From: "Frey, Nathan J." <Nathan_J._Frey@omb.eop.gov>

To: Lydia Wegman/RTP/USEPA/US@EPA

Date: 06/06/2012 08:00 AM

Subject: Summary of Interagency Comments Under EO 12866/13563: National Ambient Air Quality 

Standards for Particulate Matter NPRM

Attached please find a summary of interagency comments under EO 12866/13563 

on the EPA proposed rule regarding National Ambient Air Quality Standards for 

Particulate Matter: RIN 2060-AO47.

Thank you and please let me know if you have any questions.
Summary of Interagency Working Comments on Draft Language under 

EO12866/13563 Interagency Review. Subject to Further Policy Review.

General Comments

1) Attainment and Monitoring

EPA proposes to eliminate spatial averaging and "population-oriented" monitor 

placement, while mandating a near-road component to monitoring plans. Some 

commenters believe that these three provisions are internally inconsistent. Spatial 

averaging is a statistical means of expressing the 'ambient' aspect of "National 

Ambient Air Quality Standards." Averaging over the regulated area creates the 

regulatory consistency for the regional jurisdictions that is key to the regionallycontrolled implementation of the NAAQS. EPA cites the possibility of disparate 

health effects on disadvantaged populations as the reason for eliminating averaging.

However, EPA also proposes to eliminate "population-oriented" monitor placement, 

since EPA says that the concept of a monitor being population-oriented is 

incompatible with the 'ambient' nature of the NAAQS. In this provision, EPA 

dismisses linking NAAQS attainment to health effects as inconsistent with statute, 

even though the touchstone of the NAAQS standards is in fact public health.

2) Some commenters believe that EPA's reasoning for a near-road component to 

monitoring plans is inconsistent with its reasoning above. Near-road PM levels are 

not necessarily representative of actual risk to susceptible populations through 

exposure to PM. Nor is the placement of near-road monitors calculated to be a 

better proxy for health effects than "population-oriented" monitors. The 

elimination of spatial averaging and "population-oriented" monitors and the 

establishment of near-road monitors can only have the effect of making NAAQS 

attainment more difficult.

3) Some commenters also note that the proposed PM standards and their impacts 

appear to be based on existing monitoring systems, such that the addition of nearroad monitors can increase the costs by putting additional areas into nonattainment 

without associated health benefits.

4) Some commenters note that any difficulties in achieving attainment will likely 

translate into difficulties in PSD permitting. The elimination of spatial averaging, 

along with the inclusion of near-road monitors, is likely to make it more difficult to 

obtain permits. These commenters note that where EPA changes its interpretation 

about 'exclusion of some receptors' in PSD analyses, it does account for these 

changes and suggest that EPA clearly identify how these changes may or may not 

affect permitting decisions.
Summary of Interagency Working Comments on Draft Language under 

EO12866/13563 Interagency Review. Subject to Further Policy Review.

5) Communication of Public Health Information (Pages 218-225) from 

EO12866_PM_NAAQS_2060AO47_NPRM_Preamble_and_Reg_Text_20120529

Some commenters have concerns about the inclusion of the Air Quality Index (AQI) 

for PM2.5 into the NAAQS proposal at both ends of the index value spectrum. There 

are concerns that the upper levels of the AQI (200-500 index value) being proposed 

are not scientifically justified and will potentially have substantial agency resource 

impacts. Specific implications include large increases in wildfire suppression costs 

and decrease needed decision capability on wildfires. The proposed potential 

deviation from defining the 100 index value at the 24hr NAAQS will lead to the 

development of a presumptive standard and will potentially further hinder critical 

prescribed fire operations. As this section (pp. 218-225) is not a requirement of the 

NAAQS, and therefore not part of the court mandated material, commenters 

recommend that it does not need to be part of this proposal. These commenters

strongly recommend the removal of this section to allow for needed discussion and 

development of a sound and interagency supportable proposal for the AQI for 

PM2.5. Accompanying this specific comment and several comments below are 

attached suggested edits regarding the relevant section of the preamble.

6) A critical and ecologically indispensable method of addressing hazardous fuels 

across Federal lands is the use of prescribed fire. Managers conduct burns routinely 

up to the NAAQS 24hr standard level. Commenters express concerns that the public 

perception of the AQI being “unhealthy for sensitive groups” at a lower value than 

the NAAQS may lead to further challenges to conducting these burns in a safe, 

economically efficient and prudent fashion. Commenters express concern that a

sub-NAAQS level may lead to a functional standard in application by air quality 

regulatory agencies. This creates a public perception that would pit beneficial and 

ecologically necessary prescribed fire and fuel mitigation measures against local air 

quality objectives and messages. Less prescribed fire may negate the air quality 

benefits of judicious prescribed fire application as compared to vast PM2.5 and 

green house gas emissions from catastrophic wildfire. Commenters also note that 

smaller prescribed fires necessitated by such a presumptive standard can lead to 

higher risk to firefighters and substantial cost increases, which may also pose 

further challenges to wildland-urban interface hazardous fuels treatments.

7) The reduction in upper thresholds of the AQI (200-500 index value) do not appear 

to be well supported by the 1952 based science provided in the proposal. In 

addition, the public perception of wildfire response decisions which result in 

extended periods of “hazardous” air quality may lead to additional pressure for 
Summary of Interagency Working Comments on Draft Language under 

EO12866/13563 Interagency Review. Subject to Further Policy Review.

suppression with its attendant costs as well as risks to firefighters. Wildfires can 

create high levels of PM2.5 that can be well above the proposed upper threshold for 

the AQI for significant periods of time. Assessment of the AQS as well as other 

monitoring networks show wildfire as the most common cause of high PM2.5 level 

at the AQI of threshold of “hazardous” as proposed. Commenters express concern 

that a public expectation for response could result when levels reach “hazardous” by 

all public agencies involved. Expectations and role for the federal agency wildland 

fire programs and wildland fire incident management teams are not well defined in 

this rulemaking package but can be significant. Commenters note that the science 

for such response needs to be supported and developed and further discussion of 

the AQI thresholds could provide the opportunity for efficient and cohesive planning 

for such impacts. 

