secondary PM that is formed from chemical reactions in the atmosphere.
The issue of secondary organic aerosol formation from aromatic
precursors is an important one to which EPA and others are paying
significant attention. This is discussed in more detail in Section
1.4.1 of the RIA.

F. Near-Roadway Health Effects

    Over the years there have been a large number of studies that have
examined associations between living near major roads and different
adverse health endpoints. These studies generally examine people living
near heavily-trafficked roadways, typically within several hundred
meters, where fresh emissions from motor vehicles are not yet fully
diluted with background air.
    Several studies have measured elevated concentrations of pollutants
emitted directly by motor vehicles near road as compared to overall
urban background levels. These elevated concentrations generally occur
within approximately 200 meters of the road, although the distance may
vary depending on traffic and environmental conditions. Pollutants
measured with elevated concentrations include benzene, polycyclic
aromatic hydrocarbons, carbon monoxide, nitrogen dioxide, black carbon,
and coarse, fine, and ultrafine particulate matter. In addition,
concentrations of road dust, and wear particles from tire and brake use
also show concentration increases in proximity of major roadways.
    The near-roadway health studies provide stronger evidence for some
health endpoints than others. Evidence of adverse responses to traffic-
related pollution is strongest for non-allergic respiratory symptoms,
cardiovascular effects, premature adult mortality, and adverse birth
outcomes, including low birth weight and size. Some evidence for new
onset asthma is available, but not all studies have significant
orrelations. Lastly, among studies of childhood cancer, in particular
childhood leukemia, evidence is inconsistent. Several small studies
report positive associations, though such effects have not been
observed in two larger studies. As described above, benzene and 1,3-
butadiene are both known human leukemogens in adults. As previously
mentioned, there is evidence of increased risk of leukemia among
children whose parents have been occupationally exposed to benzene.
Though the near-roadway studies are equivocal, taken together with the
laboratory studies and other exposure environments, the data suggest a
potentially serious children's health concern could exist. Additional
research is needed to determine the significance of this potential
concern.
    Significant scientific uncertainties remain in our understanding of
the relationship between adverse health effects and near-road exposure,
including the exposures of greatest concern, the importance of chronic
versus acute exposures, the role of fuel type (e.g. diesel or gasoline)
and composition (e.g., % aromatics), relevant traffic patterns, the
role of co-stressors including noise and socioeconomic status, and the
role of differential susceptibility within the ``exposed'' populations.
For a more detailed discussion, see Chapter 3 of the Regulatory Impact
Analysis.
    These studies provide qualitative evidence that reducing emissions
from on-road mobile sources will provide public health benefits beyond
those that can be quantified using currently available information.

G. How Would This Proposal Reduce Emissions of MSATs?

    The benzene and hydrocarbon standards proposed in this action would
reduce benzene, 1,3-butadiene, formaldehyde, acrolein, polycyclic
organic matter, and naphthalene, as well as many other hydrocarbon
compounds that are emitted by motor vehicles, including those that are
listed in Table III.B-1 and discussed in more detail in Chapter 1 of
the RIA. The emission reductions expected from today's controls are
reported in section V.E of this preamble and Chapter 2 of the RIA.
    EPA believes that the emission reductions from the standards
proposed today for motor vehicles and their fuels, combined with the
standards currently in place, represent the maximum achievable
reductions of emissions from motor vehicles through the application of
technology that will be available, considering costs and the other
factors listed in section 202(l)(2). This conclusion applies whether
you consider just the compounds listed in Table III.B-1, or consider
all of the compounds on the Master List of emissions, given the breadth
of EPA's current and proposed control programs and the broad groups of
emissions that many of the control technologies reduce.
    EPA has already taken significant steps to reduce diesel emissions
from mobile sources. We have adopted stringent standards for on-highway
diesel trucks and buses, and nonroad diesel engines (engines used, for
example, in construction, agricultural, and industrial applications).
We also have additional programs underway to reduce diesel emissions,
including voluntary programs and a proposal that is being developed to
reduce emissions from diesel locomotives and marine engines.
    Emissions from motor vehicles can be chemically categorized as
hydrocarbons, trace elements (including metals) and a

few additional compounds containing carbon, nitrogen and/or halogens
(e.g., chlorine). For the hydrocarbons, which are the vast majority of
these compounds, we believe that with the controls proposed today, we
would control the emissions of these compounds from motor vehicles to
the maximum amount currently feasible or currently identifiable with
available information. Section VI of this preamble provides more
details about why the proposed and existing standards represent maximum
achievable reduction of hydrocarbons from motor vehicles. There are not
motor vehicle controls to reduce individual hydrocarbons selectively;
instead, the maximum emission reductions are achieved by controls on
hydrocarbons as a group. There are fuel controls that could selectively
reduce individual air toxics (e.g., formaldehyde, acetaldehyde, 1,3-
butadiene), as well as controls that reduce hydrocarbons more
generally. Section VII of this preamble describes why the standards we
are proposing today represent the maximum emission reductions
achievable through fuel controls, considering the factors required by
Clean Air Act section 202(l).
    Motor vehicle emissions also contain trace elements, including
metals, which originate primarily from engine wear and impurities in
engine oil and gasoline or diesel fuel. EPA does not have authority to
regulate engine oil, and there are no feasible motor vehicle controls
to directly prevent engine wear. Nevertheless, oil consumption and
engine wear have decreased over the years, decreasing emission of
metals from these sources. Metals associated with particulate matter
will be captured in emission control systems employing a particulate
matter trap, such as heavy-duty vehicles meeting the 2007 standards. We
believe that currently, particulate matter traps, in combination with
engine-out control, represent the maximum feasible reduction of both
motor vehicle particulate matter and toxic metals present as a
component of the particulate matter.
    The mobile source contribution to the national inventory for metal
compounds is generally small. In fact, the emission rate for most
metals from motor vehicles is small enough that quantitative
measurement requires state-of-the art analytical techniques that are
only recently being applied to this source category. We have efforts
underway to gather information regarding trace metal emissions,
including mercury emissions, from motor vehicles (see Chapter 1 of the
RIA for more details).
    A few metals and other elements are used as fuel additives. These
additives are designed to reduce the emission of regulated pollutants
either in combination with or without an emission control device (e.g.,
a passive particulate matter trap). Clean Air Act section 211 provides
EPA with various authorities to regulate fuel additives in order to
reduce the risk to public health from exposure to their emissions. It
is under this section that EPA requires manufacturers to register
additives before their introduction into commerce. Registration
involves certain data requirements that enable EPA to identify products
whose emissions may pose an unreasonable risk to public health. In
addition, section 211 provides EPA with authority to require health
effects testing to fill any gaps in the data that would prevent a
determination regarding the potential for risk to the public. Clean Air
Act section 211(c) provides the primary mechanism by which EPA would
take actions necessary to minimize exposure to metals or other
additives to diesel and gasoline. It is under section 211 that EPA is
currently generating the information needed to update an assessment of
the potential human health risks related to having manganese in the
national fuel supply.
    Existing regulations limit sulfur in gasoline and diesel fuel to
the maximum amount feasible and will reduce emissions of all sulfur-
containing compounds (e.g., hydrogen sulfide, carbon disulfide) to the
greatest degree achievable.84 85 86 For the remaining
compounds (e.g., chlorinated compounds), we currently have very little
information regarding emission rates and conditions that impact
emissions. This information would be necessary in order to evaluate
potential controls under section 202(l). Emissions of hydrocarbons
containing chlorine (e.g., dioxins/furans) would likely be reduced with
control measures that reduce total hydrocarbons, just as these
emissions were reduced with the use of catalytic controls that lowered
exhaust hydrocarbons.
---------------------------------------------------------------------------

    \84\ 65 FR 6697, February 10, 2000.
    \85\ 66 FR 5001, January 18, 2001.
    \86\ 69 FR 38958, June 29, 2004.
---------------------------------------------------------------------------

IV. What Are the Air Quality and Health Impacts of Air Toxics, and How
Do Mobile Sources Contribute?

A. What Is the Health Risk to the U.S. Population from Inhalation
Exposure to Ambient Sources of Air Toxics, and How Would It be Reduced
by the Proposed Controls?

    EPA's National-Scale Air Toxics Assessment (NATA) assesses human
health impacts from chronic inhalation exposures to outdoor sources of
air toxics. It assesses lifetime risks assuming continuous exposure to
levels of air toxics estimated for a particular point in time. The most
recent NATA was done for the year 1999.\87\
---------------------------------------------------------------------------

    \87\ http://www.epa.gov/ttn/atw/nata1999.

---------------------------------------------------------------------------

    The NATA modeling framework has a number of limitations, but it
remains very useful in identifying air toxic pollutants and sources of
greatest concern. Among the significant limitations of the framework,
which are discussed in more detail in the regulatory impact analysis,
is that it cannot be used to reliably identify ``hot spots,'' such as
areas in immediate proximity to major roads, where the air
concentration, exposure and/or risk might be significantly higher
within a census tract \88\ or county. These ``hot spots'' are discussed
in more detail in section IV.B.2. The framework also does not account
for risk from sources of air toxics originating indoors, such as
stoves, out-gassing from building materials, or evaporative benzene
emissions from cars in attached garages. There are also limitations
associated with the dose-response values used to quantify risk; these
are discussed in Section I of the preamble. Importantly, it should be
noted that the 1999 NATA does not include default adjustments for early
life exposures recently recommended in the Supplemental Guidance for
Assessing Susceptibility from Early-Life Exposure to Carcinogens.\89\
These adjustments would be applied to compounds which act through a
mutagenic mode of action. EPA will determine as part of the IRIS
assessment process which substances meet the criteria for making
adjustments, and future assessments will reflect them. If warranted,
incorporation of such adjustments would lead to higher estimates of
risk assuming constant lifetime exposure.
---------------------------------------------------------------------------

    \88\ A census tract is a subdivision of a county that typically
contains roughly 4000 people. In urban areas, these tracts can be
very small, on the order of a city block, whereas in rural areas,
they can be large.
    \89\ U. S. EPA. (2005) Supplemental Guidance for Assessing
Susceptibility from Early-Life Exposure to Carcinogens. Report No.
EPA/630/R-03/003F. Available electronically at http://cfpub.epa.gov/ncea/cfm/recordisplay.cfm?deid=116283
.

---------------------------------------------------------------------------

    Because of its limitations, EPA notes that the NATA assessment
should not be used as the basis for developing risk reduction plans or
regulations to control specific sources or pollutants. Additionally,
this assessment should not be used for estimating risk at the local
level, for quantifying benefits of reduced air toxic emissions, or for
identifying localized hotspots. In this

rule, we have evaluated air quality, exposure, and risk impacts of
mobile source air toxics using the 1999 NATA, as well as projections of
risk to future years using the same tools as 1999 NATA. In addition, we
also evaluate more refined local scale modeling, measured ambient
concentrations, personal exposure measurements, and other data. This
information is discussed below, as well as in Chapter 3 of the RIA. It
serves as a perspective on the possible risk-related implications of
the rule.
    Overall, the average nationwide lifetime population cancer risk in
1999 NATA was 42 in a million, assuming continuous exposure to 1999
levels. The average noncancer respiratory hazard index was 6.4.\90\
Highway vehicles and nonroad equipment account for almost 50% of the
average population cancer risk, and 74% of the noncancer risk These
estimates are based on the contribution of sources within 50 kilometers
of a given emission point and do not include the contribution to
ambient concentrations from transport beyond 50 kilometers. Ambient
concentrations from transport beyond 50 kilometers, referred to as
``background'' in NATA, are responsible for almost 50% of the average
cancer risk in NATA.
---------------------------------------------------------------------------

    \90\ A hazard index above 1 indicates the potential for adverse
health effects. It cannot be translated into a probability that an
adverse effect will occur, and is not likely to be proportional to
risk. A hazard index greater than one can be best described as only
indicating that a potential may exist for adverse health effects.
---------------------------------------------------------------------------

    Section III.C.1 discusses the pollutants that the 1999 National-
Scale Air Toxics Assessment identifies as national and regional risk
drivers. As summarized in Table III.C-1, benzene is the only pollutant
described as a national cancer risk driver. Twenty-four percent of the
total cancer risk in the 1999 National-Scale Air Toxics Assessment was
due to benzene. In 1999, 68% of nationwide benzene emissions were
attributable to mobile sources. 1,3-Butadiene and naphthalene are
regional cancer risk drivers that have a large mobile source
contribution. As presented in Table III.C-2, 58% of nationwide 1,3-
butadiene emissions in 1999 came from mobile sources. Twenty-seven
percent of nationwide naphthalene emissions in 1999 came from mobile
sources.
    One compound, acrolein, was identified as a national risk driver
for noncancer health effects, and 25% of primary acrolein emissions
were attributable to mobile sources. Over 70% of the average ambient
concentration of acrolein is attributable to mobile sources. This is
due to the large contribution from mobile source 1,3-butadiene, which
is transformed to acrolein in the atmosphere.
    Table III.C-2 provides additional information on the mobile source
contribution to emissions of national and regional risk drivers. The
standards proposed in this rule will reduce emissions of all these
pollutants.
    In addition to the 1999 NATA, we have estimated future-year risks
for those pollutants included in the 1999 NATA whose emissions
inventories include a mobile source contribution (see Table IV.B-1).
This analysis indicates that cancer and noncancer risk will continue to
be a public health concern due to exposure to mobile-source-related
pollutants.
    Figure IV.A-1 summarizes changes in average population inhalation
cancer risk for the MSATs in Table IV.A-1. Despite significant
reductions in risk from these pollutants, average inhalation cancer
risks are expected to remain well above 1 in 100,000. In addition,
because of population growth (using projected populations from the U.S.
Bureau of Census), the number of Americans above the 1 in 100,000
cancer risk level from exposure to these mobile source air toxics is
projected to increase from about 214 million in 1999 to 240 million in
2030. Benzene continues to account for a large fraction of the total
inhalation cancer risk from mobile source air toxics, decreasing
slightly from 45% of the risk in 1999 to 37% in 2030. Similarly,
although the average noncancer respiratory hazard index for MSATs
decreases from over 6 in 1999 to 3.2 in 2030, the population with a
hazard index above one increases from 250 million in 1999 to 273
million in 2030. That is, in 2030 nearly the entire U.S. population
will still be exposed to levels of these pollutants that have the
potential to cause adverse respiratory health effects (other than
cancer).
    These projected risks were estimated using the same tools and
methods as the 1999 NATA, but with future-year projected inventories.
More detailed information on the methods used to do these projections,
and associated limitations and uncertainties, can be found in Chapter 3
of the RIA for this rule. Projected risks assumed 1999 ``background''
levels. For MSATs, ``background'' accounts for slightly less than 20%
of the average cancer risk in 1999, increasing to 24% in 2030. However,
background levels should decrease along with emissions. A sensitivity
analysis of this assumption is presented in Chapter 3 of the RIA. It
should also be noted that the projected inventories used for this
modeling do not include some more recent revisions, such as higher
emissions of hydrocarbons, including gaseous air toxics, at cold
temperatures. These revisions are discussed in section V and increase
the overall magnitude of the inventory.

