Risk assessment of potentially toxic elements in areas with arsenic anomalies

Abstract

Agriculture and mining are important activities in the global economic landscape. However, they can cause adverse impacts on the environment and human health by mobilizing potentially toxic elements (PTEs) into soils and waters. Among the main PTEs, arsenic (As) and lead (Pb) have a high potential to cause health damage. However, determining only the pseudo-total contents of these PTEs in soils may be inadequate to predict real adverse effects, as bioavailability can be influenced by various physical and chemical properties of the soil. Thus, the objective of this study was to evaluate the environmental and human health risks in soils with abnormal levels of As in irrigated agricultural areas of Paracatu (MG), Brazil. Additionally, we evaluated the potential health risks of As and Pb in soils sampled from two contrasting areas with different origins and land uses, one in agricultural areas of Paracatu (MG), Brazil, and another in areas of an abandoned gold mine in Marmora and Lake (ON), Canada, using oral bioaccessibility tests of As and Pb developed by the Solubility Bioaccessibility Research Consortium (SBRC). In Brazil, soil and plant tissue samples were collected from ten agricultural and reference areas. In Canada, soil samples were collected from ten areas of an abandoned gold mine and its adjacent areas. In general, the pseudo-total contents of As and Pb in soils exceeded the regulatory soil quality limits of Brazil and Canada. However, the levels of As in plant tissues in the agricultural area were below the detection limit. The pseudo-total levels of As in agricultural soils did not differ between soil depths, indicating that the source of As in these soils is likely natural. Overall, the bioaccessibility of As and Pb in soils was low, with values of 5.57% for AsIVBA and 17.19% for PbIVBA in agricultural soils and 31.53% for AsIVBA and 20.58% for PbIVBA in mine soils. There was a significant positive correlation between the bioaccessible levels of As and Pb and some soil properties, mainly total and extractable iron (Fe) contents. The bioaccessible levels of As and Pb, by the SBRC method, were used in risk assessment calculations for accidental soil ingestion. For agricultural areas, in general, occupational risks are not concerning. However, for the abandoned mine areas, there was a high level of carcinogenic risk of As for adults and children. In both areas, there was no risk associated with Pb exposure. We concluded that assessment based only on the total levels of As and Pb is not sufficient to predict adverse health effects, overestimating chronic exposure to these elements. Therefore, we suggest a correction factor of 10% bioaccessibility of As for Brazilian agricultural soils with high Fe content. This study provides valuable insights for localized risk assessments and guides future research on the oral bioavailability of As and Pb.