Researchers at the University of California, Davis, have found a link between traffic-related air pollution and an increased risk for changes in brain development relevant to neurodevelopmental disorders. Their study, based on rodent models, corroborates previous epidemiological evidence showing this association.

While air pollution has long been a concern for pulmonary and cardiovascular health, it has only been within the past decade that scientists have turned their attention to its effects on the brain, said UC Davis toxicologist Pamela Lein, senior author of the study, recently published in an open-access paper in Translational Psychiatry.

Researchers had previously documented links between proximity to busy roadways and neurodevelopmental disorders such as autism, but preclinical data based on real-time exposures to traffic-related air pollution was scarce to nonexistent.

Lein worked with UC Davis atmospheric scientist Anthony Wexler and first author Kelley Patten, a doctoral student in the UC Davis graduate group for pharmacology and toxicology, to develop a novel approach to study the impacts of traffic-related air pollution in real time. They set up a vivarium near a traffic tunnel in Northern California so they could mimic, as closely as possible, the experience of humans in a rodent model.

The researchers compared the brains of rat pups exposed to traffic-related air pollution with those exposed to filtered air. Both air sources were drawn from the tunnel in real time.

They found abnormal growth and increased neuroinflammation in the brains of animals exposed to air pollution. This suggests that air pollution exposure during critical developmental periods may increase the risk for changes in the developing brain that are associated with neurodevelopmental disorders.

What we witnessed are subtle changes. But we are seeing these effects using air pollution exposures that fall within regulatory limits. With the backdrop of other environmental and genetic risk factors in humans, this may have a more pronounced effect. This exposure also contains very fine particulate matter that isn’t currently regulated.

—Kelley Patten

In a separate study, Patten extended this exposure for 14 months to look at longer-term impacts of traffic-related air pollution and is in the process of writing up those results.

The team is also interested in what component of traffic-related air pollution is driving the neurodevelopmental outcomes.

If they can identify the culprits, Lein said, then scientists can approach legislators to develop scientifically based regulations to protect the developing human brain.

UC Davis atmospheric scientist and co-author Keith Bein said that the single most challenging aspect of studying the health effects of air pollution may be replicating how, when and what people are exposed to throughout their lifetimes.

Tackling this requires creative thinking and a multidisciplinary team of researchers, including exposure engineers, atmospheric scientists, toxicologists, biologists, behaviorists and animal care specialists.

Other study co-authors include: Eduardo González and Anthony Valenzuela, UC Davis School of Veterinary Medicine; Elizabeth Berg, UC Davis School of Medicine; Christopher Wallis, UC Davis Air Quality Research Center; Joel Garbrow, Washington University; and Jill Silverman at the UC Davis MIND Institute and School of Medicine.

The study was supported by the National Institutes of Health.

Resources

• Patten, K.T., González, E.A., Valenzuela, A. et al. (2020) “Effects of early life exposure to traffic-related air pollution on brain development in juvenile Sprague-Dawley rats.” Transl Psychiatry 10, 166 doi: 10.1038/s41398-020-0845-3