Assessing heavy metal pollution and livestock health risks in sewage water-irrigated fodder systems: a comprehensive study.

Abstract

Sewage water (SW) irrigation is widely used in developing countries, particularly in arid and semi-arid regions, as a cost-effective method for crop production. However, it poses significant ecological and health risks owing to the presence of heavy metals (HMs), necessitating effective management strategies. This study assesses the impact of mixing SW with groundwater (GW) in various ratios (SW₀: 0%SW, SW₂₅: 25%SW, SW₅₀: 50%SW, SW₇₅: 75%SW, and SW₁₀₀: 100%SW) on fodder productivity, HMs accumulation, and associated risks to livestock in Jhansi, Uttar Pradesh, India. Over three years, SW irrigation improved soil fertility and increased fodder yields by 6-25%. However, it led to elevated levels of HMs in the soil-fodder system. Among the crops studied, oat showed the lowest bioaccumulation compared to cowpea, maize, and berseem, with Pb levels exceeding permissible limits in the SW₁₀₀ treatment. Most tested crops exceeded WHO/FAO limits for HMs, except for Cr and Cd in the SW₂₅ treatment. Pollution index values categorized all crops as "severely" to "heavily polluted", except for oat. Ecological risk indices were low for SW₀ to SW₅₀, with Cd presenting the highest ecological risk (38-69%). The transfer factor (TF) for Cr, Ni, and Cd was <1, while Pb exceeded 1 for all crops. The health risk index (HRI) for Pb was also >1, signaling health risks to immune function, productivity, and reproductive performance in livestock consuming SW-irrigated fodder. A blend of lesser metal-accumulating fodder crops and a 1:3 SW: GW dilution ratio can effectively minimize these risks. Our findings provide baseline information to policymakers, environmentalists, and livestock keepers for formulating strategic mitigation plans to minimize the potential future risks of HMs pollution in the soil-fodder-livestock continuum.