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In this unit, we became familiar with regulatory issues related to air pollution.

For this assignment, you will write an essay that meets the following criteria:

examines the National Ambient Air Quality Standards (NAAQS) impact on health and industry,

assesses the steps required for licensing under New Source Review (NSR),

analyzes the role of ground-level ozone and ozone in the stratosphere,

explores climate change and why global warming is a difficult problem to solve, and

describes how knowledge of the concepts above contribute to your career goals.

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Returning to Clean Air Act Fundamentals: A Renewed Call to Regulate
Greenhouse Gases Under the National Ambient Air Quality Standards
(NAAQS) Program
Authors: Howard M. Crystal, Kassie Siegel, Maya Golden-Krasner and Clare Lakewood
Date: Winter 2019
From: Georgetown Environmental Law Review(Vol. 31, Issue 2)
Publisher: Georgetown University Law Center
Document Type: Article
Length: 24,650 words
I. The Climate Crisis and the EPA’s Responses to Date
A. The Climate Crisis
B. The EPA’s Efforts to Address the Climate Crisis to
Date: Some Steps Forward, and Now Backward
1. The Obama EPA’s Greenhouse Gas Regulations
a. The Clean Power Plan
b. Challenges to the Clean Power Plan
c. The EPA’s Limited Progress Regulating Greenhouse
Gas Emissions from Other Stationary Source Sectors
d. The EPA’s Progress Regulating Greenhouse Gases
from Mobile Sources
2. De-regulating Greenhouse Gases under the Trump
Administration: (Roll)Back to the Future
a. Affordable Clean Energy Rule and Oil and Gas
Regulation Roll-backs
b. Roll-backs of Mobile Source Regulations
c. The EPA’s Broader Roll-back of Science-Based
II. The Updated Case for a Greenhouse Gas NAAQS
A. The NAAQS Program
B. Greenhouse Gases Are Well-Suited for Regulation Under
the NAAQS Program
1. The Time Period Necessary to Achieve Attainment
is No Impediment to a Greenhouse Gas NAAQS
a. What a Greenhouse Gas NAAQS Could Look Like
b. How a Greenhouse Gas NAAQS can be Formulated
i. The EPA Could Design a Greenhouse Gas NAAQS
that Meets the Deadline for a Primary Standard
ii. The EPA has Discretion to Establish a Secondary
NAAQS for Greenhouse Gases that Will Not Be
Fully Attained for Decades
2. The Unique Nature of the SIPs That Will Address
Greenhouse Gas Emissions Also Poses No Obstacle to
a Greenhouse Gas NAAQS
a. Clean Air Act Section 179B Calls on the EPA,
in Considering SIPs, to Take Emissions from
Outside the United States into Account, and
the Paris Agreement Provides a Framework for
Approaching That Task
b. The Supreme Court’s Decision in Homer
Demonstrates that the EPA Can Meaningfully
Apportion Greenhouse Gas Reductions Within the
United States, and the Clean Power Plan Provides
an Initial Structure from Which the EPA Can Frame
a Greenhouse Gas NAAQS
III. The Clean Air Act’s Section 111(d) Exclusion, and Concerns
About Congressional Backlash, Should Not Stand in the Way
of a Greenhouse Gas NAAQS
A. The Relationship Between a NAAQS and Regulation Under
Section 111(d) is Not an Obstacle to a Greenhouse
B. Concerns that Congress Could Remove the EPA’s
Authority to Regulate Greenhouse Gases Under the
NAAQS Program Does Not Counsel Against the Agency
Finally Moving Forward
In the more than a decade since the Supreme Court resolved that greenhouse gases are “air pollutants” under the Clean Air
Act (“Act”), (1) the Environmental Protection Agency (“EPA”) has grappled with how to bring the Act to bear on the existential
threat these pollutants pose to the earth and all its inhabitants. Under President Obama, the EPA addressed greenhouse gases
by regulating several of the most important sources. (2) Those efforts, although salutary, were limited and subject to protracted
litigation. (3) At the same time, President Obama left office without invoking the Act’s most far-reaching and important tool: the
National Ambient Air Quality Standards (“NAAQS”) program, or even responding to a 2009 rulemaking petition urging such
regulations. (4)
The NAAQS program is the heart of the Clean Air Act, providing an overarching, comprehensive program for the reduction of
those air pollutants, emitted from numerous and diverse sources, that endanger public health or welfare. Critically, the NAAQS
program allows states to use their broad regulatory powers over sectors not subject to federal legislation to optimally attain the
NAAQS through State Implementation Plans (“SIPs”). (5) While there have certainly been challenges in implementing the
NAAQS program over the years, it has made significant strides in reducing levels of the existing listed criteria air pollutants-lead, ozone, carbon monoxide, sulfur oxides, nitrogen oxides, and particulate matter.
