A new USC study of 8,500 children from across the country finds 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 particulate air pollution, or PM2.5, ammonium nitrate, has also been implicated in the risk of Alzheimer’s and dementia in adults, suggesting that PM2.5 can cause neurocognitive damage across 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.”
Megan Herting, associate professor of population and public health sciences, Keck School of Medicine, University of Southern California
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 PM2.5 can affect the brain.
PM2.5, a key 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. PM2.5 can travel deep into the lungs, where these particles can enter the bloodstream and bypass the blood-brain barrier, causing serious health problems.
Fossil fuel combustion is one of the largest sources of PM2.5, especially 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 PM2.5 as a whole, and its potential impact on cognition in children, but found no link.
For this study, they used special statistical techniques to investigate 15 chemical components in PM2.5 and their sources. That’s when ammonium nitrate -; which is usually the result of farming and agricultural activities -; appeared in the sky 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 PM2.5 is one thing in general, but for cognition it’s a mixture 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.
In addition to Herting, other authors of the study include Rima Habre, Kirthana Sukumaran, Katherine Bottenhorn, Jim Gauderman, Carlos Cardenas-Iniguez, Rob McConnell and Hedyeh Ahmadi, all of the Keck School of Medicine; Daniel A. Hackman of the USC Suzanne Dworak-Peck School of Social Work; Kiros Berhane of Columbia University Mailman School of Public Health; Shermaine Abad of the University of California, San Diego; and Joel Schwartz of the Harvard TH Chan School of Public Health.
Source:
Magazine reference:
Sukumaran, K., et al. (2024) Associations between particulate matter components, their sources, and cognitive outcomes in 9–10 year old children from the United States. Environmental health perspectives. doi.org/10.1289/ehp14418.