Hundreds of flights were delayed or canceled Friday in Shanghai as record levels of air pollution shrouded China's commercial hub in smog, prompting authorities to urge residents to stay indoors.
On Friday afternoon, the Shanghai government issued its most severe health warning as the city's pollution index ranged between 23 times and 31 times the levels recommended by international health officials.
In the first such advice since a new health warning system was launched in April, authorities urged residents to stay indoors and asked factories to either cut or halt production.
Most of the flights leaving Shanghai's Pudong International Airport, one of the world’s busiest cargo airports, were delayed due to decreased visibility, according to the airport's website.
Hazardous air pollution forced schools to shut or suspend outdoor activities in at least two other cities in eastern China on Thursday. Some schools in Shanghai canceled outdoor activities on Friday, as well.
Shanghai's unusually noxious haze was caused by several factors, including industrial pollution and auto emissions trapped by cold, windless weather, Xu Bin, an associate professor at Shanghai's Tongji University, told Reuters.
On Friday morning, the level of tiny particles in the air that are the most hazardous to health, or PM2.5 particulate matter, reached a "severely polluted" 466, according to the Shanghai government's monitoring website.
A similar measure by the U.S. consulate in Shanghai showed a reading of 503 — a level described as being beyond the index on its website.
Levels above 300 are considered hazardous, while the World Health Organization recommends a daily level of no more than 20.
"I don't think it's fit for people to live in this kind of environment," said Shanghai resident Fan Jianjun, 34, who wore a face mask as he walked through the opaque air in the Lujiazui financial district.
"But I have no choice. I still need to work. I can only take preventive measures but I have no idea whether they work."
Air quality in cities is of increasing concern to China's leaders, anxious to douse potential unrest as more affluent citizens turn against a growth-at-all-costs economic model that has polluted much of the country's air, water and soil.
The incident is especially embarrassing at a time when China seeks to build Shanghai into a global business hub on par with the likes of London, New York and Hong Kong by 2020.
The government has announced many plans to fight pollution over the years but has made little apparent progress.