The Chinese government has released a four-step schedule to monitor the PM2.5 pollution indicator in the next five years, the minister of environmental protection announced Wednesday.

In a speech at a national environment protection conference, Minister Zhou Shengxian said that indicators for PM2.5, ozone and carbon monoxide will be added to the national standard.

To fulfill the monitoring of PM2.5 and ozone, Zhou gave a four-step plan: from next year, PM2.5 and ozone will be monitored in Beijing, Tianjin and Hebei Province, the Yangtze River Delta, the Pearl River Delta, municipalities and other capitals.

In 2013, 113 key cities and environmental protection model cities will be added. In 2015, all prefecture-level cities will come into the program before a 2016 nationwide rollout.

Zhou said the country will also improve a joint mechanism on air pollutants in key areas and a warning system will be set up to advise the public when heavy pollution shrouds the skies.

PM2.5, particles with a diameter less than 2.5 microns, aroused public attention in late October after different results of air quality monitoring tests were simultaneously released by Beijing's weather forecast station and the US embassy in Beijing.

"At that time, I dared not to go outside, as the haze covered the city, but the official data said the pollution was not so heavy," Chen Zhenyun, a resident in Beijing, told the Global Times yesterday.

It is good news that the government will follow the new standard, commented Pan Xiaochuan, a professor at Peking University, on his microblog yesterday.

"It is reasonable to bring in these new changes in steps, because some regions have better technical and economic conditions to carry out the monitoring," Pan said while answering Web users' questions on the PM2.5 measurement on Weibo.

The World Health Organization (WHO) ranges the PM2.5 measurement from 10 to 35 ug/m3 (microgram per cubic meters), and China will adopt the 35 ug/m3 standard, which is commonly used for developing countries, Pan said.

Technically, it is not difficult to monitor PM2.5 as it is similar to the PM10 monitoring principles, Zhu Jianping, deputy director of environmental monitoring department, told the Beijing Times.

However, Zhu said that the biggest problem is financing. "PM2.5 monitoring equipment costs between 80,000 yuan to 380,000 yuan ($12,620-$59,943).

"A preliminary estimate shows that more than 338 prefecture-level cities have to invest more than 2 billion yuan on the equipment," said Zhu.

"It would be a simple way for the public to judge the concentration of PM2.5 on the basis of visibility," said Pan.

The hazard of PM2.5 is from the toxic chemical substances absorbed by the particles which can cause cancer and metal poisoning.