Bioaccessibility and human exposure to metals in urban soils (Huelva, SW Spain): evaluation by in vitro gastric extraction.

The main purpose of this study was to assess the human health risk of heavy metals in the urban-peri-urban soils from Huelva Township. The soils present high concentrations of potentially toxic elements well beyond the regional screening soil concentration. A site-specific health risk assessment of exposure (oral ingestion, oral inhalation and dermal contact) was conducted according to the regulatory normative. To reduce the uncertainty derived from soil characteristics, bioaccessibility and predicted bioavailability data were included in the assessment. Thereby, in order to evaluate the oral bioaccessibility, a simulation of the gastric condition (pH and T) was applied dissolving the samples in a solution of HCl and 0.4 M glycine. Soils located in industrial areas present higher bioaccessibility than those associated with urban or other uses. The adjusted-relative bioaccessibility total carcinogenic risk for As exceeded the regulatory level in all samples (except samples 7 and 184) indicating that children are more vulnerable, while no detrimental health effects are expected for Pb (except in sample 76, a "greenway" recreational area). The adjusted hazard index for non-carcinogenic effects also overpassed the threshold values in practically all possible scenarios for an adult resident working in Huelva, as well as for a child living and playing in the urban/recreational areas. The main pollutant contributions were related to As and Pb. For this reason, the reported soils exceeding the regulatory levels should be classified as polluted and, therefore, this study should be helpful to initiate necessary soil management interventions to avoid the human health risk.