This action will address the agency's technology review under Clean Air Act (CAA) section 112(d)(6) of the National Emission Standards for Hazardous Air Pollutants (NESHAP) for four subparts in 40 CFR part 63 (subparts F, G, H, and I) that apply to the Synthetic Organic Chemical Manufacturing Industry (SOCMI) and to equipment leaks from certain non-SOCMI processes which are more commonly referred to together as the Hazardous Organic NESHAP (HON). This action will also address the agency's technology review of the NESHAP for two subparts in 40 CFR part 63 (subparts U and W) that apply to the Group I and Group II Polymers and Resins industries. The HON standards were most recently updated when the agency conducted a residual risk and technology review (RTR) on December 21, 2006. Similarly, the Group I and II Polymers and Resins NESHAP were most recently updated when the agency conducted its RTR on December 16, 2008, and April 21, 2011. The HON and Group I and II Polymers and Resins NESHAP contain maximum achievable control technology (MACT) standards for controlling emissions of hazardous air pollutants (HAP) from process vents, storage vessels, transfer operations, heat exchange systems, wastewater streams, and equipment leaks. The HAP emitted from these emission sources include, but are not limited to, ethylene oxide, benzene, 1,3-butadiene, vinyl chloride, ethylene dichloride, methanol, hexane, toluene, xylenes, and chloroprene. The agency also plans to conduct a risk assessment to consider risks from the SOCMI source category and from the Neoprene Production source category in the Group I Polymers and Resins NESHAP during its technology review and to ensure the standards continue to provide an ample margin of safety to protect public health. Lastly, this action will also address the agency's review, under CAA section 111(b)(1)(B), of four New Source Performance Standards (NSPS) in 40 CFR part 60 (subparts III, NNN, RRR, and VVa) for emissions of Volatile Organic Compound (VOC) from SOCMI air oxidation unit processes, SOCMI distillation operations, SOCMI reactor processes, and equipment leaks located at SOCMI sources. These subparts were originally promulgated pursuant to section 111(b) of the CAA on June 29,1990 (subparts III and NNN), August 31, 1993 (subpart RRR), and November 16, 2007 (subpart VVa).