Date of Award
Doctor of Philosophy (PhD)
Donna L. Schwartz-Barcott
It is estimated that 5 to 20% of neurodevelopmental disabilities in children are caused by environmental toxic exposures. Lead, methylmercury and polychlorinated biphenyls (PCBs) are known to have neurobehavioral and neurodevelopmental consequences in animal models and human population studies. Bioaccumulation and exposures during gestation transfer from mother to fetus via the placenta and to an infant and young child through lactation. Little is known about multiple environmental chemical exposures, especially among childbearing-aged women.
This descriptive and exploratory study involved analysis of existing data from the National Health and Nutrition Examination Survey (NHANES), a national probability sample. Lead, methylmercury and the summed value of four lipid-adjusted PCB congeners (118, 138/158, 153, 180) were measured in the blood or serum of childbearing-aged females aged 16 to 49 of diverse races and ethnicities who were living in the U.S. 1999 to 2004, including a subset of pregnant women. Exposure was defined as two or more xenobiotic blood levels at or above the geometric mean. Sexton, Olden and Johnson’s modified environmental health paradigm (1993) guided the selection of 62 measures of vulnerability (susceptibility- and exposure-related attributes, socioeconomic factors and race-ethnicity).
Findings were reported for weighted (adjusted) data. The prevalence of exposures was widespread among childbearing-aged women, one fifth of whom had xenobiotic blood levels at or above the geometric mean for all three chemicals. Overall, pregnant women had lower prevalence rates. Best-fit logistic regression exposure model contained 13 variables. Three were notable. Any fish consumption in past 30 days tripled the risk. A non-linear relationship was demonstrated with increasing age, exponential at ages 40 to 49. Past and current breastfeeding was protective for these women. Current pregnancy was protective with regard to individual chemical exposures only. Statistically significant two-way interactions were identified even though the paradigm could not be fully tested.
Further research on exposures to multiple environmental chemicals using the modified environmental health paradigm is needed. Xenobiotic biomonitoring in conjunction with risk communication among childbearing-aged women is encouraged. Precautionary level interventions aimed at eliminating or minimizing exposures are urgently needed. Bioaccumulation and transgenerational consequences of exposures should be addressed in public health policy.
Thompson, Marcella Remer, "EXPOSURES TO MULTIPLE ENVIRONMENTAL CHEMICALS (LEAD, METHYLMERCURY AND POLYCHLORINATED BIPHENYLS) AMONG CHILDBEARING-AGED WOMEN IN THE U.S." (2011). Open Access Dissertations. Paper 83.