Groundbreaking study links childhood lead exposure to nationwide mental health decline

A researcher from the Medical University of South Carolina has contributed to a groundbreaking study linking childhood exposure to leaded gasoline with a nationwide decline in mental health across the United States over the past 75 years. Leaded fuel, used to improve engine performance since the 1920s, was ultimately phased out due to its high toxicity. Aaron Reuben, Ph.D., a postdoctoral fellow in the MUSC Department of Psychiatry and Behavioral Sciences, and researchers from Florida State University shared their findings. 

“We have known for hundreds of years that lead is toxic,” said Reuben. “What we learned over the last 70 years is that lead, at the levels distributed out of tailpipes, was more toxic than we thought.” 

In the U.S., lead was gradually phased out of automotive fuel beginning in 1975.

Reuben and fellow researchers conducted the study using publicly available data estimating that half of the United States population experienced high lead exposure during childhood. This led to an estimated increase of 600,000 “psychopathology points” to the U.S. population and approximately 151 million cases of psychiatric disorders attributable to lead.

A "psychopathology point" is measure used to assess the degree of decline in a person’s mental health. Higher scores indicate a greater risk for developing additional mental health issues. In the case of lead exposure, scientists used this measurement to estimate how much leaded gasoline may have contributed to increased mental illness in the U.S. that likely wouldn't have occurred without this exposure.

Reuben and the research team traced data back to 1976, when the U.S. started blood-lead surveillance. Then, they combined this data with historical records of lead levels in gasoline and reverse-estimated childhood lead exposures in the ‘40s, ‘50s and ‘60s. The study then highlighted the long-term mental health effects of lead, particularly on Generation X, Reuben said.

“When we look at the burden of lead and how it fell on different birth cohorts,  we find that the folks born during the peak era of lead gasoline, the late 1960s across the 1970s and early 1980s, these were folks exposed reliably to the most lead,” said Reuben. “And they would have gone on to experience more severe mental health problems as a result.” 

Reuben said there is much we still don’t know about how lead harms the brain. However, one well-established mechanism of neurotoxicity is lead’s ability to mimic calcium, an element critical for proper neuronal function. Lead also disrupts basic cell mechanisms, resulting in a brain that may be less efficient at accomplishing tasks such as managing emotions and generating and controlling impulses. One result of this is people with less ability to direct their behaviors to achieve their goals.

Reuben said there is a long road ahead to remove lead from our environment, but it’s not impossible. “We as a society need to devote the proper resources to the problem, and whenever we do that, the costs are far outweighed by the benefits.”