COMMENTS OF THE UTILITY AIR REGULATORY GROUP

ON EPA’S PROPOSED RULE ON THE PRIMARY NATIONAL 

AMBIENT AIR QUALITY STANDARD FOR SULFUR DIOXIDE

(74 FED. REG. 64810 (DECEMBER 8, 2009)) 

DOCKET ID NO. EPA-HQ-OAR-2007-0352 

 HUNTON & WILLIAMS LLP 

 LUCINDA MINTON LANGWORTHY

 E. CARTER CHANDLER CLEMENTS

 1900 K STREET, NW 

 WASHINGTON, DC 20006 

 (202) 955-1500 

 COUNSEL FOR THE UTILITY AIR

 REGULATORY GROUP

 FEBRUARY 8, 2010
1

COMMENTS OF THE UTILITY AIR REGULATORY GROUP

ON EPA’S PROPOSED RULE ON THE PRIMARY NATIONAL AMBIENT 

AIR QUALITY STANDARD FOR SULFUR DIOXIDE

(74 FED. REG. 64810 (DECEMBER 8, 2009))

On December 8, 2009, the United States Environmental Protection Agency 

(“EPA” or the “Agency”) proposed revisions to its primary National Ambient Air Quality 

Standards (“NAAQS”) for sulfur dioxide (“SO2”). 74 Fed. Reg. 64810 (Dec. 8, 2009) 

(“Proposed Rule”). Specifically, the Agency proposed to adopt a new SO2 NAAQS to 

limit the annual 99th percentile daily maximum hourly SO2 concentration, averaged over 

three years, to a level within the range of 50 to 100 parts per billion (“ppb”) and to 

revoke the present annual arithmetic average standard of 0.03 parts per million (“ppm”) 

(30 ppb) and 24-hour average standard of 0.14 ppm (140 ppb) that may not be 

exceeded more than once a year. Id. at 64810/1. EPA also sought comment on the 

alternative of a daily maximum 1-hour SO2 standard as high as 150 ppb. Id. at 64845/1. 

Finally, the Agency addressed various provisions for implementing any new SO2

NAAQS. Id. at 64846/1 - 64864/3. 

These are the comments of the Utility Air Regulatory Group (“UARG”) on the 

Proposed Rule.1

 UARG has participated actively throughout the current review of the 

SO2 NAAQS, submitting comments to EPA and to its Clean Air Scientific Advisory 

Committee (“CASAC” of the “Committee”) on drafts of the Integrated Science 

 1

 UARG is a voluntary, nonprofit group of individual electric generating utilities 

and industry trade associations. UARG’s purpose is to participate on behalf of its 

members collectively in EPA’s rulemaking and other Clean Air Act proceedings that 

affect the interests of electric generators, and in related litigation. Since 1977, UARG 

has participated in virtually all key rulemakings, related litigation, and other arenas of 

policy development under the Clean Air Act that affect electric utility companies. 
2

Assessment (“ISA”),2 and of the Risk and Exposure Assessment (“REA”)3 on which the 

Administrator relies in the Proposed Rule.4

 Those comments, which are hereby 

incorporated by reference in these comments on the Proposed Rule itself, address in 

 2

 EPA, Integrated Science Assessment for Sulfur Oxides -- Health Criteria 

(September 2008).

3

 EPA, Risk and Exposure Assessment to Support the Review of the SO2

Primary National Ambient Air Quality Standards: Final Report (July 2009).

4 See Comments of the Utility Air Regulatory Group on the Risk and Exposure 

Assessment to Support the Review of the SO2 Primary National Ambient Air Quality 

Standards: Second Draft (March 2009) (Docket ID. No. EPA-HQ-OAR-2007-0352-

0031.1) (June 11, 2009) (“Second Draft REA Comments”); Anne E. Smith, Ph.D., 

Comments to CASAC on Draft #2 of the SO2 Risk And Exposure Assessment, Public 

Comments Session, CASAC Meeting (Apr. 16-17, 2009) (Comments prepared on 

behalf of UARG), available at

http://yosemite.epa.gov/sab/SABPRODUCT.NSF/PeopleSearch/F99F04D90A9425BE8

52575450067337C?OpenDocument; Comments of the Utility Air Regulatory Group on 

the First External Review Draft of the Risk and Exposure Assessment to Support the 

Review of the SO2 Primary National Ambient Air Quality Standards: Second Draft (July 

2008) (Docket ID No. EPA-HQ-OAR-2007-0352-0014.1) (Aug. 28, 2008, corrected 

Sept. 4, 2008) (“First Draft REA Comments”); Comments of the Utility Air Regulatory 

Group on the Second External Review Draft of the Integrated Science Assessment for 

Sulfur Oxides -- Health Criteria (May 2008) (Docket ID No. EPA-HQ-ORD-2006-0260-

0020.1) (Aug. 11, 2008) (“Second Draft ISA Comments”); Timothy H. Savage, Ph.D., 

Comments on Risk and Exposure Assessment to Support the Review of the SO2

Primary National Ambient Air Quality Standards: First Draft (Presentation on behalf of 

UARG to CASAC meeting of Dec. 5-6, 2007); J. Turim, Ph.D., S. Moolgavkar, M.D., 

Ph.D., E. Anderson, Ph.D., A.T.S.F., Comments on EPA’s Integrated Science 

Assessment for Sulfur Oxides -- Health Criteria: Summary (Dec. 3, 2007) (written 

presentation to CASAC meeting of Dec. 5-6, 2007); Comments of the Utility Air 

Regulatory Group on the First External Review Draft of the Integrated Science 

Assessment for Sulfur Oxides -- Health Criteria (Sept. 2007) (Docket ID No. EPA-HQORD-2006-0260-0009.1) (Nov. 30, 2007) (“First Draft ISA Comments”). Statements to 

CASAC do not appear to have been added to the public docket, although EPA states 

that the Administrator considered them in developing her rationale for the Proposed 

Rule. 74 Fed. Reg. at 64814/2. Copies of the presentations to CASAC by Timothy H. 

Savage, Ph.D. and by J. Turim, Ph.D., et al. are attached hereto as Attachments A and 

B respectively. 
3

detail EPA’s assessment of the science concerning SO2 health effects and the risk of 

such health effects in contemporary ambient American air. 

For the reasons explained below and in those earlier comments, UARG does not 

support the proposed 1-hour NAAQS in the range of 50 to 100 ppb, or even one at the 

alternative 150 ppb level. The human clinical evidence concerning health effects 

potentially associated with SO2 is not indicative of adverse effects in the most sensitive 

population, exercising asthmatics, from exposure to short-term SO2 peaks of less than 

600 ppb. The epidemiological evidence cannot determine that SO2 is a cause of or a 

contributor to hospital admissions (“HA”), emergency department (“ED”) visits or 

respiratory symptoms, the effects cited in the Proposed Rule. See 74 Fed. Reg. at 

64818/1-2. Moreover, as demonstrated in the REA, a 1-hour NAAQS in the range of 50 

to 150 ppb would not reduce the risk of such effects in current ambient air. Thus, no 

such standard is requisite (or necessary) to protect the public health with an adequate 

margin of safety. Even if EPA rejects UARG’s advice on the lack of justification for a 

new standard, however, the Agency should modify some aspects of its plans for 

implementing any new NAAQS. 

I. Scientific Information Does Not Demonstrate that Short-term SO2 

Concentrations Below 600 ppb Cause Potentially Adverse Effects on Public 

Health. 

Section 109 of the Clean Air Act (“CAA” or the “Act”) requires the EPA 

Administrator (“Administrator”) to set primary NAAQS for certain criteria pollutants, 

including SO2, at levels that in her judgment are “requisite to protect the public health” 

while “allowing an adequate margin of safety.” 42 U.S.C. § 7409(b)(1), CAA § 109(b)(1) 

(hereinafter, citations are given only to the Act). In determining what level is requisite to 

protect public health, she must consider the health of sensitive groups (or 
4

subpopulations), such as those with particular medical conditions and those in particular 

age groups, but not the most sensitive individuals within those groups. See S. Rep. 

1196 at 10 (1970), reprinted in 1 A LEGISLATIVE HISTORY OF THE CLEAN AIR ACT 

AMENDMENTS OF 1970 410 (1974) (“1970 Legis. Hist.”). 

Interpreting this congressional instruction not long after it was given, EPA 

established the initial NAAQS for lead at a level that it estimated would protect 99.5% of 

children under five years of age (which it identified as a the group most sensitive to lead 

exposure) against “potentially adverse” health effects. 43 Fed. Reg. 46246 (Oct. 5, 

1978). At that time, EPA recognized that certain children might be at “enhanced risk” 

due to factors such as genetics, diet or residence, but did not treat them as an even 

more susceptible subgroup. See id. at 46252. The U.S. Court of Appeals for the 

District of Columbia upheld the lead NAAQS. See Lead Indus. Ass’n v. EPA, 647 F.2d 

1130 (D.C. Cir. 1980). Indeed, EPA has consistently acknowledged that NAAQS are 

not intended to protect each member of a sensitive group or subpopulation.5

 

Further, Congress intended the NAAQS to protect the public against the risk of 

“adverse” health effects, 1970 Legis. Hist. at 410, not all health effects. EPA has 

therefore always set primary NAAQS at the level the Administrator judges adequate to 

protect public health from only such adverse effects. See, e.g. 36 Fed. Reg. 8186, 

8186/2 (Apr. 30, 1971) (noting that the Administrator “has in each case promulgated a 

national primary standard which includes a margin of safety adequate to protect the 

public health from adverse effects suggested by the available data.”). The level for such 
5

a standard need not protect against all risks, only “significant” ones. See Ethyl Corp. v. 

EPA, 541 F.2d 1, 12-32 (D.C. Cir. 1976). EPA has acknowledged that NAAQS are not 

to be “zero risk” standards.6

 In determining the significance of the risk posed by the 

pollutant (in this case SO2) in the ambient air, the Administrator must consider that risk 

in the context of the real world. Whitman v. Am. Trucking Ass’ns, 531 U.S. 457, 494-95 

(2001) (Breyer, J., concurring in part and concurring in judgment). 

The Administrator must base her judgment concerning the adversity of effects 

and the significance of risks posed by a pollutant like SO2 on air quality criteria that 

“adequately reflect the latest scientific knowledge useful in indicating the kind and extent 

of all identifiable effects on human health . . . which may be expected from the presence 

of such pollutant in the ambient air in varying quantities.” CAA § 108(a)(2). She may 

not set a NAAQS at a level that is more stringent than necessary to protect public health 

with an adequate margin of safety. Whitman, 531 U.S. at 473, 476. In reaching her 

judgment, she must consider advice received from CASAC but is not bound to follow 

that advice or draw the same conclusions as drawn by that Committee. See CAA § 

307(d)(3) (stating that if the Administrator’s proposal in a proposed rulemaking “differs in 

any important respect” from CASAC’s advice, the Administrator must include an 

explanation for such differences in the proposed rule); Am. Farm Bureau Fed’n v. EPA, 

559 F.3d 512, 522 (D.C. Cir. 2009) (remanding but not vacating a rule on the PM 

 5 See, e.g., 74 Fed. Reg. 34404, 34405 n.1 (July 15, 2009); 73 Fed. Reg. 16436, 

16437 n.1 (Mar. 27, 2008); 71 Fed. Reg. 61144, 61145 n.1 (Oct. 17, 2006); 44 Fed. 

