eligibility of emissions standards for nonconformance penalties in any
given model year: (1) The emissions standard in question must become
more difficult to meet, (2) substantial work must be required in order
to meet the standard, and (3) a technological laggard must be likely to
develop (40 CFR 86.1103-87). A technological laggard is a manufacturer
who cannot meet a particular emissions standard due to technological
(not economic) difficulties and who, in the absence of nonconformance
penalties, might be forced from the marketplace. The process to
determine if these criteria are met and to establish penalty amounts
and conditions is carried out via rulemaking, as required by the CAA.
The CAA (in section 205) also lays out requirements for the assessment
of civil penalties for noncompliance with emissions standards.
    As discussed in detail in Section III, the agencies have determined
that the final GHG and fuel consumption standards are readily feasible,
and we do not believe a technological laggard will emerge in any sector
covered by these final standards. In addition to the standards being
premised on use of already-existing, cost-effective technologies, there
are a number of flexibilities and alternative standards built into the
proposal. However, in the case of potential non-conformance, civil
penalties will ensure that adequate deterrence for non-conformance
exists.
(2) NHTSA's Penalty Process
    NHTSA proposed a detailed enforcement process in the NPRM. As
proposed, enforcement would begin with a notice of violation, after
which the respondent may either pay the penalty proposed in the notice
of violation or dispute it by requesting an agency hearing. For a party
that did not pay the proposed penalty or request a hearing within 30
days of the notice of violation, a finding of default would be entered
and the penalty set forth in the notice of violation assessed. If a
hearing is timely requested, the respondent would receive written
notice of the time, date and location of the hearing. The respondent
would have the right to counsel and to examine, respond to and rebut
evidence presented by the Chief Counsel. If civil penalties greater
than $250,000,000 were assessed in the Hearing Officer's final order,
that order would contain a statement advising the party of the right to
appeal to the NHTSA Administrator. In the event of a timely appeal, the
decision of the Administrator would be a final agency action. This
structure was intended to ensure that a party was afforded ample
opportunity to be heard.
    Several manufacturers commented that NHTSA's penalty procedures
should be more formal than was proposed in the NPRM. EMA, Volvo and
Navistar commented that the penalty procedures should be subject to the
Administrative Procedure Act (APA) review requirements. EMA, Volvo and
Navistar, and TRALA commented that the penalty procedures violated due
process requirements. EMA argued that NHTSA must expressly grant a
right to judicial review, and EMA and Navistar argued that the absence
of an administrative appeals process for penalties under $250,000,000
would violate due process. Volvo faulted NHTSA for not classifying the
hearing officer's decision as a final agency action, and stated that
specifications regarding who could be a hearing officer should align
with those specified for the light-duty program, which was laid out in
49 CFR 511.3.
    As noted in the NPRM, the APA administrative hearing requirements
of Sections 554, 556, and 557 are not required where formal procedures
are not required by statute (generally, the organic statute must
provide that the administrative proceeding must be an adjudication,
determined on the record after the opportunity for an agency hearing,
sometimes referenced as an opportunity for hearing on the record). See
e.g., 5 U.S.C. Section 554. Where a formal adjudication is not required
by statute, in general, agencies adopt and apply informal processes.
While the compliance, civil penalty and appeals provisions of 49 U.S.C.
Sections 32911 and 32914 require formal adjudication in accordance with
APA requirements, those sections only apply to the light-duty fuel
economy program. In contrast, for the heavy-duty program of Section
32902(k), the Congress did not require formal adjudication in
accordance with the APA. Therefore, informal adjudication procedures
may be applied. NHTSA will not adopt the procedures of by 5 U.S.C.
Sections 554, 556, or 557 for the final rule.
    While the APA requirements for formal hearing procedures do not
apply to NHTSA's enforcement under Section 32902(k), due process
requirements do apply. NHTSA believes that formal procedures are
neither required by statute nor necessary for this enforcement process
to meet due process requirements. NHTSA expects that the cases will not
be complex. In general, there will be one or two issues: (1) Compliance
with the regulations and, if not, (2) the appropriate civil penalty.
Compliance likely will involve narrow technical questions under the
regulations being adopted today. Non-compliance with applicable fuel
consumption standards will be determined by utilizing the certified and
reported CO2 emissions and fuel consumption data provided by
EPA as described in this part, and after considering all the
flexibilities available under Section 535.7. Much of the evidence will
be materials developed by the respondent. There likely will not be wide
ranging issues. The parties will have ample opportunity to present
their positions. A hearing officer can readily address the sorts of
questions that are likely to arise. Second, if there is a
noncompliance, there will be the question of the appropriate penalty.
NHTSA's regulations contain factors to be considered in assessing
penalties. Again, the parties will have ample opportunity to present
their positions. Ultimately, the agency's final decision must be
sufficiently reasoned to withstand judicial review, based on the
arbitrary and capricious standard.
    To address commenters' concerns about the process provided, NHTSA
made several adjustments and clarifications in the final rule. The
final rule provides that there will be a written decision of the
Hearing Officer, and the assessment of a civil penalty by a hearing
officer shall be set forth in an accompanying final order. Together,
these constitute the final agency action. NHTSA has also revisited the
minimum penalty level for an administrative appeal to the NHTSA
Administrator and decided to lower the level significantly, to
$1,000,000. This provides a second level of review. NHTSA believes this

will promote an efficient use of administrative remedies and a further
opportunity to be heard at the administrative level. Of course, if a
party files an appeal with the NHTSA Administrator, the Hearing
Officer's decision and order at that juncture shall no longer be final
agency action.
    NHTSA has considered the specifications of the Hearing Officer and
determined that they are adequate for informal agency hearings of this
nature. However, the agency will add a clarification to the final rule
that specifies that the Hearing Officer will be appointed by the
Administrator. Further, in addition to having no prior connection with
the case and no responsibility, direct or supervisory, for the
investigation of cases referred for the assessment of civil penalties,
the Hearing Officer will have no duties related to the light-duty fuel
economy or medium- and heavy-duty fuel efficiency programs.
    NHTSA has also considered EMA's comment that a right to judicial
review must be specified in the regulatory text. The agency does not
agree with this concern. Parties, of course, cannot confer
jurisdiction; only Congress can do so. Whitman v. Department of
Transportation, 547 U.S. 512, 514 (2006); Weinberger v. Bentex
Pharmaceuticals, Inc., 412 U.S. 645, 652 (1973). Moreover, judicial
review of a final agency action is presumed. United States v. Fausto,
484 U.S. 439, 452 (1998), citing Abbot Laboratories v. Gardner, 387
U.S. 136, 140 (1967). See generally, 28 U.S.C. Section 1331. Therefore,
NHTSA has determined that the right to judicial review does not need to
be specified in the regulatory text.

VI. How will this program impact fuel consumption, GHG emissions, and
climate change?

A. What methodologies did the agencies use to project GHG emissions and
fuel consumption impacts?

    EPA and NHTSA used EPA's official mobile source emissions inventory
model named Motor Vehicle Emissions Simulator (MOVES2010),\320\ to
estimate emission and fuel consumption impacts of these final rules.
MOVES has the capability to take in user inputs to modify default data
to better estimate emissions for different scenarios, such as different
regulatory alternatives, state implementation plans (SIPs), geographic
locations, vehicle activity, and microscale projects.
---------------------------------------------------------------------------

    \320\ MOVES homepage: http://www.epa.gov/otaq/models/moves/index.htm. Version MOVES2010 was used for emissions impacts analysis
for this action. Current version as of September 14, 2010 is an
updated version named MOVES2010a, available directly from the MOVES
homepage. To replicate results from this action, MOVES2010 must be
used.
---------------------------------------------------------------------------

    The agencies performed multiple MOVES runs to establish reference
case and control case emission inventories and fuel consumption values.
The agencies ran MOVES with user input databases that reflected
characteristics of the final rules, such as emissions improvements and
recent sales projections. Some post-processing of the model output was
required to ensure proper results. The agencies ran MOVES for non-GHGs,
CO2, CH4, and N2O for calendar years
2005, 2018, 2030, and 2050. Additional runs were performed for just the
three greenhouse gases and for fuel consumption for every calendar year
from 2014 to 2050, inclusive, which fed the economy-wide modeling,
monetized greenhouse gas benefits estimation, and climate impacts
analyses.
    The agencies also used MOVES to estimate emissions and fuel
consumption impacts for the other alternatives considered and described
in Section IX.

B. MOVES Analysis

(i) Inputs and Assumptions
    The analysis performed for the final action mirrors what was done
for the proposal. The methods and models are the same, with differences
lying primarily in the inputs, as a result of updates in the program,
standards, and baseline data.
(a) Reference Run Updates
    Since MOVES2010a vehicle sales and activity data were developed
from AEO2009, EPA first updated these data using sales and activity
estimates from AEO2011. MOVES2010a defaults were used for all other
parameters to estimate the reference case emissions inventories.
(b) Control Run Updates
    EPA developed additional user input data for MOVES runs to estimate
control case inventories. To account for improvements of engine and
vehicle efficiency, EPA developed several user inputs to run the
control case in MOVES. As explained at proposal, since MOVES does not
operate based on Heavy-duty FTP cycle results, EPA used the percent
reduction in engine CO2 emissions expected due to the final
rules to develop energy inputs for the control case runs. 75 FR at
74280. Also, EPA used the percent reduction in aerodynamic drag and
tire rolling resistance coefficients and reduction in average total
running weight (gross combined weight) expected from the final rules to
develop road load input for the control case. The sales and activity
data updates used in the reference case were used in the control case.
Details of all the MOVES runs, input data tables, and post-processing
steps are available in the docket (EPA-HQ-OAR-2010-0162).
    Table VI-1 and Table VI-2 describe the estimated expected
reductions from these final rules, which were input into MOVES for
estimating control case emissions inventories.
---------------------------------------------------------------------------

    \321\ Section II of this preamble discusses an alternative
engine standard for the HD diesel engines in the 2014, 2015, and
2016 model years. To the extent that engines using this alternative
are expected to have baseline emissions greater than the industry
average, the reduction from the industry average projected in this
program would be reduced.

                       Table VI-1--Estimated Reductions in Engine CO2 Emission Rates \321\
----------------------------------------------------------------------------------------------------------------
                                                                                CO2 reduction
                  GVWR class                                  Fuel                  Model years    from 2010 MY
----------------------------------------------------------------------------------------------------------------
HHD (Class 8a-8b).............................  Diesel..........................       2014-2016              3%
                                                                                2017+              6%
MHD (Class 6-7) and LHD (Class 4-5)...........  Diesel..........................       2014-2016              5%
                                                                                2017+              9%
                                                Gasoline........................           2016+              5%
----------------------------------------------------------------------------------------------------------------

   Table VI-2--Estimated Reductions in Rolling Resistance Coefficient, Aerodynamic Drag Coefficient, and Gross
                                                 Combined Weight
----------------------------------------------------------------------------------------------------------------
                                                              Reduction in
                                                              tire CRR from    Reduction in Cd  Weight reduction
                        Truck type                              baseline        from baseline         (lbs.)
                                                                (percent)         (percent)
----------------------------------------------------------------------------------------------------------------
Combination long-haul.....................................               9.6              12.1               400
Combination short-haul....................................               7.0               5.9               321
Straight trucks, refuse trucks, motor homes, transit                     5.0                 0                 0
 buses, and other vocational vehicles.....................
----------------------------------------------------------------------------------------------------------------

    Since nearly all HD pickup trucks and vans will be certified on a
chassis dynamometer, the CO2 reductions for these vehicles
will not be represented as engine and road load reduction components,
but rather as total vehicle CO2 reductions. These estimated
reductions are described in Table VI-3.

