mercury

Heavy metal (liquid at normal temperature) which is a systemic poison that attacks brain, bowels, kidneys, and other body organs. It most severely affects the central nervous system, and children and elderly are most susceptible to its poisoning. Like other heavy metals, mercury is a bioaccumulant that excretes very slowly from the body, collects in body tissue, and climbs up the food chain over time. Its maximum allowable concentration is 0.05 parts per million (PPM).