Human health risks and bioaccessibility of As and Pb in urban soils in the mining district of Riotinto (SW Spain)

Abstract

Urban soils in the mining district of Riotinto in SW Spain contain high levels of As and Pb, in many cases surpassing the threshold values of polluted soils. Up to 84% of the soils have a Contamination Factor higher than 1 for As and 70 % for Pb, with maximum values of 432 for As and 373 for Pb. Natural soil forming processes from mineralized bedrock in the vicinity of the ore deposits, that are currently being exploited, influence the soil chemistry (Vázquez-Arias et al., 2023). On the contrary, calcareous aggregate pavements used as artificial soils covering public parks do not generally present risk for As and Pb. However, these soils may be influenced by deposition of atmospheric pollution derived from the mining activities (Vázquez-Arias et al., 2023). The bioaccessibility tests simulating gastric fluids (using <150 µm soil fraction), exhibit low percentages for As in natural soils in comparison to the total concentration in the same fraction (average <18%) and in the artificial soils (<6%), whereas for Pb the bioaccessible portion ranged from 20 to 48% in natural soils, whereas it was insignificant for artificial soils. According to human health risk assessment modelling (using U.S.EPA protocols), 18% of the soils present risk of As toxicity for children, and merely one sample presents toxicity risk for adults, as well as, carcinogenic risk for both children and adults. Lead does not present human health risks except for one sample with toxicity risk for children. We recommend covering the natural soils of the public parks, presenting potential human health risks, with calcareous aggregates as a cost-effective remediation measure. This material will act as a liming agent and will prevent the dusting of and the direct contact with polluted soils, minimizing human exposure via inhalation, ingestion and dermal contact and potential health risks.   Acknowledgment This work has been financed by the EMC21_00056 project granted by the Council of University, Research and Innovation of the Regional Government of Andalusia, Spain.