                Table VI-3--Estimated Total Vehicle CO2 Reductions for HD Pickup Trucks and Vans
----------------------------------------------------------------------------------------------------------------
                                                                                CO2 reduction
                 GVWR Class                                Fuel                  Model year       from baseline
                                                                                (percent)
----------------------------------------------------------------------------------------------------------------
HD Pickup Trucks and Vans...................  Gasoline......................              2014               1.5
                                                                                2015                 2
                                                                                2016                 4
                                                                                2017                 6
                                                                                2018+                10
                                              Diesel........................              2014               2.3
                                                                                2015                 3
                                                                                2016                 6
                                                                                2017                 9
                                                                                2018+                15
----------------------------------------------------------------------------------------------------------------

C. What are the projected reductions in fuel consumption and GHG
emissions?

    EPA and NHTSA expect significant reductions in GHG emissions and
fuel consumption from these final rules--emission reductions from both
downstream (tailpipe) and upstream (fuel production and distribution)
sources, and fuel consumption reductions from more efficient vehicles.
Increased vehicle efficiency and reduced vehicle fuel consumption will
also reduce GHG emissions from upstream sources. The following
subsections summarize the GHG emissions and fuel consumption reductions
expected from these final rules.
(1) Downstream (Tailpipe)
    Consistent with the proposal, EPA used MOVES to estimate downstream
GHG inventories from these final rules. We expect reductions in
CO2 from all heavy-duty vehicle categories. The reductions
come from engine and vehicle improvements. EPA expects N2O
emissions to increase very slightly because of a rebound in vehicle
miles traveled (VMT) and because significant vehicle emissions
reductions are not expected from these final rules. In the proposal, we
did not account for differences in methane emissions from use of
auxiliary power units (APUs) during extended idling from sleeper cab
combination tractors. After accounting for these differences, EPA
expects methane emissions to decrease primarily due to differences in
hydrocarbon emission characteristics between on-road diesel engines and
APUs. The amount of methane emitted as a fraction of total hydrocarbons
is significantly less for APUs than for diesel engines equipped with
diesel particulate filters. Overall, downstream GHG emissions will be
reduced significantly and are described in the following subsections.
    For CO2 and fuel consumption, the total energy
consumption ``pollutant'' was run in MOVES rather than CO2
itself. The energy was converted to fuel consumption based on fuel
heating values assumed in the Renewable Fuels Standard and used in the
development of MOVES emission and energy rates. These values are
117,250 kJ/gallon for gasoline blended with ten percent ethanol (E10)
\322\ and 138,451 kJ/gallon for diesel.\323\ To calculate
CO2, the agencies assumed a CO2 content of 8,576
g/gallon for E10 and 10,180 g/gallon for diesel. Table VI-4 shows the
fleet-wide GHG reductions and fuel savings from reference case to
control case through the lifetime of model year 2014 through 2018
heavy-duty vehicles. Table VI-5 shows the downstream GHG emissions
reductions and fuel savings in 2018, 2030, and 2050. The analysis
follows what was done for the proposal. We did not receive comments
indicating that this analysis was inappropriate or insufficient for
estimating downstream emissions impacts of this program.
---------------------------------------------------------------------------

    \322\ Renewable Fuels Standards assumptions of 115,000 BTU/
gallon gasoline (E0) and 76,330 BTU/gallon ethanol (E100) weighted
90% and 10%, respectively, and converted to kJ at 1.055 kJ/BTU.
    \323\ MOVES2004 Energy and Emission Inputs. EPA420-P-05-003,
March 2005. http://www.epa.gov/otaq/models/ngm/420p05003.pdf.

  Table VI-4--Model Year 2014 Through 2018 Lifetime GHG Reductions and
                Fuel Savings by Heavy-Duty Truck Category
------------------------------------------------------------------------
                                 Downstream GHG
                                reductions  (MMT        Fuel Savings
                                     CO2eq)           (billion gallons)
------------------------------------------------------------------------
HD pickups/vans.............                    18                   1.9
Vocational..................                    24                   2.4
Combination short-haul (Day                     50                   4.9
 cabs)......................
Combination long-haul                          135                  12.9
 (Sleeper cabs).............
------------------------------------------------------------------------

         Table VI-5--Annual Downstream GHG Emissions Reductions and Fuel Savings in 2018, 2030, and 2050
----------------------------------------------------------------------------------------------------------------
                                                   Downstream GHG
                                                  reductions  (MMT       Diesel Savings       Gasoline Savings
                                                       CO2eq)           (million gallons)     (million gallons)
----------------------------------------------------------------------------------------------------------------
2018..........................................                    22                 2,123                    59
2030..........................................                    61                 5,670                   349
2050..........................................                    89                 8,158                   522
----------------------------------------------------------------------------------------------------------------

(2) Upstream (Fuel Production and Distribution)
    Using the same approach as used in the NPRM, the upstream GHG
emission reductions associated with the production and distribution of
fuel were projected using emission factors from DOE's ``Greenhouse
Gases, Regulated Emissions, and Energy Use in Transportation''
(GREET1.8) model, with some modifications consistent with the Light-
Duty 2012-2016 MY vehicle rule. More information regarding these
modifications can be found in the RIA Chapter 5. These estimates
include both international and domestic emission reductions, since
reductions in foreign exports of finished gasoline and/or crude make up
a significant share of the fuel savings resulting from the GHG
standards. Thus, significant portions of the upstream GHG emission
reductions will occur outside of the United States; a breakdown and
discussion of projected international versus domestic reductions is
included in the RIA Chapter 5. GHG emission reductions from upstream
sources can be found in Table VI-6.

                  Table VI-6--Annual Upstream GHG Emissions Reductions in 2018, 2030, and 2050
----------------------------------------------------------------------------------------------------------------
                                                                                Total GHG  (MMT
                                             CO2  (MMT)     CH4  (MMT CO2eq)  N2O  (MMT CO2eq)       CO2eq)
----------------------------------------------------------------------------------------------------------------
2018....................................               5.1               0.9              0.02               6.0
2030....................................              12.2               1.9              0.06              14.2
2050....................................              16.4               2.5              0.08              19.0
----------------------------------------------------------------------------------------------------------------

(3) HFC Emissions
    Based on projected HFC emission reductions due to the final AC
leakage standards, EPA estimates the HFC reductions to be 120,000
metric tons of CO2eq in 2018, 440,000 metric tons of
CO2eq emissions in 2030 and 600,000 metric tons
CO2eq in 2050, as detailed in RIA Chapter 5.3.4.
(4) Total (Upstream + Downstream + HFC)
    Table VI-7 combines downstream results from Table VI-5, upstream
results Table VI-6, and HFC results to show total GHG reductions for
calendar years 2018, 2030, and 2050.

  Table VI-7--Annual Total GHG Emissions Reductions in 2018, 2030, and
                                  2050
------------------------------------------------------------------------
                                                         GHG reductions
                                                           (MMT CO2eq)
------------------------------------------------------------------------
2018..................................................                29
2030..................................................                76
2050..................................................               108
------------------------------------------------------------------------

D. Overview of Climate Change Impacts From GHG Emissions

    Once emitted, GHGs that are the subject of this regulation can
remain in the atmosphere for decades to millennia, meaning that 1)
their concentrations become well-mixed throughout the global atmosphere
regardless of emission origin, and 2) their effects on climate are long
lasting. GHG emissions come mainly from the combustion of fossil fuels
(coal, oil, and gas), with additional contributions from the clearing
of forests and agricultural activities. Transportation activities, in
aggregate, are the second largest contributor to total U.S. GHG
emissions (27 percent of total emissions) despite a decline in
emissions from this sector during 2008.\324\
---------------------------------------------------------------------------

    \324\ U.S. EPA (2010) Inventory of U.S. Greenhouse Gas Emissions
and Sinks: 1990-2007. EPA-430-R-10-006, Washington, DC.
---------------------------------------------------------------------------

    This section provides a summary of observed and projected changes
in GHG emissions and associated climate change impacts. The source
document for the section below is the Technical Support Document (TSD)
\325\ for EPA's Endangerment and Cause or Contribute Findings Under the
Clean Air Act (74 FR 66496, December 15, 2009). Below is the Executive
Summary of the TSD which provides technical support for the
endangerment and cause or contribute analyses concerning GHG emissions
under section 202(a) of the CAA. The TSD reviews observed and

projected changes in climate based on current and projected atmospheric
GHG concentrations and emissions, as well as the related impacts and
risks from climate change that are projected in the absence of GHG
mitigation actions, including this program and other U.S. and global
actions. The TSD was updated and revised based on expert technical
review and public comment as part of EPA's rulemaking process for the
final Endangerment Findings. The key findings synthesized here and the
information throughout the TSD are primarily drawn from the assessment
reports of the Intergovernmental Panel on Climate Change (IPCC), the
U.S. Climate Change Science Program (CCSP), the U.S. Global Change
Research Program (USGCRP), and NRC.\326\
---------------------------------------------------------------------------

    \325\ See Endangerment TSD, Note 10 above.
    \326\ For a complete list of core references from IPCC, USGCRP/
CCSP, NRC and others relied upon for development of the TSD for
EPA's Endangerment and Cause or Contribute Findings See section
1(b), specifically, Table 1.1 of the TSD Docket: EPA-HQ-OAR-2009-
0171-11645.
---------------------------------------------------------------------------

    In May 2010, the NRC published its comprehensive assessment,
``Advancing the Science of Climate Change.'' \327\ It concluded that
``climate change is occurring, is caused largely by human activities,
and poses significant risks for--and in many cases is already
affecting--a broad range of human and natural systems.'' Furthermore,
the NRC stated that this conclusion is based on findings that are
``consistent with the conclusions of recent assessments by the U.S.
Global Change Research Program, the Intergovernmental Panel on Climate
Change's Fourth Assessment Report, and other assessments of the state
of scientific knowledge on climate change.'' These are the same
assessments that served as the primary scientific references underlying
the Administrator's Endangerment Finding. Importantly, this recent NRC
assessment represents another independent and critical inquiry of the
state of climate change science, separate and apart from the previous
IPCC and USGCRP assessments.
---------------------------------------------------------------------------

    \327\ National Research Council (NRC) (2010). Advancing the
Science of Climate Change. National Academy Press. Washington, DC.
---------------------------------------------------------------------------

(1) Observed Trends in Greenhouse Gas Emissions and Concentrations
    The primary long-lived GHGs directly emitted by human activities
include CO2, CH4, N2O, HFCs, PFCs, and
SF6. Greenhouse gases have a warming effect by trapping heat
in the atmosphere that would otherwise escape to space. In 2007, U.S.
GHG emissions were 7,150 teragrams \328\ of CO2 equivalent
\329\ (TgCO2eq). The dominant gas emitted is CO2,
mostly from fossil fuel combustion. Methane is the second largest
component of U.S. emissions, followed by N2O and the
fluorinated gases (HFCs, PFCs, and SF6). Electricity
generation is the largest emitting sector (34 percent of total U.S. GHG
emissions), followed by transportation (27 percent) and industry (19
percent).
---------------------------------------------------------------------------

    \328\ One teragram (Tg) = 1 million metric tons. 1 metric ton =
1,000 kilograms = 1.102 short tons = 2,205 pounds.
    \329\ Long-lived GHGs are compared and summed together on a
CO2-equivalent basis by multiplying each gas by its
global warming potential (GWP), as estimated by IPCC. In accordance
with United Nations Framework Convention on Climate Change (UNFCCC)
reporting procedures, the U.S. quantifies GHG emissions in the
official U.S. greenhouse gas inventory submission to the UNFCCC
using the 100-year time frame values for GWPs established in the
1996 IPCC Second Assessment Report.
---------------------------------------------------------------------------

    Transportation sources under section 202(a) \330\ of the CAA
(passenger cars, light-duty trucks, other trucks and buses,
motorcycles, and passenger cooling) emitted 1,649 TgCO2eq in
2007, representing 23 percent of total U.S. GHG emissions. U.S.
transportation sources under section 202(a) made up 4.3 percent of
total global GHG emissions in 2005,\331\ which, in addition to the
United States as a whole, ranked only behind total GHG emissions from
China, Russia, and India but ahead of Japan, Brazil, Germany, and the
rest of the world's countries. In 2005, total U.S. GHG emissions were
responsible for 18 percent of global emissions, ranking only behind
China, which was responsible for 19 percent of global GHG emissions.
The scope of this final action focuses on GHG emissions under section
202(a) from heavy-duty source categories (see Section II).
---------------------------------------------------------------------------

    \330\ Source categories under Section 202(a) of the CAA are a
subset of source categories considered in the transportation sector
and do not include emissions from non-highway sources such as boats,
rail, aircraft, agricultural equipment, construction/mining
equipment, and other off-road equipment.
    \331\ More recent emission data are available for the United
States and other individual countries, but 2005 is the most recent
year for which data for all countries and all gases are available.
---------------------------------------------------------------------------

    The global atmospheric CO2 concentration has increased
about 38 percent from pre-industrial levels to 2009, and almost all of
the increase is due to anthropogenic emissions. The global atmospheric
concentration of CH4 has increased by 149 percent since pre-
industrial levels (through 2007); and the N2O concentration
has increased by 23 percent (through 2007). The observed concentration
increase in these gases can also be attributed primarily to
anthropogenic emissions. The industrial fluorinated gases, HFCs, PFCs,
and SF6, have relatively low atmospheric concentrations but
the total radiative forcing due to these gases is increasing rapidly;
these gases are almost entirely anthropogenic in origin.
    Historic data show that current atmospheric concentrations of the
two most important directly emitted, long-lived GHGs (CO2
and CH4) are well above the natural range of atmospheric
concentrations compared to at least the last 650,000 years. Atmospheric
GHG concentrations have been increasing because anthropogenic emissions
have been outpacing the rate at which GHGs are removed from the
atmosphere by natural processes over timescales of decades to
centuries.
(2) Observed Effects Associated With Global Elevated Concentrations of
GHGs
    Greenhouse gases, at current (and projected) atmospheric
concentrations, remain well below published exposure thresholds for any
direct adverse health effects and are not expected to pose exposure
risks (i.e., from breathing/inhalation).
    The global average net effect of the increase in atmospheric GHG
concentrations, plus other human activities (e.g., land-use change and
aerosol emissions), on the global energy balance since 1750 has been
one of warming. This total net heating effect, referred to as forcing,
is estimated to be +1.6 (+0.6 to +2.4) watts per square meter (W/m\2\),
with much of the range surrounding this estimate due to uncertainties
about the cooling and warming effects of aerosols. However, as aerosol
forcing has more regional variability than the well-mixed, long-lived
GHGs, the global average might not capture some regional effects. The
combined radiative forcing due to the cumulative (i.e., 1750 to 2005)
increase in atmospheric concentrations of CO2,
CH4, and N2O is estimated to be +2.30 (+2.07 to
+2.53) W/m\2\. The rate of increase in positive radiative forcing due
to these three GHGs during the industrial era is very likely to have
been unprecedented in more than 10,000 years.
    Warming of the climate system is unequivocal, as is now evident
from observations of increases in global average air and ocean
temperatures, widespread melting of snow and ice, and rising global
average sea level. Global mean surface temperatures have risen by 1.3
 0.32 [deg]F (0.74 [deg]C  0.18 [deg]C) over
the last 100 years. Nine of the 10 warmest years on record have
occurred since 2001. Global mean surface temperature was higher during
the last few decades of the 20th century than during any comparable
period during the preceding four centuries.

