Bioaccumulation and Human Health Risk Assessment of Arsenic and Chromium Species in Water–Soil–Vegetables System in Lephalale, Limpopo Province, South Africa

Abstract

The accumulation of potentially toxic elements (PTEs) in water, soil and vegetables can pose a severe threat to the respective organisms and lead to human health risks upon exposure. Water, soil and vegetable samples were collected from the Mokolo River and its vicinity. Total concentration quantification and speciation analysis of chromium (Cr) and arsenic (As) were performed using inductively coupled plasma-mass spectrometry (ICP-MS) and high-performance liquid chromatography hyphenated to inductively coupled plasma-mass spectrometry (HPLC-ICP-MS), respectively. The total concentrations of Cr and As were below the maximum permissible levels (MPLs) set by the World Health Organization (WHO) and South Africa’s Department of Water Affairs and Forestry (DWAF) for drinking water. The soil quality guideline value of 64.0 µg/g for Cr was surpassed in most sites and posed a great risk to the vegetables growing in it, whereas the guideline value of 12.0 µg/g for As was surpassed in one sampling site. The observed high concentrations in soil could be linked to the use of fertilizers and atmospheric deposits introduced through coal burning by power stations. In vegetables, the total Cr concentration surpassed the recommended MPL of 0.5 µg/g, rendering the vegetables unsafe for human consumption. Concentrations ranging from 197 to 1180 ng/g and 374 to 17400 ng/g were detected for Cr(VI) and Cr(III), respectively. The consumption of vegetables containing high levels of Cr and As would result in health risks in adults and children as the total hazard quotient (THQ) exceeded 1. The consumption of some vegetables particularly by children could cause serious health risks as the THQ > 10 was observed for some Cr-contaminated vegetables. The incremental lifetime cancer risk (ILCR) threshold of 1 × 10−4 was exceeded, indicating that the overall consumption of vegetables had high cancer risks for adults and children. This study suggests that the consumption of vegetable samples would lead to health risks in the population.