EPA is issuing a significant new use rule (SNUR) under section 5(a)(2) of the Toxic Substances Control Act (TSCA) for the chemical substance identified as 1-Propene, 2,3,3,3-tetrafluoro- (CAS No. 754- 12-1) which was the subject of premanufacture notice (PMN) P-07-601. This action requires persons who intend to manufacture, import, or process the chemical substance for a use that is designated as a significant new use by this final rule to notify EPA at least 90 days before commencing that activity. EPA believes that this action is necessary because the chemical substance may be hazardous to human health. 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.