"Even Beijing, previously an acid rain-free area, was among the hardest hit this year," said Zhou Heng, deputy director of the CMA's monitoring office.

The CMA says 80 percent of rainy days in Beijing were "acid rain days" in August.

Southern China has also seen more serious contamination since 2003, according to Zhou. Acid rain has hit regions running from the northeast to the southwest.

Experts attribute the rise in acid rain to increased emissions of sulfur dioxide and nitrogen dioxide since 2003.

China is the world's biggest sulfur dioxide polluter, with 25.49 million tons of sulfur dioxide discharged in 2005. The amount is up an alarming 27 percent since 2000.