While no longer registered for household use in the U.S., the insecticide Chlorpyrifos Is used widely around the world and in U.S. agriculture.Prenatal Exposure to Insecticide Chlorpyrifos Linked to
Alterations in Brain Structure and Cognition
Even low to moderate levels of exposure to the insecticide chlorpyrifos during pregnancy may lead to long-term, potentially irreversible changes in the brain structure of the child, according to a new brain imaging study by researchers from the Columbia Center for Children's Environmental Health at the Mailman School of Public Health, Duke University Medical Center, Emory University, and the New York State Psychiatric Institute. The changes in brain structure are consistent with cognitive deficits found in children exposed to this chemical. Results of the study appeared in 2012: PNAS.
The study is the first to use MRI to identify the structural evidence for these cognitive deficits in humans,confirming earlier findings in animals. Changes were visible across the surface of the brain, with abnormal enlargement of some areas and thinning in others. The disturbances in brain structure are consistent with the IQ deficits previously reported in the children with high exposure levels of chlorpyrifos, or CPF, suggesting a link between prenatal exposure to CPF and deficits in IQ and working memory at age 7.
The study also reports evidence that CPF may eliminate or reverse the male-female differences that are ordinarily present in the brain. Further study is needed to determine the consequences of these changes before and after puberty, the researchers say.
Notably, the brain abnormalities appeared to occur at exposure levels below the current EPA threshold for toxicity, which is based on exposures high enough to inhibit the action of the key neurological enzyme cholinesterase. The present findings suggest that the mechanism underlying structural changes in the brain may involve other pathways.
According to the lead author, Virginia Rauh, ScD, Professor at the Mailman School of Public Health and Deputy Director of the Columbia Center for Children's Environmental Health, "By measuring a biomarker of CPF exposure during pregnancy, and following the children prospectively from birth into middle childhood, the present study provides evidence that the prenatal period is a vulnerable time for the developing child, and that toxic exposure during this critical period can have far-reaching effects on brain development and behavioral functioning."
"By combining brain imaging and community-based research, we now have much stronger evidence linking exposure to chlorpyrifos with neurodevelopmental problems," adds senior author Bradley S. Peterson, MD, Chief of Child & Adolescent Psychiatry, New York State Psychiatric Institute, and Director of MRI Research in the Department of Psychiatry, Columbia University Medical Center.
In the current study, the researchers used MRI to evaluate the brains of 40 New York City children, ages 5 to 11, whose mothers were enrolled prenatally in a larger cohort study. Researchers compared 20 children with high exposures to CPF with 20 children with lower exposures; all exposures occurred prior to the EPA ban on household use of the chemical in 2001. They found brain anomalies were associated with the higher exposure.
Since the 2001 ban, a drop in residential exposure levels of CPF has been documented by Robin Whyatt, DrPH, a co-author on the present study and Professor of Clinical Environmental Health Sciences and Co-Deputy Director of the Columbia Center for Children's Environmental Health at the Mailman School. However, the chemical continues to be present in the environment through its widespread use in agriculture (food and feed crops), wood treatments, and public spaces such as golf courses, some parks, and highway medians. People near these sources can be exposed by inhaling the chemical, which drifts on the wind. Low-level exposure can also occur by eating fruits and vegetables that have been sprayed. Although the chemical is degraded rapidly by water and sunlight outdoors, it has been detected by the Columbia researchers in many urban residences years after the ban went into effect.
The study was supported by the National Institute of Environmental Health Sciences Grants 5P01ES09600, P50ES015905, and 5R01ES08977, as well as pilot funding through ES009089; EPA STAR Grants RD834509, RD832141, and R827027; National Institute of Mental Health Grants MH068318 and K02-74677; and the John and Wendy Neu Family Foundation.
Additional co-authors included Frederica P. Perera and Megan K. Horton, Mailman School; Ravi Bansal, Xuejun Hao, and Jun Liu, Columbia University Medical Center; Dana Boyd Barr, Emory University; and Theodore A. Slotkin, Duke University.
April 30, 2012
Study of grasshoppers' diets shows that animals are an important part of organic matter decomposition. While being hunted, prey animal diets may affect how soil releases carbon dioxide.Predators Have Outsized Influence Over Habitats
A grasshopper's change in diet to high-energy carbohydrates while being hunted by spiders may affect the way soil releases carbon dioxide into the atmosphere, according to research results published in the journal Science.
Grasshoppers like to munch on nitrogen-rich grass because it stimulates their growth and reproduction. But when spiders enter the picture, grasshoppers cope with the stress from fear of predation by shifting to carbohydrate-rich plants, setting in motion dynamic changes to the ecosystem they inhabit, scientists have found.
"Under stressful conditions they go to different parts of the 'grocery store' and choose different foods, changing the makeup of the plant community," said Oswald Schmitz, a co-author of the paper and an ecologist at Yale University. The high-energy, carbohydrate diet also tilts a grasshopper's body chemistry toward carbon at the expense of nitrogen. So when a grasshopper dies, its carcass breaks down more slowly, thus depriving the soil of high-quality fertilizer and slowing the decomposition of uneaten plants.
"This study casts a new light on the importance of predation in natural communities," said Saran Twombly, program director in the National Science Foundation's Division of Environmental Biology, which funded the research. "A clever suite of experiments shows that the dark hand of predation extends all the way from altering what prey eat to the nutrients their decomposing bodies contribute to soil."
Microbes in the soil require a lot of nitrogen to function and to produce the enzymes that break down organic matter. "It only takes a slight change in the chemical composition of that animal biomass to fundamentally alter how much carbon dioxide the microbial pool is releasing to the atmosphere while it is decomposing plant organic matter," said Schmitz. "This shows that animals could potentially have huge effects on the global carbon balance because they're changing the way microbes respire organic matter."
The researchers found that the rate at which the organic matter of leaves decomposed increased between 60 percent and 200 percent in stress-free conditions relative to stressed conditions, which they consider "huge."
"Climate and litter quality are considered the main controls on organic-matter decomposition, but we show that aboveground predators change how soil microbes break down organic matter," said Mark Bradford, a co-author of the study and also an ecologist at Yale. Schmitz added: "What it means is that we're not paying enough attention to the control that animals have over what we view as a classically important process in ecosystem functioning."
The researchers took soil from the field, put it in test tubes and ground up grasshopper carcasses obtained from environments either with or without grasshopper predators. They then sprinkled the powder atop the soil, where the microbes digested it. When the grasshopper carcasses were completely decomposed, the researchers added leaf litter and measured the rate of leaf-litter decomposition. The experiment was then replicated in the field at the Yale Myers Forest in northeastern Connecticut.
"It was a two-stage process where the grasshoppers were used to prime the soil, then we measured the consequences of that priming," said Schmitz. The effect of animals on ecosystems is disproportionately larger than their biomass would suggest.
"Traditionally people thought that animals had no important role in recycling of organic matter, because their biomass is relatively small compared to the plant material that's entering ecosystems," Schmitz said. "We need to pay more attention to the role of animals, however. In an era of biodiversity loss we're losing many top predators and larger herbivores from ecosystems."
Other co-authors are Michael Strickland of Yale, and Dror Hawlena of the Hebrew University of Jerusalem.
June 14, 2012
The Australian Antarctic Division has released a study, published in Diversity and Distribution Journal, that examines the geography, geology, climate, flora and fauna of the ice-free areas of Antarctica and has indentified biologically-distinct Antarctic Conservation Biogeographic Regions.
The lead author and Australian Antarctic Division terrestrial biologist Dr Aleks Terauds, said this is the first time there has been a continent-wide assessment of the biogeography of Antarctica using all of the available biodiversity data.
“Previously terrestrial Antarctica has been divided into 2 main areas based on aspects like geography geology or specific types of biodiversity,” Dr Terauds said.
“The new research amalgamated 38,000 terrestrial records including the diverse biology such as microbes, invertebrates and plants. It revealed a complex ecosystem which can be divided into 15 very distinct and potentially delicate biogeographic regions which are characterized by different climates, landscapes and species,” Dr Terauds said.
Introduced species are identified as one of the biggest threats to the Antarctic terrestrial ecosystems, particularly in a warming climate.
“With about 40,000 people visiting Antarctica over a summer, as tourists, scientists or station support personnel, there’s the potential more species will be accidently transferred to and within Antarctica.”
“While quarantine procedures are already in place for inter-continental travel, such as cleaning clothing and equipment before arriving in Antarctica, there are less biosecurity measures for intra-continental movement,” he said.
“The Antarctic Conservation Biogeographic Regions represent an important basis for biosecurity measures to manage the risk of species, including species native to Antarctica, being transferred from one biogeographic zone to another.”
The collaborative effort, which involved scientists from Australia, South Africa, New Zealand and the UK identified the 15 areas as:
- North-east Antarctic Peninsula
- South Orkney Islands
- North-west Antarctic Peninsula
- Enderby Land
- Dronning Maud Land
- East Antarctica
- North Victoria Land
- South Victoria Land
- Transantarctic Mountains
- Ellsworth Mountains
- Marie Byrd Land
- Adelie Land
- Ellsworth Land
- South Antarctic Peninsula.
While Antarctica already has a series of Antarctic Specially Protected Areas, delegates at the ATCM are being urged to develop a broader representation of conservation regions based on this new biogeographic assessment.
- Map of Biogeographic Regions
- Diversity and Distribution Journal paper
- Weeding out the aliens in Antarctica
13 June 2012
Exposure to chemicals during fetal development can increase the risk of health consequences, including adverse birth outcomes, childhood morbidity, and adult disease and mortality; yet, little is known about the extent of multiple chemicals exposures among pregnant women.
This article, written byTracey J. Woodruff, Ami R. Zota, and Jackie M. Schwartz*, appeared first in Environmental Health Perspectives—the peer-reviewed, open access journal of the National Institute of Environmental Health Sciences.
The article is a verbatim version of the original and is not available for edits or additions by Encyclopedia of Earth editors or authors. Companion articles on the same topic that are editable may exist within the Encyclopedia of Earth.Environmental Chemicals in Pregnant Women
in the United States: NHANES 2003–2004 Abstract
Background: Exposure to chemicals during fetal development can increase the risk of adverse health effects, and while biomonitoring studies suggest pregnant women are exposed to chemicals, little is known about the extent of multiple chemicals exposures among pregnant women in the United States.
Objective: We analyzed biomonitoring data from the National Health and Nutritional Examination Survey (NHANES) to characterize both individual and multiple chemical exposures in U.S. pregnant women.
Methods: We analyzed data for 163 chemical analytes in 12 chemical classes for subsamples of 268 pregnant women from NHANES 2003–2004, a nationally representative sample of the U.S. population. For each chemical analyte, we calculated descriptive statistics. We calculated the number of chemicals detected within the following chemical classes: polybrominated diphenyl ethers (PBDEs), perfluorinated compounds (PFCs), organochlorine pesticides, and phthalates and across multiple chemical classes. We compared chemical analyte concentrations for pregnant and nonpregnant women using least-squares geometric means, adjusting for demographic and physiological covariates.
Results: The percentage of pregnant women with detectable levels of an individual chemical ranged from 0 to 100%. Certain polychlorinated biphenyls, organochlorine pesticides, PFCs, phenols, PBDEs, phthalates, polycyclic aromatic hydrocarbons, and perchlorate were detected in 99–100% of pregnant women. The median number of detected chemicals by chemical class ranged from 4 of 12 PFCs to 9 of 13 phthalates. Across chemical classes, median number ranged from 8 of 17 chemical analytes to 50 of 71 chemical analytes. We found, generally, that levels in pregnant women were similar to or lower than levels in nonpregnant women; adjustment for covariates tended to increase levels in pregnant women compared with nonpregnant women.
Conclusions: Pregnant women in the U.S. are exposed to multiple chemicals. Further efforts are warranted to understand sources of exposure and implications for policy making.Keywords: chemicals, environmental exposures, NHANES, pregnancy.
Exposure to chemicals during fetal development can increase the risk of adverse health consequences, including adverse birth outcomes (e.g., preterm birth and birth defects), childhood morbidity (e.g., neurodevelopmental effects and childhood cancer), and adult disease and mortality (e.g., cancer and cardiovascular effects) (Gluckman and Hanson 2004; Stillerman et al. 2008). Biomonitoring studies report nearly ubiquitous exposure to many chemicals in the U.S. population—for example, bisphenol A (BPA), perchlorate, and certain phthalates and polybrominated diphenyl ethers (PBDEs) [Centers for Disease Control and Prevention (CDC) 2009a]. These studies, along with more geographically targeted studies of pregnant women, show that pregnant women are also exposed to many chemicals (Bradman et al. 2003; Swan et al. 2005). Chemicals can cross the placenta and enter the fetus, and a number of chemicals measured in maternal urine and serum have also been found in amniotic fluid, cord blood, and meconium (Barr et al. 2007). In some cases, such as for mercury, fetal exposures may be higher than maternal exposure (Barr et al. 2007).
Multiple chemical exposures are of increasing concern. Studies show that exposure to multiple chemicals that act on the same adverse outcome can have a greater effect than exposure to an individual chemical. This has been recognized by the National Academy of Sciences (NAS), which recommends that future efforts accounting for risks from multiple chemical exposures combine effects from chemicals acting on the same adverse health outcome (National Research Council 2008a). Subsequently, assessment of exposure to multiple chemicals has been identified as an important future research area (Kortenkamp 2007).
Because few data are available on levels of individual or multiple chemicals in pregnant women, levels in reproductive-age women have often been used as an indicator of chemical levels in pregnant women (Blount et al. 2000). Some studies have directly compared pregnant women in their cohort and reproductive-age women from the National Health and Nutritional Examination Survey (NHANES), a nationally representative sample of the U.S. population. For example, phthalates measured in pregnant women from three U.S. locations were lower than those measured in reproductive-age women from NHANES (Swan et al. 2005). Numerous physiological changes occur during pregnancy, including weight gain and increases in blood and plasma volume, which can affect concentrations of chemicals (Chesley 1972; Pirani and Campbell 1973). Chemicals may also concentrate in the fetus, which could influence maternal concentrations (Takahashi and Oishi 2000). Further, behavioral changes occurring during pregnancy, such as diet modification (e.g., quantity and food type), may also influence chemical body burdens in pregnant women (Mirel et al. 2009). Understanding whether some of these factors can influence maternal concentrations of chemicals helps inform our ability to use measurements of chemicals in nonpregnant women as a surrogate for pregnant women.
We analyzed biomonitoring data for pregnant women from NHANES to characterize exposure to individual and multiple chemicals and their metabolites in pregnant women. Additionally, we evaluated the extent to which levels measured in nonpregnant women are representative of levels in pregnant women, and what factors may explain observed differences.Methods
Study population. NHANES, conducted by the CDC, is a nationally representative survey and physical examination assessing the health and nutritional status of the civilian, noninstitutionalized U.S. population. The survey also includes measurement of chemicals and their metabolites in blood and urine (for more information, see CDC 2010). We use the term “chemical analyte” here to describe both chemicals and their metabolites. Because of the complex stratified survey design in NHANES, separate sample weights are assigned to each survey respondent; each participant represents approximately 50,000 other U.S. residents. Pregnant women were oversampled in the NHANES survey from 2001 to 2006 (CDC 2009b). [Protocols for oversampling pregnant women are described in Supplemental Material (doi:10.1289/ehp.1002727) and in detail elsewhere (Mirel et al. 2009).] We classified pregnancy status according to the results of the urine pregnancy test administered as part of NHANES protocols.
Most chemical analytes were measured in subsets of the total NHANES sample. Each subset included about one-third the total number of participants, so not all chemical analytes were measured in each participant. Further, not every group of chemical analytes was measured in each cycle. Therefore, we analyzed the 2003–2004 cycle, because it represents the cycle with the highest number of chemical analytes measured across the sample of pregnant women. We limited our study population to those 15–44 years of age to be consistent with the definition used by the National Center for Health Statistics for women of childbearing age (Chandra et al. 2005). Therefore, our study population includes 268 pregnant women and 1,489 nonpregnant women 15–44 years of age included in at least one subsample for chemical analyte analysis.
Environmental chemical analyte analyses. Chemical analyte analyses were conducted at the National Center for Environmental Health laboratories (CDC, Atlanta, GA). Analytical procedures and summary statistics for the general population have been described in the Fourth National Report on Human Exposure to Environmental Chemicals and in the peer-reviewed literature (Calafat et al. 2008; Caldwell et al. 2009; CDC 2009a; Sjodin et al. 2008). We assessed 163 chemical analytes across 12 chemical classes (Table 1), measured in blood, urine, and serum.Table 1. Click for Larger Image.
Chemical classes measured in biological tissue of pregnant women, NHANES 2003–2004.
Data analysis. We conducted analyses in SUDAAN (version 10.0; Research Triangle Institute, Research Triangle Park, NC) and SAS (version 9.2; SAS Institute Inc., Cary, NC). SUDAAN calculates variance estimates after incorporating the nonrandom sampling design and the sample population weights, which account for oversampling of certain subgroups.
We examined summary statistics and distributional plots for each chemical analyte. We calculated the following descriptive statistics [for further details on analysis, see Supplemental Material (doi:10.1289/ehp.1002727)]: percentage of women with levels greater than the limit of detection (LOD), geometric mean (GM), geometric standard error (GSE), median and 95th percentile estimates, and the coefficient of variation (CV; defined as the GSE divided by the GM). The GM, GSE, and CV were calculated only for chemical analytes with > 60% detection frequency. The median and 95th percentile were calculated for all chemical analytes. Concentrations below the LOD were substituted by the CDC with LOD/√–2. We present statistical results for individual chemical analytes in the main text that are representative of each chemical class [for descriptive statistics and LODs for all 163 chemical analytes, see Supplemental Material, Table 1 (doi:10.1289/ehp.1002727)]. Representative chemical analytes were chosen based on public health relevance and expectation of relatively widespread exposure.
To assess extent of multiple exposures within a chemical class, we evaluated the number of individual PBDEs, perfluorinated compounds (PFCs), organochlorine pesticides, and phthalates detected in each pregnant woman. We chose these chemical classes to represent banned persistent chemicals (organochlorine pesticides), persistent chemicals (PBDEs and PFCs), and currently used nonpersistent chemicals (phthalates).
