The Shanghai Environmental Protection Bureau rolled out a new index for measuring air quality Friday that recognizes three types of air pollution left out of the previous monitoring system.

The launch of the Air Quality Index (AQI) will result in more days when the air is reported to be polluted and could lead to an improvement in local air quality by helping environmental authorities better trace the sources of pollution.

Shanghai, along with 24 cities in Jiangsu and Zhejiang provinces, began publishing the AQI as part of pilot program to comply with a new national standard on air pollution reporting, the Shanghai Environmental Protection Bureau said in a press release Thursday. The Ministry of Environmental Protection has ordered local governments to comply with the new standard before 2016.

The AQI gauges three types of air pollutants that weren't included in its predecessor, the Air Pollution Index (API). They are carbon monoxide, ozone and PM 2.5, which stands for particulate matter smaller than 2.5 microns in diameter. The other three are nitrogen dioxide, sulfur dioxide and PM 10.

Local chemical plants and automobile exhaust are two of the main sources of pollution in the Yangtze River Delta, said Zhuang Guoshun, director of the Center for Atmospheric Chemistry Study at Fudan University.

Other sources include sandstorms out of northwestern China and crop waste incineration in northern China, according to the press release.

Each source causes different kinds of pollution, including PM 2.5, PM 10 and photochemical smog.

"As a first step to improving air quality in the Yangtze River Delta, this joint effort can help authorities identify the sources of pollution," Zhuang told the Global Times.

Because the new index tracks pollutants that have already been gauged at high levels in the city, Shanghai residents will likely see the number of days when the air is considered polluted rise to more than 100 each year, up from the current 30 or so, according to an engineer surnamed Wang from the Shanghai Environmental Monitoring Center.

"The high reading of two of the new pollutants, PM 2.5 and ozone, will certainly push the index higher, so more days of bad air quality will be reported," Wang told the Global Times. 

The Shanghai Environmental Monitoring Center publishes the AQI on its website on an hourly basis.

The center reports the severity of each pollutant on a six-level scale, with each level displayed in a different color. Green means excellent and maroon indicates heavy pollution.