Antimony is a silvery-white, naturally occurring element found in the Earth's crust. It is relatively rare but has been used in metal alloys and can help prevent fires when used in textiles. Rats have contracted lung cancer from breathing very high quantities of antimony, but the substance is not a human carcinogen. When ingested with water, antimony has affected cholesterol levels in rats. The substance is found in water supplies only near mining sites, said EPA toxicologist Bob Benson.