Childhood exposure to lead in gasoline has led to many millions of extra cases of mental disorders over the past 75 years, a new study estimates.
Lead was banned in vehicle fuel in 1996. By examining blood lead levels in children from 1940 to 2015, the study examined its long-term effects in the United States and was published on Wednesday in the Journal of Child Psychology and Psychiatry. The results suggest the nation experienced an estimated 151 million extra mental disorders linked to early childhood exposure to lead from vehicle exhaust.
The exposure has left generations of Americans more depressed, anxious, inattentive, or hyperactive, the study says.
The researchers — a team from Duke University, Florida State University and the Medical University of South Carolina — found that exposure also reduced people’s ability to control impulses and made them more likely to be neurotic.
The lead-related differences in mental health and personality were most pronounced in people born between 1966 and 1986, according to the study. Of that group, the greatest burden of lead-related mental illness was in Generation X, born between 1966 and 1970, which coincided with the peak of leaded gasoline use in the mid-1960s and mid-1970s.
People born in those years “can’t go back in time and change it,” said Aaron Ruben, a co-author of the study and a research fellow in neuropsychology at Duke and the Medical University of South Carolina.
“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 thought,” Ruben said.
Cohorts born around 1940 and 2015 had the lowest lead exposure and lead-related mental illness, the study found.
Although petrol no longer contains lead, it can still be found in other products like some foreign-imported toys, outdated plumbing systems, soil and paint in older homes. (In 1978, lead paint was outlawed.)
The Centres for Disease Control and Prevention state that there is no acceptable level of lead exposure. Even small amounts have been linked to developmental and learning disabilities, given that lead exposure is known to harm the brain, nervous system, and reproductive system. The most susceptible age group for lead poisoning is children under six.
The study, published Wednesday, combined data on blood lead levels and estimates of historical lead exposure with results from past studies, including a 2019 study of nearly 600 New Zealanders who followed children exposed to lead and measured their mental health for more than three decades. Ruben, who was the lead author of that study, said the new research “doesn’t create new information about whether lead causes harm, and we’re not claiming that this study proves causation — we’re really just taking existing evidence and applying it to the entire U.S. population.”
“We’re not at all concerned that we’ve overestimated the harm in any way,” he added.
The study was commended by Dr. Lisa Fortuna, head of the Council on Children, Adolescents, and Families of the American Psychiatric Association.
“There aren’t many studies that examine the possible risks of environmental or toxic factors linked to the emergence of higher rates of mental health issues in the population,” she said. “This study clarifies the significant and enduring influence of environmental factors.“
The study’s findings shouldn’t cause panic, Fortuna said.
“It doesn’t mean that people are, I would say, stuck with mental illness. It doesn’t mean that they’re necessarily going to have a higher risk,” she said. “This is what transpired at the population level,” the statement reads.
The study was conducted a few years after Ruben and colleagues discovered that around half of Americans had reduced IQs as a result of being exposed to leaded gasoline. This study estimates that childhood exposure to lead from gasoline cost Americans about 824 million IQ points.
The initial purpose of adding lead to petrol was to enhance engine performance. Use of leaded gasoline increased after World War II until it was found to be harmful to catalytic converters, which became mandatory in the 1970s. Although some of the risks associated with lead were recognised long before it was prohibited in petrol, it took several years before the federal government made lowering exposure a top priority.
Lead screening is now recommended for all young children, and treatments such as chelation therapy are available to remove the poison if levels are high.
Ruben said prevention is the best way to keep people safe.
“Blood lead levels have decreased significantly, but they can decrease further.” “We’ve done a lot of good in the U.S. by reducing lead exposure,” he said. “I hope we can learn from history about the harm we have done in the United States and try to apply that in the future.“
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