A new USC study involving 8,500 children from across the country has revealed 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 (PM2.5), ammonium nitrate, is also implicated in Alzheimer’s and dementia risk in adults, suggesting that PM2.5 may cause neurocognitive harm across the lifespan. Ammonium nitrate forms when ammonia gas and nitric acid, produced by agricultural activities and fossil fuel combustion, respectively, react in the atmosphere.

The findings appear in Environmental Health Perspectives.

“Our study highlights the need for more detailed research on particulate matter sources and chemical components,” said senior author Megan Herting, an 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 last 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 may affect the brain.

PM2.5: A danger to the lungs

PM2.5, a key indicator of air quality, is a mixture of dust, soot, organic compounds and metals that come in a range of particle sizes less than 2.5 micrometers in diameter. PM2.5 can travel deep into the lungs, where these particles can pass into 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 like wildfires, agriculture, marine aerosols and chemical reactions are also important.

In 2020, Herting and her colleagues published a paper in which they looked at PM2.5 as a whole, and its potential impact on cognition in children, and did not find a relationship.

For this study, they used special statistical techniques to look at 15 chemical components in PM2.5 and their sources. That’s when ammonium nitrate — which is usually a result of agricultural and farming operations — in the air appeared as a prime suspect.

“No matter how we examined it, on its own or with other pollutants, the most robust finding was that ammonium nitrate particles were linked to poorer learning and memory,” Herting said. “That suggests that overall PM2.5 is one thing, but for cognition, it’s a mixture effect of what you’re exposed to.”

For their next project, the researchers hope to look at how these mixtures and sources may map on to individual differences in brain phenotypes during child and adolescent development.

In addition to Herting, other study authors 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 the Columbia University Mailman School of Public Health; Shermaine Abad of University of California, San Diego; and Joel Schwartz of the Harvard T.H. Chan School of Public Health.

The research was supported by grants from the National Institutes of Health [NIEHS R01ES032295, R01ES031074, P30ES007048] and the Environmental Protection Agency [RD 83587201, RD 83544101].

Vice President Kamala Harris’ proposal to expand Medicare to cover the costs of long-term care at home, plus vision and hearing benefits for seniors, made only a modest splash in the news. But it caught the attention of USC’s Julie Zissimopoulos, who studies the cost of dementia and the toll it takes on family members caring for persons living with dementia including those of the “sandwich generation” — adults caring for both their kids and aging parents.

Zissimopoulos, a professor at the USC Price School of Public Policy and a senior scholar at the USC Schaeffer Institute for Public Policy & Government Service, recently sat down with USC News to discuss Harris’ proposal ahead of November’s Alzheimer’s Disease Awareness Month.

What would be the impact of Harris’ proposal on families touched by Alzheimer’s or dementia?

Zissimopoulos: It would have a profound impact. People with Alzheimer’s and other dementias require help and support that changes over time. It may be 20 hours or so per week in early stages of disease, but as disease progresses, people with dementia often require around-the-clock care. Most of this is provided by family members. It is very expensive to hire a home health aide, and it is not a service currently reimbursed by Medicare.

We estimate that there are around 12 to 13 million persons caring for a family member with dementia, and that number will rise as the number of people living well into their 80s continues to grow. So that is an enormous amount of people who are impacted, and these numbers are for caring for persons with Alzheimer’s and dementia. That’s not counting caregiving for people with other conditions.

Harris’ proposal also includes coverage for vision and hearing loss. Why is that important?

Zissimopoulos: Many persons, as they age, suffer from hearing and vision loss. And there’s new evidence emerging around the relationship between hearing loss and dementia. It may be that if you can correct the hearing loss, you might actually be able to reduce or slow cognitive decline.

The proposal has been criticized as being too expensive. Your research shows that unpaid care by family members is indeed expensive, in ways that are largely hidden from the public.

Zissimopoulos: A lot of this unpaid care is provided by adult children, and many are in the prime of their working lives, so leaving the labor force has immediate as well as long-term financial consequences.

