The researchers used data on blood lead level, census population and consumption of leaded gasoline to examine the prevalence of lead exposure in early childhood between 1940 and 2015.
In a paper published in the Proceedings of the National Academy of Sciences on Monday, researchers report that half of the US adult population in 2015 were exposed to lead levels exceeding 5 micrograms per deciliter, which represents the threshold set by the Centers for Disease Control and Prevention, for harmful exposure to lead in that. the time.
Scientists from Florida State University and Duke University also discovered that 90 percent of children born in the United States between 1950 and 1981 had blood lead levels above the CDC threshold.
The researchers found a significant impact on cognitive development, with lead exposure in early childhood leading to a 2.6 point drop in IQ, on average.
The researchers only examined lead exposure from leaded gasoline, the dominant form of exposure from the 1940s to the late 1980s, according to USGS data.
Leaded vehicle gasoline was phased out beginning in the 1970s and finally banned in 1996.
Study lead author Michael MacFarland, associate professor of sociology at Florida State University, said the study’s findings were “outrageous” because it has long been known that lead exposure is harmful, based on anecdotal evidence 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 lead exposure could persist for decades, experts told The Associated Press.
“Childhood lead exposure is not just here and now. It will affect your health for life,” said Abhit Suleiman, director of programs at the United Nations Children’s Fund.
Experts say it is known that exposure to lead in early childhood has many effects on cognitive development, but it also increases the risk of high blood pressure and heart disease.
“I think the association with IQ is greater than we thought, and it’s amazingly large,” said Ted Schwaba, a researcher at the University of Texas Austin who studies personality psychology and was not involved in the new study.