As more research is done, the department learns more about common pollutants, such as nutrients, bacteria and chloride. Research also detects new issues like perfluoroalkyl substances (PFAS). In addition to pollutants, certain conditions, such as high temperatures or excess surface runoff into streams, can also stress aquatic life.
In addition to the pollutants listed below, Missouri water quality rules contain standards for many other substances, characteristics and pollutants. Many of these are not widespread problems, in part because the rules have led to adequate controls.