Acid rain not only causes buildings, statues and bridges to deteriorate faster than usual, but it also does serious damage to the ecology.

Downpours dissolve the beneficial minerals and nutrients in soil, and in extreme cases can lead to croplands becoming infertile.

Acidified soil also affects the roots of crops planted by farmers and can reduce yields. This poses a serious threat to food security, especially at a time when China's farmlands are already shrinking due to rapid urbanization.

Rivers, lakes and streams polluted by acid rain become more acidic, which can cause them to lose the ability to sustain fish and other aquatic life. Over long periods, entire lakes and steams can become lifeless, except for algae.

This, in turn, will then have a significant effect on the food chain. For example, terrestrial animals depending on aquatic organisms for nourishment and nutrients will die out as food sources decline.

Acid rain cannot hurt a human's health directly, say scientists. For example, swimming in an acidic lake or walking in an acidic puddle is no more harmful than swimming or walking in clean water.

However, sulfur dioxide and nitrogen oxides - the pollutants that cause acid rain - can cause respiratory disease in humans, as well as make existing conditions worse.