EPA has published final national recommended water quality criteria for the protection of aquatic life from the toxic effects of ammonia in freshwater. The 2013 ammonia criteria reflect new data on sensitive freshwater mussels and snails, incorporate scientific views EPA received on its draft 2009 criteria, and supersede EPA's previously recommended 1999 ammonia criteria. In addition to the criteria document, EPA has also published supporting information to assist states, territories, and authorized tribes considering adoption of the new recommended criteria into their water quality standards. Ammonia is a type of nitrogen pollution and can enter water bodies via municipal wastewater discharges, animal waste runoff, air deposition, and runoff from agricultural lands. When ammonia is present in water at high enough concentrations, aquatic organisms cannot sufficiently excrete it, leading to toxic buildup in their internal tissues and blood, and potentially death.