[GRAPHIC] [TIFF OMITTED] TP29MR06.000

Table IV.A-1.--Pollutants Included in Risk Modeling for Projection Years
                                    *
------------------------------------------------------------------------

------------------------------------------------------------------------
1,3-Butadiene.............................  Ethyl Benzene
2,2,4-Trimethylpentane....................  Fluoranthene **
Acenaphthene **...........................  Fluorene **
Acenaphthylene **.........................  Formaldehyde
Acetaldehyde..............................  Hexane
Acrolein..................................  Indeno(1,2,3,c,d)-pyrene **
Anthracene **.............................  Manganese
Benzene...................................  Methyl tert-butyl ether
                                             (MTBE)
Benz(a)anthracene **......................  Naphthalene
Benzo(a)pyrene **.........................  Nickel
Benzo(b)fluoranthene **...................  Phenanthrene **
Benzo(g,h,i)perylene **...................  Propionaldehyde
Benzo(k)fluoranthene **...................  Pyrene **
Chromium (includes Chromium III, Chromium   Styrene
 VI, and non-speciated Chromium).
Chrysene **...............................  Toluene
Dibenzo(a,h)anthracene **.................  Xylenes
------------------------------------------------------------------------
* This list includes compounds from the 1999 National-Scale Air Toxics
  Assessment with a mobile source emissions contribution, for which data
  were sufficient to develop an emissions inventory.
** POM compound as discussed in Section III.

B. What Is the Distribution of Exposure and Risk?

1. Distribution of National-Scale Estimates of Risk From Air Toxics
    National-scale modeling indicates that 95th percentile average
cancer risk from exposure to mobile source air toxics is more than
three times higher than median risk. In addition, the 95th percentile
cancer risk is more than 10 times higher than the 5th percentile risk.
This is true for all years modeled, from 1999 to 2030. Table IV.B-1
gives the median and 5th and 95th percentile cancer risk distributions
for mobile source air toxics. As previously mentioned, the tools used
in this assessment are inadequate for identifying ``hot spots'' and do
not account for significant sources of inhalation exposure, such as
benzene emissions within attached garages from vehicles, equipment, and
portable fuel containers. If these hot spots and additional sources of
exposure were accounted for, a larger percentage of the population
would be exposed to higher risk levels. (Sections IV.B.2-4 provides
more details on ``hot spots'' and the implications for distribution of
risk.) In addition, the modeling underestimates the contribution of
hydrocarbon and particulate matter emissions at cold temperatures.
These modeling results are discussed in more detail in Chapter 3 of the
RIA.

 Table IV.B--1.--Median and 5th and 95th Percentile Lifetime Inhalation Cancer Risk Distributions for Inhalation
                             Exposure to Outdoor Sources of Mobile Source Air Toxics
                                  [Based on modeled average census tract risks]
----------------------------------------------------------------------------------------------------------------
                                                         1999                                2020
                Pollutant                -----------------------------------------------------------------------
                                              5th       Median       95th         5th       Median       95th
----------------------------------------------------------------------------------------------------------------
All MSATs...............................    4.0x10-6    1.9x10-5    5.9x10-5    3.6x10-6    1.3x10-5    4.4x10-5
Benzene.................................    2.4x10-6    8.9x10-6    2.5x10-5    2.1x10-6    5.6x10-6    1.4x10-5
1,3-Butadiene...........................    1.6x10-7    3.1x10-6    1.2x10-5    7.5x10-8    2.0x10-6    7.5x10-6
Acetaldehyde............................    1.0x10-6    2.5x10-6    6.9x10-6    9.3x10-7    1.6x10-6    3.6x10-6
Naphthalene.............................    1.1x10-7    1.4x10-6    7.6x10-6    1.0x10-7    1.4x10-6    8.5x10-6
----------------------------------------------------------------------------------------------------------------

2. Elevated Concentrations and Exposure in Mobile Source-Impacted Areas
    Air quality measurements near roads often identify elevated
concentrations of air toxic pollutants at these locations. The
concentrations of air toxic pollutants near heavily trafficked roads,
as well as the pollutant composition and characteristics, differ from
those measured distant from heavily trafficked roads. Exposures for
populations residing, working, or going to school near major roads are
likely higher than for other populations. The vehicle and fuel
standards proposed in this rule will reduce those elevated exposures.
Following is an overview of concentrations of air toxics and exposure
to air toxics in areas heavily impacted by mobile source emissions.
a. Concentrations Near Major Roadways
    The 1999 NATA estimates average concentrations within a census
tract, but it does not differentiate between locations near roadways
and those further away (within the same tract). Local-scale modeling
can better characterize distributions of concentrations, using more
refined allocation of highway vehicle emissions. Urban-scale
assessments done in Houston, TX and Portland, OR illustrated steep
gradients of air toxic concentrations along major roadways, as well as
better agreement with monitor data.91-92 93 Results of the
Portland study show average concentrations of motor vehicle-related
pollutants are ten times higher at 50 meters from a road than they are
at greater than 400 meters a road. These findings are consistent with
pollutant dispersion theory, which predicts that pollutants emitted
along roadways will show highest concentrations nearest a road, and
concentrations exponentially decrease with increasing distance
downwind. These near-road pollutant gradients have been confirmed by
measurements of both criteria pollutants and air toxics, and they are
discussed in detail in Chapter 3 of the RIA.
---------------------------------------------------------------------------

    \91-92\ Kinnee, E.J.; Touma, J.S.; Mason, R.; Thurman, J.;
Beidler, A., Bailey, C.; Cook, R. (2004) Allocation of onroad mobile
emissions to road segments for air toxics modeling in an urban area.
Transport. Res. Part D 9: 139-150.
    \93\ Cohen, J.; Cook, R.; Bailey, C.R.; Carr, E. (2005)
Relationship between motor vehicle emissions of hazardous
pollutants, roadway proximity, and ambient concentrations in
Portland, Oregon. Environ. Modelling & Software 20: 7-12.
---------------------------------------------------------------------------

    Air quality monitoring is another means of evaluating pollutant
concentrations at locations near sources such as roadways. It is also
used to evaluate model performance at a given point and, given adequate
data quality, can be statistically analyzed to determine associations
with different source types. EPA has been deploying fixed-site ambient
monitors that monitor concentrations of multiple air toxics, including
benzene, over time. Several studies have found that concentrations of
benzene and other mobile source air toxics are significantly elevated
near busy roads compared to ``urban background'' concentrations
measured at a fixed site. These studies are discussed in detail in
Chapter 3 of the RIA.
    Ambient VOC concentrations were measured around residences in
Elizabeth, NJ, as part of the Relationship among Indoor, Outdoor, and
Personal Air (RIOPA) study. Data from that study was analyzed to assess
how concentrations are influenced by proximity to known ambient
emission sources.94 95 The ambient concentrations of
benzene, toluene, ethylbenzene, and xylene isomers (BTEX) were found to
be inversely associated with distances to interstate highways and major
urban roads, and with distance to gasoline stations. The data indicate
that BTEX concentrations around homes within 200 meters of roadways and
gas stations are 1.5 to 4 times higher than urban background levels.
---------------------------------------------------------------------------

    \94\ Kwon, J. (2005) Development of a RIOPA database and
evaluation of the effect of proximity on the potential residential
exposure to VOCs from ambient sources. Rutgers, the State University
of New Jersey and University of Medicine and Dentistry of New
Jersey. PhD dissertation. This document is available in Docket EPA-
HQ-OAR-2005-0036.
    \95\ Weisel, C.P. (2004) Assessment of the contribution to
personal exposures of air toxics from mobile sources. Final report.
Submitted to EPA Office of Transportation and Air Quality.
Environmental & Occupational Health Sciences Institute, Piscataway,
NJ. This document is available in Docket EPA-HQ-OAR-2005-0036.
---------------------------------------------------------------------------

b. Exposures Near Major Roadways
    The modeling assessments and air quality monitoring studies
discussed above have increased our understanding of ambient
concentrations of mobile source air toxics and potential population
exposures. Results from the following exposure studies reveal that
populations spending time near major roadways likely experience
elevated personal exposures to motor vehicle related pollutants. In
addition, these populations may experience exposures to differing
physical and chemical compositions of certain air toxic pollutants
depending on the amount of time spent in close proximity to motor
vehicle emissions. Following is a detailed discussion on exposed
populations near major roadways.
i. Vehicles
    Several studies suggest that significant exposures may be
experienced while driving in vehicles. A recent in-vehicle monitoring
study was conducted by EPA and consisted of in-vehicle air sampling
throughout work shifts within ten police patrol cars used by the North
Carolina State Highway Patrol (smoking not permitted inside the
vehicles).\96\ Troopers operated their vehicles in typical patterns,
including highway and city driving and refueling. In-vehicle benzene
concentrations averaged 12.8 [mu]g/m3, while concentrations
measured at an ``ambient'' site located outside a nearby state
environmental office averaged 0.32 [mu]g/m3. The study also
found that the benzene concentrations were closely

associated with other fuel-related VOCs measured.
---------------------------------------------------------------------------

    \96\ Riediker, M.; Williams, R.; Devlin, R.; et al. (2003)
Exposure to particulate matter, volatile organic compounds, and
other air pollutants inside patrol cars. Environ Sci. Technol. 37:
2084-2093.
---------------------------------------------------------------------------

    In Boston, the exposure of commuters to VOCs during various
commuting modes was examined.\97\ For commuters driving a car, the mean
time-weighted concentrations of benzene, toluene, and xylenes in-
vehicle were measured at 17.0, 33.1, and 28.2 [mu]g/m3,
respectively.
---------------------------------------------------------------------------

    \97\ Chan C.-C., Spengler J. D., Ozkaynak H., and Lefkopoulou M.
(1991) Commuter Exposures to VOCs in Boston, Massachusetts. J. Air
Waste Manage. Assoc. 41: 1594-1600.
---------------------------------------------------------------------------

    The American Petroleum Institute funded a screening study of high-
end exposure microenvironments as required by section 211(b) of the
Clean Air Act.\98\ The study included vehicle chase measurements and
measurements in several vehicle-related microenvironments in several
cities for benzene and other air toxics. In-vehicle microenvironments
(average benzene concentrations in parentheses) included the vehicle
cabin tested on congested freeways (17.5 [mu]g/m\3\), in parking
garages above-ground (155 [mu]g/m\3\) and below-ground (61.7 [mu]g/
m\3\), in urban street canyons (7.54 [mu]g/m\3\), and during refueling
(46.0 [mu]g/m\3\).
---------------------------------------------------------------------------

    \98\ Zielinska, B.; Fujita, E.M.; Sagebiel, J.C.; et al. (2002)
Interim data report for Section 211(B) Tier 2 high end exposure
screening study of baseline and oxygenated gasoline. Prepared for
American Petroleum Institute. November 19, 2002. This document is
available in Docket EPA-HQ-OAR-2005-0036.
---------------------------------------------------------------------------

    In 1998, the California Air Resources Board published an extensive
study of concentrations of in-vehicle air toxics in Los Angeles and
Sacramento, CA.\99\ The data set is large and included a variety of
sampling conditions. On urban freeways, benzene in-vehicle
concentrations ranged from 3 to 15 [mu]g/m\3\ in Sacramento and 10 to
22 [mu]g/m\3\ in Los Angeles. In comparison, ambient benzene
concentrations ranged from 1 to 3 [mu]g/m\3\ in Sacramento and 3 to 7
[mu]g/m\3\ in Los Angeles.
---------------------------------------------------------------------------

    \99\ Rodes, C.; Sheldon, L.; Whitaker, D.; et al. (1998)
Measuring concentrations of selected air pollutants inside
California vehicles. Final report to California Air Resources Board.
Contract No. 95-339.
---------------------------------------------------------------------------

