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Cadmium (Cd) concentrations in 1663 liver, 1779 kidney and 2526 muscle samples were measured in a residue survey organised by the Australian Bureau of Rural Science at meatworks throughout Australia. Cadmium concentrations in livers and kidneys were also determined in sheep ranging in age from newly born to 112 months of age which had been grazed throughout life at high or low stocking rates on an improved pasture dressed annually with superphosphate. Concentrations of Cd in the residue survey averaged (with median) 0.30 (0.11), 0.96 (0.28) and 0.03 (0.01) mg/kg freshweight in ovine liver, kidney and muscle respectively; the corresponding values in cattle were 0.18 (0.08), 0.65 (0.24) and 0.03 (0.01) mg/kg. Concentrations in liver and kidney were greater in older than in younger animals, at high than at low stocking rates, and in South and Western Australia than in other States. Cadmium concentrations increase with age because ruminants are born with a low Cd burden, and much of the Cd ingested and absorbed thereafter is retained as Cd-metallothionein in the liver and kidney. It is postulated that differences in Cd levels between geographical regions, species and stocking rate are partially due to the consumption of soil that had been fertilised with superphosphate containing Cd. Hepatic and renal Cd concentrations were highly correlated and were assumed to reflect Cd intake; correlations with copper concentrations were generally small. Eight per cent of kidneys exceeded maximum permissible Cd concentrations for human consumption (2.5 mg/kg), but only 2% of liver and 1% of muscle samples exceeded the statutory maxima (1.25 and 0.2 mg/kg respectively). |
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