BEIJING, May 22 (Xinhua) -- Beijing's air quality has been improved as the vote to decide 2022 Winter Olympics host is less than three months away.

Beijing Municipal Environmental Protection Bureau (BMEPB) announced on Thursday that thanks to the capital's continuous air pollution control efforts and favorable weather conditions, Beijing's air quality has been much improved in the last four months, with the average density of PM 2.5 (airborne particles smaller than 2.5 microns in diameter) dropping by 19 percent compared with the same period last year.

The average densities of sulfur dioxide, nitrogen dioxide and PM 10 also dropped by 43.1 percent, 13.7 percent and 12.3 percent respectively.

According to BMEPB, Beijing's neighboring city Zhangjiakou has the best air quality among over 70 cities in China. Beijing is pursuing a joint bid with Zhangjiakou for the 2022 Olympic Winter Games.

Beijing has renewed its fights against pollution, which include closing a series of coal power plants to bring back "APEC Blue" -- a phrase coined by Chinese netizens to describe the city's clear skies during the Asia-Pacific Economic Cooperation (APEC) meetings in November, 2014.

The International Olympic Committee will vote on Beijing's bid race against Almaty, Kazakhstan, on July 31 in Kuala Lumpur.