Mercury is a toxic, persistent pollutant that bioaccumulates and biomagnifies through food webs. People are exposed to methyhnercruy mainly through their diet, especially through the consumption of freshwater and marine fish and of other animals that consume fish (e.g., marine mammals). All humans are exposed to low levels of mercury. Dietary patterns can increase exposure to a fish-eating population where the fish and seafood are contaminated with mercury. The primary toxicity targets of mercury and mercury compounds are the nervous system, kidneys, and cardiovascular system. It is generally accepted that developing organ systems are most sensitive to the toxic effects of mercury. The fetal-brain mercury levels appear to be significantly higher than the maternal-blood mercury levels, and the developing central nervous system of the fetus is currently regarded as the main system of concern as it demonstrates the greatest sensitivity. The subpopulation that may be at greater risk for mercury toxicity are those exposed to higher levels of methylmercury due to carnivorous fish, including sharks.