Exposure to lead in gasoline during childhood has led to several million additional cases of psychiatric disorders over the past 75 years, a new study estimates.
Lead was banned in automobile fuel in 1996. The study, published Wednesday in the Journal of Child Psychology and Psychiatryexamined its lasting impact in the United States by analyzing children’s blood lead levels from 1940 to 2015. According to the results, the national population experienced an estimated 151 million excess mental health disorders attributable to exposure lead from car exhaust during children’s early development.
According to the study, this exposure has made generations of Americans more depressed, anxious, inattentive or hyperactive.
The researchers – a group from Duke University, Florida State University and the Medical University of South Carolina – found that exposure also reduced people’s ability to control their impulses and made them more prone to becoming neurotic.
According to the study, mental health and personality differences associated with lead were most pronounced among people born between 1966 and 1986. Among this group, the greatest burden of lead-related mental illness was among members of Generation X born between 1966 and 1970, coinciding with the peak of leaded gasoline consumption in the mid-1960s and mid-1970s.
People born in those years “can’t go back in time and change that,” said Aaron Reuben, a co-author of the study and a postdoctoral researcher 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 realized,” Reuben said.
Groups born around 1940 and 2015 had the lowest exposure to lead and lead-related mental illnesses, the study found.
Although it is no longer present in gasoline, lead is still present in other sources, such as certain toys imported from other countries, water pipes which have not yet been updated, some dirt and paint in old houses. (Lead paint was banned in 1978.)
There is no safe level of exposure to lead, according to the Centers for Disease Control and Prevention. Even small amounts are associated with developmental and learning difficulties, as lead exposure is known to harm the brain and nervous and reproductive systems. Children under 6 years old are most vulnerable to lead poisoning.
The study released Wednesday combined data on blood lead levels and estimates of historical lead exposure with results from previous studies, including a 2019 study. study of nearly 600 New Zealand residents which followed lead-exposed children and measured their mental health over more than three decades.
Reuben, who was the lead author of that study, said the new research “does not create new information about whether lead is harmful, nor are we saying that it is ‘a study that proves causation – we simply take the existing evidence and apply it.’ to the entire American population.
“We are not at all afraid of having overestimated the damage,” he added.
Dr. Lisa Fortuna, chair of the American Psychiatric Association’s Council on Children, Adolescents and Their Families, praised the study.
“We don’t often see a lot of studies that look at environmental or toxin-related risks associated with the development of high rates of mental health problems in populations,” she said. “Research has highlighted the profound and lasting impact of environmental factors.”
The study results shouldn’t cause panic, Fortuna said.
“It doesn’t mean that people are, I would say, struggling with mental illness. That doesn’t mean they will necessarily be at higher risk,” she said. “It’s really about, ‘Here’s what happened at the population level. »
The study comes a few years after Reuben and other researchers discovered that exposure to leaded gasoline lowered the IQ of about half of the US population. This study estimates that childhood exposure to lead from gasoline costs Americans approximately 824 million IQ points.
Lead was initially added to gasoline to improve engine performance. The use of leaded gas increased after World War II until it proved harmful to catalytic converters, which became necessary in the 1970s. Some of the dangers of lead were known long before it was banned in the world. gasoline, but reducing lead exposure did not become a federal priority for many years.
Lead testing is now recommended for all young children, with treatment such as chelation therapy available to remove the poison if levels are high.
Reuben said prevention is the best way to keep people safe.
“We have done a lot of good in the United States by reducing exposure to lead. Blood lead levels have dropped significantly, but they could fall further,” he said. “I hope we can learn lessons from history about how much damage we have done to the United States and try to apply them in the future. »