Environmental pollution, toxic air in particular, is responsible for hundreds of thousands of deaths from acute lower respiratory infections, numerous premature deaths and, according to the World Health Organization, it routinely puts children at greater risk for chronic diseases.
But high levels of air pollution can also hurt our brains, our cognitive abilities and our overall mental well-being.
In fact, a new study published Tuesday in the journal PLoS Biology found that among more than 100 million individuals in the United States and Denmark, poor air quality was associated with an increased risk of both major depression and bipolar disorder.
“These neurological and psychiatric diseases—so costly in both financial and social terms—appear linked to the physical environment, particularly air quality,” study author and computational biologist Atif Khan said in a statement.
Khan, senior author Andrey Rzhetsky and their University of Chicago colleagues first dug into a database of 151 million Americans with 11 years of inpatient and outpatient claims for neuropsychiatric diseases, mental disorders typically attributed to diseases originating from the nervous system that impair one’s ability to learn, work or emotionally cope.
The researchers compared the medical claims with the air quality of their respective geographies. Khan and his team measured 87 different air pollutants (pulled from the Environmental Protection Agency) and found that compared to places with the best air quality, areas with the worst air quality had a 27% increase in rates of bipolar disorder and a 6% increase in rates of major depression.
They also noted a “strong association between polluted soil and an increased risk of personality disorder,” according to a university article.
To further validate these “unusually strong” correlations, the UChicago researchers collaborated with Danish scientists in an analysis of 1.4 million people born in Denmark between 1979 and 2002. Compared to areas with the best air quality, Danish counties with the worst air quality saw a 29% increase in rates of bipolar disorder. Early childhood exposure to air pollution in Denmark was also associated with a 50% increase in major depression, a 148% increase in schizophrenia and a 162% increase in personality disorders. The numbers more than mirrored those in the U.S.
That doesn’t mean the scientific community can now confirm pollution actually triggers the aforementioned diseases and disorders. What we do know, according to the study, is that “growing evidence from human, animal, and in vitro studies demonstrates that airborne pollutants target the brain and are implicated in neurological and psychiatric disorders etiology.” But more work is needed to examine how environmental factors are linked to neuropsychiatric conditions.