Was January Beijing’s worst-ever month for pollution?

The question is no doubt on the minds of residents as February brings merely “unhealthy” levels of dangerous airborne particulate matter in place of a slew of January days officially classified as “hazardous”—or worse.

The search for an answer provides a glimpse into the difficulty of quantifying China’s pollution problems.

By some measures, January 2013 can claim a title to be at least a recent high. The U.S. embassy in Beijing has since February 2008 tracked dangerous small particles called PM2.5. However, the embassy doesn’t disclose historical readings.

Michael Isvy, a web developer who has tracked the data since 2011 for the foggybeijing.com website, says PM2.5 readings averaged 199 for January, easily the highest in his data set. The next highest is February 2011, with a PM2.5 reading of 158.

continue reading Beijing’s Murky Air-Pollution Measures – China Real Time Report – WSJ.