Assessment of potential health risks due to heavy metals through vegetable consumption in a tropical area irrigated by treated wastewater

Abstract

Consumption of wastewater-irrigated vegetables is a common practice in developing countries including India. The wastewater irrigation gradually raises the contents of heavy metals in soils and vegetables. The consumption of heavy metal-rich vegetables may cause serious risk to the human health. Therefore, quantification of heavy metals in vegetables collected from wastewater-irrigated field is needed as proportion of farmers using wastewater for irrigation is increasing due to scarcity of water. The aim of the present study was to assess the heavy metal accumulation and the potential human health risks associated with consumption of contaminated vegetables irrigated with waste (WWT) and mixed wastewater (MWWT), grown in an agricultural area of Bhagwanpur, near Banaras Hindu University, Varanasi, India. Seven common vegetables growing at two differentially irrigated areas (WWT and MWWT) were considered for the study. At each site, three samples, each from water, soil and different vegetables, were taken. The samples after digestion were analysed for heavy metal contents using atomic absorption spectrophotometer. Heavy metal contents in soils, vegetables, transfer factor (TF) from soil to vegetables, metal pollution index (MPI) and their health risk in form of target hazard quotients (THQs) were calculated. Results showed significantly higher contents of heavy metals in water, soil and vegetable at WWT than MWWT. The TF value of Cd was notably greater in WWT compared to the MWWT. The values of THQ in children and adults were >1 for Pb and Cd in case of all vegetables at both WWT and MWWT. Among the vegetables, MPI was highest for B. vulgaris followed by B. botrytis, B. capitata, R. sativus, B. nigra, A. sativum and S. tuberosum. THQ for both categories were mostly higher for WWT compared at MWWT, suggesting a greater health risk to local residents from vegetable of the former than latter site. The present study suggests regular monitoring of water quality prior to discharge for irrigation uses and also points out to adopt better wastewater management strategies for proper utilization and disposal of wastewater.