– China on Monday started reopening roads and airports in Beijing and surrounding areas that were shut by heavy smog, allowing millions of travelers to return from a weeklong 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 noon Monday, 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 on its microblog. The bureau lifted a yellow alert on smog at 8:50 a.m., predicting that visibility will improve.

The closing Sunday 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 ended Monday, 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."

Police closed six expressways Sunday linking the capital city to Shanghai, Tianjin and Harbin, and 47 flights at Beijing Capital International Airport were affected. Flights resumed at Beijing Capital International Airport, an official said. Air China Ltd., the nation's biggest carrier, said it will put on additional services.

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.

China will build a nationwide network in three to five years to monitor the impact of air pollution on health, the official Xinhua News Agency reported Saturday, 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 at least two people in the eastern city of Wenzhou, led to 22 flights being canceled Monday in Hangzhou and the suspension of at least 59 bullet trains in Zhejiang province, Xinhua reported.