Recent advances in recognition of low-level methylmercury poisoning

Clinically evident neurologic damage from methylmercury exposure was well described following poisoning episodes in Japan and Iraq several decades ago. Paresthesias have been considered to be an early effect; however, additional data raise questions about whether this is the most sensitive adverse effect among adults. Fetuses are considered the most sensitive subpopulation because of the vulnerability of the developing nervous system. Over the past 5 years questions have been raised about what is an appropriate level of exposure for sensitive groups. A recent evaluation by a committee for the US National Research Council found that 0.1 microg/kg body weight per day is a scientifically justified level of methylmercury exposure for maternal-fetal pairs. The conclusions of this report and other issues are discussed in the present review. Because of anthropogenic release of mercury into the environment, methylmercury exposure from fish consumption is a pathway that is of increasing concern.