Lead.

Lead is a chemical element in the carbon group with symbol Pb (derived from the Latin: plumbum) and has the atomic number 82. It is a soft and malleable metal and has a bluish-white colour after being freshly cut, but soon tarnishes to a dull grey colour when exposed to air. It has a shiny chrome-silver luster when it is melted into a liquid.  Lead rarely occurs in its elemental form in the wild. It is typically found in ores along with copper, and in smaller quantities with zinc and silver.

Lead is used in building construction, lead-acid batteries, bullets and shot, weights, as part of solders, pewters, fusible alloys, and as a radiation shield.  It was also commonly used in pipes for many hundreds of years, giving rise to the English words, "plumbing", "plumber", "plumb", and "plumb-bob" -- words derived from the same Latin root with lead.

If ingested, lead is poisonous to animals, including humans. It damages the nervous system and causes brain disorders. Excessive lead also causes blood disorders in mammals. Like the element mercury, another heavy metal, lead is a neurotoxin that accumulates both in soft tissues and the bones. Lead poisoning has been documented from ancient Rome, ancient Greece, and ancient China.

Lead pigments were used in lead paint for white as well as yellow, orange, and red. Most uses have been discontinued due of the dangers of lead poisoning. Lead chromate is still in industrial use. Lead carbonate (white) is the traditional pigment for the priming medium for oil painting, but it has been largely displaced by the zinc and titanium oxide pigments. It was also quickly replaced in water-based painting mediums. Lead carbonate white was used by the Japanese geisha and in the West for face-whitening make-up, which was detrimental to health.

Tetraethyllead was used in leaded fuels to reduce engine knocking, but this practice has been phased out across many countries of the world in efforts to reduce toxic pollution that affected humans and the environment.

Lead is a highly poisonous metal (regardless if inhaled or swallowed), affecting almost every organ and system in the body. The main target for lead toxicity is the nervous system, both in adults and children. Long-term exposure of adults can result in decreased performance in some tests that measure functions of the nervous system. Long-term exposure to lead or its salts (especially soluble salts or the strong oxidant PbO2) can cause nephropathy, and colic-like abdominal pains. It may also cause weakness in fingers, wrists, or ankles.

For more information visit:-
http://en.wikipedia.org/wiki/Lead
http://www.theguardian.com/science/grrlscientist/2013/feb/15/1?guni=Article:in%20body%20link