Mercury and selenium concentrations in the internal organs of toothed whales and dolphins marketed for human consumption in Japan

Small cetaceans (toothed whales odontoceti and dolphins delphinidae) have been traditionally hunted along the coast of Japan and fresh red meat and blubber, as well as boiled internal organs such as liver, kidney, lung and small intestine, are still being sold for human consumption. We surveyed mercury contamination in boiled liver, kidney and lung products marketed in Japan between 1999–2001. The average ±S.D. of total mercury (T–Hg) was 370±525 (range: 7.60 1980, n=26) μg/g in liver, 40.5±48.5 (7.30 95.1, n=15) μg/g in kidney and 42.8±43.8 (2.10 79.6, n=23) μg/g in lung. A high correlation was observed between T–Hg and selenium (Se) concentrations in these organs, supporting the formation of a Hg–Se complex. The formation of a Hg–Se complex probably contribute to the detoxification of Hg for cetaceans and allows a very large accumulation of Hg in livers. The provisional permitted level of T–Hg in marine foods set by the Japanese Ministry of Health and Welfare is 0.4 μg/g, and the provisional permitted weekly intake (PTWI) set by WHO is 5 μg/kg bw/week. The maximal T–Hg detected in boiled liver (1980 μg/g) exceeds the permitted level by approximately 5000 times and the consumption of only 0.15 g of liver exceeds the PTWI of 60 kg of body weight of the consumer, suggesting the possibility of an acute intoxication by T–Hg even after a single consumption of the product.