    Most of the observed increase in global average temperatures since
the mid-20th century is very likely due to the observed increase in
anthropogenic GHG concentrations. Climate model simulations suggest
natural forcing alone (i.e., changes in solar irradiance) cannot
explain the observed warming.
    U.S. temperatures also warmed during the 20th and into the 21st
century; temperatures are now approximately 1.3 [deg]F (0.7 [deg]C)
warmer than at the start of the 20th century, with an increased rate of
warming over the past 30 years. Both the IPCC \332\ and the CCSP
reports attributed recent North American warming to elevated GHG
concentrations. In the CCSP (2008) report,\333\ the authors find that
for North America, ``more than half of this warming [for the period
1951-2006] is likely the result of human-caused greenhouse gas forcing
of climate change.''
---------------------------------------------------------------------------

    \332\ Hegerl, G.C. et al. (2007) Understanding and Attributing
Climate Change. In: Climate Change 2007: The Physical Science Basis.
Contribution of Working Group I to the Fourth Assessment Report of
the Intergovernmental Panel on Climate Change [Solomon, S., D. Qin,
M. Manning, Z. Chen, M. Marquis, K.B. Averyt, M. Tignor, and H.L.
Miller (eds.)]. Cambridge University Press, Cambridge, United
Kingdom and New York, NY, USA.
    \333\ CCSP (2008) Reanalysis of Historical Climate Data for Key
Atmospheric Features: Implications for Attribution of Causes of
Observed Change. A Report by the U.S. Climate Change Science Program
and the Subcommittee on Global Change Research [Randall Dole, Martin
Hoerling, and Siegfried Schubert (eds.)]. National Oceanic and
Atmospheric Administration, National Climatic Data Center,
Asheville, NC, 156 pp.
---------------------------------------------------------------------------

    Observations show that changes are occurring in the amount,
intensity, frequency and type of precipitation. Over the contiguous
United States, total annual precipitation increased by 6.1 percent from
1901 to 2008. It is likely that there have been increases in the number
of heavy precipitation events within many land regions, even in those
where there has been a reduction in total precipitation amount,
consistent with a warming climate.
    There is strong evidence that global sea level gradually rose in
the 20th century and is currently rising at an increased rate. It is
not clear whether the increasing rate of sea level rise is a reflection
of short-term variability or an increase in the longer-term trend.
Nearly all of the Atlantic Ocean shows sea level rise during the last
50 years with the rate of rise reaching a maximum (over 2 millimeters
[mm] per year) in a band along the U.S. east coast running east-
northeast.
    Satellite data since 1979 show that annual average Arctic sea ice
extent has shrunk by 4.1 percent per decade. The size and speed of
recent Arctic summer sea ice loss is highly anomalous relative to the
previous few thousands of years.
    Widespread changes in extreme temperatures have been observed in
the last 50 years across all world regions, including the United
States. Cold days, cold nights, and frost have become less frequent,
while hot days, hot nights, and heat waves have become more frequent.
    Observational evidence from all continents and most oceans shows
that many natural systems are being affected by regional climate
changes, particularly temperature increases. However, directly
attributing specific regional changes in climate to emissions of GHGs
from human activities is difficult, especially for precipitation.
    Ocean CO2 uptake has lowered the average ocean pH
(increased acidity) level by approximately 0.1 since 1750. Consequences
for marine ecosystems can include reduced calcification by shell-
forming organisms, and in the longer term, the dissolution of carbonate
sediments.
    Observations show that climate change is currently affecting U.S.
physical and biological systems in significant ways. The consistency of
these observed changes in physical and biological systems and the
observed significant warming likely cannot be explained entirely due to
natural variability or other confounding non-climate factors.
(3) Projections of Future Climate Change With Continued Increases in
Elevated GHG Concentrations
    Most future scenarios that assume no explicit GHG mitigation
actions (beyond those already enacted) project increasing global GHG
emissions over the century, with climbing GHG concentrations. Carbon
dioxide is expected to remain the dominant anthropogenic GHG over the
course of the 21st century. The radiative forcing associated with the
non-CO2 GHGs is still significant and increasing over time.
    Future warming over the course of the 21st century, even under
scenarios of low-emission growth, is very likely to be greater than
observed warming over the past century. According to climate model
simulations summarized by the IPCC,\334\ through about 2030, the global
warming rate is affected little by the choice of different future
emissions scenarios. By the end of the 21st century, projected average
global warming (compared to average temperature around 1990) varies
significantly depending on the emission scenario and climate
sensitivity assumptions, ranging from 3.2 to 7.2 [deg]F (1.8 to 4.0
[deg]C), with an uncertainty range of 2.0 to 11.5 [deg]F (1.1 to 6.4
[deg]C).
---------------------------------------------------------------------------

    \334\ Meehl, G.A. et al. (2007) Global Climate Projections. In:
Climate Change 2007: The Physical Science Basis. Contribution of
Working Group I to the Fourth Assessment Report of the
Intergovernmental Panel on Climate Change [Solomon, S., D. Qin, M.
Manning, Z. Chen, M. Marquis, K.B. Averyt, M. Tignor and H.L. Miller
(eds.)]. Cambridge University Press, Cambridge, United Kingdom and
New York, NY, USA.
---------------------------------------------------------------------------

    All of the United States is very likely to warm during this
century, and most areas of the United States are expected to warm by
more than the global average. The largest warming is projected to occur
in winter over northern parts of Alaska. In western, central and
eastern regions of North America, the projected warming has less
seasonal variation and is not as large, especially near the coast,
consistent with less warming over the oceans.
    It is very likely that heat waves will become more intense, more
frequent, and longer lasting in a future warm climate, whereas cold
episodes are projected to decrease significantly.
    Increases in the amount of precipitation are very likely in higher
latitudes, while decreases are likely in most subtropical latitudes and
the southwestern United States, continuing observed patterns. The mid-
continental area is expected to experience drying during summer,
indicating a greater risk of drought.
    Intensity of precipitation events is projected to increase in the
United States and other regions of the world. More intense
precipitation is expected to increase the risk of flooding and result
in greater runoff and erosion that has the potential for adverse water
quality effects.
    It is likely that hurricanes will become more intense, with
stronger peak winds and more heavy precipitation associated with
ongoing increases of tropical sea surface temperatures. Frequency
changes in hurricanes are currently too uncertain for confident
projections.
    By the end of the century, global average sea level is projected by
IPCC \335\ to rise between 7.1 and 23 inches (18 and 59 centimeter
[cm]), relative to around 1990, in the absence of increased dynamic ice
sheet loss. Recent rapid changes at the edges of the Greenland and West
Antarctic ice sheets

show acceleration of flow and thinning. While an understanding of these
ice sheet processes is incomplete, their inclusion in models would
likely lead to increased sea level projections for the end of the 21st
century.
---------------------------------------------------------------------------

    \335\ IPCC (2007) Summary for Policymakers. In: Climate Change
2007: The Physical Science Basis. Contribution of Working Group I to
the Fourth Assessment Report of the Intergovernmental Panel on
Climate Change [Solomon, S., D. Qin, M. Manning, Z. Chen, M.
Marquis, K.B. Averyt, M. Tignor and H.L. Miller (eds.)]. Cambridge
University Press, Cambridge, United Kingdom and New York, NY, USA.
---------------------------------------------------------------------------

    Sea ice extent is projected to shrink in the Arctic under all IPCC
emissions scenarios.
(4) Projected Risks and Impacts Associated With Future Climate Change
    Risk to society, ecosystems, and many natural Earth processes
increases with increases in both the rate and magnitude of climate
change. Climate warming may increase the possibility of large, abrupt
regional or global climatic events (e.g., disintegration of the
Greenland Ice Sheet or collapse of the West Antarctic Ice Sheet). The
partial deglaciation of Greenland (and possibly West Antarctica) could
be triggered by a sustained temperature increase of 2 to 7 [deg]F (1 to
4 [deg]C) above 1990 levels. Such warming would cause a 13 to 20 feet
(4 to 6 meter) rise in sea level, which would occur over a time period
of centuries to millennia.
    The CCSP \336\ reports that climate change has the potential to
accentuate the disparities already evident in the American health care
system, as many of the expected health effects are likely to fall
disproportionately on the poor, the elderly, the disabled, and the
uninsured. The IPCC \337\ states with very high confidence that climate
change impacts on human health in U.S. cities will be compounded by
population growth and an aging population.
---------------------------------------------------------------------------

    \336\ Ebi, K.L., J. Balbus, P.L. Kinney, E. Lipp, D. Mills, M.S.
O'Neill, and M. Wilson (2008) Effects of Global Change on Human
Health. In: Analyses of the effects of global change on human health
and welfare and human systems. A Report by the U.S. Climate Change
Science Program and the Subcommittee on Global Change Research.
[Gamble, J.L. (ed.), K.L. Ebi, F.G. Sussman, T.J. Wilbanks,
(Authors)]. U.S. Environmental Protection Agency, Washington, DC,
USA, pp. 2-1 to 2-78.
    \337\ Field, C.B. et al. (2007) North America. In: Climate
Change 2007: Impacts, Adaptation and Vulnerability. Contribution of
Working Group II to the Fourth Assessment Report of the
Intergovernmental Panel on Climate Change [M.L. Parry, O.F.
Canziani, J.P. Palutikof, P.J. van der Linden and C.E. Hanson
(eds.)]. Cambridge University Press, Cambridge, United Kingdom and
New York, NY, USA.
---------------------------------------------------------------------------

    Severe heat waves are projected to intensify in magnitude and
duration over the portions of the United States where these events
already occur, with potential increases in mortality and morbidity,
especially among the elderly, young, and frail.
    Some reduction in the risk of death related to extreme cold is
expected. It is not clear whether reduced mortality from cold will be
greater or less than increased heat-related mortality in the United
States due to climate change.
    Increases in regional ozone pollution relative to ozone levels
without climate change are expected due to higher temperatures and
weaker circulation in the United States and other world cities relative
to air quality levels without climate change. Climate change is
expected to increase regional ozone pollution, with associated risks in
respiratory illnesses and premature death. In addition to human health
effects, tropospheric ozone has significant adverse effects on crop
yields, pasture and forest growth, and species composition. The
directional effect of climate change on ambient particulate matter
levels remains uncertain.
    Within settlements experiencing climate change, certain parts of
the population may be especially vulnerable; these include the poor,
the elderly, those already in poor health, the disabled, those living
alone, and/or indigenous populations dependent on one or a few
resources. Thus, the potential impacts of climate change raise
environmental justice issues.
    The CCSP \338\ concludes that, with increased CO2 and
temperature, the life cycle of grain and oilseed crops will likely
progress more rapidly. But, as temperature rises, these crops will
increasingly begin to experience failure, especially if climate
variability increases and precipitation lessens or becomes more
variable. Furthermore, the marketable yield of many horticultural crops
(e.g., tomatoes, onions, fruits) is very likely to be more sensitive to
climate change than grain and oilseed crops.
---------------------------------------------------------------------------

    \338\ Backlund, P., A. Janetos, D.S. Schimel, J. Hatfield, M.G.
Ryan, S.R. Archer, and D. Lettenmaier (2008) Executive Summary. In:
The Effects of Climate Change on Agriculture, Land Resources, Water
Resources, and Biodiversity in the United States. A Report by the
U.S. Climate Change Science Program and the Subcommittee on Global
Change Research. Washington, DC., USA, 362 pp.
---------------------------------------------------------------------------

