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

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

Date: 06/12/2012 04:15 PM

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 

regarding issues related to monitoring and implementation 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.

Monitoring and Implementation

• Some commenters would like to understand whether proposed changes to the 

monitoring program (or any other changes that would not affect initial 

attainment designation) are mandated by the relevant court orders. If not 

specifically required, commenters recommend that changes to monitoring 

programs be removed from this proposed rule and be proposed separately, 

giving additional time to understand the implications of monitoring changes, the 

interplay between near-road monitoring for different pollutants, and how nearroad monitoring will affect future modeling and NAAQS standards.

• The draft NPRM appears to link the near-road monitor with the conformity 

process, which would be a substantial change in existing procedures and could 

make conformity determinations more difficult. The references to consideration 

of the near-road data for comparison to present versus future PM2.5 NAAQS are 

still not clear. It appears that EPA’s intent would be that the data would not be 

considered for the NAAQS being proposed here, but for future NAAQS. If so, 

then that concept is not clear from the language in the preamble. Understanding 

that the data would be ready for use as soon as 2018, it sounds like the nearroad data could be used for comparison to new PM2.5 24 hour NAAQS presently 

being proposed, at least. Also, to introduce a change in the conformity process 

as part of a NAAQS rulemaking is not appropriate.

• The NPRM removes the existing flexibility to determine whether specific 

receptors are appropriate for comparing to the NAAQS under transportation 

conformity, but preserves this flexibility for permitting agencies making 

decisions with respect to stationary sources. Transportation projects should be 

given the same flexibilities as stationary sources. 

• The proposed lowering of the standard will almost certainly increase the 

number of nonattainment areas that will need to comply with the transportation 

conformity process, creating an additional burden on transportation agencies 

and project sponsors.

• The commenters looking at this question had a concern about the statement that 

there was “long-standing” support for these changes. If the changes do come 

from authority from the 1997 NAAQS, then that foundation should be stated 

more clearly.

• On page 14 of 34 of the attached edited language, the discussion of the use of the 

near-road data for receptor sites on hot spot analyses has been removed, and 

more general language about how data is “valuable” for transportation 

conformity determinations has been added. Reference to the language used in 
Summary of Interagency Working Comments on Draft Language under 

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

answer to comment 22, as attached here, would be helpful in describing how the 

near-road data could be “valuable” for determining receptor sites, without 

creating the specter of requiring monitoring for hot spot analysis from the 

Friday version of the language.

• Currently, a standardized measurement methodology for PM emissions from 

aircraft engines does not exist. Since 2010, both EPA and FAA have been 

working with subject matter experts within the SAE-International E-31 

Committee to define, test, and document a standardized measurement 

methodology for non-volatile PM emissions. This technical group is 

approximately 18 months away from establishing a global Aerospace 

Recommended Practice (ARP), which would be the technical basis for 

establishing a regulation governing PM emissions from aircraft. In the absence 

of a standardized method for measuring PM emissions from aircraft engines, 

commenters find that it would be especially challenging to evaluate aviation 

actions for the proposed secondary standard, which is proposed to be based on 

visibility. There are no adequate tools for measuring or estimating PM emissions 

from aircraft; thus, it will not be possible to demonstrate compliance the new 

standards, such as in completing conformity analysis and determinations where 

needed. The current tools for surrogate emissions estimates are only available 

for commercial jet aircraft emissions, not for emissions from other aircraft 

types.

One commenter objected to the original language on page 359/360 that suggests a 

relationship between the proposed near road PM monitoring network and 

Transportation Conformity PM hot spot modeling guidance and it must be deleted. 

The sentence states “Near road PM2.5 sites would...by physically requiring 

monitoring in locations that historically were generally modeled but not 

monitored.” The revised sentence provided by EPA “Near-road PM2.5 sites would 

also make measurement data available for complex locations not routinely 

monitored currently that may be valuable for the implementation of the Agency’s 

permitting program and transportation conformity determinations” is equally 

unacceptable. Both sentences suggests a change in EPA’s current Transportation 

Conformity/CAA compliance requirements for transportation projects, insinuating a 

relationship between modeling and monitoring project impacts which is 

unsupported. Any such change will have a tremendous impact on transportation 

projects that are required to meet transportation conformity requirements and is 

inappropriate to introduce a change in this process in a NAAQS rulemaking. 