The Trump Administration does not plan to promulgate a greenhouse gas NAAQS. (6) To the contrary, the current EPA is
curtailing and rolling back not only the Obama Administration’s greenhouse gas regulations, but the larger Clean Air Act
framework that has been a bedrock of the Agency’s approach to protecting public health and the environment for generations.
However, the premise of this Article is that, under a new administration, the EPA will resume its congressional mandate to
make science-driven decisions to protect human health and the environment. At that time, the EPA should inaugurate its return
to that mission by finally promulgating NAAQS for greenhouse gases. Indeed, promulgating such a NAAQS would be the
perfect vehicle for the EPA to reclaim its mantle as a leader in science-based decision-making for the protection of the
After the Supreme Court resolved that greenhouse gases are subject to the Clean Air Act in 2007, (8) the question of a
greenhouse gas NAAQS received lengthy treatment by both academics and practitioners. (9) In one article, practitioners
argued that setting a NAAQS for greenhouse gases would fit naturally within the language and purpose of this program and
explained why regulating in this manner would be the most expeditious and effective means to employ the full force of the Act
to address the climate change crisis. (10) The article also responded to several arguments that questioned the viability of a
greenhouse gas NAAQS, including how such a standard would be structured given that greenhouse gas emissions are not
localized like other criteria air pollutants and the legal risks implementation of such a NAAQS may pose to the EPA’s regulatory
authority under other Clean Air Act sections–particularly Section 111, under which the Obama Administration promulgated the
Clean Power Plan. (11)
This Article reiterates and expands on these arguments in favor of a greenhouse gas NAAQS, calling for the EPA to launch a
more comprehensive approach to regulating greenhouse gases under the Clean Air Act than the Agency has followed to date.
Moreover, the Article will detail how eight developments in the past several years lend additional support to the case for a
greenhouse gas NAAQS.
First, the climate crisis has only grown more urgent, and thus the need for the far-reaching protections of a greenhouse gas
NAAQS more vital. While the global atmospheric concentration of carbon dioxide remained below approximately 300 parts per
million (ppm) for more than 800,000 years, and reached 350 ppm less than thirty years ago, it has continued to rise from 395
ppm in December 2012 to 408 ppm in December 2017. (12) Climate change and its devastating impacts are no longer a future
concern; the effects are being experienced now and are only going to get much worse without dramatic action to curb
greenhouse gas emissions.
Second, in 2015 the EPA issued its Clean Power Plan (“CPP”), which regulates greenhouse gas emissions from electric power
plants. (13) Although the Supreme Court has stayed its implementation, (14) and the Trump Administration has proposed
repealing it, (15) the CPP as promulgated would regulate these emissions with a nation-wide program containing elements that
could be incorporated into a greenhouse gas NAAQS. For example, the EPA established an emission reduction target
approach for each state, which could be expanded to form the basis for NAAQS SIPs and encompass greenhouse gas
reduction measures across sectors. (16)
Third, the ongoing and protracted litigation over the CPP and other greenhouse gas initiatives demonstrates that the sector-bysector approach the EPA has relied on to date will not address the climate crisis more quickly than a greenhouse gas NAAQS.
In particular, although promulgating a greenhouse gas NAAQS will almost certainly engender litigation, success with such a
program would bring about much more far-reaching results than the current regulatory approach. That is because only the
NAAQS program forces the EPA to achieve the critical goal of protecting human health and welfare, as distinguished from
focusing solely on improving technologies within each separate sector.
Fourth, in 2014 the Supreme Court, in Homer, upheld a NAAQS implementation rule which–like a potential greenhouse gas
NAAQS–addressed pollution that crosses state lines. The Court recognized the EPA’s broad latitude to address the “thorny
causation problem” caused when multiple states contribute to the failure to attain NAAQS, and concluded that the EPA’s
“efficient and equitable solution to the allocation problem” was well within the Agency’s discretion. (17) This decision further
supports the EPA’s authority to appropriately allocate greenhouse gas emission reductions among states under a greenhouse
gas NAAQS.
