The Urban Environment and Children's Health: Soils as an Integrator of Lead, Zinc, and Cadmium in New Orleans, Louisiana, U.S.A.

Abstract

Soils are evaluated as a diagnostic tool of environmental conditions that influence health. The samples for this study are urban topsoil (0–2.5 cm depth) samples (n=4026) analyzed for Pb, Zn, and Cd by inductively coupled plasma-atomic emission spectrometry (ICP-AES). The parent materials for New Orleans soils are derived from the Mississippi River, and alluvium from the Bonnet Carré Spillway (n=31) serve as control samples for this study. The urban samples were stratified by census tract (n=286). Blood Pb (BL) levels of children ≤6 years were also stratified by census tract and paired with soil Pb (SL) (n=175). A significant association (P=1.2×10−23) was found between median BL and median SL. The association was modeled by BL=3.06+0.33 (SL)0.5 (correlation coefficient=0.69 between the modeled BL and the observed BL and P=3.5×10−22). A median SL threshold (≥310 μg g−1 and <310 μg g−1) for higher metal census tracts (HMCTs) and lower metal census tracts (LMCTs), respectively, represents median BL exposures above and below 9 μg dL−1. HMCTs and LMCTs were characterized by demographic and socioeconomic data. HMCTs are more likely (P=4.5×10−6) inhabited by Blacks than by Whites. Of 13,803 children ≤6 years in HMCTs, 75% are Black and 22% are White, with other making up the remaining 3%. In LMCTs, the Black to White children ratio is 50:50. In HMCTs, socioeconomic indicators for Blacks are depressed compared to Whites. Zn and Cd are potentially phytotoxic in HMCTs. Children exhibit a steep rise in BL at SL <100 μg g−1, and empirically, a safe SL for most children is around 80 μg g−1. SL is a useful diagnostic tool, and curtailing SL may complement primary Pb prevention for children.