A rainbow rises along side fountains against the clear sky in Beijing Olympic Park Friday. [Xinhua]

Emissions of sulfur dioxide (SO2) in the Olympic host city in the first half of this year fell by 12.94 percent compared with the same period last year, the Ministry of Environmental Protection announced.

COD, or chemical oxygen demand, a measure of water pollution, dropped by 3.82 percent, it added.

The Chinese capital had projected to cut pollution levels for the two indicators by 10 percent and 4 percent respectively from last year.

The Beijing environment bureau attributed the achievement to the city's painstaking efforts in industrial restructuring and application of environment protection technologies.

According to the Beijing municipal government, the city has invested more than 140 billion yuan (20.5 billion U.S. dollars) since 1998 to improve its air quality.