8) Some commenters express concerns that the data used to propose the threshold for 

“hazardous” AQI values is not current. Commenters suggest that further work 

should be conducted to set this threshold. The technical basis for the proposed 

values is based upon outdated data from British coal combustion and secondary 

sulfate pollutions and is not related to wildfire (biomass combustion) which would 

be the likely cause of contemporary high AQI values. With the public expectations 

and potentially large costs associated with setting and responding to a trigger such 

as “hazardous” air quality, a scientifically rigorous approach that considers the likely 

causes of such an event in the US and one that uses national data is needed rather 

than a sub-regional data analysis process. The balance of PM2.5 and PM10 

contribution from the likely triggering sources in the US should be considered in the 

analysis. Development of the upper AQI values can be implemented with good 

interagency coordination and with consideration of current technical capability.

9) A Statistical Test for Translating Evidence Into PM Standards: 

A commenter has suggested consideration of the following methodology for EPA to 

consider in setting the PM standard. In the studies in which EPA has determined 

they have confidence (those with “causal or likely causal relationships”), EPA states 

that the statistical relationship between dose and response can best be described by 

a linear equation (which is significantly different from zero, statistically). However, 

this linear approximation of the true underlying relationship is only valid over the 

actual values of PM levels observed in the study – there is no evidence that the 

relationship will remain linear at PM levels lower than those observed. This fact can 

be used to construct a statistical test to determine the lowest PM level at which 

there is still evidence that the linear dose-response relationship is significantly 

different from zero. EPA could then consider, subject to the authorities under the 
Summary of Interagency Working Comments on Draft Language under 

EO12866/13563 Interagency Review. Subject to Further Policy Review.

Act, setting the PM standard at the average of the results of this test for the studies 

in which EPA has confidence.

After sorting the data of a given study by PM level, if the data point with the highest 

PM level is excluded, the sample mean of PM levels will be slightly lower. EPA can 

test this subsample to see if it still supports the hypothesis of a linear dose-response 

level different from zero (technically speaking, to see if the null hypothesis of a 

relationship equal to zero is rejected). If so, EPA could then exclude the next highest 

data point and repeat the test, and so on until the null hypothesis cannot be rejected. 

Retain the sample mean of the last subsample to reject the null hypothesis, and 

collect the results of similar tests for all studies that found a linear relationship 

significantly different from zero. Averaging all of these results can be used to inform

the PM standard.

10)Health Effects of PM vs. Ozone:

For epidemiological studies that explicitly test for the health effects of PM vs ozone 

and other pollutants, are the dose-response relationships for PM weaker than those 

that test for the health effects of PM only? If so, has EPA given more weight to these 

studies in setting the standard?

11)Extrapolated Costs: Could EPA please put a spreadsheet in the docket with PM2.5 

emissions by subsector (we’re most interested in the EGU, non-EGU point sources, 

area sources, onroad, nonroad, and alm subsectors) for each county that is found 

not in attainment in 2020 after all known technologies have been implemented? If 

such a document is already in the docket, please provide its document number.

12)Some commenters urge EPA to include in the preamble for the rule its view on the 

limitations and uncertainties in the currently available evidence that relate to 

association of distinct components of PM2.5 with different health endpoints. 

Commenters also request that EPA seek comment on those limitations and 

uncertainties.

13)Commenters propose a single paragraph to be added to the Preamble section 

entitled “Limitations and Uncertainties of Currently Available Evidence” on pages 

63-64. The suggested inserted text for consideration is presented here in context 

with the paragraphs that would be before and after the text:

[Existing text] In addition, where PM2.5 and other pollutants (e.g., ozone, nitrogen 

dioxide, and carbon monoxide) are correlated, it can be difficult to distinguish the 

effects of the various pollutants in the ambient mixture (i.e., co-pollutant 
Summary of Interagency Working Comments on Draft Language under 

EO12866/13563 Interagency Review. Subject to Further Policy Review.

confounding). Although many recent U.S. multi-city studies did not analyze 

multipollutant models, evidence from single-city studies available in the last review 

suggest that gaseous copollutants do not confound the PM2.5-related mortality 

association (US EPA, 2004, section 8.4.3.3) which is further supported by studies 

that examined the PM10-mortality relationship (US EPA, 2009a, p. 6-182 and 6-

201). 

[Text proposed for insertion] Similarly, EPA has not found evidence that distinct 

components of PM2.5 differentially affect specific health endpoints. Although EPA 

has not applied the criteria in Table 1-2 of the Integrated Science Assessment to 

individual species of PM2.5, the currently available evidence does not appear to 

support an attribution of health effects to black carbon that can be distinguished 

from other components of PM2.5. Because scientific understanding of this issue 

continues to evolve, specifically with regard to the toxicity of black carbon (and 

potentially other PM2.5 components) relative to other species of PM2.5, EPA seeks 

comments on whether or how uncertainties related to attribution of health effects to 

specific components of PM2.5 could be addressed.

[Existing text] While uncertainties and limitations still remain in the available 

health effects evidence, the Administrator judges the currently available scientific 

data base to be stronger and more consistent than in previous reviews providing a 

strong basis for decision making in this review.

Specific comments regarding the Primary Standard

14)Suggest explaining more clearly why a risk assessment was not used for 

recommending a specific level of the standard (beyond supporting the conclusion 

that the annual standard should be controlling)

15)Suggest providing a more clear explanation for why “the number of participants 

within each study area can be used as a surrogate for health event data in relation to 

the distribution of PM2.5 concentrations” for considering the 25th and 10th 

percentiles.

16)Throughout (and drawing on language from CASAC, perhaps?), the preamble 

references “the broader range of PM2.5 concentrations that were most influential in 

generating health effect estimates in epidemiological studies” (see p. 46). Suggest 

providing a more clear explanation of what is meant by “most influential,” as this 

will likely be confusing for many readers.
Summary of Interagency Working Comments on Draft Language under 

EO12866/13563 Interagency Review. Subject to Further Policy Review.