    Similar findings of elevated concentrations of pollutants have also
been found in studies done in diesel buses.100 101 102
---------------------------------------------------------------------------

    \100\ Fitz, D.R.; Winer, A.M.; Colome, S.; et al. (2003)
Characterizing the Range of Children's Pollutant Exposure During
School Bus Commutes. Prepared for the California Resources Board.
    \101\ Sabin, L.D.; Behrentz, E.; Winer, A.M.; et al. (2005)
Characterizing the range of children's air pollutant exposure during
school bus commutes. J. Expos. Anal. Environ. Epidemiol. 15: 377-
387.
    \102\ Batterman, S.A.; Peng, C.Y.; and Braun, J. (2002) Levels
and composition of volatile organic compounds on commuting routes in
Detroit, Michigan. Atmos. Environ. 36: 6015-6030.
---------------------------------------------------------------------------

    Overall, these studies show that concentrations experienced by
commuters and other roadway users are substantially higher than those
measured in typical urban air. As a result, the time a person spends in
a vehicle will significantly affect their overall exposure.
ii. Homes and Schools
    The proximity of schools to major roads may result in elevated
exposures for children due to potentially increased concentrations
indoors and increased exposures during outdoor activities. Here we
discuss international studies in addition to the limited number of U.S.
studies, because while fleets and fuels outside the U.S. can differ
significantly, the spatial distribution of concentrations is relevant.
    In the Fresno Asthmatic Children's Environment Study (FACES),
traffic-related pollutants were measured on selected days from July
2002 to February 2003 at a central site, and inside and outside of
homes and outdoors at schools of asthmatic children.\103\ Preliminary
data indicate that PAH concentrations are higher at elementary schools
located near primary roads than at elementary schools distant from
primary roads (or located near primary roads with limited access). PAH
concentrations also appear to increase with increase in annual average
daily traffic on nearest major collector. Remaining results regarding
the variance in traffic pollutant concentrations at schools in relation
to proximity to roadways and traffic density will be available in 2006.
---------------------------------------------------------------------------

    \103\ Personal communication with FACES Investigators Fred
Lurmann, Paul Roberts, and Katharine Hammond. Data is currently
being prepared for publication.
---------------------------------------------------------------------------

    The East Bay Children's Respiratory Health Study studied traffic-
related air pollution outside of schools near busy roads in the San
Francisco Bay Area in 2001.\104\ Concentrations of the traffic
pollutants PM10, PM2.5, black carbon, total
NOX, and NO2 were measured at 10 school sites in
neighborhoods that spanned a busy traffic corridor during the spring
and fall seasons. The school sites were selected to represent a range
of locations upwind and downwind of major roads. Differences were
observed in concentrations between schools nearby (<  300 m) versus
those more distant (or upwind) from major roads. Investigators found
spatial variability in exposure to black carbon, NOX, NO,
and (to a lesser extent) NO2, due specifically to roads with
heavy traffic within a relatively small geographic area.
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    \104\ Kim J.J.; Smorodinsky S.; Lipsett M.; et al. (2004)
Traffic-related air pollution near busy roads. Am. J. Respir. Crit.
Care Med. 170: 520-526.
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    A study to assess children's exposure to traffic-related air
pollution while attending schools near motorways was performed in the
Netherlands.\105\ Investigators measured PM2.5,
NO2 and benzene inside and outside of 24 schools located
within 400 m of motorways. The indoor average benzene concentration was
3.2 [mu]g/m\3\ with a range of 0.6-8.1 [mu]g/m\3\. The outdoor average
benzene concentration was 2.2 [mu]g/m\3\ with a range of 0.3-5.0 [mu]g/
m\3\. Overall results indicate that indoor pollutant concentrations are
significantly correlated with traffic density and composition,
percentage of time downwind, and distance from major roadways.
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    \105\ Janssen, N.A.H.; van Vliet, P.H.N.; Aarts, F.; et al.
(2001) Assessment of exposure to traffic related air pollution of
children attending schools near motorways. Atmos. Environ. 35: 3875-
3884.
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    The Toxic Exposure Assessment--Columbia/Harvard (TEACH) study
measured the concentrations of VOCs, PM2.5, black carbon,
and metals outside the homes of high school students in New York
City.\106\ The study was conducted during winter and summer of 1999 on
46 students and their homes. Average winter (and summer) indoor
concentrations exceeded outdoor concentrations by a factor of 2.3
(1.3). In addition, analyses of spatial and temporal patterns of MTBE
concentrations were consistent with traffic patterns. MTBE is a tracer
for motor vehicle pollution.
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    \106\ Kinney, P.L.; Chillrud, S.N.; Ramstrom, S.; et al. (2002)
Exposures to multiple air toxics in New York City. Environ Health
Perspect. 110 (Suppl 4): 539-546.
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    Children are exposed to elevated levels of air toxics not only in
their homes, classrooms, and outside on school grounds, but also during
their commute to school. See the discussion of in-vehicle
concentrations of air toxics above and in Chapter 3 of the RIA.
iii. Pedestrians and Bicyclists
    Researchers have noted that pedestrians and cyclists along major
roads experience elevated exposures to motor vehicle related
pollutants. Although commuting near roadways leads to higher levels of
exposure to traffic pollutants, the general consensus is that exposure
levels of those commuting by walking or biking is lower than for those
who travel by car or bus, (see discussion on in-vehicle exposure in
previous section above). These studies are discussed in Chapter 3 of
the RIA for this rule.

c. Exposure and Concentrations in Homes with Attached Garages
    People living in homes with attached garages are potentially
exposed to substantially higher concentrations of benzene, toluene, and
other VOCs indoors. Homes with attached garages present a special
concern related to infiltration of components of fuel, exhaust, and
other materials stored in garages (including gasoline in gas cans). A
study from the early 1980's found that approximately 30% of an average
nonsmoker's benzene exposure originated from sources in attached
garages.\107\
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    \107\ Wallace, L. (1996) Environmental exposure to benzene: an
update. Environ Health Perspect. 104 (Suppl 6): 1129-1136.
---------------------------------------------------------------------------

    Concentrations within garages are often substantially higher than
those found outdoors or indoors. A recently-completed study in Michigan
found that average concentrations in residential garages were 36.6
[mu]g/m\3\, compared to 0.4 [mu]g/m\3\ outdoors.\108\ A recent study in
Alaska, where fuel benzene concentrations are higher, cold start
emissions are higher, and homes are more tightly sealed than in most of
the U.S., found average garage concentrations of 101 [mu]g/m\3\.\109\
Air passing from these high-benzene locations can cause increased
concentrations indoors.
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    \108\ Batterman, S.; Hatzivasilis, G.; Jia, C. (2006)
Concentrations and emissions of gasoline and other vapors from
residential vehicle garages. Atmos. Environ. 30: 1828-1844.
    \109\ George, M.; Kaluza, P.; Maxwell, B.; Moore, G.; Wisdom, S.
(2002) Indoor air quality & ventilation strategies in new homes in
Alaska. Alaska Building Science Network. http://www.cchrc.org. This

document is available in Docket EPA-HQ-OAR-2005-0036.
---------------------------------------------------------------------------

    Measurement studies have found that homes with attached garages can
have significantly higher concentrations of benzene and other VOCs. One
study from Alaska found that in homes without attached garages, average
benzene concentrations were 8.6 [mu]g/m\3\, while homes with attached
garages had average concentrations of 70.8 [mu]g/m\3\.\110\ Another
showed that indoor CO and total hydrocarbon (THC) concentrations rose
sharply following a cold vehicle starting and pulling out of the
attached garage, persisting for an hour or more.\111\ The study also
showed that cold start emissions accounted for 13-85% of indoor non-
methane hydrocarbons (NMHC), while hot soak emissions accounted for 9-
71% of indoor NMHC. Numerous other studies have shown associations
between VOCs in indoor air and the presence of attached garages. These
studies are discussed in Chapter 3 of the RIA.
---------------------------------------------------------------------------

    \110\ Schlapia, A.; Morris, S. (1998) Architectural, behavioral,
and environmental factors associated with VOCs in Anchorage homes.
Proceedings of the Air & Waste Management Associations 94th Annual
Conference. Paper 98-A504.
    \111\ Graham, L.A.; Noseworthy, L.; Fugler, D.; O'Leary, K.;
Karman, D.; Grande, C. (2004) Contribution of vehicle emissions from
an attached garage to residential indoor air pollution levels. J.
Air & Waste Manage. Assoc. 54: 563-584.
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    EPA has conducted a modeling analysis to examine the influence of
attached garages on personal exposure to benzene.\112\ The analysis
modeled the air flow between the outdoor environment, indoor
environment, and the garage, and accounted for the fraction of home air
intake from the garage. Compared to national average exposure
concentrations of 1.36 [mu]g/m\3\ modeled for 1999 in the National-
Scale Air Toxics Assessment, which do not account for emissions
originating in attached garages, average exposure concentrations for
people with attached garages could more than double. For additional
details, see Chapter 3 of the RIA.
---------------------------------------------------------------------------

    \112\ Bailey, C. (2005) Additional contribution to benzene
exposure from attached garages. Memorandum to the Docket. This
document is available in Docket EPA-HQ-OAR-2005-0036.
---------------------------------------------------------------------------

    Overall, emissions of VOCs within attached garages result in
substantially higher concentrations of benzene and other pollutants
indoors. Proposed reductions in fuel benzene content, new standards for
cold temperature exhaust emissions during vehicle starts, and reduced
emissions from gas cans are all expected to significantly reduce this
major source of exposure.
d. Occupational Exposure
    Occupational settings can be considered a microenvironment in which
exposure to benzene and other air toxics can occur. Occupational
exposures to benzene from mobile sources or fuels can be several orders
of magnitude greater than typical exposures in the non-occupationally
exposed population. Several key occupational groups include workers in
fuel distribution, storage, and tank remediation; handheld and non-
handheld equipment operators; and workers who operate gasoline-powered
engines such as snowmobiles and ATV's. Exposures in these occupational
settings are discussed in Chapter 3 of the RIA.
    In addition, some occupations require that workers spend
considerable time in vehicles, which increases the time they spend in a
higher-concentration microenvironment. In-vehicle concentrations are
discussed in a previous section above.
3. What Are the Size and Characteristics of Highly Exposed Populations?
    A study of the populations in three states (Colorado, Georgia, and
New York) indicated that more than half of the population lives within
200 meters of a major road.\113\ In addition, analysis of data from the
Census Bureau's American Housing Survey suggests that approximately 37
million people live within 300 feet of a 4- or more lane highway,
railroad, or airport. American Housing Survey statistics, as well as
epidemiology studies, indicate that those houses sited near major
transportation sources are more likely to be lower in income or have
minority residents than houses not located near major transportation
sources. These data are discussed in detail in Chapter 3 of the RIA.
---------------------------------------------------------------------------

    \113\ Major roads are defined as those roads defined by the U.S.
Census as one of the following: ``limited access highway,''
``highway,'' ``major road,'' or ``ramp.''
---------------------------------------------------------------------------

    Other population studies also indicate that a significant fraction
of the population resides in locations near major roads. At present,
the available studies use different indicators of ``major road'' and of
``proximity,'' but the estimates range from 12.4% of student enrollment
in California attending schools within 150 meters of roads with 25,000
vehicles per day or more, to 13% of Massachusetts veterans living
within 50 meters of a road with at least 10,000 vehicles per
day.114 115 Using a more general definition of a ``major
road,'' between 22% and 51% of different study populations live near
such roads.
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    \114\ Green, R.S.; Smorodinsky, S.; Kim, J.J.; McLaughlin, R.;
Ostro, B. (2004) Proximity of California public schools to busy
roads. Environ. Health Perspect. 112: 61-66.
    \115\ Garshick, E.; Laden, F.; Hart, J.E.; Caron, A. (2003)
Residence near a major road and respiratory symptoms in U.S.
veterans. Epidemiol. 14: 728-736.
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4. What Are the Implications for Distribution of Individual Risk?
    We have made revisions to HAPEM5, which is the exposure model used
in our national-scale modeling, in order to account for near-road
impacts. The effect of the updated model is best understood as widening
the distribution of exposure, with a larger fraction of the population
being exposed to higher benzene concentrations. Including the effects
of residence locations near roads can result in exposures to some
individuals that are up to 50% higher than those predicted by HAPEM5.
    The revised model, HAPEM6, was run for three states representing
different parts of the country. These areas are intended to represent
different

geographies, development patterns, and housing densities. The states
modeled include Georgia, Colorado, and New York. Overall, these study
results indicate that proximity to major roads can significantly
increase personal exposure for populations living near major roads.
These modeling tools will be extended to a national scale for the final
rulemaking.
    For details on the modeling study with HAPEM6, refer to Chapter 3.2
of the RIA. We used geographic information systems to estimate the
population within each U.S. census tract living at various distances
from a major road (within 75 meters; between 75 and 200 meters; or
beyond 200 meters). An exposure gradient was determined for people
living in each zone, based on dispersion modeling.\116\ These gradients
were confirmed with monitoring studies funded by EPA.\117\ The HAPEM5
model was updated to account for elevated concentrations within these
defined distances from roadways and the population living in these
areas.
---------------------------------------------------------------------------