    Higher temperatures will very likely reduce livestock production
during the summer season in some areas, but these losses will very
likely be partially offset by warmer temperatures during the winter
season.
    Cold-water fisheries will likely be negatively affected; warm-water
fisheries will generally benefit; and the results for cool-water
fisheries will be mixed, with gains in the northern and losses in the
southern portions of ranges.
    Climate change has very likely increased the size and number of
forest fires, insect outbreaks, and tree mortality in the interior
West, the Southwest, and Alaska, and will continue to do so. Over North
America, forest growth and productivity have been observed to increase
since the middle of the 20th century, in part due to observed climate
change. Rising CO2 will very likely increase photosynthesis
for forests, but the increased photosynthesis will likely only increase
wood production in young forests on fertile soils. The combined effects
of expected increased temperature, CO2, nitrogen deposition,
ozone, and forest disturbance on soil processes and soil carbon storage
remain unclear.
    Coastal communities and habitats will be increasingly stressed by
climate change impacts interacting with development and pollution. Sea
level is rising along much of the U.S. coast, and the rate of change
will very likely increase in the future, exacerbating the impacts of
progressive inundation, storm-surge flooding, and shoreline erosion.
Storm impacts are likely to be more severe, especially along the Gulf
and Atlantic coasts. Salt marshes, other coastal habitats, and
dependent species are threatened by sea level rise, fixed structures
blocking landward migration, and changes in vegetation. Population
growth and rising value of infrastructure in coastal areas increases
vulnerability to climate variability and future climate change.
    Climate change will likely further constrain already over-allocated
water resources in some regions of the United States, increasing
competition among agricultural, municipal, industrial, and ecological
uses. Although water management practices in the United States are
generally advanced, particularly in the West, the reliance on past
conditions as the basis for current and future planning may no longer
be appropriate, as climate change increasingly creates conditions well
outside of historical observations. Rising temperatures will diminish
snowpack and increase evaporation, affecting seasonal availability of
water. In the Great Lakes and major river systems, lower water levels
are likely to exacerbate challenges relating to water quality,
navigation, recreation, hydropower generation, water transfers, and
binational relationships. Decreased water supply and lower water levels
are likely to exacerbate challenges relating to aquatic navigation in
the United States.
    Higher water temperatures, increased precipitation intensity, and
longer periods of low flows will exacerbate many forms of water
pollution, potentially making attainment of water quality goals more
difficult. As waters become warmer, the aquatic life they

now support will be replaced by other species better adapted to warmer
water. In the long term, warmer water and changing flow may result in
deterioration of aquatic ecosystems.
    Ocean acidification is projected to continue, resulting in the
reduced biological production of marine calcifiers, including corals.
    Climate change is likely to affect U.S. energy use and energy
production and physical and institutional infrastructures. It will also
likely interact with and possibly exacerbate ongoing environmental
change and environmental pressures in settlements, particularly in
Alaska where indigenous communities are facing major environmental and
cultural impacts. The U.S. energy sector, which relies heavily on water
for hydropower and cooling capacity, may be adversely impacted by
changes to water supply and quality in reservoirs and other water
bodies. Water infrastructure, including drinking water and wastewater
treatment plants, and sewer and stormwater management systems, will be
at greater risk of flooding, sea level rise and storm surge, low flows,
and other factors that could impair performance.
    Disturbances such as wildfires and insect outbreaks are increasing
in the United States and are likely to intensify in a warmer future
with warmer winters, drier soils, and longer growing seasons. Although
recent climate trends have increased vegetation growth, continuing
increases in disturbances are likely to limit carbon storage,
facilitate invasive species, and disrupt ecosystem services.
    Over the 21st century, changes in climate will cause species to
shift north and to higher elevations and fundamentally rearrange U.S.
ecosystems. Differential capacities for range shifts and constraints
from development, habitat fragmentation, invasive species, and broken
ecological connections will alter ecosystem structure, function, and
services.
(5) Present and Projected U.S. Regional Climate Change Impacts
    Climate change impacts will vary in nature and magnitude across
different regions of the United States.
    Sustained high summer temperatures, heat waves, and declining air
quality are projected in the Northeast,\339\ Southeast,\340\
Southwest,\341\ and Midwest.\342\ Projected climate change would
continue to cause loss of sea ice, glacier retreat, permafrost thawing,
and coastal erosion in Alaska.
---------------------------------------------------------------------------

    \339\ Northeast includes West Virginia, Maryland, Delaware,
Pennsylvania, New Jersey, New York, Connecticut, Rhode Island,
Massachusetts, Vermont, New Hampshire, and Maine.
    \340\ Southeast includes Kentucky, Virginia, Arkansas,
Tennessee, North Carolina, South Carolina, southeast Texas,
Louisiana, Mississippi, Alabama, Georgia, and Florida.
    \341\ Southwest includes California, Nevada, Utah, western
Colorado, Arizona, New Mexico (except the extreme eastern section),
and southwest Texas.
    \342\ The Midwest includes Minnesota, Wisconsin, Michigan, Iowa,
Illinois, Indiana, Ohio, and Missouri.
---------------------------------------------------------------------------

    Reduced snowpack, earlier spring snowmelt, and increased likelihood
of seasonal summer droughts are projected in the Northeast,
Northwest,\343\ and Alaska. More severe, sustained droughts and water
scarcity are projected in the Southeast, Great Plains,\344\ and
Southwest.
---------------------------------------------------------------------------

    \343\ The Northwest includes Washington, Idaho, western Montana,
and Oregon.
    \344\ The Great Plains includes central and eastern Montana,
North Dakota, South Dakota, Wyoming, Nebraska, eastern Colorado,
Kansas, extreme eastern New Mexico, central Texas, and Oklahoma.
---------------------------------------------------------------------------

    The Southeast, Midwest, and Northwest in particular are expected to
be impacted by an increased frequency of heavy downpours and greater
flood risk.
    Ecosystems of the Southeast, Midwest, Great Plains, Southwest,
Northwest, and Alaska are expected to experience altered distribution
of native species (including local extinctions), more frequent and
intense wildfires, and an increase in insect pest outbreaks and
invasive species.
    Sea level rise is expected to increase storm surge height and
strength, flooding, erosion, and wetland loss along the coasts,
particularly in the Northeast, Southeast, and islands.
    Warmer water temperatures and ocean acidification are expected to
degrade important aquatic resources of islands and coasts such as coral
reefs and fisheries.
    A longer growing season, low levels of warming, and fertilization
effects of carbon dioxide may benefit certain crop species and forests,
particularly in the Northeast and Alaska. Projected summer rainfall
increases in the Pacific islands may augment limited freshwater
supplies. Cold-related mortality is projected to decrease, especially
in the Southeast. In the Midwest in particular, heating oil demand and
snow-related traffic accidents are expected to decrease.
    Climate change impacts in certain regions of the world may
exacerbate problems that raise humanitarian, trade, and national
security issues for the United States. The IPCC \345\ identifies the
most vulnerable world regions as the Arctic, because of the effects of
high rates of projected warming on natural systems; Africa, especially
the sub-Saharan region, because of current low adaptive capacity as
well as climate change; small islands, due to high exposure of
population and infrastructure to risk of sea level rise and increased
storm surge; and Asian mega-deltas, such as the Ganges-Brahmaputra and
the Zhujiang, due to large populations and high exposure to sea level
rise, storm surge and river flooding. Climate change has been described
as a potential threat multiplier with regard to national security
issues.
---------------------------------------------------------------------------

    \345\ Parry, M.L. et al. (2007) Technical Summary. In: Climate
Change 2007: Impacts, Adaptation and Vulnerability. Contribution of
Working Group II to the Fourth Assessment Report of the
Intergovernmental Panel on Climate Change [M.L. Parry, O.F.
Canziani, J.P. Palutikof, P.J. van der Linden, and C.E. Hanson
(eds.)], Cambridge University Press, Cambridge, United Kingdom, pp.
23S78.
---------------------------------------------------------------------------

E. Changes in Atmospheric CO2 Concentrations, Global Mean
Temperature, Sea Level Rise, and Ocean pH Associated With the Program's
GHG Emissions Reductions

    EPA examined \346\ the reductions in CO2 and other GHGs
associated with this rulemaking and analyzed the projected effects on
atmospheric CO2 concentrations, global mean surface
temperature, sea level rise, and ocean pH which are common variables
used as indicators of climate change. The analysis projects that the
preferred alternative of this program will reduce atmospheric
concentrations of CO2, global climate warming and sea level
rise relative to the reference case. Although the projected reductions
and improvements are small in comparison to the total projected climate
change, they are quantifiable, directionally consistent, and will
contribute to reducing the risks associated with climate change.
Climate change is a global phenomenon and EPA recognizes that this one
national action alone will not prevent it: EPA notes this would be true
for any given GHG mitigation action when taken alone. EPA also notes
that a substantial portion of CO2 emitted into the
atmosphere is not removed by natural processes for millennia, and
therefore each unit of CO2 not emitted into the atmosphere
due to this program

avoids essentially permanent climate change on centennial time scales.
The heavy-duty program makes a significant contribution towards
addressing the challenge by producing substantial reductions in
greenhouse gas emissions from a particularly large and important source
of emissions. As the Supreme Court recognized in State of Massachusetts
v. EPA, [A]agencies, like legislatures, do not generally resolve
massive problems like climate change in one fell regulatory swoop. 549
U.S. 497, 524 (2008). They instead whittle away at them over time. Id.
---------------------------------------------------------------------------

    \346\ Using the Model for the Assessment of Greenhouse Gas
Induced Climate Change (MAGICC) 5.3v2, http://www.cgd.ucar.edu/cas/wigley/magicc/), EPA estimated the effects of this rulemaking's
greenhouse gas emissions reductions on global mean temperature and
sea level. Please refer to Chapter 8.4 of the RIA for additional
information.
---------------------------------------------------------------------------

    EPA determines that the projected reductions in atmospheric
CO2, global mean temperature and sea level rise are
meaningful in the context of this final action. In addition, EPA has
conducted an analysis to evaluate the projected changes in ocean pH in
the context of the changes in emissions from this rulemaking. The
results of the analysis demonstrate that relative to the reference
case, projected atmospheric CO2 concentrations are estimated
to be reduced by 0.691 to 0.787 part per million by volume (ppmv),
global mean temperature is estimated to be reduced by 0.0017 to
0.0042[deg]C, and sea-level rise is projected to be reduced by
approximately 0.017-0.040 cm by 2100, based on a range of climate
sensitivities. The analysis also demonstrates that ocean pH will
increase by 0.0003 pH units by 2100 relative to the reference case.
(1) Estimated Projected Reductions in Atmospheric CO2
Concentration, Global Mean Surface Temperatures, Sea Level Rise, and
Ocean pH
    EPA estimated changes in the atmospheric CO2
concentration, global mean temperature, and sea level rise out to 2100
resulting from the emissions reductions in this rulemaking using the
GCAM (Global Change Assessment Model, formerly MiniCAM), integrated
assessment model \347\ coupled with the Model for the Assessment of
Greenhouse Gas Induced Climate Change (MAGICC, version 5.3v2).\348\
GCAM was used to create the globally and temporally consistent set of
climate relevant variables required for running MAGICC. MAGICC was then
used to estimate the projected change in these variables over time.
Given the magnitude of the estimated emissions reductions associated
with this action, a simple climate model such as MAGICC is reasonable
for estimating the atmospheric and climate response. This widely-used,
peer reviewed modeling tool was also used to project temperature and
sea level rise under different emissions scenarios in the Third and
Fourth Assessments of the IPCC.
---------------------------------------------------------------------------

    \347\ GCAM is a long-term, global integrated assessment model of
energy, economy, agriculture and land use, that considers the
sources of emissions of a suite of GHG's, emitted in 14 globally
disaggregated regions, the fate of emissions to the atmosphere, and
the consequences of changing concentrations of greenhouse related
gases for climate change. GCAM begins with a representation of
demographic and economic developments in each region and combines
these with assumptions about technology development to describe an
internally consistent representation of energy, agriculture, land-
use, and economic developments that in turn shape global emissions.
    Brenkert A, S. Smith, S. Kim, and H. Pitcher, 2003: Model
Documentation for the MiniCAM. PNNL-14337, Pacific Northwest
National Laboratory, Richland, Washington.
    \348\ Wigley, T.M.L. 2008. MAGICC 5.3.v2 User Manual. UCAR--
Climate and Global Dynamics Division, Boulder, Colorado. http://www.cgd.ucar.edu/cas/wigley/magicc/.
---------------------------------------------------------------------------

