Air quality in Beijing in 2017 was the best since pollution controls started five years ago.
According to the Beijing Municipal Environmental Protection Bureau, the average PM2.5 level in 2017 was 58 micrograms per cubic meter, down 20.5 percent from 2016. The World Health Organization recommends an annual PM2.5 level of 10 micrograms pcm.
Beijing also had reduced densities of pollutants such as sulfur dioxide and nitrogen dioxide. Additionally, the number of "heavy pollution" days fell from 58 in 2013 to 23 in 2017. Beijing also had 226 "good air" days last year - 28 more than in 2016.
Bureau official Li Xiang said "demolition of coal-fired boilers, phasing out high-emission vehicles and upgrading industrial structure" all helped cut smog.
And Beijing was helped by an absence of coal in about three million homes newly fitted with gas or electric heaters.