Reg. 8202, 8210/1 (Feb. 8, 1979). 

6 See e.g., 62 Fed. Reg. 38856, 38857/2 (July 18, 1997); 62 Fed. Reg. 38652, 

38653/2 (July 18, 1997). 
6

NAAQS, holding that the Administrator had failed to provide a sufficient explanation for 

not following CASAC’s advice, but stating that if the Agency could explain its decision 

adequately, it was free not to follow CASAC’s advice). 

Indeed, the Administrator may not delegate judgment regarding the requisite 

levels for the NAAQS to any person. CAA § 301. It is the Administrator who must 

“make a judgment as to the level of physiological response that should be considered 

adverse.” 50 Fed. Reg. 37484, 37496/1 (Sept. 13, 1985). Additionally, when reviewing 

an existing NAAQS (which previously was determined to be at the level requisite to 

protect human health according to the CAA), the Administrator must provide a reasoned 

explanation for any conclusion that the existing NAAQS is no longer at the level 

requisite to protect public health with an adequate margin of safety.7

In the last review of the primary NAAQS for SO2, the Administrator concluded 

that no revision of the existing NAAQS was necessary at that time to protect public 

health. 61 Fed. Reg. 25566 (May 22, 1996) (“1996 NAAQS Rule”). Focusing on the 

same types of lung function changes and respiratory symptoms in exercising asthmatics 

that are at issue in the current proceeding (i.e., increased specific airway resistance 

(“sRaw”), decreased forced expiratory volume (“FEV”), and respiratory symptoms such 

as chest tightness, wheezing and shortness of breath),8

 the Administrator noted that 

 7 See Motor Vehicle Mfrs. Ass’n v. State Farm Mut. Auto. Ins. Co., 463 U.S. 29, 

42 (1983) (“an agency changing course by rescinding a rule is obligated to supply a 

reasoned analysis for the change beyond that which may be required when an agency 

does not act in the first instance”); Atchison, Topeka and Santa Fe Ry. Co. v. Wichita 

Bd. of Trade, 412 U.S. 800, 808 (1973) (an agency must “explain its departure from 

prior norms”); AT&T Corp. v. FCC, 263 F.3d 729, 736 (D.C. Cir. 2001) (reasoned 

decision making standard requires explanation of departure from prior decision). 

8 Id. at 25570/3. 
7

variability in lung function is a typical feature of asthma.9 She recognized that lung 

function in asthmatics tends to be better at certain times of the day than at others and 

may be affected by a variety of common stimuli, such as cold air, pollen and other 

allergens, which asthmatics encounter on a daily basis.10 Exercise alone triggers 

bronchoconstriction in many asthmatics, a condition that is exacerbated if the exercise 

takes place in cold, dry (albeit clean) air.11 Additionally, the Administrator noted that 

asthmatic responses to peak SO2 exposure are transient -- unlike health effects 

associated with other stimuli, such as pollen, there are no “late phase” responses -- lung 

function typically returns to normal within an hour after exercise or exposure to SO2

ends.12 She also noted that the responses in asthmatics to SO2 during exercise are 

“transient,” generally returning to normal within an hour. Id. at 25570/3. Lung function 

started to improve if the exercise stopped, even if the SO2 exposure continued. Id. at 

25572/2. The Administrator concluded that “repeated occurrences” -- as opposed to a 

single incident -- of the responses of the more sensitive asthmatic subjects to SO2

concentrations in the range of 0.6 to 1.0 ppm “should be regarded as significant from a 

public health standpoint.” Id. at 25573/3.13 Taking into account the infrequent, localized 

 9 Id. at 25570/3. 

10 Id. at 25570/2-3. 

11 Id. at 25570/3. 

12 Id. at 25570/3. The responses often diminished even as the SO2 exposure 

and exercise continued. See Linn WS, Avol EL, Peng RC, Shamoo DA, Hackney JD. 

(1987) Replicated Dose-Response Study of Sulfur Dioxide Effects in Normal, Atopic, 

and Asthmatic Volunteers. Am. Rev. Respir. Dis. 136:1127-34, at 1129. 

13 The Administrator noted that the effects in asthmatics exercising in 0.6 ppm 

were more pronounced than those in asthmatics exercising in lower SO2

(continued on next page) 
8

and site-specific nature of the responses, the Administrator concluded that revision of 

the NAAQS was not warranted. Id. at 25575/3. 

In response to a challenge of the 1996 NAAQS Rule by the American Lung 

Association and the Environmental Defense Fund, the U.S. Court of Appeals for the 

District of Columbia Circuit held that the Administrator is required to provide an 

explanation of her use of the discretion delegated to her under the CAA. See Am. Lung 

Ass’n v. EPA, 134 F.3d 388, 392 (1998) (“Where . . . Congress has delegated to an 

administrative agency the critical task of assessing the public health and the power to 

make decisions of national import . . . that agency has the heaviest of obligations to 

explain and expose every step of its reasoning.”). The court remanded the 1996 

NAAQS Rule to the Agency, not because it disagreed with the Administrator’s 

interpretation of the scientific evidence, but because the Administrator had not 

explained adequately her judgment that the existing NAAQS were requisite to protect 

public health, and therefore did not require revision. See id. at 392-93 (“[T]he 

Administrator may well be within her authority to decide that [the existing NAAQS is 

requisite to protect public health]. But unless she describes the standard under which 

she has arrived at this conclusion . . . we have no basis for exercising [judicial review] . . 

. . Given the gaps in the Final Decision’s reasoning, we must remand this case to permit 

the Administrator to explain her conclusions more fully.”). 

In the Proposed Rule, the Administrator fails to provide a reasoned explanation 

for changing course by now concluding that the existing NAAQS do not to protect public 

 

concentrations. Id. at 25571/2. In addition to pointing to group mean decreases in FEV 

of 15% or greater at 0.6 ppm SO2, she pointed to sRaw increases of 200% or greater 

(continued on next page) 
9

health with an adequate margin of safety and require revision. See Motor Vehicle Mfrs 

Ass’n, 463 U.S. at 42. She has not explained why the “latest scientific knowledge” now 

indicates an adverse effect on human health “which may be expected from the 

presence of [SO2] in the ambient air.” CAA § 108(a)(2). She has failed to justify her 

conclusion that effects that were not considered adverse in 1996 should be deemed 

adverse now. 

A. New clinical evidence does not justify a change in conclusions from the 

prior review. 

The Proposed Rule states that EPA’s conclusion that there is a causal 

relationship between respiratory morbidity and short term SO2 exposure is based 

primarily on human clinical studies. 74 Fed. Reg. at 64816/2. The new clinical 

evidence presented in the ISA, however, does not represent a change in the character 

of the scientific evidence regarding effects of SO2 exposure since the last review.14 

Rather, the changed conclusions are the result of changes in EPA’s interpretation of the 

evidence. Only if she can supply a “reasoned analysis” for these changes can the 

Administrator rely on them for a change to the 1996 conclusion that effects of public 

health significance begin at 600 ppb, or for a reversal of the 1996 decision that no new 

short-term NAAQS was needed to protect public health with an adequate margin of 

safety. She has failed to present such an analysis. See 61 Fed. Reg. at 25573/3. 

EPA’s definition in the Proposed Rule of what constitutes an adverse health 

effect is inconsistent with the definition of effects considered to be of public health 

 

and FEV decreases of 20% or greater in some individuals. Id. at 25571/2. 

14 See id. at 64816/3 (describing the newer human clinical studies as “supportive” 

of the evidence considered in the last review). 
10

significance in 1996, and with the definition’s purported basis. The Administrator 

acknowledges that her definition of adversity is different from that in the 1996 review. 

Specifically: 

[W]hereas the conclusions in the prior review of the SO2

NAAQS were based on SO2 exposure concentrations which 

resulted in large decrements in lung function and moderate 

to severe respiratory symptoms, the ISA’s current review of 

data from controlled human exposure studies focused on 

moderate to large SO2-induced decrements in lung function 

and/or respiratory symptoms ranging from mild . . . to 

severe. 

74 Fed. Reg. at 64816/2. 

The genesis of this change is obscure. First, the Proposed Rule seems to 

postulate that the health risk to asthmatics who experience lung function effects without 

symptoms might be greater than the health risk to those who experience both 

symptoms and lung function decrements. See id. at 64816/2. It is simply implausible 

that a failure to experience symptoms is worse than having them. Second, the 

Proposed Rule points to advice from CASAC as justification for the focus on moderate 

as well as large lung function decrements. Id. at 64817/3. But the Administrator culls 

this advice from comments of individual CASAC members in the transcript of a CASAC 

meeting; it is not reflected in the letter from the complete CASAC that followed that 

meeting. Finally, the Administrator simply provides no explanation of why she now 

considers mild symptoms to be adverse health effects. Clearly, this does not constitute 

a reasoned analysis in support of the change to the definition of adversity. 

The Administrator also states that the Agency’s definition of “adversity” is derived 

from a statement of the American Thoracic Society (“ATS”). See id. at 64816/3. In the 

Proposed Rule, however, EPA mischaracterizes and deviates substantially from the 
11

ATS adversity definition. According to ATS, “a small, transient loss in lung function, by 

itself, should not automatically be designated as adverse,” but should only be 

considered adverse when accompanied by symptoms. American Thoracic Society, 

What Constitutes an Adverse Health Effect of Air Pollution?, 161 Am. J. Respir. Crit. 

Care Med. 665, 670 (2000) (hereinafter “ATS Statement”). Additionally, ATS considers 

symptoms to be adverse at the individual level when they decrease quality of life or 

cause a change in clinical status. Id. at 671. As quoted above, though, in the Proposed 

Rule and contrary to the ATS Statement, EPA states that it is treating lung function 

decrements accompanied by even mild symptoms to be adverse effects. 74 Fed. Reg. 

at 64816/3. 

With respect to adversity at the population level, based on the ATS Statement, 

the Proposed Rule argues that “an air pollution-induced shift in a population distribution 

of a given health-related endpoint (e.g. lung function) should be considered adverse, 

even if this shift does not result in the immediate occurrence of illness in any one 

individual in the population.” Id. at 64816/3. The Proposed Rule attributes this 

definition of an adverse effect to the ATS Statement. However, EPA is not applying the 

ATS Statement appropriately in this context. 

