More than 824 million IQ points were lost due to leaded gas.
To some outside the US, Americans are seen as ignorant, NASCAR-loving gun nuts that don't own passports and have a tenuous grip on the English language. The stereotype may be undignified, but a new peer-reviewed study by the National Academy of Sciences (NAS) suggests that half of American citizens aren't as smart as they used to be, and it's all because of leaded gasoline. The NAS study has found that half of the US population has been exposed to adverse levels of lead in their early childhood which in turn has led to a total loss of 824,097,690 IQ points since 2015.
The new study tries to estimate the amount of cognitive damage caused by leaded petrol in the US during the peak of the leaded fuel age from the 1960s to the early 1980s, finding that the blood-lead level (BLL) for the general US population was on average three to five times higher during that era.
Lead fuel was banned in the US in 1996, but there are still millions of adults who have been exposed to high levels of lead as children. High exposure to lead can disrupt the healthy development of certain organ systems, especially the brain, bone, and cardiovascular systems. In terms of brain function, high concentrations of lead exposure can affect one's cognitive ability, emotional regulation, and fine motor skills.
Using population estimates from 2015, the study found that of the 318 million people living in the US at the time, only 131 million people had BLLs below 5 micrograms per deciliter (the 2015 threshold for clinical concern) during their childhood years. Nearly 100 million people had childhood BLLs above 10 µg/dL - three times the level of concern in 2022. Worse still, approximately 10 million people had levels above 25 ug/dL. According to the NAS, this high level of lead exposure has led to an average loss of 2.6 IQ points per person. Those born between 1966 and 1970 suffered the highest impact, with an average loss of 5.9 IQ points per person.
Principal study author Michael McFarland, an associate professor of sociology at Florida State University has noted that the amount of people affected by lead exposure is "staggering."
"This is important because we often think about lead as an issue for children, and of course it is, but what we really wanted to know is what happens to those children who were exposed? If you're more toward cognitive impairment, a couple of points can mean a lot," he said.
Lead can be ingested or inhaled (usually through exhaust fumes). This neurotoxin was replaced by unleaded fuel in 1996 that made use of non-lead-based additives. Old-school Dodge Chargers were cool, but would you risk losing a few IQ points? Suddenly driving a Tesla Model 3 seems like a healthier option.