What is methylmercury?
When people talk about exposure to ‘mercury’ in fish, they’re actually referring to methylmercury. Methylmercury is formed when mercury gets into water bodies – whether by natural processes or pollution - where it is converted into an organic compound through the actions of bacteria. Fish ingest and absorb methylmercury in minute quantities by feeding on organisms living in water where it is present. Methylmercury has always been in oceans, so minute amounts of methylmercury have been present in every fish ever eaten by humans.
In small amounts, methylmercury is not harmful to humans. Only at very high exposure levels is it toxic. The key healthy concern regarding methylmercury is that it may harm an unborn baby's or young child's developing nervous system if pregnant and nursing women consume large amounts of fish containing high levels of methylmercury.
To safeguard the public, the federal government has put in place very stringent restrictions, including issuing advice for pregnant and nursing women and women who may become pregnant about the best ways to add fish to their diets. This advice is very conservative and builds in a 10-fold safety factor - so that no on is at risk of exposure to the harmful effects of mercury.
Additionally, a twenty year scientific study of mothers and children living in the Seychelles islands off the coast of Madagascar found that moderate fish consumption by mothers is not harmful to the fetus – and the mothers in this study ate 10 times more fish, on average, than mothers in America.