ATS gives the following illustration of its population level standard: 

A population of children with asthma could have a 

distribution of lung function such that no individual child has 

a level associated with impairment. Exposure to air pollution 

could shift the distribution toward lower levels without 

bringing any individual child to a level that is associated with 

clinically relevant consequences. Individuals within the 

population would, however, have diminished reserve 

function and are at potentially increased risk if affected by 

another agent, e.g. a viral infection. 
12

ATS Statement at 668. 

The scenario that ATS sets forth does not apply to the risks associated with SO2

exposure primarily for two reasons. First, when they occur, the effects of SO2 exposure 

on exercising asthmatics (the sensitive subpopulation here, analogous to the asthmatic 

children in the ATS illustration) are transient. See discussion supra at p. 7. As EPA has 

acknowledged, lung function returns to baseline levels within an hour, when either 

exercise or SO2 exposure ceases. Therefore, a detectable shift in the lung function of 

the asthmatic population would never occur such that the population would become 

more susceptible to other agents as a result of diminished reserve capacity. Moreover, 

variation in lung function is a characteristic of asthma. See supra at 6-7. Second, in 

evaluating the effects of SO2 exposure on public health in this review, the Administrator 

has focused on the responses of a small group of individuals that has responded to 

lower levels of SO2 than the rest of the exercising asthmatic subjects. See, e.g., 74 

Fed. at 64842/2. As described infra at p. 14-15, there is no indication that these 

individuals are a distinct subpopulation that may be affected in the manner described in 

the ATS Statement. 

It is unclear why the Administrator diverges from the guidance of the ATS 

Statement in determining adversity at the individual level or why she applies ATS’s 

definition of adversity at the population level, without explanation, to a scenario to which 

the definition is not applicable. It appears that she may be interpreting the ATS 

Statement in a manner that supports her own speculation about the scientific research. 

Indeed, the Administrator’s conclusions in the Proposed Rule are based in large 

part on speculation. The range of possible levels for the proposed 1-hour NAAQS in the 
13

Proposed Rule is justified in part on the basis that the participants in the clinical studies 

are most likely not the most severe asthmatics, see id. at 64844/2, and that more 

severe asthmatics may respond to lower levels of SO2. There is a significant legal 

problem with the Agency’s reasoning -- the Administrator’s judgment must reflect the 

“latest scientific knowledge” regarding the relevant health effects from SO2 in the 

ambient air, CAA § 108(a)(2), and she may not base her judgment on speculation. Am. 

Petroleum Inst. v. Costle, 665 F.2d 1176, 1186-87 (D.C. Cir. 1981) (“[T]he 

Administrator’s conclusions must be supported by the record, and [s]he may not engage 

in sheer guesswork.”). It is clearly speculative for the Administrator to base the level of 

the proposed NAAQS on the idea that individuals with asthma more severe than those 

that participated in clinical studies may experience health effects at lower levels -- there 

is nothing to support the idea that more severe asthmatics are likely to respond to lower 

levels of SO2 -- in fact, there is evidence to the contrary. 

There is published, peer-reviewed clinical evidence that, among asthmatics, 

responses to SO2 exposure are not dependant on the clinical severity of asthma. Linn, 

et al. (1987) tested the effect of SO2 exposure on lung function in exercising asthmatics, 

including a group of “minimal/mild” asthmatics and a group of “moderate/severe” 

asthmatics, and found that responses to SO2 were not predictable based on either the 

severity of the disease or the subjects’ tolerance for exercise.15 In fact, the Linn study 

concluded that “the subjects at highest risk [of temporary respiratory disturbances from 

 15 Linn WS, Avol EL, Peng RC, Shamoo DA, Hackney JD. (1987) Replicated 

Dose-Response Study of Sulfur Dioxide Effects in Normal, Atopic, and Asthmatic 

Volunteers. Am Rev Respir Dis 136:1127-34. 
14

ambient SO2] can be identified only by actually measuring their responses to SO2.”16 

EPA is aware of the Linn study -- it is cited in the Proposed Rule to support the 

proposition that SO2-induced responses for individuals are reproducible. 74 Fed. Reg. 

at 64824/2. Thus, the Administrator acknowledges the portion of Linn’s findings that 

seems consistent with her speculation -- that an asthmatic participant’s sensitivity to 

SO2 exposure was predictable on an individual basis (the same participants were 

shown to exhibit the same level of sensitivity to SO2 in repeated trials) -- but ignores 

Linn’s main finding -- that an asthmatic participant’s sensitivity to SO2 exposure was not

predictable based on the severity of the participant’s asthma. The inappropriateness of 

the Administrator’s speculation, therefore, is exacerbated by the fact that she ignores 

scientific evidence that contradicts her assumption. 

The Proposed Rule also states that EPA believes that 200 ppb does not 

represent a threshold below which adverse effects do not occur, based only on the fact 

that a relatively small percentage (5-30%) of exercising asthmatics experienced lung 

function decrements at 200-300 ppb, the lowest level tested in chamber studies. Id. at 

64822/1. The Administrator’s reliance on her assumption that some asthmatics will 

respond to SO2 exposure at levels lower than other asthmatics is also contrary to 

congressional intent. As mentioned above, in setting the NAAQS, the Administrator 

must consider the health of sensitive subpopulations, but not the most sensitive 

individuals within those subpopulations. See discussion supra at p. 3-4. Asthmatics are 

a distinct subpopulation definable by biological criteria, and it is appropriate for the 

Administrator to consider the unusual susceptibility of asthmatics to SO2 exposure in 

 16 Id. at 1132. 
15

setting the standard. However, it is beyond her authority to base her judgment on a 

consideration that certain individuals respond to lower levels of SO2. These 

“responders” are not a sensitive subpopulation; they are merely individuals with no 

identifiable common characteristics. Even ATS recognizes that “[r]esearch now shows 

that some highly susceptible individuals may respond to common exposures that are 

often unavoidable . . . [and that] by definition, susceptible individuals cannot have the 

same margin of safety as the nonsusceptible groups within the population.” ATS 

Statement at 669. It is inappropriate for the Administrator to consider these responders 

and to extrapolate from individual results to assume without evidence that these 

responders are part of some unidentified subpopulation. 

In short, the Administrator has not provided a reasoned explanation for her 

definition of what constitutes an adverse health effect for purposes of interpreting the 

evidence from human clinical studies. Responses of exercising asthmatics to SO2

exposure in recent studies merely support the findings of studies considered in 

promulgating the 1996 NAAQS Rule. Indeed, the lowest SO2 concentration that 

arguably represents a public health concern among exercising asthmatics continues to 

be 600 ppb, as it was in 1996. The Administrator’s speculation in the Proposed Rule 

that there may be a population of severe asthmatics or subset of asthmatics that is 

more sensitive to exposure at lower SO2 concentrations is unavailing. The clinical 

studies do not support a conclusion that even exercising asthmatics require protection 

from brief SO2 exposures below 600 ppb. 
16

B. New epidemiological evidence does not justify change in conclusions from 

prior review 

The Proposed Rule states that in addition to clinical studies, “the ISA based its 

causal finding of an association between short-term . . . exposure to SO2 and 

respiratory morbidity on results from epidemiologic studies of respiratory symptoms, as 

well as [emergency department] visits and hospitalizations for all respiratory causes and 

asthma.” 74 Fed. Reg. at 64818/2-3. Although the Proposed Rule acknowledges 

uncertainties with respect to the epidemiologic studies, it fails to account fully for the 

nature and magnitude of uncertainty that surrounds the epidemiologic research. This 

failure has persisted throughout the current review of the SO2 NAAQS. As a result, 

although the epidemiologic research cites health effects, such as HA and ED visits, that 

are unquestionably adverse, there is no clear indication that these effects are the result 

of SO2 exposure. In fact, there is evidence to suggest that they are not. 

The epidemiologic studies cited in the Proposed Rule are inconsistent with the 

results of clinical studies. The Proposed Rule states that “[e]pidemiologic studies 

provide evidence of associations between SO2 concentrations and more serious health 

endpoints (e.g., [HAs] and [ED visits]) that cannot be assessed in controlled human 

exposure studies.” Id. at 64815/3. This statement is curious. Although no one would 

suggest that clinical studies could or should be conducted with the intent of sending 

people to the hospital, there is also no indication from the clinical studies of any 

population that would be susceptible to SO2 such that a brief exposure to a low 

concentration could lead to hospital visits. As discussed above, research indicates that 

responsiveness to SO2 in asthmatics is not dependant on the severity of the asthma. 

See discussion of Linn et al. (1987) supra at p. 13-14. Additionally, clinical studies 
17

conducted at SO2 concentrations far above ambient levels17 report only effects in 

asthmatics that are transient and reversible and that dissipate rapidly. See supra at p. 

7. EPA recognizes that human clinical studies “provide directly applicable information 

for determining causality” while for epidemiological studies “the degree of uncertainty 

introduced by confounding variables (e.g., other pollutants) affects the level of 

confidence that the health effects being investigated are attributable to SO2 exposures.” 

74 Fed. Reg. at 64815/3 - 64816/1. Thus, the discrepancy between the nature of 

effects attributed to SO2 in epidemiologic studies at ambient levels and those in clinical 

studies at much higher SO2 concentrations must call into question the reliability of the 

epidemiological studies as evidence of effects from SO2 exposure. 

Although EPA acknowledges that confounding is an issue in epidemiologic 

research, the Agency fails to account for it appropriately. As epidemiologic studies are 

observational in nature, confounding by co-pollutants and other environmental factors 

can never be ruled out, but researchers can evaluate the possibility of confounding 

through the use of co-pollutant models. However, many of the epidemiologic studies 

that EPA relied on for the conclusions drawn in the ISA and that the Administrator cites 

as “key studies” in the Proposed Rule fail to account for confounding. For example, of 

the five epidemiologic studies cited in the Proposed Rule that studied respiratory 

symptoms, none appropriately accounted for confounding. The Proposed Rule states 

that the results of Mortimer et al. (2002) and Schildcrout et al. (2006) “remained robust 

and statistically significant” in co-pollutant models. Id. at 64818/2, 3. However, both of 

 17 Clinical studies show pronounced, though transient, effects following exposure 

to SO2 concentrations beginning at 0.6 - 1.0 ppm (600 - 1000 ppb). 61 Fed. Reg. at 

(continued on next page) 
18

these studies used regional monitoring as a surrogate for exposure, which leads to 

measurement errors in the estimate of SO2 exposure, but also in exposure estimates for 

all of the other potentially confounding co-pollutants.18 When all of the co-pollutants are 

measured with error, robustness of the association of one pollutant in multi-pollutant 

models is not sufficient to infer an absence of confounding. Schwartz et al. (1994) 

found that there was a possibility of confounding by PM10. See id. at 8; 74 Fed. Reg. at 

64818/3. Neither of the other two studies included multi-pollutant models. 74 Fed. Reg. 

at 64818/3. Likewise, only three of the ten “key studies” on HAs and ED visits included 

multi-pollutant models, and multi-pollutant models in those three studies reported mixed 

results. See id. at 64819/2-3. It is particularly inappropriate to rely on such studies 

when, as here, EPA has previously concluded that the very effects investigated in the 

studies are caused by co-pollutants.19 

Another issue with the treatment of epidemiologic research in the Proposed Rule 

is the lack of statistical significance in many of the studies cited. Although the 

Administrator notes the importance of the strength of statistical associations in 

 

25571/3. 

