motorcycle driver with mask
It’s not just the traffic that’s bumming him out.
TonyV3112 / Shutterstock

When planning a recent trip to Beijing, I was delighted to see that the forecast predicted perfect weather: sunny, clear, highs in the 70s with no chance of rain. So imagine my surprise when on my first morning in the city, I looked out the window and saw a dense, immobile ceiling of dark gray clouds.

It wasn’t that Weather.com got it wrong. It was that pollution was unusually high that day — the U.S. Embassy Air Quality Index (AQI) readings were over 400 parts per million of PM2.5, well into the “hazardous” range, and at least eight times what the embassy would deem completely non-dangerous. The embassy advises that under such conditions, “everyone should avoid all physical activity outdoors.” The particulate matter comes from the burning of fossil fuels in factories, coal-fired power plants, and cars — the same culprits that cause climate change.

I had always imagined air pollution as a largely invisible phenomenon: It’s out there and it’s bad for you, but other than when it makes the sunset over New Jersey especially colorful, I had never actually seen it. During my trip to China, I had to get used to the idea that I didn’t need to bring my rain jacket just because it looked as if the sky was filled with ominous rain clouds. The friends I was visiting would schedule their jogging routines around low-pollution days, and keep the windows tightly shut when the AQI spiked. Some people walk around in face masks, as if they are extras in a horror film set in the post-nuclear apocalypse.

Over the last few days, the news media has been filled with stories of northeast China’s epically bad pollution. (Due to wind patterns, the pollution comes and goes and can vary dramatically.) As The Washington Post reported Tuesday:

In the industrial city of Harbin, home to more than 10 million people, vehicles crawled through the smog with fog lights on or emergency lights flashing. Bus service was canceled, a major highway was closed and hospital admissions soared by 30 percent, local media reported.

The smog descended on Harbin on Sunday evening. On Monday, the measurement of fine particulate matter in the air known as PM2.5 reached 1,000 micrograms per cubic meter in parts of the city, 40 times what the World Health Organization considers safe.

Meanwhile, according to the Associated Press, American jazz singer Patti Austen canceled a concert in Beijing “because of an asthma attack likely linked to pollution.”

Some of the stories about China’s pollution problem note the physical effects, which are easily quantified: reduced lung function, eye irritation, and an estimated average of 5.5 years of reduced life expectancy.

But when I was in the country, I wondered about the psychological impact of living under oppressive pollution. It must exact a heavy toll to go days on end without seeing the sun — and these are days that pile on in addition to the normal cycles of clouds, rain, and short winter days. Not being able to breathe fresh air or go for a run has to make you more stressed out.

And, sure enough, the academic literature backs that up. Last summer, the American Psychological Association reported, “evidence is mounting that dirty air is bad for your brain … Over the past decade, researchers have found that high levels of air pollution may damage children’s cognitive abilities, increase adults’ risk of cognitive decline, and possibly even contribute to depression.”

Among the various psychological and neurological effects found by studies described in the APA report:

  • “Older women who had been exposed to high levels of [particulate matter] experienced greater cognitive decline compared with other women their age.”
  • “Kids exposed to greater levels of black carbon [soot] scored worse on tests of memory and verbal and nonverbal.”
  • “Children who had been exposed to higher levels of urban air pollutants known as polycyclic aromatic hydrocarbons while in utero were more likely to experience attention problems and symptoms of anxiety and depression.”
  • “Pollutant-exposed mice showed signs of the rodent equivalent of depression. [They demonstrated] depressive-like symptoms [such as] giv[ing] up swimming more quickly in a forced swim test and stop[ping] sipping sugar water that they normally find attractive. Both behaviors can be reversed with antidepressants.”

One wrinkle in the research is that particulates often come in a package of various pollutants, such as sulfur dioxide and nitrogen oxide, and it is hard to untangle which specific pollutant is to blame. Many researchers try to study the relationship between psychological problems and one specific pollutant, and their findings of correlation vary.

“All pollutants come at us in complex combinations, and sorting out the influence of the combinations is problematic,” says Colleen Moore, chair of the psychology department at Montana State University and author of Silent Scourge: Children, Pollution, and Why Scientists Disagree. “I always thought that the air pollution research should have just used the numerical values of the EPA Air Quality Index and not tried to go into details on the particular pollutants. If you look at it that way, there are effects on mental health that are pretty clear.” (Further complicating matters, Moore has found that noise pollution can also cause psychological distress, and Beijing certainly has plenty of that, thanks to its manic traffic and constant construction.)

Ironically, Americans living in Beijing may find that awareness of pollution causes more psychological distress than the pollution itself. That’s because residents are so anxious about it. “As better data about current air conditions became available, people started checking websites and smartphones when deciding whether to exercise outside or wear a mask during the commute,” says Graham Webster, an academic researcher for Yale University living in Beijing. “Increased consciousness is good for policy reasons, but it can also be a kind of burden in addition to the actual smog, especially if consciousness comes with complaining instead of anything more constructive.”