Applicability of Microscale Monitors for Comparison to Annual PM NAAQS. 

Some commenters disagree with EPA’s proposal to add language “that explicitly 
Summary of Interagency Working Comments on Draft Language under 

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

states that measuring PM2.5 in micro- and middle-scale environments near 

emissions of mobile sources, such as a highway, does not constitute being impacted 

by a “unique” source”(p. 356). It is not reasonable to assume that no highways 

would represent a unique source. PM emissions resulting from a roadway are very 

unique to the individual characteristics of that roadway, such as fleet mix, age 

distribution, level-of-service, and road geometry. Commenters do not agree with 

EPA’s rational that “Mobile sources are rather ubiquitous and, as such, there are 

many locations throughout an urban area where elevated exposures could occur.” 

As highlighted in EPA’s 2006 PM2.5 and PM10 Hot-spot Rulemaking for 

Transportation Conformity, PM emissions are particularly sensitive to diesel 

emissions (71 FR 12491-12492): 

a. EPA modeling shows emission factors for heavy-duty vehicles in the near 

term are approximately 40-50 times higher than gasoline vehicles on a 

per vehicle basis and 15-20 times higher in 2015; 

b. Studies show high level of particles in areas with high diesel activity, 

particularly areas with elevated acceleration or a large number of trucks 

operating for long periods in close proximity such as around truck routes, 

freight terminals or truck stops;

c. Study results from a major freeway in Los Angeles “demonstrate that 

gasoline vehicles do not appear to reliability create higher PM2.5 

concentrations that could create or worsen air quality violations in a 

localized area.” 

Not all highways, even those with similar levels of AADT, have the same vehicle 

activity patterns and characteristics, notably the amount of diesel vehicles. 

Commenters therefore request maintaining the current capacity for unique sites to 

be able to be determined on a case-by-case basis without adding the explicit 

provision that all highways are assumed to not be unique. Section 4.7.1(c)(1) and 

(2) of Appendix D to 40 CFR Part 58 already provides information on the 

relationship between microscale sites and representativeness. 

Applicability of Near Road Monitor to the NAAQS. Commenters do not believe, 

particularly in the case of PM, that one near road monitor can represent area-wide 

exposures. Concentrations of PM in the near road environment are dependent on 

the nature of traffic on that roadway which can vary considerably. It is additionally 

inappropriate, particularly in the case of CO and PM, to collocate monitors to 

measure maximum concentrations of both pollutants. CO is a mobile pollutant 

driven primarily by gasoline vehicles and PM is driven primarily by diesel vehicles. 

EPA has sited research in Transportation Conformity Rule Amendments showing 

clustering of CO with gasoline vehicles and NOx, PM2.5, and PM2.5-10 with diesel 
Summary of Interagency Working Comments on Draft Language under 

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

vehicles (e.g., heavy-duty diesel trucks), the positive relationship of PM2.5 mass and 

elemental carbon mass (primarily from diesel exhaust), and concentrations of PM2.5

significantly associated with diesel vehicles on nearby roadways but not with 

gasoline vehicles (71 FR 12492). 

Commenters request that EPA (a) clarify how any individual roadway is ubiquitous 

to other roadways in the nonattainment area for PM2.5 before allowing monitoring 

results from a single near road monitor near one specific roadway to be used to 

represent near road or “area-wide” conditions in a nonattainment area; and (b) 

provide information to clarify the scalability of PM2.5 monitoring results associated 

with one roadway to other roadways in the CBSA including the magnitude of 

sensitivity for a variety of variables such as AADT, fleet mix, fleet age distribution, 

road geometry, level-of-service, temporal distribution of VMT, site-specific 

meteorological conditions, and others.

