Analysis of PCB congeners related to cognitive functioning in adolescents.

To investigate the characteristics of PCBs that are linked to cognitive functioning, those congeners that were concurrently found in 271 Mohawk adolescents were grouped according to structure (dioxin-like or non-dioxin-like) and persistence (persistent or low-persistent). After the effects of the congener groups were orthogonalized, regression analyses (controlling for a number of variables found to be related to the cognitive outcomes) examined the relationship of each congener group to scores on three cognitive tests (the non-verbal Ravens Progressive Matrices, the Test of Memory and Learning, and the Woodcock Johnson-Revised). Five subtests from these cognitive tests were found to be associated with one or more PCB congener groups, most often at a moderate level. Two measures of long-term memory (Delayed Recall and Long Term Retrieval) were associated with all four congener groups. Nevertheless, examination of the role of individual congeners in the significantly related congener groups revealed that almost all congeners associated with cognitive outcomes were non-dioxin-like and ortho-substituted. A notable exception was the Ravens test where scores were associated only with dioxin-like congeners. This finding adds to the limited evidence of neurotoxic effects of dioxin-like congeners. Auditory Processing was related only to the persistent congener group. The association of the non-persistent congener group with three cognitive test scores (Delayed Recall, Long Term Retrieval and Comprehension-Knowledge) suggests that the Mohawk adolescents have experienced continuing or recent environmental exposure to PCBs that is sufficient to result in detectable cognitive decrements. Comparison of our findings with those of other human studies was limited by the relative lack of specificity of both PCB measures and cognitive outcome measures in much previous work.

Growth of infants' length, weight, head and arm circumferences in relation to low levels of blood lead measured serially.

To determine whether levels of blood lead during gestation and infancy that are below the CDC action level of 10 microg/dl affect infant growth, we studied 211 disadvantaged mother-infant pairs from Albany, NY. Mothers' lead levels were low (second trimester chi = 2.8 microg/dl) as were infants' (chi = 3.3 microg/dl at 6 months; 6.4 microg/dl at 12 months). Multiple linear regression analyses showed that second trimester lead levels were related to reduced head circumference at 6 and 12 months. Infants of mothers with second trimester lead at or above the median (>or=3 microg/dl) exhibited negative associations between blood lead and head circumference at 6 and 12 months, and with weight-for-age, weight-for-length, and upper arm circumference at 6 months, but those below the median did not. Infants' 6-month lead level was related to head circumference at 12 months in the total sample, and in the subsample of infants whose blood lead was above the infants' 6-month blood lead median. Infants were also grouped by changes in their relative blood lead status, that is, above vs. below the median, from second trimester to 12 months of age. Infants whose lead levels changed from above to below the median were larger than infants whose lead levels went from below to above the median. The results suggest that lead may affect some dimensions of infant growth at levels below 10 microg/dl, but effects of lead levels less than 3 microg/dl are not evident in this sample.

Relationship of thyroid hormone levels to levels of polychlorinated biphenyls, lead, p,p'- DDE, and other toxicants in Akwesasne Mohawk youth.

BACKGROUND: It is well documented that acute exposure to high levels of persistent organic pollutants, such as polychlorinated biphenyls (PCBs), p,p'-dichlorophenyldichloroethylene (p,p'-DDE), and hexachlorobenzene (HCB), can affect human health including thyroid function. Chronic exposure to multiple toxicants is common but difficult to analyze, and most prior studies have focused on adults or newborns, creating a gap in our understanding of multitoxicant effects among adolescents. OBJECTIVE: We investigated whether levels of PCBs, p,p'-DDE, HCB, mirex, lead, and mercury reflecting past chronic exposure are associated with alterations in levels of thyroid-stimulating hormone (TSH), triiodothyronine (T(3)), total thyroxine (TT(4)), and free thyroxine (FT(4)) among older children and adolescents. METHODS: The sample consists of youth from the Akwesasne Mohawk Nation (n=232) who reside in proximity to several industries that have contaminated the local environment. We used multiple regression analysis to examine the effect of PCB groupings, p,p'-DDE, HCB, lead, and mercury on thyroid hormones after adjusting for sociodemographic covariates and controlling for all other toxicants. RESULTS: Exposure to PCBs affects the thyroid hormone profile in adolescents. The group of persistent PCBs was positively associated with TSH but inversely related to FT(4). Nonpersistent PCBs were significantly and negatively related to FT(4) only. HCB was negatively associated with T(4), and lead was positively associated with T(3). Breast-fed adolescents had higher levels of persistent PCBs and p,p'-DDE but not of nonpersistent PCBs or any other toxicant when compared with non-breast-fed adolescents. Though having lower levels of persistent PCBs and p,p'-DDE, non-breast-fed adolescents exhibited significant relationships between persistent PCBs and TSH and FT(4), but breast-fed adolescents did not. It appears that PCBs from breast milk obscure the relationship between prenatal PCB exposure and thyroid function by adding random variation in PCB levels. CONCLUSION: Our results demonstrate a reduction in thyroid function in adolescents in relation to their current serum levels of PCBs. These observations are consistent with the hypothesis that pre-natal exposure to PCBs alters thyroid function in a long-lasting manner but does not exclude the possibility that postnatal exposure is influential also.