LEARN MORE

Read about Julie Zissimopoulos’ effort to build a dementia cost-of-care “calculator.”

Returning to the labor force is not always successful or at the same level of salary that you were earning before you left; your Social Security earnings accumulation and your savings for retirement through, for example, 401(k) contributions take a hit. And we know from many prior studies that not only are there financial implications of caregiving, but there are health and psychological implications.

The costs to individuals, their families and society are enormous. So [the proposal] is about what we, as a society, are willing to spend money on and who will pay for it. Right now, families are paying for it.

Windblown dust from the shrinking Salton Sea harms the respiratory health of children living nearby, triggering asthma, coughing, wheezing and disrupted sleep, USC research shows.

The findings also indicate that children living closest to the sea, who are exposed to more dust in the air, may be the most affected.

The study, published in Environmental Research, found that 24% of children in the area have asthma — far higher than the national rate of 8.4% for boys and 5.5% for girls. The abnormally high rate raises health experts’ concerns about the children’s health in this predominantly low-income community of color 150 miles southeast of Los Angeles.

Furthermore, experts say, the dust problem is likely to intensify in a hotter climate, with evaporation exposing more and more of the lake bed, or playa, leading to more dust events.

Salton sea and health: Conservation efforts making problem worse

Ironically, successful water conservation efforts are compounding the problem. As state conservationists reduce the agricultural runoff that flows into the Salton Sea, the lake is slowly disappearing. A combination of development and lithium mining may promise more economic opportunities — and an increase in truck traffic likely to kick up more dust and further aggravate respiratory health issues.

“These rural environmental justice communities are facing health consequences due to local dust events,” said first author Jill Johnston, an associate professor of environmental health at USC. “The agricultural industry in Imperial Valley has used excessive amounts of water, but one of the impacts of water conservation is the shrinking of the sea.”

The Salton Sea was created by accident in 1905 by a canal system breach. Until recently, the sea was sustained largely by irrigation runoff from adjacent farmland. Over the past two decades, however, the decreasing waterflow has exposed 16,000 new acres of playa — and a lot of dust. Saline lake beds typically contain various harmful particulates — sulfate, chloride, pesticides and toxic metals such as arsenic, lead and chromium.

To better understand the relationship between airborne dust and respiratory health, researchers recruited 722 school-age children from the predominantly Latino/Hispanic community between 2017 and 2019. Parents and guardians completed a 64-item survey about their child’s health history of the previous 12 months, including episodes of asthma, a daily cough for three months in a row, congestion or excess phlegm for three months in a row.

Researchers then used data from a network of regulatory air monitors to estimate exposures to “dust events” in which hourly concentrations of dust exceeded 150 micrograms per cubic meter. The monitors measure levels of particulate matter in the air, including PM2.5 particles (typically from traffic and combustion) and the larger PM10 particles (typically dust and soil).

How far away: Salton Sea and health

The researchers also calculated the distance from the child’s home and the edge of the Salton Sea. Participants living within 7 miles of the sea were considered “close” for the analysis.

The research showed that dust events had a greater impact on wheezing and sleep disturbances among children living closest to the sea. In addition, each deviation increase from the average, annual fine PM2.5 measure resulted in a 3.4 and 3.1 percentage point increase in wheezing and bronchitis symptoms, respectively.

“The community has long suspected that air pollution near the sea may be impacting children’s health,” Johnston said, “but this is the first scientific study to suggest that children living close to the receding shoreline may experience more severe direct health impacts. Protecting public health should be integrated into the mitigation plans.”

In addition to Johnston, other authors included Shohreh Farzan, Elizabeth Kamai, Dayane Dueñas Barahona and Sandrah Eckel, all of USC; Christopher Zuidema and Edmund Seto of the University of Washington; and Luis Olmedo, Esther Bejarano and Christian Torres of Comité Civico del Valle, an Imperial Valley community-based organization.

This work was supported in part by R01ES029598 and 5P30ES007048-21S1 grants from the National Institute of Environmental Health Sciences.