Beijing’s municipal government is considering the establishment of six air corridors to ease air pollution, which has returned just days after the weeklong Asia-Pacific Economic Cooperation meetings that gave rise to the term “APEC blue”, according to the Beijing Municipal Institute of City Planning & Design.

Beijing’s first blue alert on pollution since the APEC meetings was issued on Nov 19. Blue is the lowest of a four-level warning system. A new spell of smog is expected to begin on Nov 22, covering major areas of northern China.

As the tight reins on production and vehicle exhaust were relaxed after the APEC meetings, pollutants accumulated again, with heavy pollution on windless days, said Zhang Dawei, director of the Beijing Municipal Environmental Monitoring Center.

Air corridors — wide tracts of land aligned in the direction of prevailing winds that help disperse pollutants and hot air in the city — are seen as a significant factor in easing pollution.

“Air corridors can help disperse and prevent the concentrations of small particulate matter, including PM2.5,” said Liu Chunlan of the Beijing Research Institute of Environmental Protection. PM2.5 is particulate matter with a diameter of less than 2.5 microns that can penetrate the lungs and seriously harm health.

Her research team is engaged in identifying air corridors and conducting studies.

Beijing and neighboring cities experienced good air quality during the APEC period, Nov 3-11, and residents called for blue skies to stay.

Chai Fahe, vice-president of the Chinese Research Academy of Environmental Sciences, said that the root solution to ease should be the reduction of emissions from major sources.

“The good air quality during the APEC period has proved that the reduction of air pollutants worked,” Chai said.