Surface soil concentrations of arsenic, barium and lead and associations with land cover and population race/ethnicity and socioeconomic status

Background Heavy metals are ubiquitous and long-lived in soils, and expensive to measure. They are associated with a host of negative health outcomes, and minority and low socioeconomic status (SES) individuals are disproportionately at risk for exposure. Our objectives were to examine if Census measures of race/ethnicity and SES were associated with different types of Anderson land use codes, and if codes could proxy for surface soil concentrations of arsenic (As), barium (Ba), and lead (Pb).

Methods Surface soil in five urban and five rural areas were sampled for As, Ba, and Pb and concentrations were spatially interpolated and aggregated to the Census 2000 block groups within each area. Weighted percentages of land use codes by block group, and percentages of the block group population that were non-Hispanic (NH) black were identified. Comparisons between areas and regression models were used with metals and land cover as dependent variables.   

Results Urban areas had higher percentages of urban/built up land cover and significantly higher As and Pb than rural sampling areas. Barium concentrations and population measures were not a function of land use. Lead was positively associated with commercial land use (p=0.01) and As with industrial land use (p=0.002). Lead was consistently positively associated with higher percentages in NH blacks in five sampling areas (all p≤0.04).

Conclusions Anderson land cover categories were a potential proxy for soil Pb and As concentrations. The consistency of the association between soil Pb and percentage of the block group population that identified as NH black has important public health implications. While these results are promising, land cover codes from more recent remote sensing data are needed, and other soil contaminants should be examined as associations were metal-dependent.