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. 

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?

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).

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. 

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.”)

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.

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?  

If forecasts are relevant and retained in the text, forecast
uncertainties should be clearly discussed and comment taken on forecast
estimates.

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

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.
 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.

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”?

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.

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.

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

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.

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.

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: “Piston-engine 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.”

Could EPA define the term “fresh emissions”.  Does this mean
“current emissions”, or refer to something else? 

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)

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.”

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.

Could EPA provide more information on which airports are located very
close to community gardens or other crop production sites.

The Section “Bioaccumulation of Lead” should clarify that it refers
only to the environment, not to human tissue.

Please consider replacing the phrase “EPA is concerned about” with
“EPA requests comment on”.

When will the Santa Monica study be available?

Has monitoring begun at airports listed on p95?

On p96, please clarify which information will be available in 2010 and
which will be available in 2011 or later.

Please describe the limitations and uncertainties associated with the
modeling EPA outlines on p98.

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.

