Humans have found lead useful for thousands of years, but the metal's toxic effects didn't become well known until the 20th century. Now, using historical hair samples, researchers have shown that regulations targeting heavy-metal pollution were extremely effective at reducing the public's exposure to lead once its dangers were known.
"We have hair samples spanning about 100 years," study co-author Ken Smith, a demographer at the University of Utah, said in a statement. The study focused on people living in Utah.
