I really wanted to go running outside this morning.

I’ve got a Chinese lesson in two hours, and my brain seems to function better after a long, hard run. I’m also making progress in losing weight, down more than 15 pounds from a year ago.

But when I peeled back the curtain to check the weather, my hopes for a quick workout were dashed. After a couple of blue-sky days last week, the pollution is back. Buildings a couple of blocks away from my apartment are barely visible from my ninth-floor window. The air is a grayish white.

The latest message from the US embassy, which monitors air pollution and releases readings hourly through its Twitter feed, said the air today is hazardous. The embassy rates air quality based on the amount of PM2.5 in the air – fine particles that are 2.5 micrometers in diameter and smaller. Common sources are power plants, industries and automobiles, according to the U.S. Environmental Protection Agency.

I’m used to this by now: this process of getting up, looking out the window and checking the US embassy’s Twitter feed – all so I can make an informed decision about whether I can run outside without damaging my health.

Oh, and about my health. Since I moved to Beijing in 2010, my blood pressure has gone from normal to unhealthy. I’m usually congested when I wake up in the morning. About once a month, I get one- or two-day sore throats that aren’t accompanied by a cough or other symptoms of a cold. I also feel depressed more often, especially during long stretches of heavily polluted days.

In January, Beijing experienced its worst stretch of heavy air pollution in years, and the city issued alerts warning residents to stay indoors. The pollution index on the US embassy’s Twitter feed, which ranks the concentration of PM2.5 on a scale of 0 to 500, said the PM2.5 density had reached 886 micrograms per cubic meter.

Louisa Lim, the Beijing correspondent for NPR, tweeted: “If I’m reading this correctly, air quality in Beijing now is 20 times higher than that considered hazardous in the US.”

I can’t be certain that my health problems are a direct a result of the dirty air, but a doctor I saw during a checkup last year said it’s possible. According to the World Health Organization, air pollution is responsible for hundreds of thousands of premature deaths in China every year.

Since I’m an expat with an American passport, I can buy a plane ticket and leave whenever I want. I’m here because of a job, but if I decide I need to live in a city with clean air, I have that option.

Most Chinese don’t. Just 1 percent of China’s 560 million city residents breathe air that is considered safe by European Union standards, according to a World Bank study.

And while the government has lifted tens of millions out of poverty over the last few decades, how many millions more are now being threatened by dangerous air pollution – a threat caused by the very forces that have propelled China’s rise?

Each year, for Spring Festival, my company gives out gift bags to its foreign employees. The holiday gift bags usually include traditional Chinese snacks, a calender and office mugs.

This year I got a bottle of wine and an air pollution mask.