Research Determines Link Between Air Pollution and Mental Illness; Millions of Americans at Risk, Kids Especially Vulnerable

Western Pennsylvania has some of the worst air quality in the nation:

• Allegheny County (which encompasses Clairton and Pittsburgh) has only achieved full compliance with federal air quality standards once in its entire history—in 2020, when COVID-19 related shut-downs reduced emissions;
• Despite that reduction in emissions, residents still experienced an average of one day a week of unhealthy air in 2020;
• The region consistently receives “F” grades for air quality from the American Lung Association;
• Allegheny County is in the top 2% of all U.S. counties for cancer risk from air pollution;
• Local elementary schools near polluting facilities experience childhood asthma rates as high as 30%—more than triple the national average of 8% and the state average of 10%;
• Climate change is driving extreme weather events in the region that will heighten the risk of air pollution exposure.
• Air pollution isn’t just an urban problem; many rural parts of western Pennsylvania also experience air pollution from the oil and gas industry.

In addition to its air pollution problems, the region also bears a substantial burden of mental illness. New research indicates that childhood exposure to air pollution can impact our mental health as adults, and links spikes in air pollution with more emergency room visits for mental illness among children. Meanwhile, western Pennsylvania communities with the highest level of air pollution often face other hardships that negatively impact mental health—like poverty, crime, and racism—while lacking access to mental health resources.

“Scientists used to assume that air pollution primarily impacted the lungs,” Aaron Reuben, a researcher and PhD candidate in clinical psychology at Duke University, told EHN. “Eventually we learned it impacts the heart, too. Now we’ve realized that air pollution impacts every organ system we’ve looked at, including the brain.”

The mental health burden of air pollution

View of U.S. Steel Edgar Thompson Works from Eighth Street and Halket Street in Braddock, PA. (Credit: Njaimeh Njie)

In April, Reuben published a groundbreaking study on air pollution and mental health that was more than two decades in the making.

It found that the more air pollution people were exposed to as children, the more likely they were to experience mental illness when they turned 18—the age when initial symptoms often appear.

Rather than focus on a specific diagnosis like most previous studies, the researchers looked at study participants’ responses to detailed survey questions about many symptoms including dependence on alcohol, cannabis, and tobacco; antisocial behavior; eating disorders; depression; anxiety; post-traumatic stress; and delusions and hallucinations.

“Assessing symptoms gives us more information about how many different symptoms people are having and at what level of severity,” Reuben said.

Related: How contaminated water contributes to mental illness

“The idea that there’s a specific disorder people get with an on or off switch is really outdated,” he added. “Mental illness is not binary. We’re not simply either depressed or not depressed. We all walk around with symptoms of mental distress that we find more or less burdensome depending on what’s going on in our lives and our ability to regulate that distress.”

Reuben’s study used data on two air pollutants linked to altered brain health in previous studies: PM2.5 (microscopic pollutant particles generated during industrial processes and combustion of fossil fuels and wood) and nitrogen oxides (pollutants associated with fossil fuel burning from power plants, vehicle emissions, and some industrial sites). Only nitrogen oxide exposure showed clear evidence of worsening mental health, but Reuben said it’s likely that other chemicals in air pollution have similar effects.

“The more we study additional air pollutants, the less confident I am that there’s any class that doesn’t harm the brain,” he said.

While his research doesn’t prove that air pollution causes mental illness, Reuben said, it does indicate that exposure to air pollution may moderately increase the severity of mental illness, and substantially increase the social and financial burden of mental illness on communities.

These findings have major implications for western Pennsylvania.

From 2018-2020, 40% of adults in Allegheny County reported having one or more days where their mental health was “not good,” according to state data. That figure was even higher—53%—among 18-44 year olds. These figures were higher in Allegheny County than in half of other Pennsylvania counties, and slightly higher than state averages.

An estimated 13% of adults in Allegheny County said their mental health was not good for 14 or more days in the last month. That figure was slightly higher in the city of Pittsburgh at 15%, and even higher in Clairton at 18%. This puts Clairton in the worst 25% of U.S. cities for the percentage of adults experiencing 14 or more days of poor mental health each month.