18 See J. Turim, Ph.D., C. Frankenfeld, Ph.D., S. Moolgavkar, M.D., Ph.D., 

Comments on EPA’s Integrated Science Assessment for Sulfur Oxides-Health Criteria 

(Second External Review Draft) (July 25, 2008) at 7-8, attached as Enclosure 1 to 

Second Draft ISA Comments (“Turim 2007”). 

19 Each of the Agency’s 2006 PM2.5 NAAQS, 2008 ozone NAAQS, and 2010 NO2

NAAQS are based, at least in part, on epidemiologic evidence associating each of those 

pollutants with HAs and ED visits for respiratory causes. See National Ambient Air 

Quality Standards for Particulate Matter; Final Rule, 71 Fed. Reg. 61143, 61145/1 (Oct. 

17, 2006); National Ambient Air Quality Standards for Ozone; Final Rule, 73 Fed. Reg. 

16436, 16436/3 (Mar. 27, 2008); Primary National Ambient Air Quality Standards for 

Nitrogen Dioxide: Final Rule (Jan. 22, 2010), at 24. 
19

epidemiologic studies, 74 Fed. Reg. 64816/1, she relies heavily on studies where there 

is no statistically significant association. See, e.g., id. at 64819/1 (“Taken together, [the 

ten “key” epidemiologic studies on HAs and ED visits] generally reported positive, but 

frequently not statistically significant associations between ambient SO2 and ED visits 

and [HAs] for all respiratory causes and for asthma.” (emphasis added)). This lack of 

statistical significance indicates a likelihood that the positive results of these studies are 

inaccurate, and they may well be indicating no effect at all. 

Finally, EPA has failed to address recent studies relevant to the health effects of 

SO2 exposure, even after UARG called them to the Agency’s attention over two years 

ago in its comments on the first draft of the ISA.20 These studies, which EPA has failed 

to account for in this NAAQS review, reported results that counter the Agency’s 

conclusions regarding the health effects of SO2 exposure. For example, Donoghue and 

Thomas reported “no evidence of any positive relation between peak SO2

concentrations [ranging from 0 to 8700 μg/m3] and hospital presentations or admissions 

for asthma, wheeze or shortness of breath.” Donoghue et al. (1999) at 232. Erbas and 

Hyndman examined the sensitivity of associations between air pollution and HAs and 

reported that “the effects of . . . sulfur dioxide were highly sensitive to model 

specification for both COPD and asthma [HAs].” See Turim 2007 at 10. 

 20 See First Draft ISA Comments at 10 n.28 (noting that neither Erbas, B & 

Hyndman, RJ (2005) Sensitivity of the estimated air pollution-respiratory admissions 

relationship to statistical model choice. Int. J. Environ. Health Res. 15:437-48 nor 

Donoghue, AM & Thomas M (1999) Point source sulphur dioxide peaks and hospital 

presentations for asthma. 56 Occup. Environ. Med. 56:232-36 is discussed in the ISA). 

Neither study was mentioned in subsequent drafts of the ISA or the REA, and neither is 

mentioned in the Proposed Rule. 
20

EPA is required to consider all of the “latest scientific knowledge” relevant to the 

effects of SO2 exposure on human health. CAA § 108(a)(2). It is just as important that 

EPA consider scientific research such as this, that indicates that there is no effect, as it 

is that the Agency consider research that indicates an effect -- the Agency must 

examine the entire range of outcomes in order to formulate a judgment that reflects the 

latest scientific knowledge. The fact that EPA has failed to examine, or even 

acknowledge the existence of these studies after they were pointed out in public 

comments, is a striking indication that EPA has not fulfilled its duty under the CAA. 

II. Information on Both Exposure and Risk Demonstrates No Need for the 

Proposed 1-hour SO2 NAAQS. 

As discussed above, the Administrator is required to set primary SO2 NAAQS at 

a level that in her judgment is “requisite to protect the public health” while “allowing an 

adequate margin of safety.” CAA § 109(b)(1). In determining what level is requisite, 

she must base her judgment on air quality criteria that “adequately reflect the latest 

scientific knowledge useful in indicating the kind and extent of all identifiable effects on 

human health . . . which may be expected from the presence of such pollutant in the 

ambient air in varying quantities.” CAA § 108(a)(2) (emphasis added). In other words, 

the Administrator must set the NAAQS at a level that is necessary to protect public 

health from risks presented by exposure to SO2 in the ambient air, at levels that exist at 

the time of the review or that are expected to exist in the future. In doing so, she may 

not set the NAAQS at a level that is more stringent than necessary to protect public 

health with an adequate margin of safety. See Whitman, 531 U.S. at 473, 476 (2001). 

According to information provided by EPA, there is no unacceptable risk to public 

health posed by current ambient levels of SO2 and none is expected in the future. In 
21

effect, the Proposed Rule seeks to fix a problem that does not exist. EPA has 

acknowledged repeatedly that SO2 concentrations in the United States have been 

decreasing over the past several decades and that it expects this trend to continue. 

EPA reported in December 2009 that, as of 2008, annual SO2 emissions had decreased 

by 56% compared with 1980 levels and 52% compared with 1990 levels. EPA, Acid 

Rain and Related Programs: 2008 Highlights, 2 (Dec. 2009). Additionally, the national 

composite average of the annual mean ambient concentration of SO2 decreased by 

71% between 1980 and 2008.21 Id. at 5. In EPA’s most recent National Air Quality 

Status and Trends Report, the Agency cited a downward trend in ambient SO2

concentrations. EPA, National Air Quality Status and Trends Through 2007, 27 (Nov. 

2008). The Agency attributed this trend to various national emissions control programs, 

including the NAAQS, and stated that it expects air quality to continue to improve in the 

coming years. Id. at 3, 27. Accordingly, any existing health risks from SO2 exposure 

will be expected to decline in the future. 

Significantly, however, EPA has not identified any health risks from exposure to 

current ambient concentrations of SO2. Although the REA and the Proposed Rule 

include some information on risks at current ambient levels of SO2, both the REA and 

the Proposed Rule focus on risks that would exist if air quality were adjusted to just 

meet the current NAAQS (either the 24-hour standard or the annual standard, 

whichever is controlling for a particular area) and to just meet potential alternative onehour daily maximum standards of 50, 100, 150, 200 and 250 ppb respectively. 

 21 EPA specifically noted that the decline in SO2 emissions from the power 

industry has improved air quality. Id.
22

Throughout this NAAQS review process, UARG has commented repeatedly that 

EPA should base its analyses on the effects of current air quality and not air quality 

modeled to just meet the current standard or alternative standards.22 There are a 

number of serious issues with EPA’s use of modeled air quality. First, as described 

above, the Administrator, in reviewing and revising the NAAQS, is required to consider 

risks to public health associated with air quality under current conditions or conditions 

that are expected to exist in the future. EPA has been quite clear that current air quality 

has improved dramatically over the past several decades and that it is expected to 

continue to improve in the future. See discussion supra at p. 20-21. It is far better than 

needed to meet the current NAAQS in all but three areas in the continental United 

States.23 Thus, ambient SO2 concentrations are not expected to increase to just meet 

the current standard in the future, and setting aside the fact that EPA has stated that it 

expects SO2 concentrations to continue decreasing, EPA has not identified any event or 

condition that could lead to a deterioration of air quality that would cause ambient SO2

concentrations to reach the current NAAQS. 

Although they are not reported in the Proposed Rule and apparently were not 

considered in the preparation thereof, the REA contains some data that address risk at 

current air quality. EPA has stated that the purpose of the proposed 1-hour standard is 

to protect against 5-minute SO2 concentrations above 200 to 400 ppb. 74 Fed. Reg. at 

 22 See First Draft REA Comments at 3-9; Second Draft REA Comments at 4-9. 

23 See, EPA’s Green Book nonattainment areas for sulfur dioxide (primary 

standard), available at http://www.epa.gov/oar/oaqps/greenbk/snc.html (listing 

Armstrong County, PA, Hayden (Pinal County), AZ and Laurel Area (Yellowstone 

County), MT as nonattainment area for the primary SO2 NAAQS. 
23

64842/3; REA at 392. Thus, this is the level of risk that the Administrator has 

determined to be acceptable.24 However, EPA’s evaluation of data from 809 ambient 

SO2 monitors, given the annual average SO2 concentration between 1997-2006, 

reported that only approximately 1% of days included a 5-minute SO2 concentration of 

200 ppb, and less than 1% of days included a 5-minute SO2 concentration of 300 or 400 

ppb. REA at 127-28. Thus, 5-minute SO2 concentrations in the range of interest are 

very rare, and health effects can only be related to such infrequent SO2 levels if 

susceptible people (in this case, sensitive exercising asthmatics) are exposed to such 

levels. Additionally, as air quality is improving, 5-minute SO2 concentrations in this 

range are likely to be even lower today. 

EPA’s REA included risk and exposure analysis case studies of asthmatics -- the 

subpopulation that EPA has identified as susceptible -- in St. Louis and in Greene 

County, Missouri. The Agency examined specifically the number of asthmatics living 

within 20 kilometers of a major SO2 source experiencing 5-minute SO2 exposures to 

100, 200, 300 and 400 ppb while at elevated breathing rates, and modeled air quality to 

represent attainment of each of the targeted levels. Id. at 10. EPA reported that the 

exposure results for Greene County using “as is” air quality were similar to those for air 

quality adjusted to meet the proposed 99th percentile 1-hour daily maximum standards 

of 50 and 100 ppb, with few people being exposed, and that the results for St. Louis 

indicated that exposure results for “as is” air quality were within the range of exposures 

using the proposed 50 and 100 ppb standards. Id. at 312. 

