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February 26, 2013

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Home » Metro » Environment

Air quality 'can't be compared'

CLAIMS that Shanghai's air may be more harmful than Beijing's have been dismissed by environmental experts who say air quality in the two cities can't be compared.

Recent media reports noted that Shanghai's air contained more organic chemicals and heavy metals than Beijing's, raising concerns that it was more harmful to health as the yearly density of PM2.5 particles, which are small enough to enter deep into the lungs, was almost the same in both.

However, experts say you can't compare the two cities based simply on one or two pollutants.

Zhuang Guoshun, an environmental researcher at Fudan University, told the Shanghai Evening Post yesterday that the composition of haze in the two cities was different and the content of harmful particles in the air was also different. In different seasons, the two cities' air also showed a bigger difference, he said, adding that Beijing so far hadn't started monitoring nitrogen particles, a major harmful content in the air.

The yearly density of PM2.5 in Beijing is between 50 to 70 micrograms per cubic meter, while in Shanghai it is about 40 to 70 micrograms per cubic meter.

China introduced a new air quality evaluation system this year and included monitoring of PM2.5 particles.

According to the Shanghai Environmental Monitoring Center, the average density of PM2.5 in the second half of last year in the city was 48 micrograms per cubic meter, 37 percent higher than the nation's yearly limits.

The daily limit of PM2.5 is 75 micrograms per cubic meter and yearly limit 35.

Qian Hua from Shanghai Academy of Environmental Sciences also said the air in Beijing was different from that in Shanghai.

"The air in Beijing is drier than in Shanghai and its pollutant discharge is also different from Shanghai," Qian said. "The major sources of pollutants in Beijing are vehicle exhausts, coal burning for heating in winter and sandstorms from February to April, while Shanghai's are vehicle exhausts and industrial pollutants.

"The two cities' temperature, humidity and geographic location are quite different, so chemical changes and meteorological conditions also differ."

He said it was meaningless to compare which city had the worse air quality but it was important for all cities to study the sources of different pollutants and how they lead to secondary pollution after chemical changes caused by the weather.

"Using clean energy, controlling vehicle exhaust emissions and improving industrial procedures to reduce pollution discharges are all effective to lessen air pollution," he said.


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