According to their report, exposure to car exhaust from leaded gas may be responsible for the loss of nearly 825 million IQ points for more than 170 million Americans.
“I frankly was shocked,” said researcher Michael MacFarland. “And when I look at the numbers, I’m still shocked even though I’m prepared for it.”
Risks to long-term brain health
To better understand how exposure to lead may affect consumers’ cognitive function, the researchers analyzed data from the National Health and Nutrition Examination Survey, the Human Mortality Database, the U.S. Census, and the United Nations. The team tracked how exposure to leaded gasoline impacted the IQ of all Americans who were alive in 2015.
The researchers explained that trends related to leaded gas versus unleaded gas greatly influenced these results. Though leaded gas was banned in the U.S. in 1996 because of health concerns, it was the primary form of gasoline throughout the 1970s. Because of this, the study showed that those who grew up between the 1960s and 1970s were the most affected by this type of lead exposure.
This study showed that consumers born in that timespan had high levels of lead in their blood as children. The researchers believe this is likely the reason for the drop in IQ points. This lead exposure is also concerning from a health perspective, as it is likely responsible for higher risks of cardiovascular disease, mental health concerns, and reduced brain size.
“Lead is able to reach the bloodstream once it’s inhaled as dust, or ingested, or consumed in water,” said researcher Aaron Reuben. “In the bloodstream, it’s able to pass into the brain through the brain-blood barrier, which is quite good at keeping a lot of toxicants and pathogens out of the brain, but not all of them.”
Loss of up to 7 IQ points
Overall, the researchers learned that consumers born in the mid-to-late 1960s saw their IQs drop by an average of three points per person. In total, there were nearly 825 million lost IQ points. The team estimated that those with the highest levels of lead in their blood may have lost up to seven IQ points.
While these findings are certainly a cause for concern, the researchers want to do more work in this area to better understand the long-term risks of lead exposure during childhood.
“Millions of us are walking around with a history of lead exposure,” Reuben said. “It’s not like you got into a car accident and had a rotator cuff tear that heals and then you’re fine. It appears to be an insult carried in the body in different ways that we’re still trying to understand but that can have implications for life.”