17)Pg. 49 describes a number of uncertainties that relate to staff recommendations 

about the level of the standard. Shouldn’t one of the uncertainties (referenced here 

and perhaps elsewhere) be limited data on health effects at lower concentrations? 

18)Suggest incorporating a more expanded discussion of the work that was done in 

response to CASAC and public comments on the Second Draft Policy Assessment 

(perhaps drawing from the cover letter for the Final PA). 

19)Suggest that EPA more explicitly describe how the Administrations proposed 

conclusions on the primary standards (p. 143) address requisite protection for 

especially susceptible or vulnerable populations.

20)Relevant to figure 4: Given that this is a critical figure for understanding the Policy 

Assessment’s and the Administrator’s reasoning for selecting the proposed level of 

the standard, some commenters suggest providing a more consolidated explanation 

of how the chart should be interpreted. That would likely require recapping 

information already discussed at greater length elsewhere, but would focus on how 

the chart itself should be understood.

Specifically, it is not immediately clear what “mean” the diamonds, triangles, and 

squares represent (in fact, this is simply the mean observed PM levels from the 

relevant studies). As a result, the casual (or even non-casual) reader could easily 

assume that, because the bulk of the points here are between 13 and 15, the 

evidence points to the “right number” (perhaps the minimum level at which an 

effect was found) being within this range. It should be made very clear what these 

points do and don’t represent.

Commenters strongly suggest making more clear (in both the figure itself and the 

description of the figure) that the 25th and 10th percentile bars displayed here are 

based on health event data (or proxies for health event data). This is not clear, 

particularly given that the long-term means displayed here (if understood correctly) 

are actually from a different distribution – they are means of the observed air 

quality and do not specifically represent a range of observed health events/effects.

If the diamonds, triangles, and squares do represent the 50th percentile of air 

quality rather than the 50th percentile of health outcome, then the rationale for 

doing so should be explained more clearly in the text. Specifically, the text seems to 

hint that the reason for examining the distribution is that there is less confidence in 

results at health levels for which data are more sparse. If so, it would seem that the 
Summary of Interagency Working Comments on Draft Language under 

EO12866/13563 Interagency Review. Subject to Further Policy Review.

relevant 50th percentile should be for health, not for ambient pollution. If there is an 

accepted peer-reviewed method that links “confidence” in results to density of data 

points that would support EPA’s approach, that should also be referenced. If not, 

EPA should state that their approach is based on heuristics. EPA may also wish to 

consider replacing the shapes with 50th percentile health effects.

EPA should consider placing asterisks next to the studies that are relevant for 

susceptible and vulnerable populations.

21)In a number of places, the preamble states that the Administrator “provisionally 

concludes” some matter regarding the NAAQS revision. Appreciating that EPA may 

be using this term to signal that the Administrator has not yet made her final 

decision; however, a commenter felt thatthe term “provisionally concludes” seemed

odd, as if there is some further action or specific information upon which the 

Administrator’s final decision will depend. EPA should consider using the phrase: 

“proposes to conclude” .

Specific Comments regarding the Secondary Standard

22)Some commenters request clarification regarding welcome why EPA believes that it 

must revise the secondary PM standard. Commenters note that EPA does not have 

estimates of the costs and benefits such a revision adds to the rule, and as such has a 

limited justification that the preferred standard is 'requisite to protect public 

welfare.' Commenters also express concern about EPA's reliance on a willingnessto-pay methodology as the basis for its future benefits estimate, expressing doubt 

that the methodological problems inherent in WTP can be adequately addressed 

and resolved in the short timetable for interagency review. Finally, several 

commenters expressed significant concern that EPA is moving forward with a 

secondary standard based on an indicator, in light of CASAC’s statement in their 

review of the Second External Review Draft Policy Assessment, that “Overwhelmingly, 

CASAC would prefer the direct measurement of light extinction, the property of the 

atmosphere that most directly relates to visibility effects.” Furthermore, several 

commenters expressed similar concerns regarding EPA’s consideration, 

recommended by CASAC, of the potential radiative forcing impacts aerosol 

reductions.

23)Some commenters suggest that EPA should request comment whether it should 

move forward with the primary and secondary standards on the same timeline and 

on whether the designations must move forward in tandem. This is especially 

important given how different the visibility measure is from previous efforts and 
Summary of Interagency Working Comments on Draft Language under 

EO12866/13563 Interagency Review. Subject to Further Policy Review.

given that major rules affecting PM (GHG mobile sources and Boiler MACT) are not 

included in the baseline analysis and the significant work required in some states to 

comply with CSAPR-better-than-BART or state-specific consent decrees.

24)Some commenters recommend that EPA should signal maximum flexibility in its 

enforcement of CAA timelines. For example, EPA has discretion to provide up to 2 1-

year extensions on secondary standards. Given the nature of this new requirement 

and the modeling difficulties that EPA acknowledges, EPA should indicate 

willingness to grant these extensions. 

25)Under 40 CFR 52.21(o) and (p), visibility analyses are routinely conducted as part of 

the PSD process. Commenters express concern regarding the potential creation of a 

different set of analytical requirements for the PM2.5 visibility index that may create 

"competing" techniques for visibility assessment between the proposed PM2.5 

visibility index and Class I procedures which could undermine existing processes 

and requirements used to protect visibility in Class I wilderness areas. 

26)Some commenters suggest that the Agency remove the language describing a 

paucity of supporting speciation data. This language could be construed such that 

the current methods used for visibility assessment for Class I analyses are not 

adequate, and that EPA is instead proposing to use a simple surrogacy technique. 

The implications of this could weaken the technical credibility of the tools used for 

Class I visibility assessments under 40 CFR 52.21(p) or the Class II visibility 

assessments under the Additional Impact Analysis ( 40 CFR 52.21(o)) of the PSD 

rule. Moreover, at 70 FR 39121 EPA identified the CALPUFF system as "the best 

currently available tool for analyzing the visiblity effects of individual sources." 

These commenters requested clarification upon why the methods that have been 

routinely used for visibility assessment under the PSD program are not deemed 

applicable to the proposed PM2.5 visibility index. 