We then evaluated the extent of multiple chemical exposures across chemical classes in three different subsamples. These three subsamples were the primary subsamples of the pregnant women. Pregnant women in subsample A were assessed for metals, cotinine, and PFCs (17 chemical analytes in 76 women); in subsample B, for metals, cotinine, organochlorine pesticides, phthalates, PBDEs, and polycyclic aromatic hydrocarbons (PAHs) (52 chemical analytes in 54 women); and in subsample C, for metals, phenols, polychlorinated biphenyls (PCBs), organophosphate insecticide metabolites, perchlorate, and cotinine (71 chemical analytes in 59 women) [for subsample composition, see Supplemental Material, Table 2 (doi:10.1289/ehp.1002727)]. Volatile organic compounds (VOCs) were measured only in a subsample of pregnant women that partially overlapped with subsamples A, B, and C. Consequently, we did not include VOCs in analyses of multiple chemical exposures.
Table 2. Click for Larger Image.
Characteristics of reproductive-age women by pregnancy status, NHANES 2003–2004.
To compare chemical analyte concentrations between pregnant and nonpregnant women, we constructed multivariate regression models, which included our main effect (binary pregnancy status variable) along with covariates. We log-transformed chemical analytes before regression analysis to account for the nonnormal distributions. From these models, we calculated the least-squares geometric means (LSGMs), which provide GM estimates after adjustment for other covariates. For every chemical analyte in the main analysis, we used the same set of covariates. Covariates were included if they were significant predictors of more than one chemical analyte or if their inclusion in the model changed the β-coefficient for the main effect by > 20%. The following covariates were evaluated: age (continuous), race/ethnicity (Mexican American, non-Hispanic white, non-Hispanic black, or other), education (high school diploma or less vs. more than high school diploma), marital status (married/living with a partner, divorced/separated, or never married), parity (number of pregnancies resulting in live births, nulliparous vs. one or more child), current body mass index (BMI; continuous), smoking status (never, former, or current), serum albumin (continuous), length of food and drink fasting before blood collection (0–4.5 hr, 4.5–8.5 hr, or 8.5–24 hr), and urinary creatinine (continuous). All regression models were adjusted for the same covariates except for creatinine (included in models for urinary chemicals only). We excluded 12 nonpregnant women who reported fasting times > 24 hr. We defined statistical significance as p < 0.10 for all analyses because of relatively small number of pregnant women sampled for each chemical analyte and, consequently, small degrees of freedom.
As a sensitivity analysis, we performed multivariate regression in women < 35 years of age, because the age distribution differed between the two groups. For this analysis, we selected model covariates separately for each individual chemical analyte using the covariate selection method described above. Thus, the covariates in the sensitivity analysis may differ from that used in the main analysis. We conducted sensitivity analyses for lead (n = 215 pregnant; n = 885 nonpregnant), BPA (n = 63 pregnant; n = 275 nonpregnant), and p,p´-dichlorodiphenyldichloroethene (DDE) (n = 65 pregnant; n = 380 nonpregnant).Results
Although most pregnant and nonpregnant women were white, there was a higher percentage of Mexican-American pregnant women compared with nonpregnant women, reflecting higher birth rates among Hispanic women in the United States (Table 2) (Martin et al. 2007). Nonpregnant women were older, less likely to be married or with a partner, and more likely to smoke than were pregnant women (Table 2). In addition, pregnant women had lower levels of albumin and shorter fasting times before blood collection than did nonpregnant women.
Table 3 summarizes statistics for pregnant and nonpregnant women for select chemical analytes [for all 163 chemical analytes in pregnant women, see Supplemental Material, Table 1 (doi:10.1289/ehp.1002727)]. We found that 0–100% of pregnant women had a detectable level across the individual chemical analytes. Eight of 12 classes of chemicals included individual chemical analytes detected in 99–100% of pregnant women (PFCs, PBDEs, PCBs, organochlorine pesticides, phenols, phthalates, PAHs, and perchlorate). Four classes (VOCs, PFCs, PCBs, and organochlorine pesticides) included at least one individual chemical analyte not detected in any pregnant women [see Supplemental Material, Table 1 (doi:10.1289/ehp.1002727)]. In general, organophosphate metabolites, VOCs, and dioxins and furans were less frequently detected in pregnant women than were the other chemical classes except for dimethylthiophosphate (DMTP), toluene, m- and p-xylene, and methyl tert-butyl ether (MTBE).
Table 3. Click for Larger Image.
Descriptive statistics for chemical analytes in pregnant and nonpregnant women, NHANES 2003–2004.a
Among pregnant women, DDE had the highest GM concentration (140.4 ng/g lipid) of the persistent, lipophilic compounds measured in serum (PCBs, PBDEs, and organochlorine pesticides), whereas concentrations of most of the other measured chemical analytes in these classes were an order of magnitude lower (PCBs, 4–8 ng/g lipid; PBDEs, 5–23 ng/g lipid). Perfluorooctane sulfonic acid (PFOS) had the highest GM among the persistent chemical analytes that do not accumulate in lipids (e.g., lead, cadmium, and PFCs). Of the nonpersistent chemical analytes measured in urine (organophosphate metabolites, phenols, phthalates, PAHs, and perchlorate), triclosan, benzophenone-3, and monoethyl phthalate (MEP) had the highest GMs (17.00, 25.49, and 226.53 μg/L, respectively).
Although the GM for cotinine was < 1 μg/L, the range of concentrations spanned three orders of magnitude (CV = 0.31). Variability in other chemical analyte levels measured in pregnant women was generally low (CV < 0.25), except for some phenols (CV = 0.25–0.51), phthalates (CV = 0.22–0.35), MTBE (CV = 0.40), triclosan (CV = 0.51), and PBDE-153 (CV = 0.31).
Figure 1 shows the numbers of individual PFC, PBDE, organochlorine pesticide, and phthalate chemical analytes detected in individual pregnant women. At least two organochlorine pesticides, one PBDE, two PFCs, and four phthalates were measured in each pregnant woman. The median number of chemicals detected for organochlorine pesticides, PBDEs, PFCs, and phthalates were 6, 6, 4, and 9, respectively. For PBDEs and phthalates, 7% and 2%, respectively, had detectable levels of ≥ 90% of the chemical analytes in the class.
Figure 1. Click for Larger Image.
Distribution of the number of chemicals detected in U.S. pregnant women for four chemical classes: organochlorine pesticides (A; n = 71), PBDEs (B; n = 75), PFCs (C; n = 76), and phthalates (D; n = 91).
The median number of chemical analytes detected among women in subsamples A, B, and C were 8 (range, 4–12), 37 (range, 28–45), and 50 (range, 35–60), respectively (Figure 2). We found generally that the overall number of chemicals detected was not dominated by detects within a particular chemical class (Figure 3). For example, several participants in subsample B at the median detected level (37 chemicals) had 10 phthalates, 10 PAHs, 7 PBDEs, 6 organochlorine pesticides, 3 metals, and cotinine detected.
Figure 2. Click for Larger Image.
Distribution of the number of chemicals detected in U.S. pregnant women across multiple chemical classes. (A) Subsample A (metals, cotinine, and PFCs). (B) Subsample B (metals, cotinine, organochlorine pesticides, phthalates, PBDEs, and PAHs). (C) Subsample C (metals, phenols, PCBs, organophosphate insecticide metabolites, perchlorate, and cotinine).Figure 3. Click for Larger Image.
Number of chemicals detected by chemical class in U.S. pregnant women, NHANES subsample B [metals, cotinine, organochlorine (OC) pesticides, phthalates, brominated flame retardants (PBDEs), and PAHs], 2003–2004 (n = 54). Each vertical bar represents one study participant. Other subsamples showed similar results.
GM and median levels for most chemicals were similar to or lower than those in pregnant than in nonpregnant women, except for PBDEs, DMTP, triclosan, and perchlorate (Table 3). About half the LSGM estimates for pregnant women (Table 4) increased after adjusting for covariates (Tables 3 and 4). For a few chemicals, the LSGM estimates for pregnant women decreased after adjustment, such as PBDEs, some phthalates, perchlorate, and BPA. In general, adjusted LSGMs were comparable between pregnant and nonpregnant women (Table 4). Nonpregnant women had significantly higher levels of cadmium, lead, PFOS, BPA, and cotinine, but pregnant women had significantly higher levels of DDE, DMTP, MTBE, and perchlorate (Table 4). The most pronounced differences between pregnant and nonpregnant women were for MTBE and DMTP (levels in pregnant women were about two times those of nonpregnant women) and cotinine (levels in pregnant women were about half those of nonpregnant women).
Comparison of chemical analyte concentrations between pregnant and nonpregnant women after adjustment for covariates,a calculated from multivariate regression models.
Serum albumin influenced the comparison between pregnant and nonpregnant women for 28 of the 32 compounds evaluated in regression analyses (the β-coefficient changed by > 20%); however, direction of the effect varied by type of compound. In general, for chemical analytes measured in blood, effect estimates for albumin were positive, and their inclusion increased the LSGMs for pregnant women; in contrast, for nonpersistent urinary chemical analytes, the albumin effect estimates were more often negative, and their inclusion decreased the LSGMs for pregnant women (data not shown). Smoking influenced comparison of LSGMs between pregnant and nonpregnant women for 75% of chemicals. Maternal age and BMI changed the LSGMs for persistent organic pollutants such as PCBs, and creatinine influenced LSGMs for most chemical analytes measured in urine. Other variables, such as race/ethnicity and education, were often significant predictors of chemical analyte concentrations but generally did not change LSGM comparisons in Table 4.
Compared with estimates based on women of all ages, LSGMs for lead and DDE for both pregnant and nonpregnant women were reduced when we restricted analyses to younger women (< 35 years of age). However, relative differences in adjusted estimates between pregnant and nonpregnant women were not substantially affected. LSGMs for BPA increased for both groups in the restricted analysis, and the differences in LSGM estimates between pregnant and nonpregnant women were no longer statistically significant [LSGM = 2.16 (pregnant) vs. 3.03 μg/L (nonpregnant), p = 0.24].Discussion
We found widespread exposure to pregnant women in the United States to multiple chemical analytes, including both banned and contemporary contaminants. Although we did not make any direct connection to potential adverse health consequences, levels of many of these chemical analytes were similar to those measured in epidemiologic studies finding an association between prenatal chemicals exposure and adverse reproductive and developmental outcomes. These include phthalates and increased risk of adverse male reproductive outcomes (Swan et al. 2005), mercury and developmental neurological outcomes (Lederman et al. 2008), PBDEs and neurodevelopmental outcomes (Herbstman et al. 2010), and PCBs and maternal thyroid hormone disruption during pregnancy (Chevrier et al. 2008).
Additionally, pregnant women were exposed to multiple chemical analytes at one time, many of which can affect the same adverse outcomes. Examples include maternal thyroid hormone disruption [e.g., perchlorate, PCBs, PBDEs, and triclosan (Crofton 2008)], male reproductive development (multiple phthalates), and the developing brain (mercury, lead, PCBs) (National Research Council 2008a). The NAS has recommended risk assessment of multiple chemicals expand to account for chemicals acting on a common adverse outcome (National Research Council 2008a). Although the NAS focused on grouping chemicals contributing to disturbances of androgen action, they also proposed this approach for chemicals affecting brain development (National Research Council 2008a).
Levels of chemicals measured during pregnancy can be influenced by physiological (e.g., changes in BMI, plasma volume expansion, and bone mobilization) and behavioral factors. For example, previous research has found an inverse relationship between weight gain during pregnancy and levels of persistent organic pollutants in pregnant women (Bradman et al. 2006). We found that plasma volume expansion, using the level of albumin as a surrogate, may also influence chemical levels measured in pregnant women. Plasma volume begins to expand in pregnant women at around 8 weeks of gestation and increases progressively until 30–34 weeks gestation, when it plateaus. This expansion may dilute environmental chemical concentrations in blood (Faupel-Badger et al. 2007). Accurately measuring plasma volume expansion is expensive and ideally requires multiple measurements throughout pregnancy (Faupel-Badger et al. 2007). However, albumin measurements may provide a reasonable surrogate because previous studies suggest that blood volume expansion dilutes circulating levels of albumin during pregnancy (Honger 1968). We found that, in general, adjusting for albumin increased GM estimates of persistent compounds, such as DDE, in pregnant women, suggesting that the concentration is diluted by increased plasma volume. However, adjustment for albumin generally decreased estimates for nonpersistent compounds, such as BPA, in pregnant women, suggesting that lower albumin may be associated with an increased clearance of environmental contaminants. Albumin may affect metabolism and transport of chemicals by mechanisms other than plasma volume expansion. For example, previous research has shown that PFCs actually bind to albumin in the blood (Jones et al. 2003). BPA also binds to plasma proteins, such as albumin, in humans (Teeguarden et al. 2005), so reduced albumin during pregnancy may influence the amount of BPA that undergoes phase II conjugation and subsequent elimination through urine. The role of albumin, and other transport proteins, in the transport and metabolism of environmental chemicals, particularly during pregnancy, is an important topic and requires further research.
We found that, generally, the levels in pregnant women were similar to or lower than levels measured in nonpregnant women. Adjusting for physiological factors that may influence levels of chemicals in pregnant women tended to increase the levels in pregnant women compared with nonpregnant women. This suggests that generally levels of chemicals in nonpregnant reproductive-age women are reasonably representative of levels found in pregnant women. However, for several chemicals, levels in pregnant women remain lower than those in nonpregnant women. Behavioral factors may explain this difference (e.g., cotinine and smoking), or other physiological factors may be important [e.g., chemical levels concentrating in the fetus such as for BPA (Takahashi and Oishi 2000)].
The NHANES study design, where groups of chemicals were analyzed in approximate one-third–sized subsamples, meant that we could not evaluate more than 71 chemical analytes in any individual pregnant women, or about 44% of chemical analytes measured during 2003–2004. This also limited our ability to assess exposures to multiple chemical analytes that may be acting on the same adverse outcome (e.g., PBDEs and PCBs, which can affect neurodevelopment, were not measured in the same women). Given that several chemical analytes within each of the classes were detected almost ubiquitously, pregnant women have more detectable chemical analytes than we could assess in any individual participant in this analysis.
Other methodological changes between cycles make it challenging to compare data across NHANES cycles. For example, the number and types of chemicals sampled changes by cycle. Another challenge is that LODs vary among the cycles. Mostly they decreased, such as with PCBs, which can increase the number of chemicals detected. However, a few LODs increased; for example, certain urinary phthalate esters, such as mono-2-ethylhexyl phthalate (MEHP) and MEP, increased between 2003–2004 and 2005–2006.
Chemical analyte concentrations in NHANES participants should be representative of typical U.S. concentrations. Thus, highly exposed subpopulations may be underrepresented. For example, women living in the agricultural Salinas Valley of California had higher measurable levels of several pesticides than did NHANES pregnant women (Castorina et al. 2010). Other subpopulations may have nonrepresentative exposure patterns, such as high fish consumption or higher use of certain personal care products.
Our analysis indicates high variability in exposures for some chemical analytes, shown by the relatively high CV for phenols, phthalates, cotinine, and MTBE. For some of these analytes, with almost an order of magnitude difference between the median and the 95th percentile, variation may reflect geographic variability in exposure sources. For example, MTBE was used in reformulated gasoline starting in 1995. Reformulated gasoline was required for use year-round in cities with significant smog problems (Energy Information Administration 2008), so it was not used in every U.S. location. Thus, the geographic variation in MTBE use may play a role in the wide exposure variability (Energy Information Administration 2008). PBDE-153 is another example of how geographic use variation can influence exposures levels. The 95th percentile of PBDE-153 levels is 15 times greater than the median, and previous research has found PBDE concentrations to be around two times higher in Californians than in others in the United States, likely because of California’s unique flammability standard (Zota et al. 2008). Variation in exposure to chemical analytes used in consumer and personal care products (e.g., triclosan, where the 95th percentile is 35 times greater than the median) could be driven by unique product uses (Allmyr et al. 2009). Although biomonitoring studies can demonstrate variation in exposures within populations, they generally are limited in their ability to identify sources of exposures. Consequently, additional exposure assessment research is needed to identify the dominant sources of exposure among pregnant women and the general population.
Our analysis of the NHANES pregnancy data shows ubiquitous exposure to multiple chemicals during a sensitive period of fetal development. The NAS recommends accounting for both multiple exposures and exposures that occur during vulnerable developmental periods in improved approaches for assessing chemical risks across the population, which includes shifting to a risk assessment approach that presumes no threshold of effect among the population unless shown otherwise (National Research Council 2008b). Data, such as from NHANES, should be used to enhance our understanding of risks among the U.S. population and to inform further policy and research activities.Supplemental Material References
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- *The Authors are: Tracey J. Woodruff, Ami R. Zota, Jackie M. Schwartz of the Program on Reproductive Health and the Environment, Department of Obstetrics, Gynecology and Reproductive Sciences, University of California, San Francisco, Oakland, California, USA
- Citation: Woodruff TJ, Zota AR, Schwartz JM 2011. Environmental Chemicals in Pregnant Women in the United States: NHANES 2003–2004. Environ Health Perspect 119:878-885. http://dx.doi.org/10.1289/ehp.1002727
- Received: 05 July 2010; Accepted: 10 January 2011; Online: 14 January 2011
- Address correspondence to T.J. Woodruff, Program on Reproductive Health and the Environment, University of California–San Francisco, 1330 Broadway St., Suite 1100, Oakland, CA 94612 USA. Telephone: (510) 986-8942. Fax: (510) 986-8960. E-mail: firstname.lastname@example.org
- Funding was provided by Pew Charitable Trusts and a grant from the Passport Science Innovation Fund, which provides research grants to increase understanding of environmental health that supports effective public health policies and clinical care.
- The authors declare they have no actual or potential competing financial interests.
Myocardial infarction, an atherosclerotic disease, has been associated with increased body burdens of persistent organic pollutants. This can be problematic in the elderly.
This article, written by P. Monica Lind, Bert van Bavel, Samira Salihovic, and Lars Lind*, appeared first in Environmental Health Perspectives—the peer-reviewed, open access journal of the National Institute of Environmental Health Sciences.
The article is a verbatim version of the original and is not available for edits or additions by Encyclopedia of Earth editors or authors. Companion articles on the same topic that are editable may exist within the Encyclopedia of Earth.Circulating Levels of Persistent Organic Pollutants (POPs)
and Carotid Atherosclerosis in the Elderly Abstract
Background and objective: Increased circulating levels of persistent organic pollutants (POPs) have been associated with myocardial infarction. Because myocardial infarction is an atherosclerotic disease, we investigated, in a cross-sectional study, whether POP levels are related to atherosclerosis.
Methods: In the population-based Prospective Investigation of the Vasculature in Uppsala Seniors (PIVUS) study (n = 1,016 participants 70 years of age), the prevalence of carotid artery plaques was determined by ultrasound. The number of carotid arteries with plaques (0, 1, or 2) was recorded. Also, the intima-media thickness (IMT) and gray scale median of the intima-media complex (IM-GSM) were measured. Twenty-three POPs, comprising 16 polychlorinated biphenyls (PCBs), 5 pesticides, 1 dioxin, and 1 brominated compound (brominated diphenyl ether congener BDE-47), were analyzed by high-resolution chromatography coupled to high-resolution mass spectrometry.
