Ammonia is one of the most important pollutants in the aquatic environment. It is highly toxic and waste fluids, such as municipal wastewater or runoff from concentrated animal feeding operations, must be treated extensively to lower the concentrations of ammonia in surface waters.
Currently, there are separate ammonia criteria for freshwater depending on whether salmonids or mussels are present. Salmonid fish include salmon, trout and whitefish. When conducting research in lakes, streams and rivers using the current criteria, scientists first have to determine if these fish or mussels are present. Scientists also suspect that the current criterion is not protective of freshwater snails.
EPA collaborated with the U.S. Geological Survey to develop a method to breed and raise Idaho pebblesnails (Fluminicola sp.) and test their sensitivity to ammonia. The Idaho pebblesnail is a freshwater snail common in the western U.S. Toxicity data from the lab-controlled studies showed that it is among the most sensitive species evaluated for developing the ammonia criteria.
The data also prompted a significant change in the way the ammonia criterion is stated. The criterion will now apply nationwide to all aquatic species. Permit writers will no longer have to determine if salmonid fish or mussels are present in a given water body. This will make it much easier to be consistently protective of all aquatic life, including threatened or endangered freshwater snails. EPA is revising the 2011 National Aquatic Life Ambient Water Quality Criteria for Freshwater Ammonia to reflect this change.