Residential Proximity to Metal-Containing Superfund Sites and Toenail Metal Concentrations in a Nationwide Study of US Women

BACKGROUND AND AIM: Superfund sites in the United States contain hazardous substances, including toxic metals, which could potentially expose those living nearby. However, it is unclear whether residential proximity to sites may increase body burden of toxic metals. We aimed to evaluate the association between residential proximity to metal-containing Superfund sites and toenail metal concentrations. METHODS: Metal concentrations (aluminum, antimony, arsenic, cadmium, and lead, ng/g) were measured in toenail clippings collected between 2003-2009 in 2,998 women with a family history of breast cancer. Residential proximity to Superfund sites was measured by living ≤5 or 10 miles of a site (yes/no), site density (sites/mile^2) and an inverse-weighted sum distance measure (sites/mile). Linear regression was used to estimate the difference in toenail metal concentrations and 95% confidence intervals (CIs) per unit change in residential proximity measures (β). We evaluated whether associations varied by race/ethnicity. RESULTS:Women who lived closer to, or had a higher residential density of, Superfund sites reporting contamination of lead or antimony had higher toenail concentrations of the corresponding metals. For example, living ≤5-miles of a lead site was associated with 0.37 ng/g higher lead concentrations (95% CI: 0.18-0.57), and an increase in 1 additional lead-containing site/mile^2 was associated with 2.9 ng/g higher lead concentrations (95% CI: 1.8-4.0). Negligible associations were observed for sites containing arsenic or aluminum for any distance metric. For cadmium, associations were only evident in non-Hispanic Black women living near Superfund sites (N=744) but not non-Hispanic White women (N=2,244, e.g., living ≤5-miles of a cadmium site, βNon-Hispanic Black= 0.69, CI: 0.37-1.0; βNon-Hispanic white = -0.04, CI: -0.3-0.23; p-heterogeneity=0.02). CONCLUSIONS:Increased residential proximity to Superfund sites was associated with higher toenail concentrations of certain metals. Results for cadmium suggest important racial/ethnic differences in exposure that warrant follow-up for potential issues of environmental justice. KEYWORDS: chemical exposures, hazardous waste, heavy metals