A Methodological Approach to Assessing the Health Impact of Environmental Chemical Mixtures: PCBs and Hypertension in the National Health and Nutrition Examination Survey

Krista L Yorita Christensen,Paul White

doi:10.3390/ijerph8114220

Abstract

We describe an approach to examine the association between exposure to chemical mixtures and a health outcome, using as our case study polychlorinated biphenyls (PCBs) and hypertension. The association between serum PCB and hypertension among participants in the 1999–2004 National Health and Nutrition Examination Survey was examined. First, unconditional multivariate logistic regression was used to estimate odds ratios and associated 95% confidence intervals. Next, correlation and multicollinearity among PCB congeners was evaluated, and clustering analyses performed to determine groups of related congeners. Finally, a weighted sum was constructed to represent the relative importance of each congener in relation to hypertension risk. PCB serum concentrations varied by demographic characteristics, and were on average higher among those with hypertension. Logistic regression results showed mixed findings by congener and class. Further analyses identified groupings of correlated PCBs. Using a weighted sum approach to equalize different ranges and potencies, PCBs 66, 101, 118, 128 and 187 were significantly associated with increased risk of hypertension. Epidemiologic data were used to demonstrate an approach to evaluating the association between a complex environmental exposure and health outcome. The complexity of analyzing a large number of related exposures, where each may have different potency and range, are addressed in the context of the association between hypertension risk and exposure to PCBs.

Highlights

Humans are exposed to a multitude of environmental exposures, and these exposures may interact with one another to alter risk for health outcomes
polychlorinated biphenyls (PCBs) exposure in humans has been linked to numerous adverse health outcomes, including increased risk of elevated blood pressure, or hypertension
As our goal is to illustrate a methodological approach rather than test a hypothesis regarding the true association between PCB exposure and hypertension in the general population, we did not account for the complex survey design of the NHANES in these analyses—results are unweighted and do not include the survey design variables

Summary

Introduction

Humans are exposed to a multitude of environmental exposures, and these exposures may interact with one another to alter risk for health outcomes. In 2008, the National Research Council issued a report urging risk assessors to consider chemical mixtures rather than each component in isolation, when considering effects on human health [1]. The varying ranges in the values of the exposures being assessed, and non-independence of the exposures make it difficult to determine relative contributions of each exposure component. These issues are relevant when assessing human health effects of exposure to polychlorinated biphenyls (PCBs). PCB exposure in humans has been linked to numerous adverse health outcomes, including increased risk of elevated blood pressure, or hypertension. In a 24-year follow up of the Yucheng cohort, Wang et al reported a non-significant 20–40% increase in hypertension risk among exposed persons; results were not presented stratified by congener (or congener group) or level of exposure [3]

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Conclusion