Chinese authorities have set tougher rules to combat air pollution by ordering all major cities to monitor tiny particles that do serious damage to health. One of China's leading environmental activists, Ma Jun, greeted the change as a major step forward.

Surprisingly, given China's strict control of the internet, state media have acknowledged the change is partly in response to online environmental campaigners.

The national air quality rules were agreed at an executive meeting of the state council presided over by the premier, Wen Jiabao, on 1 March, a statement on its website said.

They order stricter air pollution monitoring standards this year in the mega-cities of Beijing, Shanghai, Chongqing and Tianjin, 27 provincial capitals, and three key industrial belts: the Yangtze and Pearl river deltas, and Beijing's hinterland. Another 113 cities must adopt new standards next year, and all but the smallest cities by 2015.

To "help allay public concern over official air quality readings", levels of ozone and PM2.5 particles must be included. PM2.5 particulate matter is below 2.5 micrometres in diameter, or 1/30th the width of an average human hair, and easily penetrates lung tissue.

"This is a major step forward in terms of China's process to combat urban air pollution," said Ma Jun, director of the Institute of Public and Environmental Affairs. "The prerequisite for mobilising our people is to let them know what is going on.

"It doesn't mean that the sky will turn blue automatically because at the end of the day we still need to cut off these emissions."

Following the announcement, more than a million – mostly positive – comments were posted on the Weibo micro-blogging service in under 24 hours. "Good news, applause," wrote Xu Xiaonian, a prominent economist. Others questioned whether the rules would be enforced.

In January, Beijing's environmental agency included PM2.5 particles in its calculations after months of postings from netizens mocking the discrepancy between officially clear days and the dense smog at their windows. Ma said social media had played an essential role in changing government policy last year.

State media also acknowledged the role of bloggers: "A stirring campaign on the country's social network websites since last autumn seemed to have gained a satisfying response from the country's policymakers," Xinhua news agency said.