At the state level, three agencies share the monitoring and control of pollutants:
- The MPCA focuses on pollutants and stressors in lakes and streams (surface waters)
- The Minnesota Dept. of Agriculture focuses on pesticides and groundwater
- The Minnesota Dept. of Health focuses on drinking water, which comes from both surface waters and groundwater
As more research is done, the agencies know more about common pollutants such as phosphorus and nitrogen. Research also detects new issues such as chloride impacting fresh-water fish and bugs. In addition to pollutants, certain conditions can also stress aquatic life, such as too little or too much flow in streams.
In addition to the pollutants listed below, Minnesota water quality rules contain standards (acceptable levels) for more than 50 other substances, characteristics, and pollutants. Many of these are not widespread problems, in part because the rules have led to adequate controls.