Lead exposure in the 20th century may have led to mental health issues in Americans, a new study suggests.
Researchers from Duke University and Florida State University studied the impact of lead in gasoline, which was first added in 1923 to help keep car engines healthy. (It was later banned from all U.S. vehicles in 1996.)
The use of lead gas is said to have peaked from the mid-1960s through the mid-1970s.
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The findings revealed that childhood exposure to car exhaust from leaded gas resulted in an imbalance of mental health in the U.S., which made "generations of Americans more depressed, anxious and inattentive or hyperactive," according to a Duke press release.
The study, published in the Journal of Child Psychology and Psychiatry, attributed an estimated 151 million cases of psychiatric disorders over the past 75 years to leaded gas exposure in American children.
Americans born before 1966 experienced "significantly higher rates of mental health problems as a result of lead, and likely experienced changes to their personalities that would have made them less successful and resilient in life," the researchers wrote.
‘No safe level’
Lead is "neurotoxic" and can erode brain cells and alter brain function – therefore, there is "no safe level of exposure at any point in life," according to Duke.
While young children are especially vulnerable to the effects, the researchers noted that "no matter what age, our brains are ill-equipped for keeping lead toxicity at bay."
"Lead has played a larger role in our mental health than previously thought."
Lead study author Aaron Reuben, PhD, based in North Carolina, wrote in a statement that humans are "not adapted to be exposed to lead at the levels we have been exposed to over the past century."
He added, "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."
‘Clinically concerning’
The researchers analyzed historical data on childhood blood-lead levels, leaded gas use and U.S. population statistics, determining that more than 170 million Americans had "clinically concerning levels" of lead in their blood as children as of 2015.
Lead exposure resulted in greater rates of mental disorders like depression and anxiety, but also more "mild distress that would impair quality of life."
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"We saw very significant shifts in mental health across generations of Americans — meaning many more people experienced psychiatric problems than would have if we had never added lead to gasoline," co-author Matt Hauer said in a statement.
This likely resulted in lower IQs, mental health problems and other long-term health complications, such as cardiovascular disease, the study suggests.
In an interview with Fox News Digital, Reuben reiterated that mental health in America was "likely significantly influenced by Americans’ exposure to lead over the past century."
He said, "Declining lead exposures were likely met by improving mental health. Lead has played a larger role in our mental health than previously thought."
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While the researcher said he was not surprised to find that lead caused harm, he was surprised by the "magnitude" of its effect.
"We assume that our ‘lead problem’ was solved in the 1970s and 1980s, but that was just the start of solving the problem," he said.
"There are millions of Americans alive today who had extremely high lead exposure as children. How have those exposures influenced the trajectories of their lives? This is one thing we set out to answer."
Reuben pointed out some limitations of the study, including that it only included two cohorts and that it did not study exposures from other sources besides gasoline.
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"As time goes on, we hope that more lead-mental health studies become available for us to improve our estimates based on better lead-harm curves," he said.
"Future studies should ideally be able to incorporate lead exposure from water and paints."
The expert urged the public to take lead exposure seriously by removing hazards that still exist in some paint, fuel, batteries and other mediums.
"There are millions of Americans alive today who had extremely high lead exposure as children."
The U.S. Environmental Protection Agency (EPA) issued a regulation in Oct. 2024 giving cities 10 years to replace any remaining lead plumbing.
The agency also took action in Jan. 2024 to lower the levels of lead in soil at residential homes across the country.
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In an interview with Fox News Digital, California child psychologist Dr. Michele Borba noted that the current youth mental health crisis in America has been largely attributed to social media, but that this new study on lead exposure explores a "new realm" of what could be behind deteriorating mental health.
"It's an unusual and fascinating reason that most of us have never been prepared for or even thought of – but it isn't just children's mental health and well-being at stake," she said.
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"We may be overlooking other generations and the long-lasting impact of lead exposure."
Borba said that while more research is required on the topic, she recommends that other mental health experts take lead exposure into consideration when treating patients.