In paint, it adds sticking power. Lead-based paint was banned in 1978, leaded gasoline in 1986. But the EPA estimates that more than half the nation's houses still have lead paint, and exhaust fumes have made America's highway shoulders rich with lead. Lead is most dangerous to children under the age of 6, whose brains are still developing, the Centers for Disease Control and Prevention in Atlanta says. Even a little bit can cause a child permanent brain damage and learning disabilities.
High doses cause mental retardation and death.
Adults, whose neurological functions have matured, can tolerate more lead than children before getting sick. Exactly how much is still under scientific debate. The CDC considers lead poisoning the nation's biggest health threat to children. Other researchers and scientists put the number much higher. Everyone agrees that lead-based paint is the primary culprit.