On May 2nd, China Daily reported that "Beijing has 'cleanest month' in 9 years," writing, "the city experienced its best month of air quality since 2000 with 23 blue-sky days in April."
The excellent blog Daily Dose of Air Pollution highlighted that this claim is dubious, noting at least three other months (August and September, 2008, and August 2006) in which Beijing had higher numbers of Blue Sky Days and lower average APIs than April 2009.
I think I've identified the source of confusion. The official Beijing EPB announcement (Chinese), titled 4月本市空气质量创2000年以来同期最好水平, states specifically that April 2009 was the best April since 2000, not the best month overall. It seems the China Daily (or the Beijing EPB spokesperson during the press conference) misrepresented the real announcement.
Two follow up points:
1) While acknowledging progress, we should also simultaneously not get too excited over the "clean" air. The Beijing EPB claims that the average PM concentration during this month was 120 ug/m3 (主要污染物可吸入颗粒物月均浓度为每立方米0.12 毫克), which is still well above China's national air quality target (100 ug/m3) and six times higher than the WHO recommended guideline (20 ug/m3). (Comparison of international standards in this post.) Although it is critically important in China to note progress, we must not wrap ourselves so much in cheers of success that we become blinded to the significant challenges and work still ahead.
2) The China Daily article describes in more detail than I have ever seen how the economic slowdown may have contributed to improved air quality, writing:
Besides strict environmental protection measures, experts think the global economic slowdown might be playing a positive role in environmental protection.
Zhu Tong, an environment professor with Peking University, told China Daily on Friday that heavy industry has decreased production in many polluting factories, which benefits the air.
"Most companies in heavy industry are seeing fewer orders. The output of the Shougang Group this year so far equals the same period during the Olympics," said Wang Dawei, head of the air quality control division of the Beijing municipal environmental protection bureau.
In the first season this year, the added value for ferrous metal and chemistry manufacturing in the capital was 3.36 billion yuan ($490 million) and 1.85 billion yuan, a year-on-year decrease of 18.1 percent and 17.9 percent respectively.
If the improved air quality is indeed due to the slowdown, then this means there is even less cause for celebration.