Results: Seven of the POPs (PCB congeners 153, 156, 157, 170, 180, 206, and 209) were significantly associated with the number of carotid arteries with plaques even after adjusting for multiple risk factors (sex, waist circumference, body mass index, fasting blood glucose, systolic and diastolic blood pressure, high-density lipoprotein and low-density lipoprotein cholesterol, serum triglycerides, smoking, antihypertensive treatment, and statin use; p = 0.002–0.0001). Highly chlorinated PCBs (congeners 194, 206, and 209) were associated with an echolucent IM-GSM (p < 0.0001 after adjustment), whereas associations between POPs and IMT were modest.
Conclusions: Circulating levels of PCBs were associated with atherosclerotic plaques and echogenicity of the intima-media complex independent of cardiovascular risk factors, including lipids. This suggests that POPs may be a risk factor for myocardial infarction, but associations need to be confirmed in prospective studies.Keywords: atherosclerosis, atherosclerotic plaques, persistent organic pollutants (POPs), pesticides.
Persistent organic pollutants (POPs) are chemical substances that persist in the environment, bioaccumulate through the food web, and pose a risk of causing adverse effects to human health and the environment. There is evidence of long-range transport of these substances to regions where they have never been used or produced, resulting in exposure of most human populations to POPs through consumption of fat-containing food such as fish, dairy products, and meat (Letcher et al. 2010).
During recent years, elevated circulating levels of POPs have been associated with a number of cardiovascular (CV) risk factors, such as hypertension, obesity, and diabetes, as well as with metabolic syndrome (Everett et al. 2008; Ha et al. 2009; Lee et al. 2007, 2011b; Rönn et al. 2011; Uemura et al. 2009). Furthermore, circulating levels of POPs have been associated with a history of myocardial infarction (Flesch-Janys et al. 1995; Sergeev and Carpenter 2005).
A characteristic feature of myocardial infarction is atherosclerosis. Because coronary and carotid artery atherosclerosis often go hand in hand (Hulthe et al. 1997), we hypothesized that participants with high levels of circulating POPs would have a higher incidence of carotid atherosclerotic plaques. Furthermore, because we recently found that the echogenicity of the intima-media complex in the carotid artery, a possible marker of lipid infiltration in the vascular wall, is a predictor of future CV death (Wohlin et al. 2009), we also investigated whether POP levels are associated with the gray scale median of the carotid artery intima-media complex (IM-GSM). To test these hypotheses, we used the population-based Prospective Investigation of the Vasculature in Uppsala Seniors (PIVUS) study (Lind et al. 2005), from which we have data on atherosclerosis and circulating POP levels for almost 1,000 participants.
Specifically, we tested associations between POP levels and the prevalence of overt carotid plaques, and intima-media thickness (IMT; an early marker of atherosclerosis development measurable in participants without overt plaque). In addition, we tested associations with carotid artery IM-GSM, a marker of lipid infiltration in the vascular wall that might be altered even before a plaque could be measured.Materials and Methods
Participants. Eligible participants were all 70 years of age and lived in the community of Uppsala, Sweden. The participants were randomly chosen from the register of persons living in the community. A total of 1,016 persons participated, giving a participation rate of 50.1%. The study was approved by the Ethics Committee of the University of Uppsala, and all the participants gave their informed consent before the study.
All participants were evaluated in the morning after an overnight fast. No medication or smoking was allowed after midnight. The participants were asked to answer a questionnaire about their medical history, smoking habits, and current use of regular medication.
We measured the blood pressure in the noncannulated arm of each participant using a calibrated mercury sphygmomanometer. Blood pressure was measured to the nearest 1 mmHg after at least 30 min of rest, and the average of three recordings was used. Lipid variables and fasting blood glucose were measured by standard laboratory techniques.
Ultrasound evaluation of the carotid artery. The carotid artery was assessed by external B-mode ultrasound imaging (Acuson XP128 with a 10 MHz linear transducer; Acuson Corp, Mountain View, CA, USA). We visually inspected the common carotid artery, the bulb, and the internal carotid artery at both sides for the presence of plaque. A plaque was judged to be present in a particular carotid artery if a local thickening of the IMT was seen that was > 50% thicker than the surrounding IMT in any part of the carotid artery investigated. We recorded the presence of carotid plaques in none, one, or both of the carotid arteries (Figure 1).
Figure 1. Click for Larger Image.
An ultrasonographic image of the left carotid artery from a study participant. The blood inside the artery appears black. The right side of the image shows the part of the common carotid artery where IMT and IM-GSM are measured (rectangle). IMT is the thickness of that part of the vascular wall, and IM-GSM is a measure of the echogenicity (gray scale) of the same part of the wall. At the left side of the image, the carotid artery has divided into an internal part and an external part. In the bifurcation region, two plaques are outlined.
The images were digitized and imported into the automated Artery Measurement Software, version 1.0 (Liang et al. 2000) for dedicated analysis of IMT and the IM-GSM. For IMT analysis, a maximal 10-mm segment with good image quality was chosen from the common carotid artery close to the bifurcation point. A region of interest was placed manually around the intima-media complex, which was evaluated for IMT. The program calculated the echogenicity in the intima-media complex by analyzing individual pixels within the region of interest on a scale from 0 (black) to 256 (white). Thus, a low IM-GSM value indicated a lipid-rich wall, while a high value represented a vascular wall rich in collagen or calcium. Like IMT, the gray scale median value given is the mean value from right and left carotid arteries. We repeated the IMT measurements in 30 random participants, giving a coefficient of variation for carotid artery IMT of 7.2% and for IM-GSM of 7.5%.
Method for analyses of POPs. POPs were measured in stored serum samples collected at baseline. We used a sample cleanup and extraction method based on a method by Sandau et al. (2003), with some modifications. Briefly, 1 mL formic acid was added to 0.5 mL plasma sample and sonicated. Labeled 13C internal standards and 1 mL 3% isopropanol in water were added after 60 min, followed by another sonication. Solid-phase extraction (SPE) was performed by loading the sample on a conditioned Oasis® HLB SPE (Waters, Milford, MA, USA) cartridge (6 cm3/150 mg). The cartridge was rinsed with 6 mL 3% isopropanol in water and 6 mL 40% methanol in water. After drying under nitrogen, the target compounds were eluted with 6 mL methylene chloride:hexane (1:1). Further cleanup was performed using a small, activated multilayer silica gel column (2 mL, 1.5 g) eluted with 7.5 mL hexane. After evaporation and addition of the 13C-labeled recovery standard, the volume was reduced to 25 μL tetradecane. The final measurements were performed on a Micromass Autospec Ultima (Waters) high-resolution gas chromatograph/high-resolution mass spectrometer. We monitored the two most abundant ions of the chlorine or bromine cluster in addition to one ion for the 13C-labeled internal and recovery standards by injecting 2 μL on a 6890N gas chromatograph (Agilent Technologies, Atlanta, GA, USA) containing a 30 m × 0.25 i.d. × 0.25 μm DB-5 capillary column (SGE Analytical Science, Victoria, AUS).
Quality assurance/quality control. Quality control plasma samples and procedural blank samples were incorporated in each batch of 10 samples. Blank samples did not contain any target compounds at levels > 5% of the levels in the samples except for cis-chlordane and trans-chlordane. The recoveries of the internal standards were satisfactory, in general ranging from 60–110%. The relative standard deviation of the 100 quality assurance/quality control (QA/QC) samples was < 25% for all compounds except for the compounds that were present at low levels and just above the limit of detection (LOD) in the QA/QC sample. The laboratory routinely takes part in international laboratory comparison studies, with good results (z-scores < 2).Table 1. Click for Larger Image.
Selected basic characteristics and major CV risk factors in the PIVUS study (n = 1,016; 50.2% females).Table 2. Click for Larger Image.
Serum concentrations (pg/mL) of POPs in the PIVUS study (n = 1,016; 50.2% females).
A total toxic equivalency (TEQ) value was calculated for the polychlorinated biphenyls (PCBs) as well as octachlorodibenzo-p-dioxin (OCDD) according to Van den Berg et al. (1998). TEQ was also calculated separately for the dioxin-like non-ortho-PCBs (congeners 126 and 169) and the dioxin-like mono-ortho-PCBs.
Statistical analysis. POPs were measured in 992 participants; data were missing for some participants because of a lack of plasma samples. IMT and IM-GSM were evaluated in 990 participants, while plaque prevalence was evaluated in only 943 participants because of bad image quality for some participants. Data for individual model covariates used to adjust for potential confounding were missing for < 10 participants.
We evaluated all variables for nonnormality. Variables with a skewed distribution, including fasting glucose, serum triglycerides, all POPs, the sum of the PCBs, and TEQ, were natural log (ln) transformed. In addition, the POPs were divided into quintiles to evaluate potential nonlinear relationships.
Ordinal logistic regression models were used when the outcome was number of carotid arteries with plaques (grouped as 0, 1, or 2; the dependent variable). Linear regression was used when the outcomes were the continuous variables IMT or IM-GSM (the dependent variable). Linear and logistic regression modeling was done according to Dobson (2002).
We evaluated all interactions between the POP levels and sex for all POPs and for all outcomes by introducing an interaction term between the POP under investigation and sex together with the POP and sex terms. Because no such interactions (p < 0.05) were found, sex adjustment was performed in the first set of models.
In the second sets of models, we adjusted for multiple CV risk factors [sex, waist circumference, body mass index (BMI), ln-transformed fasting blood glucose, systolic blood pressure (SBP), diastolic blood pressure (DBP), high-density lipoprotein (HDL) and low-density lipoprotein (LDL) cholesterol, ln-transformed serum triglycerides, current smoking, antihypertensive treatment, and statin use].
In all the above models, analyses were first run with the POPs modeled as ln-transformed continuous variables and categorized using quintiles. Because of the large number of POPs analyzed, we applied a Bonferroni correction to determine the alpha level for statistical significance (0.05/21 = 0.00238) for each of the three outcomes: plaque occurrence, IMT, and IM-GSM. The software used was STATA (version 11; StataCorp, College Station, TX, USA).Results
Approximately 7% of the cohort reported a history of myocardial infarction, 4% stroke, and 9% diabetes mellitus. Almost half the cohort (45%) reported use of CV medication, with antihypertensive medication being the most common (32%). Fifteen percent of the participants reported use of statins. Two percent of the sample were on insulin therapy, and 6% were on regular oral antiglycemic drugs (Table 1; for details, see Lind et al. 2005).
A total of 23 POPs were measured: 16 PCB congeners, 5 organochlorine (OC) pesticides, 1 OCDD, and 1 brominated diphenyl ether (BDE) congener. We evaluated POPs that we found at detectable levels in > 90% of the study population. Because the statistical analysis is limited by a large number of cases with undetectable levels, two OC pesticides (trans-chlordane and cis-chlordane) with detection rates < 10% were excluded from the final analyses (Table 2).
POPs versus carotid plaques. Models of ln-transformed POP levels as continuous variables identified 7 POPs (PCB congeners 153, 156, 157, 170, 180, 206, and 209) that were significantly associated (p < 0.00238) with the number of carotid arteries with plaques, even after adjusting for sex or sex and multiple CV risk factors (Table 3).
Table 3. Click for Larger Image.
Relationships among POPs, plaques in the carotid artery, and echogenicity IM-GSM in the common carotid artery (ln-transformed continuous variables).
No significant interactions were seen between POP levels and sex regarding carotid plaque except for hexachlorobenzene (HCB). For HCB, however, no statistically significant relationships with carotid atherosclerosis were seen after adjusting for multiple testing [after adjusting for multiple risk factors; men: odds ratio (OR) = 0.92; 95% confidence interval (CI): 0.60, 1.41; women: OR = 1.5; 95% CI: 1.01, 2.24]. For the other POPs, we adjusted, rather than stratified, the sample for sex.
When we divided the POP levels into quintiles, we found monotonic relationships versus the number of arteries with plaques for the POPs described above (data not shown).
A significant relationship was found between the ln-transformed sum of the PCBs and the number of arteries with plaques after adjusting for multiple risk factors (OR = 1.03; 95% CI: 1.01, 1.05; p = 0.002). When we summed subsets of PCBs according to the number of chlorine atoms, PCBs with fewer than six chlorine atoms were not related to carotid plaques, whereas those with six or more chlorine atoms were significantly associated with plaque prevalence (Table 3).
Total TEQ (ln-transformed) was not significantly associated with the number of arteries with plaques. Nonetheless, TEQ for the dioxin-like mono-ortho-PCBs, but not for the dioxin-like non-ortho-PCBs, was significantly related to plaque prevalence (Table 3).
POPs versus IMT. No single POP was related to IMT after adjusting for multiple risk factors and multiple testing (Table 3). No evidence was seen of any low-dose effect, as defined by a marked change in the median for IMT already taking place at the second quartile (data not shown).
The sum of the PCBs was not significantly associated with IMT after adjusting for multiple risk factors. The sum of PCBs with fewer than 8 chlorine atoms also was not associated with IMT, but the sum of PCBs with 8–10 chlorine atoms was significantly related to IMT (p = 0.009; Table 3). Total TEQ was associated with IMT after adjusting for multiple risk factors (p = 0.009; Table 3). The TEQ for the dioxin-like non-ortho-PCBs, but not for the dioxin-like mono-ortho-PCBs, was also significantly associated with IMT.
POPs versus IM-GSM. IM-GSM was inversely associated with ln-transformed PCB-126 and the highly chlorinated PCBs (congeners 194, 206, and 209) after adjusting for multiple risk factors (p < 0.0001; Table 3) and positively associated with HCB and trans-nonachlordane (TNC; p < 0.0001). The inverse relationship between 1,1-bis-(4-chlorophenyl)-2,2-dichloroethene (DDE) levels and IM-GSM approached significance after adjusting for multiple risk factors and multiple testing (p = 0.003).
No significant interactions were seen between the POP levels and sex regarding IM-GSM. Consequently, we adjusted, rather than stratified, the sample for sex. When the POP levels were divided into quintiles, monotonic relationships were seen between IM-GSM and PCBs congeners 206 and 209 (data not shown).
An inverse significant relationship was found between the sum of the PCBs and IM-GSM after adjusting for multiple risk factors (p = 0.002; Table 3). When the sum of PCBs was divided according to the number of chlorine atoms, PCBs with fewer than 8 chlorine atoms were not associated with IM-GSM; however, PCBs with 8–10 chlorine atoms had a significant inverse association with IM-GSM (p = 0.0001). Total TEQ was inversely related to IM-GSM after adjusting for multiple risk factors (p = 0.0001). However, only TEQ for the dioxin-like non-ortho-PCBs, not for the dioxin-like mono-ortho-PCBs, was significantly related to IM-GSM.
Stratification by CV medication. To investigate whether the observed associations reported above were similar in participants with CV medication and those without, we performed the analysis again in participants with CV medication (45% of the sample) and participants without CV medication separately. In general, estimated associations according to medication use were comparable for all three outcomes with those estimated for the population as a whole. One exception was the association between OCDD and IM-GSM, which was evident only in participants not using CV medication (OR = 1.51; 95% CI: 1.41, 2.01; vs. participants using CV medication: OR = 1.00; 95% CI: 0.74, 1.37).Discussion
In the present cross-sectional study, several of the individual PCBs, as well as the sum of the PCBs, were associated with the presence of carotid artery plaques. Some of the highly chlorinated PCBs were also associated with the echogenicity of the intima-media complex, a marker of vascular wall composition. Total TEQ was positively associated with IMT and inversely associated with the echogenicity of the intima-media complex but not associated with plaque prevalence. These relationships were statistically significant after adjusting for CV risk factors, including lipids, suggesting that POPs may have a vascular effect not mediated by traditional risk factors for atherosclerosis. To the best of our knowledge, no other study has reported associations between POP levels and measures of atherosclerosis in a large human sample.
Comparison with the literature. Associations between POP exposure and myocardial infarction based on studies of highly exposed individuals (through accident or occupational exposure) and studies of representative population-based samples have been reported (Chase et al. 1982; Dalton et al. 2001; Sergeev and Carpenter 2010). However, because POP exposure has also been associated with well-known CV risk factors such as hypertension, diabetes, hyperlipidemia, and obesity (Everett et al. 2008; Goncharov et al. 2008; Lee et al. 2007, 2011a, 2011b; Rönn et al. 2011), it is unclear whether POPs might induce myocardial infarction by altering risk factors or by a more direct action on the vascular wall.
Biological rationale. Development of atherosclerosis is a complicated chain of events starting with accumulation of LDL cholesterol in the subintimal space. After oxidation of LDL, immunocompetent cells such as monocytes and T-cell lymphocytes are attracted to the site of lipid oxidation by activation of adhesion molecules from the endothelium, and the chronic repair-of-injury process begins with the liberation of proinflammatory cytokines.
POPs may interfere with this process in several ways. For example, POPs have been associated with an increased blood pressure, with proatherogenic alterations in lipid metabolism, and with the development of diabetes and obesity (Everett et al. 2008; Ha et al. 2009; Lee et al. 2007, 2011b; Rönn et al. 2011; Uemura et al. 2009). However, associations between several of the POPs and markers of atherosclerosis were evident despite adjustment for classical CV risk factors, which suggests that associations, if causal, might reflect direct effects of POPs on atherosclerosis. Moreover, POPs have been found to impair endothelium-dependent vasodilatation in mice (Kopf et al. 2008) and alter the expression of genes involved in DNA repair and cell cycling in vascular smooth muscle cells (Puga et al. 2004). Several POPs activate the cytosolic aryl hydrocarbon receptor (AHR). For example, activation of the AHR by dioxin induces an oxidative stress response (Kopf et al. 2008; Park et al. 1996; Shertzer et al. 1998), which might contribute to atherosclerosis via the oxidation of LDL, an early event in the formation of atherosclerotic plaques. Activation of the AHR also triggers up-regulation of genes such as cytochrome P450 1A1 (CYP1A1) and cyclooxygenase-2 (COX2), whose products metabolize arachidonic acid into vasoactive eicosanoids known to be involved in the atherosclerotic process (Dalton et al. 2001; Kraemer et al. 1996; Puga et al. 1997, 2004). Cross talk between the AHR and sex-hormone receptors is a well-known occurrence (Ohtake et al. 2008), and it is also well known that estrogen and testosterone are important players in atherosclerosis (Bourghardt et al. 2010; Kolovou et al. 2011). We have recently reported an association between circulating levels of the estrogen-receptor ligand bisphenol A and atherosclerosis in the present study population (Lind and Lind 2011).
