BEIJING, Dec. 31-- China's improved air quality monitoring standards will apply in more cities from Wednesday, the latest effort to combat air pollution.

The number of cities covered by the tighter standards will rise from 74 to 161. The cities will be required to issue real-time air quality monitoring data, according to a statement from the Ministry of Environmental Protection.

The new standards, which included indices for ozone and PM2.5 (airborne particles measuring less than 2.5 microns) come into use on Jan. 1. Previously, PM10 was the main indicator of air quality.

The new standards come in response to public debate in 2011, when people became aware of the huge discrepancies between the air quality data published by the U.S. Embassy in Beijing and that of local environmental agencies.

Central and local governments will invest about 440 million yuan (72.68 million U.S. dollars) to improve monitoring, and the ministry will use nearly 100 experts to overhaul such monitoring stations nationwide.