Summary of interagency working comments on draft rule under EO 12866. 

These comments do not necessarily represent the views of OMB and are subject to further policy review.

29. To improve clarity, it would be useful to move the request for information to the 

beginning of the document and include the rest as background. 

Response: We do not understand this comment and the specific language it’s referring to. 

30. When will the Santa Monica Study be ready?

Response: The Santa Monica study conducted by the South Coast Air Quality Management 

District is completed and the draft final report is expected to be ready this Spring. The Santa 

Monica study conducted by EPA was recently finalized and is now available at: 

www/epa.gov/otaq/aviation.htm.

31. We recommend that EPA include the following questions, to help EPA collect useful 

information on how regulation of avgas may cause commercial disruptions:

 How many companies manufacture AvGas today?

 Do we have to import AvGas to meet current demand?

 How is AvGas transported to airports? (either piped into airports or by truck)

 For companies developing alternatives, what is the best estimate as to when they’d be 

able to meet current demand?

 Where does the research stand on a standard for unleaded fuel for high-performance 

engines?

 To what extent are U.S. operators of general aviation aircraft concerned that any changes 

made to U.S. avgas requirements (such as, for example, requiring manufacturers to 

produce engines that consume non-leaded fuels), could disrupt their ability to fly to/from 

locations outside the United States because of a potential lack of those non-leaded fuels?

 To what extent are U.S. manufacturers and other sellers of general aviation aircraft 

concerned that a change in U.S. avgas requirements could affect the international 

competitiveness of their products by, for example, decreasing the demand for U.S. 

aircraft overseas if they are not compatible with avgas used in those non-U.S. markets? 

Response: In consultation with industry it is understood that any near-term or long-term 

unleaded avgas or low lead would provide equivalent performance to 100LL (i.e, 

equivalent octane performance); the fuel would need to meet the ASTM specification for 

100LL. We currently ask for comment on potential problems with the approach we 

outline in this section of the ANPR. We’re willing to add another sentence requesting 

comment on avgas issues, but it will be more generally worded than what is suggested 

here, in order to be consistent with the level of detail in our other requests for comment. 

We can get you some suggested text tomorrow.

32. Page 13 line 12: It is indicated that 100LL is the most commonly available type of 

avgas but it is not clear here if this is the most commonly used. Suggest noting this 

here and not later in the paragraph as it is presented.

Response: We will add the note regarding the dominant use of 100LL where suggested. 

33. Page 14 line 6: It is noted that if all avgas was 100LL, it would account for 

approximately 34,000 tons of lead emitted to the air. Would this be double if 100 

octane only were used as indicated by the doubling of the concentration of lead in 

100 octane relative to 100LL? 
Summary of interagency working comments on draft rule under EO 12866. 

These comments do not necessarily represent the views of OMB and are subject to further policy review.

Response: Yes. 

34. Page 17 line 8: It is mentioned that EPA has discussed it “endangerment finding” 

authority at length in recent notices. It should be noted here that these 

endangerment findings are with respect to green house gases and not lead.

Response: We will add that these recent findings refer to greenhouse gases. 

35. Page 17 line 18: Concentrations of the standard are presented in text unites of 

micrograms per cubic meter but in previous and future text units are presented as 

μg/m3. We suggest notations be used consistently throughout the document.

Response: We have corrected this.

36. Page 20 line 10: It is noted that EPA has found that air pollutant emissions that 

amount to 1.2 percent of the total inventory met the statutory test for contribution. 

How does this value compare to the value for lead in avgas? (What percent of Pb in 

avgas contributes to the total inventory of Pb?)

Response: As noted in the ANPR, avgas lead contributes to 50% of the total inventory

for lead in 2005. For future actions we will be evaluating, as noted in Section VI.A.2., 

the contribution of avgas lead to areas that are designated nonattainment for lead.

37. Page 29 line 12: It is noted that particles size influences the amount of time spent in 

[insert “the”] aerosol phase. It should be noted as well this influences their 

residence time in the atmosphere. 

Response: We have made this correction. The next sentence, beginning with “In 

general, larger particles tend to deposit more quickly,.....” describes particle size as a 

factor in residence time in the atmosphere.

38. Page 30 line 6: It is noted “Once deposited to surfaces, lead can subsequently be 

resuspended into the ambient air and, because of the persistence of lead, emissions 

of this metal contribute to environmental media concentrations for many years into 

the future”. It should be added that the emissions contribute to environmental 

media concentrations for many years into the future “as it is cycled within and 

between environmental media such as soil, air, and water”. 

Response: We have added this phrase to the sentence as suggested.

39. Page 31 line 6: Insert at the end of the paragraph “as described above”.

Response: We have made this addition.

40. Page 48 top: Volume of avgas produced presented in gallons yet concentrations of 

Pb in avgas are presented in g/L. We suggest the gallon notation also be converted 

to liters here and present the concentrations in g/L as well as g/gal as noted in the 

equation in the next paragraph.

Response: We will provide this information in a footnote in this section. 
Summary of interagency working comments on draft rule under EO 12866. 

These comments do not necessarily represent the views of OMB and are subject to further policy review.

41. Page 51 last ¶: General aviation and air taxi acronyms are presented here but 

should be defined in the preceding paragraph where GA and TA are listed with no 

definition.

Response: We have corrected this. The original acronyms were provided on page 13 so 

we removed the definition of GA and AT on page 51.

42. Page 53 last ¶: What is the concentration of Pb in 100 Octane in units of g/L so that 

one may compare to the 0.56 g/L presented for 100LL in the previous sentence? 

Response: We have added the information that Pb in 100 Octane is present at a 

concentration of 1.12 g/L.

43. Page 57 line 17: typo: “an” should be “and”

Response: We have made this correction.

44. Page 62 last ¶: Particulate emissions from piston-engine aircraft are presented as 

10,000 μg/m3. It would be helpful to put this value in perspective with respect to 

ambient air TSP air quality standards (i.e., for particles less than 2.5 micron in 

diameter, the 24 hour attainment standard is 35 μg/m3).

Response: The particulate matter concentration of 10,000 μg/m3 was extrapolated from 

exhaust measurements made in the air immediately exiting the engine. These 

concentrations are not directly comparable to ambient air quality standards since the 

emissions have not undergone dilution and dispersion in the ambient air. 

45. Page 63 ¶2: “due to their “small” size”... We suggest an (i.e., typically less than one 

micron in diameter).

Response: We have added this parenthetical information.

46. Page 71 ¶1: It is noted “We are requesting comment on the availability of 

additional monitoring or modeling studies that evaluate the air quality impact of 

lead emissions from piston-engine aircraft as well as potential impacts on soil, house 

dust, surface water or other environmental media”, we suggest adding a request for 

comment on studies that will also assess potential impact on public health and 

welfare.

Response: We have added this request for comment on page 71 at the end of ¶1.

47. Page 86 top: There is a discussion of lead concentrations in fish. In an effort to put 

these numbers in perspective, fish advisory levels for lead in fish should be 

presented too.

Response: States establish advisory levels for pollutants measured in fish. We are 

intending to collecting state-specific information regarding lead advisory levels and we 

have added a request for this information on page 86.