Exposure to certain sources of pollution harms children’s learning and memory, research shows

A new USC study of 8,500 children from across the country has found that a form of air pollution, largely the product of agricultural emissions, is linked to poor learning and memory performance in 9- and 10-year-olds.

The specific component of fine particle air pollution (PM_2.5), ammonium nitrate, has also been implicated in the risk of Alzheimer’s and dementia in adults, suggesting that PM_2.5 can cause neurocognitive damage throughout the lifespan. Ammonium nitrate is formed when ammonia gas and nitric acid, produced by agricultural activities and the combustion of fossil fuels respectively, react in the atmosphere.

The findings appear in Environmental health perspectives.

“Our study highlights the need for more detailed research into sources of particulate matter and chemical components,” said senior author Megan Herting, associate professor of population and public health sciences at the Keck School of Medicine of USC. “It suggests that understanding these nuances is crucial for informing air quality regulations and understanding long-term neurocognitive effects.”

For the past several years, Herting has been working with data from the largest brain study across America, known as the Adolescent Brain Cognitive Development Study, or ABCD, to understand how PM_2.5 can affect the brain.

P.M_2.5: A danger to the lungs

P.M_2.5an important indicator of air quality, is a mixture of dust, soot, organic compounds and metals with a range of particle sizes less than 2.5 micrometers in diameter. P.M_2.5 can travel deep into the lungs, where these particles can enter the bloodstream and bypass the blood-brain barrier, causing serious health problems.

The combustion of fossil fuels is one of the largest sources of PM_2.5mainly in urban areas, but sources such as forest fires, agriculture, marine aerosols and chemical reactions are also important.

In 2020, Herting and her colleagues published a paper looking at PM_2.5 as a whole, and its potential impact on cognition in children, and found no association.

For this study, they used special statistical techniques to look at 15 chemical components in PM_2.5 and their sources. At that moment, ammonium nitrate – which is usually the result of farming and agricultural activities – appeared in the air as the main suspect.

“No matter how we examined it, alone or with other pollutants, the most robust finding was that ammonium nitrate particles were associated with poorer learning and memory,” Herting said. “That suggests that overall PM_2.5 is one thing, but for cognition it’s a mixed effect of what you’re exposed to.”

For their next project, the researchers hope to see how these mixtures and sources can tap into individual differences in brain phenotypes during child and adolescent development.