    The integrated impact of the following pollutant and greenhouse gas
emissions changes are considered: CO2, CH4,
N2O, HFC-134a, NOX, CO2 and
SO2, and volatile organic compounds (VOC). For
CO2, CH4, HFC-134a, and N2O an annual
time-series of (upstream + downstream) emissions reductions estimated
from the rulemaking were input directly. The GHG emissions reductions,
from Section VI.C, were applied as net reductions to a global reference
case (or baseline) emissions scenario in GCAM to generate an emissions
scenario specific to this rulemaking. For CO, VOCs, SO2, and
NOX, emissions reductions were estimated for 2018, 2030, and
2050 (provided in Section VII.A). EPA then linearly scaled emissions
reductions for these gases between a zero input value in 2013 and the
value supplied for 2018 to produce the reductions for 2014-2018. A
similar scaling was used for 2019-2029 and 2031-2050. The emissions
reductions past 2050 for all gases were scaled with total U.S. road
transportation fuel consumption from the GCAM reference scenario. Road
transport fuel consumption past 2050 does not change significantly and
thus emissions reductions remain relatively constant from 2050 through
2100. Specific details about the GCAM reference case scenario can be
found in Chapter 8.4 of the RIA that accompanies this preamble.
    MAGICC calculates the forcing response at the global scale from
changes in atmospheric concentrations of CO2,
CH4, N2O, HFCs, and tropospheric ozone. It also
includes the effects of temperature changes on stratospheric ozone and
the effects of CH4 emissions on stratospheric water vapor.
Changes in CH4, NOX, VOC, and CO emissions affect
both O3 concentrations and CH4 concentrations.
MAGICC includes the relative climate forcing effects of changes in
sulfate concentrations due to changing SO2 emissions,
including both the direct effect of sulfate particles and the indirect
effects related to cloud interactions. However, MAGICC does not
calculate the effect of changes in concentrations of other aerosols
such as nitrates, black carbon, or organic carbon, making the
assumption that the sulfate cooling effect is a proxy for the sum of
all the aerosol effects. Therefore, the climate effects of changes in
PM2.5 emissions and precursors (besides SO2)
which are presented in the RIA Chapter 5 were not included in the
calculations in this section. MAGICC also calculates all climate
effects at the global scale. This global scale captures the climate
effects of the long-lived, well-mixed greenhouse gases, but does not
address the fact that short-lived climate forcers such as aerosols and
ozone can have effects that vary with location and timing of emissions.
Black carbon in particular is known to cause a positive forcing or
warming effect by absorbing incoming solar radiation, but there are
uncertainties about the magnitude of that warming effect and the
interaction of black carbon (and other co-emitted aerosol species) with
clouds. While black carbon is likely to be an important contributor to
climate change, it would be premature to include quantification of
black carbon climate impacts in an analysis of the final standards at
this time.
    Changes in atmospheric CO2 concentration, global mean
temperature, and sea level rise for both the reference case and the
emissions scenarios associated with this action were computed using
MAGICC. To calculate the reductions in the atmospheric CO2
concentrations as well as in temperature and sea level resulting from
this action, the output from the policy scenario associated with the
preferred approach of this action was subtracted from an existing
Global Change Assessment Model (GCAM, formerly MiniCAM) reference
emission scenario. To capture some key uncertainties in the climate
system with the MAGICC model, changes in atmospheric CO2,
global mean temperature and sea level rise were projected across the
most current IPCC range of climate sensitivities, from 1.5 [deg]C to
6.0 [deg]C.\349\ This range reflects

the uncertainty for equilibrium climate sensitivity for how much global
mean temperature would rise if the concentration of carbon dioxide in
the atmosphere were to double. The information for this range come from
constraints from past climate change on various time scales, and the
spread of results for climate sensitivity from ensembles of
models.\350\ Details about this modeling analysis can be found in the
RIA Chapter 8.4.
---------------------------------------------------------------------------

    \349\ In IPCC reports, equilibrium climate sensitivity refers to
the equilibrium change in the annual mean global surface temperature
following a doubling of the atmospheric equivalent carbon dioxide
concentration. The IPCC states that climate sensitivity is
``likely'' to be in the range of 2 [deg]C to 4.5 [deg]C, ``very
unlikely'' to be less than 1.5 [deg]C, and ``values substantially
higher than 4.5 [deg]C cannot be excluded.'' IPCC WGI, 2007, Climate
Change 2007--The Physical Science Basis, Contribution of Working
Group I to the Fourth Assessment Report of the IPCC, http://www.ipcc.ch/.
    \350\ Meehl, G.A. et al. (2007) Global Climate Projections. In:
Climate Change 2007: The Physical Science Basis. Contribution of
Working Group I to the Fourth Assessment Report of the
Intergovernmental Panel on Climate Change [Solomon, S., D. Qin, M.
Manning, Z. Chen, M. Marquis, K.B. Averyt, M. Tignor and H.L. Miller
(eds.)]. Cambridge University Press, Cambridge, United Kingdom and
New York, NY, USA.
---------------------------------------------------------------------------

    The results of this modeling, summarized in Table VI-8, show small,
but quantifiable, reductions in atmospheric CO2
concentrations, projected global mean temperature and sea level
resulting from this action, across all climate sensitivities. As a
result of the emission reductions from the final standards for this
action, relative to the reference case the atmospheric CO2
concentration is projected to be reduced by 0.691-0.787 ppmv, the
global mean temperature is projected to be reduced by approximately
0.0017-0.0042 [deg]C by 2100, and global mean sea level rise is
projected to be reduced by approximately 0.017-0.040 cm by 2100. The
range of reductions in global mean temperature and sea level rise is
larger than that for CO2 concentrations because
CO2 concentrations are only weakly coupled to climate
sensitivity through the dependence on temperature of the rate of ocean
absorption of CO2, whereas the magnitude of temperature
change response to CO2 changes (and therefore sea level
rise) is more tightly coupled to climate sensitivity in the MAGICC
model.

 Table VI-8--Impact of GHG Emissions Reductions on Projected Changes in Global Climate Associated With the Final
                    Rulemaking (Based on a Range of Climate Sensitivities From 1.5-6 [deg]C)
----------------------------------------------------------------------------------------------------------------
                Variable                       Units           Year                  Projected change
----------------------------------------------------------------------------------------------------------------
Atmospheric CO2 Concentration...........            ppmv            2100  -0.691 to -0.787.
Global Mean Surface Temperature.........          [deg]C            2100  -0.0017 to -0.0042.
Sea Level Rise..........................              cm            2100  -0.017 to -0.040.
Ocean pH................................        pH units            2100  0.0003 \a\.
----------------------------------------------------------------------------------------------------------------
Note:
\a\ The value for projected change in ocean pH is based on a climate sensitivity of 3.0.

    The projected reductions are small relative to the change in
temperature (1.8-4.8 [deg]C), sea level rise (27--51 cm), and ocean
acidity (-0.30 pH units) from 1990 to 2100 from the MAGICC simulations
for the GCAM reference case. However, this is to be expected given the
magnitude of emissions reductions expected from the program in the
context of global emissions. This uncertainty range does not include
the effects of uncertainty in future emissions. It should also be noted
that the calculations in MAGICC do not include the possible effects of
accelerated ice flow in Greenland and/or Antarctica: the recent NRC
report estimated a likely sea level increase for the A1B SRES scenario
of 0.5 to 1.0 meters.\351\ Further discussion of EPA's modeling
analysis is found in the RIA, Chapter 8.
---------------------------------------------------------------------------

    \351\ National Research Council, 2011. Climate Stabilization
Targets: Emissions, Concentrations, and Impacts over Decades to
Millenia. Washington, DC: National Academies Press.
---------------------------------------------------------------------------

    EPA used the Program CO2SYS,\352\ version 1.05 to estimate
projected changes in ocean pH for tropical waters based on the
atmospheric CO2 concentration change (reduction) resulting
from this action. The program performs calculations relating parameters
of the CO2 system in seawater. EPA used the program to
calculate ocean pH as a function of atmospheric CO2
concentrations, among other specified input conditions. Based on the
projected atmospheric CO2 concentration reductions resulting
from this action, the program calculates an increase in ocean pH of
0.0003 pH units in 2100 relative to the reference case (compared to a
decrease of 0.3 pH units from 1990 to 2100 in the reference case).
Thus, this analysis indicates the projected decrease in atmospheric
CO2 concentrations from the program will result in an
increase in ocean pH. For additional validation, results were generated
using different known constants from the literature. A comprehensive
discussion of the modeling analysis associated with ocean pH is
provided in the RIA, Chapter 8.
---------------------------------------------------------------------------

    \352\ Lewis, E., and D. W. R. Wallace. 1998. Program Developed
for CO2 System Calculations. ORNL/CDIAC-105. Carbon
Dioxide Information Analysis Center, Oak Ridge National Laboratory,
U.S. Department of Energy, Oak Ridge, Tennessee.
---------------------------------------------------------------------------

(2) Program's Effect on Climate
    As a substantial portion of CO2 emitted into the
atmosphere is not removed by natural processes for millennia, each unit
of CO2 not emitted into the atmosphere avoids essentially
permanent climate change on centennial time scales. Reductions in
emissions in the near-term are important in determining long-term
climate stabilization and associated impacts experienced not just over
the next decades but in the coming centuries and millennia.\353\ Though
the magnitude of the avoided climate change projected here is small in
comparison to the total projected changes, these reductions represent a
reduction in the adverse risks associated with climate change (though
these risks were not formally estimated for this action) across a range
of equilibrium climate sensitivities.
---------------------------------------------------------------------------

    \353\ See NRC 2011, Note 351.
---------------------------------------------------------------------------

    EPA's analysis of the program's impact on global climate conditions
is intended to quantify these potential reductions using the best
available science. EPA's modeling results show repeatable, consistent
reductions relative to the reference case in changes of CO2
concentration, temperature, sea-level rise, and ocean pH over the next
century.

VII. How will this final action impact non-GHG emissions and their
associated effects?

A. Emissions Inventory Impacts

(1) Upstream Impacts of the Program
    Increasing efficiency in heavy-duty vehicles will result in reduced
fuel demand and therefore reductions in the emissions associated with
all processes involved in getting petroleum to the pump. These
projected upstream emission impacts on criteria pollutants

are summarized in Table VII-1. Table VII-2 shows the corresponding
projected impacts on upstream air toxic emissions in 2030.

 Table VII-1--Overall Estimated Upstream Impacts on Criteria Pollutants for Calendar Years 2018, 2030, and 2050
                                                  [Short tons]
----------------------------------------------------------------------------------------------------------------
              Calendar year                      NOX               VOC               CO               PM2.5
----------------------------------------------------------------------------------------------------------------
2018....................................            -6,475            -1,765            -2,217              -971
2030....................................            -9,975            -4,367            -3,331            -1,379
2050....................................           -14,243            -6,379            -4,785            -1,998
----------------------------------------------------------------------------------------------------------------

                          Table VII-2--Overall Estimated Upstream Impacts on AIR TOXICS for Calendar Years 2018, 2030, and 2050
                                                                      [Short tons]
--------------------------------------------------------------------------------------------------------------------------------------------------------
                         Calendar year                               Benzene        1,3-butadiene     Formaldehyde      Acetaldehyde        Acrolein
--------------------------------------------------------------------------------------------------------------------------------------------------------
2018..........................................................               -12              -0.6               -12                -1              -0.2
2030..........................................................               -19              -0.9               -26                -3              -0.5
2050..........................................................               -28              -1.2               -35                -5              -0.6
--------------------------------------------------------------------------------------------------------------------------------------------------------

    To project these impacts, EPA estimated the impact of reduced
petroleum volumes on the extraction and transportation of crude oil as
well as the production and distribution of finished gasoline and
diesel. For the purpose of assessing domestic-only emission reductions
it was necessary to estimate the fraction of fuel savings attributable
to domestic finished gasoline and diesel, and of this fuel what
fraction is produced from domestic crude. For this analysis EPA
estimated that 50 percent of fuel savings is attributable to domestic
finished gasoline and diesel and that 90 percent of this gasoline and
diesel originated from imported crude. Emission factors for most
upstream emission sources are based on the GREET1.8 model, developed by
DOE's Argonne National Laboratory but in some cases the GREET values
were modified or updated by EPA to be consistent with the National
Emission Inventory. These updates are consistent with those used for
the upstream analysis included in the Light-Duty GHG rulemaking. More
information on the development of the emission factors used in this
analysis can be found in RIA chapter 5.
(2) Downstream Impacts of the Program
    While these final rules do not regulate non-GHG pollutants, EPA
expects reductions in downstream emissions of most non-GHG pollutants.
These pollutants include NOX, SO2, VOC, CO, and
PM. The primary reasons for this are the improvements in road load
(aerodynamics and tire rolling resistance) under the program and the
agency's anticipation of increased use of APUs in combination tractors
for GHG reduction purposes during extended idling. APUs exhibit
different non-GHG emissions characteristics compared to the on-road
engines they would replace during extended idling. Another reason is
that emissions from certain pollutants (e.g., SO2) are
proportional to fuel consumption. For vehicle types not affected by
road load improvements, non-GHG emissions may increase very slightly
due to VMT rebound. EPA used MOVES to determine non-GHG emissions
inventories for baseline and control cases. Further information about
the MOVES analysis is available in Section VI and RIA chapter 5. The
improvements in road load, use of APUs, and VMT rebound were included
in the MOVES runs and post-processing. Table VII-3 summarizes the
downstream criteria pollutant impacts of this program. Most of the
impacts shown are through projected increased APU use. Because APUs are
required to meet much less stringent PM standards than on-road engines,
the projected widespread use of APUs leads to higher PM2.5.
Table VII-4 summarizes the downstream air toxics impacts of this
program.