Advancing biocultural models by working with communities: a partnership approach.

Culture and human behavior are recognized today as major forces acting on human biological variation around the world. Studies of the relationships between biology and processes, such as modernization, urbanization, and social stratification, are prominent in our journals and meetings. An ongoing study of the interrelationships between toxicant exposure (organochlorines, lead, and mercury), health, and culture among youth of the Mohawk Nation at Akwesasne is located within this context and is used to analyze the strengths and challenges of a partnership approach to biocultural research. To assist in modeling the complex relationships between health, behavior, and culture, we have employed concepts from contemporary social theory, integrated qualitative and quantitative research, and implemented community-based research principles to develop a partnership approach to research in human biology. The community is directly involved in identifying research goals, developing research protocols appropriate for local cultural sensitivities and complexities, implementing the protocols in the field, and collaborating in the analysis and publication of results. We show the utility of this approach for understanding the relationships of toxicants to behavior and biological outcomes (adolescent growth, sexual maturation, and endocrine system alteration); as well as how it facilitates the agency of participants and communities involved in research, and brings greater social engagement to the development of the new human biology.

PCBs and cognitive functioning of Mohawk adolescents.

This paper reports on the relationships between the cognitive functioning and PCB current body burdens of adolescents in the Mohawk Nation of Akwesasne where there is concern about industrial pollution of the environment. Three cognitive tests (Woodcock Johnson-Revised, Test of Memory and Learning, and Ravens Progressive Matrices) provide 13 subtests that allow a variety of cognitive outcomes to be assessed. A summary measure of PCB level was created from the congeners detected in at least 50% of the participants. The most notable finding was the significant negative relationship between PCB levels and two separate measures of long term memory. There was also a negative relationship with a measure of comprehension and knowledge. Significant relationships were not large, but provide evidence of subtle negative effects of PCB exposure.

Effects of pollution on human growth and development: an introduction.

Pollution is a worldwide problem and its potential to influence the physiology of human populations is great. Studies of human growth and development in relation to pollution have increased in number and quality since the mid-twentieth century. Many studies have found that some pollutants have detrimental effects on human growth, particularly prenatal growth. The heavy metal, lead, is commonly found in human populations and is related to smaller size at birth and studies have reported decrements that range up to about 200 grams. Noise stress from transportation sources also is related to reduced prenatal growth with somewhat smaller decrements reported. Studies of humans exposed to polychlorinated biphenyls, one of the persistent organic pollutants, have reduced size at birth, advanced sexual maturation and altered hormone levels related to thyroid regulation. Thus different pollutants exert effects through different physiological pathways. However, some studies have not observed these effects, which indicates that the situation is complex and requires further study with better study designs. Determining the effects of pollutants on human physiology and growth is difficult as it requires fairly large numbers of subjects who are not purposely exposed but for whom exposure can be measured. These effects of pollutants and the mechanisms of effect require further study to understand and, it is hoped, to blunt or block any detrimental effects on human health and well-being.

Relationship of lead, mercury, mirex, dichlorodiphenyldichloroethylene, hexachlorobenzene, and polychlorinated biphenyls to timing of menarche among Akwesasne Mohawk girls.

