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February 23, 2013

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Shanghai's PM2.5 in 2012 higher than national limits

THE average density of dangerously small PM2.5 particles in Shanghai's air was 48 micrograms per cubic meter in the second half of last year, 37 percent higher than the nation's yearly limits, city environment officials said yesterday.

The nation's daily limit is 75 micrograms per cubic meter and the yearly limit is 35.

PM2.5 readings were recorded from June 27 to December 31 in the city, Fu Qingyan, chief engineer at the Shanghai Environmental Monitoring Center, told a seminar on air pollution prevention and control.

"The average reading of PM2.5 is higher than the nation's standard and the air quality poorer than developed countries," she said. "A total of 156 days in the 188 days met the daily limit, which is set higher than the yearly limit considering different weather conditions."

PM2.5 particles, which are less than 2.5 micrometers in diameter, have gained increasing attention for their impact on visibility and people's health.

Researchers told the seminar that fine particles, ozone and acid rain were the three major challenges to air pollution prevention in Shanghai and the entire nation, which suffered four periods of widespread haze in January.

Research in five major cities in 2011, which included Shanghai and Beijing, found that PM2.5 particles had become a major health risk. Overall mortality increased by 0.5 percent whenever the density of PM2.5 rose by 10 micrograms, researchers found.

The World Health Organization has listed PM2.5 as the fourth greatest risk to people's health in China after high blood pressure, smoking and unhealthy diets. WHO estimated that about 1.2 million deaths in 2010 in China were related to PM2.5 pollution.

"We studied the out-patient, emergency and hospitalized patient numbers in Beijing and its neighboring cities of Shijiazhuang and Tangshan during last month's haze pollution," Kan Haidong, of Fudan University's public health school, told the seminar. "People's visits to hospitals rose along with the severity of haze."

Zhuang Guoshun, also from Fudan University, said the government needed to work out effective measures to control vehicle exhaust emissions, a major cause of haze in China.

The seminar was told that researchers were working on a machine to reduce PM2.5 density indoors.

Chen Jianmin, director of Shanghai Key Laboratory of Atmospheric Particle Pollution Prevention, said: "So far we only make a big model, which can only be installed outdoors as it is 3 meters long and 1.5 meters wide."

He said experiments had shown it could eliminate 90 percent of fine particles and a household version would be available at some point in the future.


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