    \116\ Cohen, J.; Cook, R.; Bailey, C.R.; Carr, E. (2005)
Relationship between motor vehicle emissions of hazardous
pollutants, roadway proximity, and ambient concentrations in
Portland, Oregon. Environ Modelling & Software 20: 7-12.
    \117\ Kwon, J. (2005) Development of a RIOPA database and
evaluation of the effect of proximity on the potential residential
exposure to VOCs from ambient sources. PhD Dissertation. Rutgers,
The State University of New Jersey and University of Medicine and
Dentistry of New Jersey. Written under direction of Dr. Clifford
Weisel. This document is available in Docket EPA-HQ-OAR-2005-0036.
---------------------------------------------------------------------------

C. Ozone

    While the focus of this rule is on air toxics, the proposed vehicle
and gas can standards will also help reduce volatile organic compounds
(VOCs), which are precursors to ozone.
1. Background
    Ground-level ozone, the main ingredient in smog, is formed by the
reaction of VOCs and nitrogen oxides (NOX) in the atmosphere
in the presence of heat and sunlight. These pollutants, often referred
to as ozone precursors, are emitted by many types of pollution sources,
such as highway and nonroad motor vehicles and engines, power plants,
chemical plants, refineries, makers of consumer and commercial
products, industrial facilities, and smaller ``area'' sources. VOCs can
also be emitted by natural sources such as vegetation. The gas can
controls proposed in this action would help reduce VOC emissions by
reducing evaporation, permeation and spillage from gas cans. The
proposed vehicle controls will also reduce VOC emissions; however,
because these reductions will occur at cold temperatures the ozone
benefits will be limited.
    The science of ozone formation, transport, and accumulation is
complex.\118\ Ground-level ozone is produced and destroyed in a
cyclical set of chemical reactions, many of which are sensitive to
temperature and sunlight. When ambient temperatures and sunlight levels
remain high for several days and the air is relatively stagnant, ozone
and its precursors can build up and result in more ozone than typically
would occur on a single high-temperature day. Further complicating
matters, ozone also can be transported into an area from pollution
sources found hundreds of miles upwind, resulting in elevated ozone
levels even in areas with low VOC or NOX emissions. As a
result, differences in VOC and NOX emissions contribute to
daily, seasonal, and yearly differences in ozone concentrations across
different locations.
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    \118\ U.S. EPA (1996). Air Quality Criteria for Ozone and
Related Photochemical Oxidants, EPA600-P-93-004aF. This document is
available in Docket EPA-HQ-OAR-2005-0036.
---------------------------------------------------------------------------

    The current ozone National Ambient Air Quality Standards (NAAQS)
has an 8-hour averaging time. The 8-hour ozone NAAQS, established by
EPA in 1997, is based on well-documented science demonstrating that
more people were experiencing adverse health effects at lower levels of
exertion, over longer periods, and at lower ozone concentrations than
addressed by the previous one-hour ozone NAAQS. It addresses ozone
exposures of concern for the general population and populations most at
risk, including children active outdoors, outdoor workers, and
individuals with pre-existing respiratory disease, such as asthma. The
8-hour ozone NAAQS is met at an ambient air quality monitoring site
when the average of the annual fourth-highest daily maximum 8-hour
average ozone concentration over three years is less than or equal to
0.084 ppm.
2. Health Effects of Ozone
    The health and welfare effects of ozone are well documented and are
critically assessed in the EPA ozone criteria document (CD) and EPA
staff paper.119 120 In August 2005, the EPA released the
second external review draft of a new ozone CD which is scheduled to be
released in final form in February 2006.\121\ This document summarizes
the findings of the 1996 ozone criteria document and critically
assesses relevant new scientific information which has emerged in the
past decade. Additional information on health and welfare effects of
ozone can also be found in the draft RIA for this proposal.
---------------------------------------------------------------------------

    \119\ U.S. EPA (1996). Air Quality Criteria for Ozone and
Related Photochemical Oxidants, EPA600-P-93-004aF. This document is
available in Docket EPA-HQ-OAR-2005-0036.
    \120\ U.S. EPA (1996) Review of National Ambient Air Quality
Standards for Ozone, Assessment of Scientific and Technical
Information, OAQPS Staff Paper, EPA-452/R-96-007. This document is
available in Docket EPA-HQ-OAR-2005-0036.
    \121\ U.S. EPA (2005) Air Quality Criteria for Ozone and Related
Photochemical Oxidants (Second External Review Draft). This document
is available in Docket EPA-HQ-OAR-2005-0036.
---------------------------------------------------------------------------

    Ozone can irritate the respiratory system, causing coughing, throat
irritation, and/or uncomfortable sensation in the chest. Ozone can
reduce lung function and make it more difficult to breathe deeply, and
breathing may become more rapid and shallow than normal, thereby
limiting a person's normal activity. Ozone can also aggravate asthma,
leading to more asthma attacks that require a doctor's attention and/or
the use of additional medication. In addition, ozone can inflame and
damage the lining of the lungs, which may lead to permanent changes in
lung tissue, irreversible reductions in lung function, and a lower
quality of life if the inflammation occurs repeatedly over a long time
period. People who are of particular concern with respect to ozone
exposures include children and adults who are active outdoors. Those
people particularly susceptible to ozone effects are people with
respiratory disease (e.g., asthma), people with unusual sensitivity to
ozone, and children.
    There has been new research that suggests additional serious health
effects beyond those that had been known when the 1996 ozone CD was
published. Since then, over 1,700 new ozone-related health and welfare
studies have been published in peer-reviewed journals.\122\ Many of
these studies have investigated the impact of ozone exposure on such
health effects as changes in lung structure and biochemistry,
inflammation of the lungs, exacerbation and causation of asthma,
respiratory illness-related school absence, hospital and emergency room
visits for asthma and other respiratory causes, and premature

mortality. EPA is currently in the process of evaluating these and
other studies as part of the ongoing review of the air quality criteria
document and NAAQS for ozone. Key new health information falls into
four general areas: development of new-onset asthma, hospital
admissions for young children, school absence rate, and premature
mortality.
---------------------------------------------------------------------------

    \122\ New Ozone Health and Environmental Effects References,
Published Since Completion of the Previous Ozone AQCD, National
Center for Environmental Assessment, Office of Research and
Development, U.S. Environmental Protection Agency, Research Triangle
Park, NC 27711 (7/2002). This document is available in Docket EPA-
HQ-OAR-2005-0036.
---------------------------------------------------------------------------

    Aggravation of existing asthma resulting from short-term ambient
ozone exposure was reported prior to the 1997 NAAQS standard and has
been observed in studies published subsequently.123 124 In
addition, a relationship between long-term ambient ozone concentrations
and the incidence of new-onset asthma in adult males (but not in
females) was reported by McDonnell et al. (1999).\125\ Subsequently, an
additional study suggests that incidence of new diagnoses of asthma in
children is associated with heavy exercise in communities with high
concentrations (i.e., mean 8-hour concentration of 59.6 parts per
billion (ppb) or greater) of ozone.\126\ This relationship was
documented in children who played 3 or more sports and thus spent more
time outdoors. It was not documented in those children who played one
or two sports.
---------------------------------------------------------------------------

    \123\ Thurston, G.D.; Lippman, M.L.; Scott, M.B.; Fine, J.M.
(1997) Summertime Haze Air Pollution and Children with Asthma.
American Journal of Respiratory Critical Care Medicine 155: 654-660.
    \124\ Ostro, B.; Lipsett, M.; Mann, J.; Braxton-Owens, H.;
White, M. (2001) Air pollution and exacerbation of asthma in
African-American children in Los Angeles. Epidemiology 12(2): 200-
208.
    \125\ McDonnell, W.F.; Abbey, D.E.; Nishino, N.; Lebowitz, M.D.
(1999) ``Long-term ambient ozone concentration and the incidence of
asthma in nonsmoking adults: the AHSMOG study.'' Environmental
Research 80(2 Pt 1): 110-121.
    \126\ McConnell, R.; Berhane, K.; Gilliland, F.; London, S.J.;
Islam, T.; Gauderman, W.J.; Avol, E.; Margolis, H.G.; Peters, J.M.
(2002) Asthma in exercising children exposed to ozone: a cohort
study. Lancet 359: 386-391.
---------------------------------------------------------------------------

    Previous studies have shown relationships between ozone and
hospital admissions in the general population. A study in Toronto
reported a significant relationship between 1-hour maximum ozone
concentrations and respiratory hospital admissions in children under
the age of two.\127\ Given the relative vulnerability of children in
this age category, there is particular concern about these findings.
---------------------------------------------------------------------------

    \127\ Burnett, R.T.; Smith-Doiron, M.; Stieb, D.; Raizenne,
M.E.; Brook, J.R.; Dales, R.E.; Leech, J.A.; Cakmak, S.; Krewski, D.
(2001) Association between ozone and hospitalization for acute
respiratory diseases in children less than 2 years of age. Am. J.
Epidemiol. 153: 444-452.
---------------------------------------------------------------------------

    Increased rates of illness-related school absenteeism have been
associated with 1-hour daily maximum and 8-hour average ozone
concentrations in studies conducted in Nevada \128\ in kindergarten to
6th grade and in Southern California in grades four through six.\129\
These studies suggest that higher ambient ozone levels may result in
increased school absenteeism.
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    \128\ Chen, L.; Jennison, B.L.; Yang, W.; Omaye, S.T. (2000)
Elementary school absenteeism and air pollution. Inhalation Toxicol.
12: 997-1016.
    \129\ Gilliland, F.D.; Berhane, K.; Rappaport, E.B.; Thomas,
D.C.; Avol, E.; Gauderman, W.J.; London, S.J.; Margolis, H.G.;
McConnell, R.; Islam, K.T.; Peters, J.M. (2001) The effects of
ambient air pollution on school absenteeism due to respiratory
illnesses. Epidemiology 12:43-54.
---------------------------------------------------------------------------

    The air pollutant most clearly associated with premature mortality
is PM, with many studies reporting such an association. However, recent
analyses provide evidence that short term ozone exposure is associated
with increased premature mortality. Bell et al. (2004) published new
analyses of the 95 cities in the National Morbidity, Mortality, and Air
Pollution Study (NMMAPS) data sets, showing associations between daily
mortality and the previous week's ozone concentrations which were
robust to adjustment for particulate matter, weather, seasonality, and
long-term trends.\130\ Although earlier analyses undertaken as part of
the NMMAPS did not report an effect of ozone on total mortality across
the full year, in those earlier studies the NMMAPS investigators did
observe an effect after limiting the analysis to summer, when ozone
levels are highest.131 132 Another recent study from 23
cities throughout Europe (APHEA2) also found an association between
ambient ozone and daily mortality.\133\ Similarly, other studies have
shown associations between ozone and mortality.134 135
Specifically, Toulomi et al. (1997) found that 1-hour maximum ozone
levels were associated with daily numbers of deaths in four cities
(London, Athens, Barcelona, and Paris), and a quantitatively similar
effect was found in a group of four additional cities (Amsterdam,
Basel, Geneva, and Zurich).
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    \130\ Bell, M.L.; McDermott, A.; Zeger, S.L.; Samet, J.M.;
Dominici, F. Ozone and short-term mortality in 95 U.S. urban
communities, 1987-2000. JAMA 292(19): 2372-2378.
    \131\ Samet, J.M.; Zeger, S.L.; Dominici, F.; Curriero, F.;
Coursac, I.; Dockery, D.W.; Schwartz, J.; Zanobetti, A. (2000) The
National Morbidity, Mortality and Air Pollution Study: Part II:
Morbidity, Mortality and Air Pollution in the United States.
Research Report No. 94, Part II. Health Effects Institute,
Cambridge, MA, June 2000. This document is available in Docket EPA-
HQ-OAR-2005-0036.
    \132\ Samet, J.M.; Zeger, S.L.; Dominici, F.; Curriero, F.;
Coursac, I.; Zeger, S. (2000) Fine Particulate Air Pollution and
Mortality in 20 U.S. Cities, 1987-1994. The New England Journal of
Medicine 343(24): 1742-1749.
    \133\ Gryparis, A.; Forsberg, B.; Katsouyanni, K.; Analitis, A.;
Touloumi, G.; Schwartz, J.; Samoli, E.; Medina, S.; Anderson, H.R.;
Niciu, E.M.; Wichmann, H.E.; Kriz, B.; Kosnik, M.; Skorkovsky, J.;
Vonk, J.M.; Dortbudak, Z. (2004) Acute effects of ozone on mortality
from the ``Air Pollution and Health: A European Approach'' project.
Am. J. Respir. Crit. Care Med. 170: 1080-1087.
    \134\ Thurston, G.D.; Ito, K. (2001) Epidemiological studies of
acute ozone exposures and mortality. J. Exposure Anal. Environ.
Epidemiol. 11: 286-294.
    \135\ Touloumi, G.; Katsouyanni, K.; Zmirou, D.; Schwartz, J.;
Spix, C.; Ponce de Leon, A.; Tobias, A.; Quennel, P.; Rabczenko, D.;
Bacharova, L.; Bisanti, L.; Vonk, J.M.; Ponka, A. (1997) Short-term
effects of ambient oxidant exposure on mortality: A combined
analysis within the APHEA project. Am. J. Epidemiol. 146: 177-185.
---------------------------------------------------------------------------

    In all, the new studies that have become available since the 8-hour
ozone standard was adopted in 1997 continue to demonstrate the harmful
effects of ozone on public health, and the need to attain and maintain
the ozone NAAQS.
3. Current and Projected 8-Hour Ozone Levels
    Currently, ozone concentrations exceeding the level of the 8-hour
ozone NAAQS occur over wide geographic areas, including most of the
nation's major population centers.\136\ As of September 2005 there are
approximately 159 million people living in 126 areas designated as not
in attainment with the 8-hour ozone NAAQS. There are 474 full or
partial counties that make up the 8-hour ozone nonattainment areas.
---------------------------------------------------------------------------

