lead (Pb)

Heavy metal that can cause mental retardation, and increase in the rate of infections and cancer by blunting body's defense mechanisms (the immune system). Lead accumulates in blood, bones, and soft tissue and may result in damage to brain, central and peripheral nervous system, and kidneys. While its suggested threshold is 0.4 part-per-million (ppm) for adults and 0.3 ppm for children, people can exhibit lead poisoning symptoms at 0.2 ppm. Lead intake can occur through water stored in lead pipes, food contaminated by lead in soil, lead-paint flakes, or motor exhaust that contains lead compounds as anti-knocking or performance enhancing additives in gasoline.