Air Quality This Week Gives U.S. a Glimpse of the World’s Air Pollution

In East Asia, years of chronic air pollution is one reason that wearing face masks was common well before the coronavirus pandemic. School children there are used to playing inside on bad air days. In the Korean language, bad air has a specific term — fine dust — and its levels are displayed in real time in places like train stations, bus stops and elevators.

“I know fine dust is a problem, and I don’t think twice about it anymore,” said Lee Hyung-ko, a university student from Seoul, the South Korean capital. “It’s not going away soon, so we just have to live with it.”

Air pollution can also weigh heavily on politics. In South Korea, would-be presidents have made reducing air pollution part of their campaign platforms. In China, smog over Beijing and other cities has been seen over the years as a failure of leadership. And smoke that occasionally wafts from forest and peatland fires in Indonesia to other parts of Southeast Asia tends to infuriate neighboring governments.

Sometimes political pressure over bad air leads to tangible changes. Starting in the late 1980s, as Mexico City came under international criticism for its bad air, the city and nearby state government undertook a series of measures, such as limiting how many days cars could circulate each week and shutting an urban refinery. The reforms mostly worked: The city’s air improved dramatically.

In other cases, urban air has improved because of something that no one saw coming. In Bangkok, as in New Delhi and other cities, for example, the air in the city of 11 million people improved noticeably during the coronavirus pandemic, said Mr. Paiboon, the taxi driver, who has been driving a cab for 18 years.

Now it’s back to normal.

“If you drive early morning up on the tollway, you can see it’s all hazy,” he said. “It looks like fog, but it’s not. It’s all dust particles.”