Summaries of Study Results

Hypertension

A total of 758 Anniston residents had multiple measurements of blood pressure, provided information on demographic factors, medications, smoking, and exercise and provided blood samples for determination of PCBs and total serum lipids. Rates of hypertension increased significantly (p‹0.05) with age and concentration of serum PCBs and were higher in African-Americans (n=351) than in Caucasians (n=407). Hypertension also increased with body mass index (BMI), but was not related to total serum lipids levels, gender, smoking or exercise. Among 394 persons not on anti-hypertensive medication, linear regression analysis demonstrated a significant positive relation between serum PCB level and both systolic and diastolic blood pressure. After adjustment for potentially confounding variables, logistic regression gave odds ratios (ORs) for the highest to lowest tertiles of total serum PCBs that exceeded 3.5 for both systolic and diastolic hypertension. When analyzed by quintiles of PCBs, the highest OR was in the third quintile, suggesting a low dose effect. Significant positive associations were also observed between PCB concentrations and systolic and diastolic blood pressure even in normotensive ranges. The strengths of the relationships between PCB exposure and both hypertension and blood pressure suggests that PCB exposure may be an important contributing factor in regulation of blood pressure (Goncharov et al., 2010 [PDF - 201 KB]).

Blood Pressure

Linear regression analysis was used to determine the relationships between blood pressure and serum levels of the various contaminants after adjustment for age, body mass index (BMI), gender, race, smoking and exercise in 394 Anniston residents who were not on anti-hypertensive medication. Other than age total serum PCB concentration was the strongest determinant of blood pressure of the covariates studied. The strongest associations were found for those PCB congeners that had multiple ortho chlorines, although there was also a significant association with dioxin-like TEQs. The chlorinated pesticides showed little or no relationship to blood pressure. The associations were found over the full range of blood pressure as well as in those subjects whose blood pressure was in the normal range. Serum PCBs, especially those congeners with multiple ortho chlorines, seem to be important factors in regulation of blood pressure and hypertension. (Goncharov et al., 2011 [PDF - 411 KB]).

Diabetes

For this cross-sectional study, data were analyzed from randomly selected adults (n=774) who completed the Anniston Community Health Survey and underwent measurements of height, weight, fasting glucose, lipid and PCB levels and verification of medications. Odds ratios (OR) and 95% confidence intervals were calculated to assess the relationships between PCBs and diabetes, adjusting for diabetes risk factors. Participants with pre-diabetes were excluded from the logistic regression analysis. Participants were 47% African American, 70% female with a mean age (standard deviation) of 54.8 (15.9) years. The prevalence of diabetes was 27% and the PCB body burden of 35 major congeners ranged from 0.11 to 170.42 ppb, wet weight. In the overall analysis, ORs were significantly elevated in the 3rd and 5th quintiles following adjustment for risk factors. In participants < 55, the adjusted OR for diabetes was significantly elevated in the highest quintile (p‹0.05), whereas in those > 55, the adjusted analysis demonstrated no significant association. Additionally, elevated total PCB levels, specific congener groups, and dichlorodiphenyldichloroethylene (DDE) were associated with a doubling in the log risk of diabetes among women (p‹0.05) but not in men. In conclusion, we observed significant associations between elevated PCB levels and diabetes mostly due to associations in women and in individuals under age 55 (Silverstone et al., 2012 [PDF - 316 KB]).

Lipids

The objective of the study was to test the hypothesis that levels of the various lipid components (total cholesterol, LDL cholesterol, HDL cholesterol, triglycerides) are differentially associated with concentrations of total PCBs and total pesticides, and further that different congeners, congener groups and different pesticides do not have identical associations in serum samples obtained from Anniston residents in a cross-sectional study.

Fasting serum samples were obtained from 575 residents of Anniston who were not on any lipid-lowering medication and were analyzed for 35 PCB congeners, nine chlorinated pesticides, total cholesterol, LDL and HDL cholesterol and triglyceride concentrations. Associations between toxicant concentrations and lipid levels were determined using multiple linear regression analysis.

We observed that elevated serum concentrations of lipids were associated with elevated serum concentrations of the sum of 35 PCBs and summed pesticides in analyses adjusted for age, race, gender, BMI, alcohol consumption, smoking and exercising status. The strongest associations were seen for PCB congeners with three or four ortho, and at least eight substituted chlorines. Mono-ortho substituted congeners 74 and 156, di-ortho congeners 172 and 194, and tri- and tetra-ortho congeners 199, 196-203, 206 and 209 each were significantly associated with total lipids, total cholesterol and triglycerides. Serum concentrations of HCB and chlordane also had strong associations with lipid components.

Increased concentrations of PCBs and organochlorine pesticides are associated with elevations in total serum lipids, total cholesterol and triglycerides, but the patterns are different for different groups of PCBs and different pesticides. These observations show selective effects of different organochlorines on serum concentrations of different groups of lipids. This elevation in concentrations of serum lipids may be the basis for the increased incidence of cardiovascular disease found in persons with elevated exposures to PCBs and chlorinated pesticides (Aminov et al., 2013).

