Hong Kongʼs Environmental Protection Department and the Guangdong Environmental Protection Bureau released a report April 26 finding that average levels of ambient SO2 and N2O fell in Chinaʼs Pearl River Delta region in 2011, while ozone pollution worsened. Clean Air Network, however, found increases in each pollutant as well as coarse particulate matter in Hong Kong, and said that the Special Administrative Regionʼs government could no longer blame mainland China for its local air pollution problems.