Pennsylvania is among the top 10 U.S. states for mental health spending. Allegheny County officials have said they hope to secure $25 million in federal COVID-19 relief funds to allocate toward mental health, drug, and alcohol services, which would bring the total amount budgeted toward those services for 2021 to $500 million.

Reuben’s study was relatively small, but many other studies conducted around the world have shown links between air pollution exposure and cognitive issues (including dementia and Alzheimer’s disease) and mental illness.

A study published earlier this month uncovered a genetic marker for depression that makes people more susceptible to depression triggered by air pollution, marking the first time scientists have shown a direct link between air pollution exposure and the brain’s functioning at a neurological level.

A massive 2019 study looked at mental health data from 151 million people in the United States and 1.4 million people in Denmark and found that long periods of increased air pollution in urban areas were linked to a 16% increase in cases of bipolar disorder and a 6% increase in depression diagnoses.

View of the Clairton Coke Works in Clairton, PA. (Credit: Njaimeh Njie)

“We saw significant associations between air quality and mental illness, even after controlling for other factors that could cause mental illness” Andrey Rzhetsky, a co-author of the study and professor of medicine at the University of Chicago, told EHN. “I was personally surprised by how strong the signal was.”

The researchers had more detailed data for the Denmark group, Rzhetsky said, and the link between air pollution and mental illness for that group was even stronger: Air pollution exposure was linked to a 31% increase in bipolar disorder, a 104% increase in schizophrenia, a 210% increase in personality disorder, and a 68% increase in major depression.

In addition to being much larger, Rzhetsky’s study differed from Reuben’s in that it looked at official mental illness diagnoses rather than symptoms and considered the effects of 87 different air pollutants. That makes it difficult to compare the two studies, Rzhetsky said, but he thought Reuben’s study was “very well designed.” Both studies have similar limitations, including relying on data modelling to estimate people’s exposure to air pollutants.

Scientists are still trying to figure out exactly what happens in brains exposed to air pollution that affects mental health and cognition, but many think it’s related to the inflammation that air pollution causes. Chronic inflammation in the brain can damage neurons that are involved in the brain and nervous system’s regulatory responses, which in turn can impact mental health.

“Studies in animal models have shown there are three different pathways by which air pollutants can get into the brain and cause inflammation,” Rzhetsky said. “One is through the lungs by entering the blood-brain barrier. Another is through olfactory neurons connecting the nose to the brain, and the third is through the stomach and the digestive system.”

When pollutants enter the brain through these pathways, he explained, “it creates persistent inflammation in the brain which can cause symptoms in animals that mimic things like depression or bipolar disease.”

Short spikes in air pollution send more kids to the ER for mental illness

Children playing at an annual “Trunk or Treat” event on Braddock Avenue and Library Street, in Braddock, PA. (Credit: Njaimeh Njie)

Research suggests that exposure to even brief spikes in air pollution increases emergency room (ER) visits for mental health crises in children.

Cole Brokamp, an assistant professor of pediatrics at Cincinnati Children’s Hospital Medical Center and the University of Cincinnati College of Medicine, was the lead author on the first study to look at short-term exposure to air pollution and mental health effects in children. That 2019 study found that children exposed to high amounts of air pollution were more likely to end up in the ER for a mental health problem a few days later than children with lower exposures.

Brokamp looked at five years of emergency room data for more than 6,800 children under the age of 18 who visited Cincinnati Children’s Hospital Medical Center for psychiatric distress including anxiety, depression, bipolar disorder, suicidality, personality disorders, and schizophrenia.

The researchers estimated the kids’ exposure to PM2.5 from the three days prior to their visit to the emergency room, and determined that every increase in PM2.5 exposure of 10 micrograms per cubic meter was linked to a large jump in emergency room visits—even though all the daily exposures remained below U.S. Environmental Protection Agency (EPA) standards.

Brokamp noted that few other studies have investigated the link between children’s mental health and air pollution exposure, but their findings likely represent the tip of the iceberg.

