Only half the population has access to safe drinking water, and only 10% has access to household sewage treatment. 43% of the waterways are unfit for human contact, and 90% of the cities have poisoned their own water tables. The following article has pages of statistics like this.

http://factsanddetails.com/china/cat10/sub66/item391.html

The air pollution is at least as bad.

China is a large enough percentage of the earth’s surface area to make these global problems.