Fish Consumption Advice for Alaskans
Summary The absence of associations between methylmercury exposures and neurodevelopmental effects in the Seychelles Islands study and the potential confounding effect of PCB exposure on the results of the Faroe Islands study cause continued debate among public health officials as to the appropriate study to use as the basis for dietary guidelines for seafood containing methylmercury.
The Alaska Scientific Advisory Committee for Fish Consumption reviewed both studies, and decided that the Seychelles Islands study provides the most appropriate data for determining the human health risks posed by mercury exposure via fish consumption in Alaska. The Seychelles Islander and Alaskan exposure scenarios are comparable, as both populations eat large quantities of ocean fish with minimal influence from local mercury sources, and mercury levels in most fish species encompass a similar range in the two locations. The Committee was also concerned about the uncertainty associated with PCB confounding in the Faroe Island study, especially when Alaska fish have very low PCB levels. Further, potential differences in toxicity of mercury through consumption of pilot whale versus fish (such as the species of mercury present, the relative quantities and types of nutrients such as selenium, relative bioavailability and other issues) add uncertainty to the predictive power of the Faroe Island data. Therefore, the committee concluded that the Seychelles Islands study provided the most appropriate data to develop an Alaska-specific mercury Acceptable Daily Intake for use in fish consumption guideline calculations.
Risk Assessment for Food Consumption Guidelines
Currently, public health scientists and regulators have not reached a consensus on methylmercury dietary exposure guidelines. For example, FDA, the U.S. Agency for Toxic Substances and Disease Registry (ATSDR), and EPA each use different epidemiological studies to derive distinct guidelines (Table 7). FDA bases their dietary intake guidelines for methylmercury on knowledge gained from the acute poisoning episodes in Minamata and Niigata, Japan and Iraq. ATSDR bases their intake guidelines on the Seychelles data while EPA uses Faroe Islands data, and WHO considers both studies.