This action reestablishes emission guidelines for existing small municipal waste combustion (MWC) units. The emission guidelines contain stringent emission limits for organics (dioxins/furans), metals (cadmium, lead, mercury, and particulate matter), and acid gases (hydrogen chloride, sulfur dioxide, and nitrogen oxides). Some of those pollutants can cause toxic effects such as eye, nose, throat, and skin irritation, and blood cell, heart, liver, and kidney damage. Emission guidelines for small MWC units were originally promulgated in December 1995, but were vacated by the U.S. Court of Appeals for the District of Columbia Circuit in March 1997. In response to the 1997 vacature, on August 30, 1999, EPA proposed to reestablish emission guidelines for small MWC units. The emission guidelines contained in this final rule are equivalent to the 1995 emission guidelines for small MWC units.