EPA is issuing a significant new use rule (SNUR) under section 5(a)(2) of the Toxic Substances Control Act (TSCA) for Burkholderia cepacia complex (Bcc), a group of naturally-occurring microorganisms. Bcc microorganisms, when encountered in sufficient numbers through an appropriate route of exposure by a member of a sensitive population, such as a cystic fibrosis (CF) patient, have the potential to cause a severe infection, resulting in significantly increased rates of mortality. This rule would require persons who intend to manufacture, import, or process any individual member of Bcc for a significant new use to notify EPA at least 90 days before commencing the manufacturing (including import) or processing of Bcc for a use designated by this SNUR as a significant new use. The required notice would provide EPA with the opportunity to evaluate the intended new use and associated activities and, if necessary, to prohibit or limit that activity before it occurs.