The admission by China’s Environment ministry came in a five-year plan on tackling pollution.

“In recent years, toxic and hazardous chemical pollution has caused many environmental disasters, cutting off drinking water supplies, and even leading to severe health and social problems such as ‘cancer villages’” the document says.

Environmentalists have long campaigned for the government to recognise and help the hundreds of cancer clusters caused by poisoned soil, water or air. In 2009, Deng Fei, an investigative journalist helped toplot some of the worst-hit villages on a Google map.

“I do think this shows a positive development,” said Ma Jun, one of China’s leading environmentalists. “The recognition of the existence of problems is the very first step and the precondition for us to really start solving these problems.”