Industry Summary: Swine production and manure management and storage have been implicated asa major and increasing source of ammonia (NH3) emissions in North Carolina, with increasing environmental impact. Further, reports have stated that ammonium (NH4+) deposition, as measured by the National Atmospheric Deposition Program (NADP, a program established to determine long-term trends in NH4+and other nutrient deposition in the United States), increased about 100% during periods overlapping the swine-production expansion period(1990-1996)in North Carolina,without considering deposition trends before or after the industry expansion or other changes that would have contributed to NH4+depositions.As a result of this and other concerns, the North Carolina legislature enacted a moratorium on new swine farms in 1997. The swine industry questions this conjecture.Because of a lack of emissions data, the United States Environmental Protection Agency (USEPA) initiated studies across North Carolina to determine NH3emissions from livestock operations under a USEPA Air Consent Agreement with the livestock industries. These studies were undertaken from 2007 to 2009, as a National Air Emissions Monitoring Study(NAEMS)funded by participating producers. These NAEMS studies estimated that swine NH3emissions were1.5 times larger from finisher and 18.3times larger from sow production systems over what had been measured by a USDA study10 years prior. The NAEMS authors suggested their increased estimates were likely caused by different measurement approaches and climate conditions but ignored other factors that affect emissions. The swine industry challenges the accuracy of the reported increase in emissions from swine farms since over this period the industry made numerous changes to improve feed efficiency which should have reduced emissions.