This story was updated to clarify how the EPA would proceed. The Environmental Protection Agency will propose regulations on nutrient pollution by mid-December 2017 to settle a lawsuit filed by an environmental group in U.S. District Court. The Missouri Coalition for the Environment filed a lawsuit against the EPA in February for not adequately addressing the issue of nutrient pollution through the Clean Water Act. The EPA has agreed to propose rules by next year, unless the agency approves criteria submitted by the state before the deadline. Nitrogen, phosphorus and other nutrients enter waterways through fertilizer runoff and sewage treatment plant discharges. An overabundance of such nutrients have caused fish kills, harmful algal blooms and dead zones along the Mississippi River.