Air pollution affects nearly every organ in our body, but did you know air pollution affects your mood too? Research shows direct correlations between air pollution and a bad mood.

PM2.5 Air Pollution Worsens Mood

Researchers at MIT studied how air pollution affects mood across 144 cities in China. Now, there’s a problem. You could ask people about air pollution and their mental health, but then people would probably just tell you, “Oh yeah, air pollution is bad.” That’s what psychologists call “demand effects.”

They got around this problem by analyzing the words people use from day to day. They looked at Weibo, which is China’s Twitter. They used “sentiment analysis,” which rates the positive and negative emotions in the words people use.

For air pollution, they tracked day-to-day air pollution in 144 cities in China. That hits home for me, because I’ve lived in China for seven years, including during Beijing’s “airpocalypse.”

On days when small particles (called “PM2.5”) were worse, people used more negative emotion words. This suggests that air pollution worsens people’s mood.

Factors Affecting Our Sensitivity to Air Pollution

The study discovered a few factors that increased the effect air pollution had on mood. One factor was the day of the week. Air pollution seemed to have the biggest effect on the weekend. I suspect this could be due to people going out more on the weekend and having more time to think about the air pollution. The higher the negative number below, the higher the sensitivity to air polution.

Air pollution also had a larger effect on mood during holidays.

Air pollution seemed to have a bigger effect on the emotion words that women used than men. One possibility is that women express their moods more than men.

Linked to Changes in Mood on Social Media

A study analyzing 7 million tweets from the U.S. during the July 2015 Canadian wildfires found that higher air pollution was linked to more negative and fewer positive emotion words.

Growing Link Between Air Pollution and Depression

Using social media data is only one method to measure the effect of air pollution on mood, and it has limitations. But it connects with a larger body of research on air pollution mental health. For example, studies have found that air pollution is linked to increase risk for more serious mental health issues such as depression and schizophrenia.

• One study found that every 10 microgram increase in NO2 was associated with doubled risk for depression.
• Another study found that every 18 microgram increase in PM2.5 with 6.7% higher risk of depression.
• A 12-year study found PM2.5 significantly increased psychological stress.

How Does Air Pollution Affect Our Brain and Mood?

Although we don’t know all the specifics about how PM2.5 causes mental illnesses, there is a lot we do know. We know PM2.5 particles get into our bloodstream causing havoc in organs all over our body.

PM2.5 can even enter the brain and increase inflammation. This could explain why air pollution exposure is linked to increased risk for Alzheimer’s disease.