Psychiatric disorders in more than 150 million people over the past 75 years may have resulted from childhood exposure to leaded gas, new research suggests.
No level of lead exposure is safe for children, and it can lead to hearing and speech problems, damage to the brain and central nervous system, learning and behavior issues, among other serious adverse medical effects, according to the Center for Disease Control and Prevention. A study published Wednesday in The Journal of Child Psychology and Psychiatry suggests that the mental health impacts of childhood lead exposure are even more dire than previously thought.
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"We saw very significant shifts in mental health across generations of Americans, meaning many more people experienced psychiatric problems than would have if we had never added lead to gasoline," Mathew Hauer, a sociology professor at Florida State University, said in a news release.
Using historical data about childhood blood lead levels, population statistics and leaded gas use, researchers from Florida State and Duke University wanted to pinpoint more precisely the mental health impacts of leaded gas exposure for Americans alive in 2015. The researchers found significant increases in depression, anxiety, attention-deficit/hyperactivity disorder and personality changes for people born before 1996, when leaded gas was banned in the United States. People born during the 1960s and 1970s, when leaded gas use was at its peak, were particularly affected, according to the study.
"We have very few effective measures for dealing with lead once it is in the body, and many of us have been exposed to levels 1,000 to 10,000 times more than what is natural," said Aaron Reuben, a postdoctoral scholar in neuropsychology at Duke.
"For most people, the impact of lead would have been like a low-grade fever," Reuben said. "You wouldn't go to the hospital or seek treatment, but you would struggle just a bit more than if you didn't have the fever."
Leaded gas was introduced in the early 1920s after engineers at General Motors discovered that lead reduced engine knock. After five people working at refineries in New Jersey and Ohio died in 1924 from suspected lead poisoning, the surgeon general temporarily suspended the use of leaded gasoline. A panel did not find enough evidence that short-term lead exposure was dangerous but warned that long-term exposure could result in "chronic degenerative diseases of a less obvious character." Still, leaded gas quickly came back onto the market, according to the Environmental and Energy Study Institute.
A 1984 report from the Environmental Protection Agency on the costs and benefits of reducing lead in gas indicated that the amount of lead in blood is directly related to the amount of lead in gasoline.
"Lead has long been known to cause pathophysiological changes, including the inhibition of major enzymatic processes, adverse effects on the central nervous system, and decreases in cognitive ability," the authors wrote. "Children are especially vulnerable to lead, and black children are more severely affected than others. Children with elevated blood lead levels require medical monitoring and/or treatment.
"Adverse effects of lead in the blood are now found at levels that were previously thought safe, and additional effects are suspected."
It took until 1987 for the EPA to introduce tighter restrictions on acceptable lead levels in gas and until 1996 for leaded gas to be banned altogether.