납, or lead, is a heavy metal with the chemical symbol Pb. It is known for its malleability and resistance to corrosion, making it useful in various applications. Lead has been historically used in batteries, radiation shielding, and plumbing materials. However, due to its toxicity, its use has been restricted in many products. Lead is found naturally in the earth's crust and can be extracted from ores such as galena. Exposure to lead can lead to serious health issues, particularly in children, affecting their development and cognitive functions. As a result, many countries have implemented regulations to limit lead exposure in the environment.