Halting emission-heavy production and banning half of the city's cars relieved the Chinese capital of smog during the Asia-Pacific Economic Cooperation (APEC) meetings, data released by the Beijing environment watchdog confirmed.

In order to lessen pollution for the economic forum, Beijing and its neighboring regions imposed tight limits on car use, ordered factories and construction sites to close and declared a holiday for public-sector employees.

The tough emissions-reduction measures greatly improved air quality and the phrase "APEC blue" was coined on social media to describe the clear sky that came with a heavy price tag.

Following the APEC air pollution control plan, between Nov. 1 and Nov. 12 the city's daily PM 2.5 density fell to 43 micrograms per cubic meter, a 55-percent reduction compared with the same period last year, according to the Beijing Municipal Environmental Protection Bureau.

Daily average levels of sulfur dioxide, nitrogen dioxide and PM 10 decreased by 57 percent, 31 percent and 44 percent respectively from the same period in 2013, it said.

According to the bureau, the control of vehicle and factory emissions, the two biggest sources of smog, were the most effective measures.

"Beijing had 11 days of good air quality, while only one day suffered from mild air pollution," said Fang Li, deputy head of the bureau.

"The city became cleaner and traffic flow was more smooth and quick during APEC," said Song Qiang, head of Beijing Municipal Research Institute of Environmental Protection.

A post circulating widely on China's popular messaging service WeChat said that APEC also stands for "Air Pollution Eventually Controlled." Another post defined "APEC Blue" as "something that is beautiful but transient, almost like an illusion."

While emission-reduction controls were removed following the end of the APEC meetings, environmental experts called for some of the strict measures to continue.

Director of the Beijing Institute of Public Environmental Affairs, Ma Jun, urged authorities to ensure the monitoring of high-emission factories was strict and regular.

Wang Zifa, a researcher with the Institute of Atmospheric Physics of Chinese Academy of Sciences, said Beijing could close factories that generated heavy pollution through legislation.

The Beijing Municipal Government is mulling the inclusion of air quality into its evaluations of its sub-governments and departments. New factories, or heavy polluting industries, may be prohibited from areas that are plagued by poor air quality and officials deemed accountable for can be punished.

"But solving the air pollution issue is a complicated and long-term task. Everybody needs to shoulder the responsibility to cut emissions and make APEC blue the new normal," Song said.