Source: "The bad earth"
The World Health Organization estimates that smog in China contains ten times more pollution than what would be considered safe. Air pollution is visible but soil pollution, although less visible, is more of a problem. A 2014 soil survey conducted by the Chinese government (and kept secret for years) indicates that almost 20% of all farmland in China is contaminated with heavy metals like cadmium or arsenic, due to unregulated pollution from heavy industry. This is an area the size of all the arable land in Mexico. And this is a problem as soil can remain toxic for decades or even centuries and take years to clean up (it took the US over 20 years to clean up the relatively small Love Canal site in New York State). This is a further problem as China already has 18% of the world's population but only 9% of its arable land.
Human impacts of soil pollution include China's "cancer villages" - these are 450 locations where there are unusually high levels of liver and digestive tract cancers amongst the inhabitants. There is also "cadmium rice" - a recent test conducted in the southern Chinese city of Guangzhou found that half the rice tested had high levels of the toxic metal cadmium.