This proposal will address the Agency's residual risk and technology review (RTR) of the National Emission Standards for Hazardous Air Pollutants (NESHAP) for Leather Finishing Operations. The Leather Finishing Operations NESHAP, subpart TTTT, was promulgated pursuant to section 112(d) of the Clean Air Act (CAA) on February 27, 2002, and amended on February 28, 2005. The NESHAP established emission limitations based on maximum achievable control technology (MACT) for controlling emissions of hazardous air pollutants (HAP) from the application of the coatings, drying or curing of the coatings, and from handling, storage, and clean-up of the finishing materials. The HAP emitted include glycol ethers, chromium III, triethylamine, ethylene glycol, toluene, and methyl isobutyl ketone. This action will implement the residual risk review requirements of CAA section 112(f)(2) and the technology review requirements of CAA section 112(d)(6). The statute directs the EPA to promulgate emission standards under CAA 112(f)(2) if such standards are required to provide an ample margin of safety to protect public health or to prevent, taking relevant factors into account, an adverse environmental effect. Any such standards are to be promulgated within 8 years after promulgation of MACT standards under CAA section 112(d). CAA section 112(d)(6) requires the EPA to review and revise the MACT standards as necessary, taking into account developments in practices, processes, and control technologies, no less often than every 8 years. Pursuant to a court order related to the review of 13 source categories, the EPA must complete seven final RTR actions by December 31, 2018, and six additional RTR actions by June 30, 2020. The EPA currently plans to complete this action by December 31, 2018.