Lead is a heavy metal applied in batteries, alloys, solder and industrial coatings, and it poses severe health risks once entering the human body via breathing, eating or skin contact. Lead cannot be broken down by human metabolism and builds up in blood, bones and organs permanently. It blocks hemoglobin production and causes anemia, while damaging the nervous system to trigger headaches, poor memory and slow responses; low-level exposure can permanently hinder children’s brain growth. It also hurts kidney function, disrupts calcium absorption to weaken bones, and disturbs reproductive and endocrine systems, bringing lower fertility and fetal defects in pregnant women. Stored lead in bones may leak back into blood for years, causing repeated organ damage long after initial exposure.