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The researchers used data on blood lead levels, censuses and leaded gasoline consumption to examine the extent of lead exposure among young children in the country between 1940 and 2015.
In a paper published Monday in the Proceedings of the National Academy of Sciences, they estimated that half of the adult American population in 2015 had been exposed to levels of lead exceeding five micrograms per deciliter – the threshold for harmful exposure to lead. lead from the Centers for Disease Control and Prevention. at the time.
Florida State University and Duke University scientists also found that 90% of children born in the United States between 1950 and 1981 had blood lead levels above the CDC threshold. And the researchers found a significant impact on cognitive development: on average, exposure to lead in early childhood led to a 2.6-point drop in IQ.
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The researchers only looked at lead exposure from leaded gasoline, the dominant form of exposure from the 1940s through the late 1980s, according to data from the US Geological Survey. Leaded gasoline for road vehicles was phased out beginning in the 1970s and finally banned in 1996.
The study’s lead author, Michael McFarland, an associate professor of sociology at Florida State University, said the results were “infuriating” because lead exposure has long been known to be harmful, based on evidence anecdotal accounts of the health effects of lead throughout history.
Although the United States has implemented stricter regulations to protect Americans from lead poisoning in recent decades, the public health effects of exposure could last for decades, experts told the Associated Press.
“Lead exposure in children is not just here and now. It will impact your health throughout life,” said Abheet Solomon, senior program officer at the United Nations Development Fund. childhood.
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Lead exposure in early childhood is known to have many impacts on cognitive development, but it also increases the risk of developing hypertension and heart disease, experts have said.
“I think the connection to IQ is bigger than we thought, and it’s surprisingly big,” said Ted Schwaba, a researcher at the University of Texas-Austin who studies personality psychology and wasn’t one of the new study.
Schwaba said the study’s use of an average to represent the cognitive impacts of lead exposure could result in the impacts being overestimated on some people and underestimated on others.
Previous research on the relationship between lead exposure and IQ found a similar impact, but over a shorter study period.
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Bruce Lanphear, a professor of health sciences at Simon Fraser University in Vancouver who has researched lead exposure and IQ, said his 2005 study found that initial exposure to lead was most harmful in terms of loss of cognitive ability as measured by IQ.
“The most tragic part is that we keep making the same…mistakes,” Lanphear said. “First it was lead, then air pollution. … Now it’s PFAS chemicals and phthalates (chemicals used to make plastics more durable). And it goes on and on.
“And we can’t stop long enough to wonder if we should regulate chemicals differently,” he said.
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