Living in a polluted area as a pre-teen and teenager may have long-lasting, detrimental effects on a person’s ability to reason and problem solve, a new study suggests.
Researchers at the University of Southern California and UCLA Center for Health Policy Research tracked more than 1,300 pre-teens living in neighborhoods across Los Angeles and surrounding counties over a 12-year period. They tested the teens’ IQ levels at ages 9 to 11, and in young adulthood between ages 18 to 20.
The scientists then used EPA data to retroactively calculate air pollution levels around the homes where the teens lived. They focused on fine-particle pollution, which comes from cars, power plants and other sources. These particles are about 30 times smaller than the width of a human hair, and can pass into the lungs and blood stream.
For every increase of 2.5 micrograms per cubic meter in the fine-particle pollution level surrounding the teens’ homes, their performance IQ score dropped 1 point, the researchers found.
Performance IQ measures reasoning and problem-solving abilities. It’s different from verbal IQ, which represents the capacity to acquire new skills and knowledge, and was not significantly impacted by pollution levels.
“Verbal IQ is something you can learn and once you learn, you know that for your lifetime. But performance IQ is about your ability to solve new questions, new problems … That’s more controlled by your brain function,” said Pan Wang, a UCLA statistician involved in the study.
“The findings from this study indicate the adverse effects of air pollution are at a higher level in the brain,” Wang said. Air pollution “may have adverse effects on the brain structure or brain function.”
Most teens in the study were exposed to air pollution levels above Environmental Protection Agency (EPA) air quality standards of 12 micrograms per cubic meter, the study said.
Air pollution did not affect teens equally. Poorer teens saw a 150 percent greater drop in performance IQ than wealthier teens, even after accounting for different socioeconomic circumstances and parental intelligence, the study found. Also, boys were significantly more likely than girls to experience adverse effects from air pollution.
What’s causing these differences isn’t clear. Wang said wealthier families may be better equipped to compensate for children’s IQ loss through access to good education and parenting know-how. The gender difference also fits with previous studies that show boys are more sensitive to contaminants than girls during the puberty phase, said senior study author, USC professor Jiu-Chiuan Chen.
Lower IQ is tied to reduced-earning power over a person’s lifetime, as well as poorer mental and physical health, Wang said.
This has an effect for society as a whole, she said. Just a 1-point drop in IQ level among a portion of the population can result in billions of dollars in losses to the U.S. economy, previous studies have estimated.
The Trump administration’s efforts to roll back air pollution regulations could make the situation worse, Wang added.
Chen said more must be done to reduce air pollution.
“I think our study adds to growing evidence that the neurotoxicity of air pollution decreases the nation’s mental capital,” he said. “For anyone who wants to help America succeed in the global competition of the knowledge economy, relaxing the air pollution regulations will very likely do the opposite.”
Bill Magavern, policy director for the Coalition for Clean Air, an advocacy group pushing for stronger air pollution regulations across California, said the study findings are alarming but consistent with other scientific studies that show air pollution from fine-particulate matter is especially damaging to people’s health.
He said all levels of government must act more boldly to reduce air pollution with the goal of eventually eliminating combustion of fossil fuels. He applauded Gov. Jerry Brown’s recent executive order to put five million zero-emission cars on the roads by 2030.
“California has the best standards in the country to address this problem, but we also have the worst air pollution because of our geography and our population,” Magavern said.
“We need to be the leader in the country, and we need to push further, both with what we can do with the state and regional level, and also trying to get the cooperation of the federal government.”