Summary of Interagency Working Comments Submitted during EO12866 Review 

Subject to Further Policy Review

1. The title of the NPRM should be changed to better reflect what is covered in the NPRM.

A more comprehensive title would be, “National Ambient Air Quality Standards for 

Carbon Monoxide and Changes to Ambient Air Monitoring Requirements” 

2. Reporting of in-vehicle CO exposure, as well as exposure from indoor sources (pgs. 18 

and 21) are not consistent with establishment of ambient air quality standard. Should 

this be discussed and evaluate in establishment of a separate indoor standard? Similar 

comments were submitted on the NO2 standard rulemaking.

3. Some acronyms are not defined the first time they were used – e.g. the acronym ‘NCEA’ 

on page 12, (we believe it is National Council for Environmental Assessment) and on 

page 109, the acronym ‘RF’ (we believe it is Radiative Forcing) . Please provide 

definitions.

4. Throughout the preamble, the term “elevated CO concentration” was used numerous 

times, especially in the discussion of near-roadway concentration. However, the 

meaning of “elevation” but was never defined. What is the level of elevation? Elevated 

as compared to the concentrations trend which is way below the standard according 

EPA’s data (see http://www.epa.gov/air/airtrends/carbon.html) Or elevated to above 

the standard? If it is the former, is there evidence that the CO concentrations is 

trending upwards to violating the standards that prompted EPA to introduce (or reintroduce?) near roadway monitoring requirements for CO?

5. Throughout the preamble, it says that the 8-hour standard is the controlling standard 

and footnote 38 on page 57 even goes so far as to say that meeting the 8-hour standard 

results in 1-hour maximum concentrations well below the corresponding 1-hour 

standard. If this is true, then why is it necessary to keep the 1-hour standard? Also, 

statements on pages 18 and 19, “, all areas of the US meet both CO NAAQS. As of 

September 27, 2010, there are no areas designated as nonattainment for the CO 

NAAQS.” and “At the set of sites across the US that have been continuously monitored 

since 1990 the average second highest 8-hour and 1-hour concentrations have declined 

by nearly 70%” It is not clear to us why standards are being retained.

6. What is the basis for resolution of differences in position between CASAC and Public 

Assessment on establishment of a lower standard (pgs. 65 and 97).

7. Unreferenced acronym ‘RF’ on page 109. Believe it is Radiative Forcing. Need 

definition.

8. EPA explains that all areas of the country are believed to be in attainment with the 

existing standard proposed for retention in this review. It is implied, then, that there is 

no benefit associated with changes to the monitoring network. Please clarify whether 

EPA believes that changes to the monitoring network are required in order to identify 
Summary of Interagency Working Comments Submitted during EO12866 Review 

Subject to Further Policy Review

areas of non-attainment, and provide for public comment any analysis that suggests 

that non-attainment may occur, and the location of the non-attainment. 

9. Section IV ‘Proposed Amendments to Ambient Monitoring Requirements’ contains a 

lengthy discussion describing a substantial increase in the number, site placements and 

sensitivity of a new generation of CO monitors able to detect increasingly lower levels of 

the pollutant. For increased precision EPA is also proposing to change the form of the 

precision limit specifications from an absolute measure (ppm) to (percent ) of the upper 

range limit for CO analyzers. Considering that all indications are that the NAAQS for 

both the 8-hour and the 1-hour concentrations have been met, this seems to be a 

tremendously unwarranted expenditure of resources and manpower.

10. The language on pages 117-119 is unclear regarding whether or not the new CO FRM or 

FEM analyzer performance requirements would apply only to newly designated 

analyzers or also existing analyzers. The language seems to say while almost all current 

analyzers are meeting the new requirements, EPA may determine that some existing 

analyzers do not and would need to be changed. If no re-testing or re-designation is 

being proposed, how does EPA plan to determine if existing analyzers need to be 

changed?

11. Page 123 provided data that on-road mobile sources is now “approximate 60% of total 

CO emissions inventory.” But the paragraph did not mention that total CO emissions 

has been declining, so even though 60% seems to be a high number, the actual 

emissions coming from on-road mobile source has been declining in the past 20 years 

and the CO concentration has also been in a declining trend in the past 30 years (see 

EPA’s national trends for CO emissions 

http://cfpub.epa.gov/eroe/index.cfm?fuseaction=detail.viewMidImg&lShowInd=0&subt

op=341&lv=list.listByAlpha&r=219652#11452 and CO concentration 

http://www.epa.gov/air/airtrends/carbon.html) We believe EPA should include this 

information to present a more accurate picture of CO emissions.

12. Page 124 and 125 in the “Near-road environment” section and later in the section 

“monitoring for CO at required near-road NO2 monitoring stations” starting on p.130, 

we shared the concerns raised during the interagency conference call – that EPA should

articulate in a clearer way why the near-roadway monitoring requirements for NO2 

apply for CO.

13. P.131 EPA should clarify whether the housing units numbered include those that live 

near airports and railroads. 

14. On page 131, in the paragraph that starts on this page, how does including the 2008 

American Time Use Survey about in-vehicle microenvironments support the need for 
Summary of Interagency Working Comments Submitted during EO12866 Review 

Subject to Further Policy Review

near road monitoring since those monitors will not be able to capture in-vehicle 

conditions? This fact would be better placed in the discussion regarding other sources 

of CO not captured in the monitoring network.

15. Again on p.131 – EPA seems to be concerned about the CO exposure for a large portion 

of the population but did not discuss whether the “higher” concentration near roadways

are expected to be above the CO standards. Because there have been no violations of 

the applicable standards since the 1990s, it is not apparent that there would be health 

risk and exposure issues.

16. On pages 132-133, how was 1,000,000 or more persons chosen as the threshold for 

CBSAs where CO near-road monitors would be placed? This number is different than 

the thresholds established for NO2 and the CO preamble only says that 1,000,000 is a 

reasonable approach without giving any further explanation.

17. As EPA notes in the NPRM, no CO violations have occurred for many years, and three 

are no U.S. nonattainment areas. The CO reductions through improved technology 

are an environmental and health success story. It is appropriate that EPA does not 

propose any change to the national ambient air quality standard for CO.