Lead (Pb) is a dense, soft, grey metal which occurs mainly in lead sulphide ore known as galena. Because it is cheap, malleable and resistant to corrosion, lead has long been used for many purposes. It was widely used by the Romans, to make bronze and pewter and for water tanks, pipes and drinking vesels. Because it is waterproof, lead has been widely utilised for roofing and to protect underground pipes and cables. Plumbum, the metal's Latin name, is where the word 'plumber' originated. In recent times, lead has been used as an anti-knock additive in petrol, and its ability to absorb radiation has made it useful for shielding nuclear reactors and X-ray equipment. Lead's toxicity has led to a reduction in some of its uses, particularly in pipes and petrol.
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