Other mechanisms may exist whereby POPs could influence several of the major stages in the atherosclerotic process. The association between TEQ and atherosclerosis in the present study, together with a previous experimental finding that tetrachlorodibenzo-p-dioxin increases the formation of plaques in apolipoprotein E knockout mice, a well-known model of atherosclerosis formation (Dalton et al. 2001), supports the involvement of the AHR in atherosclerosis formation.
Different measurements of atherosclerosis. In the present study, we evaluated three markers that reflect different characteristics of the atherosclerotic process: plaque prevalence, IMT, and IM-GSM. All three measures are related to future CV events (Davidsson et al. 2010; O’Leary et al. 1999; Wohlin et al. 2009), but IMT and IM-GSM are measured in the plaque-free part of the vascular wall and consequently represent processes that occur before overt plaques form. However, IMT and IM-GSM are poorly correlated with each other (R2 < 0.01), and although the major risk factors for IMT in the present cohort were SBP and smoking, the major risk factors for IM-GSM were lipids and markers of inflammation and oxidative stress (Andersson et al. 2009). This suggests that the two measures, IMT and IM-GSM, may reflect different aspects of atherosclerosis development that may be affected in different ways by POPs. Furthermore, although IMT and overt plaque formation were both associated with blood pressure and smoking in the study population, markers of oxidative stress and inflammation were more closely associated with plaque than with IMT (Andersson et al. 2009). This may explain why POPs could be more closely related with plaque prevalence than with IMT, i.e., because activation of the AHR could induce oxidative stress and inflammation (Park et al. 1996; Shertzer et al. 1998).
Carotid artery plaque. The presence of atherosclerotic plaques in the carotid arteries is a known predictor of future CV events (O’Leary et al. 1999). Atherosclerosis in the carotid arteries is also predictive of plaques in the coronary circulation (Hulthe et al. 1997). Consequently, persons with carotid artery plaques are at increased risk for myocardial infarction. Furthermore, because persons with bilateral carotid plaques are at higher risk of future CV disorders compared with those with unilateral plaques (Davidsson et al. 2010), we used a graded response for carotid plaques (0, 1, or 2 carotid arteries with plaques) rather than a binary outcome (plaque or no plaque) for our study participants.
Echogenicity of the intima-media complex. The echogenicity of the intima-media complex is closely related to the echogenicity of overt plaques (Lind et al. 2007) and has been shown to be a powerful predictor of future CV mortality (Wohlin et al. 2009). The echogenicity of overt plaques is related to the composition of the plaque (El-Barghouty et al. 1996), and it is therefore likely that the echogenicity of the intima-media complex is also a marker for the composition of the vascular wall.
In the present study, the highly chlorinated PCBs were associated with an echolucent intima-media complex, a likely marker for a lipid-rich vascular wall, even after adjusting for CV risk factors, including lipids. By contrast, HCB and TNC were associated with an echogenic intima-media complex, suggesting that these pesticides might affect vascular walls with compositions opposite to those affected by highly chlorinated POPs. In contrast to the findings for plaques, total TEQ was associated with IM-GSM, supporting an AHR-mediated effect of the PCBs on this outcome.
Intima-media thickness. IMT is a known predictor of CV events and is usually regarded as a marker of atherosclerosis (O’Leary et al. 1999). Atherosclerosis is a disorder of the intima, but IMT also incorporates the media in the measurement and thus might distort the relationship with POP levels.
Nonlinear relationships. In most cases, models of POPs categorized by quintiles supported linear relationships with atherosclerosis. It has been argued that nonmonotonic, low-dose effects could be a characteristic feature of many POPs (Gregoraszczuk et al. 2008; Haase et al. 2009; Kim et al. 2010; Lee et al. 2007), but the present study produced very little evidence to support this.
Adjustment for lipids. Traditionally, POP levels are normalized for lipids and given per gram lipid because these compounds are lipid soluble (Bernert et al. 2007). However, this normalization may not be appropriate when dealing with CV diseases because POP exposure has been shown to alter lipid levels in both human and animal studies (Bell et al. 1994; Goncharov et al. 2008; Kanagawa et al. 2008; Kratz 2005; Lind et al. 2004). We therefore chose to use wet-weight levels for the POPs but adjusted for lipids (together with the multiple risk factors) in the second model. It has also been argued that lipid normalization tends to overadjust for the effects of lipids and that adjusting the statistical models is more appropriate (Gaskins and Schisterman 2009). This lipid adjustment, however, only marginally changed the results in the present study. Furthermore, essentially the same results as presented above were obtained when we used lipid-normalized POP levels in the analysis (data not shown).
Limitations of the study. The cross-sectional study population was limited to Caucasians 70 years of age, which means that caution should be taken about generalizing to other ethnic and age groups.
The present study had a moderate participation rate. However, an analysis of nonparticipants showed the present sample to be fairly representative of the total population regarding most CV disorders and drug intake (Lind et al. 2005).Conclusions
Circulating levels of PCBs were associated with atherosclerotic plaques and the echogenicity of the intima-media complex independent of CV risk factors, including lipids. This suggests an effect of POPs on the risk of myocardial infarction that should be investigated in prospective studies.References
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*The Authors and their affiliations are: P. Monica Lind1, Bert van Bavel2, Samira Salihovic2, Lars Lind3
1 Occupational and Environmental Medicine, Uppsala University, Uppsala, Sweden,
2 Man-Technology-Environment (MTM) Research Centre, Örebro University, Örebro, Sweden, and
3 Department of Medicine, Uppsala University, Uppsala, Sweden.
- Citation: Lind PM, van Bavel B, Salihovic S, Lind L 2012. Circulating Levels of Persistent Organic Pollutants (POPs) and Carotid Atherosclerosis in the Elderly. Environ Health Perspect 120:38-43. http://dx.doi.org/10.1289/ehp.1103563
- Received: 11 February 2011; Accepted: 03 October 2011; Online: 11 October 2011
Address correspondence to M. Lind, Occupational and Environmental Medicine, Department of Medicine, Uppsala University, 751 85 Uppsala, Sweden. Telephone: 46 186119745. Fax: 46 18519978.
- This study was supported by the Swedish Research Council and the Swedish Research Council for Environment, Agricultural Sciences, and Spatial Planning.
- The authors declare they have no actual or potential competing financial interests.
Two decades after Rio Earth Summit, scientists recommend international efforts to halt biodiversity losses. Such loss is compromising nature's ability to provide goods and services essential for human well-being, the scientists say.Ecologists Call for Preservation of
Planet's Remaining Biological Diversity
Twenty years after the Earth Summit in Rio de Janeiro, 17 ecologists are calling for renewed international efforts to curb the loss of Earth's biological diversity. The loss is compromising nature's ability to provide goods and services essential for human well-being, the scientists say.
Over the past two decades, strong scientific evidence has emerged showing that decline of the world's biological diversity reduces the productivity and sustainability of ecosystems, according to an international team led by the University of Michigan's Bradley Cardinale. It also decreases ecosystems' ability to provide society with goods and services like food, wood, fodder, fertile soils and protection from pests and disease.
"Water purity, food production and air quality are easy to take for granted, but all are largely provided by communities of organisms," said George Gilchrist, program director in the National Science Foundation's Division of Environmental Biology, which funded the research. "This paper demonstrates that it is not simply the quantity of living things, but their species, genetic and trait biodiversity, that influences the delivery of many essential 'ecosystem services.'''
Human actions are dismantling ecosystems, resulting in species extinctions at rates several orders of magnitude faster than observed in the fossil record. If the nations of the world make biodiversity an international priority, the scientists say, there's still time to conserve much of the remaining variety of life--and possibly to restore much of what's been lost. The researchers present their findings in the journal Nature. The paper is a scientific consensus statement that summarizes evidence from more than 1,000 ecological studies over the last two decades.
"Much as consensus statements by doctors led to public warnings that tobacco use is harmful to your health, this is a consensus statement that loss of Earth's wild species will be harmful to the world's ecosystems and may harm society by reducing ecosystem services that are essential to human health and prosperity," said Cardinale. "We need to take biodiversity loss far more seriously--from individuals to international governing bodies--and take greater action to prevent further losses of species."
An estimated nine million species of plants, animals, protists and fungi inhabit the Earth, sharing it with some seven billion people. The call to action comes as international leaders prepare to gather in Rio de Janeiro on June 20-22 for the United Nations Conference on Sustainable Development, known as the Rio+20 Conference. The upcoming conference marks the 20th anniversary of the 1992 Earth Summit in Rio, which resulted in 193 nations supporting the Convention on Biological Diversity's goals of biodiversity conservation and the sustainable use of natural resources. The 1992 Earth Summit caused an explosion of interest in understanding how biodiversity loss might affect the dynamics and functioning of ecosystems, as well as the supply of goods and services of value to society.
In the Nature paper, the scientists review published studies on the topic and list six consensus statements, four emerging trends, and four "balance of evidence" statements. The balance of evidence shows, for example, that genetic diversity increases the yield of commercial crops, enhances the production of wood in tree plantations, improves the production of fodder in grasslands, and increases the stability of yields in fisheries.
Increased plant diversity results in greater resistance to invasion by exotic plants, inhibits plant pathogens such as fungal and viral infections, increases above-ground carbon sequestration through enhanced biomass, and increases nutrient remineralization and soil organic matter.
"No one can agree on what exactly will happen when an ecosystem loses a species, but most of us agree that it's not going to be good," said Shahid Naeem of Columbia University, a co-author of the paper. "And we agree that if ecosystems lose most of their species, it will be a disaster." "Twenty years and a thousand studies later, what the world thought was true in Rio in 1992 has finally been proven: biodiversity underpins our ability to achieve sustainable development," Naeem said. Despite far-reaching support for the Convention on Biological Diversity, biodiversity loss has continued over the last two decades, often at increasing rates.
In response, a new set of diversity-preservation goals for 2020, known as the Aichi targets, was recently formulated. And a new international body called the Intergovernmental Platform on Biodiversity and Ecosystem Services was formed in April 2012 to guide a global response toward sustainable management of the world's biodiversity and ecosystems. Significant gaps in the science behind biological diversity remain and must be addressed if the Aichi targets are to be met, the scientists write in their paper.
"This paper is important both because of what it shows we know, and what it shows we don't know," said David Hooper of Western Washington University, one of the co-authors. "Several of the key questions we outline help point the way for the next generation of research on how changing biodiversity affects human well-being."
Without an understanding of the fundamental ecological processes that link biodiversity, ecosystem functions and services, attempts to forecast the societal consequences of diversity loss, and to meet policy objectives, are likely to fail, the ecologists write. "But with that fundamental understanding in hand, we may yet bring the modern era of biodiversity loss to a safe end for humanity," they conclude.
In addition to Cardinale, Naeem and Hooper, co-authors of the Nature paper are: J. Emmett Duffy of The College of William and Mary; Andrew Gonzalez of McGill University; Charles Perrings and Ann P. Kinzig of Arizona State University; Patrick Venail and Anita Narwani of the University of Michigan; Georgina M. Mace of Imperial College London; David Tilman of the University of Minnesota; David A. Wardle of the Swedish University of Agricultural Sciences; Gretchen C. Daily of Stanford University; Michel Loreau of the National Centre for Scientific Research in Moulis, France; James B. Grace of the U.S. Geological Survey; Anne Larigauderie of the National Museum of Natural History in Rue Cuvier, France; and Diane Srivastava of the University of British Columbia.
June 6, 2012
The United Nations Environment Programme notes that the world remains on an unsustainable track despite hundreds of internationally agreed goals and objectives. An ambitious set of sustainability targets can be met, but only with renewed commitment and rapid scaling-up of successful policies.Global Environmental Outlook: Fifth Edition
The world continues to speed down an unsustainable path despite over 500 internationally agreed goals and objectives to support the sustainable management of the environment and improve human wellbeing, according to a new and wide-ranging assessment coordinated by the United Nations Environment Programme (UNEP).
The fifth edition of the Global Environmental Outlook (GEO-5), launched on the eve of the Rio+20 Summit, assessed 90 of the most-important environmental goals and objectives and found that significant progress had only been made in four.
These are eliminating the production and use of substances that deplete the ozone layer, removal of lead from fuel, increasing access to improved water supplies and boosting research to reduce pollution of the marine environment - for a full list of goals and status of implementation, visit: www.unep.org/geo/pdfs/geo5/Progress_towards_goals.pdf .
Some progress was shown in 40 goals, including the expansion of protected areas such as National Parks and efforts to reduce deforestation.
Little or no progress was detected for 24 – including climate change, fish stocks, and desertification and drought.
Further deterioration was posted for eight goals including the state of the world‘s coral reefs while no assessment was made of 14 other goals due to a lack of data.
The report cautions that if humanity does not urgently change its ways, several critical thresholds may be exceeded, beyond which abrupt and generally irreversible changes to the life-support functions of the planet could occur.
"If current trends continue, if current patterns of production and consumption of natural resources prevail and cannot be reversed and 'decoupled', then governments will preside over unprecedented levels of damage and degradation,‖ said UN Under-Secretary General and UNEP Executive Director Achim Steiner.
But it‘s not all bad news. The report says meeting an ambitious set of sustainability targets by the middle of the century is possible if current policies and strategies are changed and strengthened, and gives many examples of successful policy initiatives, including public investment, green accounting, sustainable trade, the establishment of new markets, technological innovation and capacity building.
GEO-5 also points out that where international treaties and agreements have tackled goals with specific, measurable targets—such as the bans on ozone-depleting substances and lead in petrol—they have demonstrated considerable success. For this reason, GEO-5 calls for more specific targets, with quantifiable results, across a broader range of environmental challenges.
"GEO-5 reminds world leaders and nations meeting at Rio+20 why a decisive and defining transition towards a low-carbon, resource-efficient, job-generating Green Economy is urgently needed," said Mr. Steiner. "The scientific evidence, built over decades, is overwhelming and leaves little room for doubt."
"The moment has come to put away the paralysis of indecision, acknowledge the facts and face up to the common humanity that unites all peoples," he added. "Rio+20 is a moment to turn sustainable development from aspiration and patchy implementation into a genuine path to progress and prosperity for this and the next generations to come."
The report also calls for a greater focus on policies that target the drivers of environmental change – such as population growth and urbanization, unsustainable consumption patterns, fossil fuel-based energy consumption and transport, and globalization.
In particular, globalization has made it possible for trends in drivers to generate intense pressures in concentrated parts of the world very quickly, as in the case of increased demand for biofuels leading to land clearance and conversion.
Although reducing the drivers of environmental change directly may appear politically difficult, it is possible to accomplish significant indirect benefits by targeting more expedient objectives, such as international goals on human well-being, the report says.
Advance Indoor Microbial Sampling
Humans spend greater than 90 percent of their time indoors, but we're never alone there. Bacteria and viruses, scientists estimate, make up half of the world's biomass—some 10 nonillion (1 followed by 31 zeros) microorganisms—and we most often meet them within enclosed spaces. So, that's where the modern microbe hunter often looks first. A report issued by the National Institute of Standards and Technology (NIST) offers guidance to make the hunting more effective.
A fundamental understanding of the microbial community in the built environment—including estimates of diversity, function and concentration—is necessary to accurately assess human exposure, and in turn, the potential impacts on human health. To address the many challenges associated with characterizing this invisible biosphere, develop innovative approaches to make both aerosol and surface sampling more effective, and prioritize research efforts to optimize and standardize those methods, NIST, Yale University and the Alfred P. Sloan Foundation held the "Challenges in Microbial Sampling in the Indoor Environment Workshop" on February 14-15, 2011, at NIST headquarters in Gaithersburg, Md. The report summarizes the results of that workshop.
Traditionally, taking a "census" of the microflora in an indoor environment has been done by taking samples from both the air and various surfaces, growing them in nutrient media, identifying the different species that arose, and then extrapolating an estimated total quantity for each species based on the numbers present in the culture. This approach provides a view of the microbial population that is limited, unreliable and biased toward those few species that grow successfully in culture.
In recent years, culture-based detection, identification and quantification is being replaced by culture-independent characterization of an entire microbial community by studying the different genomic DNA sequences present. Attendees at the indoor sampling workshop were charged with optimizing this modern genomic approach to microbial analysis by:
- Detailing the current sample collection and processing procedures available to characterize the indoor microbiome;
- Determining the future requirements for monitoring and characterizing microbe communities;
- Defining the challenges and limitations with current methods;
- Prioritizing issues that should be addressed to meet future requirements; and
- Mapping the pathways and approaches that should be taken to develop and improve techniques to meet those needs.
The workshop summary report documents the results of these discussions, highlighting the current state of science, challenges and future priorities for surface and aerosol microbial analysis; exploring cross-cutting issues such as surface/aerosol microbiome relationships, education, training and public awareness; and providing a comprehensive overview of existing resources, including those for building and architectural considerations, sampling strategies, and worker safety and health guidelines.
NIST Technical Note (TN) 1737, Challenges in Microbial Sampling in the Indoor Environment—Workshop Summary Report, is available online at:
May 29, 2012
NIST Contact: Michael E. Newman, 301-975-3025
Carbon dioxide atmospheric concentrations at Barrow, Alaska, reached 400 parts per million this spring—the first time a monthly average measurement for the greenhouse gas attained the 400 ppm mark in a remote location.NOAA: Carbon dioxide levels
reach milestone at Arctic sites
NOAA cooperative measurements in remote, northern sites hit greenhouse gas milestone in April
The concentration of carbon dioxide in the atmosphere of Barrow, Alaska, reached 400 parts per million (ppm) this spring, according to NOAA measurements, the first time a monthly average measurement for the greenhouse gas attained the 400 ppm mark in a remote location.
Carbon dioxide (CO2), emitted by fossil fuel combustion and other human activities, is the most significant greenhouse gas contributing to climate change.
“The northern sites in our monitoring network tell us what is coming soon to the globe as a whole,” said Pieter Tans, an atmospheric scientist with NOAA’s Earth System Research Laboratory (ESRL) in Boulder, Colo. “We will likely see global average CO2 concentrations reach 400 ppm about 2016.”
Carbon dioxide at six other remote northern sites in NOAA’s international cooperative air sampling network also reached 400 ppm at least once this spring: at a second site in Alaska and others in Canada, Iceland, Finland, Norway, and an island in the North Pacific.
Measurements at all those remote sites reflect background levels of CO2, influenced by long-term human emissions around the world, but not directly by emissions from a nearby population center. At other more locally influenced sites in NOAA’s network, such as Cape May, N.J., upwind cities influence CO2 concentrations, which have exceeded 400 ppm in spring for several years.
