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

A diagnosis of heavy metal poisoning in sheep living on pasture in the vicinity of a zinc smelter was made based on laboratory tests and clinical signs in livestock in the Wumeng mountain area of China. Heavy metal contamination has generated serious harm to the health of local farmers after passing through the food chain. The levels of copper, zinc, cadmium, and lead in irrigation water, soil, forages, and animal tissues were measured in samples taken from within the vicinity of a zinc smelter and control samples. Heavy metal concentrations in foods (corn, rice, and wheat) and human tissues (blood and hair) from local farmers living in affected areas and controls were also determined. Hematological values were determined in human and animal samples. The copper, zinc, cadmium, and lead concentrations in irrigation water, soils, and forages were markedly higher than the levels in healthy pastures. Cadmium and lead concentrations were 177.82 and 16.61 times greater in forages than controls, respectively, and 68.71 and 15.66 times greater in soils than controls, respectively. Heavy metal concentrations in food (corn, rice, and wheat) in affected areas were markedly higher than in the control samples. Cadmium and lead concentrations in the tissues of affected sheep were markedly higher than in control animals (P< 0.01). Cadmium and lead concentrations in blood and hair samples from affected farmers were markedly higher than the control samples (P < 0.01). The occurrence of anemia in affected persons and animals followed a hypochromic and microcytic pattern. The intake of cadmium and lead was estimated according to herbage ingestion rates. It was found that the levels of cadmium and lead accumulated in sheep through the ingestion of vegetation growing in the sites closest to the zinc smelter were approximately 3.36 mg Cd/kg body wt./day and 38.47 mg Pb/kg body wt./day. This surpassed the fatal dosages for sheep of 1.13 mg Cd/kg body wt/day and 4.42 mg Pb/kg body wt./day. Serum total antioxidant capacity in affected humans and animals was significantly lower than in the controls (P < 0.01). The serum protein parameters in affected humans and animals were significantly reduced (P < 0.01). It was therefore concluded that heavy metal contamination has caused serious harm to sheep in this area. The heavy metal concentrations in food and grain also pose a significant risk to human health in the Chinese Wumeng mountain area.


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The Wumeng mountain area is located in the Yunnan-Guizhou Plateau of China, where the 47 three provinces of Guizhou, Yunnan, and Sichuan meet, and is an important pasture land for sheep 48 [1]. Sheep farming is vital to the production system in the Wumeng mountain area. The animals 49 provide meat, wool, and hides for local people [2]. During the past 10 years, lead, cadmium, 50 copper, and zinc concentrations in air, water, soils, forages, and foods (corn, rice, and wheat) have 51 been increasing in the region. In terms of the potential adverse effects on human and animal health, 52 lead, cadmium, and arsenic have caused most concern [3-4], because they are readily transferred 53 though food-chains and are not known to serve any essential biological function [5]. Industrial

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The Wumeng mountain area is also an important production base of non-ferrous metals in Selected humans and animals ground by a mortar, passed through a 0.5 mm sieve and then stored in a desiccator over silica gel 140 (Fig 2). Samples of water, soil, forage, and food for use as controls were collected from Dushan 141 County on the Yunnan-Guizhou Plateau. Inc., Chicago, IL, USA), and presented in the form of mean ± standard error (SE). Significant 178 differences between groups were assessed using a student's t test, with least significant differences 179 of 1% (P < 0.01) or 5% (P < 0.05).

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It was found that heavy metal concentrations clearly decreased with increasing distance from 182 the zinc smelter (Fig 3−5). The heavy metal concentrations (lead, cadmium, copper, and zinc) in 183 irrigation water, soils, forages, and foods (corn, rice, and wheat) in affected pastures were 184 markedly higher than those in the control area (P < 0.01; Table 1    superoxide dismutase, and glutathione peroxidase activities were significantly reduced (P < 0.01).

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Serum total antioxidant capacity levels in affected humans and animals were significantly lower 247 than those in the controls (P < 0.01). Malondialdehyde levels in serum from affected humans and 248 animals were significantly higher than those in the controls. Serum protein parameters in affected 249 humans and animals are given in Table 9. Compared with healthy humans and animals, the total 250 protein, albumin, α-globulin, β-globulin, and γ-globulin levels were significantly reduced (P < 251 0.01).
252 253   in the vicinity of zinc smelters and are the primary livestock species exposed to heavy metal 312 contamination in this area. Therefore, a determination of the cadmium, lead, copper, and zinc 313 concentrations in domestic animals in this area is important for assessing the potential effects of 314 pollutants on livestock and for quantifying contaminant uptake by humans.

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Lead, cadmium, copper, and zinc concentrations in blood and hair samples from the local 316 farmers in the affected area were also significantly higher than those in the controls (P < 0.01).

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Hypochromic microcytic anemia was also evident in affected humans. The levels of superoxide 318 dismutase, glutathione peroxidase, and total antioxidant capacity are given in