A southwest China city that used to be plagued by acid rain is gradually shaking off pollution, thanks to a sustained environment campaign that has begun to pay off.

Guiyang, capital of the southwestern Guizhou Province, reported only 19 "slightly polluted" days last year, sharply down from 30 days in 2005, the city government said in a press release Monday.

It said the city's total emissions of acid rain-causing sulphur dioxide were down from 314,100 tonnes in 2005 to 179,500 tonnes last year.

Meanwhile, discharges of "chemical oxygen demand" (COD) -- a measure of water pollution -- in wastewater were 50,700 tonnes compared with 57,700 tonnes in 2005, it said.

Guiyang was once one of the worst cities for acid rain in China, a result of excessive coal consumption by local industries as well as households.

In the past five years, the city has revamped its workshops, replaced coal with clean energy to cut emissions, and increased forest coverage by at least 40 percent to improve the environment, the document said.