According to a report from China's Environment Ministry for the first half of 2013, only 4 cities met the acceptable air quality standards. The national grade 2 standard in China is for 35 micrograms per cubic meter for levels of airborne particulate matter smaller than 2.5 micrograms in diameter. WHO standard is for 25 micrograms per cubic meter in a 24 hour period. The 4 cities with acceptable air qualty out of 74 cities monitored by the Environment Ministry are Lhasa in Tibet, island city Haikou, coastal town Zhoushan, and Pearl River Delta city of Huizhou.