More than half of Americans could have lowered IQs from lead exposure
Childhood exposure to leaded gasoline has had devastating results.
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Leaded gasoline for cars was banned in Canada in 1990, and in the U.S. in 1996. But its damage persists in a significant way: a new study from Duke University found that lead exposure has shrunk the IQs of more than half the American population.
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Lead was first added to gas in the 1920s, NPR reported last year, as a way to improve engine performance. It was known at the time that lead was dangerous, and there was some concern that auto workers might be negatively impacted by leaded gasoline. But both powerful chemical companies and the inventor of leaded gas, Thomas Midgley, assured the public it would be safe. (Midgley would later come down with lead poisoning himself.)
It was commonly used for more than 50 years before rich countries began to realize and acknowledge that it was dangerous, largely as a result of a 1979 study of the neurological impact of lead on children. Even minor exposure to lead in childhood has been linked to lower IQs and increased rates of violent crime.
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The Duke University study found that Americans born before 1996 — the year the U.S. banned the sale of leaded gas — are now at a greater risk for health problems including rapid aging of the brain, as well as bone and cardiovascular issues. People who were born in the 1960s and ’70s, during the peak use of leaded gas, are especially at risk. People older and younger than that generation — people born in the 1940s, and people born in the mid-’80s and ’90 — have much lower levels of lead in their blood. From the late ’60s to early ’80s, the average blood-lead level for the general American population “was routinely three to five times higher than the current reference value for clinical concern,” the study found.
100 million had lead levels more than three times what’s safe
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Duke researchers used data from the National Health and Nutrition Examination Survey, a continuous national survey conducted by the US Centers for Disease Control and Prevention, looking at the period from 1976 to 2016. They found that lead exposure in childhood was “ubiquitous” in Americans alive in 2015. That year, fewer than half of Americans — 131 million out of 318 million — had blood-lead levels considered safe. Most of those people — 100 million of them — had childhood blood-lead levels that were more than three times higher than the current safety standard. About 10 million people had childhood levels move than seven times higher than the current standard.
“I, frankly, was shocked,” Michael McFarland, co-author of the study, told Duke’s news outlet. “And when I look at the numbers, I’m still shocked even though I’m prepared for it.”
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Those numbers have severe consequences. Researchers calculate that the people with the highest amounts of lead in their blood may have lost an average of seven IQ points. That might not sound like a lot, but it could be the difference between being considered someone with bel0w-average cognitive ability and being intellectually disabled, the study points out. Overall, study found that the U.S. lost a cumulative 824 million IQ points. (The IQ system has been the subject of some controversy, but a disparity this significant is still important to note.)
Some countries used leaded gas until mere months ago
In 2002, the United Nations Environment Programme (UNEP) started campaigning against the use of leaded gas. By the ’80s, most high-income countries started limiting its use. It was banned in Canada in 1990, with the exception of cars used in stock-car and drag races, CTV reported. Its use for those cars was also banned in 2010.
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Lead exposure is still an issue in Canada, though. According to Health Canada, 100 per cent of Canadians aged three to 79 had lead in their blood. But the average level was relatively low, with most people under the level needing health intervention line. Predictably, older people had the highest lead levels. At all age groups above age 12, boys and men had higher lead levels than girls and women.
A 2019 review of thousands of samples of drinking water from across the country found disturbingly high lead levels in many places, including schools and daycares. Montreal, Regina and Prince Rupert, B.C had some of the highest levels nationally.
And as with so many other health issues, people who are marginalized in other ways are also more likely to be vulnerable to lead poisoning. According to Health Canada, lead levels are highest in immigrants and people with lower incomes. Many Indigenous communities are still dealing with drinking water that’s contaminated with lead, among other harmful substances.
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The Duke researchers are now looking at racial disparities in lead poisoning, as Black children were often exposed to more lead than white children.
Leaded gas is no longer used anywhere in the world — but that’s a very recent development. M
any low-income countries continued using leaded gas for decades, even after the risks were widely known. Algeria, the last country in the world to use leaded gas reserves, continued to use them until they finished them up this past July.
A 2011 study estimated that the phasing out of leaded gas has been the “single most important strategy” to end lead poisoning. They also found that it directly saved 1.2 million lives per year, including 125,000 children.
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“Millions of us are walking around with a history of lead exposure,” the Duke study’s co-author Aaron Reuben said.
“It’s not like you got into a car accident and had a rotator cuff tear that heals and then you’re fine. It appears to be an insult carried in the body in different ways that we’re still trying to understand but that can have implications for life.”
Maija Kappler is a reporter and editor at Healthing. You can reach her at [email protected]
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