methylmercury

Methylmercury is an organic form of mercury that accumulates in living organisms, particularly fish.

It builds up in the food chain through a process called bioaccumulation—small fish absorb it, larger fish eat them, and concentrations increase at each level.

Human exposure comes mainly from eating contaminated seafood.

Methylmercury is a potent neurotoxin, especially dangerous to developing fetuses and young children: Pregnant women are advised to limit consumption of high-mercury fish like tuna and swordfish.