 24 The NAAQS is not intended to eliminate all risk. See discussion supra at p. 4-

5. 
24

EPA’s risk modeling indicates that the risks associated with current ambient air 

quality are consistently comparable to or lower than the risks that are estimated to exist 

upon attainment of any of the 1-hour SO2 standards under consideration. For example, 

Table 9-8 of the REA presents EPA’s data on the percentages of asthmatic children 

engaged in moderate or greater exertion that are estimated to experience at least one 

lung function response per year associated with exposure to SO2 concentrations at 

various levels in each of St. Louis and Greene County, Missouri. See id. at 338. Table 

9-8 of the REA is reproduced below: 

As indicated in Table 9-8, EPA’s St. Louis analysis reported that, using the 2-

parameter logistic model, the percentage of asthmatic children engaged in moderate or 

greater exercise who are estimated to experience an increase in specific airway 

resistance (sRAW) of 100% or greater at least once in a year from exposure to current 

ambient air is 1.4%, which is lower than the percentage of children estimated to 
25

experience such a response upon exposure to air that meets a 99th percentile daily 

maximum 1-hour standard of either 100 ppb (2.9%) or 150 ppb (5.4%). Although the 

percentage estimated to experience such a response upon exposure to air that meets 

the 50 ppb standard appears slightly lower (0.9%), it is indistinguishable from the 

percentage responding to current air quality, as it falls within the 95% credible interval 

(0.5% - 3.8%). The same is true using the probit model, with 0.8% estimated to 

respond following exposure to current air quality, compared to 2.1% and 4.6% 

estimated to respond following exposure to air meeting either of the proposed 100 or 

150 ppb standards respectively, and 0.4% estimated to respond following exposure at 

the proposed 50 ppb level (which is within the 95% credible interval of 0.2% - 2.8%). 

Similarly, the Greene County analysis reported that, using either the 2-parameter 

logistic model25 or the probit model,26 the percentage of asthmatic children predicted to 

experience an increase in sRAW of 100% or greater at least once in a year is identical 

for current air quality, and for air quality that attains a 99th percentile daily maximum 1-

hour standard of 50 ppb, and lower with current air quality than with a 99th percentile 

daily maximum standard of 100 ppb, or 150 ppb. Indeed, EPA’s modeling indicates that 

the comparability among the levels of residual risk permitted by current air quality and 

 25 According to EPA, in Greene County, 0.4% of exercising asthmatic children 

would be expected to experience at least one lung function response associated with 

SO2 per year following exposure to current air quality and following exposure to air 

meeting the 50 or the 100 ppb standard, and 0.5% would be expected to experience 

such a reaction upon exposure to air meeting the 150 ppb standard. 

26 According to EPA, in Greene County, 0.1% of exercising asthmatic children 

would be expected to experience at least one lung function response associated with 

SO2 per year following exposure to current air quality or air meeting the proposed 99th

percentile daily maximum 1-hour standard of either 50 or 100 ppb, and 0.2% would be 

expected to respond to air meeting the 150 ppb standard. 
26

by the proposed 1-hour standards of 50, 100 and 150 ppb holds true for EPA’s 

estimates of the number27 and percent28 of asthmatics engaged in moderate or greater 

exertion estimated to experience an increase in sRAW of 100% or greater at least once 

in a year; the number of occurrences of such an increase in sRAW among asthmatics;29

the number of asthmatic children estimated to experience such an increase in sRAW;30

and the number of occurrences of such an increase in sRAW among asthmatic 

children.31 The same is also true of EPA’s estimates of decreases in FEV1 of 15% and 

20% following exposure to current air quality and air adjusted to meet the proposed 1-

hour standards of 50, 100 and 150 ppb, which appear in Appendix C.32

 27 See id. at 334, Table 9-4. 

28 See id. at 335, Table 9-5. 

29 See id. at 336, Table 9-6. 

30 See id. at 337, Table 9-7. 

31 See id. at 339, Table 9-9. 

32 See REA Appendix C at 4-18, Table 4-3 (number of occurrences in a year 

among asthmatics engaged in moderate or greater exertion); 4-19, Table 4-4 number of 

occurrences in a year among asthmatic children engaged in moderate or greater 

exertion); 4-22, Table 4-7 (number of asthmatics engaged in moderate or greater 

exertion estimated to experience one such response in year); 4-23, Table 4-8 (number 

of asthmatic children engaged in moderate or greater exertion estimated to experience 

one such response in year); 4-26, Table 4-11 (percent of asthmatics engaged in 

moderate or greater exertion estimated to experience one such response in year); and 

4-27, Table 4-12 (percent of asthmatics engaged in moderate or greater exertion 

estimated to experience one such response in year). In each case, the number or 

percentage estimated for current air quality is indistinguishable from or lower than the 

number or percentage estimated for air quality adjusted to meet the proposed 1-hour 

standards of 50, 100 and 150 ppb (or the number or percentage for the proposed 

standard is within the 95% credible interval for the estimate at current air quality). 
27

Moreover, EPA overestimates the risk to the health of asthmatics and asthmatic 

children associated with current air quality and attainment of any of the alternative 

standards as a result of the techniques used in the analysis.33 In addition, the Agency’s 

analysis fails to reflect that only repeated exposures or lung function changes should be 

deemed to be of public health significance. 

It is important to note that, although the REA is not a comprehensive examination 

of risk nationally, it examined risks in areas where SO2 emissions were among the 

highest currently found in the U.S. REA at 189 (“In a ranking of estimated SO2 

emissions reported in the National Emissions Inventory . . . Missouri ranked 7th out of all 

U.S. states for the number of stacks with annual emissions greater than 1,000 tons.”). 

Additionally, the estimates of current air quality are actually based on air quality 

information from 2002. Id. at 332. Thus, these numbers are not representative of the 

United States now that SO2 levels have fallen and likely overstate current risks. Even 

within this limited Missouri data set, EPA consistently emphasizes the results of the St. 

Louis analysis and disregards the results of the analysis in rural Greene County.34 This 

 33 See Memorandum from Edmund Crouch, Ph.D., to Utility Air Regulatory 

Group, Response to EPA-HQ-ORD-2006-0260-0036 3-4 (Feb. 5, 2010) (Attached 

hereto as Attachment C) (explaining that EPA has failed to respond in any meaningful 

way to his technical comments on the draft REA on behalf of UARG, detailing 

substantial technical errors that led to significant overprediction of risk, and that EPA 

has failed to account properly for such overprediction of risk). 

34 See, e.g., 74 Fed. Reg. at 64827/2 (“when considering the risk and exposure 

results as they relate to the adequacy of the current standards, the REA concluded that 

the St. Louis results were more informative [than the Greene County results] in terms of 

ascertaining the extent to which the current standards protect against effects linked to 

various benchmarks”); Id. at 64842/3 to 43/1 (basing determination of the level of the 

proposed 1-hour standard on the St. Louis risk and exposure analyses but not 

mentioning the Greene County analyses). 
28

is inappropriate. As indicated in the REA,35 Greene County is a reasonable model for 

exposures in rural areas. 

In summary, as described above, in the REA and the Proposed Rule, EPA has 

vastly overestimated the public health risk presented by SO2 concentrations. In fact, 

risks are below those identified by EPA as dangerous, or unacceptable, and will 

continue to decrease as air quality continues to improve. Therefore, there is no 

justification for the proposed 1-hour NAAQS.36 

III. The Agency Must Base Nonattainment Decisions on Monitors Qualifying as 

Federal Reference Method Monitors Under The Agency’s New 

Specifications. 

In the Proposed Rule, the Administrator proposes to establish a new Federal 

Reference Method (“FRM”) for measuring ambient levels of SO2, 74 Fed. Reg. 64846/1, 

and to update the performance based requirements for Federal Equivalent Method 

(“FEM”) analyzers. Id. at 64847/1. She proposes further to retain the current FRM for a 

period of time after the final rule (including the new FRM) is promulgated in order to 

 35 See, e.g., REA at 311 (noting that the St. Louis and Greene County exposure 

analyses “[t]aken together . . . provide useful insights about urban and rural counties 

with SO2 emission sources”). 

36 The health evidence at most suggests that exercising asthmatics should be 

protected from brief exposures to 600 ppb. Assuming that the ratio between a 5-minute 

peak and a 1-hour average is in the range of 2 or 3 to 1, an hourly standard in the range 

of 200 to 300 ppb would appear protective. Any such standard should use the 98th

percentile form given that only multiple responses by an asthmatic to SO2 might 

legitimately be considered of public health significance. Moreover, the 98th percentile 

form would be consistent with the form used for the Agency’s recently promulgated 1-

hour primary NAAQS for NO2 and the Agency’s 24-hour primary NAAQS for PM2.5. No 

such standard is requisite to protect public health, however, because SO2 levels 

currently found in ambient air are already protective against such effects. 
29

avoid disruption of the SO2 monitoring network. Id. at 64848/1-2. While UARG agrees 

that a new FRM for judging compliance with a new 1-hour SO2 NAAQS is appropriate, 

the proposed approach for implementing it is contrary to the terms of the CAA, and 

therefore must be abandoned. 

The Proposed Rule acknowledges that any data to be used in determining 

compliance with the SO2 NAAQS must be collected using either an FRM or an FEM. Id.

at 64846/1. One primary purpose of FRMs is “to provide a specified, definitive 

methodology for routinely measuring concentrations of various ambient air pollutants for 

comparison to the NAAQS. Id. at 64846/2. An FRM is designated is to ensure 

consistency and fairness when judging compliance with a NAAQS. Thus, EPA 

designates a single FRM for judging compliance with each NAAQS.37 Therefore, if the 

Administrator promulgates a new 1-hour NAAQS for SO2, she must specify a single 

FRM for that standard, and only data collected using that FRM (or monitors designated 

as an FEM with regard to the FRM) can be used to assess compliance with that 

NAAQS.38 

 37 See 40 C.F.R. App. A (specifying a single FRM for the SO2 NAAQS codified in 

40 C.F.R. 50.4 & 50.5), App. C (describing a single measurement principle and 

calibration procedure defining an FRM for the carbon monoxide NAAQS codified in 40 

C.F.R. 50.8), App. D (describing a single measurement principle and calibration 

procedure defining an FRM for the ozone NAAQS codified at 40 C.F.R. 50.9, 50.10 & 

50.15), App. G (specifying a single FRM for the lead NAAQS codified at 40 C.F.R. 50.12 

& 50.16) and App. L (specifying a single FRM for the PM2.5 NAAQS codified at 40 

C.F.R. 50.7 & 50.13). 

38 EPA would have the option of retaining the existing FRM for judging 

compliance with the 3-hour, 24, hour and annual NAAQS to the extent that any or all of 

those standards are retained. Certainly, EPA has designated different FRMs for 

measuring different regulated forms of particulate matter. It might be less burdensome 

for the States, however, for EPA to designate a single FRM for all of the SO2 NAAQS. 
30

With regard to EPA’s decision to use a different FRM to judge compliance with 

any new SO2 NAAQS, UARG agrees that that is appropriate. The ability of this monitor 

to accurately measure low hourly concentrations of SO2 has not, to UARG’s knowledge, 

ever been demonstrated. In fact, as the Proposed Rule explains: 

The existing FRM is primarily a 24-hour integrated method, 

whereas a 1-hour SO2 FRM measurement capability would 

be needed to implement the proposed 1-hour SO2 NAAQS. . 