Fifth, although the Supreme Court issued another ruling in UARG limiting the EPA’s authority to regulate greenhouse gas
emissions from certain sources, (18) in that decision the Court further concluded that the EPA could continue to regulate those
sources under certain conditions, which has important implications for the EPA’s authority to regulate these pollutants under
the NAAQS program. Thus, although the Court found that the term “air pollutant” in the statutory definition of “major sources”
does not include greenhouse gases–because, the Court concluded, including them would lead to absurd results Congress
could not have intended–the Court limited its holding to that definition alone. The Court concluded there is no similar constraint
on including greenhouse gas emissions where the EPA is regulating those sources anyway, called “anyway sources,” for other
pollutant emissions. (19)
One of the arguments against a greenhouse gas NAAQS concerns the statutory requirement that the EPA establish a deadline
for the “attainment” of a primary NAAQS in no longer than ten years. (20) A ten-year deadline is currently impossible for
greenhouse gases because they are long-lived in the atmosphere, and thus will take much longer than ten years to reduce to
safe concentration levels. But the NAAQS program also has a separate provision for imposing secondary standards as
necessary to protect “public welfare.” (21) This provision not only contains no strict deadline, it expressly calls on the EPA to
take into account effects on “climate.” (22) The Court’s treatment of “anyway sources” in UARG thus suggests a path by which
the EPA could impose a secondary NAAQS, even if it were determined that the Agency does not have the authority to impose
a primary standard.
Sixth, in 2015 the United States and the international community, under the auspices of the United Nations Framework
Convention on Climate Change, entered into the Paris Agreement, which commits participating nations to taking the steps
necessary to hold “the global average temperature to well below 2[degrees] Celsius above pre-industrial levels and pursue
efforts to limit the temperature increase to 1.5[degrees] Celsius above pre-industrial levels.” (23) This international framework
serves to reinforce the EPA’s authority, under Clean Air Act Section 179B, (24) to take global greenhouse gas emissions into
account in setting domestic emission limits under the NAAQS program. (25)
Seventh, in recent years, scientists have developed reasonable carbon budgets that allocate appropriate carbon emission
reductions among the nations of the world, including the United States. For example, the United States carbon budget to limit
temperature rise to well below 2[degrees]C (per the Paris Agreement) has been estimated at 25 GtC[O.sub.2]eq to 57
GtC[O.sub.2]eq on average. (26) Taken together, this carbon budgets work and the Paris Agreement provide the EPA with
multiple options for establishing the United States’ emission reduction levels that would be incorporated into a greenhouse gas
Finally, the current regulatory uncertainty concerning the regulation of greenhouse gases under the NAAQS program, which
will remain so long as the EPA does not invoke this authority, is arguably itself an obstacle to addressing the climate crisis in
other ways. For example, in response to recent tort lawsuits against fossil fuel companies and others potentially liable for the
sea level rise and other damages caused by climate change, defendants have been arguing, with some initial success, that
because the EPA has such plenary authority to address greenhouse gases under the Clean Air Act, the Act displaces any
claims that touch on climate change. (27)
If, in fact, the courts were to determine that the EPA has no power to regulate greenhouse gases under the NAAQS program,
defendants’ displacement arguments would certainly have less force. On the other hand, the current status quo, under which
the scope of the EPA’s authority to act remains unresolved, has allowed defendants to more successfully invoke the Act to
avoid liability.
Accordingly, even if in response to an EPA NAAQS for greenhouse gases, the courts–or Congress–were to preclude the EPA
from regulating these pollutants under the NAAQS program, that result could arguably be preferable to the status quo. In short,
while today there is no such program, the uncertain prospect of comprehensively regulating greenhouse gases by means of a
NAAQS poses an obstacle to addressing the climate crisis in other ways. Under a new administration, the EPA should not let
this untenable status quo remain.
Part I of this Article summarizes the state of the climate crisis and addresses the Obama Administration’s efforts to harness the
Act to address that crisis, before summarizing the Trump Administration’s initiatives to dismantle these efforts.
Part II, in turn, details the unique suitability of the NAAQS program to comprehensively address greenhouse gas pollution in the
United States. In particular, this Part will explain why, especially in light of the Paris Agreement and more recent work on
carbon budgets, the dispersal of greenhouse gases throughout the atmosphere is no impediment to a greenhouse gas
NAAQS. It will also suggest several approaches that the EPA could take to ensure that a greenhouse gas NAAQS is consistent
with the statute’s requirements for prompt action towards attainment of air quality standards, particularly in light of the Supreme
Court’s rulings in Homer and UARG, as well as the significant progress the EPA made with the SIPs components of the CPP.
