An updated action plan for phasing out major emitters of airborne pollutants in North China released by the Ministry of Ecology and Environment makes preventing days of heavy pollution the top priority this fall and winter.

The plan, released every year since 2017, covers the Beijing-Tianjin-Hebei province cluster and the Fenwei Plain region, including Shanxi, Shaanxi and Henan provinces, where average densities of PM2.5, particulate matter with a diameter of less than 2.5 microns, are the highest in China.

This year's plan put effectively dealing with heavy pollution days as the top priority. It was further down the list in previous years.

Ministry spokesman Liu Youbin told a news conference last month the change was made in response to public opinion because people complained more about heavy pollution days than other air pollution issues.

"While our general goal will not change, combating heavy air pollution will be the focus of the work for this fall and winter," he said.

Cai Jun, an official from the ministry's department of atmospheric environment, told People's Daily: "People are more likely to concentrate on heavy pollution days compared with other air pollution. With the continuous improvement of air quality, their tolerance for high levels of air pollution is declining, and mitigating the worst situations is necessary.

"Besides, one or two heavy air pollution processes may raise the whole year's average PM2.5 density and stop an area from achieving the year's pollution control target set by the ministry."

The ministry will step up efforts to ensure that all enterprises that emit polluting gases are included in its heavy pollution emergency response list. When an early warning is issued, such plants need to suspend or reduce production.

From October to December, the Beijing-Tianjin-Hebei cluster should keep the average concentration of PM2.5 below 63 micrograms per cubic meter, the plan said, and have no more than five days with serious or worse pollution in each city.

For the Fenwei Plain, the PM2.5 target is 62 mcg per cubic meter, while the number of days with heavy pollution is capped at five.

This year's plan includes more specific details on dealing with air pollution rather than just giving general goals.

"The new plan puts more emphasis on targeted scientific treatment methods than before because the ministry aims to better tackle the current problems instead of adding new goals," Liu said.

For example, it specifies four periods during which supervisors need to monitor and stop the burning of straw in fields: straw harvest season, the first half of the night, before rain and before sowing. Farmers usually burn straw to produce ash that can be used as fertilizer, but the burning causes air pollution.

Large steel enterprises such as Shougang and Taiyuan Iron and Steel will be required to play a leading role in achieving ultralow emissions in the iron and steel industry, the plan said.

The ministry will report any air quality improvement in the areas every month, and government officials in areas that fail to meet quarterly targets will have to answer to it.

Any local government that tampers or forges monitoring data will be investigated.

Last fall and winter, the average concentration of PM2.5 in the Beijing-Tianjin-Hebei cluster decreased by 33 percent compared with the same period in 2016, and the number of heavy pollution days was down by 52 percent.

"Despite the positive results, the processes leading to heavy pollution days will remain a feature of the region, especially during adverse weather conditions," Liu said.