27)Preferred Form of IMPROVE Algorithm

Some commenters express specific concerns regarding the discussion starting on 

page 239 of NPRM_Preamble_and_Reg_Text and note that it is important that the 

“revised” form of the IMPROVE equation (split-component mass extinction 

efficiency) be presented as the preferred algorithm. Commenters express concern 

that to do otherwise undermines the robust science and modeling procedures 

inherent in the Regional Haze Rule and under the PSD program. Adopting the old 

form of the IMPROVE equation would, in essence, create additional, sometimes 

competing analytical requirements in the major source permitting process if 
Summary of Interagency Working Comments on Draft Language under 

EO12866/13563 Interagency Review. Subject to Further Policy Review.

permitting procedures must be enacted for comparison against the secondary 

PM2.5 standard.

28)Some commenters note practical difficulties associated with the implementation of a 

sub-daily visibility NAAQS, which would require application of historical averages of 

speciation profiles from the closest STN monitoring site and require application of 

same day hourly relative humidity values. 

29)Some commenters also note difficulties associated with using historical monthly or 

seasonal speciation averages or estimates as surrogates for calculating light 

extinction for consideration of use with either continuous FEM or gravimetric FRM 

PM2.5 mass samplers.

30)Please clarify what background visual range would be used to compare light 

extinction against if this proposal is simply based upon absolute deciviews. This is 

an important implementation aspect of this proposed rule which should be aligned 

with the components of the Regional Haze Rule which requires current visual air 

quality to be compared to "natural background" in order to determine progress 

towards the RHR goals. 

31) Some commenters strongly support the use of the climatological relative humidity 

values based upon either the 2003 EPA guidance or similar guidance (e.g. FLAG 

2010). Normalization of RH values through the use of climatic means is an efficient 

means to avoid justifying exclusion of certain hours based upon the presence of 

weather events. This could occur if air quality modeling is required for the 

secondary NAAQS under the PSD program.

32) The description of the policy assessment states that “...the Policy Assessment notes 

that this scatter could be reduced by the use of same-day hourly relative humidity 

data to calculate a 24-hour average value of the relative humidity term in the 

IMPROVE algorithm.” Commenters request clarification of this concept noting that 

the 24-hour average f(RH) is not the same as calculating a 24-hour average relative 

humidity and applying it to the f(RH). Calculating 24-hour f(RH) (with hourly RH 

values capped at 95%) is the appropriate procedure if this were to be followed.

33) Some commenters do not support alternatives that cap relative humidities at 90 

percent. The approach described for the policy assessment of capping at 95% is the 

most appropriate and is consistent with FLAG guidance.
Summary of Interagency Working Comments on Draft Language under 

EO12866/13563 Interagency Review. Subject to Further Policy Review.

34)The preamble should discuss whether it is premature to establish a new secondary 

standard when there is not a suitable indicator and the scientific support underlying 

the standard is so uncertain. The preamble should also note that the Agency will 

continue to develop methods for an indicator and seek to reduce the uncertainty in 

the scientific literature before the next review. A commenter also suggested the 

proposal could seek comment on setting the secondary standard equal to the 

primary standard.

35)As the preamble notes, CASAC overwhelmingly recommended using a direct 

measurement of light extinction as the indicator for the secondary standard. The 

preamble states that the Administrator concurs.

36)Given that CASAC suggested the indicator approach would best be considered an 

interim approach, please indicate in the preamble how long it would take to finalize 

an FRM for direct measurement of light extinction. What steps are necessary to 

complete this process?

37)On pg 280. what does it mean that the Administrator “provisionally” concludes a 

new calculated light extinction indicator is appropriate? Please clarify whether the 

calculated light extinction indicator is merely an interim indicator until a direct 

measurement indicator can be established. If this is an interim indicator, 

specifically what steps does EPA plan to take to replace the index with a direct 

measurement approach?

38)Please indicate how difficult and expensive it would be for delegated authorities to 

implement a new secondary standard, recognizing that it will require new tracking 

systems, recordkeeping and reporting systems, QA systems, etc. Please provide 

some estimate of the impact on state resources, and request comment from the 

states on the accuracy of these estimates

39)Pg 253. indicates that the 4 visibility preference studies differ on “specific wording 

used to frame questions used in the group interview”. Please expand the discussion 

of these differences. Also, please explain how the wording used to frame the 

questions aligns with language that defines acceptability in the Clean Air Act. Did 

the researchers use the Clean Air Act as a starting point to define acceptability, and 

how was this translated to study subjects?

40) Pg 256-257. Please note that the DC and Denver studies have a roughly 2.5 fold 

difference (75 to 200 Mm-1) between the median visibility levels that were deemed 
Summary of Interagency Working Comments on Draft Language under 

EO12866/13563 Interagency Review. Subject to Further Policy Review.

acceptable. Please note that this high relative difference calls into question the 

reproducibility and reliability of the underlying studies.

RIA Comments 

1) Some commenters request clarification why GHG emissions rules for passenger 

vehicles and heavy-duty vehicles were not included in the baseline, particularly 

given the inclusion of near-road monitoring.

2) Some comments would like to suggest an alternate baseline analysis be conducted 

that would include the Boiler MACT and CISWI rules in the baseline, particularly as 

they are expected to be final before this rule will be. Commenters would also 

suggest the Regional Haze policies (including any State-specific regional haze 

controls or consent decrees that fall outside the CSAPR-better-then-BART 

rulemaking) and the RICE rule be also included in this alternate baseline.

3) Some commenters note that characterization of the baseline could have a major 

effect on the alternatives analysis, given the significantly lower costs and benefits of 

the 13/35 alternative. If inclusion of the GHG mobile source rules and the Boiler 

MACT rules has a significant effect on the baseline, it could drastically change the 

benefit-cost ratio of the preferred alternative.

4) Some commenters note that it is not clear why EPA has not attempted to “estimate 

costs that government agencies may incur for managing the requirement,” and 

request clarification whether this will be done for the final RIA. These commenters 

note that it would be helpful for EPA to provide a rough estimate of how much it 

would cost for state and local air authorities to implement a new secondary 

standard while seeking public comment on the issue.