Finally, Part III will explain why neither (a) the relationship between the NAAQS program and the EPA’s power to regulate
pollutants under Clean Air Act Section 111 (under which the CPP was promulgated) nor (b) any concern with Congressional
backlash, should stand in the way of the EPA finally moving forward with a greenhouse gas NAAQS. As for the CPP, it would
not be impacted until a greenhouse gas NAAQS is in effect, at which point its relevant elements can be incorporated into the
NAAQS. And although Congress always will have the power to completely remove the EPA’s authority to promulgate a
greenhouse gas NAAQS, the Agency’s refusal to resolve the scope of this authority is a double blow, hindering both the full use
of the Clean Air Act to address the climate crisis and separate efforts to address that crisis with other regulatory tools, both
within and beyond the Act. Accordingly, a new EPA should finally move forward with a greenhouse gas NAAQS.
After the Supreme Court ruled in Massachusetts v. EPA (28) that greenhouse gases are “air pollutants” under the Clean Air
Act, the EPA comprehensively assessed whether these gases endanger public health and welfare. In 2009, the EPA made its
endangerment finding, establishing that, for the purposes of the Act, motor-vehicle emissions of greenhouse gases “contribute
to the total greenhouse gas air pollution, and thus to the climate change problem, which is reasonably anticipated to endanger
public health and welfare.” (29) Industry-supported groups and various states vigorously challenged that finding. (30) Rejecting
those challenges in 2012, the D.C. Circuit unanimously found that the EPA had relied on the best scientific data; had
reasonably concluded, based on that data, that climate change is caused by anthropogenic greenhouse gas emissions; and
had also reasonably found that climate change “threatens both public health and public welfare.” (31) The Supreme Court
declined to review the EPA’s findings, and since that time, the EPA has consistently reiterated that greenhouse gases
endanger public health and welfare. (32)
Since that decision, the urgency of the climate crisis has only grown. In October 2018, the Intergovernmental Panel on Climate
Change (“IPCC”) issued a Special Report on the state of the crisis and what needs to be done. (33) Most importantly, the
Special Report concludes that it is absolutely critical for greenhouse gas emissions to be drastically reduced in the next decade
to avoid the worst impacts of climate change. (34) Key findings of the special report also include:
First, “human-induced warming reached approximately 1[degrees]C (likely between 0.8[degrees]C and 1.2[degrees]C) above
pre-industrial levels in 2017, increasing at 0.2[degrees]C (likely between 0.1[degrees]C and 0.3[degrees]C) per decade.” (35)
Second, “[m]ean sea level is increasing… with substantial impacts already being felt by coastal ecosystems and communities….
These changes are interacting with other factors such as strengthening storms, which together are driving greater storm surge,
infrastructure damage, erosion and habitat loss.” (36)
Third, “[t]he ocean has absorbed about 30% of the anthropogenic carbon dioxide, resulting in ocean acidification and changes
to carbonate chemistry that are unprecedented in 65 million years.” (37)
Fourth, greenhouse gas emissions are principally responsible for global warming and climate change. (38)
And finally, “[t]he rise in global C[O.sub.2] concentration since 2000 is about 20 ppm/decade, which is up to 10 times faster
than any sustained rise in C[O.sub.2] during the past 800,000 years.” (39)
In November 2018, Volume II of the congressionally-mandated Fourth National Climate Assessment was released, further
detailing the stark realities of climate change impacts on Americans, including increased hurricanes and extended wildfire
seasons. (40) The Assessment also details how lower-income and marginalized communities are expected to experience even
greater impacts to their health, safety and quality of life than others. (41) It further concludes that, without substantial and
sustained reductions in emissions, the impact to the United States economy will likely reach hundreds of billions of dollars by
the end of the century. (42)
Reports aside, the on-the-ground evidence of the climate crisis is now all around us. Ever more severe hurricanes, rain storms
and extreme weather, wildfires, intense heat waves, melting ice, and other impacts are dominating headlines and devastating
lives and the environment. (43) The climate crisis is no longer something to be concerned about in the distant future. (44) And,
as detailed in the IPCC’s most recent report, absent necessary action within the next decade, it will become exponentially more
difficult to keep global temperatures from rising more than 1.5[degrees] Celsius–above which the earth will experience
devastating climate change impacts. (45)
Although the NAAQS program allows the EPA to comprehensively regulate emissions of an air pollutant that is both dangerous
and widespread, the Act also provides the EPA with tools to combat those pollutants more narrowly, by targeting individual
pollutant sectors and sources. This section reviews those programs, and the progress the Obama Administration made in
regulating greenhouse gases under them, and then addresses the Trump Administration’s efforts to roll back these initiatives.
