Letters to the Editor, February 28, 2013
We would like to point out that the article "Smog in Pearl Delta 'worse than Beijing'" misrepresented how air pollution in the Pearl River Delta should be understood. For those of us who study air quality in the delta, the air pollution there is not worse than that in Beijing.

We would like to point out that the article "Smog in Pearl Delta 'worse than Beijing'" (February 21) misrepresented how air pollution in the Pearl River Delta should be understood.
For those of us who study air quality in the delta, the air pollution there is not worse than that in Beijing.
The article misquoted one of the undersigned, who had merely explained the different causes of PM2.5 in the two places. Coal burning and photochemical smog are the main causes of air pollution in the northern part of the mainland, while photochemical smog is the main cause in the Pearl River Delta.
As a result of joint efforts of the Guangdong and Hong Kong governments to reduce the emissions in the delta, with the support of scientific research institutes in Hong Kong, the Pearl River Delta and Beijing, the particulate level in the delta was reduced by 14 per cent between 2006 and 2011, as registered by the Pearl River Delta's regional air quality monitoring network.
Last November, the Hong Kong and Guangdong governments agreed to set emission reduction targets for 2015 and 2020, in respect of four major air pollutants, including respirable suspended particles.
Both governments will continue to work in partnership to improve the air quality of the Pearl River Delta region.