5) The document states that “Costs of federal and state administration of SIP program” 

is an un-quantified cost, but also says that it could bias the overall cost estimate high 

or low. If these costs are not estimated, it is not clear how they could necessarily 

lead to a high bias. Please clarify.

6) Some Commenters suggest that EPA itemize and take comment on the areas where 

the RIA has not provided a quantitative analysis of the potential impacts of the rule. 

For example, EPA does not provide a quantitative estimate of the cost or benefits of 

additional permitting requirements in both attainment and non-attainment areas. 

PSD permitting is one of the earliest and potentially most important impacts of a 

NAAQs. In addition, EPA does not provide an analysis of the costs and benefits of 
Summary of Interagency Working Comments on Draft Language under 

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non-attainment, over and above the controls that need be adopted in order to attain. 

For example, an area being found in non-attainment certainly will be impacted, even 

if they were to be able to rely completely on “on the books” controls to attain. NSR 

permitting, and the requirement to find offsets for new construction, perhaps is the 

most prominent example, but other NAAQs obligations such as SIP development and 

approval and other showings required by a non-attainment decision could also be 

important and have impacts. 

7) Some commenters suggest that EPA include a note of explanation as to why DSI is 

not included as a possible SO2 control strategy, along with flue gas desulfurization. 

DOE suggests EPA may want to consider this control technology as a sensitivity case 

in future analysis for the final revision of the standard.

8) Some commenters note that EPA appears to have used dated reports (2009 and 

2006 and many older) to calculate economic value of avoided PM2.5 morbidities 

and premature deaths. 

9) On page 5-33, commenters suggest that EPA clarify how one report is selected over 

another when more than one report exists that detail pollutant results.

10)EPA assumes that all fine particles, regardless of their chemical composition, are 

equally potent in causing premature mortality. Commenters encourage EPA to 

review literature suggesting that there may be evidence to support a differentiation 

in the association of health endpoints with specific components of PM2.5.

11)Section 11.3.1, Page 11-4: “However, the environmental protection sector often sees 

immediate employment effects.” Please provide a definition and examples of the 

“environmental protection sector.”

12)Chapter_4--Control_Strategies_5-22-12_revised_clean.docx

Page 4-6: Under area sources: some commenters suggest changes that cite use of 

Basic Smoke Management Practices and Establishment of Smoke Management 

Programs rather than current controls suggested of “Episodic Bans on Open 

Burning, Substituting Chipping for Open Burning and Household Burning and 

Seasonal Ban on Agricultural Burning.”

13)Page 4-10: The following sentence was in the draft: “Controls for area sources were 

applied to: home heating, restaurant operations, as well as controls on burning.” Yet 

when one reviews the emission inventories used for modeling of the PM NAAQS, 
Summary of Interagency Working Comments on Draft Language under 

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open burning was not cited and the 2005 NEI had very little prescribed fire and 

open burning included based on the summary of the 2005 NEI from the 2005 

National Air Toxics Assessment. Please clarify what was done and what controls are 

implied. If reductions were applied to prescribed fire, we are likely perpetuating the 

potential for catastrophic wildfire and emissions. This also relevant with statement 

on pages 4-14 to 4-15 that says ”Area source controls assume a constant estimate of 

emission reductions, despite variability in extent and scale of application.” 

14)Chapter_10--Secondary_Standard_0529

Page 2: Current proposal states: “Smoke from wildfires is an important contributor 

to visibility impairment in the western U.S., and particulate nitrate contributes to 

decreased visibility in California and the upper Midwest, particularly during the 

winter (U.S. EPA, 2009).” Commenters point out that by EPA Regional Haze 

Guidance the smoke from wildfires is considered natural background and makes 

this statement potentially very misleading as impairment is usually associated with 

anthropogenic sources.

15)Commenters request that EPA better explain why coarse PM does not have benefit 

cost analysis for alternative standards (e.g., this was already done last time around 

and there is no change) and provide reference for most recent analysis.

16)P. ES-3 “The baseline includes reductions already achieved as a result of national 

regulations, reductions expected prior to 2020 from recently promulgated national 

regulations (i.e., reductions that were not realized before 2005 but are expected 

prior to attainment of the current PM standard)...” Please explain why 2005 is the 

relevant year for baseline (versus, say 2012).

17)P.2-13 “ For example, Figure 2-8 shows that visual range increased nearly 50% in 

the eastern U.S. since 1992.” Please explain how the Figure shows this. Charts don’t 

seem to show distribution of days between three categories. Visibility on best days 

may be getting better, but might there be fewer best days, leading to an overall 

decrease in visual range?

18)P. 6-15 Commenters suggest Striking the following language from footnote 14 “EPA 

believes the study has received adequate review and has been cited in numerous 

peer-reviewed publications (e.g., Chestnut and Dennis, 1997).” Commenters note 

that being cited doesn’t necessarily lend specific credibility to a study (somebody 

could be citing it as a bad example).

19)P. 10-5 Figure 10-2 should indicate the year in the title.
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20)Ch. 10 In general there should be more detailed discussion regarding the 

uncertainty of modeling attainment with secondary NAAQS. In particular it should 

be emphasized that although EPA does not currently believe that any county that is 

in compliance with primary will violate secondary, different trajectories may lead to 

cases in which the secondary standard is binding.
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I. Communication of Public Health Information

Sections 319(a)(1) and (3) of the CAA require the EPA to establish a uniform air quality 

index for reporting of air quality. These sections specifically direct the Administrator to 

‘‘promulgate regulations establishing an air quality monitoring system throughout the United 

States which utilizes uniform air quality monitoring criteria and methodology and measures such 

air quality according to a uniform air quality index’’ and ‘‘provides for daily analysis and 

reporting of air quality based upon such uniform air quality index...’’ In 1979, the EPA 

established requirements for index reporting (44 FR 27598, May 10, 1979). The requirement for 

State and local agencies to report the AQI appears in 40 CFR 58.50 and the specific requirements 

(e.g., what to report, how to report, reporting frequency, calculations) are in appendix G to 40 

CFR part 58.