BACKGROUND: Children are commonly exposed at background levels to several ubiquitous environmental pollutants, such as lead and persistent organic pollutants, that have been linked to neurologic and endocrine effects. These effects have prompted concern about alterations in human reproductive development. Few studies have examined the effects of these toxicants on human sexual maturation at levels commonly found in the general population, and none has been able to examine multiple toxicant exposures. The aim of the current investigation was to examine the relationship between attainment of menarche and levels of 6 environmental pollutants to which children are commonly exposed at low levels, ie, dichlorodiphenyldichloroethylene (p,p'-DDE), hexachlorobenzene (HCB), polychlorinated biphenyls (PCBs), mirex, lead, and mercury. METHODS: This study was conducted with residents of the Akwesasne Mohawk Nation, a sovereign territory that spans the St Lawrence River and the boundaries of New York State and Ontario and Quebec, Canada. Since the 1950s, the St Lawrence River has been a site of substantial industrial development, and the Nation is currently adjacent to a US National Priority Superfund site. PCB, p,p'-DDE, HCB, and mirex levels exceeding the US Food and Drug Administration recommended tolerance limits for human consumption have been found in local animal species. The present analysis included 138 Akwesasne Mohawk Nation girls 10 to 16.9 years of age. Blood samples and sociodemographic data were collected by Akwesasne community members, without prior knowledge of participants' exposure status. Attainment of menses (menarche) was assessed as present or absent at the time of the interview. Congener-specific PCB analysis was available, and all 16 PCB congeners detected in >50% of the sample were included in analyses (International Union of Pure and Applied Chemistry numbers 52, 70, 74, 84, 87, 95, 99, 101 [+90], 105, 110, 118, 138 [+163 and 164], 149 [+123], 153, 180, and 187). Probit analysis was used to determine the median age at menarche for the sample. Binary logistic regression analysis was used to determine predictors of menarcheal status. Six toxicants (p,p'-DDE, HCB, PCBs, mirex, lead, and mercury) were entered into the logistic regression model. Age, socioeconomic status (SES), and BMI were tested as potential cofounders and were included in the model at P < .05. Interactions among toxicants were also evaluated. RESULTS: Toxicant levels were measured in blood for this sample and were consistent with long-term exposure to a variety of toxicants in multiple media. Mercury levels were at or below background levels, all lead levels were well below the Centers for Disease Control and Prevention action limit of 10 microg/dL, and PCB levels were consistent with a cumulative, continuing exposure pattern. The median age at menarche for the total sample was 12.2 years. The predicted age at menarche for girls with lead levels above the median (1.2 microg/dL) was 10.5 months later than that for girls with lead levels below the median. In the logistic regression analysis, age was the strongest predictor of menarcheal status and SES was also a significant predictor but BMI was not. The logistic regression analysis that corrected for age, SES, and other pollutants (p,p'-DDE, HCB, mirex, and mercury) indicated that, at their respective geometric means, lead (geometric mean: 0.49 microg/dL) was associated with a significantly lower probability of having reached menarche (beta = -1.29) and a group of 4 potentially estrogenic PCB congeners (E-PCB) (geometric mean: 0.12 ppb; International Union of Pure and Applied Chemistry numbers 52, 70, 101 [+90], and 187) was associated with a significantly greater probability of having reached menarche (beta = 2.13). Predicted probabilities at different levels of lead and PCBs were calculated on the basis of the logistic regression model. At the respective means of all toxicants and SES, 69% of 12-year-old girls were predicted to have reached menarche. However, at the 75th percentile of lead levels, only 10% of 12-year-old Mohawk girls were predicted to have reached menarche; at the 75th percentile of E-PCB levels, 86% of 12-year-old Mohawk girls were predicted to have reached menarche. No association was observed between mirex, p,p'-DDE, or HCB and menarcheal status. Although BMI was not a significant predictor, we tested BMI in the logistic regression model; it had little effect on the relationships between menarcheal status and either lead or E-PCB. In models testing toxicant interactions, age, SES, lead levels, and PCB levels continued to be significant predictors of menarcheal status. When each toxicant was tested in a logistic regression model correcting only for age and SES, we observed little change in the effects of lead or E-PCB on menarcheal status. CONCLUSIONS: The analysis of multichemical exposure among Akwesasne Mohawk Nation adolescent girls suggests that the attainment of menarche may be sensitive to relatively low levels of lead and certain PCB congeners. This study is distinguished by the ability to test many toxicants simultaneously and thus to exclude effects from unmeasured but coexisting exposures. By testing several PCB congener groupings, we were able to determine that specifically a group of potentially estrogenic PCB congeners affected the odds of reaching menarche. The lead and PCB findings are consistent with the literature and are biologically plausible. The sample size, cross-sectional study design, and possible occurrence of confounders beyond those tested suggest that results should be interpreted cautiously. Additional investigation to determine whether such low toxicant levels may affect reproduction and disorders of the reproductive system is warranted.

