Soil heavy metal contamination in residential neighborhoods in post-industrial cities and its potential human exposure risk

This study assessed the extent of potential human risk to heavy metal exposure by comparing concentrations of arsenic (As), cadmium (Cd), chromium (Cr), lead (Pb) and zinc (Zn) in soil in 43 vacant lots in two low income neighborhoods, Hough (Cleveland, Cuyahoga County, Ohio) and Weinland Park (Columbus, Franklin County, Ohio) in USA to the US Environmental Protection Agency (EPA)'s Soil Screening Levels (SSLs) and to regional background concentrations. At least one soil sample in all the lots in Weinland Park and 27 out of 28 (96%) of the lots in Hough exceeded the natural background concentration of Pb in Franklin (14 to 25 mg/kg soil) and Cuyahoga (56 to 136 mg/kg soil) counties, respectively. When compared to the USEPA's SSL for Pb for human ingestion of soil, soil from only 1 out of 15 (6.6%) lots in Weinland Park and 15 out of 28 (54%) in Hough neighborhood exceeded the SSL of 400 mg Pb/kg soil. All sites in both neighborhoods exceeded the SSL for As (0.4 mg/kg soil); however only 1 lot (6.6%) in Weinland Park and 3 (11%) in Hough exceeded the background concentrations of As in Franklin (9 to 33 mg/kg soil) and Cuyahoga (5 to 20 mg/kg soil) counties. Thirteen (86%) lots in Weinland Park and 25 (89%) in Hough had soil Zn concentration higher than the background in Franklin County (71 to 177 mg/kg soil) and Cuyahoga County (56 to 137 mg/kg soil) respectively, however they were all within the SSL of 23,000 mg Zn/kg soil. Significant correlations were observed within metals, soil properties, and between metals and soil properties including texture, moisture, pH, organic matter and active carbon suggesting unique associations in the two neighborhoods. Results indicate that Pb is a metal of concern in 54% of the vacant lots in Hough neighborhood. The study highlights the need for comparing vacant lot heavy metal concentrations to both USEPA's SSLs and natural background concentrations in the area for establishing safety of a lot prior to its use for urban agriculture.