Vegetables under siege: the hidden threat of metal contamination in Varanasi’s suburban soils

Abstract

Heavy metal pollution in soils and edible crops poses a critical environmental challenge worldwide. This study examined the contamination of soils by heavy metals in Varanasi region of the Indo-Gangetic plains and assessed its impact on the phenolic, flavonoid, and antioxidant profiles of vegetables. Field investigations were conducted at various sites irrigated with wastewater from industries such as fabric dyeing, battery production, and paint manufacturing. Samples of soil, water, and vegetables including S. oleracea, L. siceraria, M. spicata, A. grain, L. acutangula, A. esculentus, M. charantia, P. vulgaris, and S. melongena were collected from agricultural fields frequently exposed to industrial wastewater. Concentrations of heavy metals (Cu, Zn, Pb, Cr) were measured in soil, water, and vegetables, revealing highest metal pollution index (MPI) in Lohta, followed by Ramnagar, Varuna, Dinapur, Shivpur, and least at Banaras Hindu University (BHU). A positive correlation was observed between metal contamination along with increased phenolic and flavonoid content in vegetables, indicating potential biomarkers for heavy metal-induced stress. Additionally, significant elevations in DPPH, ABTS, and FRAP activities were recorded across contaminated sites, suggesting heightened oxidative stress from increased free radical production. Hierarchical clustering and regression analyses revealed that leafy vegetables (S. oleracea, M. spicata, A. grain) exhibited strongest antioxidant responses. These findings underscore that prolonged consumption of these contaminated vegetables may pose serious health risks due to heavy metal-induced oxidative stress. © The Author(s) under exclusive licence to Society for Plant Research 2025.