Relationship between blood lead concentration and dietary intakes of infants from 3 to 12 months of age.

Data from a study of mother-infant pairs of low socioeconomic status living in Albany County, NY, were analyzed to determine the influence of diet and nutrition on the blood lead level of infants during the first year of life. Children's diets were assessed at 3-month intervals using a 24-h diet recall as reported by the primary caregiver. The potential impact of dietary consumption of protein, iron, zinc, calcium, vitamin D, and fat, as well as serum vitamin D and ferritin on blood lead levels at 6 and 12 months of age was examined with multivariable statistical analyses, controlling for other influences on lead levels. Neonates' blood lead levels were low at birth (geometric mean=1.6 microg/dL), and none were elevated (> or = 10 microg/dL). By 12 months, the mean blood lead for this sample was 5.1 microg/dL, and 18% of the sample had an elevated blood lead level. We observed significant inverse relationships between infants' 6-month lead level and their intake of zinc, iron, and calcium. At 12 months, low iron intake continued to be associated with higher lead levels, although zinc and calcium did not. Protein had a paradoxical effect, being associated with lower lead at 6 months, but higher lead at 12 months. Serum vitamin D and ferritin were not associated with lead levels, nor was vitamin supplement use. The results reported here emphasize the value of key minerals in the diet to reduce lead absorption during early infancy.

Thyroid function in relation to burden of PCBs, p,p'-DDE, HCB, mirex and lead among Akwesasne Mohawk youth: a preliminary study.

The effects of endocrine disrupting environmental contaminants such as polychlorinated biphenyls (PCBs), hexachlorobenzene (HCB), p,p'-dichlorophenyldichloroethylene (p,p'-DDE), mirex, and lead, are examined in a sample of youth of the Akwesasne Mohawk Nation who are 10-16.9 years of age (n=115). The Akwesasne community is located adjacent to hazardous waste sites where PCBs and other toxicants have contaminated the local ecology. This study examines the relationship between measures of thyroid function and endocrine disrupting environmental toxicants. Both with and without statistical adjustment for other toxicants, as well as age, sex and lipid levels, several indicators of PCB burden are significantly, negatively related to levels of free thyroxine and total thyroxine, and positively to thyrotropin. Lead level was positively related to triidothyronine. Future testing of non-linear relationships is warranted. Despite the linear associations with thyrotropin, free and total thyroxine, PCBs were not related to increased occurrence of these hormones outside the clinically normal range for the testing laboratory.

Maternal blood lead concentration, diet during pregnancy, and anthropometry predict neonatal blood lead in a socioeconomically disadvantaged population.

To determine the influences of maternal diet and nutrition during pregnancy on the blood lead level of neonates, we conducted a study of mother-infant pairs from lower socioeconomic circumstances living in Albany County, New York. Maternal blood lead (MBPb), anthropometry, and diet were assessed in each trimester. Neonates' blood lead (NBPb) levels were low (geometric mean = 1.58 micro g/dL), and none had elevated blood lead. More than 50% of the mothers had intakes below the recommended dietary allowances for zinc, calcium, iron, vitamin D, and kilocalories. As expected, MBPb was strongly and positively related to NBPb. Among the anthropometric measures of maternal nutritional status, variables measuring gain in weight and arm circumference were negatively related to NBPb. In multivariable models reflecting different analytic strageties and including MBPb, anthropometry, and sociodemographic characteristics, dietary intakes of iron and vitamin D were negatively related to NBPb. The effect of zinc varied substantially depending on model covariates. Effects of dietary constituents are difficult to distinguish, given the intercorrelated nature of nutrients in the diet. Nevertheless, the influences of maternal anthropometric variables, iron, and vitamin D on neonatal lead levels are clear in our analyses.