(Beijing) -- Barely any rainfall on a bone dry landscape has always made crop farming in the western province of Gansu a rough gamble between the sky and local irrigation policies. But now, farmers reap only sorrow from fields that experts say is severely contaminated with cadmium and other heavy metals.

A survey conducted between 2006 to 2010 by the Ministry of Environmental Protection (MEP) and the Ministry of Land and Resources is believed by many soil pollution experts to be the most comprehensive inspection of China's land pollution to date. But the central government has refused to release the results of the survey, on grounds that the information is an issue of national security. In 2006, the MEP stated roughly 10 million hectares of farmland had been contaminated by heavy metals, including 2.2 million hectares of land affected through water pollution.