From dumping grounds to farmlands: Toxic metal contamination and food safety risks in India's reclaimed agricultural lands.

Rapid urbanisation and industrialisation have substantially reduced cultivable land worldwide. To meet increasing food demand, dumping grounds are increasingly being reclaimed for agriculture. The distribution and temporal pollution trends of eight trace and toxic metals (Cr, Mn, Ni, Cu, Zn, Cd, Hg, and Pb) were assessed in reclaimed farmland soils of Dhapa (East Kolkata Wetlands Ramsar site, India). Tissue-specific metal transfer, bioaccumulation of Cd, Hg, and Pb in vegetables, dietary exposure, and probabilistic health risk assessment were integrated to evaluate farming safety on reclaimed landfill soils. A progressive increase in the PLI from ~ 5.8 to 13.6 was observed over the past few decades, indicating a deterioration in soil quality in the study area. The soil to root metal transfer factor decreased as Cd > Pb > Hg, while their root to shoot transfer factor ranked as Hg = Cd > Pb, and bioaccumulation efficiency decreased as Cd (~ 0.8) > Hg (~ 0.03) > Pb (~ 0.02). Metal accumulation in edible tissues resulted in elevated dietary exposure and health risks. The calculated combined HI was 1.0 for adults and 4.5 for children. The TCR was 1.8 × 10-3 for adults and 6.5 × 10-3 for children, substantially exceeding the acceptable risk range (10-6-10-4). This study proposed a bioaccumulation-based classification of vegetables, enabling selection of low-bioaccumulator crops for safer cultivation on contaminated soils, thereby minimizing dietary metal exposure. Future research should integrate species-specific metal uptake mechanisms into crop selection strategies to promote safer agriculture on reclaimed landfill soils.