PM2.5 emerging as major pollutant in city

The PM2.5 particles are becoming a major pollutant in the city, surpassing former culprits like sulfur and nitrogen dioxides, Shanghai officials said yesterday.

PM2.5 refers to airborne particles which are smaller than 2.5 micrometers in diameter. They are the main cause of urban smog and are harmful to human health.

Between January and May, the city recorded 42 heavily polluted days with the PM2.5 density reaching the highest 200 micrograms per cubic meter on May 11. The city's Air Pollution Index rates it as "serious pollution."

"The former major pollutants - sulfur and nitrogen dioxides - have been decreasing since 2008, but the PM2.5 density has been rising," said Bai Guoqiang, deputy chief engineer with the Shanghai Environmental Protection Bureau.

The average density of PM2.5 is 56 microgram per cubic meter, some 60 percent over the national standard.

During the most severely polluted days in January, the PM2.5 density reached 85 microgram per cubic meter and surged to its highest at 201.

"Some 80 percent of the PM2.5 pollution comes from the city, especially from traffic and heavy industries," Bai said.

Flying dust, power plants and agricultural produce are other major pollutants.

The burning of straws, sandstorms and firecrackers add to the city's pollution as well, Bai said.

The factories in Shanghai's neighboring cities are also a major contributor to the poor air quality in the city, Zhang Quan, director of the bureau, said.

"One of the major culprits of the country's air pollution is the densely distributed chemical factories in east and central Chinese cities," Zhang said.

He said the city must work with the neighboring provinces to curb emissions as it is difficult for Shanghai alone to improve the quality of air .

He proposed establishing a regional commission to supervise factories and a system to alert neighboring cities whenever heavy pollutants are detected in the air. Shanghai will start issuing PM2.5 forecasts later this year, initially offering 24-hour forecasts before progressing to 48-hour outlook.