OREANDA-NEWS. December 26, 2013. Zhejiang Province, an economic powerhouse in the Yangtze River Delta, now has over 20 times the number of hazy days as it did 50 years ago, a research report has revealed.

The average number of hazy days in Zhejiang from the 1960s to the early 1990s was around seven. The figure rose to almost 200 after the millennium, said a report on the province's hazy weather.

Vehicle exhaust and industrial fume are blamed as the biggest causes, said the report by the Environmental Science Research and Design Institute of Zhejiang Province, which is in east China.

A project team collected and analyzed data from the provincial and local environmental and meteorological departments covering the past half a century.

Heavy smog shrouded north and east China on Saturday, with highways closed and flights delayed or canceled.

Cities in Zhejiang and its neighboring Shanghai municipality have been enveloped in grey sky for several days. Many pedestrians have been wearing masks.

The coastal province is known for its prosperous local economy. Private enterprises took off in the 1980s when China started with its market economic reforms.

But along with industrialization has come more smog.

Zhejiang's capital city Hangzhou and other industrial cities, such as Wenzhou and Huzhou, had on average over 40 hazy days annually before 2000.

"The number of hazy days showed an explosive growth after 2000," said Jin Jun, the team leader of the project and the deputy director with the institute.

"Some major cities in Zhejiang have seen an annual average number of 150 hazy days. In some cases about 200 hazy days -- about 30 times the number before reform and opening at the end of the 1970s," said Jin.

Vehicle exhaust is the primary cause of the increasing smog in downtown areas, the report said.

Though the report is based on Zhejiang, it is representative of the country. The main components of the haze are vehicle emissions and industrial sewage which are formed by dust, sulfuric acid and vitriolic acid, said Jin.

Diesel vehicles are the "prime culprit" that cause emissions of PM 2.5, a key indicator of air pollution. Oxynitride which is released from gasoline vehicles easily become particle pollutants, which also worsens air quality, said the report.

"Zhejiang used about seven million tonnes of gasoline and nine million tonnes of diesel last year, which makes the province the second largest consumer of these two fuels nationwide," said Wu Jian, a senior engineer with the institute.

At the end of June, Zhejiang had 13.38 million registered vehicles, and about 8.39 million were gasoline cars.

In the past 13 years, the number of gasoline cars in the province has increased 12-fold.

Planning and construction of the urban transportation network has failed to meet the surging number of cars. Cars in traffic jams release four to five times more emissions than running cars do, said Jin.

But it is not just vehicles.

Industrial pollution is also blamed for the smog, Jin added.

Both industrialization and car ownership have led to Zhejiang's serious air pollution issue in the past two to three decades, he said.

"It is critical we are aware of this serious environmental issue," said Jin.

Both central and local governments are trying to cut pollution by accelerating "green transport" and implementing controls on industry.

Zhejiang also suffers from air pollution around the province as industrial sewage and pollutants caused by winter heating in northern China have flowed into Zhejiang.

The province's island cities of Zhoushan and Shengsi suffer from hazy weather even though they have small populations, few vehicles and little industrial pollution.

"According to our analysis, it is likely that their hazy weather is caused by a dust haze belt from northern China," said Jin.

"The continuous hazy weather in north China's Hebei Province and nearby regions are characteristics of cross-regional pollution," said Guo Bin, deputy director with the Environmental Science and Engineering College of Hebei University of Science and Technology.

Pollutants float in the air and overlap with those in other regions, which spreads pollution to vast areas of China, he said.

The State Council has vowed to restrict high energy-consuming and polluting industries, adjust energy structure and enhance control of PM 2.5 in regions suffering from serious air pollution.

It set a goal of reducing key industries' emissions of major air pollutants by at least 30 percent by the end of 2017.