Beijing Air Comparison: Good vs. "Hazardous"

On June 22, 2011, Beijing had a particularly miserable day as far as air pollution goes. It wasn’t as serious as the “crazy bad” day in November 2010, but it was still remarkably polluted. Visibility was low, it stunk, and I could actually taste the pollution in the air.

Air pollution in Beijing, June 2011

According to the sensors used at the U.S. Embassy in Beijing, the pollution level was "Hazardous", meaning it had an air quality index value greater than 300. At its worst it was 473 that day (the scale only goes up to 500), with a PM2.5 concentration of 459 micrograms per cubic meter. For reference, in 2009, the average PM2.5 concentration in the Los Angeles area was "only" 12.68, and the World Health Organization recommends an average annual exposure of no more than 10. Keep in mind that the 10 μ/m³ guideline is only an "acceptable and achievable objective"—not even necessarily a safe level.

Progression of Beijing's air pollution on June 22, 2011

Readings from the sensors at the U.S. Embassy, as posted to Twitter, @beijingair

Then, just a couple days later, Beijing saw some of the best air it's had in a while.

Great air in Beijing, June 2011

For two whole hours the sensors reported air pollution levels within acceptable limits.

In Beijing, barely acceptable = outstanding

To be fair, Beijing is somewhat making progress in cleaning up the air. Earlier this year, we had a record number of consecutive blue-sky days—the best since 1998.

To compare the good and bad days, I made a page to easily switch back and forth between photos of Beijing's pollution.