A new study shows half of the adults born in the United States were exposed to harmful levels of lead as children.

The study found about 170 million Americans born between 1961 and 1980 had high amounts of lead in their blood.

That number is about 53% of the total population.

Researchers blame leaded gasoline, which was commonly used to fuel cars in the 1960s and 70s, and exposure to that car exhaust.

One of the lead-related health problems is faster aging of the brain. Experts estimate "affected people" lost 800 million IQ points collectively - about 2.6 points per person.