By Drew Costley
The Associated Press
More than 170 million U.S.-born people who were adults in 2015 were exposed to harmful levels of lead as children, a new study estimates.
Researchers used blood-lead level, census and leaded gasoline consumption data to examine how widespread early childhood lead exposure was in the country between 1940 and 2015.
In a paper published in the Proceedings of the National Academy of Sciences on Monday, they estimated half the U.S. adult population in 2015 had been exposed to lead levels surpassing five micrograms per deciliter — the Centers for Disease Control and Prevention threshold for harmful lead exposure at the time.
The scientists from Florida State University and Duke University also found that 90% of children born in the U.S. between 1950 and 1981 had bloodlead levels higher than the CDC threshold. And the researchers found significant impact on cognitive development: on average, early childhood exposure to lead resulted in a 2.6-point drop in IQ.
The researchers only examined lead exposure caused by leaded gasoline, the dominant form of exposure from the 1940s to the late 1980s, according to data from the U.S. Geological Survey. Leaded gasoline for onroad vehicles was phased out starting in the 1970s, then finally banned in 1996.
Study lead author Michael McFarland, an associate professor of sociology at Florida State University, said the findings were “infuriating” because it was long known that lead exposure was harmful, based on anecdotal evidence of lead’s health impacts throughout history.
Though the U.S. has implemented tougher regulations to protect Americans from lead poisoning in recent decades, the public health impacts of exposure could last for several decades, experts said.
“Childhood lead exposure is not just here and now. It’s going to impact your lifelong health,” said Abheet Solomon, a senior program manager at the United Nations Children’s Fund.
Early childhood lead exposure is known to have many impacts on cognitive development, but it also increases risk for developing hypertension and heart disease, experts said.
“I think the connection to IQ is larger than we thought and it’s startlingly large,” said Ted Schwaba, a researcher at University of Texas-Austin who studies personality psychology and was not part of the new study.