                                        Table VII-3--Overall Estimated Downstream Impacts on Criteria Pollutants
                                                                      [Short tons]
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                                Downstream PM2.5
                         Calendar year                           Downstream NOX    Downstream VOC    Downstream SO2     Downstream CO           a
--------------------------------------------------------------------------------------------------------------------------------------------------------
2018..........................................................          -107,135           -12,951              -145           -25,614               803
2030..........................................................          -235,046           -25,502              -423           -52,212             1,751
2050..........................................................          -326,413           -35,126              -614           -72,049             2,441
--------------------------------------------------------------------------------------------------------------------------------------------------------
Note:
a Positive number means emissions would increase from baseline to control case. PM2.5 from tire wear and brake wear is included.

                                             Table VII-4--Overall Estimated Downstream Impacts on Air Toxics
                                                                      [Short tons]
--------------------------------------------------------------------------------------------------------------------------------------------------------
                         Calendar year                               Benzene        1,3-butadiene     Formaldehyde      Acetaldehyde        Acrolein
--------------------------------------------------------------------------------------------------------------------------------------------------------
2018..........................................................              -158              -0.3            -2,853              -871              -120
2030..........................................................              -341               0.4            -6,255            -1,908              -263

2050..........................................................              -472               0.8            -8,689            -2,650              -365
--------------------------------------------------------------------------------------------------------------------------------------------------------

(3) Total Impacts of the Program
    As shown in Table VII-5 and Table VII-6, the agencies estimate that
this program would result in reductions of NOX, VOC, CO, PM,
and air toxics. For NOX, VOC, and CO, much of the net
reductions are realized through the use of APUs, which emit these
pollutants at a lower rate than on-road engines during extended idle
operation. Additional reductions are achieved in all pollutants through
reduced road load (improved aerodynamics and tire rolling resistance),
which reduces the amount of work required to travel a given distance.
For SOX, downstream emissions are roughly proportional to
fuel consumption; therefore a decrease is seen in both upstream and
downstream sources. The downstream increase in PM2.5 due to
APU use is mostly negated by upstream PM2.5 reductions,
though our calculations show a slight net increase in 2030 and
2050.\354\
---------------------------------------------------------------------------

    \354\ Although the net impact is small when aggregated to the
national level, it is unlikely that the geographic location of
increases in downstream PM2.5 emissions will coincide
with the location of decreases in upstream PM2.5
emissions. Impacts of the emissions changes are included in the air
quality modeling, discussed in Section VII.D of this preamble and in
Chapter 8 of the RIA.

                             Table VII-5--Overall Estimated Total Impacts (Upstream Plus Downstream) on Criteria Pollutants
                                [Results are shown in both short tons and percent change from baseline to control case.]
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                  NOX                      VOC                   SO2                   CO                   PM2.5
                                      ------------------------------------------------------------------------------------------------------------------
                  CY                                                short                 short                 short                 short
                                         short tons        %         tons        %         tons        %         tons        %         tons        %
--------------------------------------------------------------------------------------------------------------------------------------------------------
2018.................................        -113,610       -6.2    -14,715       -5.6     -4,566       -4.5    -27,832       -1.0       -167       -0.2
2030.................................        -245,129      -21.0    -29,932      -16.0     -6,888      -10.1    -55,579       -2.1        356       10.1
2050.................................        -340,656      -23.7    -41,506      -18.3     -9,857      -11.0    -76,834       -2.2        443       10.1
--------------------------------------------------------------------------------------------------------------------------------------------------------

                                  Table VII-6--Overall Estimated Total Impacts on Air Toxics (Upstream Plus Downstream)
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                   Benzene            1,3-butadiene         Formaldehyde          Acetaldehyde            Acrolein
                                           -------------------------------------------------------------------------------------------------------------
                    CY                        short                 short                 short                 short                 short
                                               tons        %         tons        %         tons        %         tons        %         tons        %
--------------------------------------------------------------------------------------------------------------------------------------------------------
2018......................................       -170       -4.8       -0.9       -0.1     -2,865      -18.3       -873      -13.9     -120.0      -12.4
2030......................................       -359      -15.0       -0.5       -0.1     -6,282      -46.2     -1,912      -40.2     -263.0      -40.0
2050......................................       -500      -17.4       -0.4       -0.1     -8,725      -49.5     -2,655      -44.2     -365.4      -44.5
--------------------------------------------------------------------------------------------------------------------------------------------------------

B. Health Effects of Non-GHG Pollutants

    In this section we discuss health effects associated with exposure
to some of the criteria and air toxic pollutants impacted by the final
heavy-duty vehicle standards.
(1) Particulate Matter
(a) Background
    Particulate matter is a generic term for 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. Since
1987, EPA has delineated that subset of inhalable particles small
enough to penetrate to the thoracic region (including the
tracheobronchial and alveolar regions) of the respiratory tract
(referred to as thoracic particles). Current National Ambient Air
Quality Standards (NAAQS) use PM2.5 as the indicator for
fine particles (with PM2.5 referring to particles with a
nominal mean aerodynamic diameter less than or equal to 2.5 [mu]m), and
use PM10 as the indicator for purposes of regulating the
coarse fraction of PM10 (referred to as thoracic coarse
particles or coarse-fraction particles; generally including particles
with a nominal mean aerodynamic diameter greater than 2.5 [mu]m and
less than or equal to 10 [mu]m, or PM10-2.5). Ultrafine
particles are a subset of fine particles, generally less than 100
nanometers (0.1 [mu]m) in aerodynamic diameter.
    Fine particles are produced primarily by combustion processes and
by transformations of gaseous emissions (e.g., SOX,
NOX, and VOC) in the atmosphere. The chemical and physical
properties of PM2.5 may vary greatly with time, region,
meteorology, and source category. Thus, PM2.5 may include a
complex mixture of different pollutants including sulfates, nitrates,
organic compounds, elemental carbon and metal compounds. These
particles can remain in the atmosphere for days to weeks and travel
hundreds to thousands of kilometers.
(b) 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
EPA's Integrated Science Assessment for Particulate Matter (ISA).\355\
Further discussion of health effects associated with PM can also be
found in the RIA for this final action. The ISA summarizes evidence
associated with PM2.5, PM10-2.5, and ultrafine
particles.
---------------------------------------------------------------------------

    \355\ U.S. EPA (2009) Integrated Science Assessment for
Particulate Matter (Final Report). U.S. Environmental Protection
Agency, Washington, DC, EPA/600/R-08/139F, Docket EPA-HQ-OAR-2010-
0162.
---------------------------------------------------------------------------

    The ISA concludes that health effects associated with short-term
exposures (hours to days) to ambient PM2.5 include
mortality, cardiovascular effects, such as

altered vasomotor function and hospital admissions and emergency
department visits for ischemic heart disease and congestive heart
failure, and respiratory effects, such as exacerbation of asthma
symptoms in children and hospital admissions and emergency department
visits for chronic obstructive pulmonary disease and respiratory
infections.\356\ The ISA notes that long-term exposure to
PM2.5 (months to years) is associated with the development/
progression of cardiovascular disease, premature mortality, and
respiratory effects, including reduced lung function growth, increased
respiratory symptoms, and asthma development.\357\ The ISA concludes
that the currently available scientific evidence from epidemiologic,
controlled human exposure, and toxicological studies supports a causal
association between short- and long-term exposures to PM2.5
and cardiovascular effects and mortality. Furthermore, the ISA
concludes that the collective evidence supports likely causal
associations between short- and long-term PM2.5 exposures
and respiratory effects. The ISA also concludes that the scientific
evidence is suggestive of a causal association for reproductive and
developmental effects and cancer, mutagenicity, and genotoxicity and
long-term exposure to PM2.5.\358\
---------------------------------------------------------------------------

    \356\ See U.S. EPA, 2009 Final PM ISA, Note 355, at Section
<IP_ADDRESS>.
    \357\ See U.S. EPA 2009 Final PM ISA, Note 355, at page 2-12,
Sections <IP_ADDRESS> and <IP_ADDRESS>.
    \358\ See U.S. EPA 2009 Final PM ISA, Note 355, at Section
2.3.2.
---------------------------------------------------------------------------

    For PM10-2.5, the ISA concludes that the current
evidence is suggestive of a causal relationship between short-term
exposures and cardiovascular effects, such as hospitalization for
ischemic heart disease. There is also suggestive evidence of a causal
relationship between short-term PM10-2.5 exposure and
mortality and respiratory effects. Data are inadequate to draw
conclusions regarding the health effects associated with long-term
exposure to PM10-2.5.\359\
---------------------------------------------------------------------------

    \359\ See U.S. EPA 2009 Final PM ISA, Note 355, at Section
2.3.4, Table 2-6.
---------------------------------------------------------------------------

    For ultrafine particles, the ISA concludes that there is suggestive
evidence of a causal relationship between short-term exposures and
cardiovascular effects, such as changes in heart rhythm and blood
vessel function. It also concludes that there is suggestive evidence of
association between short-term exposure to ultrafine particles and
respiratory effects. Data are inadequate to draw conclusions regarding
the health effects associated with long-term exposure to ultrafine
particles.\360\
---------------------------------------------------------------------------

    \360\ See U.S. EPA 2009 Final PM ISA, Note 355, at Section
2.3.5, Table 2-6.
---------------------------------------------------------------------------

(2) Ozone
(a) Background
    Ground-level ozone pollution is typically formed by the reaction of
VOC and NOX in the lower atmosphere in the presence of
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.
    The science of ozone formation, transport, and accumulation is
complex. 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 occurs
on a single high-temperature day. Ozone can be transported hundreds of
miles downwind from precursor emissions, resulting in elevated ozone
levels even in areas with low local VOC or NOX emissions.
(b) Health Effects of Ozone
    The health and welfare effects of ozone are well documented and are
assessed in EPA's 2006 Air Quality Criteria Document and 2007 Staff
Paper.361 362 People who are more susceptible to effects
associated with exposure to ozone can include children, the elderly,
and individuals with respiratory disease such as asthma. Those with
greater exposures to ozone, for instance due to time spent outdoors
(e.g., children and outdoor workers), are of particular concern. Ozone
can irritate the respiratory system, causing coughing, throat
irritation, and breathing discomfort. Ozone can reduce lung function
and cause pulmonary inflammation in healthy individuals. Ozone can also
aggravate asthma, leading to more asthma attacks that require medical
attention and/or the use of additional medication. Thus, ambient ozone
may cause both healthy and asthmatic individuals to limit their outdoor
activities. In addition, there is suggestive evidence of a contribution
of ozone to cardiovascular-related morbidity and highly suggestive
evidence that short-term ozone exposure directly or indirectly
contributes to non-accidental and cardiopulmonary-related mortality,
but additional research is needed to clarify the underlying mechanisms
causing these effects. In a recent report on the estimation of ozone-
related premature mortality published by NRC, a panel of experts and
reviewers concluded that short-term exposure to ambient ozone is likely
to contribute to premature deaths and that ozone-related mortality
should be included in estimates of the health benefits of reducing
ozone exposure.\363\ Animal toxicological evidence indicates that with
repeated exposure, ozone can inflame and damage the lining of the
lungs, which may lead to permanent changes in lung tissue and
irreversible reductions in lung function. The respiratory effects
observed in controlled human exposure studies and animal studies are
coherent with the evidence from epidemiologic studies supporting a
causal relationship between acute ambient ozone exposures and increased
respiratory-related emergency room visits and hospitalizations in the
warm season. In addition, there is suggestive evidence of a
contribution of ozone to cardiovascular-related morbidity and non-
accidental and cardiopulmonary mortality.
---------------------------------------------------------------------------

    \361\ U.S. EPA. (2006). Air Quality Criteria for Ozone and
Related Photochemical Oxidants (Final). EPA/600/R-05/004aF-cF.
Washington, DC: U.S. EPA. Docket EPA-HQ-OAR-2010-0162.
    \362\ U.S. EPA. (2007). Review of the National Ambient Air
Quality Standards for Ozone: Policy Assessment of Scientific and
Technical Information, OAQPS Staff Paper. EPA-452/R-07-003.
Washington, DC, U.S. EPA. Docket EPA-HQ-OAR-2010-0162.
    \363\ National Research Council (NRC), 2008. Estimating
Mortality Risk Reduction and Economic Benefits from Controlling
Ozone Air Pollution. The National Academies Press: Washington, DC
Docket EPA-HQ-OAR-2010-0162.
---------------------------------------------------------------------------

