151 million Americans have mental health disorders linked to leaded gasoline
In 1923, lead was first introduced into gasoline to enhance car engine performance. However, this improvement in automotive health came at a significant cost to human well-being.
According to a new study, exposure to car exhaust from leaded gasoline during childhood has altered the mental health balance in the U.S. population, leading to generations of Americans who are more depressed, anxious, inattentive, or hyperactive.
The research estimates that over the past 75 years, 151 million cases of psychiatric disorders have resulted from American children’s exposure to lead.
The study was led by Aaron Reuben, a postdoctoral scholar in neuropsychology at Duke University, and his colleagues at Florida State University,
The findings suggest that Americans born before 1996 experienced significantly higher rates of mental health problems due to lead exposure. These individuals likely experienced personality changes that made them less successful and resilient in life.
Leaded gasoline for cars was banned in the U.S. in 1996, but the researchers emphasize that anyone born before then – especially during its peak use in the 1960s and 1970s – had concerningly high lead exposures as children.
Neurotoxic effects of lead
Lead is neurotoxic and can erode brain cells and alter brain function once it enters the body. Health experts state that there is no safe level of exposure at any point in life.
Young children are especially vulnerable to lead’s ability to impair brain development and alter brain health. Unfortunately, regardless of age, our brains are ill-equipped to combat lead toxicity.
Because water systems in older American cities still contain lead pipes, the U.S. Environmental Protection Agency (EPA) issued regulations in October that give cities 10 years to identify and replace lead plumbing, allocating $2.6 billion to get it done.
Earlier this year, the EPA also lowered the level of lead in soil that it considers potentially hazardous, resulting in an estimated one in four U.S. households having soil that may require cleanup.
“Humans are not adapted to be exposed to lead at the levels we have been exposed to over the past century,” Reuben said. “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.”
Lead exposure and mental health
Throughout the past century, lead was used in paint, pipes, solder, and most disastrously, automotive fuel.
Numerous studies have linked lead exposure to neurodevelopmental and mental health problems, particularly conduct disorder, attention-deficit/hyperactivity disorder (ADHD), and depression.
However, it had not been clear how widespread lead-linked mental illness symptoms might have been.
Lifelong burden of lead exposure
To address this complex question, Reuben and his co-authors Michael McFarland and Mathew Hauer, both professors of sociology at Florida State University, turned to publicly available nationwide data.
By using historical data on U.S. childhood blood-lead levels, leaded-gas use, and population statistics, they determined the likely lifelong burden of lead exposure carried by every American alive in 2015.
From this data, the researchers estimated lead’s assault on mental health and personality by calculating “mental illness points” gained from leaded gas exposure as a proxy for its harmful impact on public health.
“This is the exact approach we have taken in the past to estimate lead’s harms for population cognitive ability and IQ,” McFarland said, noting that the research team previously identified that lead stole 824 million IQ points from the U.S. population over the past century.
Generational shifts in mental health
“We saw very significant shifts in mental health across generations of Americans,” Hauer said. “Meaning many more people experienced psychiatric problems than would have if we had never added lead to gasoline.”
Lead exposure led to greater rates of diagnosable mental disorders, like depression and anxiety, but also increased instances of individuals experiencing milder distress that could impair their quality of life.
“For most people, the impact of lead would have been like a low-grade fever,” Reuben explained. “You wouldn’t go to the hospital or seek treatment, but you would struggle just a bit more than if you didn’t have the fever.”
Lead’s effect on brain health has also been linked to changes in personality observable at the national level. “We estimate a shift in neuroticism and conscientiousness at the population level,” McFarland said.
The scope of lead exposure
As of 2015, more than 170 million Americans – over half of the U.S. population – had clinically concerning levels of lead in their blood when they were children.
This exposure likely resulted in lower IQs, more mental health problems, and a higher risk for other long-term health impairments, such as increased cardiovascular disease.
Leaded gasoline consumption rose rapidly in the early 1960s and peaked in the 1970s. Consequently, Reuben and his colleagues found that essentially everyone born during those two decades was nearly certain to have been exposed to pernicious levels of lead from car exhaust.
The generation with the greatest lead exposures, Generation X (those born between 1965 and 1980), would have experienced the most significant mental health losses.
Addressing the legacy of lead exposure
“We are coming to understand that lead exposures from the past – even decades in the past – can influence our health today,” said Reuben.
“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.”
The study is published in the Journal of Child Psychology and Psychiatry.
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