“Our study only captured children with mental illness severe enough to prompt an emergency room visit,” Brokamp told EHN. “We also have to think about how it may or may not affect people who have milder depression or anxiety. They may never go to the emergency room, but it doesn’t make their mental health problems any less important.”

No one has yet studied whether there’s a link between air pollution and ER visits for mental illness in western Pennsylvania. EHN reached out to the Pennsylvania Department of Health, the Allegheny County Health Department, and the two biggest hospital systems in western Pennsylvania (University of Pittsburgh Medical Center and Allegheny Health Network) to request data on children’s emergency room visits for mental illness, and none were able to provide that data. But substantial spikes in air pollution are a frequent occurrence in the region.

The median level of estimated daily PM2.5 exposure in Brokamp’s study that led to increased mental health ER visits for children was 10.5 micrograms per cubic meter of air. According to an EHN analysis of EPA data, one or more of the air monitors in Allegheny County recorded daily averages of PM2.5 higher than 10.5 μg/m3 for about four months in 2020 (129 days)—and 2020 was one of the best years in recent history for air quality in the region.

“We’re concerned about the results of this study and this analysis of Pittsburgh’s air,” Patrick Campbell, executive director of the Pittsburgh-based clean air advocacy organization Group Against Smog and Pollution (GASP), told EHN. “We hope our public health officials will take it seriously.”

Brokamp’s study is part of a growing body of research indicating that air pollution exposure is harmful to human health at levels well below current legal limits.

The federal 24-hour standard for PM2.5 is 35 micrograms per cubic meter of air. The Allegheny County Health Department, which oversees air quality in the region, hasn’t yet published its annual air quality report for 2020, but in 2019 one of the county’s air monitors (the one closest to Clairton) recorded 24-hour PM2.5 levels that exceeded that standard on nine days. The highest level recorded was 66.4 micrograms of PM2.5 per cubic meter of air—nearly twice as high as the level currently permitted by law in the U.S. The EPA is expected to tighten standards for PM2.5 in 2022.

Chris Togneri, the public health information officer for the Allegheny County Health Department, said the agency has taken meaningful steps toward improving air quality in the region in recent years.

“The Health Department believes that everyone deserves healthy air,” Togneri told EHN, noting that the agency’s Air Quality Program, which includes around 50 employees, “operates one of the densest air monitoring networks in the nation,” consisting of 16 EPA-approved air monitoring sites that are regularly analyzed to determine if monitors should be added or relocated.

He also pointed to recent improvements to the agency’s air quality alert system and air quality dashboard aimed at making information on air quality more accessible to the general public.

“Overall,” he said, “efforts by the Health Department have resulted in some of the largest improvements in air quality in the United States.”

Environmental injustice and mental health

Air pollution doesn’t respect geopolitical boundaries, so air pollution’s impacts on mental health are relevant to everyone in western Pennsylvania. But many of the communities that experience the highest levels and most frequent spikes of air pollution also experience other community stressors like poverty, crime, and racism.

In Brokamp’s study, children from neighborhoods experiencing high levels of poverty were the most likely to experience a mental illness crisis following spikes in air pollution. He said this could be because poverty and crime cause stress, which results in inflammation that can harm brains and immune systems, which could worsen similar impacts from air pollution exposure.

Examples of what some researchers call “toxic zip codes”—regions where a combination of environmental injustice, racism, and poverty create substantial negative health impacts—abound in western Pennsylvania.

For example, the Monongahela Valley (commonly referred to as the “Mon Valley”), a former steel corridor of municipalities from the southern tip of Pittsburgh to the West Virginia border including Braddock, Duquesne, Clairton, McKeesport, Charleroi, Monessen and Uniontown, regularly sees extreme spikes in air pollution leading to some of the dirtiest air in the country.

The municipalities in the Mon Valley have poverty rates ranging from 16%-40%—significantly higher than Allegheny County’s poverty rate of 11% and the state poverty rate of 12%. A number of these communities also have substantially higher percentages of Black residents compared to the state or region as a whole: Allegheny County is 13% Black and Pennsylvania is 12% Black, compared to Duquesne, which is 57% Black; Braddock, which is 67% Black; and Clairton, which is 38% Black.