ENVIRONMENTAL PROTECTION AGENCY [FRL________________ ] National Ambient Air Quality Standards for Sulfur Oxides (sulfur dioxide); Intervention Level Program AGENCY: Environmental Protection Agency (EPA). ACTION: Notice. SUMMARY: The EPA is announcing today the following actions: (1) The schedule for responding to the remand of the final decision on the national ambient air quality standards (NAAQS) for sulfur dioxide (SO2) published on May 22, 1996, and any final action on the proposed intervention level program (ILP) for the reduction of SO2 emissions published on January 2, 1997. (2) The interim actions EPA will take to address 5-minute peak SO2 levels that may pose risk to sensitive asthmatic individuals. (3) The solicitation of comments and associated information and analyses on 5-minute peak SO2 concentrations in the ambient air, with emphasis on the characterization of the likelihood of exposure of sensitive asthmatic individuals to peak SO2 concentrations at 0.6 parts per million (ppm) and above during exercise. DATES: (1) The EPA will propose its response to the SO2 NAAQS remand for public comment in the summer of 1999 and take final action no later than December 2000. The EPA will take any final action on the proposed ILP, consistent with its final action on the SO2 NAAQS, no later than December 2000. (2) In the interim, until such final actions are taken, EPA will now begin taking actions to address known problem areas with high 5-minute peak SO2 levels that may pose risk to sensitive asthmatic individuals. (3) Comments and associated information and analyses should be submitted on or before November 1, 1998. ADDRESSES: Comments and associated information and analyses should be submitted to Ms. Susan Lyon Stone, U.S. Environmental Protection Agency, MD-15, Research Triangle Park, NC 27711. FOR FURTHER INFORMATION CONTACT: Ms. Susan Lyon Stone at the above address or telephone (919) 541-1146 on matters pertaining to 5-minute peak SO2 levels and the SO2 NAAQS remand. For information on the interim actions EPA plans to take to address 5-minute peak SO2 levels and the ILP, contact Mr. Eric Crump at the same address or telephone (919)541-4719. SUPPLEMENTARY INFORMATION: On May 22, 1996, EPA announced its final decision that revisions of the SO2 NAAQS were not appropriate (61 FR 25566). At issue in making that decision was whether a new 5-minute NAAQS was appropriate to protect sensitive asthmatic individuals from the risk posed by exposure to 5-minute SO2 levels of 0.6 ppm or above. Given the available health effects information; information as to the localized, infrequent, and site-specific nature of risk involved; and the advice of the Clean Air Scientific Advisory Committee (CASAC), the Administrator concluded that short-term peak concentrations of SO2 do not constitute the type of ubiquitous public health problem for which the establishment of a NAAQS would be appropriate. Because of the localized, infrequent, and site-specific nature of the risk, as characterized in its final decision notice (61 FR 25575-25576), the Administrator further concluded that the residual health risk posed by short-term SO2 concentrations remaining after attainment of the current SO2 NAAQS are most appropriately addressed by the States. It was the Administrator's judgment that the States are in a far better position than EPA to assess the highly localized and site-specific factors that determine whether occurrences of 5-minute peak SO2 concentrations in a given area pose a significant risk to sensitive asthmatic individuals in the local population, and if so, to fashion an appropriate remedial response. In light of its characterization of the nature of 5-minute peak SO2 concentrations and the likelihood that these peaks would result in exposure conditions that could cause significant health effects in sensitive asthmatic individuals during exercise, EPA also announced that it intended to propose a new program and associated guidance to assist States in determining whether 5-minute peak concentrations of SO2 in the range of 0.6 ppm to 2.0 ppm posed a significant health risk to sensitive asthmatic individuals in the local population, and if so, to identify appropriate remedial responses. Consistent with its final SO2 NAAQS decision, EPA subsequently proposed for comment the intervention level program (ILP)for the reduction of SO2 emissions on January 2, 1997 (62 FR 210). This proposed ILP was intended to supplement the protection provided by the existing primary and secondary SO2 NAAQS. A key element of the proposed ILP was the establishment (to be codified in part 51 of the CFR) of a concern level of 0.6 ppm, 5-minute average SO2 concentration, and an endangerment level of 2.0 ppm, 5-minute average. The proposed ILP would require that State and tribal plans contain