Epidemiological evidence on methylmercury neurotoxicity

Methylmercury neurotoxicity has been gradually recorded over several decades. Designs of recent epidemiologic studies have improved to focus their assessments in developmental neurotoxicity. The developing brain, due to rapid physiologic changes and a protective system under development, is particularly vulnerable to the exposure to environmental insults. This chapter aims to systematically review and discuss the state-of-the-art epidemiological studies published up to the present days. We also describe and discuss some of the methodological problems. For example, the uncertainties (confounding) derived from a situation in which an association between an exposure and an outcome is distorted because it is mixed with the effect of a confounding variable. A majority of the studies have demonstrated that methylmercury exposure is neurotoxic to adults and children, but stronger adverse effects would result if negative confounding derived from the nutritional factors of seafood is taken into consideration in the data analyses. The EU and US decision to take preventive measures occurred at a substantial delay following the discovery of these neurotoxic effects.