(3) Nitrogen Oxides and Sulfur Oxides
(a) Background
    Nitrogen dioxide (NO2) is a member of the NOX
family of gases. Most NO2 is formed in the air through the
oxidation of nitric oxide (NO) emitted when fuel is burned at a high
temperature. SO2, a member of the sulfur oxide
(SOX) family of gases, is formed from burning fuels
containing sulfur (e.g., coal or oil derived), extracting gasoline from
oil, or extracting metals from ore.
    SO2 and NO2 can dissolve in water droplets
and further oxidize to form sulfuric and nitric acid which react with
ammonia to form sulfates and nitrates, both of which are important
components of ambient PM. The health effects of ambient PM are
discussed in Section 0 of this preamble. NOX and NMHC are
the two major precursors of

ozone. The health effects of ozone are covered in Section 0.
(b) Health Effects of NO2
    Information on the health effects of NO2 can be found in
the EPA Integrated Science Assessment (ISA) for Nitrogen Oxides.\364\
The EPA has concluded that the findings of epidemiologic, controlled
human exposure, and animal toxicological studies provide evidence that
is sufficient to infer a likely causal relationship between respiratory
effects and short-term NO2 exposure. The ISA concludes that
the strongest evidence for such a relationship comes from epidemiologic
studies of respiratory effects including symptoms, emergency department
visits, and hospital admissions. The ISA also draws two broad
conclusions regarding airway responsiveness following NO2
exposure. First, the ISA concludes that NO2 exposure may
enhance the sensitivity to allergen-induced decrements in lung function
and increase the allergen-induced airway inflammatory response
following 30-minute exposures of asthmatics to NO2
concentrations as low as 0.26 ppm. In addition, small but significant
increases in non-specific airway hyperresponsiveness were reported
following 1-hour exposures of asthmatics to 0.1 ppm NO2.
Second, exposure to NO2 has been found to enhance the
inherent responsiveness of the airway to subsequent nonspecific
challenges in controlled human exposure studies of asthmatic subjects.
Enhanced airway responsiveness could have important clinical
implications for asthmatics since transient increases in airway
responsiveness following NO2 exposure have the potential to
increase symptoms and worsen asthma control. Together, the
epidemiologic and experimental data sets form a plausible, consistent,
and coherent description of a relationship between NO2
exposures and an array of adverse health effects that range from the
onset of respiratory symptoms to hospital admission.
---------------------------------------------------------------------------

    \364\ U.S. EPA (2008). Integrated Science Assessment for Oxides
of Nitrogen--Health Criteria (Final Report). EPA/600/R-08/071.
Washington, DC: U.S.EPA. Docket EPA-HQ-OAR-2010-0162.
---------------------------------------------------------------------------

    Although the weight of evidence supporting a causal relationship is
somewhat less certain than that associated with respiratory morbidity,
NO2 has also been linked to other health endpoints. These
include all-cause (nonaccidental) mortality, hospital admissions or
emergency department visits for cardiovascular disease, and decrements
in lung function growth associated with chronic exposure.
(c) Health Effects of SO2
    Information on the health effects of SO2 can be found in
the EPA Integrated Science Assessment for Sulfur Oxides.\365\
SO2 has long been known to cause adverse respiratory health
effects, particularly among individuals with asthma. Other potentially
sensitive groups include children and the elderly. During periods of
elevated ventilation, asthmatics may experience symptomatic
bronchoconstriction within minutes of exposure. Following an extensive
evaluation of health evidence from epidemiologic and laboratory
studies, the EPA has concluded that there is a causal relationship
between respiratory health effects and short-term exposure to
SO2. Separately, based on an evaluation of the epidemiologic
evidence of associations between short-term exposure to SO2
and mortality, the EPA has concluded that the overall evidence is
suggestive of a causal relationship between short-term exposure to
SO2 and mortality.
---------------------------------------------------------------------------

    \365\ U.S. EPA. (2008). Integrated Science Assessment (ISA) for
Sulfur Oxides--Health Criteria (Final Report). EPA/600/R-08/047F.
Washington, DC: U.S. Environmental Protection Agency. Docket EPA-HQ-
OAR-2010-0162.
---------------------------------------------------------------------------

(4) Carbon Monoxide
    Information on the health effects of CO can be found in the EPA
Integrated Science Assessment (ISA) for Carbon Monoxide.\366\ The ISA
concludes that ambient concentrations of CO are associated with a
number of adverse health effects.\367\ This section provides a summary
of the health effects associated with exposure to ambient
concentrations of CO.\368\
---------------------------------------------------------------------------

    \366\ U.S. EPA, 2010. Integrated Science Assessment for Carbon
Monoxide (Final Report). U.S. Environmental Protection Agency,
Washington, DC, EPA/600/R-09/019F, 2010. Available at http://cfpub.epa.gov/ncea/cfm/recordisplay.cfm?deid=218686. Docket EPA-HQ-
OAR-2010-0162
    \367\ The ISA evaluates the health evidence associated with
different health effects, assigning one of five ``weight of
evidence'' determinations: causal relationship, likely to be a
causal relationship, suggestive of a causal relationship, inadequate
to infer a causal relationship, and not likely to be a causal
relationship. For definitions of these levels of evidence, please
refer to Section 1.6 of the ISA.
    \368\ Personal exposure includes contributions from many
sources, and in many different environments. Total personal exposure
to CO includes both ambient and nonambient components; and both
components may contribute to adverse health effects.
---------------------------------------------------------------------------

    Human clinical studies of subjects with coronary artery disease
show a decrease in the time to onset of exercise-induced angina (chest
pain) and electrocardiogram changes following CO exposure. In addition,
epidemiologic studies show associations between short-term CO exposure
and cardiovascular morbidity, particularly increased emergency room
visits and hospital admissions for coronary heart disease (including
ischemic heart disease, myocardial infarction, and angina). Some
epidemiologic evidence is also available for increased hospital
admissions and emergency room visits for congestive heart failure and
cardiovascular disease as a whole. The ISA concludes that a causal
relationship is likely to exist between short-term exposures to CO and
cardiovascular morbidity. It also concludes that available data are
inadequate to conclude that a causal relationship exists between long-
term exposures to CO and cardiovascular morbidity.
    Animal studies show various neurological effects with in-utero CO
exposure. Controlled human exposure studies report inconsistent neural
and behavioral effects following low-level CO exposures. The ISA
concludes the evidence is suggestive of a causal relationship with both
short- and long-term exposure to CO and central nervous system effects.
    A number of epidemiologic and animal toxicological studies cited in
the ISA have evaluated associations between CO exposure and birth
outcomes such as preterm birth or cardiac birth defects. The
epidemiologic studies provide limited evidence of a CO-induced effect
on preterm births and birth defects, with weak evidence for a decrease
in birth weight. Animal toxicological studies have found associations
between perinatal CO exposure and decrements in birth weight, as well
as other developmental outcomes. The ISA concludes these studies are
suggestive of a causal relationship between long-term exposures to CO
and developmental effects and birth outcomes.
    Epidemiologic studies provide evidence of effects on respiratory
morbidity such as changes in pulmonary function, respiratory symptoms,
and hospital admissions associated with ambient CO concentrations. A
limited number of epidemiologic studies considered copollutants such as
ozone, SO2, and PM in two-pollutant models and found that CO
risk estimates were generally robust, although this limited evidence
makes it difficult to disentangle effects attributed to CO itself from
those of the larger complex air pollution mixture. Controlled human
exposure studies have not extensively evaluated the effect of CO on
respiratory morbidity. Animal studies at levels of 50-100 ppm CO show
preliminary evidence of altered pulmonary vascular remodeling and

oxidative injury. The ISA concludes that the evidence is suggestive of
a causal relationship between short-term CO exposure and respiratory
morbidity, and inadequate to conclude that a causal relationship exists
between long-term exposure and respiratory morbidity.
    Finally, the ISA concludes that the epidemiologic evidence is
suggestive of a causal relationship between short-term exposures to CO
and mortality. Epidemiologic studies provide evidence of an association
between short-term exposure to CO and mortality, but limited evidence
is available to evaluate cause-specific mortality outcomes associated
with CO exposure. In addition, the attenuation of CO risk estimates
which was often observed in copollutant models contributes to the
uncertainty as to whether CO is acting alone or as an indicator for
other combustion-related pollutants. The ISA also concludes that there
is not likely to be a causal relationship between relevant long-term
exposures to CO and mortality.
(5) Air Toxics
    Heavy-duty vehicle emissions contribute to ambient levels of air
toxics known or suspected as human or animal carcinogens, or that have
noncancer health effects. The population experiences an elevated risk
of cancer and other noncancer health effects from exposure to the class
of pollutants known collectively as ``air toxics.'' \369\ These
compounds include, but are not limited to, benzene, 1,3-butadiene,
formaldehyde, acetaldehyde, acrolein, diesel particulate matter and
exhaust organic gases, polycyclic organic matter, and naphthalene.
These compounds were identified as national or regional risk drivers or
contributors in the 2005 National-scale Air Toxics Assessment and have
significant inventory contributions from mobile sources.\370\
---------------------------------------------------------------------------

    \369\ U.S. EPA. 2002 National-Scale Air Toxics Assessment.
http://www.epa.gov/ttn/atw/nata12002/risksum.html Docket EPA-HQ-OAR-
2010-0162.
    \370\ U.S. EPA 2009. National-Scale Air Toxics Assessment for
2002. http://www.epa.gov/ttn/atw/nata2002/ Docket EPA-HQ-OAR-2010-
0162.
---------------------------------------------------------------------------

(a) Diesel Exhaust
    Heavy-duty diesel engines emit diesel exhaust, a complex mixture
composed of carbon dioxide, oxygen, nitrogen, water vapor, carbon
monoxide, nitrogen compounds, sulfur compounds and numerous low-
molecular-weight hydrocarbons. A number of these gaseous hydrocarbon
components are individually known to be toxic, including aldehydes,
benzene and 1,3-butadiene. The diesel particulate matter present in
diesel exhaust consists mostly of fine particles (< 2.5 [micro]m),
including a significant fraction of ultrafine particles (< 0.1
[micro]m). These particles have a large surface area which makes them
an excellent medium for adsorbing organics and their small size makes
them highly respirable. Many of the organic compounds present in the
gases and on the particles, such as polycyclic organic matter, are
individually known to have mutagenic and carcinogenic properties.
    Diesel exhaust varies significantly in chemical composition and
particle sizes between different engine types (heavy-duty, light-duty),
engine operating conditions (idle, accelerate, decelerate), and fuel
formulations (high/low sulfur fuel). Also, there are emissions
differences between on-road and nonroad engines because the nonroad
engines are generally of older technology. After being emitted in the
engine exhaust, diesel exhaust undergoes dilution as well as chemical
and physical changes in the atmosphere. The lifetime for some of the
compounds present in diesel exhaust ranges from hours to days.\371\
---------------------------------------------------------------------------

    \371\ U.S. EPA (2002). Health Assessment Document for Diesel
Engine Exhaust. EPA/600/8-90/057F Office of Research and
Development, Washington DC. Retrieved on March 17, 2009, from http://cfpub.epa.gov/ncea/cfm/recordisplay.cfm?deid=29060. Docket EPA-HQ-
OAR-2010-0162.
---------------------------------------------------------------------------