the authority to take whatever action is necessary to prevent further exceedances of such concern and endangerment levels when the State/tribe determines that intervention is appropriate. The proposed ILP includes a discussion of the factors that the State/tribe should consider in making such determinations, including the magnitude and frequency of peak concentrations exceeding these levels, the history and nature of any citizen complaints, available information on potential exposure of sensitive asthmatic individuals, and information about the source(s) causing the peak SO2 concentrations. Based on the above factors, the proposed ILP provides for flexibility for the State/tribe to determine the nature and degree of intervention that is warranted in any area. The States/tribes are also given the flexibility in the proposed ILP to relocate existing monitors to areas where 5-minute peak concentrations may be of concern through changes to SO2 monitoring requirements. The proposed ILP recognizes that authority to take such actions, when justified on a case-by-case basis, currently exists under section 303 of the Clean Air Act. Building upon this authority, the proposed ILP codifies the health benchmarks for such actions (i.e., the concern and endangerment levels) and provides guidance to assist States/tribes in identifying and taking appropriate actions. SO2 NAAQS Remand In July 1996, the American Lung Association and the Environmental Defense Fund petitioned the District of Columbia Court of Appeals for judicial review of EPA's decision not to establish a new 5-minute NAAQS. On January 30, 1998, the court issued a decision in that case [American Lung Association v. Browner, No. 96-1251 (D.C. Cir.)]. The court found that EPA failed to provide an adequate explanation for its determination that no revision to the SO2 NAAQS was appropriate. As a result, the court remanded the case to permit EPA to more fully explain its decision not to set a standard for short-term peak SO2 levels of 0.6 ppm or greater. Schedule for EPA Final Actions In remanding the case to EPA, the court did not establish a deadline for EPA to take action consistent with the remand. In lieu of pursuing further litigation to seek a court-ordered schedule for EPA's response to the SO2 NAAQS remand, the petitioners in the case initiated discussions with EPA to establish such a schedule for EPA's response. Based on these discussions, it was agreed that EPA would take final action no later than December 2000. In order to meet this date for final action, EPA intends to propose for public comment its response to the remand by the summer of 1999. In conjunction with taking final action on its response to the SO2 NAAQS remand, EPA also intends to take any final action on the ILP no later than December 2000. In so doing, EPA will draw upon its response to the remand on the SO2 NAAQS decision so as to ensure consistency between these actions. Interim Actions Between now and when final action on the SO2 NAAQS remand and the ILP is taken, EPA intends to work with States/tribes with known areas of high 5-minute peak SO2 concentrations to undertake a number of actions. These actions include the following: determining whether the existing SO2 NAAQS and State Implementation Plan (SIP) requirements are being met in such areas; taking regulatory action in such areas where appropriate (e.g., SIP calls); and initiating enforcement review/action to ensure SIP requirements are met. The EPA also plans to issue monitoring and other guidance to States/tribes/regions to assist them in identifying and addressing high 5-minute peak problems. Solicitation of Information on 5-Minute Peak SO2 Concentrations To supplement its current information on 5-minute peak SO2 concentrations and exposures of sensitive asthmatic individuals to peak levels of concern, EPA is soliciting comments and associated information and analyses on such 5-minute peak SO2 concentrations. The EPA will consider this information in the context of the interim actions described above and in its response to the remand and in its final ILP decision. More specifically, EPA solicits information and analyses on the following: sources or source types and the nature of events that are most likely to give rise to short-term peak SO2 levels; the magnitude and frequency of such peaks; the time of day of the occurrence of such peaks; meteorological conditions in the area in which such peaks occur; the density of the population near the source(s) involved; and the frequency with which asthmatic individuals would likely be exposed to peak SO2 concentrations at 0.60 ppm and above while at elevated ventilation rates (i.e., during exercise). ______________________ Dated ______________________ Richard D. Wilson Acting Assistant Adminstrator for Air and Radiation