Over 170 million U.S.-born people who were adults in 2015 were exposed to harmful levels of lead as children, a new study estimates.
And the researchers found a 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 on-road vehicles was phased out starting in the 1970s, then finally banned in 1996.
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 told the Associated Press. "I think the connection to IQ is larger than we thought and it's startlingly large," said Ted Schwaba, a researcher at the University of Texas-Austin who studies personality psychology and was not part of the new study.
Previous research on the relationship between lead exposure and IQ found a similar impact, though 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 the initial exposure to lead was the most harmful when it comes to loss of cognitive ability as measured by IQ.