Applicability of Receptors for Comparison to Annual PM NAAQS. Any changes 

in the implementation for PSD permitting and transportation conformity should be 

consistent as related to the proposed change in the applicability of receptors for 

comparison to the annual standard. EPA notes in its response to interagency 

comments that: “...if the proposed PM NAAQS revisions and monitoring regulation 

clarifications described previously are finalized, permitting agencies will continue to 

have the flexibility to qualify or disqualify specific receptor locations used in PSD air 

quality analyses consistent with those provisions.” However, for transportation 

conformity as discussed in Section G, the change “would mean that micro- and 

middle scale sites would be compared to the annual PM2.5 standard unless the 

Regional Administrator decides that the site is unique.” EPA proposes to remove the 

flexibility in the current Transportation Conformity PM hot-spot guidance for the 

interagency consultation process to determine whether receptors are appropriate 

for comparison to the NAAQS, per Section G of the NPRM. Commenters strongly 

object to this seemingly inconsistent approach and the removal of flexibility to 

transportation projects while the same flexibility will continue to be allowed for 

other permitting agencies. Inconsistencies in the application of the change in annual 

NAAQS receptor applicability should be resolved and transportation project 

sponsors should continue to have the flexibility to be able to qualify or disqualify 

specific receptor locations via the interagency consultation process.

Introduction of Secondary Standard. (a) Boundaries. As noted by EPA, 

nonattainment boundaries for areas violating the secondary standard are expected 

to overlap with the primary standard (p. 384). Commenters support this approach. 

Where the area-specific analysis supports overlapping boundaries, this overlap 
Summary of Interagency Working Comments on Draft Language under 

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

would promote the most streamlined case for areas to address transportation 

conformity requirements for the secondary standard. (b) EPA also notes that “the 

same type of emissions sources contribute to concentrations affecting attainment 

status for both the proposed primary and secondary NAAQS (p. 384). Therefore, 

commenters suggest that implementation of the standards allow for areas that are 

nonattainment for both to control for the secondary standard by meeting the 

transportation conformity requirements for the primary standard. 

Implementation of New NAAQS. In context of implementing the proposed revised 

primary annual PM2.5 NAAQS in nonattainment areas, EPA discusses potentially 

updating certain polices in the existing implementation rule (p. 394). Commenters

strongly encourage EPA to discuss the Agency’s plans on revoking the existing 

PM2.5 annual standards (15 μg/m3) or solicit comments on this matter. This 

revocation issue is especially important in the implementation of the conformity 

provisions of the CAA. The revocation issue was not applicable (and therefore was 

not included) in the implementation rule of the 1997 PM2.5 NAAQS. 

Additional Burden for Transportation due to New NAAQS. Some commenters 

express concern regarding a substantial additional burden for transportation 

practitioners due to the lowering of the standard from 15 μg/m3. (a) Areas newly 

designated for the lower standard will need to comply with the Transportation 

Conformity requirements, including integrating these requirements in to their 

transportation planning processes. For areas new to meeting transportation 

requirements, this may involve building expertise, additional resources to meet 

requirements, and additional interagency relationship building; (b)To meet projectlevel requirements, project sponsors must complete a hot-spot analysis for certain 

projects involving a large amount of diesel traffic. Current guidance on conducting 

this analysis does not allow a consideration of future background concentrations. 

Therefore, with the majority of areas expected to be well over the new standard in 

the near term, project sponsors will at a minimum need to conduct additional nobuild analyses and/or will have to mitigate project emissions according to current 

background despite the project being built in the future; and (c) additional 

uncertainty will be introduced should EPA finalize its proposed secondary standard, 

for which the transportation conformity has yet to be implemented, and if the 

Agency finalizes changes to the monitoring requirements for the PM2.5 annual 

standard related to microscale monitoring. It is unclear with a distinct secondary 

standard how nonattainment boundaries will align for the primary and secondary 

NAAQS as well as how mobile source emissions budgets will be executed 
Summary of Interagency Working Comments on Draft Language under 

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