Heavy-metals contamination and associated risks in the water-soil-fodder-livestock continuum after long‑term sewage‑water irrigation in peri-urban areas: Evidence from Central India.

Sewage water (SW) use is a common practice for crop production in peri-urban areas globally, especially in arid and semi-arid environments. While it enhances crop yields, it also raises potential ecological and health risks from heavy metals (HMs) contamination, requiring effective management strategies. The study examined the long-term (> 20 years) impact of SW irrigation on HM contamination in the water-soil-fodder-livestock continuum in central India. Samples of SW, groundwater (GW) (pre-monsoon, monsoon, and post-monsoon seasons), soil, fodder, and milk were collected over three years (2018-2021) to evaluate HMs levels, fodder quality, soil pollution indices, and livestock health risks. Findings revealed elevated HMs concentrations in SW, especially during the pre-monsoon. The SW irrigation improved soil fertility (SOC, N, P and K, ~ 14%, ~ 8%, ~ 44% and ~ 12%, respectively) and fodder quality over GW. Soils in Bhopal recorded the highest Cr (51.47 mg kg-1) and Ni (55.35 mg kg-1), while Cd (1.34 mg kg-1), Pb (26.41 mg kg-1) were highest in soils from Varanasi and Kanpur, respectively. Cr and Pb levels exceeded permissible limits. Fodder irrigated with SW showed significantly higher HM accumulation (Cd: ~ 27%, Ni: ~ 44%, Pb: ~ 42%) than with GW. Milk samples exceeded safe limits for Cr, Cd, and Pb, indicating human health risks. Soil indices identified Cd as the primary ecological risk. Although metal transfer factors were < 1.0, Ni and Pb health risk indices surpassed safe thresholds, potentially impairing livestock immunity and productivity. The study underscores the urgent need for regulated SW reuse, farmer education, and policy intervention to ensure sustainable livestock systems.