Mercury is a cumulative heavy metal poison that can be absorbed through the skin, lungs, and gastrointestinal tract. Both mercury and its compounds are toxic, with organic compounds being extremely toxic. Mercury exposure can damage the central nervous system, kidneys, and other organs. Heavy or prolonged exposure can cause irreversible brain damage and death, especially in fetuses and infants. Notable cases of mercury poisoning include Minamata disease from contaminated fish in Japan and mercury poisoning from fungicide-treated grain in Iraq, which together caused over 1000 deaths.