Shanghai begins posting PM2.5 readings from 10 stations

Shanghai started to post readings of PM2.5 to the public from 10 monitoring stations around the city on Wednesday.

PM2.5 stands for particulate matter with a diameter of 2.5 micrometers or less. These air pollutant particles can invade even the smallest airways.

In the past, readings from only two control spots — Shanghai's Putuo and Zhangjiang — were available.

Figures such as the average density of PM2.5, the latest 24-hour reading at each station and a chart illustrating data change will be published on the website of the Shanghai Environmental Monitoring Center and the micro blog of the Shanghai Environmental Protection Bureau.

However, authorities at the bureau said they need another six months before they can release hourly and daily readings of all six types of pollution, as required by the country's new Ambient Air Quality Standards.

The six readings are PM10, PM2.5, sulfur dioxide, carbon dioxide, ozone and carbon monoxide.

"The equipment is in the various stations but we're at the debugging stage," said Zhang Quan, director of the bureau.

The Shanghai-based Oriental Morning Post quoted an anonymous professional from the bureau, who said that in order to guarantee the accuracy of detected data, monitoring instruments in the city's 10 spots need to go through the challenge of Shanghai's humid and hot weather.

"Monitoring instruments need a break of three or four hours for maintenance in such wet and humid weather, but, according to the national regulation, valid data needs to be collected for 20 consecutive hours," said the expert. That is why the extra six months is needed, he added.

In the meantime, the monitoring stations are scattered in different districts, from downtown areas to suburbs, to give authentic readings of Shanghai's air quality.

Zhang said: "A city needs at least eight to 10 monitoring stations in various spots, depending on its size, to measure PM2.5. An analysis of a city's air quality cannot be done using readings from a single machine.”

The city of Shanghai has established 30 PM2.5 monitoring stations but only 10 are national control spots.