This action will complete Clean Air Act (CAA) section 112(d)(6) technology reviews of the National Emission Standards for Hazardous Air Pollutants (NESHAP) for the Pulp and Paper Industry (40 CFR part 63, subpart S) and the NESHAP for Chemical Recovery Combustion Sources at Kraft, Soda, Sulfite, and Stand-Alone Semichemical Pulp Mills (40 CFR part 63, subpart MM). This action will also complete a CAA section 111(b)(1)(B) technology review of the New Source Performance Standards (NSPS) for Kraft Pulp Mills (40 CFR part 60, subpart BBa). EPA promulgated the residual risk and technology review (RTR) of the NESHAP for the Pulp and Paper Industry in 2012, while the RTR of the NESHAP for Chemical Recovery Combustion Sources was promulgated in 2017. The most recent technology review of the NSPS for Kraft Pulp Mills was promulgated in 2014. The NESHAPs establish emission limitations based on the maximum achievable control technology (MACT) for controlling hazardous air pollutants (HAP). Subpart MM regulates chemical recovery combustion sources such as recovery furnaces, lime kilns, and smelt dissolving tanks at kraft, soda, sulfite, and semi-chemical pulp mills. Subpart S regulates non-combustion sources at facilities that manufacture pulp, paper, or paperboard. Subpart BBa regulates particulate matter and total reduced sulfur from certain sources at kraft pulp mills that were constructed, reconstructed, or modified after May 23, 2013. CAA section 112(d)(6) requires EPA to review and revise MACT standards as necessary, taking into account developments in practices, processes and control technologies, no less often than every 8 years. In 2020, the Court of Appeals for the D.C. circuit ruled in Louisiana Environmental Action Network (LEAN) v EPA, that EPA has an obligation to establish standards for unregulated HAP emissions during the 8-year technology review. This action will establish standards for unregulated HAP emissions within the pulp and paper source category, while also reviewing existing standards promulgated under the three subparts.