China in a battle to save its farmland

The survey, which covered about 6.3m square kilometers of soil, found that roughly two-thirds of China's total area is polluted.

The survey was commissioned by the Ministry of Environmental Protection from 2005 to 2012, though the findings had been previously kept secret by the Chinese government.

The study, which appeared on the ministry’s website, blamed mining and farming practices among other causes.

The ministry said that it had examined soil in a variety of settings, including forests and areas earmarked for development, as well as farmland. Of farmland, the ministry said that more than 19% was polluted.

“The national soil pollution situation is not positive,”​ it said, adding that more than 80% of the soil pollution was caused by “non-organic contaminants.”​

Though the ministry has had the results with it for two years, it had previously described the results as a state secret and refused to release them, a move that received intense pushback from environmental campaigners.

In response to public pressure, the central government has opened up more on pollution matters, including releasing more accurate data on air pollution after many of its cities were covered in smog last year.

The ministry also acknowledged the existence of “cancer villages​” years after the media first reported on more than 100 polluted rural areas with higher incidences of the disease.

Chinese Premier Li Keqiang announced in March this year that the country was declaring war on pollution as he sought to address public concerns on issues ranging from smog to food safety.