. . While the existing manual reference method can produce 

1-hour averages, it is clearly impractical for routine use in 

making 1-hour SO2 measurements. Also, the 1-hour mode 

of the manual methods is not a good standard for approving 

new FEMs with 1-hour measurement capability, because 

scores of 1-hour measurements would be needed during 

equivalency testing. 

74 Fed. Reg. at 64846/3. 

The proposal to specify a different FRM to judge compliance is therefore entirely 

reasonable. UARG is generally supportive of the proposed specifications for a new 

FRM. We question, however, the Agency’s proposed total interferent limit. EPA 

proposed to reduce the allowable interference equivalent limits for the total of all 

interferents from 60 ppb to 20 ppb. Id. at 64848/3. Although this is a substantial 

reduction, even 20 ppb is a significant percentage of any of the 1-hour NAAQS that EPA 

proposes.39 UARG therefore recommends that the Agency further limit the total of all 

interferents.40 

 39 The Administrator’s proposed total interferent limit of 20 ppb amounts to 20-

40% of the proposed NAAQS (50-150 ppb). Eric S. Edgerton, Comments on Proposed 

SO2 Rule 1 (Feb. 3, 2010) (Attached hereto as Attachment D). 

40 See id. (demonstrating that the Administrator’s proposed total interferent limit 

is likely to lead to false positive exceedances of the proposed NAAQS). 
31

As EPA recognizes, specification of a new FRM has implications for existing SO2

monitoring networks. See 74 Fed. Reg. at 64848/3. For the reasons discussed above, 

however, EPA’s proposal to retain the existing FRM for several years -- thus having two 

FRMs specified for a given NAAQS -- is not viable. See id. at 64848/2. Although EPA 

states that the existing FEMs that constitute the bulk of the SO2 monitoring network “are 

adequate for the current and the proposed SO2 NAAQS,” Id. at 64848/1, the Agency 

has provided no support for this statement. Although they may be adequate “for many 

other purposes,” Id. at 64848/1-2, they may only to used to judge compliance with the 1-

hour NAAQS if they are shown to qualify as FRMs or FEMS under the new FRM 

definition. 

EPA therefore would have two options for making initial designations with regard 

to any 1-hour NAAQS that it adopts. First, it could designate all areas as unclassifiable 

until adequate data have been collected using the new FRM. Second, if the Agency 

believes that many of the monitors in the existing networks might qualify as new FRMs 

or FEMs, the Agency could take advantage of its authority to extend the deadline for 

designations by a year, see CAA § 107(d)(1)(B),41 and use that year to determine which 

monitors would qualify under the new FRM and FEM definitions. For those monitors 

that qualify, EPA could then appropriately rely on existing data to make designations. 

 41 EPA recently used this provision to defer designations for the 2008 ozone 

NAAQS by a year while it reconsiders that rule. 75 Fed. Reg. 2936 (Jan. 19, 2010). 

Extending the date for designations in light of the lack of data from monitors then 

qualified as FRMs or FEMs would be at least as appropriate as that use of the 

provision. 
32

IV. Other Implementation Concerns 

A. Monitoring Network Design 

EPA proposes to revise the design of the monitoring network for SO2 to reflect 

two components: (1) a requirement for monitoring tied to an EPA-developed populationweighted emissions index based on populations and the emissions inventory of a 

CBSA, and (2) monitoring tied to total state-level SO2 emissions. See 74 Fed. Reg. at 

64851/2 to 53/3. UARG’s primary concern with this network design is its reliance on old 

emissions data. For electric utilities which report their SO2 emissions to EPA annually, 

the use of more recent data would be appropriate. 

UARG believes that it is appropriate to tie the monitoring network for a standard 

intended to protect public health to the size of the population in an area, as opposed to 

the alternative approach to network design on which EPA is soliciting comments. That 

approach would appear to focus solely on monitoring near SO2 sources. See id. at 

64854/3. Moreover, that approach would be laborious. It would rely on highly 

conservative screening models for selecting which sources might require a monitor, and 

would then require further modeling with AERMOD to site monitors. EPA recognizes 

that AERMOD will likely require adjustments before it would be suitable for use with a 

new 1-hour SO2 standard. Id. at 64862/1. More basically, however, AERMOD would 

simply not be appropriate for siting a monitor at the likely site of the expected maximum 

1-hour concentration -- the model has been validated by comparing it with observed 

high ambient concentrations, but its performance for matching concentrations at a 

specific time or location has not been evaluated. 
33

B. Data Interpretation 

The Proposed Rule also contains provisions to ensure data completeness. See

Id. 64856/2-3. These provisions suggest that at least 75% of the monitoring data that 

should have resulted from monitoring in accordance with the schedule during a calendar 

quarter must be available. Id. 64856/2. If it is not, but 50% percent of the expected 

data is available, the Administrator’s plan “would substitute a high hypothetical 

concentration for as much of the missing data as needed to meet the 100% 

requirement.” Id. at 64856/3. The concentrations that would be substituted would be 

the highest daily maximum 1-hour concentration observed during the same calendar 

quarter. Id. 64856/3. Finally, the Proposed Rule would give the Administrator “general 

discretion to use incomplete data,” either at the request of a state or on her own. Id. at 

64856/3. 

UARG agrees that there should be completeness criteria for compliance data. 

However, there are several flaws with the Administrator’s approach. First, giving the 

Administrator authority to use incomplete data despite the rule on data completeness 

renders the rule meaningless and opens the possibility of arbitrary decisions, or 

decisions that appear arbitrary. The rule should include a system for determining the 

circumstances under which incomplete data should be used, rather than giving 

unfettered discretion to the Administrator. Second, substituting the highest reported 

concentrations for missing data will lead to data sets that are not representative of 

actual conditions. If the rule provides for substitution of hypothetical data, those data 

should be set at values that would have been likely to be recorded and not at extreme 

values. Third, given that only 75% of the expected data are required for completeness, 

if hypothetical data are substituted, only enough to make up 75% of the expected data 
34

should be substituted, as opposed to 100%. The goal of the monitoring program should 

be to obtain an accurate measurement of ambient SO2 levels and the measurement will 

be more accurate, not only the higher the percentage of expected data points are used, 

but also the higher the percentage of such data points that represent actual monitored 

data. 

C. Exceptional Events 

The Proposed Rule provides further that, with respect to exceptional events, to 

the extent 2011 data is considered for SO2 designations, “2011 data must be flagged 

and detailed event documentation submitted 60 days after the end of a calendar quarter 

in which the event occurred or by March 31, 2011.” Id. 64858/1-2. This proposal 

seems so odd that UARG suspects that it may be an error. According to Table 6 of the 

Proposed Rule, the detailed documentation submission deadline for 2011 occurs after 

the deadline for 2010 documentation. See Table 6, 74 Fed. Reg. at 64858 (listing the 

deadline for 2010 as June 1, 2011 and the deadline for 2011 as the earlier of (i) 60 days 

after the end of the calendar quarter in which the event occurred and (ii) March 31, 

2011). March 31, 2011 is the end of the first calendar quarter of 2011 and will always 

occur before 60 days after any calendar quarter for 2011. Therefore, the 

Administrator’s framework for determining the 2011 deadline is at best arbitrary and at 

worst nonsensical. Finally, this deadline will not allow for consideration of a full year of 

data for 2011, something that would be required if any 2011 data were to be 

considered. See 74 Fed. Reg. at 64873/1 (defining a year as a calendar year). 

UARG suggests that the deadline for detailed 2011 documentation submission 

should be March 31, 2012, or in the alternative, 60 days after the end of each calendar 
35

quarter. The deadline should be March 31, 2013 if necessary to qualify FRMs and 

FEMs under new specifications. 

D. Issues Requiring Further Rulemaking 

The Proposed Rule suggests development of new screening tools, such as 

significant impact levels (“SILs”), significant emissions rates (“SERs”) and significant 

monitoring concentrations (“SMCs”), to accompany the proposed 1-hour standard. Id.

64862/2-3. It also suggests that it may consider new PSD increments. Id. at 64861/1.42 

Furthermore, it suggests the need for anti-backsliding provisions if either the annual or 

24-hour NAAQS is repealed. Id. at 64863/3. The Proposed Rule does not provide 

sufficient details to provide for meaningful public comment on these issues. As a result, 

the Proposed Rule does not provide adequate notice of the Administrator’s plans for 

these regulations. Thus, if the Administrator intends to specify new requirements in 

these areas, she must conduct separate notice-and-comment rulemaking before doing 

so, allowing adequate opportunity for interested parties to develop and provide 

thoughtful comments. 

V. Conclusion 

In summary, the scientific record and EPA’s own modeling of the risks associated 

with ambient SO2 do not justify the Agency’s proposed 1-hour primary SO2 NAAQS. 

 42 Ideally, EPA would provide the regulatory framework for a PSD program at the 

time that it promulgates a new NAAQS. Clearly, that is not possible in this case. 

Promulgating a NAAQS without the framework to implement it -- whether that 

framework is a PSD program or models that can be used to provide realistic estimates 

of ambient air quality for purposes of SIP development -- imposes a significant burden 

on States and source owners. The problems associated with an inadequately 

developed implementation program are exacerbated in this case, where States have 

only 18 months after a nonattainment designation to submit an approved SIP to EPA. 

See CAA § 191(a). 
36

Nor do they establish a basis for a 1-hour NAAQS of 150 ppb. Indeed, given the low 

risk of short-term health effects posed by SO2 in current ambient air, the record simply 

does not show that revision of the primary SO2 NAAQS through promulgation of any 1-

hour NAAQS is appropriate. If, contrary to UARG’s recommendations, EPA 

nevertheless promulgates a 1-hour SO2 NAAQS, the Agency should revise its 

implementation program for that standard as explained in these comments.
1

Attachment A

Timothy H. Savage, Ph.D., Comments on Risk and Exposure Assessment to Support 

the Review of the SO2 Primary National Ambient Air Quality Standards: First Draft 

(Presentation on behalf of UARG to CASAC meeting of Dec. 5-6, 2007)
Comments on Risk and Exposure Assessm

Support the Review of the SO

2 Primary Na

Ambient Air Quality Standards: Firs

Dr. Timothy H

Prepared on behalf o
2

Three Issues in Five Minutes• Decline in the Number of Monitors• Prediction of 5-Minute Max Exceedances• Roll-Up to “Just-Meet” Standards
3

Decline in Number of Monitors• Draft REA documents large decline in the number 

minute max and 1-hour average SO2 monitors.
4

Figure 6-11: Decline in 5-Min Max Monitors
5

Figure 6-17: Decline in 1-Hour Average Monitors
6

Assessing the Effect• EPA should explore the temporal and geographic 

in which monitors have been removed. 

