Mercury is a naturally occurring metal having several forms. Methyl mercury and metallic mercury vapors are more harmful than other forms, because more mercury in these forms reaches the brain. Exposure to high levels of metallic, inorganic, or organic mercury can permanently damage the brain, kidneys, and developing fetus. Effects on brain functioning may result in irritability, shyness, tremors, changes in vision or hearing, and memory problems. Short-term exposure to high levels of metallic mercury vapors may cause lung damage, nausea, vomiting, diarrhea, increases in blood pressure or heart rate, skin rashes, and eye irritation.
Thus, the EPA has concluded that mercuric chloride and methyl mercury are possible human carcinogens. Children are more sensitive to mercury than are adults, and mercury in the mother’s body passes to the fetus. Children poisoned by mercury may develop problems in their nervous and digestive systems and suffer from kidney damage.
The EPA has set a limit of 2 parts of mercury per billion parts of drinking water (2 ppb). The Food and Drug Administration (FDA) has set a maximum permissible level of 1 part of methyl mercury in a million parts of seafood (1 ppm).