Leaded Gasoline Lowered the IQ of Half of U.S. Population, Study Finds
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Leaded gasoline exposure caused the IQ of about half of Americans to decrease, according to a new study.
The peer-reviewed study published in the Proceedings of the National Academy of Sciences estimated that 170 million Americans were exposed to high-lead levels in early childhood.
The Duke University and Florida State University researchers found that the leaded gasoline in cars may have lowered a person's IQ by an average of 2.6 points, which is a total of roughly 824 million points lost by Americans.
The study found that people born in the 1960s and 1970s, when lead gas consumption was booming, may have lost up to seven IQ points at worst.
"I frankly was shocked," said lead author Michael McFarland, professor of sociology at Florida State University, told USA Today. "And when I look at the numbers, I'm still shocked even though I'm prepared for it."
Scientists focused on Americans more before born before 1996, the year that leaded gasoline was banned in America, and still alive in 2015, to determine the long-term effects of leaded gasoline exposure.
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Lead is a neurotoxin, and no amount is considered safe. It was added to gasoline to help engines run more smoothly until it was replaced with other additives. It has also been linked with heart disease, kidney disease, cardiovascular disease and dementia.
According to the Centers for Disease Control and Prevention, 3.5 micrograms per deciliter in blood lead levels is considered a "high."
"This is important because we often think about lead as an issue for children, and of course it is," McFarland told NBC News. "But what we really wanted to know is what happens to those children who were exposed?"
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The study also revealed most Black adults under age 45 experienced "considerably higher" blood lead levels in childhood than white people. The racial disparities are generally due to environmental contamination and infrastructure issues.
The study was conducted using publicly available data on U.S. childhood blood-lead levels, leaded-gas use and population statistics. Exposure came primarily from inhaling auto exhaust.
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He said that 2 to 3 point IQ differential is nominal unless an individual is lower side of IQ distribution.
"If you're more toward cognitive impairment, a couple points can mean a lot," McFarland told NBC News.
