EPA intends to propose a significant new use rule (SNUR) under section 5(a)(2) of the Toxic Substances Control Act (TSCA) for 2,4-toluene diisocyanate, 2,6-toluene diisocyanate, toluene diisocyanate unspecified isomers (these three chemical substances are hereafter referred to as toluene diisocyanates or TDI) and related compounds (toluene diisocyanate trimer, poly(toluene diisocyanate), toluene diisocyanate dimer, and toluene diisocyanate cyclic trimer). Diisocyanates are well known dermal and inhalation sensitizers in the workplace and have been documented to cause asthma, lung damage, and in severe cases, fatal reactions. Worker exposures are already subject to protective controls in occupational settings, but EPA is concerned about potential health effects that may result from exposures to the consumer or self-employed worker while using products containing uncured TDI and its related polyisocyanates (e.g., spray-applied sealants and coatings) or incidental exposures to the general population while such products are used in or around buildings including homes or schools. The SNUR would require persons who intend to manufacture (including import) or process these chemical substances for an activity that is designated as a significant new use by the proposed rule to notify EPA at least 90 days before commencing that activity. EPA also intends to propose to make the general SNUR article exemption for persons who import or process these chemical substances as part of an article inapplicable. The required notification would provide EPA with the opportunity to evaluate the intended use and, if necessary, to prohibit or limit that activity before it occurs.