Childhood exposure to lead in the United States has left a lasting legacy on mental health and personality traits, according to a study published in the Journal of Child Psychology and Psychiatry. Researchers found significant associations between lead exposure and an increase in mental illness symptoms, alongside shifts in personality traits that disadvantage individuals over the long term.

The study, led by Michael J. McFarland, Ph.D., of Florida State University, drew on data from the National Health and Nutrition Examination Surveys combined with historic leaded-gasoline usage records. This approach allowed the researchers to estimate blood-lead levels in U.S. children from 1940 to 2015 and assess how these exposures correlated with mental health outcomes and personality differences.

By 2015, lead exposure—primarily from leaded gasoline—was linked to a substantial increase in the liability to mental illness across the U.S. population. The researchers attributed an estimated 151 million excess mental disorders to childhood lead exposure during this period. The study also revealed significant impacts on specific disorders, with higher rates of anxiety, depression, and attention-deficit/hyperactivity disorder (ADHD) symptoms tied to elevated lead levels.

In addition to mental health outcomes, personality traits were notably affected by lead exposure. Researchers observed an increase in neuroticism, characterized by heightened emotional instability, and a decline in conscientiousness, which is associated with lower levels of self-discipline and organization. These effects were particularly pronounced among individuals born between 1966 and 1986, a cohort that experienced peak exposure to leaded gasoline.

The findings underscore the long-term impact of environmental lead exposure on public health and highlight its far-reaching consequences. According to the researchers, the burden of mental illness and personality changes attributable to lead exposure may be much greater than previously understood.

This research calls for greater awareness of the generational effects of environmental toxins and emphasizes the need for ongoing efforts to address the consequences of historical lead exposure. It also serves as a cautionary tale for policymakers to prioritize environmental health safeguards to prevent similar public health crises in the future.