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• Posted December 4, 2024

20th Century Lead Exposures Took Grim Toll on Americans' Health

Decades of lead exposure from car exhaust altered the mental health of millions of Americans, making them more prone to depression, anxiety and ADHD, a new study claims.

Lead was first added to gasoline in 1923 to help keep car engines healthy, researchers said.

But lead is toxic to brain cells, and there’s no safe level of exposure at any point in life. Children are especially vulnerable, as lead is known to impair brain development.

Leaded gas was banned in the United States in 1996, but anyone born before then -- especially during peak use in the 1960s and 1970s -- is at risk for toxic brain effects from car exhaust, researchers said.

Such exposure has caused as many as 151 million cases of mental health disorder during the past 75 years, researchers reported.

Americans born before leaded gas was banned have experienced significantly higher rates of mental health problems, and likely underwent changes in their personalities that made them less successful and resilient in life, the study concluded.

“Humans are not adapted to be exposed to lead at the levels we have been exposed to over the past century,” said researcher Aaron Reuben, a postdoctoral scholar in neuropsychology at Duke University, in Durham, N.C.

“We have very few effective measures for dealing with lead once it is in the body, and many of us have been exposed to levels 1,000 to 10,000 times more than what is natural,” Reuben added in a university news release.

For the study, Reuben and his colleagues analyzed historical data on blood-lead levels in U.S. children, patterns of leaded gasoline use in America and population statistics of mental health problems.

This data allowed them to calculate “mental illness points” gained from exposure to leaded gas, researchers aid.

“This is the exact approach we have taken in the past to estimate lead’s harms for population cognitive ability and IQ,” noted researcher Michael McFarland, a professor of sociology at Florida State University. Previous research from the team found that lead stole 824 million IQ points from the U.S. population over the past century.

As of 2015, over 170 million Americans -- more than half the U.S. population -- had elevated levels of lead in their blood as children, likely blunting their IQ and putting them at high risk for mental health disorders, researchers said.

Lead exposure is significantly linked to higher rates of mental disorders like depression and anxiety, researchers found. It also likely caused mild distress that impaired people’s quality of life without resulting in a full-blown psychiatric condition.

The new study was published Dec. 4 in the Journal of Child Psychology and Psychiatry.

“We saw very significant shifts in mental health across generations of Americans,” said researcher Mathew Hauer, a professor of sociology at Florida State. “Meaning many more people experienced psychiatric problems than would have if we had never added lead to gasoline.”

Generation X (born 1965 to 1980) would have had the greatest lead exposures and the greatest mental health losses, the researchers concluded.

“We are coming to understand that lead exposures from the past -- even decades in the past -- can influence our health today,” Reuben said. “Our job moving forward will be to better understand the role lead has played in the health of our country, and to make sure we protect today’s children from new lead exposures wherever they occur.”

More information

The U.S. Centers for Disease Control and Prevention has more about the health effects of lead exposure.

SOURCE: Duke University, news release, Dec. 4, 2024