“Turning up the levels of greenhouse gases in our atmosphere is like turning up the dial on an electric blanket,” said Jim Butler, director of the ESRL Global Monitoring Division. “You know it will keep getting warmer, but you don’t know how quickly the temperature will rise, and it can take awhile for the blanket – or the atmosphere – to heat up.”
Average global levels of CO2 were 390.4 ppm in 2011, according to NOAA measurements, and will likely reach 400 ppm about 2016. Before the Industrial Revolution of the 1880s, global average CO2 was about 280 ppm.
Scientists with ESRL’s Global Monitoring Division keep track of CO2 and other greenhouse gases in the atmosphere in two ways. First, the group coordinates an international cooperative flask sampling network in which scientists and volunteers at more than 60 sites around the world collect air samples weekly, shipping them back to Colorado for detailed laboratory analysis. Secondly, the group maintains six baseline observatories around the world, where staff collect flasks for analysis and also measure CO2 continuously, along with many other aspects of the atmosphere and solar radiation.
In Barrow, Alaska, the only remote northern site with continual CO2 monitoring, the average monthly value of CO2 reached 400.00 ppm for the first time in April. Flask measurements made at Barrow and other remote northern sites from the North Pacific to Norway also showed CO2 levels periodically reaching 400 this spring.
The remote, high latitude northern sites reached 400 ppm first in April and May, the peak of the natural CO2 cycle. Plant growth cycles remove the gas from the air during late spring and summer and add it back during fall, winter and early spring. This annual cycle is largest at Northern high latitudes. During June through August, CO2 will fall again, and next April and May it is expected be to 402 ppm or higher at the same northern sites.
Every year since 1959, when David Keeling of the Scripps Institution of Oceanography made the first accurate measurements of CO2 in the atmosphere, the concentration of the greenhouse gas has increased. In the early 1960s, it rose about 0.7 ppm per year. For the last decade, it has been rising at about 2 ppm per year. That observed increase, independent of the seasonal ups and downs described above, is due to the accelerating pace of emissions from human activities, particularly the burning of fossil fuels.
This spring’s numbers are technically “preliminary,” and will not be finalized until next year, but rarely change more than 0.2 ppm, Tans said.
Carbon dioxide is not the only greenhouse gas. NOAA calculates the Annual Greenhouse Gas Index every year, which takes into account the heating effects of other gases that are emitted from human activities (e.g., methane, nitrous oxide, and chemicals called chlorofluorocarbons). When those gases are also considered, the global atmosphere reached a CO2 equivalent concentration of 400 ppm in 1985; and 450 ppm in 2003. Atmospheric CO2 levels are currently higher than they have been at any time during the last 800,000 years.
Watch a NOAA Earth System Research Laboratory animation of carbon dioxide levels for the past 800,000 years on:
YouTube at http://www.youtube.com/watch?v=SXHDwdd7Tf8.
May 31, 2012
Contact: Katy Human, 303-497-4747
It is known that chemical components from packaging can migrate into foods, but questions of how much migration occurs and what the potential health effects may be are gaining more attention from researchers and regulators. Food packaging is a complicated issue.
This article, written by Luz Claudio, Ph.D.*, appeared first in Environmental Health Perspectives—the peer-reviewed, open access journal of the National Institute of Environmental Health Sciences.
The article is a verbatim version of the original and is not available for edits or additions by Encyclopedia of Earth editors or authors. Companion articles on the same topic that are editable may exist within the Encyclopedia of Earth.Our Food: Packaging & Public Health
Your daily routine has many close encounters with food packaging: For breakfast, cereal from a paperboard box and a can of energy drink. For lunch, canned tuna and a plastic bottle of water. Afternoon snack, a foil-lined plastic bag of potato chips and a shrink-wrapped tray of fruit. By the time you dish up your supper of baked chicken and frozen broccoli, you’ve reaped the benefits of—and discarded—numerous different food-packaging materials. “Packaged food is very convenient. It is nice to have good food that you can grab and go,” says Claudia DeMegret, director of education at the City Parks Foundation in New York. “You try to be conscientious—buy fresh food and recycle. But you also have to wonder about how all this packaging affects the food we feed our kids and . . . how much of it ends up in landfills.”
Food packaging does much more than simply hold a product. It keeps food safe and fresh, tells us how to safely store and prepare it, displays barcodes that facilitate purchasing, provides nutritional information, and protects products during transport, delivery, and storage. On the other hand, packaging also fills trash containers and landfills, lasting far longer than the products it was made to contain. It consumes natural resources. And it can also transfer chemicals into our food, with unknown health effects. Our relationship with packaging—you could say it’s complicated.A History of Benefits
For millennia, humans stored their food in containers they found in nature—dried gourds, shells, hollow logs, leaves—as well as baskets and pottery. By the first century BC, the Chinese were wrapping foods with treated tree bark and other forerunners of paper. Centuries later, Napoleon Bonaparte used some of the first mass-produced canned food to feed his troops in the Franco-Austrian War of 1809. Plastics were discovered in the decades following that innovation but were not used beyond military purposes until well into the twentieth century.1,2
The art and science of food packaging have evolved a long way from those origins. Today, products often are wrapped in multiple layers of packaging to get them safely from the point of manufacture to consumers’ cupboards and refrigerators. Food packaging can improve food safety by alleviating bacterial contamination. It has been proposed that increased use of packaging for fresh produce could prevent contamination with Salmonella spp., a leading cause of foodborne diseases.3
“We appreciate foodservice packaging because of the convenience it affords for our busy lifestyles, but often we forget about the main benefit: sanitation,” says Lynn Dyer, president of the Foodservice Packaging Institute, an industry association. “That’s why single-use products were invented over 100 years ago—to help stop the spread of contagious diseases.”
In addition to preventing bacterial contamination, food packaging also extends the shelf life of products, which allows for broader distribution and reduced food waste. Food waste is a significant problem in the United States. The Environ-mental Protection Agency (EPA) estimates that 34 million tons of food was thrown away in 2010, representing close to 14% of the municipal solid waste generated in the United States.4 (Ironically, using more packaging to reduce food waste creates another waste problem: In 2010 household packaging constituted almost one-third of the municipal solid waste generated.5)
In the United States, all food-contact substances (FCSs)—defined as substances “intended for use as a component of materi-als used in manufacturing, packing, packaging, transporting, or holding food if such use is not intended to have any technical effect in such food”6—are regulated by the Food and Drug Administration (FDA). Different packaging materials offer different advantages. Glass preserves taste well and is chemically inert. Paper and paperboard are economic to produce and easy to print on. They are also lightweight, which reduces the fuel used for the transport of goods.7 Steel and aluminum offer the advantages of malleability, impermeability, and ease of recycling. Aluminum can also be bound to paper or plastic films for more versatility in the types of packaging that can be produced. And plastics have revolutionized the packaging industry because they are highly moldable into infinite shapes, lightweight, inexpensive, easy to seal, and durable.Potential Chemical Exposures from Packaging
It is well known that chemical components from packaging can migrate into foods, but questions of how much migration occurs and what the potential health effects may be are gaining more attention from researchers and regulators.8 However, few studies to date have looked at adverse human health effects of these exposures.
Different types of packaging materials pose different potential chemical exposures. Glass, for instance, is generally recognized as safe by the FDA when used as a container for holding food. But some glass bottles and jars may contain lead. Researchers at the Institute of Environmental Geochemistry of the University of Heidelberg in Germany assessed 125 brands of drinking water from 28 countries and showed that waters packaged in glass bottles contained 26–57 times more lead than comparable waters bottled in polyethylene terephthalate (PET) plastic. The increased lead content appeared to be a result of leaching from glass containers, although at < 1–761 ng/L, even the highest lead levels detected were well below maximum allowances for drinking water (10 µg/L in the European Union and Can-ada, and 15 µg/L in the United States).9
Other studies have found chemical contamination of food coming not from glass itself but from materials used to seal the metal lids on glass jars. In work by a Danish group, some foods in glass jars sealed with polyvinyl chloride (PVC) gaskets were found to contain di(2-ethylhexyl)phthalate (DEHP) and other phthalates at levels deemed unacceptable by the European Food Safety Authority.10,11 These studies did not assess potential health effects from this exposure, but in other studies phthalates have been associated with endocrine disruption in humans.12,13,14
Environmental health concerns associ-ated with the use of paper food packaging have focused on the use of recycled paper products. Printing inks from earlier incarnations of the paper can be trapped in this material, potentially exposing consumers to phthalates as well as to other suspected endocrine disruptors, including benzophenones and mineral oils.8 A study conducted by a German group showed that infant foods packed in recycled paperboard boxes with coated paper liners were contaminated with diisobutyl phthalate and di-n-butyl phthalate, with a few samples containing the former at levels exceeding European Commission limits for food contaminants.15 The authors noted that inner liners made of aluminum-coated foil were much more effective than coated paper at blocking the migration of phthalates from recycled paperboard packaging.
There also have been problems with the liners themselves in some paper boxes. In 2010 Kellogg Company recalled 28 million boxes of cereal because of elevated levels of methylnaphthalene16 that leached from the coated paper lining the boxes.17 Although the potential consequences of ingestion of this compound are not well understood, at least five consumers reportedly became ill after eating the contaminated cereal.18
Perhaps the hottest current debate regarding food packaging is the use of epoxy-based resins containing bisphenol A (BPA) in metal can liners (BPA is also used in hard, clear polycarbonate plastic).19 In 2008 the Nat-ional Toxicology Program released a review of the evidence on the toxicity of BPA expressing “some concern” that the compound may adversely affect the brain and prostate gland in fetuses, infants, and children at exposure levels documented in the general U.S. population.20 The Natural Resources Defense Council has petitioned the FDA to ban the use of BPA in food packaging, but on 30 March 2012 the FDA issued an interim ruling denying that request, pending further research.21 Currently the FDA allows the use of BPA in food-contact applications.
In one Texas-based study of BPA in packaged foods, researchers assessed 105 samples of fresh, plastic-wrapped, and canned foods, and found detectable levels of the chemical in 60% of them (including some of the fresh foods).22 The researchers calculated BPA intake for adults and children eating regular servings of some of the foods sampled. Their estimates fell between the reference doses established by the European Commission Scientific Committee on Food Safety (10 µg/kg/day) and the U.S. EPA (50 µg/kg/day). Despite the relatively low estimated doses from eating any one food, these authors and others8,23 point out there are multiple sources of intake of BPA, and evidence increasingly suggests that BPA and other endocrine disruptors—like the hormones they mimic—may cause unexpected effects even at tiny doses, although the extent to which these effects may occur in humans is still under investigation.24
Any food packaging that is not recycled or properly disposed of is likely to end up as litter. Since 1986 volunteers with the Ocean Conservancy’s annual one-day International Coastal Cleanups have picked up tens of millions of food-packaging items from beaches around the world.29 Other debris makes its way into oceans, perhaps most notoriously ending up as part of the Great Pacific Garbage Patch and other accumulations of trash formed by converging ocean currents. A study released 9 May 2012 estimates plastic contamination in the Great Pacific Garbage Patch has increased by two orders of magnitude since 1972.30
Although these patches can contain large chunks of debris, they consist primarily of microscopic weathered particles of plastic and other materials, forming a sort of “trash soup” that is difficult to quantify and clean up.29 Charles J. Moore, founder of the Algalita Marine Research Foundation and one of the first people to document waste contamination of the North Pacific Central Gyre,31 says this soup likely finds its way up the food chain as it mixes with the plankton consumed by fish. It is unclear whether ingesting microplastic particles causes any adverse health effects anywhere in the food chain, although there is evidence these particles may bind relatively large amounts of persistent organic pollutants found in seawater, then release them into marine organisms, with unknown effects.32
© John Lund/Getty Images
Some chemicals of concern, such as phthalates, have been phased out of use in food packaging. For instance, the American Plastics Council has stated that “phthalates are not used in plastic beverage bottles, nor are they used in plastic food wrap, food containers, or any other type of plastic food packaging sold in the United States.”25 Steve Russell, vice president of the Plastics Division of the American Chemistry Council, says that in the United States very little PVC is used in food contact except for meat and cling wrap, and in that application, phthalates have been replaced with alternative plasticizers such as di-(2-ethylhexyl) adipate. Adipates have been shown to potentially leach into foods, and their effects are being studied in laboratory animals, but effects on humans—if any—are not known.26,27
Although food packaging is important for sanitation and convenience, studies such as these point to the need for a better understanding of the scope and impact of chemical contamination of food via packaging. In a 2007 review of packaging contaminants in European food, Koni Grob and colleagues of the Official Food Control Authority of Canton of Zürich, Switzerland, estimated that migration of contaminants from food packaging may greatly exceed that of other contaminants, such as pesticides and environmental pollutants. “In terms of amounts,” the authors wrote, “migration from packaging material is the most important source: it exceeds most others by a factor of 100–1000.”28
Although the authors noted these amounts “measure the degree of contamination and are not indicative of risks,” they further point out, “Legal limits for migration from packaging materials are high: the global migration limit sanctions a contamination which is unparalleled, and restrictions for specific components . . . probably [do] not correspond to the expectations of the consumers.”28
It is difficult to estimate the risk of chronic ingestion of contaminants from food packaging, as so little is known. It is even more difficult, at this point, to estimate any public-health impact that might result from that ingestion or to weigh the potential negative impacts against the known benefits related to reduced spoilage and microbial contamination.
Click for Larger Image.
What Is Being Done to Address Environmental Impacts?
Efforts to address the environmental impacts of packaging include those that aim for source reduction, reuse, and recycling.
Reduce: Source reduction can be achieved by “lightweighting,” or using less material to make the same packaging. Glass containers have decreased in weight by nearly 50% in 10 years, and between the 1970s and 2000s, two-liter PET soft-drink bottles got 25% lighter, aluminum cans got 26% lighter, and steel cans and plastic grocery sacks each lightened up by 40%.33,34 Another form of lightweighting is the use of pouches made of a thin film of plastic combined with other materials. The Swedish packaging developer Ecolean produces a one-liter pouch that weighs only 16 grams, nearly half as much as a one-liter polyethylene terephthalate (PET) bottle.35
Reuse: Reusable and refillable containers are another way in which companies can implement source reduction. Although refillable milk bottles are no longer common in the United States, they are still used in some areas of Britain where milk production is local. In Germany, about half the soft drinks and mineral water and most of the beer is sold in refillable bottles.36
Recycle: Recovery for recycling is encouraged by beverage container laws, also known as “bottle bills,” in which a cash deposit of 5–10¢ is added to the product and reimbursed when the empty container is redeemed. Currently only 10 U.S. states have such laws in place—California, Connecticut, Hawaii, Iowa, Maine, Massachusetts, Michigan, New York, Oregon, and Vermont (unclaimed deposits, which can amount to millions of dollars per year, revert to the state and/or bottlers and distributors).37 According to the nonprofit Container Recycling Institute, states that do not have bottle bills have a beverage-container recycling rate of about 24%, whereas states with bottle bills recycle about 60% of their containers.38
Glass can be recycled endlessly with little loss of quality or purity of the material. The demand for glass for recycling exceeds supply, with only 33% of discarded glass bottles and jars actually recovered for recycling in 2010. Paper food packaging is one of the least recycled materials, with 25% of discarded cartons, boxes, and bags recovered for recycling the same year. Steel cans were the most highly recycled metal food packaging material at 67% recovery, followed by aluminum cans at 50% recovery. Just under 30% of PET and high-density polyethylene (HDPE) containers were recovered.5
Although most food-packaging plastics can, in theory, be melted to make new products, some are easier and cheaper to collect and process than others, and the demand for recycled plastics differs by material, according to Steve Russell, vice president of the Plastics Division of the American Chemistry Council. Metallized plastics and laminates such as those used in juice pouches are difficult to recycle because of the mixtures of materials used. However, TerraCycle, a Trenton, New Jersey–based recycling company, collects these and other types of hard-to-recycle waste and “upcycles” them—that is, uses them to create new and innovative household and personal items.39
Recycled material may not be of the same quality or purity as the original raw material, or additional steps may be necessary to achieve the quality or purity needed for the next use of the material. For instance, plastics containing additives to help them degrade may be unsuitable as food-contact substances in their next life if any of the degradable additives remain after recycling, says Russell. The FDA therefore must preapprove any recycled materials intended to be used in contact with food.40
There’s much more to recycling than reducing the waste stream, however. “The main concern with large volumes of packaging waste is not that we are filling up landfills, it is that we are squandering materials,” says Mathy Stanislaus, assistant administrator for the EPA Office of Solid Waste and Emergency Response. For instance, in 2006 about 331 million barrels of petroleum and natural gas were used to make plastic materials in the United States, representing 4.6% of total U.S. petroleum consumption that year.41 “When we fail to find better ways to reduce, reuse, or recycle [packaging] materials, then we must use new materials,” Stanislaus says, “and that has significant negative impacts on human health and the environment.”
© Ryan McVay/Getty Images
But the need for more research is clear. “While pesticides are thoroughly evaluated and well controlled in their use, only a small fraction of the substances migrating from food packaging have been evaluated—less than fifteen hundred—and the majority have not even been identified,” Grob says. “If fifty to a hundred thousand sub-stances migrate [from packaging into foods] at levels sometimes exceeding the threshold of toxicological concern, and if one out of a hundred substances harms our health, this is likely to cause serious damage.”
EHP Editor’s note: Innovations in packaging materials and processes are being developed that use alternative materials to address the migration of potentially toxic chemicals into foods. Others address the volume of food-packaging trash by incorporating biodegradable components. EHP will explore food-packaging innovations in an upcoming issue.References
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11. Pederson GA, et al. 2008. Food Addit Contam Part A Chem Anal Control Expo Risk Assess. Migration of epoxidized soybean oil (ESBO) and phthalates from twist closures into food and enforcement of the overall migration limit. pp. 503–510. http://dx.doi.org/ 10.1080/02652030701519088
12. Duty SM, et al. The relationship between environmental exposures to phthalates and DNA damage in human sperm using the neutral comet assay. Environ Health Perspect 111(9):1164–1169. 2003. http://dx.doi.org/10.1289/ehp.5756
13. Swan SH, et al. Decrease in anogenital distance among male infants with prenatal phthalate exposure. Environ Health Perspect 113(8):1056–1061. 2005. http://dx.doi.org/10.1289/ehp.8100
14. Latini G, et al. Di-2-ethylhexyl phthalate and endocrine disruption: a review. Curr Drug Targets: Immune Endocr Metabol Disord 4(1):37–40. 2004. http://dx.doi.org/10.2174/1568008043340017
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17. Harrington R. Kellogg Issues Massive Recall as Tainted Packaging Sparks Health Fears. FoodProductionDaily.com (28 Jun 2010). Available: http://www.foodproductiondaily.com/Quality-Safety/Kellogg-issues-massive-recall-as-tainted-packaging-sparks-health-fears [accessed 7 May 2012].
