Experts at the research institute for Yungang Grottoes has found that excessive dust and sulphur dioxide, residue of industrial pollution in the air, has accelerated the natural weathering of the grottoes.

Shanxi is one of China's major coal production bases. They warn without timely countermeasures the statues might lose their original look within a short period of time. The Yungang Grottoes were formed into a honeycomb pattern in the cliffs more than 1500 years ago and stretch for a kilometer from east to west.

Shanxi has invested 100 million yuan or about 12 million US dollars to improve the infrastructure and environment around the precious cultural relics. The province currently plans to demolish or relocate unsightly buildings from scenic spots and to plant more trees.

Source: http://en.chinabroadcast.cn/537/2006/01/24/61@45516.htm