Teams have spent the past year rigorously checking implementation of environmental regulations, as Hou Liqiang reports.

In his 10 years as an environmental law enforcement officer, Yin Wei has never known his schedule to be as tight as when he was sent to the Beijing-Tianjin-Hebei cluster as part of a yearlong program to monitor air pollution control.

During the three weeks he spent in Handan, Hebei province, Yin got up at 6 am but didn't get to bed before midnight. He spent his days inspecting companies, either openly or covertly, and looking for any violations of pollution regulations. "We only had half an hour for lunch," he said, referring to the hectic schedule.

The native of Lyuliang, Shanxi province, and his colleagues would arrive back at their hotel at about 7 pm every evening, and then rush to send details of violations or illegal behavior to the Ministry of Environmental Protection by 9 pm. After that, they scoured complaints submitted to local authorities, looking for clues to potential irregularities, and then selected the companies they would inspect the following day.

Every company may be inspected several times and the inspection records will be handed on to successive teams, he said.

Yin, whose four-strong team was among the first to be dispatched, is one of 5,600 officers taking part in the largest-ever air pollution control operation in North China. The assignment started on April 5, although most of the teams only take part in the inspection for two weeks at a time.

Even though the inspection has made progress and air quality in the cluster has been improved, work to control air pollution in the region will be intensified. Meanwhile, as the inspection draws to a close, the authorities have been drafting a new three-year operation dubbed a "blue sky protection campaign". As a follow-up measure, a number of leading experts will work to draft air pollution measures tailored to the situations in each of the 28 major cities in the cluster, according to officials.