Lead

Lead is a dense, metallic chemical element (atomic number 82, atomic symbol Pb from the Latin plumbum) that has numerous industrial uses and is common in the environment. It is fairly soft and easy to mold, resists corrosion well, and is common in applications where weight is not an issue. It is used in automotive batteries, pigments, drainage plumbing and ammunition. It is also used as a radiation shield as one inch of lead provides as much protection against radiation as a foot of solid concrete. 
However, lead and its compounds are all poisonous to living things and are not found naturally in the body. Until the 1970s, lead pigments were commonly used in house paint and children who eat paint chips (which have a slightly sweet taste) can often suffer serious neurological damage. It affects the brain, nerves and blood as it interferes with the production of heme and the body's natural chemical reactions which normally use calcium. Many so called folk remedies are also made of lead salts. Soil can also be contaminated by lead often by tetraethyl lead used as a gasoline additive, but soil can often be contaminated by natural lead deposits. 
Lead poisoning usually causes neurological symptoms such as weakness of the extremities and loss of mental function. It can also affect the kidneys. It is usually treated with chelation therapy.
Lead at Wikipedia
Category:Diseases
Category:Chemistry