    \136\ A map of the 8-hour ozone nonattainment areas is included
in the RIA for this proposed rule.
---------------------------------------------------------------------------

    EPA has already adopted many emission control programs that are
expected to reduce ambient ozone levels. These control programs include
the Clean Air Interstate Rule (70 FR 25162, May 12, 2005), as well as
many mobile source rules (many of which are described in section V.D).
As a result of these programs, the number of areas that fail to achieve
the 8-hour ozone NAAQS is expected to decrease.
    Based on the recent ozone modeling performed for the CAIR analysis
\137\, barring additional local ozone precursor controls, we estimate
37 Eastern counties (where 24 million people are projected to live)
will exceed the 8-hour ozone NAAQS in 2010. An additional 148 Eastern
counties (where 61 million people are projected to live) are expected
to be within 10 percent of violating the 8-hour ozone NAAQS in 2010.
---------------------------------------------------------------------------

    \137\ Technical Support Document for the Final Clean Air
Interstate Rule Air Quality Modeling. This document is available in
Docket EPA-HQ-OAR-2005-0036.
---------------------------------------------------------------------------

    States with 8-hour ozone nonattainment areas will be required to

take action to bring those areas into compliance in the future. Based
on the final rule designating and classifying 8-hour ozone
nonattainment areas (69 FR 23951, April 30, 2004), most 8-hour ozone
nonattainment areas will be required to attain the 8-hour ozone NAAQS
in the 2007 to 2013 time frame and then be required to maintain the 8-
hour ozone NAAQS thereafter.\138\ We also expect many of the 8-hour
ozone nonattainment areas to adopt additional emission reduction
programs, but we are unable to quantify or rely upon future reductions
from additional state and local programs that have not yet been
adopted. The expected ozone inventory reductions from the standards
proposed in this action may be useful to states in attaining or
maintaining the 8-hour ozone NAAQS.
---------------------------------------------------------------------------

    \138\ The Los Angeles South Coast Air Basin 8-hour ozone
nonattainment area will have to attain before June 15, 2021.
---------------------------------------------------------------------------

    A metamodeling tool developed at EPA, the ozone response surface
metamodel, was used to estimate the effects of the proposed emission
reductions. The ozone response surface metamodel was created using
multiple runs of the Comprehensive Air Quality Model with Extensions
(CAMx). Base and proposed control CAMx metamodeling was completed for
two future years (2020, 2030) over a modeling domain that includes all
or part of 37 Eastern U.S. states. For more information on the response
surface metamodel, please see the RIA for this proposal or the Air
Quality Modeling Technical Support Document (TSD).
    We have made estimates using the ozone response surface metamodel
to illustrate the types of change in future ozone levels that we would
expect to result from this proposed rule, as described in Chapter 3 of
the draft RIA. The proposed gas can controls are projected to result in
a very small net improvement in future ozone, after weighting for
population. Although the net future ozone improvement is small, some
VOC-limited areas in the Eastern U.S. are projected to have non-
negligible improvements in projected 8-hour ozone design values due to
the proposed gas can controls. As stated in Section VII.E.3, we view
these improvements as useful in meeting the 8-hour ozone NAAQS. These
net ozone improvements are in addition to reductions in levels of
benzene due to the proposed gas can controls.

D. Particulate Matter

    The cold temperature vehicle controls proposed here will result in
reductions of primary PM being emitted by vehicles. In addition, both
the proposed vehicle controls and the proposed gas can controls will
reduce VOCs that react in the atmosphere to form secondary
PM2.5, namely organic carbonaceous PM2.5.
1. Background
    Particulate matter (PM) represents a broad class of chemically and
physically diverse substances. It can be principally characterized as
discrete particles that exist in the condensed (liquid or solid) phase
spanning several orders of magnitude in size. PM is further described
by breaking it down into size fractions. PM10 refers to
particles with an aerodynamic diameter less than or equal to a nominal
10 micrometers ([mu]m). PM2.5 refers to fine particles,
those particles with an aerodynamic diameter less than or equal to a
nominal 2.5 [mu]m. Coarse fraction particles refer to those particles
with an aerodynamic diameter less than or equal to a nominal 10 [mu]m.
Inhalable (or ``thoracic'') coarse particles refer to those particles
with an aerodynamic diameter greater than 2.5 [mu]m but less than or
equal to 10 [mu]m. Ultrafine PM refers to particles with diameters of
less than 100 nanometers (0.1 [mu]m). Larger particles (>10 [mu]m) tend
to be removed by the respiratory clearance mechanisms, whereas smaller
particles are deposited deeper in the lungs. Ambient fine particles are
a complex mixture including sulfates, nitrates, chlorides, organic
carbonaceous material, elemental carbon, geological material, and
metals. Fine particles can remain in the atmosphere for days to weeks
and travel through the atmosphere hundreds to thousands of kilometers,
while coarse particles generally tend to deposit to the earth within
minutes to hours and within tens of kilometers from the emission
source.
    EPA has NAAQS for both PM2.5 and PM10. Both
the PM2.5 and PM10 NAAQS consist of a short-term
(24-hour) and a long-term (annual) standard. The 24-hour
PM2.5 NAAQS is set at a level of 65 [mu]g/m\3\ based on the
98th percentile concentration averaged over three years. The annual
PM2.5 NAAQS specifies an expected annual arithmetic mean not
to exceed 15 [mu]g/m\3\ averaged over three years. The 24-hour
PM10 NAAQS is set at a level of 150 [mu]g/m\3\ not to be
exceeded more than once per year. The annual PM10 NAAQS
specifies an expected annual arithmetic mean not to exceed 50 [mu]g/
m\3\.
    EPA has recently proposed to amend the PM NAAQS.\139\ The proposal
includes lowering the level of the primary 24-hour fine particle
standard from the current level of 65 micrograms per cubic meter
([mu]g/m\3\) to 35 [mu]g/m\3\, retaining the level of the annual fine
standard at 15 [mu]g/m\3\, and setting a new primary 24-hour standard
for certain inhalable coarse particles (the indicator is qualified so
as to include any ambient mix of PM10-2.5 that is dominated
by resuspended dust from high-density traffic on paved roads and PM
generated by industrial and construction sources, and excludes any
ambient mix of PM10-2.5 dominated by rural windblown dust
and soils and PM generated by agricultural and mining sources) at 70
[mu]g/m\3\. The Agency is also requesting comment on various other
standards for fine and inhalable coarse PM (71 FR 2620, Jan. 17, 2006).
---------------------------------------------------------------------------

    \139\ U.S. EPA, National Ambient Air Quality Standards for
Particulate Matter (71 FR 2620, Jan. 17, 2006). This document is
also available on the web at: http://www.epa.gov/air/particlepollution/actions.html_____________________________________-

2. Health Effects of PM
    Scientific studies show ambient PM is associated with a series of
adverse health effects. These health effects are discussed in detail in
the 1997 PM criteria document, the recent 2004 EPA Criteria Document
for PM as well as the 2005 PM Staff Paper.140 141 142
Further discussion of health effects associated with PM can also be
found in the draft RIA for this proposal.
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    \140\ U.S.EPA (1996) Air Quality Criteria for Particulate
Matter, EPA 600-P-95-001aF, EPA 600-P-95-001bF. This document is
available in Docket EPA-HQ-OAR-2005-0036.
    \141\ U.S. EPA (2004) Air Quality Criteria for Particulate
Matter (Oct 2004), Volume I Document No. EPA600/P-99/002aF and
Volume II Document No. EPA600/P-99/002bF. This document is available
in Docket EPA-HQ-OAR-2005-0036.
    \142\ U.S. EPA (2005) Review of the National Ambient Air Quality
Standard for Particulate Matter: Policy Assessment of Scientific and
Technical Information, OAQPS Staff Paper. EPA-452/R-05-005. This
document is available in Docket EPA-HQ-OAR-2005-0036.
---------------------------------------------------------------------------

    As described in the documents listed above, health effects
associated with short-term variation (e.g. hours to days) in ambient
PM2.5 include premature mortality, hospital admissions,
heart and lung diseases, increased cough, lower-respiratory symptoms,
decrements in lung function and changes in heart rate rhythm and other
cardiac effects. Studies examining populations exposed to different
levels of air pollution over a number of years, including the Harvard
Six Cities Study and the American Cancer Society Study, show
associations between long-term exposure to ambient PM2.5 and
premature mortality, including deaths attributed to cardiovascular
changes and lung cancer.

    Recently, several studies have highlighted the adverse effects of
PM specifically from mobile sources.143 144 Studies have
also focused on health effects due to PM exposures on or near
roadways.\145\ Although these studies include all air pollution
sources, including both spark-ignition (gasoline) and diesel powered
vehicles, they indicate that exposure to PM emissions near roadways,
thus dominated by mobile sources, are associated with health effects.
The proposed vehicle controls may help to reduce exposures to mobile
source related PM2.5. Additional information on near roadway
health effects can be found in Section III of this preamble.
---------------------------------------------------------------------------

    \143\ Laden, F.; Neas, L.M.; Dockery, D.W.; Schwartz, J. (2000)
Association of Fine Particulate Matter from Different Sources with
Daily Mortality in Six U.S. Cities. Environmental Health
Perspectives 108: 941-947.
    \144\ Janssen, N.A.H.; Schwartz, J.; Zanobetti, A.; Suh, H.H.
(2002) Air Conditioning and Source-Specific Particles as Modifiers
of the Effect of PM10 on Hospital Admissions for Heart
and Lung Disease. Environmental Health Perspectives 110: 43-49.
    \145\ Riekider, M.; Cascio, W.E.; Griggs, T.R.; Herbst, M.C.;
Bromberg, P.A.; Neas, L.; Williams, R.W.; Devlin, R.B. (2003)
Particulate Matter Exposures in Cars is Associated with
Cardiovascular Effects in Healthy Young Men. Am. J. Respir. Crit.
Care Med. 169: 934-940.
---------------------------------------------------------------------------

3. Current and Projected PM2.5 Levels
    EPA has recently finalized PM2.5 nonattainment
designations (70 FR 943, Jan 5. 2005).\146\ As can be seen from the
designations, ambient PM2.5 levels exceeding the level of
the PM2.5 NAAQS are widespread throughout the country. There
are approximately 88 million people living in 39 areas (which include
all or part of 208 counties) designated as not in attainment with the
PM2.5 NAAQS.
---------------------------------------------------------------------------

    \146\ US EPA, Air Quality Designations and Classifications for
the Fine Particles (PM2.5) National Ambient Air Quality
Standards, December 17, 2004. (70 FR 943, Jan 5, 2005) This document
is also available on the web at: http://www.epa.gov/pmdesignations/.

---------------------------------------------------------------------------

    EPA has already adopted many emission control programs that are
expected to reduce ambient PM levels. These rules include the Clean Air
Interstate Rule (70 FR 25162, May 12, 2005), as well as many mobile
source rules. Section V.D details many of these mobile source
rules.\147\ As a result of these programs, the number of areas that
fail to achieve the 1997 PM2.5 NAAQS is expected to
decrease. Based on modeling performed for the CAIR analysis, we
estimate that 28 Eastern counties (where 19 million people are
projected to live) will exceed the PM2.5 standard in
2010.\148\ In addition, 56 Eastern counties (where 24 million people
are projected to live) are expected to be within 10 percent of
violating the PM2.5 in 2010.
---------------------------------------------------------------------------

    \147\ The Clean Air Interstate Rule (CAIR) will reduce emissions
of SO2 and NOX from power plants in the
Eastern 37 states, reducing interstate transport of nitrogen oxides
and sulfur dioxide and helping cities and states in the East meet
the ozone and PM NAAQS. (70 FR 25162) (May 12, 2005).
    \148\ Technical Support Document for the Final Clean Air
Interstate Rule Air Quality Modeling. This document is available in
Docket EPA-HQ-OAR-2005-0036.
---------------------------------------------------------------------------

    While the final implementation process for bringing the nation's
air into attainment with the 1997 PM2.5 NAAQS is still being
completed in a separate rulemaking action, we expect that most areas
will need to attain the 1997 PM2.5 NAAQS in the 2009 to 2014
time frame, and then be required to maintain the NAAQS thereafter. The
expected PM and VOC inventory reductions from the standards proposed in
this action will be useful to states in attaining or maintaining the
PM2.5 NAAQS.
4. Current PM10 Levels
    Air quality monitoring data indicates that as of September 2005
approximately 29 million people live in 55 designated PM10
nonattainment areas, which include all or part of 54 counties. The RIA
for this proposed rule lists the PM10 nonattainment areas
and their populations.
    Based on section 188 of the Act, we expect that most areas will
attain the PM10 NAAQS no later than December 31, 2006,
depending on an area's classification and other factors, and then be
required to maintain the PM10 NAAQS thereafter. The expected
PM and VOC inventory reductions from the standards proposed in this
action could be useful to states in maintaining the PM10
NAAQS.\149\
---------------------------------------------------------------------------

    \149\ As mentioned above, the EPA has recently proposed to amend
the PM NAAQS, by establishing a new indicator for certain inhalable
coarse particles, and a new primary 24-hour standard for coarse
particles described by that indicator. EPA also proposed to revoke
the current 24-hour PM10 standard in all areas of the
country except in those areas with a population of at least 100,000
people and which contain at least one monitor violating the 24-hour
PM10 standard, based on the most recent 3 years of air
quality data. In addition, EPA proposed to revoke upon promulgation
of this rule the current annual PM10 standard if EPA
finalizes the proposed primary standard for PM10-2.5 (71
FR 2620, Jan. 17, 2006).
---------------------------------------------------------------------------

E. Other Environmental Effects

1. Visibility
a. Background
    Visibility can be defined as the degree to which the atmosphere is
transparent to visible light.\150\ Visibility is important because it
has direct significance to people's enjoyment of daily activities in
all parts of the country. Individuals value good visibility for the
well-being it provides them directly, where they live and work, and in
places where they enjoy recreational opportunities. Visibility is also
highly valued in significant natural areas such as national parks and
wilderness areas, because of the special emphasis given to protecting
these lands now and for future generations. For more information on
visibility see the recent 2004 EPA Criteria Document for PM as well as
the 2005 PM Staff Paper.151 152
---------------------------------------------------------------------------

    \150\ National Research Council, 1993. Protecting Visibility in
National Parks and Wilderness Areas. National Academy of Sciences
Committee on Haze in National Parks and Wilderness Areas. National
Academy Press, Washington, DC. This document is available in Docket
EPA-HQ-OAR-2005-0036. This book can be viewed on the National
Academy Press Website at http://www.nap.edu/books/0309048443/html/.

