Associations between soil lead concentrations and populations by race/ethnicity and income-to-poverty ratio in urban and rural areas

Abstract

Lead (Pb) is a well-studied environmental contaminant that has many negative health effects, especially for children. Both racial/ethnic and income disparities have been documented with respect to exposure to Pb in soils. The objectives of this study were to assess whether soil Pb concentrations in rural and urban areas of South Carolina USA, previously identified as having clusters of intellectual disabilities (ID) in children, were positively associated with populations of minority and low-income individuals and children (≤ 6 years of age). Surface soils from two rural and two urban areas with identified clusters of ID were analyzed for Pb and concentrations were spatially interpolated using inverse distance weighted analysis. Population race/ethnicity and income-to-poverty ratio (ITPR) from United States Census 2000 block group data were aerially interpolated by block group within each area. Urban areas had significantly higher concentrations of Pb than rural areas. Significant positive associations between black, non-Hispanic Latino, individuals and children ≤ 6 years of age and mean estimated Pb concentrations were observed in both urban (r = 0.38, p = 0.0007) and rural (r = 0.53, p = 0.04) areas. Significant positive associations also were observed between individuals and children with an ITPR < 1.00 and Pb concentrations, though primarily in urban areas. Racial/ethnic minorities and low ITPR individuals, including children, may be at elevated risk for exposure to Pb in soils.

Fig. 1. Map of the contiguous United States and location of the state of South Carolina

Fig. 2. Estimated soil lead (Pb) concentrations and identified block groups within sampling areas where >50 % of the population was racial/ethnic minority, >50 % of the population has income-to-poverty ratio (ITPR) < 1.00, and where the mean estimated Pb concentration was >400 mg kg⁻¹ (the EPA residential soil limit or RSL) for urban Area 4 (a) and Area 5 (b), and rural Area 6 (c) and Area 27 (d)

Fig. 3. Population frequency distribution by race/ethnicity for urban Areas 4 and 5 and rural Areas 6 and 27

Fig. 4. Population frequency distribution by income-to-poverty ratio (ITPR) range (with average 1999 median income) for urban Areas 4 and 5 and rural Areas 6 and 27