Information on the public health implications of ambient concentrations of criteria 

pollutants is currently made available primarily through EPA’s AQI program. The current AQI 

has been in use since its inception in 1999.1It provides accurate, timely, and easily 

understandable information about daily levels of pollution (40 CFR 58.50). The AQI establishes 

a nationally uniform system of indexing pollution levels for ozone, carbon monoxide, nitrogen 

dioxide, PM and sulfur dioxide. The AQI is also recognized internationally as a proven tool to 

effectively communicate air quality information to the public. In fact, many countries have 

created similar indices based on the AQI. 

The AQI converts pollutant concentrations in a community’s air to a number on a scale 

 

1

In 1976, the EPA established a nationally uniform air quality index, then called the Pollutant 

Standard Index (PSI), for use by State and local agencies on a voluntary basis (41 FR 37660, 

September 7, 1976). In August 1999, the EPA adopted revisions to this air quality index (64 FR 

42530, August 4, 1999) and renamed the index the AQI. 
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from 0 to 500. Reported AQI values enable the public to know whether air pollution levels in a 

particular location are characterized as good (0–50), moderate (51–100), unhealthy for sensitive 

groups (101– 150), unhealthy (151–200), very unhealthy (201–300), or hazardous (300–500). 

The AQI index value of 100 typically corresponds to the level of the short-term (e.g., daily or 

hourly standard) NAAQS for each pollutant. Below an index value of 100, an intermediate value 

of 50 was defined either as the level of the annual standard if an annual standard has been 

established (e.g., PM2.5, nitrogen dioxide), or as a concentration equal to one-half the value of the 

short-term standard used to define an index value of 100 (e.g., carbon monoxide). An AQI value 

greater than 100 means that a pollutant is in one of the unhealthy categories (i.e., unhealthy for 

sensitive groups, unhealthy, very unhealthy, or hazardous) on a given day. An AQI value at or 

below 100 means that a pollutant concentration is in one of the satisfactory categories (i.e., 

moderate or good). Decisions about the pollutant concentrations at which to set the various AQI 

breakpoints that delineate the various AQI categories draw directly from the underlying health 

information that supports the NAAQS review.

Historically, state and local agencies have primarily used the AQI to provide general 

information to the public about air quality and its relationship to public health. For more than a 

decade, many states and local agencies, as well as the EPA and other Federal agencies, have 

been developing new and innovative programs and initiatives to provide more information to the 

public, in a more timely way. These initiatives, including air quality forecasting, real-time data 

reporting through the AIRNow website2, and air quality action day programs, can serve to 

provide useful, up-to-date, and timely information to the public about air pollution and its 

effects. Such information will help individuals take actions to avoid or to reduce exposures to 

 

2

See http://www.airnow.gov/index.cfm?action=airnow.showlocal&cityid=204. 
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ambient pollution at levels of concern to them and can encourage the public to take actions that 

will reduce air pollution on days when levels are projected to be at levels of concern to local 

communities. Thus, these programs have significantly broadened the ways in which state and 

local agencies can meet the nationally uniform AQI reporting requirements, and are contributing 

to state and local efforts to provide community health protection and to attain or maintain 

compliance with the NAAQS. The EPA and state and local agencies recognize that these 

programs are interrelated with AQI reporting and with the information on the effects of air 

pollution on public health that is generated through the periodic review, and revision when 

appropriate, of the NAAQS.

In recognition of the proposed changes to the suite of primary PM2.5 standards 

summarized in section III.F above, the EPA proposes conforming changes to the AQI to be 

consistent with the proposed changes to the standards. The health effects information that 

supports the proposed decisions on the PM2.5 standards as discussed in section III.B above is also 

the basis for the proposed changes in the AQI discussed below in this section. The EPA intends 

to finalize conforming changes to the AQI in conjunction with the Agency’s final decisions on 

the primary annual and 24-hour PM2.5 standards, if revisions to such standards are promulgated. 

Note that, currently, we are cautioning members of sensitive groups at the AQI value of 100 at 

35 μg/m3, 24-hour average, because this is the level that was provided in guidance (Harnett, 

2009, Attachment B) which, in essence, superseded the AQI value of 100 established in 1999 (64 

FR 42530, August 4, 1999).3

With respect to an AQI value of 50, as discussed above, the historical approach is to set it 

at the same level of the annual standard, if there is one. This is consistent with the current AQI 

 

3

In addition, this guidance document recommended an AQI value of 150 at 55 μg/m3, 24-hour 

average, which is in use by many State and local agencies (Harnett, 2009, Attachment B).

Comment [A1]: The last official FR notice which 

listed the AQI for PM2.5 is: Federal Register: June 

26, 2009 (Volume 74, Number 122. I believe, like 

the NAAQS, EPA should post the current AQI that 

is being used. These references are vague and 

having looked at them I landed on the last FR notice 

above. It appears the number at 100 Index level is 

not in alignment. 
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sub-index for PM2.5 and the EPA sees no basis for deviating from this approach. Thus, the EPA 

proposes to set an AQI value of 50 at 12 μg/m3, 24-hour average, the same level as the proposed 

annual PM2.5standard. If the annual standard is set at a different level, an AQI value of 50 will be 

set at the level of the annual PM2.5 standard that is promulgated. 

With respect to an AQI value of 100, there are two general approaches that could be used 

to select the associated PM2.5 level. By far the most common approach, which has been used with 

the other sub-indices as discussed above, is to set an AQI value of 100 at the same level as the 

short-term standard. The EPA recognizes that some state and local air quality agencies have 

expressed a strong preference that the Agency set an AQI value of 100 equal to any short-term 

standard. These agencies typically express the view that this linkage is useful for the purpose of 

communicating with the public about the standard, as well as the health impacts associated with 

daily air quality. 

