BEIJING — China started reopening roads and airports in Beijing and surrounding areas that were shut by heavy smog, allowing millions of travelers to return from a week-long holiday.

Air quality index readings for half of Beijing’s 12 urban areas fell below 200, the level dividing medium and heavy pollution, as of 12 p.m. today, according to data on the website of the Beijing Municipal Environmental Monitoring Center.

“Beijing will see light rain tonight, which will make it easier for air pollutants to dissipate,” Beijing Meteorological Bureau said today in its official microblog. The bureau lifted a yellow alert on smog at 8:50 a.m., predicting that visibility will improve.

The closures yesterday of six expressways and disruption at Beijing Capital International Airport underscore the severity of pollution that has become the top cause of social unrest in China. Premier Li Keqiang has pledged a cleanup that includes cutting coal consumption, shutting steel plants and controlling the number of cars.

An estimated 430 million people were expected to travel during the holiday that ends today, according to the China Tourism Academy.

“Air pollution will be an additional factor for holiday traveling that needs to be considered,” said Chen Yifeng, a Shanghai-based accountant who didn’t travel during the holiday to avoid crowds. “I won’t go to heavily polluted places like China’s north region as it’s either hazardous to your health or causes trouble when traveling.”

ROADS CLOSED

Police closed six expressways linking the capital city to Shanghai, Tianjin and Harbin yesterday, and 47 flights at Beijing Capital International Airport were affected.

Some parts of the expressways linking Beijing to Shanghai and Tianjin were still closed as of 9:40 a.m. because of haze, according to Beijing Capital Highway Development Group Co., which operates the highways.

Flights have resumed at Beijing Capital International Airport, an official said, declining to be identified citing company policy. Air China Ltd., the nation’s biggest carrier by market value, will put on additional services after the smog affected at least 47 flights yesterday, an official said.

The State Council, China’s Cabinet, said last month it will cut coal consumption, close steel plants and control the number of cars on its roads to gradually eliminate heavily polluted days in as soon as a decade.

CONTROL POLLUTION

China will build a nationwide network within three to five years to monitor the impact of air pollution on health, the official Xinhua News Agency reported on Oct. 5, citing the Chinese Center for Disease Control and Prevention.

A total of 43 monitoring spots will be set up in 16 provinces and municipalities frequently engulfed by smog to facilitate research on air pollutants in different regions, the impact on the health of vulnerable groups and the study of related diseases, the report said.

Separately, Typhoon Fitow, which killed two people in the eastern city of Wenzhou, led to the cancellation of 22 flights in Hangzhou today and the suspension of at least 59 bullet trains in Zhejiang province, Xinhua reported. The storm made landfall in the southeast Fujian province, according to Xinhua.