This page includes data that provide two perspectives on water quality. The first data set, from the University of Wisconsin Population Health Institute, is based on data from the U.S. Environmental Protection Agency (EPA) on drinking water safety. The EPA measures drinking water safety in terms of the percentage of the population served by a community water system with reported violations of health-based EPA regulations. The second data set, from the Wisconsin Department of Natural Resources (DNR), includes the number of miles of rivers and streams and square miles of lakes and ponds impaired by water pollution, and the priority level of water pollution in these impaired waterways. Water pollutants include polychlorinated biphenyls (PCBs), phosphorus, sediment, mercury, ammonia, and polycyclic aromatic hydrocarbons (PAHs).