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20. NTP. NTP-CERHR Monograph on the Potential Human Reproductive and Developmental Effects of Bisphenol-A. Research Triangle Park, NC:Center for the Evaluation of Risks to Human Reproduction, National Toxicology Program, U.S. Department of Health and Human Services (Sep 2008). Available: http://ntp.niehs.nih.gov/ntp/ohat/bisphenol/bisphenol.pdf [accessed 7 May 2012].
21. FDA. Bisphenol A (BPA): Use in Food Contact Application [website]. Silver Spring, MD:U.S. Food and Drug Administration (updated 30 Mar 2012). Available: http://www.fda.gov/NewsEvents/PublicHealthFocus/ucm064437.htm [accessed 7 May 2012].
22. Schecter A, et al. Bisphenol A (BPA) in U.S. food. Environ Sci Technol 44(24):9425–9430. 2010. http://dx.doi.org/10.1021/es102785d
23. Muncke J.. Exposure to endocrine disrupting compounds via the food chain: is packaging a relevant source? Sci Total Environ 407(16):4549–4559. 2009. http://dx.doi.org/10.1016/j.scitotenv.2009.05.006
24. Ahearn A. Low-dose exposure to endocrine disruptors, with Laura Vandenberg [podcast]. Environ Health Perspect; http://dx.doi.org/10.1289/ehp.trp060112 [online 1 Jun 2012].
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26. ter Veld MGR, et al. Estrogenicity of food-associated estrogenic compounds in the fetuses of female transgenic mice upon oral and IP maternal exposure. Reprod Toxicol 27(2):133–139. 2009. http://dx.doi.org/10.1016/j.reprotox.2009.01.010
27. Jarfelt K, et al. Antiandrogenic effects in male rats perinatally exposed to a mixture of di(2-ethylhexyl) phthalate and di(2-ethylhexyl) adipate. Reprod Toxicol. 19(4):pp. 505–515. http://dx.doi.org/10.1016/j.reprotox.2004.11.005
28. Grob K, et al. Food contamination with organic materials in perspective: packaging materials as the largest and least controlled source? A view focusing on the European situation. Crit Rev Food Sci Nutr 46(7):529–536. 2006. http://dx.doi.org/10.1080/10408390500295490
29. Ocean Conservancy. Tracking Trash: 25 Years of Action for the Ocean. Washington, DC:Ocean Conservancy (2011). Available: http://act.oceanconservancy.org/pdf/Marine_Debris_2011_Report_OC.pdf [accessed 7 May 2012].
30. Goldstein MC, et al. Increased oceanic microplastic debris enhances oviposition in an endemic pelagic insect. Biol Lett; http://dx.doi.org/10.1098/rsbl.2012.0298 [online 7 May 2012].
31. Moore CJ, et al. A comparison of plastic and plankton in the North Pacific Central Gyre. Mar Pollut Bull 42(12):1297–1300. 2001. http://dx.doi.org/10.1016/S0025-326X(01)00114-X
32. Gorycka M. Environmental Risks of Microplastics. Amsterdam, the Netherlands:Vrije Universiteit (6 Jul 2009). Available: http://www.cleanup-sa.co.za/Images/Environmental_Risks_Microplastics.pdf [accessed 7 May 2012].
33. Marsh K, Bugusu B.. Food packaging—roles, materials, and environmental issues. J Food Sci 72(3):R39–R55. 2007. http://dx.doi.org/10.1111/j.1750-3841.2007.00301.x
34. EPIC. The Invisible “R” Reduction. Mississauga, Canada:Environment and Plastics Industry Council. Available: http://www.plastics.ca/_files/file.php?fileid=itemThReciXyTj&filename=file_files_Invisiblr_R.pdf [accessed 7 May 2012].
35. Ecolean. Environmental Comparison, Ecolean Air [website]. Helsingborg, Sweden:Ecolean AB (2012). Available: http://www.ecolean.com/en/environment/environmental-comparison-ecolean-air/ [accessed 7 May 2012].
36. INCPEN. Reuseable Packaging [fact sheet]. Reading, UK:Industry Council for Packaging and the Environment (2010). Available: http://www.incpen.org/displayarticle.asp?a=5&c=2 [accessed 7 May 2012].
37. Bottle Bill Resource Guide [website]. Culver City, CA:Container Recycling Institute (2011). Available: http://www.bottlebill.org/ [accessed 7 May 2012].
38. Bottle Bills [website]. Culver City, CA:Container Recycling Institute (2003–2013). Available: http://www.container-recycling.org/issues/bottlebills.htm [accessed 7 May 2012].
39. Products Index [website]. Trenton, NJ:TerraCycle, Inc. (2012). Available: http://www.terracycle.net/en-US/products/page/1.html [accessed 7 May 2012].
40. FDA. Submissions on Post-Consumer Recycled (PCR) Plastics for Food-Contact Articles [website]. Silver Spring, MD:U.S. Food and Drug Administration (updated 2 Mar 2012). Available: http://www.accessdata.fda.gov/scripts/fcn/fcnNavigation.cfm?rpt=recyListing&displayAll=true [accessed 7 May 2012].
41. EIA. Frequently Asked Questions: How Much Oil Is Used to Make Plastic? [website]. Washington, DC:Energy Information Administration, U.S. Department of Energy (updated 27 May 2011). Available: http://188.8.131.52/tools/faqs/faq.cfm?id=34&t=6 [accessed 7 May 2012].Editor's Notes
- *Luz Claudio, PhD, is a tenured associate professor of preventive medicine at Mount Sinai School of Medicine, where she is director of International Health.
- Citation: Claudio L 2012. Our Food: Packaging & Public Health. Environ Health Perspect 120:a232-a237. http://dx.doi.org/10.1289/ehp.120-a232
- Online: 01 June 2012
The Gila River is a watercourse lying generally within Arizona and New Mexico in the USA, with a small portion of the tributary [catchment] situated in the Mexican state of Sonora. The Gila Basin consists chiefly of an arid landscape comprised to a considerable extent by elements of the Sonoran Desert. The mouth of the Gila River is characterized by discharge to the Colorado River.
Until around sixty million years ago, the Gila Basin was a vast swamp, with a torpid meandering flow. Gradual uplift of the Rocky Mountain block raised [headwaters] to their present elevation of about 3000 meters. Native American use of the basin includes considerable prehistoric deforestation, coupled with circa 1700-1850 AD Apache grassland burning; however, the most recent 150 years marks a notable afforestation, particularly in the upper elevations of the watershed.Hydrology
The entire [catchment] of the Gila River encompasses an area of approximately 150,740 square kilometers. The river rises in Sierra County in western New Mexico on the western slopes of the Continental Divide in the mountains known as the Black Range.
The principal tributaries of the Gila River are: San Simon River, San Pedro River, Santa Cruz River, San Francisco River, Salt River, Agua Fria River and the Hassayampa River.Human interference in ecosystems
Although humans have existed in the basin for the entire Holocene, their earliest role in ecosystem modification was likely during the first millenium AD, when timber harvesting by Mogollon, Hohokam and even Anasazi peoples. Thus there is evidence that an earlier forest rich cover became more grassland dominant at least as early as about 700 AD. However, disturbance of the natural fire regime coupled with overgrazing has led to a reversal of events in the last 150 years. Thus presently, there is a marked increase in afforestation, both a high altitudes with pines, oaks and fir, and at lower elevations with mesquite growth. In fact, this recent trend in afforestation is likely the greatest percentage positive change in forest cover anywhere in North America over the modern period.Water quality
Sedimentation has been a prominent issue in historic times, likely due to the loss of grass cover which systematically occurred over the period 500 to 1850 AD, due to ancient deforestation by Native Americans and later grassland burning by Apache peoples followed by overgrazing caused by European settlers. The basin is inherently vulnerable to sedimentation due to the erosive soil cover over most of the catchment. In parts of the Gila River system there are elevated levels of certain heavy metals, especially lead and selenium. Nitrate levels are generally not of concern, because of the low human and grazing animal population densities and low intensity agricultural use within the basin; however, there are localized issues of elevated nitrate in irrigation return waters from agricultural uses. Fluoride levels in parts of the river system are elevated creating a circumstance of low health risk, but a precursor of teeth discoloration.Aquatic biota
Native fishes in the Gila River system include the threatened [demersal] spikedace (Meda fulgida); this species is endemic to the upper Gila River Basin generally at elevations of 1800 to 2000 meters. This taxon is slender in form with a pointed snout and total body length of about eight centimeters. Coloration is olive-grey to brown above, with silvery sides that frequently exhibit blue flashes, accompanied with black speckling on the back and upper side. Breeding males manifest a bright, brassy yellow head and fins. Preferred spikedace habitat consists of moderately flowing streams with sand or gravel bottom; the species is threatened by stream channelization and adverse water qualtiy impacts.
The razorback sucker (Xyrauchen texanus) is an endangered species of fish with limited distribution in the Western USA, including upper reaches of the Gila Basin. Key extant metapopulations of this taxon are found in the Gila River, Green River (Utah), Yampa River and Lake Mohave in Arizona.
The sonora tiger salamander (Ambystoma tigrinum stebbinsi) is an endangered amphibian found in the Gila River Basin. The range of this near-endemic is delimited by Sonora north to the Canelo Hills and lying between the crests of the Huachuca and Patagonia Mountains. This salamander is resilient to wide swings in thermal stress, and thus not threatened by any trends in temperature change. Much of the breeding habitat of this taxon consists of man-made cattle ponds, and a prime driver of extinction is the presence of the barred tiger salamander (A.mavortium mavortium), which can interbreed with and genetically pollute A. tigrinum stebbinsi, which has much smaller numbers. The two salamanders are so close in appearance that genetic testing is required for exact speciation.
Another amphibian occurring in the Gila Basin is the threatened Chiricahua leopard frog (Lithobates chiricahuensis), which is found only at higher elevations (e.g. above 1000 meters) in reservoirs, small pools and cattle ponds. Threats to the species include poorly managed cattle operations, over-use of pesticides and herbicides, runoff from copper mining and presence of a pathogenic chytridiomycete fungus.Terrestrial ecoregions
Several terrestrial ecoregions encompass the Gila drainage basin:
The Arizona mountains forests ecoregion is an exception to the aridity of the majority of lower elevation parts of the Gila watershed. The transition zone of this ecoregion comprises a strong Mexican fasciation, includes several dominant pine species including Chihuahua pine (Pinus leiophylla) and Apache pine (P. engelmannii) and unique varieties of ponderosa pine (P. ponderosa var. arizonica).The zone above 2000 meters (m) includes mostly Rocky Mountain species of mixed-conifer communities such as Douglas-fir (Pseudotsuga menzeisii), Engelmann spruce (Picea engelmanni), subalpine fir (Abies lasiocarpa), and white fir (corkbark variety, A. lasiocarpa var. arizonica). Dwarf juniper (Juniperus communis) is an understory shrubby closely associated with spruce/fir forests. Exposed sites include southwestern white pine (P. strobiformis, a variety of limber pine), while disturbed north-facing sites consists primarily of lodgepole pine (P. contorta) or Quaking aspen (Populus tremuloides).
Virgin forests in this region often exceed 25 meters in height and are commonly layered in two or more age classes. Below 2900 m one or more of the age classes may be composed solely of Quaking aspen, an important wildlife habitat component and pioneer species following fire. Wetter sites contain Rocky Mountain maple (Acer glabrum), Bebb willow (Salix bebbiana), scouler willow (S. scouleriana), blueberry elder (Sambucus glauca), thin-leafed alder (Alnus tenuifolis), or bitter cherry (Prunus emarginata). Dry windy sites may be occupied by limber pine (P. flexis) and Bristelcone pine (P. aristata). At lower elevations (less than 2600 m) Douglas-fir intermingles with ponderosa pine and white fir (A. concolor).
The Sonoran Desert comprises much of the desert floor and bajada lower elevations of the Gila Basin. The Sonoran Desert is bounded in the east and southeast in a transition to the temperate coniferous forests of the Arizona Mountains and Sierra Madre Occidental pine-oak forests at higher elevations. Finally, to the south the Sonoran-Sinaloan transition subtropical dry forest is the ecotone from the Sonoran Desert to the Sinaloan dry forests of Sinaloa.
In the Chihuahuan Desert, due to its recent origin, the few warm-blooded vertebrates are restricted to the Chihuahuan Desert scrub. However, the Chihuahuan desert supports a large number of wide-ranging mammals, such as the pronghorn antelope (Antilocapra americana), mule deer (Odocoileus hemionus), grey fox (Unocyon cineroargentinus), jaguar (Panthera onca), collared peccary or javelina (Pecari tajacu), desert cottontail (Sylvilagus auduboni), black tailed jackrabbit (Lepus californicus), kangaroo rat (Dipodomys sp.), pocket mouse (Perognathus spp.), woodrat (Neotoma spp.) and deer mice (Peromyscus spp.). With only 24 individuals recorded in the state of Chihuahua Antilocapra americana is one of the most endangered species that resides in this desert. The ecoregion also contains a small wild population of the highly endangered American bison (Bison bison) and scattered populations of the highly endangered Mexican prairie dog (Cynomys mexicanus), as well as the common prairie dog (Cynomys ludovicianus).
The Sierra Madre Oriental pine-oak forests contains a very diverse and unique community of endemic and specialized species of plants, animals, reptiles and amphibians. These high mountains run north to south, beginning in the United States and ending in Mexico. The variation accumulated in this distance, between its ends and elevation ranges, increases the diversity of habitats and species present.Prehistory
Early Native Americans were present in the Gila Basin prior to the Holocene as hunter gatherers, although archaeological recovery of these earliest eras is scant.
Much of the early prehistory of the Gila Basin is associated with the Hohokam culture, whose pioneer period consists of small village settlements along the middle reaches of the Gila River; this era is generally considered to span the period 1 to 750 AD. These early settlements had a sedentary agriculture component, and extensive irrigation was conducted using diversions of the Gila River to grow maize, squash, beans and cotton.
There is no doubt that the Hohokam were influenced by their more advanced neighbors to the northeast, the Anasazi. Examination of their architectural styles and earlier peaking of Anasazi culture, especially at Chaco Canyon, indicates such a relationship.
Hohokam culture featured three discrete types of ceramics: plain ware, red ware and decorated varieties. MIneral content can be used to trace the locus of origin, with the chief distinctive ingredients being mica, quartz, quartzite, phyllite (also known as Squaw Peak schist), along with granite and arkosic sands. Thus, the subcultural region of Hohokam can be deduced from the distinctive mineral mix (e.g. Wingfield pottery associated with the Aqua Fria sub-basin; Salt pottery associated with the Salt River or Verde sub-basin).
Mogollon peoples inhabited some of the higher elevations of the catchment, constructing pithouses and often engaging in seasonal migrations. The Mogollon, however, substantially abandoned the watershed around 1400 AD.References
- Michael J.Cohen, Christine Henges-Jeck and Gerardo Castillo-Moreno. 2001. A preliminary water balance for the Colorado River delta, 1992–1998. Journal of Arid Environments 2001 (49): 35–48.
- James P.Collins and Jonathan Snyder. 2002. Sonora tiger salamander recovery plan. U.S.Fish and Wildlife Service, Region 2
- Patrica L.Crown, and James W.Judge, editors. 1991. Chaco & Hohokam: Prehistoric Regional Systems in the American Southwest. School of American Research Press, Sante Fe, New Mexico. ISBN 0-933452-76-4.
- Suzanne K.Fish. 2000. Hohokam Impacts on Sonoran Desert Environment. in Imperfect Balance: Landscape Transformations in the Precolumbian Americas. ed by David L. Lentz. Columbia University Press, New York, pages 251-280
- James Galloway. 2002. Optimizing nitrogen management in food and energy production. books.google.com 1013 pages
- Paul C.Marsh. 1991. Spikedace recovery plan. U.S.Fish and Wildlife Service, Region 2
- Stephen Plog. 1997. Ancient Peoples of the American Southwest. Thames and Hudson, London, England. ISBN 0-500-27939-X
- Mike Sredl and Randy Jennings. 2007. Chiricahua leopard frog recovery plan. U.S.Fish and Wildlife Service Region 2
- Henry Smith Turner. 1966. The original journals of Henry Smith Turner with Stephen Watts Kearny to New Mexico and California, 1846-1847. Ed. Dwight L.Clarke. University of Oklahoma Press, Norman, Oklahoma
- Harold M.Tyus. 1998. Razorback sucker recovery plan. U.S.Fish and Wildlife Service, Region 6
By identifying the positive health effects of a reduction in air pollution exposure, a new NIEHS-funded study led by Junfeng (Jim) Zhang, Ph.D., a professor in the Keck School of Medicine at the University of Southern California (USC), shows how air pollution contributes to cardiovascular disease (CVD) risk.
“We believe this is the first major study to clearly demonstrate that changes in air pollution exposure affect cardiovascular disease mechanisms in healthy young people,” said Zhang.
This environmental health research, with real-world conditions, was possible because the Chinese government agreed to temporarily improve air quality in Beijing, as a stipulation for hosting the 2008 summer Olympic Games. To clean up Beijing for the Olympic Games in China, factories were closed down and car traffic was limited. This governmental air quality intervention set the stage for a controlled examination of pollution-mediated health effects.
“Beijing is one of the most polluted cities in the world,” said Zhang. “We wanted to take advantage of such a huge intervention and look at what happens to people biologically.”
Seizing the unique opportunity to gauge changes in air quality, a team led by Zhang measured air pollutants before, during, and after the Olympic Games. At the same time, the researchers also measured seven markers of cardiovascular health in 125 healthy, non-smoking, young people, who were an average of 24 years old. Several blood plasma factors, cell counts, blood pressure, and heart rate were examined.
Air pollution exposure linked to risk for cardiovascular disease
During the Games, air pollutant concentrations decreased substantially. These air quality improvements were associated with improved biological measurements in the young adults, indicating decreased risk for cardiovascular problems. However, when industrial and automotive activity resumed in Beijing, the cardiovascular health indicators returned to high-risk levels.
Thus, the short-term reduction in air pollution levels during the games led to temporary improvement in cardiovascular health among study participants.
Although the research did not quantify the risk from air pollution exposures, it provides invaluable information for improving the assessment of public health impacts of air pollution reduction.
Public health impacts
During the past two decades, both chronic and short-term air pollution exposures have been related to cardiovascular diseases in numerous observational studies. But few studies have examined how the environment affects disease pathways. Through the investigation of biological indicators clinically related to cardiovascular morbidity or mortality, the work of Zhang’s research team stands apart.
