Metal sources and exposures in the homes of young children living near a mining-impacted Superfund site

Abstract

Children living near hazardous waste sites may be exposed to environmental contaminants, yet few studies have conducted multi-media exposure assessments, including residential environments where children spend most of their time. We sampled yard soil, house dust, and particulate matter with aerodynamic diameter <2.5 in 59 homes of young children near an abandoned mining area and analyzed samples for lead (Pb), zinc (Zn), cadmium (Cd), arsenic (As), and manganese (Mn). In over half of the homes, dust concentrations of Pb, Zn, Cd, and As were higher than those in soil. Proximity to mine waste (chat) piles and the presence of chat in the driveway significantly predicted dust metals levels. Homes with both chat sources had Pb, Zn, Cd, and As dust levels two to three times higher than homes with no known chat sources after controlling for other sources. In contrast, Mn concentrations in dust were consistently lower than in soil and were not associated with chat sources. Mn dust concentrations were predicted by soil concentrations and occupant density. These findings suggest that nearby outdoor sources of metal contaminants from mine waste may migrate indoors. Populations farther away from the mining site may also be exposed if secondary uses of chat are in close proximity to the home.

Figure 1

Cumulative distributions for the ratios of metal concentrations in dust ([metal]dust) to metal concentrations in soil ([metal] soil) across study homes.

Figure 2

Dust metal concentrations by number of chat sources (solid line = median; boxes = interquartile range; whiskers = 5th and 95th percentiles, circles = outliers). Chat sources defined as: (1) living near one or more chat piles and (2) the presence of chat in the residential driveway.