BEIJING, Oct. 19 (Xinhua) -- Heavy smog continued across north China on Wednesday, causing the cancellation of flights and road closures.
The average density of the fine particulate matter PM2.5 in Beijing's six downtown districts was 279 micrograms per cubic meter at 2 p.m. Wednesday, according to data with the Beijing Environmental Protection Monitoring Center.
Many pedestrians in the capital chose to wear masks while outside. Visibility was less than one kilometer in some areas.
Poor visibility also caused Beijing's smaller Nanyuan Airport to cancel some flights Wednesday.
Beijing authorities advised citizens to reduce outdoor activities and better manage construction projects, which are known for stirring up dust.
Hebei, Shandong and Liaoning provinces, as well as Tianjin Municipality, all issued a yellow alert for smog.
Most expressways in Hebei were shut due to dense fog on Wednesday, according to traffic police.
The PM2.5 reading was 178 micrograms per cubic meter at noon Wednesday in Shenyang, capital of Liaoning, which also issued a yellow alert.
The bout of haze is predicted to be dispersed by cold air on Thursday.
Beijing aims to keep average PM2.5 levels below 60 micrograms per cubic meters in 2017. Its density of PM2.5 decreased by 12.5 percent year on year to 63 micrograms per cubic meter from January to August.