BEIJING, Aug. 4(Xinhuanet)-- Experts warn that anywhere from 80 percent to 90 percent of 30 world heritage sites around China are being menaced by air pollution, with the biggest threat coming from acid rain, said, a noted researcher with the science and technology department of China National Museum.

According to Zhou Baozhong, only the natural heritage sites of Jiuzhaigou and Huanglong in southwestern Sichuan Province, the three parallel limpid rivers of Nujiang, Jinshan and Lancang and the cultural heritage site of ancient Lijiang city in Yunnan Province, also in southwest China, have good air quality.

Other natural and cultural heritage sites are loomed over in the air of poor quality of varing extent. Air quality at Yungang Grottoes in north China's Shanxi Province and Longmen Grottoes in central China's Henan Province is in serious pollution.

Air quality and environmental situation have a direct impact onthe ancient building structures, tombs, grottoes, sculptures and paintings at the heritage sites, acknowledged Zhou.

Acid rain has caused some 90 percent of the precious fir trees in Emei Mountain in Sichuan province to wither away, Zhou said, adding that damages to wooden structures and stone relics are even worse.

He suggested enacting regulations regarding air quality in management of world heritage.

Lu Shoulin, an ace expert from the world famous Palace Museum in the national capital, said a supervision and early-warning system should be set up to help tackle the knotty problem. Enditem