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 

Board Review of Risk and Technology Review (RTR) Risk Assessment 

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 of Air Quality Planning and Standards (OAQPS) to convene an expert 

panel to review their draft document entitled, "Risk and Technology Review (RTR) Risk Assessment 

Methodologies: For Review by the EPA's Science Advisory Board with Case Studies- MACT I 

Petroleum Refining Sources and Portland Cement Manufacturing" (June 2009) 

(http://yosemite.epa.gov/sab/sabproduct.nsf/4AB3966E263D943A8525771F00668381/$File/EPASAB-10-007-unsigned.pdf). This memorandum provides a summary of the OAQPS actions in 

response to the key recommendations of that report. The five key technical recommendations from 

the SAB Review Panel and the ongoing and future efforts of OAQPS to address the SAB R TR 

review panel recommendations are summarized below: 

1. The panel recommended that the EPA modify its RTR methodology to first assess residual 

risks associated with "allowable" emissions (which reflect current regulatory limits), as opposed to 

developing assessments based on "actual" emissions, which are often those reported to the National 

Emissions Inventory (NEI) as a starting point. To address this recommendation, current and future 

RTR assessments will be based 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 of radionuclide emissions be 

developed before they can be included in any RTR assessment. They recognized this in the specific 

case of Portland cement facilities (one of the case studies used to showcase the RTR methodologies), 

as well as for the general case of other source categories which may emit radionuclides. However, 

the panel recognized that isotope-specific information, which is not currently available and for which 

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scientifically-accepted methods have not been 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 of the Integrated Risk Assessment (IRIS) 

database as the preferred database for chronic health data used in the RTR assessments. The SAB 

panel recognized that there 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 of sensitive 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 of concern 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 of more established risk assessment methods and to 

conduct a comparison of outcomes 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 of environmental and ecological measurements when resources become available. 

5. The panel recommended that the EPA's RTR process could present better characterization 

of risks from facilities that fall into more than one regulatory category such as petroleum refineries. 

The SAB panel also recommended presenting results in a broader context of cumulative risks 

including background concentrations and contributions of multiple sources in an area. In current and 

futme RTR risk assessments, EPA will include assessments of facility-wide HAP risks (i.e., an 

assessment of the risks posed by HAP emissions from all emission points within a facility, not just 

the emissions from the source category being evaluated for residual risk). 

If you have questions or need additional information please contact Dave Guinn up at (919) 

541-5368.