Assessing human health risks and strategies for phytoremediation in soils contaminated with As, Cd, Pb, and Zn by slag disposal.

Soils impacted by metallurgy activities pose serious risks to the health of exposed populations, whether by ingestion of soil or contaminated food and water. The municipality of Santo Amaro, Bahia state, presents the most important case of human lead contamination in Brazil. It occurred because of inadequate slag disposal. The aims of this research were to: (i) determine the environmentally available concentrations and the distribution of As, Cd, Pb, and Zn in soil fractions; (ii) estimate the non-carcinogenic and carcinogenic risks of these elements for children; and (iii) to evaluate the use of corn (Zea mays) and castor bean (Ricinus communis) either for phytoextraction induced by chelating agents or phytostabilization. Our data demonstrated that the environmentally available concentrations of As, Cd, Pb, and Zn in soils surrounding the Pb smelting plant are among the highest that have been reported. Apart from Cd, sequential extraction demonstrated that most metals are in recalcitrant forms in the soil. However, the daily exposure of children to Pb, Zn, Cd, and As exceeded the acceptable daily intake as established by the World Health Organization. Non-carcinogenic risk modeling indicated probable adverse health effects from chronic exposure to soil Pb. The mean estimated time for remediation of the area using phytoextraction was high, ranging from 76 to 259 years; therefore, this is not a viable alternative for remediating soils in the studied area. However, good development in the contaminated soil along with restriction of the metal(oid) translocation to shoots enables castor bean to phytostabilize metal(oid)s. Additionally, castor bean cultivation may be an alternative for an economic return because of biofuel production.