This paper studies the consequences of China's recent water pollution regulation. We find evidence that the regulation reduces pollution-intensive activity in highly regulated areas. Relative to the locations where regulations are more stringent (downstream cities), locations where regulations are less stringent (upstream cities) attract more water-polluting activity. As polluting activity concentrates upstream, a larger proportion of the river and more poor residents are exposed to high levels of pollution. (C) 2018 Elsevier Inc. All rights reserved.