In December, Beijing issued its very first “red alert” over the levels of smog enveloping the city. The pollution reached such a point that officials took the decision to close many factories, keep children indoors, and limit the number of cars on the road. But to many it came as a surprise, as the level of pollution had been much higher in the past, leading some to assume that it was a sign of the government taking more concern over the health of its people and the environment.

Yet now the Chinese state news agency Xinhua has reported that the city is to raise the threshold for issuing red alerts, which are the highest air pollution warnings. Many countries use the air quality index (AQI) as a measure of how much pollution is in the air. This looks at the concentration of solid and liquid particles larger than 2.5 micrometers, known as particulates, in the air, as well as other harmful substances such as ozone, carbon monoxide and sulfur dioxide. How countries measure the AQI varies from nation to nation.

The calculation of the AQI by Chinese authorities combines the measurements taken from all of these pollutants to give a reading from zero to more than 500. Back in December, a reading of over 200 for three days straight that prompted the red alert. But now it will have to hit 200 for four days, be at over 300 for two days, or breach an AQI of 500 for one day before the city will issue an alert.

To some, this is an attempt by the government to limit the economic impact of issuing red alerts by reducing them, as they result in people being unable to go to work and limits on the number of cars on the road being put into place. “There will be multiple times of red alerts in a year if we continue using the current standards, which will bring about a high social and economic cost,” Ma Jun, an environmental researcher in Beijing, told The New York Times.

During the last red alert, the city recorded the peak number of particulates in the air as 291 micrograms per cubic meter. The World Health Organization recommends that the level of these particulates should be limited to a 24-hour average of just 25 micrograms per cubic meter. So the fact that the Beijing has just made it harder for a red alert to be raised could be seen as worrying.

The new guidelines will not, however, only be in place for Beijing. They will also cover the surrounding industrial areas, including the major port city of Tianjin, which has a massive and rapidly expanding manufacturing industry. It is hoped, Xinhua claims, that these new rules might actually work to reduce the air pollution pumped out by the surrounding regions, which could have a positive knock-on effect for the city itself. 

^{Main image credit: LWYang/Flickr CC BY 2.0}