An estimated 151 million psychiatric cases in US attributed to lead exposure

Key takeaways:

• A study examined the mental health effects of lead exposure from gasoline over the past 75 years in the U.S.
• Researchers said lead exposure has a larger impact on mental health than previously assumed.

Hundreds of millions of psychiatric disorders in the United States have been linked to childhood exposure of car exhaust from leaded gasoline, according to a recent study in the Journal of Child Psychology and Psychiatry.

The findings indicate that “lead has played a larger role in our mental health than previously thought,” Aaron Reuben, PhD, a postdoctoral scholar in neuropsychology at Duke University, told Healio.

According to Reuben and colleagues, lead exposure in most industrialized countries peaked from 1960 through 1990 due to the use of lead in gasoline, which was banned in the United States in 1996.

Previous research estimates that about 170 million Americans were exposed to leaded gasoline as young children at “levels greater than current (3.5 µg/dL) and previous (5 µg/dL) reference values,” the researchers wrote. Around 60 million of these children were exposed to levels that were three to six times the 5 µg/dL reference value.

Evidence suggests that childhood lead exposure can disrupt brain development, “resulting in lowered cognitive ability, fine motor skills and emotional regulation capacity,” Reuben and colleagues wrote. It has been tied to a variety of mental health disorders like depression, anxiety and hyperactivity.

For their study, Reuben and colleagues combined National Health and Nutrition Examination Survey data with historic data on leaded gasoline to examine childhood blood-lead levels from 1940 to 2015 and estimated its impact on mental health among Americans.

They specifically looked at five outcomes: General Psychopathology points, which the researchers said reflect a person’s “liability to overall mental disorder”; IQ scores; symptoms of internalizing disorders like depression and anxiety; ADHD; and personality trait differences.

“Assuming that published lead-psychopathology associations are causal and not purely correlational,” Reuben and colleagues estimated that leaded gasoline was attributable to 602 million General Psychopathology points in the U.S. population by 2015, representing a 0.13 standard-deviation increase in mental illness liability and about 151 million excess mental disorders.

The researchers also reported population-level standard deviation increases of 0.64 for internalizing disorder symptoms; 0.42 for ADHD symptoms; and 0.14 for neuroticism. The associations were particularly pronounced in people born from 1966 to 1986.

Despite the U.S. ban on leaded gasoline, Reuben said that “lead exposure is still absolutely a concern for American children today.”

“First, most of us have been exposed to levels of lead hundreds of times greater than what would be ‘natural’ or so-called background levels of lead. Even small amounts of exposure have health consequences,” he said. “Second, approximately 500,000 children in the U.S. have elevated lead exposure above these levels each year. Our chief exposure concern is to old leaded paint that has exfoliated inside old homes and outside into soil around homes. Estimates suggest one in four households in the U.S. have soil lead hazards that warrant attention.”

Reuben said he hopes to measure the impact of lead exposure on other domains of health, such as heart, liver and kidney disease.

“A global movement has begun to prevent new lead exposures around the world. This should be an urgent global priority. It is time to stop putting lead into fuel, paint and any products that will interact with consumers or families.”

Reference:

• 20th century lead exposure damaged American mental health. https://today.duke.edu/2024/12/20th-century-lead-exposure-damaged-american-mental-health. Published Dec. 4, 2024. Accessed Dec. 4, 2024.