• In particular, EPA should focus on whether non-ra

monitor closure could be introducing systematic bprediction of exceedances.
7

Prediction Using Peak-to-Mean Ratio (PMR)• EPA employs a PMR to predict 5-minute max conc

from 1-hour average concentrations.

• EPA’s current PMR is based on COV.• COV is useful for summarizing dispersion of data.• It is less appropriate as a predictive method in this 

– Traditional standard deviation of normally distributed dat
8

Evidence of Over-Prediction for 400 PPB Level
9

Predicting Exceedances• EPA should recognize that it is predicting exceeda

which is a “rare” event.

• EPA should consider using more standard parame

models for prediction.

– Logistic, exponential, and/or log-normal.

• EPA should document the quality of any prediction 

using actual 5-minute max concentrations as a ben

• EPA should develop confidence intervals for any p

method to assess the relevance of sampling variab
10

Roll-Up Approach Stretches the Bounds of Real• Following the NO2 REA, EPA conducts a roll-up of 

is” standard to a “just-meets” standard.

• EPA’s roll-up factors used in the draft SO2 REA are 

larger than those used in the NO2 REA.

– Median factor is 3.75.– Top 25% of factors range from 4.47 to 15.85. 

• Process lacks scientific credibility as it requires an 

unwarranted degree of extrapolation from observe

• Statistically, it is unclear whether an entire distribu

be credibly “rolled up” in such a manner.
11

Timothy H

CRA Inter

1155 Avenue of the A

New York, N

(212) 5

tsavage@
1

Attachment B

J. Turim, Ph.D., S. Moolgavkar, M.D., Ph.D., E. Anderson, Ph.D., A.T.S.F., Comments 

on EPA’s Integrated Science Assessment for Sulfur Oxides -- Health Criteria: Summary 

(Dec. 3, 2007) (written presentation to CASAC meeting of Dec. 5-6, 2007) 
COMMENTS ON EPA’S INTEGRATED SCIENCE ASSESSMENT 

FOR SULFUR OXIDES-HEALTH CRITERIA

SUMMARY

J. Turim, PhD

S. Moolgavkar, MD, PhD

E.L. Anderson, PhD, ATSF 

Exponent, Inc.

December 3, 2007
2

COMMENTS ON EPA’S INTEGRATED SCIENCE ASSESSMENT FOR 

SULFUR OXIDES-HEALTH CRITERIA

SUMMARY

This is the summary of a report prepared by Exponent, Inc. commenting on EPA’s 

Integrated Science Assessment for Sulfur Oxides – Health Criteria (First External Review 

Draft) September 2007 (ISA). The full text was filed with comments of the Utility Air 

Regulatory Group to EPA on November 30, 2007. The report focused on Chapters 3 and 

4 of the ISA that summarized the clinical (chamber) and epidemiological studies of sulfur 

oxides and the ISA interpretation of the totality of the literature. The emphasis of the 

report was on new human studies that may have significant impact on the EPA 

Administrator’s decision on whether to revise the primary SO2 NAAQS. 

The ISA states “there is a causal relationship between peak (1 h or less, typically 5 to 15 

min) exposure to SO2 and effects on the respiratory system, based on evidence from 

human clinical studies. Human clinical studies provide clear and consistent evidence of a 

causal relationship between peak exposures to SO2 at levels of 0.5 to 1.0 ppm and effects 

on the respiratory system, namely decrements in lung function in exercising asthmatic 

adults.”

Five papers published in 1990 or later reporting on four clinical studies are included in 

ISA Table 5A-2 that provides results on key human health effects of peak exposure to 

SO2 (Magnussen et al (1990), Gong et al (1995), Tunnicliffe et al (2001, 2003), and 

Routledge et al (2007)). Of the five publications, only two consider exposures in the 

range of 0.5 to 1.0 ppm, and their results provide little additional support for the ISA’s 

conclusion of a causal relationship between peak exposure and respiratory system effects

in exercising asthmatics. Magnussen et al. (1990) simply confirmed previous findings 

that asthmatics are more sensitive than non-asthmatics to SO2 concentrations of 500 ppb. 
3

Gong et al. (1995) found a decrease in FEV1 and an increase in SRaw with increasing 

SO2 exposure. Contrary to what would be expected, these trends did not increase with an 

increasing level of exercise. Of the remaining three papers, the Tunnicliffe et al. (2001) 

and Routledge et al. (2007) studies offer, as described in the ISA, ‘weak and inconsistent 

evidence’ of changes in heart rate variability at SO2 exposures to 200 ppb for one-hour 

duration. Tunnicliffe et al. (2003) did not show any change in lung function in a group of 

asthmatic and non-asthmatic subjects exposed to SO2 at 200 ppb. Although taken 

together, these five clinical studies may somewhat contribute to the weight of evidence 

concerning effects on the respiratory system and peak exposure to SO2, they do not 

contribute substantively to the information that was available to EPA previously and lend 

only marginal support to the ISA’s conclusion that a causal relationship exists between 

peak exposure to SO2 and effects on the respiratory system of exercising adult asthmatics. 

The ISA also concluded that “there is a likely causal relationship between short-term

(generally 24-h average) SO2 exposure at ambient levels and respiratory health effects, 

mostly based on the epidemiological studies.” Fifteen epidemiological studies, published 

since 1990 and conducted in the U.S. or Canada, are cited along with older studies in ISA 

Tables 5A-3 and 5A-4 as providing results on respiratory symptoms among children and 

on emergency department visits and hospital admissions in support of this finding. While 

the ISA acknowledges the numerous methodological issues in the interpretation of the 

human studies of air pollution, it does not discuss the implications of these issues 

specifically for SO2. A discussion of these issues is particularly important for SO2

because most of the studies on which the ISA relies, even those appearing after 1990, 

were published before the methodological difficulties were recognized. 

The ISA fails to discuss recent literature that has direct bearing on these issues, its review 

of individual studies is not sufficiently critical, and it does not recognize significant 

limitations. Specific issues that are not addressed adequately in the ISA include: 

treatment of exposure measurement error, the S-plus convergence problem, publication 
4

bias, effects of model choice, and interpretation of results in light of confounding by 

other pollutants, notably ozone and particulates. While the ISA acknowledges that 

exposure measurement error could seriously bias the results of epidemiological studies of 

air pollution, it should recognize that the correlation between ambient concentration 

measurements and personal exposures is poorly understood. The reanalyses of particulate 

time-series studies prompted by the S-plus convergence problem indicate that reanalyses 

of sulfur dioxide studies could be generally expected to result in effect estimates that 

become smaller and confidence intervals that become wider. A consequence of SO2 not 

having been the primary exposure of interest in recent studies is that the studies did not 

pay particular attention to optimizing analytic approaches and sensitivity analyses to the 

SO2 associations with health effects. Another consequence is the very real possibility of 

publication bias in the SO2 literature appearing in the last decade. With the generally 

small risks estimated in air pollution epidemiology, and the lack of biological information 

to guide the choice of models for control of weather, temporal trends and co-pollutants, 

the strategy for model selection for the analyses of time-series data is of critical 

importance. Although this problem of “model choice” is increasingly recognized in the 

epidemiological literature, most of the important papers on this issue have been ignored 

in the ISA.

Although the ISA admits to the uncertainties surrounding the interpretation of the health 

evidence from the epidemiological studies associated with ambient short-term SO2

exposure, it has neither discussed nor treated them appropriately. Because of the

profound unresolved issues, the fifteen epidemiological studies published since 1990 with 

U.S. or Canadian cohorts cannot be taken to support the existence of a likely causal 

relationship between short-term SO2 exposure and respiratory effects.
1

Attachment C

Memorandum from Edmund Crouch, Ph.D., to Utility Air Regulatory Group, Response to 

EPA-HQ-ORD-2006-0260-0036 (Feb. 5, 2010).
Cambridge Environmental Inc 

58 Charles Street Cambridge, Massachusetts 02141 

617-225-0810 FAX: 617-225-0813 www.CambridgeEnvironmental.com

MEMORANDUM 

 

To: Utility Air Regulatory Group 

From: Edmund Crouch, Ph.D. 

Subject: Response to EPA-HQ-ORD-2006-0260-0036 

Date: February 5, 2010 

Purpose of this memo 

As you requested, I have examined docket entry EPA-HQ-ORD-2006-0260-0036 consisting of a 

memorandum entitled “Quality assurance review of individual subject data presented in Table 3-

1 of the 2008 Integrated Science Assessment (ISA) for Sulfur Oxides” from Douglas Johns and 

Kirsten Simmons, EPA, NCEA-RTP to the Sulfur Oxides NAAQS Review Docket and dated 

October 2, 2009 (“Johns & Simmons Memo”). I have also examined the material in that docket 

associated with that memorandum (EPA-HQ-ORD-2006-0260-0036.1 through 0036.5, “Johns & 

Simmons Material”), and the final REA document EPA-HQ-OAR-2007-0352-0033 (“Final 

REA”). This memorandum presents my evaluation of the cited memorandum considered as a 

response to our previous technical comments.

The Johns & Simmons Memo is clearly a response to the discussion of data entry errors in our 

technical comments (EPA-HQ-OAR-2007-0352-0031.1, Attachment 1, “Our Comments”), and 

represents a welcome quality control step by the EPA, albeit one that should have been 

undertaken at the beginning of the process of utilizing these data. It appears that EPA has now 

done a relatively good job of entering the individual data for the Linn et al. studies, for those 

studies for which individual data are available in the previous air docket (previously A-84-25, 

now EPA-HQ-OAR-2004-0112, “Previous Data”). 

EPA data entry quality control 

I have examined the quality of the new EPA data entry by comparison with my own entries for 

sRaw only (not FEV1) for Linn et al. 1983 and 1987 (the sRaw data for the1983 study were not 

previously available; these data were provided by Ron Wyzga at EPA-HQ-OAR-2007-0352-

0038 and 0038.1 through 0038.8, “Wyzga Data”) and find that EPA now has only minor data 

entry errors for sRaw for these two studies. 

Specifically, for Linn et al. 1983 the following discrepancies still exist: 
Utility Air Regulatory Group 

Page 2 

February 5, 2010 

Cambridge Environmental Inc 

58 Charles Street Cambridge, Massachusetts 02141 

617-225-0810 FAX: 617-225-0813 www.CambridgeEnvironmental.com

Subject Condition When Column Presented EPA 

582 2 Pre Mean 5.76 5.75 

592 3 Pre Minute 7 2.67 2.69 

584 3 Post Minute 4 7.56 7.59 

416 2 Post Minute 7 5.62 5.66 

416 2 Post Mean 6.05 6.03 

Subject: subject ID used by Linn et al. 1983. 

