A new study reported on this week says that lead in gasoline could be tied to "over 150 million excess cases of mental health disorders", including anxiety, depression and ADHD, according to NBC News.

A new study estimates that childhood exposure to leaded gasoline caused 151 million excess psychiatric disorders in the U.S. over the past 75 years. Despite its ban in 1996, lead's lingering impact on mental health was traced through childhood blood lead levels from 1940 to 2015.

Lead was added to gasoline to enhance engine performance, but its use surged post-WWII until catalytic converters, required in the 1970s, highlighted its drawbacks. Despite early awareness of its dangers, federal efforts to reduce lead exposure lagged for years.

The NBC News report says that researchers from Duke, Florida State, and the Medical University of South Carolina found that lead exposure reduced impulse control and increased neuroticism, with the strongest effects in those born between 1966 and 1986.

Generation Xers born from 1966 to 1970, during peak leaded gasoline use, faced the highest burden of lead-related mental health issues.

Aaron Reuben, a co-author of the study and a postdoctoral scholar in neuropsychology at Duke and the Medical University of South Carolina, commented: “Studies like ours today add more evidence that removing lead from our environment and not putting it there in the first place has more benefits than we previously understood.”

He said of the new research that it “doesn’t create new information about whether lead causes harm, nor do we say this is a study that proves causation — we’re really just taking existing evidence and applying it to the whole U.S. population.”

“We’re not at all concerned that we have in any way overestimated the harm,” he continued. 

“We don’t often get to see a lot of studies that look at environmental, or toxin-related, potential associated risks with the development of elevated rates of mental health problems in populations. The research shed some light on the profound and lasting impact of environmental factors,” added Dr. Lisa Fortuna, chair of the American Psychiatric Association’s Council on Children, Adolescents and Their Families.

“It does not mean that people are, I would say, stuck with a mental illness. It doesn’t mean that they’re necessarily going to have a higher risk. It’s really an issue of, ‘Here’s what’s happened at a population level.’”

A previous study by Reuben and colleagues found that leaded gasoline exposure lowered the IQ of about half the U.S. population, costing 824 million IQ points. The new research highlights that those born around 1940 and 2015 had the lowest lead exposure and related mental illnesses, NBC reported.

Although banned in gasoline, lead persists in sources like old paint, outdated water lines, some imported toys, and soil. The CDC states there is no safe level of lead exposure, which is particularly harmful to children under 6, affecting brain development, learning, and the nervous and reproductive systems.