Lead

Lead (chemical symbol: Pb) is a chemical element belonging to the heavy metals. It is a soft metal that can be easily shaped, with a dull gray color when freshly cut, but quickly darkens when exposed to air. Its melting point is significantly lower than most common metals, which is why ancient peoples were able to cast and work it.

Lead is among the earliest metals extracted by humans, because its primary ore—galena, a compound of lead and sulfur (lead sulfide)—can be easily separated through smelting. From the Middle Ages onward, lead's toxicity when ingested became known, leading to the reduction or restriction of its use.

Physical and chemical properties

Lead is an extremely soft metal; it can be scratched with a fingernail. It is malleable and lacks strength, which is why it is not used in load-bearing construction. It has the ability to block radiation such as gamma rays and X-rays, making it useful in hospital shielding and radiation facilities. When exposed to air, an oxide layer forms on its surface that protects what lies beneath, allowing it to have a long lifespan.

Uses

The greatest current use is in lead-acid batteries for vehicles and energy storage. It is also used in radiation shielding, certain pipes and roofs, calibration equipment, and metal alloys such as solder. Historically, lead was added to paint and motor fuel (petrol), but these two uses have been largely phased out in most countries for health reasons.

Health hazards

Lead is a cumulative poison in the body; there is no safe level of exposure. It affects the nervous system, particularly in young children, and is linked to reduced learning ability and behavioral changes. In adults it can cause anemia, kidney damage, and reproductive complications. Routes of exposure include water passing through lead pipes, dust from old paint, and occupational and waste processing settings lacking proper controls.