Continued surveillance

The list has enabled enforcement officers to deepen their inspections and ensure emissions are being reduced, and the checks will continue until the air quality in the cluster improves to a suitable level, according to Liu Bingjiang. "Instead of leaving law enforcement officers scattered across the country, the ministry will place greater emphasis on a small number of key tasks every year, and once we start, we will keep going until our mission is complete," he said.

According to the ministry, the central government's efforts to tackle severe air pollution in the cluster have been successful. The annual average concentration of PM2.5 fell by almost 40 percent after the government launched a five-year nationwide campaign to reduce air pollution in 2013. For example, the average concentration of PM2.5 in the capital fell by 31.5 micrograms per cubic meter from the 89.5 recorded in 2013 to 58 mcg per cu m last year.

However, attempts to further improve the air quality in the cluster are likely to face more challenges. "Research conducted by several leading climate experts has shown that the winds generated during monsoons in East Asia are becoming weaker, and global warming is likely to make the lower and middle levels of the regional atmosphere more stable. Those factors will result in more frequent smog," said Liu Bingjiang.

He Kebin, dean of the School of Environment at Tsinghua University, said 500 researchers have been dispatched to the 28 cities to conduct research and offer guidance for pollution control work. The researchers' primary task is to draft a detailed three-year action plan for the cities, along with a long-term road map to improve air quality in the region, said He, who is also deputy director of a national joint research center on the causes and control of air pollution.

Liu Bingjiang said the ministry is determined to eradicate air pollution in the smog-plagued region.

"When the air quality is good, we should still have a sense of crisis," he said, noting that there is still a lot to do to permanently ensure blue skies.

"However, when it is not, we should be confident that we will be victorious in the blue sky protection campaign."