(i) Diesel Exhaust: Potential Cancer Effects
    In EPA's 2002 Diesel Health Assessment Document (Diesel HAD),\372\
exposure to diesel exhaust was classified as likely to be carcinogenic
to humans by inhalation from environmental exposures, in accordance
with the revised draft 1996/1999 EPA cancer guidelines. A number of
other agencies (National Institute for Occupational Safety and Health,
the International Agency for Research on Cancer, the World Health
Organization, California EPA, and the U.S. Department of Health and
Human Services) have made similar classifications. However, EPA also
concluded in the Diesel HAD that it is not possible currently to
calculate a cancer unit risk for diesel exhaust due to a variety of
factors that limit the current studies, such as limited quantitative
exposure histories in occupational groups investigated for lung cancer.
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    \372\ See U.S. EPA (2002) Diesel HAD, Note 371, at pp. 1-1, 1-2.
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    For the Diesel HAD, EPA reviewed 22 epidemiologic studies on the
subject of the carcinogenicity of workers exposed to diesel exhaust in
various occupations, finding increased lung cancer risk, although not
always statistically significant, in 8 out of 10 cohort studies and 10
out of 12 case-control studies within several industries. Relative risk
for lung cancer associated with exposure ranged from 1.2 to 1.5,
although a few studies show relative risks as high as 2.6.
Additionally, the Diesel HAD also relied on two independent meta-
analyses, which examined 23 and 30 occupational studies respectively,
which found statistically significant increases in smoking-adjusted
relative lung cancer risk associated with exposure to diesel exhaust of
1.33 to 1.47. These meta-analyses demonstrate the effect of pooling
many studies and in this case show the positive relationship between
diesel exhaust exposure and lung cancer across a variety of diesel
exhaust-exposed occupations.373 374
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    \373\ Bhatia, R., Lopipero, P., Smith, A. (1998). Diesel
exposure and lung cancer. Epidemiology, 9(1), 84-91. Docket EPA-HQ-
OAR-2010-0162.
    \374\ Lipsett, M. Campleman, S. (1999). Occupational exposure to
diesel exhaust and lung cancer: a meta-analysis. Am J Public Health,
80(7), 1009-1017. Docket EPA-HQ-OAR-2010-0162.
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    In the absence of a cancer unit risk, the Diesel HAD sought to
provide additional insight into the significance of the diesel exhaust-
cancer hazard by estimating possible ranges of risk that might be
present in the population. An exploratory analysis was used to
characterize a possible risk range by comparing a typical environmental
exposure level for highway diesel sources to a selected range of
occupational exposure levels. The occupationally observed risks were
then proportionally scaled according to the exposure ratios to obtain
an estimate of the possible environmental risk. A number of
calculations are needed to accomplish this, and these can be seen in
the EPA Diesel HAD. The outcome was that environmental risks from
diesel exhaust exposure could range from a low of 10-4 to
10-5 to as high as 10\3\, reflecting the range of
occupational exposures that could be associated with the relative and
absolute risk levels observed in the occupational studies. Because of
uncertainties, the analysis acknowledged that the risks could be lower
than 10-4 or 10-5, and a zero risk from diesel
exhaust exposure was not ruled out.
(ii) Diesel Exhaust: Other Health Effects
    Noncancer health effects of acute and chronic exposure to diesel
exhaust emissions are also of concern to the EPA. EPA derived a diesel
exhaust reference concentration (RfC) from

consideration of four well-conducted chronic rat inhalation studies
showing adverse pulmonary effects.375 376 377 378 The RfC is
5 [micro]g/m\3\ for diesel exhaust as measured by diesel particulate
matter. This RfC does not consider allergenic effects such as those
associated with asthma or immunologic effects. There is growing
evidence, discussed in the Diesel HAD, that exposure to diesel exhaust
can exacerbate these effects, but the exposure-response data are
presently lacking to derive an RfC. The EPA Diesel HAD states, ``With
[diesel particulate matter] being a ubiquitous component of ambient PM,
there is an uncertainty about the adequacy of the existing [diesel
exhaust] noncancer database to identify all of the pertinent [diesel
exhaust]-caused noncancer health hazards.'' (p. 9-19). The Diesel HAD
concludes ``that acute exposure to [diesel exhaust] has been associated
with irritation of the eye, nose, and throat, respiratory symptoms
(cough and phlegm), and neurophysiological symptoms such as headache,
lightheadedness, nausea, vomiting, and numbness or tingling of the
extremities.'' \379\
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    \375\ Ishinishi, N. Kuwabara, N. Takaki, Y., et al. (1988).
Long-term inhalation experiments on diesel exhaust. In: Diesel
exhaust and health risks. Results of the HERP studies. Ibaraki,
Japan: Research Committee for HERP Studies; pp.11-84. Docket EPA-HQ-
OAR-2010-0162.
    \376\ Heinrich, U., Fuhst, R., Rittinghausen, S., et al. (1995).
Chronic inhalation exposure of Wistar rats and two different strains
of mice to diesel engine exhaust, carbon black, and titanium
dioxide. Inhal Toxicol, 7, 553-556. Docket EPA-HQ-OAR-2010-0162.
    \377\ Mauderly, J.L., Jones, R.K., Griffith, W.C., et al.
(1987). Diesel exhaust is a pulmonary carcinogen in rats exposed
chronically by inhalation. Fundam. Appl. Toxicol., 9, 208-221.
Docket EPA-HQ-OAR-2010-0162.
    \378\ Nikula, K.J., Snipes, M.B., Barr, E.B., et al. (1995).
Comparative pulmonary toxicities and carcinogenicities of
chronically inhaled diesel exhaust and carbon black in F344 rats.
Fundam. Appl. Toxicol, 25, 80-94. Docket EPA-HQ-OAR-2010-0162.
    \379\ See U.S. EPA (2002), Diesel HAD at Note 371, at p. 9-9.
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(iii) Ambient PM2.5 Levels and Exposure to Diesel Exhaust PM
    The Diesel HAD also briefly summarizes health effects associated
with ambient PM and discusses the EPA's annual PM2.5 NAAQS
of 15 [micro]g/m\3\. There is a much more extensive body of human data
showing a wide spectrum of adverse health effects associated with
exposure to ambient PM, of which diesel exhaust is an important
component. The PM2.5 NAAQS is designed to provide protection
from the noncancer and premature mortality effects of PM2.5
as a whole.
(iv) Diesel Exhaust PM Exposures
    Exposure of people to diesel exhaust depends on their various
activities, the time spent in those activities, the locations where
these activities occur, and the levels of diesel exhaust pollutants in
those locations. The major difference between ambient levels of diesel
particulate and exposure levels for diesel particulate is that exposure
accounts for a person moving from location to location, proximity to
the emission source, and whether the exposure occurs in an enclosed
environment.
Occupational Exposures
    Occupational exposures to diesel exhaust from mobile sources can be
several orders of magnitude greater than typical exposures in the non-
occupationally exposed population.
    Over the years, diesel particulate exposures have been measured for
a number of occupational groups. A wide range of exposures has been
reported, from 2 [mu]g/m\3\ to 1,280 [mu]g/m\3\, for a variety of
occupations. As discussed in the Diesel HAD, the National Institute of
Occupational Safety and Health has estimated a total of 1,400,000
workers are occupationally exposed to diesel exhaust from on-road and
nonroad vehicles.
Elevated Concentrations and Ambient Exposures in Mobile Source-Impacted
Areas
    Regions immediately downwind of highways or truck stops may
experience elevated ambient concentrations of directly-emitted
PM2.5 from diesel engines. Due to the unique nature of
highways and truck stops, emissions from a large number of diesel
engines are concentrated in a small area. Studies near roadways with
high truck traffic indicate higher concentrations of components of
diesel PM than other locations.380, 381, 382 High ambient
particle concentrations have also been reported near trucking
terminals, truck stops, and bus garages.383, 384, 385
Additional discussion of exposure and health effects associated with
traffic is included below in Section 0.
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    \380\ Zhu, Y.; Hinds, W.C.; Kim, S.; Shen, S.; Sioutas, C.
(2002) Study of ultrafine particles near a major highway with heavy-
duty diesel traffic. Atmospheric Environment 36: 4323-4335. Docket
EPA-HQ-OAR-2010-0162.
    \381\ Lena, T.S; Ochieng, V.; Holgu[iacute]n-Veras, J.; Kinney,
P.L. (2002) Elemental carbon and PM2.5 levels in an urban
community heavily impacted by truck traffic. Environ Health Perspect
110: 1009-1015. Docket EPA-HQ-OAR-2010-0162.
    \382\ Soliman, A.S.M.; Jacko, J.B.; Palmer, G.M. (2006)
Development of an empirical model to estimate real-world fine
particulate matter emission factors: the Traffic Air Quality model.
J Air & Waste Manage Assoc 56: 1540-1549. Docket EPA-HQ-OAR-2010-
0162.
    \383\ Davis, M.E.; Smith, T.J.; Laden, F.; Hart, J.E.; Ryan,
L.M.; Garshick, E. (2006) Modeling particle exposure in U.S.
trucking terminals. Environ Sci Techol 40: 4226-4232. Docket EPA-HQ-
OAR-2010-0162.
    \384\ Miller, T.L.; Fu, J.S.; Hromis, B.; Storey, J.M. (2007)
Diesel truck idling emissions--measurements at a PM2.5
hot spot. Proceedings of the Annual Conference of the Transportation
Research Board, paper no. 07-2609. Docket EPA-HQ-OAR-2010-0162.
    \385\ Ramachandran, G.; Paulsen, D.; Watts, W.; Kittelson, D.
(2005) Mass, surface area, and number metrics in diesel occupational
exposure assessment. J Environ Monit 7: 728-735. Docket EPA-HQ-OAR-
2010-0162.
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(b) Benzene
    The EPA's Integrated Risk Information System (IRIS) database lists
benzene as a known human carcinogen (causing leukemia) by all routes of
exposure, and concludes that exposure is associated with additional
health effects, including genetic changes in both humans and animals
and increased proliferation of bone marrow cells in
mice.386, 387, 388 EPA states in its IRIS database that data
indicate a causal relationship between benzene exposure and acute
lymphocytic leukemia and suggest a relationship between benzene
exposure and chronic non-lymphocytic leukemia and chronic lymphocytic
leukemia. The International Agency for Research on Carcinogens (IARC)
has determined that benzene is a human carcinogen and the U.S.
Department of Health and Human Services (DHHS) has characterized
benzene as a known human carcinogen.389, 390
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    \386\ U.S. EPA. 2000. Integrated Risk Information System File
for Benzene. This material is available electronically at http://www.epa.gov/iris/subst/0276.htm. Docket EPA-HQ-OAR-2010-0162.
    \387\ International Agency for Research on Cancer. 1982.
Monographs on the evaluation of carcinogenic risk of chemicals to
humans, Volume 29. Some industrial chemicals and dyestuffs, World
Health Organization, Lyon, France, p. 345-389. Docket EPA-HQ-OAR-
2010-0162.
    \388\ Irons, R.D.; Stillman, W.S.; Colagiovanni, D.B.; Henry,
V.A. 1992. Synergistic action of the benzene metabolite hydroquinone
on myelopoietic stimulating activity of granulocyte/macrophage
colony-stimulating factor in vitro, Proc. Natl. Acad. Sci. 89:3691-
3695. Docket EPA-HQ-OAR-2010-0162.
    \389\ See IARC, Note 387, above.
    \390\ U.S. Department of Health and Human Services National
Toxicology Program 11th Report on Carcinogens available at: http://ntp.niehs.nih.gov/go/16183. Docket EPA-HQ-OAR-2010-0162.
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    A number of adverse noncancer health effects including blood
disorders, such as preleukemia and aplastic anemia, have also been
associated with long-term exposure to benzene.391, 392

The most sensitive noncancer effect observed in humans, based on
current data, is the depression of the absolute lymphocyte count in
blood.393, 394 In addition, recent work, including studies
sponsored by the Health Effects Institute (HEI), provides evidence that
biochemical responses are occurring at lower levels of benzene exposure
than previously known.395, 396, 397, 398 EPA's IRIS program
has not yet evaluated these new data.
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    \391\ Aksoy, M. (1989). Hematotoxicity and carcinogenicity of
benzene. Environ. Health Perspect. 82: 193-197. Docket EPA-HQ-OAR-
2010-0162.
    \392\ Goldstein, B.D. (1988). Benzene toxicity. Occupational
medicine. State of the Art Reviews. 3: 541-554. Docket EPA-HQ-OAR-
2010-0162.
    \393\ Rothman, N., G.L. Li, M. Dosemeci, W.E. Bechtold, G.E.
Marti, Y.Z. Wang, M. Linet, L.Q. Xi, W. Lu, M.T. Smith, N. Titenko-
Holland, L.P. Zhang, W. Blot, S.N. Yin, and R.B. Hayes (1996)
Hematotoxicity among Chinese workers heavily exposed to benzene. Am.
J. Ind. Med. 29: 236-246. Docket EPA-HQ-OAR-2010-0162.
    \394\ U.S. EPA (2002) Toxicological Review of Benzene (Noncancer
Effects). Environmental Protection Agency, Integrated Risk
Information System, Research and Development, National Center for
Environmental Assessment, Washington DC. This material is available
electronically at http://www.epa.gov/iris/subst/0276.htm. Docket
EPA-HQ-OAR-2010-0162.
    \395\ Qu, O.; Shore, R.; Li, G.; Jin, X.; Chen, C.L.; Cohen, B.;
Melikian, A.; Eastmond, D.; Rappaport, S.; Li, H.; Rupa, D.;
Suramaya, R.; Songnian, W.; Huifant, Y.; Meng, M.; Winnik, M.; Kwok,
E.; Li, Y.; Mu, R.; Xu, B.; Zhang, X.; Li, K. (2003) HEI Report 115,
Validation & Evaluation of Biomarkers in Workers Exposed to Benzene
in China. Docket EPA-HQ-OAR-2010-0162.
    \396\ Qu, Q., R. Shore, G. Li, X. Jin, L.C. Chen, B. Cohen, et
al. (2002) Hematological changes among Chinese workers with a broad
range of benzene exposures. Am. J. Industr. Med. 42: 275-285. Docket
EPA-HQ-OAR-2010-0162.
    \397\ Lan, Qing, Zhang, L., Li, G., Vermeulen, R., et al. (2004)
Hematotoxically in Workers Exposed to Low Levels of Benzene. Science
306: 1774-1776. Docket EPA-HQ-OAR-2010-0162.