Zhang Lishan stands on a ridge of dirt tending a small vegetable garden surrounded by pools of stagnant, stinking water. His plot near the banks of the Yangtze River in China's eastern Anhui province is irrigated by the run-off from a large paper mill.

"I can hardly grow anything because this water is poisoned," he says. "It kills all the fish and many of my neighbours have been made sick." At the point where the run-off meets the river, a dead pig bobs on the wake of a cargo ship steaming past.