The effect of heavy metal contamination on human and animal health in the vicinity of a zinc smelter

Abstract

15A diagnosis of heavy metal poisoning in sheep living on pasture in the vicinity of a zinc smelter 16 was made based on laboratory tests and clinical signs in livestock in the Wumeng mountain area 17 of China. Heavy metal contamination has generated serious harm to the health of local farmers 18 after passing through the food chain. The levels of copper, zinc, cadmium, and lead in irrigation 19 water, soil, forages, and animal tissues were measured in samples taken from within the vicinity of 20 a zinc smelter and control samples. Heavy metal concentrations in foods (corn, rice, and wheat) 21 and human tissues (blood and hair) from local farmers living in affected areas and controls were 22 also determined. Hematological values were determined in human and animal samples. The 23 copper, zinc, cadmium, and lead concentrations in irrigation water, soils, and forages were 24 markedly higher than the levels in healthy pastures. Cadmium and lead concentrations were 25 177.82 and 16.61 times greater in forages than controls, respectively, and 68.71 and 15.66 times 26 greater in soils than controls, respectively. Heavy metal concentrations in food (corn, rice, and 27 wheat) in affected areas were markedly higher than in the control samples. Cadmium and lead 28 concentrations in the tissues of affected sheep were markedly higher than in control animals (P < 29 0.01). Cadmium and lead concentrations in blood and hair samples from affected farmers were 30 markedly higher than the control samples (P < 0.01). The occurrence of anemia in affected 31 persons and animals followed a hypochromic and microcytic pattern. The intake of cadmium and 32 lead was estimated according to herbage ingestion rates. It was found that the levels of cadmium 33 and lead accumulated in sheep through the ingestion of vegetation growing in the sites closest to 34 the zinc smelter were approximately 3.36 mg Cd/kg body wt./day and 38.47 mg Pb/kg body 35 wt./day. This surpassed the fatal dosages for sheep of 1.13 mg Cd/kg body wt/day and 4.42 mg 36 Pb/kg body wt./day. Serum total antioxidant capacity in affected humans and animals was 37 significantly lower than in the controls (P < 0.01). The serum protein parameters in affected 38 humans and animals were significantly reduced (P < 0.01). It was therefore concluded that heavy 39 metal contamination has caused serious harm to sheep in this area. The heavy metal 40 concentrations in food and grain also pose a significant risk to human health in the Chinese 41 Wumeng mountain area. 65 China. The area has extensive heavy metal reserves, characterized by large quantities of ores 66 containing zinc, copper, and lead [2]. A large number of industrial enterprises were established for 67 the purpose of lead, zinc, copper, and polymetallic extraction in the 2010s. After a few years of 68 intensive development, metallurgical industries occupied a very wide area of former pasture and 69 farmland [1]. A number of sheep grazing on pastures in the vicinity died after the smelters went 70 into operation. All of the...