    \151\ U.S. EPA (2004) Air Quality Criteria for Particulate
Matter (Oct 2004), Volume I Document No. EPA600/P-99/002aF and
Volume II Document No. EPA600/P-99/002bF. This document is available
in Docket EPA-HQ-OAR-2005-0036.
    \152\ U.S. EPA (2005) Review of the National Ambient Air Quality
Standard for Particulate Matter: Policy Assessment of Scientific and
Technical Information, OAQPS Staff Paper. EPA-452/R-05-005. This
document is available in Docket EPA-HQ-OAR-2005-0036.
---------------------------------------------------------------------------

    To address the welfare effects of PM on visibility, EPA set
secondary PM2.5 standards in 1997 which would act in
conjunction with the establishment of a regional haze program. EPA
concluded that PM2.5 causes adverse effects on visibility in
various locations, depending on PM concentrations and factors such as
chemical composition and average relative humidity and the secondary
(welfare-based) PM2.5 NAAQS was established as equal to the
suite of primary (health-based) NAAQS (62 FR 38669, July 18, 1997).
Furthermore, Section 169 of the Act provides additional authorities to
remedy existing visibility impairment and prevent future visibility
impairment in the 156 national parks, forests and wilderness areas
categorized as mandatory Federal class I areas (62 FR 38680-81, July
18, 1997).\153\ In July 1999 the regional haze rule (64 FR 35714) was
put in place to protect the visibility in mandatory Federal class I
areas. Visibility can be said to be impaired in both PM2.5
nonattainment areas and mandatory Federal class I areas.\154\
---------------------------------------------------------------------------

    \153\ These areas are defined in section 162 of the Act as those
national parks exceeding 6,000 acres, wilderness areas and memorial
parks exceeding 5,000 acres, and all international parks which were
in existence on August 7, 1977.
    \154\ As mentioned above, the EPA has recently proposed to amend
the PM NAAQS (71 FR 2620, Jan. 17, 2006). The proposal would set the
secondary NAAQS equal to the primary standards for both
PM2.5 and PM10-2.5. EPA also is taking comment
on whether to set a separate PM2.5 standard, designed to
address visibility (principally in urban areas), on potential levels
for that standard within a range of 20 to 30 [mu]g/m3,
and on averaging times for the standard within a range of four to
eight daylight hours.

---------------------------------------------------------------------------

b. Current Visibility Impairment
    Data showing PM2.5 nonattainment areas, and visibility
levels above background at the Mandatory Class I Federal Areas
demonstrate that unacceptable visibility impairment is experienced
throughout the U.S., in multi-state regions, urban areas, and remote
mandatory Federal class I areas.155 156 The mandatory
federal class I areas are listed in Chapter 3 of the draft RIA for this
action. The areas that have design values above the PM2.5
NAAQS are also listed in Chapter 3 of the draft RIA for this action.
---------------------------------------------------------------------------

    \155\ US EPA, Air Quality Designations and Classifications for
the Fine Particles (PM2.5) National Ambient Air Quality
Standards, December 17, 2004. (70 FR 943, Jan 5. 2005) This document
is also available on the web at: http://www.epa.gov/pmdesignations/.

    \156\ US EPA. Regional Haze Regulations, July 1, 1999. (64 FR
35714, July 1, 1999).
---------------------------------------------------------------------------

c. Future Visibility Impairment
    Recent modeling for the Clean Air Interstate Rule (CAIR) was used
to project visibility conditions in mandatory Federal class I areas
across the country in 2015. The results for the mandatory Federal Class
I areas suggest that these areas are predicted to continue to have
annual average deciview levels above background in the future.\157\
Modeling done for the CAIR also projected PM2.5 levels in
the Eastern U.S. in 2010. These projections include all sources of
PM2.5, including the engines covered in this proposal, and
suggest that PM2.5 levels above the 1997 NAAQS will persist
into the future.\158\
    The vehicles that would be subject to the proposed standards
contribute to visibility concerns in these areas through both their
primary PM emissions and their VOC emissions, which contribute to the
formation of secondary PM2.5. The gas cans that would be
subject to the proposed standards also contribute to visibility
concerns through their VOC emissions. Reductions in these direct PM and
VOC emissions will help to improve visibility across the nation,
including mandatory Federal class I areas.
---------------------------------------------------------------------------

    \157\ The deciview metric describes perceived visual changes in
a linear fashion over its entire range, analogous to the decibel
scale for sound. A deciview of 0 represents pristine conditions. The
higher the deciview value, the worse the visibility, and an
improvement in visibility is a decrease in deciview value.
    \158\ EPA recently proposed to revise the current secondary PM
NAAQS standards by making them identical to the suite of proposed
primary standards for fine and coarse particles (71 FR 2620, Jan.
17, 2006).
---------------------------------------------------------------------------

2. Plant Damage From Ozone
    Ozone contributes to many environmental effects, with damage to
plants and ecosystems being of most concern. Plant damage affects crop
yields, forestry production, and ornamentals. The adverse effect of
ozone on forests and other natural vegetation can in turn cause damage
to associated ecosystems, with additional resulting economic losses.
Prolonged ozone concentrations of 100 ppb can be phytotoxic to a large
number of plant species, and can produce acute injury and reduced crop
yield and biomass production. Ozone concentrations within the range of
50 to 100 ppb have the potential over a longer duration to create
chronic stress on vegetation that can result in reduced plant growth
and yield, shifts in competitive advantages in mixed populations,
decreased vigor, and injury. Ozone effects on vegetation are presented
in more detail in the 1996 Criteria Document and the 2005 draft
Criteria Document.
3. Atmospheric Deposition
    Wet and dry deposition of ambient particulate matter delivers a
complex mixture of metals (e.g., mercury, zinc, lead, nickel, aluminum,
cadmium), organic compounds (e.g., POM, dioxins, furans) and inorganic
compounds (e.g., nitrate, sulfate) to terrestrial and aquatic
ecosystems. EPA's Great Waters Program has identified 15 pollutants
whose deposition to water bodies has contributed to the overall
contamination loadings to these Great Waters. These 15 compounds
include several heavy metals and a group known as polycyclic organic
matter (POM). Within POM are the polycyclic aromatic hydrocarbons
(PAHs). PAHs in the environment may be present in the gas or particle
phase, although the bulk will be adsorbed onto airborne particulate
matter. In most cases, human-made sources of PAHs account for the
majority of PAHs released to the environment. The PAHs are usually the
POMs of concern as many PAHs are probable human carcinogens.\159\ For
some watersheds, atmospheric deposition represents a significant input
to the total surface water PAH burden.160 161 Emissions from
mobile sources have been found to account for a percentage of the
atmospheric deposition of PAHs. For instance, recent studies have
identified gasoline and diesel vehicles as the major contributors in
the atmospheric deposition of PAHs to Chesapeake Bay, Massachusetts Bay
and Casco Bay.162 163 The vehicle controls being proposed
may help to reduce deposition of heavy metals and POM.
---------------------------------------------------------------------------

    \159\ Deposition of Air Pollutants to the Great Waters-Third
Report to Congress, Office of Air Quality Planning and Standards,
June 2000, EPA453-R-00-005. This document is available in Docket
EPA-HQ-OAR-2005-0036.
    \160\ Simcik, M.F.; Eisenrich, S.J.; Golden, K.A.; Liu, S.;
Lipiatou, E.; Swackhamer, D.L.; and Long, D.T. (1996) Atmospheric
Loading of Polycyclic Aromatic Hydrocarbons to Lake Michigan as
Recorded in the Sediments. Environ. Sci. Technol. 30:3039-3046.
    \161\ Simcik, M.F.; Eisenrich, S.J.; and Lioy, P.J. (1999)
Source Apportionment and Source/Sink Relationships of PAHs in the
Coastal Atmosphere of Chicago and Lake Michigan. Atmospheric
Environment 33: 5071-5079.
    \162\ Dickhut, R.M.; Canuel, E.A.; Gustafson, K.E.; Liu, K.;
Arzayus, K.M.; Walker, S.E.; Edgecombe, G.; Gaylor, M.O.; and
McDonald, E.H. (2000) Automotive Sources of Carcinogenic Polycyclic
Aromatic Hydrocarbons Associated with Particulate Matter in the
Chesapeake Bay Region. Environ. Sci. Technol. 34: 4635-4640.
    \163\ Golomb, D.; Barry, E.; Fisher, G.; Varanusupakul, P.;
Koleda, M.; amd Rooney, T. (2001) Atmospheric Deposition of
Polycyclic Aromatic Hydrocarbons near New England Coastal Waters.
Atmospheric Environment 35: 6245-6258.
---------------------------------------------------------------------------

4. Materials Damage and Soiling
    The deposition of airborne particles can also reduce the aesthetic
appeal of buildings and culturally important articles through soiling,
and can contribute directly (or in conjunction with other pollutants)
to structural damage by means of corrosion or erosion.\164\ Particles
affect materials principally by promoting and accelerating the
corrosion of metals, by degrading paints, and by deteriorating building
materials such as concrete and limestone. Particles contribute to these
effects because of their electrolytic, hygroscopic, and acidic
properties, and their ability to sorb corrosive gases (principally
sulfur dioxide). The rate of metal corrosion depends on a number of
factors, including the deposition rate and nature of the pollutant; the
influence of the metal protective corrosion film; the amount of
moisture present; variability in the electrochemical reactions; the
presence and concentration of other surface electrolytes; and the
orientation of the metal surface.
---------------------------------------------------------------------------

    \164\ U.S. EPA (2005) Review of the National Ambient Air Quality
Standards for Particulate Matter: Policy Assessment of Scientific
and Technical Information, OAQPS Staff Paper. This document is
available in Docket EPA-HQ-OAR-2005-0036.
---------------------------------------------------------------------------

V. What Are Mobile Source Emissions Over Time and How Would This
Proposal Reduce Emissions, Exposure and Associated Health Effects?

A. Mobile Source Contribution to Air Toxics Emissions

    In 1999, based on the National Emissions Inventory (NEI), mobile
sources accounted for 44% of total

emissions of 188 hazardous air pollutants (on the Clean Air Act section
112(b) list of hazardous air pollutants). Diesel particulate matter
(PM) is not included in this list of 188 pollutants. Sixty-five percent
of the mobile source tons in this inventory were attributable to
highway mobile sources, and the remainder to nonroad sources.
Furthermore, over 90% of mobile source emissions of air toxics (not
including diesel PM) are attributable to gasoline vehicles and
equipment.
    Recently, EPA projected trends in air toxic emissions (not
including diesel PM) to 2020, using the 1999 National Emissions
Inventory (NEI) as a baseline.\165\ Overall, air toxic emissions are
projected to decrease from 5,030,000 tons in 1999 to 4,010,000 tons in
2020, as a result of emission controls on major, area, and mobile
sources. In the absence of Clean Air Act emission controls currently in
place, EPA estimates air toxic emissions would total 11,590,000 tons in
2020.
---------------------------------------------------------------------------

    \165\ Strum, M., R. Cook, J. Thurman, D. Ensley, A. Pope, T.
Palma, R. Mason, H. Michaels, and S. Shedd. 2005. Projection of
Hazardous Air Pollutant Emissions to Future Years. Science of the
Total Environment, in press.
---------------------------------------------------------------------------

    Figure V.A-1 depicts the contributions of source categories to air
toxic emissions between 1990 and 2020.\166\ As indicated in Figure V.A-
1, mobile source air toxic emissions will be reduced 60% between 1999
and 2020, from 2.2 million to 880,000 tons. This reduction will occur
despite a projected 57% increase in vehicle miles traveled, and a
projected 63% increase in nonroad activity, based on units of work
called horsepower-hours. It should be noted, however, that EPA
anticipates mobile source air toxic emissions will begin to increase
after 2020, from about 880,000 tons in 2020 to 920,000 tons in 2030.
This is because, after 2020, reductions from control programs will be
outpaced by increases in activity.
---------------------------------------------------------------------------

    \166\ It should be noted that after 2010, stationary source
emissions are based only on economic growth, and do not account for
reductions from ongoing toxics programs such as the urban air toxics
program, residual risk standards and area source program, which are
expected to further reduce toxics.
---------------------------------------------------------------------------

    In 1999, 29% of air toxic emissions were from highway vehicles and
15% from nonroad equipment. Moreover, 54% of air toxic emissions from
highway vehicles were emitted by light-duty gasoline vehicles (LDGVs)
and 37% by light-duty trucks (LDGTs) (see Table V.A-1). EPA projects
that in 2020, only 27% of highway vehicle toxic emissions will be from
LDGVs and 63% will be from LDGTs. Air toxic emissions from nonroad
equipment are dominated by lawn and garden equipment, recreational
equipment, and pleasure craft, which collectively accounted for almost
80% of nonroad toxic emissions in 1999 and 2020 (see Table V.A-2).
    Figure V.A-1Contribution of Source Categories to Air Toxic
Emissions, 1990 to 2020 (not including diesel particulate matter).
Note: Dashed line represents projected emissions without Clean Air Act
controls.