Maternal PCB Exposure and Birth Weight

We investigated the association between maternal serum PCB concentrations, preterm birth and low birth weight in a population with elevated exposure to PCBs. From 2005-2007, the Anniston Community Health Survey analyzed adult blood samples for total PCBs (sum of 35 congeners). For each child born between 1936 and 2006, mothers self-reported information on preterm births (yes vs. no) and birth weight. Birth weight was dichotomized as low birth weight (‹2500 grams) or not (>=2500 grams). After excluding participants with missing information on PCBs, preterm births or birth weight, there were 395 mothers and 952 children. Random effects were used to account for correlations between infants with the same mother. For 1936-2006 births, there was no statistically significant difference in birth weight over time and no association was detected between PCB and preterm birth. The adjusted OR for the association between PCBs and low birth weight was 1.21 (95% CI: 0.97, 1.50) for all infants and 1.38 (95% CI: 1.06, 1.80) for term infants. These results provide some evidence in support of an association between maternal PCB and low birth weight, but are limited by the timing of maternal serum measurements relative to the births and maternal recall of infant birth outcomes (Dove et al., cleared by ATSDR, not yet published).

Metabolic Syndrome

Metabolic syndrome, a constellation of CVD risk factors including insulin resistance, hypertension, dyslipidemia, abnormal glucose tolerance and central obesity (increased waist circumference) was found to be present in 60% of the Anniston Health Study sample. When restricting the definition to individuals without diagnosed diabetes, the prevalence of Metabolic Syndrome was about 50%. Increasing levels of both β-HCCH, and p,p’-DDT were associated with elevated odds ratios for the presence of Metabolic Syndrome (with and without diabetes); there was no association observed with levels of PCBs. Our findings concerning pesticides are consistent with those reported by Lee and colleagues using NHANES data from 1999-2002, while those for PCBs are in contrast to their results and those of Uemura and his coauthors. The significant positive associations between specific pesticides and Metabolic Syndrome (high CVD risk) as well as the inverse association noted with Mirex, require further study. (Rosenbaum et al., 2010 [PDF - 540 KB])

PCB levels

Serum concentrations of 35 ortho-substituted polychlorinated biphenyl congeners (PCBs) were measured in 765 adults from Anniston, Alabama, where PCBs were manufactured between 1929 and 1971. As part of the Anniston Community Health Survey (ACHS), demographic data, questionnaire information, and blood samples were collected from participants in 2005-2007. Forty-six percent of study participants were African-American, 70% were female, and the median age was 56 years. The median concentration of the sum of 35 PCB congeners (ΣPCBs) was 528 ng/g lipid, with a 90th percentile of 2600 ng/g lipid, minimum of 17.0 ng/g lipid, and maximum of 27,337 ng/g lipid. The least square geometric mean ΣPCBs was more than 2.5 times higher for African-American participants than for White participants (866 ng/g lipid vs. 331 ng/g lipid); this difference did not change materially after adjustment for age, sex, body mass index (BMI) and current smoking. In spite of large differences in absolute PCB levels, relative contributions of individual congeners to ΣPCBs were quite similar between race groups. Nevertheless, while percent contributions to ΣPCBs for most of the most abundant penta- to heptachlorobiphenyls were higher among African-Americans, the percentages were higher in Whites for the lower-chlorinated PCBs 28 and 74 and for octa- to decachlorinated PCBs. No major differences were observed in geometric mean ΣPCBs between women and men when adjusted for age, race, BMI and current smoking (516 ng/g lipid vs. 526 ng/g lipid). Principal component analysis revealed groups of co-varying congeners that appear to be determined by chlorine substitution patterns. These congener groupings were similar between ACHS participants and the National Health and Nutrition Examination Survey (NHANES) 2003-04 sample of the general United States population, despite ACHS participants having serum concentrations of ΣPCBs two to three times higher than those in comparable age and race groups from NHANES . (Pavuk et al., 2014)

Neurocognitive

The Anniston Neurocognitive Study was a parallel but separate study from the ACHS and was conducted by the Civitan International Research Center, University of Alabama – Birmingham. ATSDR has never had access to the full study dataset.

In this study, a relationship was noted between higher PCB levels and less effective non-verbal planning and problem solving in children and potential relationship between lower IQ scores in children and higher PCB levels in their parents. Higher PCB levels were also associated with lower IQ in adults. It should be noted that PCB levels in Anniston children are much lower than in adult Anniston residents and are similar to children throughout the United States (0.25 vs. 0.23 ppb; sum of PCB congeners 138, 153, 180) (data not published).

For a report of PCB levels in Anniston children without the results of neurocognitive tests, see Pavuk et al., 2007 [PDF - 81 KB].

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