Exposure to exhaust from leaded gasoline during childhood has significantly impacted mental health across generations in the U.S. Researchers estimate that this exposure has contributed to 151 million cases of mental health disorders over the past 75 years, leading to increased levels of depression, anxiety, and attention issues in Americans.
In 1923, lead was introduced into gasoline to improve engine performance. However, the cost of that improvement has been the well-being of countless individuals.
Recent research indicates that childhood exposure to car exhaust from leaded gasoline has disrupted the mental health landscape in the U.S., resulting in higher rates of depression, anxiety, and attention-related disorders across generations. Over the last 75 years, it is estimated that 151 million psychiatric cases can be linked to children’s lead exposure.
Aaron Reuben, a postdoctoral scholar in neuropsychology from Duke University, along with colleagues from Florida State University, found that individuals born before 1996 faced notably higher mental health challenges due to lead, likely affecting their personalities and reducing their chances of success and resilience in life.
Even though leaded gasoline was banned in the U.S. in 1996, those born earlier, particularly during its peak usage in the 1960s and 1970s, were exposed to alarmingly high levels of lead as children.
The findings will be published the week of December 4 in the Journal of Child Psychology and Psychiatry.
Lead is known to be neurotoxic, damaging brain cells and altering brain function upon entry into the body. Health experts emphasize that any level of exposure is unsafe, especially for young children, who are more susceptible to its harmful effects on brain development. Unfortunately, no one can effectively prevent lead toxicity at any age.
Due to the presence of lead pipes in older cities, the EPA announced regulations in October requiring cities to replace lead plumbing within the next ten years and allocated $2.6 billion for this effort. Earlier this year, the EPA also lowered the threshold for lead levels in soil, potentially affecting 1 in 4 U.S. households with soil needing cleanup.
“Humans are not equipped to handle the lead exposure levels we’ve faced over the past century,” Reuben stated. “Many of us have encountered lead levels 1,000 to 10,000 times higher than natural levels, with very few effective methods for mitigating its impacts after it enters the body.”
Over the last hundred years, lead was used in a variety of products including paint, pipes, and, most critically, as a fuel additive in cars. Numerous studies have connected lead exposure to various neurodevelopmental and mental health issues, notably conduct disorder, attention-deficit/hyperactivity disorder, and depression. However, the full extent of lead-associated mental health symptoms had not been previously established.
To explore how decades of leaded gasoline use might have permanently affected mental health, Reuben and his co-authors, Michael McFarland and Mathew Hauer from Florida State University, analyzed publicly available national data.
By examining historical data on childhood blood-lead levels, patterns of leaded gasoline usage, and population stats, they calculated the potential lifelong impact of lead exposure for individuals alive in 2015. They used this data to estimate lead’s detrimental effects on mental health and personality by determining the “mental illness points” accrued from leaded gasoline exposure as an indicator of public health repercussions.
“This approach mirrors what we’ve done previously to assess lead’s impact on cognitive function and IQ,” McFarland pointed out, adding that the research team had already found that lead exposure has diminished the U.S. population’s total IQ by 824 million points over the last century.
“Significant changes in mental health have been observed across different generations of Americans,” Hauer noted. “This suggests that a greater number of individuals faced psychiatric issues than would have occurred had lead never been added to gasoline.” Lead exposure has been associated with increased rates of diagnosable mental disorders like depression and anxiety, along with more common, mild distress that affects overall quality of life.
“For most individuals, the effects of lead would be similar to having a low-grade fever,” Reuben explained. “You wouldn’t require hospitalization or treatment, but you would find daily life a bit more challenging.”
Research also indicates that lead’s detrimental effects extend to personality traits on a broader scale. “We observe changes in neuroticism and conscientiousness at the population level,” McFarland remarked.
By 2015, over 170 million Americans (more than half of the population) had concerning lead levels in their blood during childhood, which likely resulted in reduced IQ scores and increased mental health issues, along with heightened risks for other long-term health concerns, such as cardiovascular diseases.
Lead gasoline usage saw a rapid rise in the early 1960s, peaking in the 1970s. Consequently, Reuben and his team found that nearly everyone born in those two decades was likely exposed to harmful levels of lead from vehicle emissions. Generation X (born between 1965 and 1980) experienced the most significant reductions in mental health as a result of lead exposure.
“We are beginning to understand that past lead exposures, even those from decades ago, can still impact our health today,” Reuben stated. “Moving forward, it’s essential to fully grasp lead’s historical role in public health and ensure that today’s children are shielded from future lead exposures.”