Condition: the exposure group, as recorded in Wyzga Material. 

When: indicates pre or post exposure and exercise. 

Column: column in Wyzga Material, with “Mean” being the entry handwritten above the regular entry in Minute 7 

(corresponding to “Presented average” in the Johns & Simmons Material). 

Presented: value given on the handwritten sheet in the Wyzga Material (at 0038.2). 

EPA: value entered in the Johns & Simmons Material (at 0036.1).

For Linn et al. 1987 the following discrepancies still exist: 

Subject Day Conc. When Column Presented EPA 

879 2 0.6 ppm Post Measurement 4 35.78 35.75 

1051 2 0.2 ppm Pre Measurement 4 22.07 22.09 

611 2 0.2 ppm Post Measurement 2 14.51 14.54 

1028 1 0.4 ppm Pre Measurement 4 4.56 4.54 

892 2 0.4 ppm Post Measurement 4 29.46 29.76 

Subject: subject ID used by Linn et al. 1987. 

Day: day number of experiment as recorded in the Wyzga Material and Previous Data. 

Conc: exposure concentration. 

When: indicates pre or post exposure and exercise. 

Column: name of the column in the Johns & Simmons material. 

Presented: column is the value given on the relevant handwritten sheets in the Wyzga Material (at 0038.3 through 

0038.8), or equivalently in the Previous Data (at item IV-B-5). 

EPA: value entered in the Johns & Simmons Material (at 0036.2). 

The effect of the remaining data entry errors should be negligible on any correct analysis of the 

data (such as that I performed in Our Comments), although it might affect the EPA’s treatment (I 

have not checked) because EPA categorizes results as being above or below thresholds (so even 

minor differences in values can throw the entry into the wrong category). 

The data entries in the Johns & Simmons Material at 0036.3 check out against the Previous Data, 

but these are mean sRaw values only. EPA has apparently not located the individual raw data 

values for sRaw for this experiment (Linn et al. 1988). Presumably EPA originally had such 

data to produce these mean values, but copied only the mean values to the Previous Data. 

I have not checked the data entry in the Johns & Simmons Material at 0036.4, for Linn et al. 

1990 for sRaw (this file also contains individual raw FEV1 entries for Linn et al. 1988). The 
Utility Air Regulatory Group 

Page 3 

February 5, 2010 

Cambridge Environmental Inc 

58 Charles Street Cambridge, Massachusetts 02141 

617-225-0810 FAX: 617-225-0813 www.CambridgeEnvironmental.com

individual raw data are recorded in the Previous Data, but the quality is so low that I could not 

reasonably hope to decipher them within time and budget constraints. 

Effect of the data entry errors

The Johns & Simmons Memo is carefully worded: 

In conclusion, the results of the full quality assurance review of the individual 

subject data presented in Table 3-1 of the ISA, along with consideration of newly 

available data from Linn et al. (1983) do not result in any changes to the 

conclusions presented in the ISA for sulfur oxides (EPA, 2008). 

The conclusions presented in the ISA are qualitative, and indeed correction of the data entry 

errors does not change those qualitative conclusions. However, the draft REA (the subject of 

Our Comments) attempted to use these data for a quantitative assessment, as did the Final REA. 

The Final REA however, takes no notice of the corrections noted in the Johns & Simmons 

Memo, nor indeed of the additional data made available there (from Linn et al. 1983). Indeed, 

the Final REA was added to docket EPA-HQ-OAR-2007-0352 on 8/12/09, almost two months 

before the Johns & Simmons Memo was written (10/2/09). This is despite the corrections in the 

entries of Table 3.1 (on which the whole REA analysis was based) that were pointed out in Our 

Comments, and which have been confirmed by the Johns & Simmons Memo. 

The data entry in the Johns & Simmons Material allows me to correct and augment the data used 

for quantitative assessments in our technical comments. I expect to provide an updated version 

of those quantitative assessments in a separate entry to the docket (this work will not be funded 

by UARG). However, I expect no substantial change in the results obtained — the methodology 

we used is insensitive to the minor changes involved. 

Responses to other technical comments

The Johns & Simmons Memo acknowledges and corrects data entry error we pointed out in Our 

Comments. The Final REA (at pages 326–327) acknowledges the possibility of such errors, but 

does not correct them and ignores their potential consequences.1

 Apart from this, neither the 

Johns & Simmons Memo nor the Final REA responds in any meaningful way to Our Comments, 

despite the very substantial technical errors we identified and discussed at length. Indeed, the 

 

1

 EPA indicates that the effect of some data entry errors on the percentage responding was evaluated, but apparently 

there was no evaluation of the effect on the estimated dose-response parameters or number of events. The statement 

(Final REA, page 327) that “While staff placed more confidence in the average values presented rather than the 

calculated average of the individual measurements,” flies in the face of centuries of experience with hand 

calculations, and was of course contradicted by Professor Linn, who recommended reliance on the computed 

averages rather than the presented ones when they differed (Johns & Simmons Memo, page 2). 
Utility Air Regulatory Group 

Page 4 

February 5, 2010 

Cambridge Environmental Inc 

58 Charles Street Cambridge, Massachusetts 02141 

617-225-0810 FAX: 617-225-0813 www.CambridgeEnvironmental.com

Final REA is unchanged from the 2nd draft REA in all aspects upon which we commented. In 

summary, the Final REA maintains the multiple erroneous approaches we pointed out including: 

• Use of a response marker (exercise-corrected increment in sRaw) that is not predictive of 

symptoms, 

• Data entry errors, 

• The assumption of independence of observations a short time apart on the same 

individual, 

• Lack of accounting for variability in human responses and uncertainties in measurements, 

• Incorrect summing to obtain the total potential number of effects (by using 50 ppb bin 

sizes for exposures). 

The quantitative effect of retaining these erroneous approaches is that the REA overestimates the 

number of pulmonary function events by a factor of approximately 80 or more. 

Such complete lack of response is discouraging — ours was the only technical analysis of the 

REA, and our scientific analysis has been completely ignored. As stated above, I expect to 

provide to the Docket an updated analysis (not funded by UARG); this update will: 

• Prove the independence assumption is untenable (using data in the Agency’s possession), 

• Update the calculations in Our Comments to incorporate corrections in data entry and the 

Linn et al. 1983 data, 

• More correctly sum the total number of effects (again using data in the Agency’s 

possession). 
1

Attachment D

Eric S. Edgerton, Comments on Proposed SO2 Rule (Feb. 3, 2010). 
Comments on Proposed SO2 Rule 

Prepared by 

Eric S. Edgerton 

Atmospheric Research & Analysis, Inc. 

Cary, NC 27513 

EPA is proposing new performance requirements for the continuous FRM that are generally reasonable and 

likely to be achievable with current UV fluorescent (UVF) analyzers. It is not clear to me, however, that 

EPA has actually demonstrated compliance with all of the proposed new performance requirements. In 

addition, one major concern is the proposal to lower the allowable interference equivalent from +/- 20 ppb 

to +/- 5 ppb for each interferent and from 60 ppb to 20 ppb for the total of all interferents. The latter 

amounts to 20-40% of the proposed NAAQS (50-100 ppb) and provides much too much room for false 

positives. Not only that, but it is unclear whether or not present day analyzers are capable of limiting “total 

interference” to 20 ppb. 

The SEARCH network has amassed a record of “total interference” because of the unique approach it uses 

to zero SO2 analyzers. SEARCH uses a “native” zeroing approach, which involves scrubbing SO2

immediately upstream of the analyzer with a sodium carbonate impregnated annular denuder. The denuder 

removes SO2 and acidic gases, but allows basic and neutral gases to pass more or less quantitatively into 

the UVF detection cell. Ambient air is diverted through the annular denuder for 10 minutes every 2 hours 

and the resulting zeroes are used to continuously adjust the SO2 baseline by linear interpolation between 

successive zeros. The SO2 baseline is then subtracted from the total SO2 measurement to arrive at the 

“true” SO2 concentration. 

Figure 1 contains time series of maximum daily SO2 zeros for two urban SEARCH sites (Jefferson Street 

(JST), Atlanta, GA and Birmingham (BHM), AL) for CY 2008 and CY2009. Values shown are 5-minute 

averages and reflect the last 5 minutes of data when the zeroing scrubber is engaged. It should be noted 

that instrument baselines are initially set to 0.5-1.0 ppb with scrubbed zero air and therefore the “total 

interference” is roughly equal to the maximum daily SO2 zero minus 1 ppb. Inspection of Figure 1 shows 

several relevant features. First, the lowest zeros are on the order of 0.5-1 ppb, the scrubbed zero air 

setpoint. This indicates there are times with little or no interference, but also strongly suggests that the 

preponderance of interferences in these two cities are positive (i.e., increase apparent concentrations). 

Second, “total interferences” for both sites exceed 10 ppb, but maximum values at JST are more than twice 

those at BHM (i.e., 27 ppb vs. 12.5 ppb). This is significant because Birmingham, AL has many industrial 

sources, including metallurgy and steelmaking that are absent or much more limited in Atlanta, GA. If 

daily maximum zeros were higher at BHM than JST, we might ascribe such to unique industrial sources. 

Since this is not the case, we infer this level of interference to be widespread among urban sites. Third, 
there is a strong seasonality in the zeros and this is much more apparent at JST than BHM. Highest zeros 

occur in the coldest months and lowest zeros in the warmest months. Maximum daily zeroes above 5 ppb 

are rare at JST from April through September, but much more common at BHM during the same time 

period. Given that these are intermittent estimates of interference (i.e., every two hours) it is almost certain 

that that actual interferences were even higher than those shown in Figure 1. 

The above results show that “total interference” in SO2 measurements, using late model continuous 

analyzers, can be a serious issue and can potentially lead to false positive exceedances of the proposed 

NAAQS. It then becomes incumbent upon EPA to demonstrate that FRM and FEM SO2 analyzers have the 

capability to minimize interferences, not only in a laboratory setting, but on a continuing basis in the field. 
Figure 1. Maximum daily SO2 zeros (5-minute average) for JST (upper) and BHM (lower), 2008-9. 

JST Max SO2 Zero

0

5

10

15

20

25

30

1/1/082/1/083/1/084/1/085/1/086/1/087/1/088/1/089/1/08

10/1/0811/1/0812/1/08

1/1/092/1/093/1/094/1/095/1/096/1/097/1/098/1/099/1/09

10/1/0911/1/0912/1/09

BHM Max SO2 Zero

0.0

2.5

5.0

7.5

10.0

12.5

15.0

1/1/082/1/083/1/084/1/085/1/086/1/087/1/088/1/089/1/08

10/1/0811/1/0812/1/08

1/1/092/1/093/1/094/1/095/1/096/1/097/1/098/1/099/1/09

10/1/0911/1/0912/1/09