Air quality on trains assured by authorities

Shanghai railway authorities Wednesday assured passengers that the air quality on trains comply with national standards, after a passenger said that testing revealed the level of PM2.5 particles on board nearly doubled the limit.

The bureau made the comment in a written statement, but failed to comment further on the issue Wednesday. The release was issued after passenger Zhang Yan and her colleague, who both work for a Suzhou-based air filtration technology company, said Sunday they discovered a PM2.5 reading of 130 micrograms per cubic meter aboard their Beijing-Shanghai high-speed train.

The Chinese mainland regulates air quality by permitting a daily average density of 75 micrograms per cubic meter standard.

Zhang said that she and her colleague used a hand-held air particle counter imported from the US by her company to test the air quality in the carriage carrying less than 20 passengers on the weekend. She posted the results to her Sina microblog, which was circulated some thousand times over in the days following.

"The density of 130 micrograms per cubic meter provides an air quality that is similar to a person smoking two cigarettes in a 10-square-meter room," she told the Global Times Wednesday. "It's hard to imagine how bad the air quality would have been if our carriage was full of passengers."

Zhang, however, said that the reading she took may not be authoritative, adding that monitoring methods vary and the counter she used is less sophisticated than the exponentially costlier ones used by official inspectors.