The city saw only eight days last month that were considered good or perfect by standards of the Shanghai Environmental Monitoring Center (whatever those standards mean).
In the previous four Decembers, this number reached around 20 days a month, according to the city monitoring center.
An expert has also said that smog shrouding southern regions of the country is more hazardous than the haze in the north of China, Shanghai Daily reports.
Zhuang Guozhun, a professor from Fudan University, said smog in Beijing mostly consists of natural dust particles.
In around 30 percent the main component is aluminosilicate — crystals that are poor at absorbing water.
But smog in areas in the Yangtze River Delta region is mainly composed of man-made pollutants — including ammonium salt, sulfate and nitrate — which can easily absorb water and expand rapidly.
Compared with dust particles, man-made pollutants are more dangerous as they contain heavy metal elements and toxic organics, he said.
The director of Shanghai’s environmental protection bureau announced last week that it would take at least 10 years to relieve the city of its heavy air pollution. In the meantime, authorities have said that construction will be halted and vehicle usage will be regulated during especially hazy days to cut down on pollution.
In Shanghai, vehicle and factory emissions are believed to make up at least 50 percent of the city’s air pollution, and dust from construction sites make up another 10.5 percent.
Straw burning is estimated to account for around 10 percent of the haze, 7.3 percent comes from power stations and the remaining 20 percent comes from other provinces.
In the beginning of December, environmental authorities announced that air pollution standards in Shanghai would be adjusted to reduce the number of alerts after the city saw off-the-chart Air Quality Index (AQI) levels.