An assessment of cumulative exposure to lead and mercury in subsets of the US population

The metals lead and mercury are known to independently exert neurotoxic effects in children following pre- and postnatal exposures. Exposures to lead or mercury in US populations have been largely characterized for each individual metal, and have also been shown to be disproportionately distributed across race/ethnicity and socioeconomic groups. However, not much is known about concurrent or cumulative exposure to both metals in the US population. Generally, emerging research suggests that differences in exposure to multiple pollutants exist in the US population, and these differences may depend on socioeconomics and race/ethnicity. In this study, we assessed the distribution of combined body burdens of lead and total mercury (as a measure of exposure) in the US population using data from the 2001-2002 and 2003-2004 NHANES surveys. This analysis focused on children aged 1-5 because the association between exposure and neurotoxicity is strongest for this age group and also for data availability reasons, and women of child-bearing age (16-49) because of pre-natal exposures. For both study populations, we identified NHANES participants at or exceeding the 75^th or 90^th percentiles for both metals in blood. These individuals were subsequently characterized by race/ethnicity and income using descriptive data analysis methods. This analysis is intended to serve as a case study on potential approaches for estimating cumulative body burdens. Future analysis will include cadmium, the third metal for which NHANES data is available.