[GRAPHIC] [TIFF OMITTED] TP29MR06.001

    If diesel PM emissions were added to the mobile source total,
mobile sources would account for 48% of a total 5,398,000 tons in 1999.
Figure V.A.-2 summarizes the trend in diesel PM between 1999 and 2020,
by source category. Diesel PM emissions will be reduced from 368,000
tons in 1999 to 114,000 tons in 2020, a decrease of 70%. As controls on
highway diesel engines and nonroad diesel engines phase in, diesel-
powered locomotives and commercial marine vessels increase from 11% of
the inventory in 1999 to 27% in 2020.
    Subsequent to the development of these projected inventories for
mobile source air toxics, a number of inventory revisions have
occurred. Data EPA has collected indicate that the MOBILE6.2 emission
factor model is under predicting hydrocarbon emissions (including air
toxics) and PM emissions at lower temperatures, from light-duty
vehicles meeting National Low Emission Vehicle (NLEV) and Tier 2
tailpipe standards. The inventories presented in sections V.B, V.C.,
and V.E. reflect these enhancements.

   Table V.A-1.--Percent Contribution of Vehicle Classes to Highway Vehicle Air Toxic Emissions, 1999 to 2020
                                    [Not including diesel particulate matter]
----------------------------------------------------------------------------------------------------------------
                    Vehicle                       1999  (%)    2007  (%)    2010  (%)    2015  (%)    2020  (%)
----------------------------------------------------------------------------------------------------------------
Light-Duty Gasoline Vehicles...................           54           41           37           31           27
Light-Duty Gasoline Trucks.....................           37           49           53           59           63
Heavy-Duty Gasoline Vehicles...................            6            5            4            4            3
Heavy-Duty Diesel Vehicles.....................            3            4            4            4            5
Other (motorcycles and light-duty diesel                   1            1            1            2            2
 vehicles and trucks)..........................
----------------------------------------------------------------------------------------------------------------

           Table V.A-2.--Contribution of Equipment Types to Nonroad Air Toxic Emissions, 1999 to 2020
----------------------------------------------------------------------------------------------------------------
                 Equipment type                   1999  (%)    2007  (%)    2010  (%)    2015  (%)    2020  (%)
----------------------------------------------------------------------------------------------------------------
Lawn and Garden................................           26           18           17           21           25
Pleasure Craft.................................           34           27           25           25           25
Recreational...................................           19           38           40           35           29
All Others.....................................           21           17           18           19           21
----------------------------------------------------------------------------------------------------------------

                                                                                [GRAPHIC] [TIFF OMITTED] TP29MR06.002

B. VOC Emissions From Mobile Sources

    Table V.B-1 presents 48-State VOC emissions from key mobile source
sectors in 1999, 2010, 2015, and 2020, not including the effects of
this proposed rule. The 1999 inventory estimates for nonroad equipment
were obtained from the National Emissions Inventory, and the 2010 and
later year estimates were obtained from the inventories developed for
the Clean Air Interstate Air Quality Rule (CAIR). The table provides
emissions for nonroad equipment such as commercial marine vessels,
locomotives, aircraft, lawn and garden equipment, recreational vehicles
and boats, industrial equipment, and construction equipment. The
estimates for highway vehicle classes were developed for this rule. The
estimates for light-duty gasoline vehicles reflect revised estimates of
hydrocarbon emissions at low temperatures.

    Table V.B-1.--48-State VOC Emissions (Tons) From Key Mobile Source Sectors in 1999, 2010, 2015, and 2020
                                          [Without this proposed rule]
----------------------------------------------------------------------------------------------------------------
                    Category                           1999            2010            2015            2020
----------------------------------------------------------------------------------------------------------------
Light Duty Gasoline Vehicles and Trucks.........       4,873,000       2,896,000       2,566,000       2,486,000

Heavy Duty and Other Highway Vehicles...........         672,000         255,000         212,000         200,000
Nonroad Equipment...............................       2,785,000       1,739,000       1,500,000       1,387,000
----------------------------------------------------------------------------------------------------------------

    VOC emissions from highway vehicles are about twice those from
nonroad equipment in 1999. Emissions from both highway vehicles and
nonroad equipment decline substantially between 1999 and 2020 as a
result of EPA control programs that are already adopted. The VOC
emission reductions associated with this proposed rule are presented in
section V.E, below.

C. PM Emissions From Mobile Sources

    Table V.C-1 presents 48-State PM2.5 \167\ emissions from
key mobile source sectors in 1999, 2010, 2015, and 2020, not including
the effects of this proposed rule. The estimates in Table V.C-1 come
from the same sources as the VOC estimates in section V.B. EPA is
considering revisions to estimates of the PM emissions inventory for
motor vehicles. Recent data suggest PM emissions are significantly
higher than currently estimated in the MOBILE6 emissions model. In
addition, testing done for this rule demonstrates that PM emissions are
elevated at cold temperatures. The estimates in Table V.C-1 do not
account for the effects of cold temperature.
---------------------------------------------------------------------------

    \167\ PM2.5 is particulate matter under 2.5 microns
in diameter. Over 85% of the mass of PM from mobile sources is
PM2.5.

    Table V.C-1--48-State PM2.5 Emissions (Tons) from Key Mobile Source Sectors in 1999, 2010, 2015, and 2020
                                          [Without this proposed rule]
----------------------------------------------------------------------------------------------------------------
                    Category                           1999            2010            2015            2020
----------------------------------------------------------------------------------------------------------------
Light-Duty Gasoline Vehicles and Trucks.........          48,000          33,000          36,000          39,000
Heavy-Duty and Other Highway Vehicles...........         136,000          51,000          28,000          20,000
Nonroad Equipment...............................         332,000         232,000         201,000         178,000
----------------------------------------------------------------------------------------------------------------

    Section V.E, below, presents estimates of PM emission reductions
associated with the proposed cold-temperature vehicle standards.

D. Description of Current Mobile Source Emissions Control Programs That
Reduce MSATs

    As described in section V.A, existing mobile source control
programs will reduce MSAT emissions (not including diesel PM) by 60%
between 1999 and 2020. Diesel PM from mobile sources will be reduced by
70% between 1999 and 2020. The mobile source programs include controls
on fuels, highway vehicles, and nonroad equipment. These programs are
also reducing hydrocarbons and PM more generally, as well as oxides of
nitrogen. The sections immediately below provide general descriptions
of these programs, as well as voluntary programs to reduce mobile
source emissions, such as the National Clean Diesel Campaign and Best
Workplaces for Commuters. A more detailed description of mobile source
programs is provided in Chapter 2 of the RIA.
1. Fuels Programs
    Several federal fuel programs reduce MSAT emissions. Some of these
programs directly control air toxics, such as the reformulated gasoline
(RFG) program's benzene content limit and required reduction in total
toxics emissions, and the anti-backsliding requirements of the anti-
dumping and current MSAT programs, which require that gasoline cannot
get dirtier with respect to toxics emissions. Others, such as the
gasoline sulfur program, control toxics indirectly by reducing
hydrocarbon and related toxics emissions.
a. RFG
    The RFG program contains two direct toxics control requirements.
The first is a fuel benzene standard, requiring RFG to average no
greater than 0.95 volume percent benzene annually (on a refinery or
importer basis). The RFG benzene requirement includes a per-gallon cap
on fuel benzene level of 1.3 volume percent. In 1990, when the Clean
Air Act was amended to require reformulated gasoline, fuel benzene
averaged 1.60 volume percent. For a variety of reasons, including other
regulations, chemical product prices and refining efficiencies, most
refiners and importers have achieved significantly greater reductions
in benzene than required by the program. In 2003, RFG benzene content
averaged 0.62 percent. The RFG benzene requirement includes a per-
gallon cap on fuel benzene level of 1.3 volume percent.
    The second RFG toxics control requires that RFG achieve a specific
level of toxics emissions reduction. The requirement has increased in
stringency since the RFG program began in 1995, when the requirement
was that RFG annually achieve a 16.5% reduction in total (exhaust plus
evaporative) air toxics emissions. Currently, a 21.5% reduction is
required. These reductions are determined using the Complex Model. As
mentioned above, for a variety of reasons most regulated parties have
overcomplied with the required toxics emissions reductions. During
1998-2000, RFG achieved, on average, a 27.5% reduction in toxics
emissions.
b. Anti-Dumping
    The anti-dumping regulations were intended to prevent the dumping
of ``dirty'' gasoline components, which

were removed to produce RFG, into conventional gasoline (CG). Since the
dumping of ``dirty'' gasoline components, for example, benzene or
benzene-containing blending streams, would show up as increases in
toxics emissions, the anti-dumping regulations require that a refiner's
or importer's CG be no more polluting with respect to toxics emissions
than the refiner's or importer's 1990 gasoline. The anti-dumping
program considers only exhaust toxics emissions and does not include
evaporative emissions.\168\ Refiners and importers have either a unique
individual anti-dumping baseline or they have the statutory anti-
dumping baseline if they did not fulfill the minimum requirements for
developing a unique individual baseline. In 1990, average exhaust
toxics emissions (as estimated by the Complex Model) were 104.5 mg/
mile; \169\ in 2004, CG exhaust toxics emissions averaged 90.7 mg/mile.
Although CG has no benzene limit, benzene levels have declined
significantly from the 1990 level of 1.6 volume percent to 1.1 volume
percent for CG in 2004.
---------------------------------------------------------------------------

    \168\ See RFG rule for why evaporative emissions are not
included in the anti-dumping toxics determination.
    \169\ Phase II.
---------------------------------------------------------------------------

c. 2001 Mobile Source Air Toxics Rule (MSAT1)
    As discussed above, both RFG and CG have, on average, exceeded
their respective toxics control requirements. In 2001, EPA issued a
mobile source air toxics rule (MSAT1, for the purposes of this second
proposal), as discussed in section I.D. The intent of MSAT1 is to
prevent refiners and importers from backsliding from the toxics
performance that was being achieved by RFG and CG. In order to lock in
superior levels of control, the rule requires that the annual average
toxics performance of gasoline must be at least as clean as the average
performance of the gasoline produced or imported during the three-year
period 1998-2000. The period 1998-2000 is called the baseline period.
Toxics performance is determined separately for RFG and CG, in the same
manner as the toxics determinations required by the RFG \170\ and anti-
dumping rules.
---------------------------------------------------------------------------

    \170\ 40 CFR Part 80, Subpart D.
---------------------------------------------------------------------------

    Like the anti-dumping provisions, MSAT1 utilizes an individual
baseline against which compliance is determined. The average 1998-2000
toxics performance level, or baseline, is determined separately for
each refinery and importer.\171\ To establish a unique individual MSAT1
baseline, EPA requires each refiner and importer to submit
documentation supporting the determination of the baseline. Most
refiners and many importers in business during the baseline period had
sufficient data to establish an individual baseline. An MSAT1 baseline
volume is associated with each unique individual baseline value. The
MSAT1 baseline volume reflects the average annual volume of such
gasoline produced or imported during the baseline period. Refiners and
importers who did not have sufficient refinery production or imports
during 1998-2000 to establish a unique individual MSAT1 baseline must
use the default baseline provided in the rule.
---------------------------------------------------------------------------

    \171\ Except for those who comply with the anti-dumping
requirements for conventional gasoline on an aggregate basis, in
which case the MSAT1 requirements for conventional gasoline must be
met on the same aggregate basis (40 CFR Part 80, Subpart E).
---------------------------------------------------------------------------

    The MSAT1 program began with the annual averaging period beginning
January 1, 2002. Since then, the toxics performance for RFG has
improved from a baseline period average of 27.5% reduction to 29.5%
reduction in 2003. Likewise, CG toxics emissions have decreased from an
average of 95 mg/mile during 1998-2000 to 90.7 mg/mile in 2003.
d. Gasoline Sulfur
    EPA's gasoline sulfur program \172\ requires, beginning in 2006,
that sulfur levels in gasoline can be no higher in any one batch than
80 ppm, and must average 30 ppm annually. When fully effective,
gasoline will have 90 percent less sulfur than before the program.
Reduced sulfur levels are necessary to ensure that vehicle emission
control systems are not impaired. These systems effectively reduce non-
methane organic gas (NMOG) emissions, of which some are air toxics.
With lower sulfur levels, emission control technologies can work longer
and more efficiently. Both new and older vehicles benefit from reduced
gasoline sulfur levels.
---------------------------------------------------------------------------

    \172\ 65 FR 6822 (February 10, 2000).
---------------------------------------------------------------------------

e. Gasoline Volatility
    A fuel's volatility defines its evaporation characteristics. A
gasoline's volatility is commonly referred to as its Reid vapor
pressure, or RVP. Gasoline summertime RVP ranges from about 6-9 psi,
and wintertime RVP ranges from about 9-14 psi, when additional vapor is
required for starting in cold temperatures. Gasoline vapors contain a
subset of the liquid gasoline components, and thus can contain toxics
compounds such as benzene. EPA has controlled summertime gasoline RVP
since 1989 primarily as a VOC and ozone precursor control, which also
results in some toxics pollutant reductions.
f. Diesel Fuel
    In early 2001, EPA issued rules requiring that diesel fuel for use
in highway vehicles contain no more than 15 ppm sulfur beginning June
1, 2006.\173\ This program contains averaging, banking and trading
provisions, as well as other compliance flexibilities. In June 2004,
EPA issued rules governing the sulfur content of diesel fuel used in
nonroad diesel engines.\174\ In the nonroad rule, sulfur levels are
limited to a maximum of 500 ppm sulfur beginning in 2007 (current
levels are approximately 3000 ppm). In 2010, nonroad diesel sulfur
levels must not exceed 15 ppm.
---------------------------------------------------------------------------

    \173\ 66 FR 5002 (January 18, 2001) http://www.epa.gov/otaq/diesel.html
.

