Survey of Total Mercury Content in Fishery Products

The total mercury content in 112 fishery products, purchased from Osaka city during 2013-2018, was measured using a heating vaporization mercury analyzer. The average total mercury content in all tuna processed products was found out to be 0.115 mu g/g (median=0.070 mu g/g). Notably, albacore tuna exhibited the highest mercury content with an average concentration of 0.301 mu g/g (median= 0.296 mu g/g). The total mercury concentration of the fishery products, except processed tuna and Kezuribushi (comprising shavings of dried and smoked mackerel, sardine, as well as horse mackerel), was generally low (<0.1 mu g/g). The provisional tolerable weekly intake (PTWI) for mercury as set by the Joint FAO/WHO Expert Committee on Food Additives is 4.0 mu g/kg body weight/week. On an average, for Japanese diet, the total weekly mercury intake from fishery products for a person weighing 50 kg was estimated to be 0.13 mu g/kg body weight/week, which was 3.3% of the PTWI. These values indicate that it was not a problem to consume fishery products normally. However, albacore tuna cans have a relatively high total mercury concentration; thus, pregnant women consuming them daily may exceed the tolerable weekly intake of methylmercury (2 mu g/kg body weight/week) as set by the Food Safety Commission of Japan.