Estimation of Daily Mercury Intake from Seafood in Japanese Women: Akita Cross-sectional Study

We estimated daily mercury intakes from seafood in 154 mothers residing in several cities and towns in Akita, Japan, to address the relationships between the reference dose (RfD of 0.1 microg/kg body weight per day, derived by US EPA) and daily mercury intakes, combined with hair mercury levels. The frequency and volume of seafood ingested by them were examined using a food frequency questionnaire (FFQ) with 25 kinds of full-scale pictures including fish and shellfish items. Hair mercury concentrations in the mothers were also determined. The geometric means in the mothers were 15.3 (2.65-48.4) microg/day for daily mercury intakes from seafood, calculated on the basis of the references on mercury contents, and 1.73 (0.49-5.82) microg/g for hair mercury concentrations. The daily mercury intake was significantly correlated with hair mercury concentrations (Spearman rank correlation coefficient rs=0.335, p<0.001). No significant differences in mercury intakes were found either between mothers residing in fishing and non-fishing areas or between those in cities and towns (p>0.05). Assuming the methylmercury content rate of 75% in seafood mercury and body weight of 55 kg, the mothers were estimated to ingest methylmercury of 0.21 microg/kg body weight per day. It is suggested that daily mercury intakes, calculated by the FFQ, reflect hair mercury levels, and there is no interregional difference in the daily mercury intake unless any special circumstance exists. Daily methylmercury intake in more than 90% of Japanese women may exceed the RfD, and it therefore seems to be far from the present state of Japanese dietary lives.