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.

1) Could EPA better describe various options that could be considered if emissions standards 

or other remedies are considered, including incentives or other flexible mechanisms? 

Consider for example that approximately 60% of Forest Service aircraft are piston aircraft using 

leaded aviation fuel, including a several floatplanes. Many of these are firefighting aircraft that 

are critical to the protection of lives and property. A primary concern with this proposal is that 

many of the aircraft that we own or operate are so old that they no longer have a manufacturer to 

support engine modifications to meet any new standard or conversions to unleaded fuel. 

Consequently, this burden would most likely fall on the current owners, and could reduce the 

current fleet of firefighting aircraft. Hence, the Forest Service would like the EPA and FAA to 

consider alternative options or additional incentives for owners and operators to replace piston 

aircraft with turbine powered aircraft. This could result in the same benefits of reduced lead 

emissions without the research and development costs of converting piston engines to unleaded 

fuel. 

2) The exposure section should have references for all relevant statements and assertions. The 

exposure section seems to use quite a few characterizations that are not supported by referenced 

literature, such as the descriptions of land use near airports (ex: “Airports are often surrounded by 

...recreational sport facilities...”), “airports are especially attractive to young children...” and 

“programs .. provide outdoor observation facilities and picnic facilities for families..”. “Personal 

gardens, community gardens...” etc are all characterizations that are not referenced. Perhaps 

there is a background document EPA could cite?

3) In the count of schools within 1km of an airport, could EPA break out preschools, 

elementary schools, middle schools, high schools and colleges? This is relevant because 

vulnerable populations are typically very young (pre-school and elementary / grammer school).

4) Could EPA provide references to support the statement on p 11 and Section VI “The data 

described in Section VI of this ANPR indicate that lead levels in ambient air on and near 

airports servicing piston-fired aircraft are higher than lead levels in areas not directly 

influenced by a lead source”. This statement seems to characterize all airports relative to all 

other areas, and implies we have a great deal of information about lead levels and airports and 

other areas. If so, that information should be discussed more fully as it is important for the entire 

document.

5) We recommend that the language on p 14 in the “Background on Leaded Aviation 

Gasoline” section be deleted or moved, because it describes airports not Gasoline. If the 

language is necessary, perhaps move it into a section about airports? (“Over 3,000 of the 20,000 

airport facilities ... if this fuel was all 100LL, it would account for approximately 34,00 tons of 

lead emitted into the air.”)

6) The draft ANPRM should try to focus on referenced materials and published studies. For 

example, “If this fuel was all 100LL, it would account for approximately 34,00 tons of lead 

emitted into the air.” EPA has other estimates, such as NEI, to represent source contribution.

7) Is the endangerment finding based on current conditions, or possible forecasted conditions? 

EPA mentions on p 15: “As described in III.B of this ANPR, the is a slight growth in the activity 

of general aviation aircraft projected to 2025.” Also, on p 59, there is a section on Projections for 

Future Growth. Should readers infer that an endangerment finding is based on forecasted 

conditions, not current conditions, or is this statement irrelevant? 

8) If forecasts are relevant and retained in the text, forecast uncertainties should be clearly 

discussed and comment taken on forecast estimates.

9) Could EPA provide a citation on p 60 for “...prior AQCDs for Lead.”

10) What flexibility does EPA have to wait to promulgate this ANPRM until the information is 

available that EPA discusses? EPA seems to be relying on only 1 study (Santa Monica Airport)

to understand emissions of lead from piston-engine aircraft, and that study is not yet complete. 
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.

Furthermore, monitoring for airports have been proposed but is not yet finalized by EPA, and in 

fact EPA may not have finished reviewing public comments on the monitoring reconsideration.

11) Given that there is not a monitoring network at airports now, how do monitoring studies 

show “...an increase in lead levels in ambient air...” as described in the first line on p 65? Or 

should this read “higher levels at airports with piston aircraft than at airports without piston 

aircraft”?

12) Please provide information on the study design for the Santa Monica Study, for example 

why monitors were placed in certain locations, how that would help identify lead gradient, 

and why only two short time periods were adopted for the study.

13) Could EPA explain why“..analogies to gradients in ultrafine PM are relevant” (p66). PM is 

both formed from precursors (unlike lead) and emitted from motor vehicles that are typically 

restricted to roads, whereas aircraft are not restricted to roads.

14) Is the model referenced on p70 available for public review, or is it in the docket?

15) Please confirm on p70 that EPA plans to use the study of one airport to characterize that 

airport, and not to generalize to other airports which may have dramatically different 

conditions.

16) EPA might intend to say that use of leaded avgas in piston-fired aircraft is one of the larger 

sources of current emissions instead of “The continued use of lead in avgas by piston-engine 

aircraft is a significant source of lead to the environment.” On p71.

17) Does higher ambient concentration of lead result from concentrated emissions (airports) or 

from the fact that emissions occur at various altitudes? P71 (and agin on p72) reads: “Pistonengine aircraft emissions of lead occur at ground level as well as at flying altitude. Consequently, 

lead from this source is concentrated near airports but is also deposited over a large geographic 

area potentially contributing to higher ambient concentrations in many communities.”

18) Could EPA define the term “fresh emissions”. Does this mean “current emissions”, or refer to 

something else? 

19) Could EPA provide references for the background documents or analysis that supports the 

characterization of land use around airports. (for Example: “Airports are often surrounded by 

a variety of land uses including recreational sport facilities, ....”o p 72-73)

20) Could EPA explain the statement on p74: “The limited ambient lead monitoring data near 

airports presented in Section IV of this ANPR suggests that for some airports this analysis will 

underestimate the actual number of people potentially exposed to elevated levels of ambient lead 

from piston-engine powered aircraft.”

21) Could EPA provide analysis of Slow, Medium and Busy airports and the number of 

residences, schools, etc located within 1km. We suggest deciling the airports by LTO, then 

counting the residences, schools, and parks located with 1km of the airports in each decile. This 

analysis will help explain how representative are the airports in the limited studies available and 

other airports in the US.

22) Could EPA provide more information on which airports are located very close to 

community gardens or other crop production sites.

23) The Section “Bioaccumulation of Lead” should clarify that it refers only to the 

environment, not to human tissue.

24) Please consider replacing the phrase “EPA is concerned about” with “EPA requests 

comment on”.

25) When will the Santa Monica study be available?

26) Has monitoring begun at airports listed on p95?

27) On p96, please clarify which information will be available in 2010 and which will be 

available in 2011 or later.

28) Please describe the limitations and uncertainties associated with the modeling EPA outlines 

on p98.