With every breath you take, you’re inhaling a lot more than just the oxygen your lungs crave. Particulate matter, sulfur dioxide, ozone—all pollutants known to damage the heart and lungs—probably enter your body, too.
New research suggests that the damage from pollution may go beyond the cardiac and respiratory systems. All this crappy air quality could also be messing up people’s brains, leading to a higher risk of depression, bipolar disorder, or schizophrenia.
A study published in PLOS Biology on Tuesday looked at populations in both the U.S. and Denmark. Among both cohorts, the authors found that poor air quality resulted in a roughly 29 percent increase in the rate of bipolar disorder. However, rates of depression and schizophrenia varied among the countries, which the authors attribute to the different data sets.
Denmark saw a frightening correlation between air quality and mental health that wasn’t nearly as strong in the U.S. data. For personality disorder, the correlation was strongest, with those breathing the worst air being 162 percent more likely to have personality disorder compared to those breathing the best air. Individuals living with the country’s worst air quality saw a 148 percent increase in the prevalence of schizophrenia compared to those living among the best air quality. Depression saw the smallest increase but still a dramatic 50 percent.
“The major takeaway is that the environment matters,” lead author Andrey Rzhetsky, a professor of medicine and genetics at the University of Chicago, told Earther. “And it’s involved in psychiatric disease.”
While this requires further analysis, the authors believe the brain could be exposed to pollutants in a number of ways. Either through direct inhalation from the nose that goes straight to the brain or perhaps indirect exposure when the pollutants enter the lungs. Either one may lead to systemic inflammation, the authors note. That’s never good.
“There are several ways in which pollutants can enter the brain,” Rzhetsky told Earther. “Once they are in the brain, they cause abnormal processes, such as inflammation.”
In order to explore the hypothesis that air pollution can cause these diseases, the team of scientists didn’t study actual human brains or subjects, which would be ideal to truly investigate this but is tricky because of, well, ethical and technical reasons. Instead, they looked at two data sets. The U.S. set was made up of health insurance claims from more than 150 million people between 2003 and 2013. The data included a single health snapshot for these individuals, but their individual health data was coupled with county-wide environmental data from the Environmental Protection Agency from this time period, including air quality and level of vehicle traffic.
For the Danish, however, the authors had individual health data, which included pollution exposure, for the more than 1.4 million individuals born between 1979 and 2003. The data only recorded pollution exposure, however, until age 10. That means that a person could only need to be exposed only during childhood to suffer psychiatry impacts as an adult.
Air pollution may only grow worse in a warmer world, which creates the perfect environment for ozone and smog to form. And the communities of color and low-income families who tend to live closest to polluters (at least in the U.S.) already face disproportionate health issues, as well as worse access to health care.
Rzhetsky hopes these findings help scientists focus more attention on the environmental causes of psychiatric disease. So far, the focus has been largely on genetic disposition, he said, which does play a role but can’t be prevented. Instead, by looking at what we can fix, perhaps science can find ways to better treat people living with these diseases.
We didn’t need more reasons to reduce air pollution. But it’s clear that breathing polluted air is bad for us in ways that go well beyond lung disease. So, can we finally address the crap spewing into our air and one day breathe easy?