The second approach is to directly evaluate the health effects evidence to select the level 

for an AQI value of 100 which is the basis for advisories to individuals in sensitive groups. The 

EPA is considering this alternative approach in recognition that, as proposed, the 24-hour PM2.5

standard provides supplemental protection against effects associated with short-term exposures 

of PM2.5 by working in conjunction with the annual standard to reduce 24-hour exposures to 

PM2.5. The EPA recognizes that some state and local air quality agencies have expressed support 

for this alternative approach, when the annual standard provides some protection from effects 

associated with short-term exposures. This alternative approach of evaluating the health evidence 

directly results in the consideration of a range of 35 to 30 μg/m3, 24-hour average, based on the 

discussion of the health information pertaining to the level of the 24-hour standard in section 

III.E.4 above. Setting an AQI value of 100 at the upper end of the range (35 μg/m3, 24-hour 

Comment [A2]: The use of different state-bystate AQI values is confusing to the public and leads 

to public inaction due to potentially different 

messaging about serious air quality conditions. 

Consider: Although state and local air agencies have 

used AQI values and indices that differ from EPA, in 

an emergency situation, communication to the public 

should be consistent to afford the best potential for 

public confidence and proactive response to the air 

quality conditions.

Comment [A3]: This entire section reiterates 

Section III. B above and is not needed. This led me 

and others to think that EPA is proposing two 

options for the AQI. I suggest striking the whole 

highlighted section.
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average) would place more weight on the multi-city, short-term exposure studies that generally 

support retaining the current 24-hour standard level at 35 μg/m3in conjunction with lowering the 

level of the annual standard to 12 μg/m3. Setting an AQI value of 100 at the lower end of the 

range (30 μg/m3, 24-hour average) would place more weight on the limited evidence from one 

multi-city study (Bell et al., 2008) that reported positive and statistically significant effects with 

an overall 98th percentile value below 35 μg/m3, 24-hour average, in conjunction with an overall 

long-term mean concentration slightly less than 13 μg/m3(US EPA, 2011a, p. 2-84). 

Both of these approaches result in the consideration of setting an AQI value of 100 for 

the PM2.5 sub-index within the range of 35 to 30 μg/m3, 24-hour average. In making a final 

decision on the air quality level for an AQI value of 100, the EPA will first decide on the 

approach that is appropriate, and then the level that is consistent with that approach. If the first 

approach is selected, the Agency will set the AQI value of 100 at the level of the 24-hour PM2.5

that is promulgated. If the second approach is selected, the Agency will base the decision to set 

the PM2.5 level for an AQI value of 100 by evaluating the health effects evidence. The EPA 

strongly encourages state and local air quality agencies that use the AQI to comment on both the 

approach and the level at which to set an AQI value of 100.

With respect to an AQI value of 150, this level is based upon the same health effects 

information that informs the selection of the level of the 24-hour standard and the AQI value of

100. As noted above, in guidance the EPA indicated that a 55 μg/m3, 24-hour average, PM2.5

level should be used for an AQI value of 150, in conjunction with an AQI value of 100 at 35 

μg/m3, 24-hour average (Harnett, 2009. Attachment B). In considering what level to propose for 

an AQI value of 150, we still believe that the health effects evidence indicates that the level of 55 

μg/m3, 24-hour average, is appropriate to use in conjunction with an AQI value of 100 set at 35 

Comment [A4]: Confusing, please strike.

Comment [A5]: This clearly says that EPA is 

open to two different approaches and that is for the 

AQI and NOT the NAAQS 24hr standard. Consider: 

changing section to read: The EPA proposes to set an 

AQI value of 100 at either 35 or 30 μg/m3, 24-hour 

average the same levels as the proposed short term 

PM2.5standard. If the 24-hour standard is set at a 

different level, an AQI value of 100 will be set at the 

level of the 24-hour PM2.5 standard that is 

promulgated.
Summary of Interagency Working Comments on Draft Language under 

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μg/m3. If, however, the EPA decides to set an AQI value of 100 at 30 μg/m3, using one of the 

two approaches discussed above, then the EPA would adjust an AQI value of 150 proportionally 

to the PM2.5 level of 50 μg/m3, 24-hour average. The Agency’s approach to selecting the levels at 

which to set the AQI values of 100 and 150 inherently recognizes that the epidemiological 

evidence upon which these decisions are based provides no evidence of discernible thresholds, 

below which effects do not occur in either sensitive groups or in the general population, at which 

to set these two breakpoints. Therefore, EPA concludes the use of a proportional adjustment is 

appropriate. Thus, if the EPA sets an AQI value of 100 at the PM2.5 level of 35 μg/m3, 24-hour 

average, the Agency proposes to set an AQI value of 150 at the PM2.5 level of 55 μg/m3, 24-hour 

average. However, if the EPA sets an AQI value of 100 at the PM2.5 level of 30 μg/m3, 24-hour 

average, the Agency proposes to set an AQI value of 150 at the PM2.5 level of 50 μg/m3, 24-hour 

average. 

The EPA also proposes to set an AQI value of 500 at 350 500 μg/m3, as discussed below, 

and proposes proportional revisions to the AQI breakpoints between the 150 and 500 levels. The 

proposed breakpoints are shown in Table 2 below. A review of the history of the AQI value of 

500 for PM10 and of the AQI value of 500 for PM2.5 is useful background for explaining the basis 

for maintaining proposing to set an AQI value of 500 at 500350 μg/m3, 24-hour average, for 

PM2.5. The current AQI value of 500 for PM10 was set in 1987 at the level of 600 μg/m3, 24-hour 

average, on the basis of increased mortality associated with historical wintertime pollution 

episodes in London (52 FR 24687 to 24688, July 1, 1987). Particle concentrations, dominated 

with sulfate from coal burning for heating during these episodes, measured by the British Smoke 

method, were in the range of 500 to 1000 μg/m3. In the 1987 rulemaking that established the 

upper bound index value for PM10, the EPA cited a generally held opinion that the British Smoke 

Comment [A6]: Strike as this adds to the 

confusion. 

