China's cabinet ordered on Wednesday new air-quality standards to measure the most dangerous form of particulate matter, following a public outcry over worsening air pollution.

The State Council told 31 major regional capitals including Beijing and Shanghai to begin monitoring PM2.5 particulate, or fine particles measuring 2.5 microns in diameter, this year, the cabinet said on its website.

The new measure -- which had been demanded by environmental campaigners -- would be compulsory for 113 more cities in 2013, it 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 China, activists say.

But the cabinet did not publish the indices on how the readings of the new standards would be interpreted. It also did not say when this year Beijing and Shanghai would adopt the new measure.

The state-run China Daily reported that if PM2.5 were used as China's main standard, only 20 percent of Chinese cities would be rated as having satisfactory air quality, against the current 80 percent.

Most Chinese cities now base their air-quality information on particles of 10 micrometers or larger, known as PM10, and do not take into account the smaller particulates that experts say are most harmful to human health.

"Our nation's pollution emissions are rather large, the air pollution problem in some regions remains prominent and the state of air pollution serious," the cabinet said when announcing the new standard.

"We need more determination, higher standards and stronger measures to fully strengthen overall air pollution prevention and advance continued improvements in air quality."

The meeting also called for the removal of outdated and polluting industrial technology, as well as pollution control improvements in major industries such as energy, steel, building materials and chemicals.

A doubling of coal consumption over the last decade and booming auto sales that have made China the world's biggest car market have made air quality in China among the worst in the world, according to international organisations such as the United Nations.

Wang Qiuxia, an air pollution expert with Chinese group GreenBeagle, said last month that adopting new air-quality standards would not have an immediate impact on pollution.

"According to some assessments it will take 20 years before we see an improvement in Beijing's air quality, provided that proper measures are adopted," Wang told AFP.