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Charlottesville, VA — Childhood exposure to leaded gasoline, a once-common source of environmental pollution, has been linked to 151 million excess cases of psychiatric disorders in the United States, according to new research published in the Journal of Child Psychology and Psychiatry. The study sheds light on the long-term mental health effects of lead exposure, particularly among individuals born during the peak era of leaded gasoline use.
The research identifies Generation X — those born between 1966 and 1986 — as the group most significantly impacted. Within this cohort, individuals born between 1966 and 1970 experienced the highest rates of mental health issues, including a 1.75-fold increase in anxiety and depression and a 1.17-fold increase in ADHD symptoms. This timeline aligns with the mid-20th-century peak of leaded gasoline usage.
A Nationwide Public Health Crisis
“Lead exposure across the country has likely played a significant role in worsening mental health in ways that were previously unappreciated,” said Dr. Aaron Reuben, the study’s lead investigator and an assistant professor of clinical neuropsychology at the University of Virginia. However, the study emphasizes that the findings demonstrate a correlation, not a definitive cause-and-effect relationship, between lead exposure and mental illness.
Researchers estimate that from 1940 to 2015, childhood exposure to leaded gasoline contributed to a 0.13 standard deviation increase in the general liability to mental illness within the population. This translated to significant increases in anxiety, depression, ADHD symptoms, and personality traits like neuroticism, which indicates emotional instability.
Historical Context of Lead Exposure
Leaded gasoline, introduced in the 1920s to improve engine performance, was widely used for decades despite mounting evidence of its neurotoxicity. By the 1970s, blood lead levels (BLLs) in children were three to six times higher than today’s clinical safety threshold of 3.5 micrograms per deciliter. The U.S. banned leaded gasoline in 1996, but the legacy of its use continues, as lead persists in old paint, soil, and water pipes.
The study combined data from the National Health and Nutrition Examination Survey with historical gasoline consumption records to estimate childhood BLLs across generations. Researchers then linked these estimates to mental health metrics, including general psychopathology scores — a measure analogous to IQ scores for mental health.
The Lasting Legacy of Lead
The study’s findings underscore the profound, generational impact of lead exposure on mental health. For instance, children born during the peak of leaded gasoline usage in the late 1960s showed marked increases in internalizing disorders, such as anxiety and depression, and symptoms of ADHD.
Dr. Terrie Moffitt, a professor of psychology and neuroscience at Duke University, described the findings as a stark reminder of the “legacy of lead.” “This study is crucial because it shows us the lasting damage caused by lead exposure during an era when it was pervasive,” Moffitt said.
A Call to Action
While reversing past lead exposure is impossible, experts recommend proactive measures to mitigate ongoing risks. Screening for lead exposure, especially in communities with aging infrastructure, is essential, as evidenced by the 2014 water crisis in Flint, Michigan.
“Physicians should remain vigilant for signs of lead exposure, even decades after the fact,” Reuben advised, noting that 90% of lead in the body is stored in the skeleton and can re-enter the bloodstream during times of calcium deficiency, pregnancy, or osteoporosis.
The study highlights the importance of addressing the residual effects of lead exposure through mental health interventions such as therapy and medication. It also calls attention to the environmental and social inequities that disproportionately expose disadvantaged communities to lead, further compounding their risk of mental illness.
This research was supported by the National Institute of Environmental Health Sciences.
