One-fifth of China’s agricultural land is polluted, particularly in the country’s southern rice baskets, according to a sobering government report previously classified as a “state secret”.

Soil pollution, including hazardous levels of cadmium, nickel, arsenic, lead and mercury, is particularly pronounced in the Yangtze and Pearl River Deltas, and generally in the south where rice is grown, the report said. Previous exposés by Chinese media had found severe cadmium pollution in rice grown in the southern province of Hunan, raising national alarm.

“There’s a clear link between pollution and people’s health, so we pushed through legal channels to get this released. Transparent information is part of building rule of law,” said lawyer Dong Zhengwei, whose freedom of information request to get the government to release the results of a 2005-2010 soil pollution survey led to the report being classified a state secret in 2013.