China has ordered new air-quality standards to measure the most dangerous form of particulate matter, following an outcry over worsening air pollution.
The State Council told 31 regional capitals, including Beijing and Shanghai, to begin monitoring PM2.5 particulates, or fine particles measuring 2.5 microns in diameter, this year.
The new measure - which had been demanded by environmental campaigners - will be compulsory for 113 more cities in 2013, the State Council said.
Authorities came under huge pressure to change the system last year after local governments routinely reported "slight pollution" when thick smog blanketed whole regions.
The new system could give a more accurate reflection of the true nature of pollution in the mainland, activists say.
But the Cabinet did not publish the indexes on how the readings of the new standards would be interpreted.
It also did not say when Beijing and Shanghai would adopt the new measure.
China Daily reported that if PM2.5 is used as China's main standard, only 20 percent of cities will be rated as having satisfactory air quality, against the current 80 percent, as most of them use the PM10 standard.