Bioaccumulation and transfer of zinc in soil plant and animal system: a health risk assessment for the grazing animals.

Heavy metals pollution has thorough worldwide apprehensions due to the instantaneous growth of industries. Farming regions are irrigated mainly with wastewater which contains both municipal and industrial emancipations. Keeping in view the above scenario, a study was designed in which three sites irrigated with ground, canal, and municipal wastewater in the District Jhang were selected to determine the zinc accumulation and its transfer in the soil, plant, and animal food chain. Zinc concentration was ranged as 18.85-35.59mg/kg in the soil, 26.42-42.67 mg/kg in the forage, and 0.982-2.85mg/kg in the animal samples. Investigated zinc concentration in soil and forages was found to be within the recommended WHO/FAO limits, but blood samples exceed the standards of NRC (2007). The maximum level of pollution load index (0.427-0.805mg/kg) and enrichment factor (0.373-0.894 mg/kg) for zinc was noticed upon wastewater irrigation. Daily intake (0.039 to 0.082 mg/kg/day) and health risk index (0.130 to 0.275 mg/kg/day) of zinc metal was higher in the buffaloes that feed on wastewater-irrigated forages. Bio-concentration factor (0.840 to 2.01mg/kg) for soil-forage was >1 which represents that these plants accumulated the zinc concentration into their tissues and raised health issues in grazing animals on consumption of wastewater-contaminated forages. As animal-derived products are part of human food, then zinc toxicity prevailed in livestock tissues ultimately affects the human food chain. Overall, findings of this study concluded that animal herds should be monitored periodically to devise preventive measures regarding the toxic level of heavy metals availability to livestock.