February 06, 2023
Inhaling air pollution over a long period of time has been linked to depression and anxiety in a new study.
The research, published last week in the journal JAMA Psychiatry, found that over a decade of air pollution exposure to even relatively low levels of pollution can increase a person's risk of depression or anxiety.
The relationship between exposure to air pollution and physical health conditions like lung and heart disease and overall mortality has been well-documented by scientists for decades. Pollution's link to mental challenges, however, is still not clearly understood.
Some studies have linked short-term exposure to severe air pollution with an increased risk of doctor's visits or hospitalization for depression or anxiety. A 2019 study also found a link to an increased risk of schizophrenia and bipolar disorder.
Other studies have found that long-term exposure to small particulate matter increases the risk of a new diagnosis of dementia or Alzheimer's disease, especially for women, older people and people with more clinical risk factors for dementia. Research has also concluded that air pollution harms children's cognitive skills.
The most recent findings were based on data from almost 400,000 mostly white adults in the United Kingdom. Information on where they lived, their lifestyle and air pollution data, as well as their medical records, were combined for the analysis.
The study participants were broken into four groups based on their air pollution exposure. Those with the least amount of air pollution were the least likely to be diagnosed with depression or anxiety. However, it wasn't the group with the highest level of pollution exposure that had the strongest association with a mental health diagnosis. It was the group with the second-highest exposure that had the biggest risk increase – about 15%.
The researchers also found that men were more vulnerable to the effects of small particulate matter than women. According to the U.S. Centers for Disease Control and Prevention, particulate matter is made up of tiny pieces of solids or liquids that are in the air. It can include dust, dirt, soot, smoke or drops of liquid.
Some particles are big enough to appear like smoke in the air, but others are too small to be visible. Smaller particles called PM2.5 are more dangerous because they can get into your lungs or bloodstream.
Scientists have not been about to explain exactly how air pollution from cars, industrial centers and wildfires acts on the brain, but one theory is that it causes a spike in stress hormones which increases inflammation. It is this inflammation of the brain that increases the risk of dementia and other mental health conditions.
Yale health economist Xi Chen has been studying the link between air pollution and mental health in countries such as India and China, where air pollution is at higher levels than it is in the U.S. His own work has shown that high levels of pollution can influence a person's short-term happiness and their likelihood of experiencing symptoms of depression.
Chen was not involved in the British study, but he told USA Today that he was surprised that even relatively low levels of pollution were associated with mental health challenges.
"A lower dose of exposure but for a longer time period can still make a difference and may have an adverse affect on mental wellbeing. I think that's the key message," he said.
To decrease your individual exposure, experts say to avoid spending time on heavily congested roads and areas where cars may be idling. They also recommend moving to areas with less pollution, and using high-quality air filters for your home's HVAC units. You should also check the EPA Air Quality Index daily, so that on days when air pollution is likely to reach harmful levels, you can spend more time indoors.
In the American Lung Association’s 2021 State of the Air report, Philadelphia ranked 17th on the list of the 25 U.S. cities most polluted year-round by particle pollution.