There’s a mental health crisis gestating among children and adolescents, and new evidence has suggested that exposure to air pollution could be one of many risk factor’s. In a recent study, researchers found that adolescents living in areas with relatively high levels of ozone experienced a significant increase in depressive symptoms, such as sadness, loneliness, and feelings of self-hatred.
“One of the things that is quite surprising to me is that we are seeing these effects over 2-year and 4-year periods.”
And this change in mental health can happen quite quickly, explained the study’s lead author, Erika Manczak, assistant professor of psychology at the University of Denver. “One of the things that is quite surprising to me is that we are seeing these effects over 2-year and 4-year periods.” Perhaps even more unexpected: All 213 study participants lived in neighborhoods where average ozone concentrations were below the National Ambient Air Quality Standards. “Although these were objectively low levels of average ozone exposure, we are seeing these effects.”
To conduct this study, Manczak and colleagues analyzed mental health data on children between the ages of 9 and 13 collected at various points over a 4-year period. They then compared these figures to air quality monitoring data that roughly corresponded to each participant’s home address. After accounting for a variety of composite factors, such as age, gender, and socioeconomic status, the researchers found that even slightly elevated ozone levels correlated with increased depressive symptoms over time.
“They were able to show really clean linear symptom trends in people exposed to high levels [of ozone] that are basically absent in people who are not exposed to high levels,” said Reuben Aaron, a postdoctoral fellow in neuropsychology at Duke University who was not involved in the study. “For people concerned with understanding people’s risk of depression, I think this paper adds a lot of new value.”
“Humans are messy subjects”
Scientists have long known that exposure to air pollution can cause a host of negative health impacts, but “for many years it was assumed that air pollution primarily damages the lungs,” Reuben explained. Even today, ozone is often said to contribute to lung problems like asthma and respiratory infections, “which happens, but then we realised: maybe it could also damage organ systems closely associated with the lungs.”
Turns out that includes the brain and the central nervous system. “It seems there are some evidence in animal models to suggest that exposure to ozone and other forms of pollution can affect the activity of various neurotransmitters, as well as stimulate the expression of inflammatory proteins in the brain,” Manczak explained.
All those things have been separate involved in the formation and development of mental disorders, said Omar Hahadpsychologist and researcher at the University Medical Center Mainz in Germany who was not involved in the study.
Animal-based research can tell scientists a lot. After all, depression in a rat will look very different than depression in a human. That’s why these findings are often used in conjunction with observational studies, like Manczak’s, to understand how these physiological mechanisms might affect people, especially vulnerable populations like children.
However, it is not a perfect science. For one, “humans are messy subjects,” Reuben explained. “Almost everything in human toxicology studies is going to be correlational.”
Other factors that researchers can’t easily control could also come into play. “In highly urbanized areas, there are more likely to be colocalizations of other environmental factors, such as exposure to noise, light, or temperatures, that we know affect mental health,” Hahad explained.
take precautionary measures
However, Manczak and colleagues’ research adds to the growing list of evidence highlighting the negative effect of air pollution on mental health. “I think replicating the study in a much larger sample and in different parts of the world would be a really important next step to help us get a little more confidence in these associations,” Manczak said.
Furthermore, more work is also needed to understand how different mixtures of pollutants can alter these effects. “We don’t know if the effects of these air pollutants are additive or synergistic,” Hahad said.
Despite these lingering questions, the public can still take precautionary measures, the researchers said. “I’m a really strong believer in paying attention to your local air quality and using that information to inform how you behave during the day,” Manczak said, whether it’s rescheduling outdoor activities on high-pollution days or put on N95 masks.
That said, individual efforts can only take us so far. “What is really missing [are] political actions to really address this problem,” Hahad said.
Ruben agreed. “Fundamentally, when we talk about air quality, water quality, the things that influence the health and longevity of all of us, it has to be a societal response. You just can’t do it alone.”
—Krystal Vasquez (@caffeinatedkrys), science writer
