Heavy metal levels in the dairy production chain in China

The aims of this study were to investigate the heavy metal pollution status and distribution and to analyze the relationships among metal concentrations of different links in the dairy production chain. Chromium (Cr), arsenic (As), cadmium (Cd), lead (Pb), copper (Cu), and zinc (Zn) levels in water, fodder, milk, blood, hair, and feces samples collected from cows from five dairy farms in China were measured. The concentrations of Cr, As, Cd, Pb, Cu, and Zn were 4.61–11.11, 0.06–0.46, 0.17–0.29, 2.84–4.23, 4.11–7.72, and 7.23–19.91 mg/kg in silage; 12.72–40.85, 0.76–2.40, 0.05–0.16, 4.73–9.16, 44.14–78.46, and 4148.51–4845.20 μg/L in milk; 33.59–60.73, 0.09–3.57, 0.29–1.78, 20.14–39.20, 821.34–1007.45, and 2665.10–4929.95 μg/L in blood; 0.59–1.06, 0.02–0.09, 0.08–0.11, 1.70–2.09, 6.45–8.64, and 9.73–1.56 mg/kg in hair; 31.75–296.35, 0.33–5.96, 0.18–0.53, 3.35–9.06, 12.27–41.39, and 56.54–196.34 mg/kg in feces, respectively. The concentrations of heavy metals in hair were higher than those in the other samples and when combined with the results from the silage and tissue samples, we can assume that cow's hair can be used as a biological indicator for heavy metal contamination in the dairy production chain.