High mercury levels in Doochi, a local shark skin and intestine dish of the Eastern coast of Korea.

Doochi, a traditional Korean dish made from boiled shark skin and intestine, may be a source of mercury exposure. In 2013, total mercury was measured in untreated fragments of boiled shark skin from 32 purchased servings of Doochi and of 32 raw skins sold as its ingredient. In 2022, another serving was separated into the skin and intestine, each fully homogenized and analyzed in triplicate at an accredited laboratory. The geometric mean was 0.349 µg/g in the boiled skin fragments and 0.122 and 0.137 µg/g in the outer and inner layers of the raw skin. After homogenization, the boiled skin contained 2.667-2.882 µg/g and the intestine 0.295-0.333 µg/g. The homogenized boiled skin exceeded the European total mercury limit of 1.0 µg/g for shark, and its estimated methylmercury concentration exceeded the Korean limit of 1.0 µg/g for deep-sea fish. Fragment concentrations varied 167-fold and were more dispersed than in raw skin (Levene's test, p < 0.001). Hazard quotients against the methylmercury reference dose were 0.15 to 0.57 under traditional ceremonial consumption, and exceeded 1 at 10 to 36 servings per year depending on the assumptions; the corresponding intakes were 7 to 25% of the provisional tolerable weekly intake under that pattern and reached it at 22 to 81 servings per year. Under the assumptions of this analysis, exposure at the traditional consumption frequency was below the reference dose, but frequency warrants attention as the dish becomes more widely available, particularly for individuals of lower body weight.