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This action will address the agency's residual risk and technology review (RTR) of the National Emission Standards for Hazardous Air Pollutants (NESHAP) for Ethylene Production. The Ethylene Production NESHAPs, subparts XX and YY, were promulgated pursuant to section 112(d) of the Clean Air Act (CAA) on July 12, 2002, and further amended on April 13, 2005. The NESHAP established emission limitations and work practice requirements based on maximum achievable control technology (MACT) for controlling emissions of hazardous air pollutants (HAP) from ethylene process vents, storage vessels, transfer racks, equipment, heat exchange systems and waste streams. The HAP emitted from ethylene process vents, storage vessels, transfer racks, equipment, heat exchange systems and waste streams include benzene, 1,3-butadiene, hexane, toluene and naphthalene. 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. This RTR is subject to an ongoing deadline suit, but does not have established proposal or final rule dates yet.