Comment [A7]: 500

Comment [A8]: Table 2 should reflect current 

AQI and propsed with proportional steps up to Index 

500 and 500 μg/m3

Comment [A9]: Note that previously EPA cites 

that there is indication that sulfate dominated 

particulate is a pollutant with specific negative 

affects (see page 104 and the linkage of mortality 

and secondary sulfate which was a significant 

portion of the pollution in the London pollution). 

Note woodsmoke is very low in secondary sulfate 

constituency . 
Summary of Interagency Working Comments on Draft Language under 

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method measures PM with a cutpoint of approximately 4.5 microns (52 FR 24688, July 1, 1987). 

In establishing this value for PM10, we assumed that concentrations of PM10, which includes both 

coarse and fine particles, during episodes of concern, would be about 100 μg/m3higher than the 

PM concentration measured in terms of British Smoke (52 FR 24688, July 1, 1987). The upper 

bound index value of 600 μg/m3 was developed by selecting the lower end of the range of 

harmful concentrations during the historical wintertime pollution episodes in London (500 

μg/m3) and adding a margin of 100 μg/m3to account for this measurement difference. The 

current PM2.5 concentration corresponding to an AQI value of 500 is 500 μg/m3, 24-hour 

average. This was proposed in 1998 and finalized in 1999 (63 FR 67829, December 9, 1998, and 

64 FR 42530, August 4, 1999, respectively). Because there were few PM2.5 monitoring data 

available at that time, the proposal was based on the stated assumption that PM concentrations 

measured by the British Smoke method are approximately equivalent to PM2.5 concentrations. 

Table 2. Proposed Revisions to PM2.5 Sub-Index

AQI Category Index Values Proposed Breakpoints

(μg/m3, 24-hour average)

Good 0 - 50 0.0 – 12.4

Moderate 51 - 100 12.5 – (30.4 - 35.4)

Unhealthy for 

Sensitive Groups 101 - 150 (30.5 - 35.5) – (50.4 - 55.4)

Unhealthy 151 - 200 (50.5 - 55.5) - 140.4150.4

Very Unhealthy 201 - 300 140.5 - 210.4 150.5-250.4

Hazardous 301 - 400 210.5 - 280.4 250.4-350.4

401 - 500 280.5 - 350.4 350.5-500

In considering revisions to an AQI value of 500 for PM2.5, the EPA has taken note that 

the proposed and final actions in 1998 and 1999 were based on an assumption of approximate 

equivalence between the British Smoke method and the current PM2.5 method. This assumption 

is not entirely consistent with the view cited in 1987 that the British Smoke method has a cutoff 

Comment [A10]: Note, need the table to show 

current AQI for PM2.5 and the proposed changes as 

shown here. 
Summary of Interagency Working Comments on Draft Language under 

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of 4.5 microns (52 FR 24688, July 1, 1987). Because of the dramatic increase in PM2.5

monitoring data since that rulemaking, the EPA considers it appropriate to set the AQI value of 

500 for PM2.5 at a level below 500 μg/m3so that it retains is current is more consistencyt with the 

findings from the London episodes and with the AQI value of 500 for PM10. 

On average, about 60 percent of ambient PM10 measured in the northeastern, 

southeastern, and industrial midwest portions of the U.S. consists of PM2.5.

4 Using the 60 percent 

factor to scale the AQI value of 500 for PM10 (600 μg/m3) results in an AQI value of 500 for 

PM2.5 of about 350 μg/m3. The Agency believes it is appropriate that this scaling approach 

results in a PM2.5 value for the upper bound index value that is below the 500 μg/m3 

concentration of PM4.5 by the British Smoke method. The EPA therefore proposes this level for 

the upper bound level of the PM2.5 sub-index of the AQI.

The EPA has used the historical wintertime pollution episodes in London to propose 

setting an AQI value of 500 for PM2.5 as described above because it is still the best available 

information - there is little information about similar, more recent, air pollution episodes and 

associated impacts on community health upon which to base a decision. However, the limited 

number of studies cited in the Integrated Science Assessment that evaluated wood smoke health 

impacts found effects such as cardiovascular morbidity and mortality (e.g., Delfino et al., 2009; 

Mar et al., 2000; Sarnat et al., 2008) as well as respiratory effects (e.g., Barregard et al., 2008; 

Delfino et al., 2009; Schreuder et al., 2006) at much lower levels (US EPA, 2009a, sections 6.2 

and 6.6). These recent health studies provide additional qualitative support for lowering the air 

quality level associated with an AQI value of 500 to 350 μg/m3and, therefore, also lowering the 

 

4 More specifically, in 2001 to 2003, the median of the ratio of 24-hour PM2.5 and PM10 among 

monitoring sites in the northeastern, southeastern, and industrial midwest portions of the U.S to 

the annual average was between 0.60 and 0.65 (US EPA, 2005, Figure 2-19). 

Comment [A11]: This is not geographically 

representative of the US and yet the AQI is a 

national metric. A query of the EPA’s AQS shows 

high values of PM2.5 are most frequently associated 

with wildfires and are not found in some the regions 

used by EPA. 

Comment [A12]: Srike this section.

Comment [A13]: Note: This work is based on 

indoor smoke exposure, based on 13 subjects, and 

two 4 hr sessions. No follow up on long term health 

effects.
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other levels in the range of AQI values between 150 and 500. 

For the intermediate breakpoints in the AQI between the values of 150 and 500, the EPA 

proposes PM2.5 concentrations that generally reflect a linear relationship between increasing 

index values and increasing PM2.5 values (Table 2 above). The available scientific evidence of 

health effects related to population exposures to PM2.5 concentrations between the level of the 

24-hour standard and an AQI value of 500 suggest a continuum of effects in this range, with 

increasing PM2.5 concentrations being associated with increasingly larger numbers of people 

likely to experience such effects. The generally linear relationship between AQI values and 

PM2.5 concentrations in this range is consistent with the health evidence. This also is consistent 

with the Agency’s practice of setting breakpoints in symmetrical fashion where health effects 

information does not suggest particular levels. EPA is interested in alternative approaches to the 

setting of the upper levels of the AQI and if further research is available to base changes to the 

proposed values here, welcome such information.