Using blood lead levels, census data and data on leaded gasoline use, the researchers examined the prevalence of early childhood lead exposure 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 US adult population was exposed to levels of lead in 2015 greater than five micrograms per deciliter — the Centers for Disease Control and Prevention threshold for lead harmful lead exposure at that time.
The researchers from Florida State University and Duke University also found that 90% of children born in the United States between 1950 and 1981 had blood lead levels above the CDC limit. And the researchers found a significant impact on cognitive development: On average, exposure to lead in early childhood resulted in a 2.6-point drop in IQ.
The researchers looked only at lead exposure from leaded gasoline, which was the predominant 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 from the 1970s and finally banned in 1996.
The study’s lead author, Michael McFarland, associate professor of sociology at Florida State University, said the results were “disturbing” because it has long been known that lead exposure is harmful, based on anecdotal evidence of the health effects of exposure to lead course of history.
Although the US has introduced stricter regulations to protect Americans from lead poisoning in recent decades, the public health effects of exposure could last for several decades, experts told the Associated Press.
“Childhood lead exposure is not just here and now. It will affect your health throughout your life,” said Abheet Solomon, a senior program manager at the United Nations Children’s Fund.
Early childhood lead exposure is known to have many effects on cognitive development, but it also increases the risk of developing high blood pressure and heart disease, experts said.
“I think the connection to IQ is bigger than we thought, and it’s amazingly strong,” said Ted Schwaba, a researcher at the University of Texas-Austin who studies personality psychology and was not part of the new study.
Schwaba said that using an average in the study to represent the cognitive effects of lead exposure could result in overestimating the effects for some people and underestimating for others.
Previous research into the association between lead exposure and IQ found similar effects, albeit over a shorter study period.
Bruce Lanphear, a health sciences professor at Simon Fraser University in Vancouver who has researched lead exposure and IQ, said his 2005 study found that initial lead exposure was most harmful when it came to loss of cognitive ability, measured by IQ, went.
“The more 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 that make plastics more durable). And it goes on and on.
“And we can’t stop long enough to ask ourselves if we should regulate chemicals differently,” he said.
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https://abc13.com/lead-exposure-levels-leaded-gasoline-poisoning/11630739/ Lead Exposure: The study estimates that half of US adults were exposed to harmful levels of lead as children