Several environmental groups, including the Gulf Restoration Network and the Natural Resources Defense Council, are suing EPA to address discharge limits of fertilizers and other contaminants into the Mississippi River, which they claim create a hypoxic or "dead” zone the size of Massachusetts in the Gulf of Mexico.

The lawsuit involves a petition the environmental groups filed in ’08 that asked EPA to establish numeric nutrient criteria standards in 10 states within the Mississippi River Basin and other areas affecting the Gulf of Mexico. EPA responded to the petition indicating they agreed that harm was occurring but that the agency was addressing the problem by working with the states.

The environmentalists are claiming in the litigation that there is overwhelming evidence of existing harm as a result of nutrients and that EPA has admitted to it within the petition response and therefore EPA is required to act. There is a risk that this litigation could trigger a court mandate for EPA to develop federal numeric nutrient criteria.

The Mississippi River is the largest river system in North America. Its basin stretches from the Rocky Mountains in the west all the way to New York State in the east and drains all or part of 31 states.