According to the American Heart Association, air pollution can trigger heart attacks and other heart problems, especially in people with underlying cardiovascular conditions. This new study shows that even healthy people, like the young adult participants, may experience cardiovascular disease symptoms from exposure to elevated levels of air pollution. In the United States, more than 40 percent of people live in areas where air pollution threatens their health, according to the American Lung Association State of the Air 2012 report.
Large numbers of people around the world are exposed to air pollution levels as high as Beijing’s, explained Jonathan Samet, M.D., director of the USC Institute for Global Health.
Zhang and fellow authors maintain that their findings further provide data to support the argument that air pollution may be a global risk factor for cardiovascular disease.Citation:
Rich DQ, Kipen HM, Huang W, Wang G, Wang Y, Zhu P, Ohman-Strickland P, Hu M, Philipp C, Diehl SR, Lu SE, Tong J, Gong J, Thomas D, Zhu T, Zhang J. 2012. Association between changes in air pollution levels during the Beijing Olympics and biomarkers of inflammation and thrombosis in healthy young adults.
- Article written by Carol Kelly, a research and communication specialist with MDB, Inc., a contractor for the NIEHS Division of Extramural Research and Training.
Glacier lilies and broad-tailed hummingbirds are out of sync. With the earlier timing of their first blooms the glacier lily is no longer synchronized with the arrival of broad-tailed hummingbirds, which depend on glacier lilies for nectar.Where Have All the Hummingbirds Gone?
The glacier lily as it's called, is a tall, willowy plant that graces mountain meadows throughout western North America. It flowers early in spring, when the first bumblebees and hummingbirds appear. Or did.
The lily, a plant that grows best on subalpine slopes, is fast becoming a hothouse flower. In Earth's warming temperatures, its first blooms appear some 17 days earlier than they did in the 1970s, scientists David Inouye and Amy McKinney of the University of Maryland and colleagues have found.
The problem, say the biologists, with the earlier timing of these first blooms is that the glacier lily is no longer synchronized with the arrival of broad-tailed hummingbirds, which depend on glacier lilies for nectar. By the time the hummingbirds fly in, many of the flowers have withered away, their nectar-laden blooms going with them.
Broad-tailed hummingbirds migrate north from Central America every spring to high-mountain breeding sites in the western United States. The birds have only a short mountain summer to raise their young. Male hummingbirds scout for territories before the first flowers bloom.
But the time between the first hummingbird and the first bloom has collapsed by 13 days over the past four decades, say Inouye and McKinney. "In some years," says McKinney, "the lilies have already bloomed by the time the first hummingbird lands." The biologists calculate that if current trends continue, in two decades the hummingbirds will miss the first flowers entirely.
The results are reported in a paper in the journal Ecology. In addition to McKinney and Inouye, co-authors of the paper are Paul CaraDonna of the University of Arizona; Billy Barr of the Rocky Mountain Biological Laboratory in Crested Butte, Colo.; David Bertelsen of the University of Arizona; and Nickolas Waser, affiliated with all three institutions.
"Northern species, such as the broad-tailed hummingbird, are most at risk of arriving at their breeding sites after their key food resources are no longer available, yet ecologists predict that species will move northward as climate warms," says Saran Twombly, program director in the National Science Foundation's Division of Environmental Biology, which funded the research. "These conflicting pressures challenge society to ensure that species don't soon find themselves without a suitable place to live."
Broad-tailed hummingbirds that breed farther south have fewer challenges. "In Arizona, for example," says Inouye, "there's no obvious narrowing of the timing between the first arriving males and the first blooms of, in this case, the nectar-containing Indian paintbrush."
Higher latitudes may be more likely to get out of sync ecologically because global warming is happening fastest there. As the snow continues to melt earlier in the spring, bringing earlier flowering, says Inouye, the mountains may come alive with glacier lilies long before hummingbirds can complete their journey north.
"Where have all the flowers gone?" then will be "where have all the hummingbirds gone?"
May 30, 2012
- Cheryl Dybas, NSF (703) 292-7734 email@example.com
- Where Have All the Flowers Gone?: http://www.nsf.gov/news/news_summ.jsp?cntn_id=119843
- Early Spring Drives Butterfly Population Declines: http://www.nsf.gov/news/news_summ.jsp?cntn_id=123520
Live Chat: Spring Forward--The Ecological Impact of Climate Change on the Seasons:
Pine (scientific name Pinus), is a genus of around 115-120 species of coniferous trees that grow widely around the northern hemisphere from cold boreal to tropical regions. They are abundant over large areas of the huge boreal taiga forests, but species diversity there is low, with only five species (Pinus sylvestris in Europe and Asia, Pinus sibirica and Pinus pumila in Asia, and Pinus banksiana and Pinus contorta in North America); species diversity is much greater in mountain forests at lower latitudes, being high between 20° to 45°N, and at a maximum in Mexico, California, and southern China.
The northernmost and most widely distributed is Pinus sylvestris, reaching well north of the Arctic Circle at 71°N in Norway, and the southernmost is Pinus merkusii, which reaches just south of the Equator at 2°S in Sumatra. Several species are rare, and some critically endangered; the rarest is Pinus squamata, with under 40 individuals in Yunnan, southwest China.Subgenera
The genus is divided into two subgenera, subgenus Pinus (hard pines) with a double vascular bundle in the leaves, and subgenus Strobus (soft pines) with a single vascular bundle in the leaves. Subgenus Strobus has sometimes also been divided into two subgenera, subgenus Strobus in a strict sense (white pines) with cone scales with a terminal umbo, and subgenus Ducampopinus (lacebark, pinyon and bristlecone pines) with cone scales with a dorsal umbo (in which they resemble subgenus Pinus), but this morphological subdivision does not match genetic relationships, and the two are now combined. Each of the two subgenera are further divided into several sections. The most distinct pines both genetically and morphologically are Pinus nelsonii from northeast Mexico, and Pinus krempfii from southern Vietnam, both are classified in monotypic sections and probably very early separated from other pines.Morphology
Pines are small to very large trees; the tallest are Pinus lambertiana and Pinus ponderosa, both from western North America, which both reach just over 80 metres tall and two to three metres trunk diameter. By contrast, Pinus culminicola from northeast Mexico, Pinus pumila from northeast Asia, and Pinus mugo subsp. mugo from central Europe, are all shrubby plants rarely exceeding three to four metres high. Pines have three types of leaves. Firstly on seedlings one to two years (rarely to five years or more) old, spirally arranged green or glaucous-green needle-like juvenile leaves which range from two to six cm long on. Then on adult foliage, two types, brown scale-leaves a few millimetres long on the branches, and clusters (fascicles) of green needles in the axils of the scale leaves, with two, three or five (rarely one, four or six) needles per fascicle; it is these fascicles that are the familiar pine needles.
The needles are evergreen, with persistence ranging from two to 45 years; they are semicircular or triangular in cross-section, often sharply pointed, and have lines of stomata (breathing pores) on all sides or just on the adaxial side (as also in spruces Picea, but unlike other Pinaceae genera where the stomata are concentrated on the abaxial side). Needle length varies from 2 cm (in Pinus banksiana) up to 45 cm (in Pinus palustris, Pinus devoniana and Pinus engelmannii) and thickness from 0.5-3 mm.
The pollen cones are 10-50 mm long, and shed soon after pollen release in spring. The seed cones are produced in spring and in most species mature over two growing seasons 18-24 months later (longer, over three growing seasons in a few, up to 36 months in Pinus pinea); they are erect at first when pollinated, then turn sideways to pendulous as they mature; length varies from 3 cm (in several species) to 65 cm (in Pinus lambertiana) and colour from yellow-green to red to dark purple. The cone scales have a distinct umbo (uniquely indistinct in Pinus nelsonii) which comprises the first season's growth and apophysis, which develops in the second season. Species with a three growing season development have an umbo with a concentric ring from the second season, and the apophysis in the third season.Ecology
In several species, the cones have thick, armoured scales and spined umbos as a defence against seed predators (primarily squirrels Sciuridae); this development is most extreme in Pinus coulteri, where the ripe cones may weigh three to four. There are two winged seeds under each cone scale; the seeds are blackish-brown to golden-brown, and range from three millimetres (in Pinus banksiana) to 28 mm (in Pinus maximartinezii) long.
In species with small seeds, the seed wings are long, and effective for wind dispersal, while in species with large seeds, the wings are vestigial and the seeds are dispersed by birds, mainly various genera in the family Corvidae (notably Aphelocoma, Cyanopica, Gymnorhinus, and Nucifraga). Species with bird-dispersed seeds typically have many features of the cone such as soft scales which also aid bird access.Uses
Pines are a major source of commercial wood throughout the world, with extensive plantations both throughout the native range of the genus, and also widely in the southern hemisphere. The wood is used for general construction, plywood, interior finishing, boxes, and also for pulp and paper. Pines are used to a small extent as Christmas trees, although they are not as popular as spruces or firs (Abies species). Pine resin is extensively used to produce turpentine. Several pines are widely planted as landscape and ornamental trees, and numerous cultivars have been developed, with variations in growth rates, needle colour, and form.Selected literature
- Businský, R. (2008). The Genus Pinus L., Pines. Acta Pruhoniciana 88: 1-126.
- Encyclopedia of Life (2012) Pinus. Genus curators M.Frankis and R.Hole Jr
- Farjon, A. (2005). Pines: Drawings and Descriptions of the Genus Pinus, 2nd ed. Koeltz Scientific.
- Gernandt, D. S., et al. (2005). Phylogeny and classification of Pinus. Taxon 54 (1): 29–42.
- Huxley, A., ed. (1992). New RHS Dictionary of Gardening. Macmillan.
- Lanner, R. M. (1996). Made for Each Other: A Symbiosis of Pines and Birds. Oxford.
- Mirov, N. T. (1967). The Genus Pinus. Ronald. Richardson, D. M., ed. (1998). Ecology and Biogeography of Pinus. Cambridge.
- Rushforth, K. (1987). Conifers. Helm. Syring, J., et al. (2007). Widespread Genealogical Nonmonophyly in Species of Pinus Subgenus Strobus. Syst. Bot. 56 (2): 163–181.
Tobacco industry interference is the theme of this year’s World No Tobacco Day, which takes place on 31 May 2012. The global tobacco epidemic kills nearly 6 million people each year.World No Tobacco Day:
31 May 2012
The World Health Organization (WHO) has selected "tobacco industry interference" as the theme of this year's World No Tobacco Day, which will take place on Thursday, 31 May 2012.
The campaign focuses on the need to expose and counter the tobacco industry's brazen and increasingly aggressive attempts to undermine the WHO Framework Convention on Tobacco Control (WHO FCTC) because of the serious danger they pose to public health.
Tobacco use is one of the leading preventable causes of death. The global tobacco epidemic kills nearly 6 million people each year, of which more than 600,000 are people exposed to second-hand smoke. Unless we act, it will kill up to 8 million people by 2030, of which more than 80% will live in low- and middle-income countries.
As more and more countries move to fully meet their obligations under the WHO FCTC, the tobacco industry's efforts to undermine the treaty are becoming more and more energetic.
For example, in an attempt to halt the adoption of pictorial health warnings on packages of tobacco, the industry recently adopted the novel tactic of suing countries under bilateral investment treaties, claiming that the warnings impinge the companies' attempts to use their legally-registered brands.
Meanwhile, the industry's attempts to undermine the treaty continue on other fronts, particularly with regard to countries' attempts to ban smoking in enclosed public places and to ban tobacco advertising, promotion and sponsorship.
World No Tobacco Day 2012 will educate policy-makers and the general public about the tobacco industry's nefarious and harmful tactics.
It will also be in keeping with the letter and the spirit of the WHO FCTC. The preamble of the treaty recognizes "the need to be alert to any efforts by the tobacco industry to undermine or subvert tobacco control efforts and the need to be informed of activities of the tobacco industry that have a negative impact on tobacco control efforts".
In addition, Article 5.3 of the treaty states that "in setting and implementing their public health policies with respect to tobacco control, Parties shall act to protect these policies from commercial and other vested interests of the tobacco industry in accordance with national law".
Furthermore, the guidelines to the implementation of Article 5.3 state that Parties are recommended to "raise awareness about…tobacco industry interference with Parties' tobacco control policies".
On World No Tobacco Day 2012, and throughout the following year, WHO will urge countries to put the fight against tobacco industry interference at the heart of their efforts to control the global tobacco epidemic.Editor's Note
- Also, see: Thirdhand smoke exposure concerns in the Encyclopedia of earth.
The Okavango River drains a closed basin in southern Africa, with most of the flow dissipating in the Okavango Alluvial Fan within the nation of Botswana. The Okavango course prehistorically included an outflow to the ocean; however, geologic events of uplift and rifting over the prior million years have converted the Okavango Basin to an endorheic system. The Okavango River not only supports a large assemblage of fish and other aquatic biota, but its drainage area embraces habitat for a large variety of mammals, birds and other terrestrial organisms.
The southern Okavango Basin manifests rich archaeological arrays of Early Stone Age tools that demonstrate this area was an important locus for early man and even earlier tool-making hominid species; this Eartly Stone Age culture thrived in the region in an era of a much wetter climate, when the Makgadikgadi Pan was a vast permanent lake along the Okavango River.
The Makgadikgadi Pan is a large depression (the Kalahari Basin) that once held a lake that spanned most of northern Botswana. The Zambezi, Okavango and Kwando/Chobe Rivers fed this ancient Lake. The formation of various faults on the southern extremity of the East African Rift Valley diverted the flow of these rivers away from the lake, causing it to slowly dry up. This drying process concentrated salts in the lake bed, eventually leaving flat, salt-saturated clay pans (the Makgadikgadi Pans complex). The lake was its deepest in the area of the Ntwetwe and Sua Pans, which were the last areas to dry up, and are today the most saline. Steep escarpments of white calcrete, marking the perimeter of the ancient lake, run along the shores of the pans, rising between 70 and 100 meters (m) above their surface. The only body of water to remain from the once massive lake is the Okavango Alluvial Fan in the northeast of Botswana.Hydrology
Although prehistorically the Okavango had a discharge that eventually led to the sea, in modern times the basin is endorheic, with most of the river flow terminating in the porous soils of the Okavango Alluvial Fan (usually but incorrectly termed the Okavango Delta). Rising in Angola, the Okavango has a total length of approximately 1600 kilometres.
One of the endemic species in the Okavango River is the 30 centimetre (cm) long [demersal] broadhead catfish (Clariallabes platyprosopos). Another example native demersal fish species occurring in the Okavango is the 32 cm smoothhead catfish (Clarias liocephalus).
Native [benthopelagic] species occurring in the Okavango River include the ten cm Okavango tilapia (Tilapia ruweti), the nine cm hyphen barb (Barbus bifrenatus) and the six cm spottail barb (Barbus afrovernayi).
Native [pelagic fish] species found in the Okavango River include the 95 cm elongate tigerfish (Hydrocynus forskahlii), the 11 cm sharptooth tetra (Micralestes acutidens) and the nine cm Okavango robber (Rhabdalestes maunensis).Terrestrial ecoregions
The chief ecoregions within the Okavango Basin are:
- Zambezian baikiaea woodlands
- Zambezian flooded grasslands
- Zambezian and mopane woodlands
- Kalahari acacia baikiaea woodlands ecoregion
- Zambezian halophytics
The Zambezian baikiaea woodlands cover much of the northern Okavango basin along the Angola/Botswana border area. Baikiaea plurijuga is the sole dominant, forming a fairly dense, dry, semi-deciduous forest with trees up to 20 metres in height. There is a dense and shrubby [understory] of Combretum engleri, Pteleopsis anisoptera, Pterocarpus antunesii, Guibourtea coleosperma, Dialium engleranum, Strychnos spp., Parinari curatellifolia, Ochna pulchra, Baphia massaiensis subsp. obovata, Diplorhynchus condylocarpon, Terminalia brachystemma, Burkea africana, Copaifera baumiana and Bauhinia petersiana serpae. Lianas and climbers are also common in the understory, including Combretum elaeagnoides, C. celastroides, Dalbergia martinii, Acacia ataxacantha, Friesodielsia obovata, and Strophanthus kombe. Smaller shrubs are scattered beneath the thicket. The herb layer is conspicuous solely during the rainy season. Grasses vary from sparse to dense and include Leptochloa uniflora, Oplismenus hirtellus, Panicum heterostachyum, and Setaria homonyma. Other conspicuous herbs are Aneilema johnstonii and Kaempferia rosa.
In the area west of the Okavango Alluvial Fan and in the area occupying southeast Namibia, the tree savanna becomes dominated by Baikiaea plurijuga, with varying proportions of Colophospermum mopane and Burkea africana. With fire protection, a dense shrub layer develops and Baphia massaiensis, Bauhinia petersiana, and Paropsia brazzeana are all common. The grass layer is sparse when the shrubby understory is well developed, but when it is more open, species such as Aristida meridionalis, A. congesta, Eragrostis pallens, and E. lehmanniana are found. Baikiaea plurijuga (Caesalpinaceae) is fire sensitive and when fire damage is severe, this cover can vanish completely.
Most of the flow of the Okavango River dissipates within the Okavango Alluvial Fan, in an ecoregion known as the Zambezian flooded grasslands. this ecoregion falls within the center of distribution of the globally threatened slaty egret (Egretta vinaceigula, VU). Largely restricted to this ecoregion, this species is an uncommon resident of the marshes and floodplains of the Okavango, Chobe/Kwando, and the Caprivi Strip as well as from the Zambezi River Valley northwards to the Bangweulu swamps.
At the southern edge of the Okavango Alluvial Fan and with a narrow finger extending north across the Namibian border is the Zambezian and mopane woodlands. The mopane tree characterizes the entire ecoregion, and in many places dominates to the exclusion of other species, particularly trees. Mopane trees are ecologically valuable as browse for numerous animals, notably elephants, and economically the wood is prized for building material and fuel. In addition, this tree is the major host for the seasonally abundant mopane worm (Gonimbrasia belina), the larval stage of a moth which is characteristic of the mopane woodlands. The mopane worm is an important human food and economic resource. Other important taxa in the ecoregion are the families Combretaceae and Mimosaceae, which are represented by 34 and 56 tree and shrub species respectively.
