Methylmercury in fish species used in preparing sashimi : a case study in Brazil.

The objective of this work was to determine the organic and total mercury contents in twelve fish species used in preparing sashimi in Japanese restaurants and estimate the exposure to organic mercury due to the consumption of this food. The mercury species were quantified by atomic absorption with thermal decomposition and amalgamation. Total mercury was analyzed directly, whereas organic mercury was quantified after extraction with toluene in an acid medium using a microwave assisted system. Needlefish and tuna showed the highest levels of mercury species and salmon and mullet the lowest levels. The mean ratios between MeHg?/total Hg were 93% and 87% for sandperch and octopus, respectively, indicating that the most toxic form (organic Hg) predominates in these species. Exposure to methylmercury was estimated based on the PTWI and the results showed that the ingestion of 2 portions of needlefish and tuna exceeded the values established by 100%