    \174\ 69 FR 38958 (June 29, 2004).
---------------------------------------------------------------------------

    EPA's diesel fuel requirements are part of a comprehensive program
to combine engine and fuel controls to achieve the greatest emission
reductions. The diesel fuel provisions enable the use of advanced
emission-control technologies on diesel vehicles and engines. The
diesel fuel requirements will also provide immediate public health
benefits by reducing PM emissions from current diesel vehicles and
engines.
g. Phase-Out of Lead in Gasoline
    One of the first programs to control toxic emissions from motor
vehicles was the removal of lead from gasoline. Beginning in the mid-
1970s, unleaded gasoline was phased in to replace leaded gasoline. The
phase-out of leaded gasoline was completed January 1, 1996, when lead
was banned from motor vehicle gasoline. The removal of lead from
gasoline has essentially eliminated on-highway mobile source emissions
of this highly toxic substance.
2. Highway Vehicle and Engine Programs
    The 1990 Clean Air Act Amendments set specific emission standards
for hydrocarbons and for PM. Air toxics are present in both of these
pollutant categories. As vehicle manufacturers develop technologies to
comply with the hydrocarbon (HC) and particulate standards (e.g., more
efficient catalytic converters), air toxics are reduced as well. Since
1990, we have developed a number of programs to address exhaust and
evaporative hydrocarbon emissions and PM emissions.
    Two of our recent initiatives to control emissions from motor
vehicles

and their fuels are the Tier 2 control program for light-duty vehicles
and the 2007 heavy-duty engine rule. Together these two initiatives
define a set of comprehensive standards for light-duty and heavy-duty
motor vehicles and their fuels. In both of these initiatives, we treat
vehicles and fuels as a system. The Tier 2 control program establishes
stringent tailpipe and evaporative emission standards for light-duty
vehicles and a reduction in sulfur levels in gasoline fuel beginning in
2004.\175\ The 2007 heavy-duty engine rule establishes stringent
exhaust emission standards for new heavy-duty engines and vehicles for
the 2007 model year as well as reductions in diesel fuel sulfur levels
starting in 2006.\176\ Both of these programs will provide substantial
emissions reductions through the application of advanced technologies.
We expect 90% reductions in PM from new diesel engines compared to
engines under current standards.
---------------------------------------------------------------------------

    \175\ 65 FR 6697, February 10, 2000.
    \176\ 66 FR 5001, January 18, 2001.
---------------------------------------------------------------------------

    Some of the key earlier programs controlling highway vehicle and
engine emissions are the Tier 1 and NLEV standards for light-duty
vehicles and trucks; enhanced evaporative emissions standards; the
supplemental federal test procedures (SFTP); urban bus standards; and
heavy-duty diesel and gasoline standards for the 2004/2005 time frame.
3. Nonroad Engine Programs
    There are various categories of nonroad engines, including land-
based diesel engines (e.g., farm and construction equipment), small
land-based spark-ignition (SI) engines (e.g., lawn and garden
equipment, string trimmers), large land-based SI engines (e.g.,
forklifts, airport ground service equipment), marine engines (including
diesel and SI, propulsion and auxiliary, commercial and recreational),
locomotives, aircraft, and recreational vehicles (off-road motorcycles,
``all terrain'' vehicles and snowmobiles). Chapter 2 of the RIA
provides more information about these programs. As with highway
vehicles, the VOC standards we have established for nonroad engines
will also significantly reduce VOC-based toxics from nonroad engines.
In addition, the standards for diesel engines (in combination with the
stringent sulfur controls on nonroad diesel fuel) will significantly
reduce diesel PM and exhaust organic gases, which are mobile source air
toxics.
    In addition to the engine-based emission control programs described
below, fuel controls will also reduce emissions of air toxics from
nonroad engines. For example, restrictions on gasoline formulation (the
removal of lead, limits on gasoline volatility and RFG) are projected
to reduce nonroad MSAT emissions because most gasoline-fueled nonroad
vehicles are fueled with the same gasoline used in on-highway vehicles.
An exception to this is lead in aviation gasoline. Aviation gasoline,
used in general (as opposed to commercial) aviation, is a high octane
fuel used in a relatively small number of aircraft (those with piston
engines). Such aircraft are generally used for personal transportation,
sightseeing, crop dusting, and similar activities.
4. Voluntary Programs
    In addition to the fuel and engine control programs described
above, we are actively promoting several voluntary programs to reduce
emissions from mobile sources, such as the National Clean Diesel
Campaign, anti-idling measures, and Best Workplaces for Commuters.
While the stringent emissions standards described above apply to new
highway and nonroad diesel engines, it is also important to reduce
emissions from the existing fleet of about 11 million diesel engines.
EPA has launched a comprehensive initiative called the National Clean
Diesel Campaign, one component of which is to promote the reduction of
emissions in the existing fleet of engines through a variety of cost-
effective and innovative strategies. The goal of the Campaign is to
reduce emissions from the 11 million existing engines by 2014. Emission
reduction strategies include switching to cleaner fuels, retrofitting
engines through the addition of emission control devices, and engine
replacement. For example, installing a diesel particulate filter
achieves diesel particulate matter reductions of approximately 90
percent (when combined with the use of ultra low sulfur diesel fuel).
The Energy Policy Act of 2005 includes grant authorizations and other
incentives to help facilitate voluntary clean diesel actions
nationwide.
    The National Clean Diesel Campaign is focused on leveraging local,
state, and federal resources to retrofit or replace diesel engines,
adopt best practices, and track and report results. The Campaign
targets five key sectors: School buses, ports, construction, freight,
and agriculture.
    Reducing vehicle idling provides important environmental benefits.
As a part of their daily routine, truck drivers often keep their
vehicles at idle during stops to provide power, heat and air
conditioning. EPA's SmartWay Transport Partnership is helping the
freight industry to adopt innovative idle reduction technologies and
take advantage of proven systems that provide drivers with basic
necessities without using the engine. To date, there are 50 stationary
anti-idling projects, and mobile technology has been installed on
nearly 20,000 trucks. The SmartWay Transport Partnership also works
with the freight industry to reduce fuel use (with a concomitant
reduction in emissions) by promoting a wide range of new technologies
such as advanced aerodynamics, single-wide tires, weight reduction
speed control and intermodal shipping.
    Daily commuting represents another significant source of emissions
from motor vehicles. EPA's Best Workplaces for CommutersSM
program is working with employers across the country to reverse the
trend of longer, single-occupancy vehicle commuting. OTAQ has created a
national list of the Best Workplaces for Commuters to formally
recognize employers that offer superior commuter benefits such as free
transit passes, subsidized vanpools/carpools, and flexi-place, or work-
from-home, programs. More than 1,300 employers representing 2.8 million
U.S. workers have been designated Best Workplaces for Commuters.
    Much of the growth in the Best Workplaces for Commuters program has
been through metro area-wide campaigns. Since 2002, EPA has worked with
coalitions in 14 major metropolitan areas to increase the penetration
of commuter benefits in the marketplace and the visibility of the
companies that have received the BWC designation. Another significant
path by which the program has grown is through Commuter Districts
including corporate and industrial business parks, shopping malls,
business improvement districts and downtown commercial areas. To date
EPA has granted the Best Workplaces for Commuters ``District''
designation to twenty locations across the country including downtown
Denver, Houston, Minneapolis and Tampa.

E. Emission Reductions From Proposed Controls

1. Proposed Vehicle Controls
    We are proposing a hydrocarbon standard for gasoline passenger
vehicles at cold temperatures. This standard will reduce VOC at
temperatures below 75 [deg]F, including air toxics such as benzene,
1,3-butadiene, formaldehyde, acetaldehyde, acrolein and naphthalene,
and will also reduce emissions of direct and secondary PM. We are also
proposing new evaporative emissions standards for Tier 2 vehicles
starting in

2009. These new evaporative standards reflect the emissions levels
already being achieved by manufacturers.
a. Volatile Organic Compounds (VOC)
    Table V.E-1 shows the VOC exhaust emission reductions from light-
duty gasoline vehicles and trucks that would result from our proposed
standards. The proposed standards would reduce VOC emissions in 2030 by
32%. Overall VOC exhaust emissions from these vehicles would be reduced
by 81% between 1999 and 2030 (including the effects of the proposed
standards as well as standards already in place, such as Tier 2).

   Table V.E-1.--Estimated National Reductions in Exhaust VOC Emissions From Light-Duty Gasoline Vehicles and
                                              Trucks, 1999 to 2030
----------------------------------------------------------------------------------------------------------------
                                                       1999            2015            2020            2030
----------------------------------------------------------------------------------------------------------------
VOC Without Rule (tons).........................       4,899,891       2,625,076       2,556,751       2,899,269
VOC With Proposed Vehicle Standards (tons)......             N.A       2,305,202       2,020,267       1,985,830
VOC Reductions from Proposed Vehicle Standards               N.A         319,874         536,484         913,439
 (tons).........................................
Percentage Reduction............................             N.A              12              21              32
----------------------------------------------------------------------------------------------------------------

b. Toxics
    In 2030, we estimate that the proposed vehicle standards would
result in a 38% reduction in benzene emissions and 37% reduction in
total emissions of the MSATs \177\ from light-duty vehicles and trucks
(see Tables V.E-2 and V.E-3).
---------------------------------------------------------------------------

    \177\ Table IV.A-1 lists the MSATs included in this analysis.

 Table V.E-2.--Estimated National Reductions in Benzene Exhaust Emissions From Light-Duty Gasoline Vehicles and
                                              Trucks, 1999 to 2030
----------------------------------------------------------------------------------------------------------------
                                                       1999            2015            2020            2030
----------------------------------------------------------------------------------------------------------------
Benzene Without Rule (tons).....................         171,154         101,355         106,071         124,897
Benzene With Proposed Vehicle Standards (tons)..            N.A.          84,496          77,966          77,208
Benzene Reductions from Proposed Vehicle                    N.A.          16,859          28,105          47,689
 Standards (tons)...............................
Percentage Reduction............................            N.A.              17              26              38
----------------------------------------------------------------------------------------------------------------

   Table V.E-3.--Estimated National Reductions in Exhaust MSAT Emissions From Light-Duty Gasoline Vehicles and
                                              Trucks, 1999 to 2030
----------------------------------------------------------------------------------------------------------------
                                                       1999            2015            2020            2030
----------------------------------------------------------------------------------------------------------------
MSATs Without Rule (tons).......................       1,341,572         707,877         724,840         844,366
MSATs With Proposed Vehicle Standards (tons)....            N.A.         599,492         543,332         535,479
MSAT Reductions from Proposed Vehicle Standards             N.A.         108,385         181,509         308,887
 (tons).........................................
Percentage Reduction............................            N.A.              15              25              37
----------------------------------------------------------------------------------------------------------------

c. PM2.5
    EPA expects that the proposed cold-temperature vehicle standards
would reduce exhaust emissions of direct PM2.5 by over
20,000 tons in 2030 nationwide (see Table V.E-4 below). Our analysis of
the data from vehicles meeting Tier 2 emission standards indicate that
PM emissions follow a monotonic relationship with temperature, with
lower temperatures corresponding to higher vehicle emissions.
Additionally, the analysis shows the ratio of PM to total non-methane
hydrocarbons (NMHC) to be independent of temperature.\178\ Our testing
indicates that strategies which reduce NMHC start emissions at cold
temperatures also reduce direct PM emissions. Based on these findings,
direct PM emissions at cold temperatures were estimated using a
constant PM to NMHC ratio. PM emission reductions were estimated by
assuming that NMHC reductions will result in proportional reductions in
PM. This assumption is supported by test data. For more detail, see
Chapter 2.1 of the RIA.
---------------------------------------------------------------------------

    \178\ U.S. EPA. 2005. Cold-temperature exhaust particulate
matter emissions. Memorandum from Chad Bailey to docket EPA-HQ-OAR-
2005-0036.

 Table V.E-4.--Estimated National Reductions in Direct PM2.5 Exhaust Emissions From Light-Duty Gasoline Vehicles
                                            and Trucks, 2015 to 2030
----------------------------------------------------------------------------------------------------------------
                                                                       2015            2020            2030