Fw: EPA response to OMB SO2 NAAQS RIA recommendations

Lydia Wegman 

to: 

Tricia Crabtree 

06/02/2010 06:50 PM 

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 From: Lydia Wegman 

 Sent: 05/28/2010 01:36 PM EDT 

 To: "James_A ._Laity" <James_A._Laity@omb.eop.gov>; "Dominic Mancini" <Dominic_J._Mancini@omb.eop.gov> 

 Cc: "Ron Evans" <evans.ron@epa.gov> 

 Subject: Fw: EPA response to OMB SO2 NAAQS RIA recommendations 

I hope this comes through clearly. Let me know. 

 From: Lydia Wegman 

 Sent: 05/27/2010 05:58 PM EDT 

 To: James_A.._Laity@omb.eop.gov 

 Cc: Charlotte Bertrand; Bridgid Curry; Ron Evans; Amy Lamson; Neal Fann; Lydia Wegman <wegman.lydia@epa.gov>; 

Al McGartland; Tricia Crabtree 

 Subject: EPA response to OMB SO2 NAAQS RIA recommendations 

Jim,

Please find below our responses to your comments on the RIA. We believe we have addressed your first 

comment in the RIA as it currently stands and that your second comment has been resolved in prior RIAs. As we 

discussed, you and I both plan to be out of the office tomorrow and will plan to talk on Tuesday. But if you need 

to reach me tomorrow, please call my cell phone on 919-621-3125. I should be available except during our flight 

to Boston (11 AM-1 PM) and a meeting that I have between 1:30 and 2:30 PM. I will shortly be sending you our 

response to the implementation comments. Thanks and have a good weekend. 

Lydia 

Interagency Comments on SO2 NAAQS RIA 

Q1)        We understand that EPA continues to use the assumption that all species of PM 2.5 have the same toxicity.

However, it seems appropriate in the context of an RIA that focuses primarily on reducing sulfates to recognize the

epidemiological studies suggesting different toxicities from different types of PM2.5, as well as hypotheses regarding why

V, Ni, and EC/BC might be more harmful to human health than sulfates (e.g., atmospheric transformations due to oxidation

of SO2 to acid and then to chemically neutral ammonium sulfates might cause harm because metals will become more

toxic, or products of acid catalysis will be harmful).  This sensitivity to the uncertainty associated with the toxicity of sulfates

in particular could be reflected in the RIA either through a sensitivity analysis showing reduced PM co‐benefits due to

targeting of sulfates by SO2 control strategies, or through a qualitative discussion of this issue and its potential implications

for estimated PM co‐benefits. 

A1) Within three places in the RIA (i.e., the benefits chapter, the executive summary, and the cost-benefit 

comparison chapter), we acknowledge that all species of PM2.5 may not have the same toxicity and this would 

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have implications for the benefits. However, as the Integrated Science Assessment (ISA) for PM concluded, 

there is not sufficient evidence to provide a quantitative estimate of the potential implications of such differential 

toxicity. Our current write-up describes this issue qualitatively, which we believe meets the request for a 

qualitative discussion. We would need to know specifically what additional language would be needed beyond 

what is currently in the RIA. 

Q2)        We note that the sensitivity analysis that explores the implications of using a threshold model, thereby

acknowledging the greater uncertainty associated with the health effects below ambient concentrations of 8‐10 ppb, is only

presented in the Appendix of the benefits chapter.   For the purposes of transparency we encourage EPA to present a

broader range of estimates in which the threshold model of the Pope/ACS study (that is currently only presented in the

appendix) is used as the lower anchor and the no‐threshold model of the Laden study (currently presented in the body of

the chapter) is used as the upper anchor in the primary analysis.

A2) This request is inconsistent with the state of the science and the past agreed to characterization in the RIA. 

In the final PM ISA, EPA concluded that the no-threshold assumption is appropriate and CASAC did not reject 

this. We have been using the current presentation of the no threshold results in the last 10 RIAs since April 

2009. We are not aware of any change in the science to warrant a change in the presentation. Also, there is no 

appendix to the RIA; the sensitivity analysis with the threshold assumption is in the the benefits chapter of the 

RIA. 

Ron Evans 

Leader, Air Benefit & Cost Group 

HEID/OAQPS/OAR/EPA 

Mail Drop C-439-02 

919-541-5488 

919-541-0839 fax 

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