Study Finds Exhaust From Leaded Gasoline Shrank IQs For At Least Half Of U.S. Adults


A new study claims that children exposed to car exhaust from leaded gasoline has actually ‘stolen a collective 824 million IQ points from more than 170 million Americans’ that are still alive today. Alarmingly, this number is almost half of the current US population.

Apparently lead poisoning isn’t a problem just for kids that happen to get exposed to chipped lead-based paint on older toys, or from contaminated drinking water. The new study shows that a number of middle-aged and older adults have been experiencing cognitive problems currently due to breathing in car exhaust from leaded gasoline as children.

Beginning 1923, most vehicles on the road used leaded gas back when it was first being added to gasoline in order keep car engines healthy. But by 1996, it was banned within the United States after it was linked to widespread cognitive damage in the younger population.

To get the proper data for the new study, researchers used information on leaded-gas use, childhood blood-lead levels, and population trends in order to estimate the lifetime amount of lead exposure for all Americans alive in 2015.

According to study results that were reported in the Proceedings of the National Academy of Sciences, they found that on average, childhood lead exposure cut their IQ scores by at least 3 points.


Highest Leaded Gasoline Use Was Tied to Effects in the 60’s and 70’s

The study found that leaded gasoline usage hit its highest in the United States during the 1960s and 1970s, which also meant that the damage was doubled. During this time, the typical levels of childhood lead exposure ended in an average reduction of IQ scores by at least six points, sometimes even higher reduction of IQ scores to those with the highest levels of lead exposure.

Associate professor of sociology at Florida State University in Tallahassee, and lead author of the study, Michael McFarland, PhD, said “I frankly was shocked.”


In Cognitive Classification, Every IQ Point Matters

When it comes to cognitive classification, a few IQ points could make a huge difference. By losing a few IQ points, it could make someone with an average cognitive ability – classified by IQ scores of 85 to 115 – and bring them below average. Researchers also point out that it could also mean that if someone already has below average scores without any lead exposure, they would end up shifting to an intellectually disabled classification, or an IQ score of below 70, if they were to get lead poisoning.

According to the Centers for Disease Control and Prevention (CDC), there is no safe level of lead exposure. Moreover, lead poisoning causes a variety of serious, lasting health conditions such as attention deficits, reduced brain size, lower IQ, and a heightened risk of cardiovascular disease and mental illness.

Although young children are especially vulnerable since their brains are still developing, the study team notes that lead exposure can negatively impact people of any age.

Clinical psychology researcher at Duke University in Durham, North Carolina, senior study author Aaron Reuben, “Lead is able to reach the bloodstream once it’s inhaled as dust, or ingested, or consumed in water.”

He adds, “In the bloodstream, it’s able to pass into the brain through the blood-brain barrier.”

When lead reaches the brain, the adverse effects can linger for decades. A 2020 published study in JAMA even found that ‘middle-aged adults with childhood lead exposure had significantly smaller brains with less structural integrity, conditions that may accelerate brain aging and lead to premature cognitive decline.’

Reuben adds, “Millions of us are walking around with a history of lead exposure. 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.”