It is generally understood that air pollution is bad for public health. Breathing dirty air has been associated with a multitude of adverse physical health effects, including respiratory infections, hearth disease and lung cancer. There is even some research to suggest it can lead to obesity, diabetes and dementia. But not all of its effects are physical.
A new study from the University of Washington (UW) has revealed that air pollution could also lead to psychological distress. When UW researchers cross-referenced the results of a nation-wide survey with pollution data, they found an important connection between air toxicity and mental health.
"This is really setting out a new trajectory around the health effects of air pollution," said Anjum Hajat, an assistant professor of epidemiology in the UW School of Public Health.
"The effects of air pollution on cardiovascular health and lung diseases like asthma are well established, but this area of brain health is a newer area of research."
The UW researchers began by looking at some 6,000 responses to a nation-wide survey that assessed psychological distress based on participants' feelings of sadness, nervousness and hopelessness. The researchers then examined the level of pollution in each respondent's neighborhood, using an air pollution database.
The team focused specifically on fine particulate matter, which is the same substance that is produced by car engines and coal-fired power plants. Fine particulate matter is generally considered more dangerous than larger particles because it is much easier to inhale. In fact, fine particulate matter is so tiny, it is 28 times smaller than the average human hair. So, most people have no idea when they are inhaling it.
The findings of the new study found psychological distress increased alongside the amount of fine particulate matter in the air. For instance, in areas with higher fine particulate matter in the air, psychological distress scores were 17 percent higher than in areas with lower fine particulate matter.
These results occurred even when the researchers controlled for other physical, behavioral and socioeconomic factors that can influence mental health, like chronic health conditions, unemployment and excessive drinking.
The recent study is supported by previous research that has found higher anxiety levels among those with greater exposure to fine particulate matter. Some studies have even found that at low levels, air pollution can increase the prevalence of mental illness in children.
Even still, more research is needed to determine exactly why mental health is affected by pollution.
One possible explanation is that people living in polluted areas change their behavior to avoid air pollution. These behavioral changes range from spending less time outside to leading a more sedentary lifestyle. And while these changes may help protect the public from unnecessary air pollution, they are also related to psychological distress and social isolation. But until more research is conducted, scientists won't know for sure.
The good news is that air pollution has a clear, actionable solution, and in the US, it has even been declining. Although it is important to note that it still kills thousands of people every year, even at the levels allowed by the Environmental Protection Agency (EPA), according to a study that was published earlier this year.
"We shouldn't think of this as a problem that has been solved," said primary author Victoria Sass, a graduate student in the Department of Sociology.
"There is a lot to be said for having federal guidelines that are rigorously enforced and continually updated. The ability of communities to have clean air will be impacted with more lax regulation."
But thanks to EPA administrator Scott Pruitt's new agenda, clean air regulations in the US are at risk. Recently, Pruitt announced that no scientist could serve on the EPA's Science Advisory Board if they received EPA grants. As a result, several scientists were dismissed from the clean air advisory board.
To fill the gaps, Pruitt appointed air pollution researcher Robert Phalen to the board. The decision was widely criticized because, in the past, Phalen has argued for softer air regulations. In 2012, Phalen even told the American Association for the Advancement of Science (AAAS) that contrary to scientific evidence, air pollution is good for children.
"Modern air," he said, "is a little too clean for optimum health."
The craziness doesn't stop there. In 2004, Phalen wrote a paper that claimed particulate matter is not as risky as scientists think.
"The relative risks associated with modern [particulate matter] are very small and confounded by many factors," Phalen wrote.
"Neither toxicology studies nor human clinical investigations have identified the components and/or characteristics of [particulate matter] that might be causing the health-effect associations."
The report stands in direct opposition to the EPA's website, which states that "the size of particles is directly linked to their potential for causing health problems."
With people like Phalen in charge of clean air regulations, who knows what the future of air pollution in the U.S. will look like.
The study was published in Health & Place.