Section 111(b)(1) of the Clean Air Act (CAA) directs EPA to review and, if appropriate, revise the New Source Performance Standards (NSPS) at least every 8 years after promulgation. This is a review of subpart BB, Standards of Performance for Kraft Pulp Mills Section 60.280 - 60.285 which was promulgated in 1978 and last reviewed in 1986. The subpart is applicable to the following sources in kraft pulp mills that were installed after 1978: digester systems, brown stock washers, evaporator systems, recovery furnaces, smelt dissolving tanks, lime kilns, and condensate stripper systems. The pollutants regulated in this subpart include total reduced sulfur (TRS) compounds and particulate matter (PM). This action is subject to a citizen suit under section 304(a)(2) of the Clean Air Act brought against the US EPA under the Administrative Procedure Act, 5. U.S.C. 701-06. This action will fulfill our mandatory obligation to review the NSPS for new and modified kraft pulp mills.