Dietary exposure of Hong Kong secondary school students to total mercury and methylmercury from fish intake.

Fish is the main source of dietary exposure to methylmercury (MeHg), which is a public health concern owing to its potential neurotoxicity. To evaluate the public health risk, this study estimated the total mercury (tHg) and MeHg exposure from fish intake in Hong Kong secondary school students. Median tHg and MeHg concentrations of 280 samples purchased from different commercial outlets (covering 89 species of whole fish and three types of canned tuna), together with the local food consumption data of secondary school students obtained by semi-quantitative food frequency questionnaire in 2000, were used to estimate dietary exposure from fish intake for the average and high consumer (95th percentile exposure). For tHg, the median concentration was 63 µg kg(-1) (range 3-1370 µg kg(-1)) and estimated exposures ranged 0.5-0.6 µg kg(-1) body weight (bw) week(-1) for an average consumer and 1.6-1.9 µg kg(-1) bw week(-1) for a high consumer. For MeHg, median concentration was 48 µg kg(-1) (range 3-1010 µg kg(-1)) and estimated dietary exposures were 0.4-0.5 µg kg(-1) bw week(-1) for an average consumer and 1.2-1.4 µg kg(-1) bw week(-1) for a high consumer. These values are below the respective provisional tolerable weekly intake (PTWI) established by the Joint Food and Agriculture Organization/World Health Organization Expert Committee on Food Additives (JECFA). The health risk is greater for high consumers since MeHg exposures may approach or exceed the PTWI when other dietary sources are taken into account.