The IQ of more than half of the American population may have been lowered by leaded gasoline


Exposure to leaded gasoline during childhood has been linked to an average drop in IQ of 2.6 points in American adults, dropping to 5.9 points in those born in the mid to late 1960s.


March 7, 2022

Fumes from cars using leaded gasoline can affect IQ

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More than half of people in the United States may have a slightly lower IQ as a result of inhaling the exhaust fumes of vehicles running on leaded gasoline as children. The damage is thought to be most pronounced in people born in the 1960s and 1970s, when the use of this fuel was at its peak.

Similar effects have likely occurred in other high-income countries, says Aaron Reuben of Duke University in North Carolina. “Patterns of lead use in gasoline over the past century were very similar in developed countries.”

Lead began to be added to gasoline in the 1920s to improve the operation of car engines. If the substance enters the brain, it can disrupt nerve signaling and, at higher levels, kill brain cells. Young children are especially susceptible due to the metal disrupting brain development.

Using data from a national survey, Reuben and his colleagues analyzed the circulating lead levels of more than 11,600 children aged 1 to 5 from blood samples taken between 1976 and 2016. They also estimated blood lead levels for the period from 1940 to 1975 based on lead gasoline consumption during that time. This data was then linked to an established formula of how lead exposure influences IQ.

Their findings suggest that half of the current US population had elevated blood lead levels as children. Nationwide, they estimate that lead exposure may have caused an average drop in IQ of 2.6 points. People born in the mid to late 1960s may have lost an average of 5.9 points.

In the 1970s, it was recognized that tiny lead particles in car exhaust could enter people’s bloodstreams and that higher environmental levels of the metal were linked to poorer school performance in children.

Leaded gasoline was banned in road vehicles in the United States in 1996 and in the United Kingdom in 2000. The latest study demonstrates the lingering effects of certain environmental toxins, says Mathew Hauer of Florida State University, who participated to the works. “The long legacy is really important. The effects can last a long time. This could be the case with other toxins.

Journal reference: PNASDOI: 10.1073/pnas.2118631119

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