Beijing's First PM2.5 Pollution Readings Draws Skepticism

On an average day in Beijing, the smog is a thick whitish yellow blanket. Millions of people living there breathe a veritable soup of air pollutants. PM2.5 air pollutants—or those that measure less than two and a half microns—are considered the most dangerous to human health, because they penetrate deep into lung tissue.

After considerable public pressure, Beijing officials began publishing PM2.5 readings, but residents are skeptical of the numbers. One reason is that the readings don't match-up with the numbers released by the US Embassy in Beijing. The Embassy has long published its own PM2.5 data and has become the go-to source for Internet savvy Beijingers wanting to know how dangerous the air is to breathe on a given day.

On Monday morning, Beijing municipal readings were at 30 micrograms per cubic meter—or a "moderate" level of pollution. Four miles away at the US Embassy, the reading was 66 micrograms per cubic meter—considered "unhealthy" by US standards. There could be good reasons for the discrepancies in the numbers, but experts closely watching the situation suspect municipal officials may be manipulating the data. Also, Beijing officials use a less stringent formula for calculating the concentration of PM2.5 pollutant, which could also contribute to lower readings.