### 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@o mb.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 st ands and that your second comment has been resolved in prior RIAs. As we

discussed, you and I both plan to be ou t 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 919-621-3 125. 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 comment s. 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.

A 1) Within three places in the RIA (i.e., the benefi ts 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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6/2/2010 file://C:\Documents and Settin g s\tcrabtre\Local Settin g s\Tem p \notesFCBCEE\~web1976.htmhave implications for the benefits. However, as the Integrated Science Assessment (ISA) for PM concluded,

there is not sufficient evidence to provide a quantitative es timate of the potential implic ations 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 ad ditional 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.

A 2) This request is incons istent with the state of the sci ence and the past agreed to characterization in the RIA.

In the final PM ISA, EPA concluded t hat the no-threshold assumption is a ppropriate and CASA C did not reject

this. We have been using the current presentation of th e 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 thre shold 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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