MEMORANDUM UNITED STATES ENVIRONMENTAL PROTECTION AGENCY RESEARCH TRIANGLE PARK, NC 27711

September 13, 2010 OFFICE OF AIR QUALITY PLANNING AND STANDARDS

SUBJECT: EPA's Actions in Response to the Key Recommendations ofthe Science Advisory BoardReview ofRisk and TechnologyReview (RTR) RiskAssessment Methodologies. FROM: David Guinnup, Group Leader Sector Based Assessment Group TO: EPA-HQ-OAR-2010-0600 docket On May 7, EPA's Science Advisory Board (SAB) issued its peer review report in response to a request from EPA's Office ofAir QualityPlanning and Standards (OAQPS) to convene an expert panel to review their draft document entitled, "Risk and TechnologyReview (RTR) Risk Assessment Methodologies: For Review bythe EPA's Science Advisory Board with Case Studies- MACT I Petroleum Refining Sources and Portland CementManufacturing" (June 2009) (http://yosemite.epa.gov/sab/sabproduct.nsf/4AB3966E263D943A8525771F00668381/$File/EPASAB-10-007-unsigned.pdf). This memorandum provides a summary ofthe OAQPS actions in response to the keyrecommendations ofthat report

. The five key technical recommendations from the SAB Review Panel and the ongoing and future efforts ofOAQPS to address the SAB RTR review panel recommendations are summarized below: 1. The panel recommended that the EPA modifyits RTR methodology to first assess residual risks associated with "allowable" emissions (whichreflect current regulatory limits), as opposed to developing assessments based on "actual" emissions, which are often those reportedto the National Emissions Inventory (NEI) as a starting point. To address this recommendation, current and future RTR assessments will bebased on estimates ofboth "actual" and "allowable" facility-specific emissions, to the extent that we are able to estimate them, and these results will be identified clearly in the risk assessment reports. 2. The panel recommended that a better characterization ofradionuclide emissions be developedbefore they canbe included in anyRTR assessment. Theyrecognized this in the specific case ofPortland cement facilities (one ofthe case studies used to showcase the RTRmethodologies), as well as for the general case ofother source categories whichmay emitradionuclides. However, the panel recognized that isotope-specific information, which is not currently available and for which

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### scientifically-accepted methods have notbeen fully developed, will need to be developed in order to be able to do this. The EPA plans to further characterize radionuclide emissions from the Portland cement facilities and other source categories as appropriate when better methods and data become available. 3. The panel concurred with the EPA on the use ofthe Integrated Risk Assessment (IRIS) database as the preferred database for chronic health data usedin the RTR assessments. The SAB panel recognized thatthere are greater gaps and inconsistencies in the existing acute health data when compared to existing chronic health data, and encouraged EPA to carefully examine acute toxicity values to ensure that they are protective ofsensitive subpopulations. The EPA will continue its preferred use ofiRIS for RTR assessments, and will continue to carefully examine acute toxicity values for use in assessing the potential for acute impacts ofconcern from RTR sources and source categories. 4. The panel commended EPA on the ecological risk assessment case study presented and suggested further refinements including the use ofmore established risk assessment methods and to conduct a comparison ofoutcomes with TRIM.FaTE predictions. The EPA plans to conduct an ecological risk assessment case study for an RTR facility which has been well-characterized from the standpoint ofenvironmental and ecological measurements when resources become available. 5. The panel recommended that the EPA's RTR process could presentbetter characterization ofrisks from facilities that fall into more than one regulatory category such as petroleumrefineries. The SAB panel also recommended presentingresults in a broader context ofcumulative risks including background concentrations and contributions ofmultiple sources in an area. In current and futme RTRrisk assessments, EPA will include assessments offacility-wide HAP risks (i.e., an assessment ofthe risks posed byHAP emissions from all emission points within a facility, notjust the emissions from the source categorybeing evaluated for residual risk). Ifyou have questions or need additional information please contact Dave Guinnup at (919) 541-5368.