The Kalahari acacia baikiaea woodlands ecoregion covers much of the southern portion of the Okavango Basin. Deciduous tree and bush savanna covers most of the ecoregion, in the sandveld area. Taller trees are mainly confined to low sand ridges and are dominated by Terminalia sericea, Burkea africana, Peltophorum africanum, Croton gratissimus, Rhus tenuinervis, Acacia giraffe, A. fleckii, A. luederitzii, Cobretum zeyheri, C. apiculatum, and Ziziphus mucronata. A shrub savanna occurs on the gently rolling plains between the sand ridges and is mainly composed of Dichrostachys cinerea, Grewia flava, G. flavescens, Acacia mellifera, Bauhinia macrantha, Ximenia caffra, and Commiphora pyracanthoides. The grass cover includes Stipagrostis uniplumis, Aristida meridionalis, A. congesta, Eragrostis pallens, E. superba, Heteropogon contortus, Cymbopogon excavatus, and Digitaria eriantha.
The Zambezian halophytics stretch out within the southern portion of the Okavango Basin. This seasonal lake represents an overflow area of the Okavango, which bears surface water as a large shallow lake, the Makgadikgadi Pan, when the Okavango overflows its usual sump in the Okavango Alluvial Fan. On the saline fringes two macrophytes predominate; Sporobolus spicatus and the spiny grass Odyssea paucinervis. Salt marshes are found scattered around the wetter fringes of the pans. These marshes support species such as Portulaca oleracea, Sporobolus tenellus, and Saudea fruticosa. Surrounding the pans on a larger scale (on less brackish soil) are grasslands dominated by Odyssea paucinervis and Cynodon dactylon with Cenchrus ciliaris and Eriochloa meyeriana dominating the crests of calcrete escarpments. These grasslands have few trees, except to the west where Hyphaene palms fringe the drainage lines, extending north to Nxai Pan. The fruit of these palms is known as vegetable ivory and is used by the local people to make necklaces and heads for walking sticks. To the north and northwest of Ntwetwe Pan individual baobab (Adansonia digitata), Acacia kirkii, and Acacia nigrescens trees are found scattered throughout the grasslandPrehistory
Significant recovery of Early Stone Age tools has derived from the southern part of the watershed in the Makgadikgadi Pans, as vestiges of habitation by Homo sapiens and even Homo habilis. Much of the extant collection is exhibited at Jack's Camp Museum located in the north end of the pans. Field reconnaissance in the dry lakebeds yielded extensive surficial specimens of early stone tools and later projectile points.
Late Stone Age man would have lived in the southern Okavango Basin in huts made of sticks and grass in nomadic groups of 15 to 60 individuals .The women would have concentrated on gathering fruits and nuts, while men created snares of twine to catch springhares emerging from their burrows. Springbok and eland were hunted by spear and arrow, as the Later Stone Age tools had become quite sophisticated. Although no rock paintings are found in the pans, somewhat north in the Tsodillo Hills there is a wealth of animal and human subject rock art, some dating as early as 24,000 years before present.
- Fishbase. 2010. Species in Okavango
A.Gieske. 1996. Modelling of the surface overflow of the Okavango delta, Botswana Notes and Records, vol. 28, pp 165-192
C. Michael Hogan. 2008. Makgadikgadi, The Megalithic Portal, ed. A.burnham
- B.J.Huntley. 1978. Ecosystem conservation in southern Africa. M.J.A. Werger, editor. Biogeography and Ecology of Southern Africa. W. Junk, The Hague. ISBN: 9061930839
- Graham McCulloch. 2003. The ecology of Sua Pan and its flamingo populations, PhD thesis, University of Dublin, Ireland
- S.N.Stuart, R.J. Adams and M.D. Jenkins. 1990. Biodiversity in sub-Saharan Africa and its Islands. Chapter 8: Botswana. Occasional Papers of the IUCN Species Survival Commission No. 6. IUCN, Gland, Switzerland. ISBN: 2831700213
- Thomas Tlou and Alec Campbell. 1984. History of Botswana. MacMillan ISBN 99912-74-08-7
- M.J.A.Werger. 1978. Biogeography and Ecology of Southern Africa. Monographie Biologicae vol. 31., The Hague. ISBN: 9061930839
- World Wildlife Fund. 2002. Zambezian flooded grasslands ecoregion
Research finds that the global carbon pool in seagrass beds is as much as 19.9 billion metric tons. They are vital to understanding climate change—they can store up to twice as much carbon as the world's temperate and tropical forests.Seagrasses Can Store as Much Carbon as Forests
Seagrasses are a vital part of the solution to climate change and, per unit area, seagrass meadows can store up to twice as much carbon as the world's temperate and tropical forests.
So report researchers publishing a paper in the journal Nature Geoscience. The paper, "Seagrass Ecosystems as a Globally Significant Carbon Stock," is the first global analysis of carbon stored in seagrasses. The results demonstrate that coastal seagrass beds store up to 83,000 metric tons of carbon per square kilometer, mostly in the soils beneath them.
As a comparison, a typical terrestrial forest stores about 30,000 metric tons per square kilometer, most of which is in the form of wood. The research also estimates that, although seagrass meadows occupy less than 0.2 percent of the world's oceans, they are responsible for more than 10 percent of all carbon buried annually in the sea.
"Seagrasses only take up a small percentage of global coastal area, but this assessment shows that they're a dynamic ecosystem for carbon transformation," said James Fourqurean, the lead author of the paper and a scientist at Florida International University and the National Science Foundation's (NSF) Florida Coastal Everglades Long-Term Ecological Research (LTER) site. The Florida Coastal Everglades LTER site is one of 26 such NSF LTER sites around the world in ecosystems from forests to tundra, coral reefs to barrier islands.
"Seagrasses have the unique ability to continue to store carbon in their roots and soil in coastal seas," said Fourqurean. "We found places where seagrass beds have been storing carbon for thousands of years."
The research was led by Fourqurean in partnership with scientists at the Spanish High Council for Scientific Investigation, the Oceans Institute at the University of Western Australia, Bangor University in the United Kingdom, the University of Southern Denmark, the Hellenic Center for Marine Research in Greece, Aarhus University in Denmark and the University of Virginia.
Seagrass meadows, the researchers found, store ninety percent of their carbon in the soil--and continue to build on it for centuries. In the Mediterranean, the geographic region with the greatest concentration of carbon found in the study, seagrass meadows store carbon in deposits many meters deep. Seagrasses are among the world's most threatened ecosystems. Some 29 percent of all historic seagrass meadows have been destroyed, mainly due to dredging and degradation of water quality. At least 1.5 percent of Earth's seagrass meadows are lost every year. The study estimates that emissions from destruction of seagrass meadows can potentially emit up to 25 percent as much carbon as those from terrestrial deforestation.
"One remarkable thing about seagrass meadows is that, if restored, they can effectively and rapidly sequester carbon and reestablish lost carbon sinks," said paper co-author Karen McGlathery, a scientist at the University of Virginia and NSF's Virginia Coast Reserve LTER site. The Virginia Coast Reserve and Florida Coastal Everglades LTER sites are known for their extensive seagrass beds.
Seagrasses have long been recognized for their many ecosystem benefits: they filter sediment from the oceans; protect coastlines against floods and storms; and serve as habitats for fish and other marine life. The new results, say the scientists, emphasize that conserving and restoring seagrass meadows may reduce greenhouse gas emissions and increase carbon stores--while delivering important "ecosystem services" to coastal communities.
The research is part of the Blue Carbon Initiative, a collaborative effort of Conservation International, the International Union for Conservation of Nature, and the Intergovernmental Oceanographic Commission of UNESCO.
May 21, 2012
- Cheryl Dybas, NSF (703) 292-7734 firstname.lastname@example.org
- NSF Florida Coastal Everglades LTER Site: http://fce.lternet.edu/
- NSF Virginia Coast Reserve LTER Site: http://www.vcrlter.virginia.edu/home1/index.php
- NSF LTER Network: http://www.lternet.edu
Florida Coastal Everglades: Alligator Commuters Link Salt, Freshwater Ecosystems:
Gulf Oil Spill: NSF Funds Research on Effects on Florida Everglades:
The Draa River of Morocco rised in the High Atlas Mountains and flows to the Atlantic Ocean. Even though the Draa Basin is sparsely populated compared to world standards, the human population exacts an overdrafting of the river and its associated groundwater by historic standards, leading to an undersupply of the river's waters for humans as well as the indigenous riparian biota. In fact land use patterns along the Draa Valley have led to human settlements that are solely centered on the Draa River, with intense extraction for agricultural and domestic use, as the virtually sole water source for this arid region.
The Draa Valley is noted for its rich heritage of petroglyphs and rock paintings, left by an era of humans when the landscape was more lush and hospitable to agriculture. Furthermore, the Draa is one of the earliest noted rivers in recorded history on the African Atlantic shores, when Hanno the Navigator chronicled sighting the Draa mouth circa 500 BC.Hydrology
The Draa Basin is relatively arid, incurring only about 25 centimeters of precipitation annually, except for higher reach parts of the catchment in the High Atlas. The Draa generally drains southern slopes of the High Atlas Mountains and Anti-Atlas Mountains, prior to eventual discharge to the Atlantic near Tan Tan. Historically the Draa has been considered a permanent river, but over-extraction in modern times makes its flow throughout all reaches as problematic. In any case south of the Draa Valley, there is no more southerly perennial river (or standing lake) in North Africa on the Atlantic shores.Water quality
Water quality is a matter of concern in the vicinity of and downriver from human settlements along the oasis chains; impacts stem from agricultural return flows that are ion rich and from discharge of typically untreated or partially treated domestic sewage. Even though the human population densities are not considered high by world perspectives, the human densities and extraction/water use rates are high by historic standards, and with regard to river flow rates. Correspondingly the percolation rates of extracted and used water are high in the relatively porous soils of the generally level areas of the plains. Therefore, it is not surprising that in the vicinity of oases there are high sulfate levels in groundwater (generally above 400 milligrams per litre); moreover, nitrate levels in groundwater are around 27 milligrams per litre, and reflect the fact that most domestic sewage from the oasis settlements are discharged untreated to reach the groundwater.Aquatic biota
There are a number of endemic cyprinidae fish species endemic to the High Atlas reaches of the Draa catchment as well as drainages of the north slopes of the High Atlas; unfortunately, not enough research has gone into the fish species of this region to provide accurate mapping. Barbus lepineyi is an example endemic fish to the Draa River Basin.Terrestrial ecoregions
Map source: World Wildlife Fund
The highest elevation reaches of the Draa catchment are covered by the Mediterranean High Atlas juniper steppe ecoregion. This ecoregion covers the uppermost ridgeline of the Draa drainages and also stores snowpack for vital late season runoff in the Draa Basin as well as the key urban areas in the watersheds to the north serving Fes, Marrakech and Meknes.
Next highest elevation easternmost reaches of the Draa Basin are covered by Mediterranean woodlands and forests. This ecoregion hosts an important avian assemblage, with over 120 species, including an endemic subspecies of great spotted woodpecker, Dendrocopos major numidus, an endemic subspecies of grey shrike, Lanus meridionalis algeriensis, the endangered Algerian nuthatch (Sitta ledanti), and raptors such as golden eagle (Aquila chrysaetos), black-shouldered kite (Elanus caeruleus), short-toed eagle (Circaetus gallicus), booted eagle (Hieratus pennatus), and the vulnerable lesser kestrel (Falco naumanni). Reptiles are also well represented in these forest ecosystems, including the spurred tortoise (Testudo graeca VU), common chameleon (Chamaeleo chamaeleon), North African ocellated lizard (Lacerta pater), Atlas mountain viper (Macrovipera mauritanica), Olivier’s desert-racer (Mesalina olivieri), Eumeces algeriensis, Chalcides mauretanicus, Lataste’s viper (Vipera latasti), Acanthodactylus maculatus, A. savigni, A. lineomaculatus.
The westernmost terrestrial ecoregion through which the Draa River flows is the Mediterranean acacia-argania woodlands and thickets. The major plant species which develop with Argania are: Periploca laevigata, Senecio anthephorbium, Launaea arborescens, Warionia saharae, Acacia gummifera, Rhus trpartitum, Withania frutescens, Euphorbia officinarum, Cytisus albidus, Ephedra altissima, and Tetraclinis articulata. The boundaries of the ecoregion correspond to those of the boundaries of the Argania forest. Acacia gummifera grows in shrubs and is a common companion species to the argan tree. Other acacia species such as Acacia ehrebengiana are more common in inland, and are widely distributed through out the Sahara Desert. Balanites aegyptiaca and Maerua crassifolia commonly grow among Acacia-Argania woodlands in the eastern part of the ecoregion.Important Bird Areas
The nearly-perennial rivers and coastal wetlands of Morocco are a key flyway for migrant palearctic species coming south from Europe to rest or overwinter. The following two Important Bird Areas are associated with the Draa catchment.
The Barrage al Monsour Ad-Dhabi is an unprotected reservoir formed near the confluences of the Dades River and Ourzatate River by construction of a hydroelectric plant in 1972; this reservoir is near the town of Ourzatate. Along portions of the shallow perimeter of the lake are dense vegetative stands of Cynodon dactylon, Phragmites australis and Tamarix canariensis. Known to breed here are the bird species marbled duck (Marmaronetta angustirostris) and ruddy shelduck (Tadorna ferruginea).
The Msseyed is an unprotected area about 70 kilometres east of Tan Tan between the Draa Valley and . The extreme northwest of the Msseyed holds dense stands of Argania spinosa and Euphorbia echinus; however, in the more arid southeastern part of the Msseyed are the densest known stands in Morocco of Acacia raddiana, as well as vigourous growth ol Limoniastrum ifniense and Nitraria retusa. Key avian species found here are the M. angustirostris and T. ferruginea.Prehistory and ancient history
A controversial figurine was recovered in the lower Draa Valley near Tan Tan; although the quartzite object resembles a female human form and has been dated to 500,000 to 300,000 years before present, its authenticity as a hominid produced art object is unclear. The object is known in archaeological circles as the Venus of Tan Tan, but analysis and discussion is proceeding to interpret this find; if authenticated as of hominid origin, it would be the oldest art object known, and produced by a near ancestor of Homo sapiens.
In any case the Draa River Valley is rich in prehistoric art, including numerous extant [petroglyphs]. Some of the more important archaeological sites for rock etching and rock painting in the Draa Basin are: Aït Ouaazik ( Asguine Tarna, Tazzarine), Tiouririne e Tisguinine (Zagora) and Foum Chenna (Tinzouline).
Hanno the Navigator of Carthage is the first to note the Draa in written history when he recorded his passage by the mouth, as part of his epic voyage through the Straits of Gibraltar circa 500 BC.References
- Robert G. Bednarik. 2003. A figurine from the African Acheulian. Current Anthropology 44(3): 405-13.
- J.D.Fage, Anthony Oliver Roland and A.D.Roberts, eds. 1979. The Cambridge History of Africa. Cambridge University Press. ISBN 978-0-521-21592-3.
- A.Hammoudi. 1985. Substance and Relation: Water Rights and Water Distribution in the Dra Valley. In: Mayer, A.E. (Ed.), Property, Social Structure, and law in the Modern Middle East. New York: pp. 27–57
- C.Michael Hogan. 2007. Volubilis. Megalithic Portal, ed. A. Burnham
- IUCN. 2011. The Status and Distribution of Freshwater Biodiversity in Northern Africa. Internation Union for Conservation of Nature
- Stephan Klose and Klaus Haaken. Groundwater quality in Ouled Yauob. Impetus Atlas Morocco.
- D.Jacques-Meunié. 1982. Le Maroc Saharien, des origines à 1670. Thèse d'État. 2 tomes, Librairie Klincksieck, Paris
Increasing aridity could lead to major problems for societies and ecosystems in already-arid places.Dead Ahead: Less Rainfall for Drought-Sensitive
Southern Hemisphere Regions?
Warming climate may mean less rainfall for drought-sensitive regions of the Southern Hemisphere, according to results just published by an international research team. Geoscientist Curt Stager of Paul Smith's College in Paul Smiths, N.Y., and colleagues found that rainfall in South Africa during the last 1,400 years was affected by temperature--with more rain falling during cool periods and less during warm ones. The findings, published in the journal Climate of the Past, are supported by the National Science Foundation (NSF).
"The link between climate change and rainfall in certain latitudes can have large effects on ecosystems," said Paul Filmer, program officer in NSF's Directorate for Geosciences. "Plants, for example, may be able to grow in a wider area, or conversely, be squeezed up a mountain or onto a peninsula. When the affected ecosystem supports a food crop, that can mean a bonanza--or a famine."
Theoretical climate models have shown that global warming could push storm tracks southward "and away from the mainlands of southern Africa, South America and Australia," said Stager. "This research supports those predictions of increasing aridity, which could lead to major problems for societies and ecosystems in these already-arid places." A poleward shift in winds could also affect the flow of marine currents around the tip of Africa, changing air and water temperatures farther afield, including in the Atlantic and Indian Oceans.
Stager, lead author of the paper, collected sediment samples from Lake Verlorenvlei in South Africa. By analyzing the diatoms--tiny, glassy-shelled algae--preserved in sediment cores from the bottom of the lake, he and other researchers were able to reconstruct rainfall patterns dating back to 600 A.D. Two Paul Smith's College undergraduate students, Christiaan King and Jay White, also participated in the study, along with scientists from the University of Maine and from institutions in South Africa and Europe.
Rainfall at the southernmost tip of Africa is governed by a sinuous belt of eastward winds that migrate like a meandering river, depending on the season. In summer months, these winds drift closer to Antarctica, carrying rain clouds over the ocean; in winter, the winds move over the African continent. The shifting winds bring rains that provide much of the annual water supply.
"A poleward retreat of these winds would have serious consequences for cities like Cape Town, for farms and wineries, and for local animal and plant communities," Stager said. "The same also appears to be true for the semi-arid winter rainfall regions of South America and Australia-New Zealand."
Michael Meadows, a scientist at the University of Cape Town who co-authored the paper, said that hundreds of species of rare flowering plants native to the area's fynbos ecosystem are threatened by the changes. "These plants are tough, and are already used to dry conditions," Meadows said. "But more aridity could make fires more frequent, which could damage the soils and make it even harder for the plants to survive. "Unfortunately, this is their only native habitat, so such a change might threaten their existence."
According to Stager, such links to mobile storm tracks make these regions exceptionally vulnerable to the effects of greenhouse gas build-up. "When it comes to climate change, there's more to consider than warming alone," he said. "In places like these, increasing drought could bring far-reaching challenges."
May 18, 2012
- Cheryl Dybas, NSF (703) 292-7734 email@example.com
- Ancient Catastrophic Drought Leads to Question: How Severe Can Climate Change Become?: http://www.nsf.gov/news/news_summ.jsp?cntn_id=118718
- Link Between Sunspots, Rain Helps Predict Disease in East Africa: http://www.nsf.gov/news/news_summ.jsp?cntn_id=109789