Uptake of cadmium from Pacific oysters (Crassostrea gigas) in British Columbia oyster growers

Background Pacific oysters along the North American coast from Washington to Alaska contain concentrations of cadmium (Cd) that are high by comparison with Atlantic oysters, frequently exceeding 2 μg/g wet weight, but it is unclear whether this Cd is absorbed by consumers. Objectives To determine the effect of oyster consumption on Cd in blood and urine among a group with high oyster consumption. Methods Sixty-one non-smoking oyster growers and family members with a mean age of 47.3±7.6 years (range 33–64) were interviewed by telephone to assess their oyster consumption and other sources of Cd exposure at present and 5 years prior to the start of oyster farming. Their blood and urine Cd concentrations were measured. Results The geometric mean Cd concentration in blood was 0.83 μg/L and in urine was 0.76 μg/g creatinine. Thirty-six percent of participants had urinary Cd levels above 1 μg/g creatinine and 5% were above 2 μg/g creatinine. Recent (last 12 months) and long-term oyster consumptions were positive predictors of blood Cd but did not directly predict urinary Cd. The optimal model for predicting the variance in blood Cd included recent intake of oyster-derived Cd, serum iron concentration and recent ketchup consumption (R2=0.34, p=0.00004), with the latter two variables showing a protective effect. The factors found to predict urinary Cd were blood Cd concentration and duration of oyster farming. A rise in blood Cd was observed after 12 years of farming oysters, likely caused by higher consumption of oysters during this period. Conclusions Oyster-derived Cd is bioavailable and affects body stores of the metal.