As depicted in the chart on the following page, taken together, the EPA estimated that the emissions reductions from the
Obama Administration’s programs–between 2020 and 2050–would amount to approximately 16 gigatons of C[O.sub.2]eq.
Thus, although any or all of these emission reduction efforts might be strengthened, as developed to date they would not
collectively bring about greenhouse gas reduction levels even remotely approaching those necessary for the United States to
stay within its carbon budget of at least 25-57 gigatons of C[O.sub.2]eq. (46)
1. The Obama EPA’s Greenhouse Gas Regulations
a. The Clean Power Plan
For stationary sources, Clean Air Act Section 111(b) provides for the EPA to establish a list of the different “categories” of
stationary sources that “cause[], or contribute[] significantly to, air pollution which may reasonably be anticipated to endanger
public health or welfare,” and then to issue “standards of performance” for pollution from those sources. (47) Those standards
must reflect the “best system of emission reductions” (“BSER”) that stationary sources can achieve while taking into account
both the costs involved and “any nonair quality health and environmental impact and energy requirements.” (48)
In addition to mandating such regulations for new sources, the Act provides for the development of standards of performance
for existing stationary sources of pollution. (49) Under the existing source program in Section 111(d), the Act provides for the
EPA to require that states develop plans–similar to the SIPs promulgated for national air quality standards–that impose
requirements on existing sources in sectors where new source standards are issued. It was under that authority that the EPA
issued the CPP.
The CPP was the Obama Administration’s marquee greenhouse gas reduction program, intended to establish the BSERs for
greenhouse gases from existing power plants. Pursuant to Clean Air Act Section 111(b), (50) in 2015 the EPA issued New
Source Performance Standards (“NSPS”) for greenhouse gas emissions from new, modified, and reconstructed fossil fuel-fired
steam generating units and natural gas-fired stationary combustion turbines–collectively Electric Generating Units, or “EGUs.”
(51) At the same time, pursuant to its authority under Section 111(d), (52) the EPA issued the CPP for greenhouse gas
emissions from existing power plants. (53) In its most general form, the CPP established state-by-state goals for carbon
emissions reductions from existing power plants and offered a flexible framework under which states could meet those targets.
More specifically, the EPA examined various approaches to the BSER from existing power plants. Based on that analysis the
EPA established state carbon emission reduction targets. The CPP then provided emission guidelines to guide states in
achieving these targets over time. (54) Under the CPP, the EPA defined the BSER for existing power plants by reference to
several “building blocks.” Block One concerned economically achievable measures source owners could take to improve the
heat rates–the efficiency with which plants convert fuel to electricity–at coal-fired steam plants. (55) Blocks Two and Three, in
turn, focused on economically achievable approaches to shifting energy generation from coal-fired, and other steam-to-electric,
power plants to other forms of generation, including more efficient existing natural gas combined-cycle plants (“gas plants”) and
renewable-energy sources such as wind and solar. (56)
The CPP provided for states to adopt plans to satisfy the emission guidelines and allowed multiple avenues for the states to
structure their plans and emission limits. For example, the CPP allowed for a relatively straightforward approach, whereby
states would implement the two national emission performance rates for coal and gas plants. Each source would be allowed to
reduce its emissions through a combination of actions, including heat-rate improvements, shifting generation from dirtier to
cleaner power generation methods, or acquiring emission rate credits. (57)
Alternatively, the CPP allowed states to adopt state-based emission limits that would blend the separate limits for coal and gas
plants, and which would apply uniformly to both kinds of plants. It also allowed for “mass-based” approaches used under other
programs–such as those addressing acid rain and cross-state smog–whereby the state would impose limits on the number of
tons of pollution a plant may emit, rather than calculating limits based on pollution emitted per unit of electricity generated. (58)
Finally, the CPP anticipated that source owners could choose to obtain alternative sources of generation to meet emission
reduction goals. Thus, states were permitted to adopt a mass-based plan that could include measures such as renewable
portfolio standards that provide for source owners to obtain renewable energy resources. Under any of these approaches,
states could also allow sources to engage in cross-state trading for emission reduction credits. (59)
b. Challenges to the Clean Power Plan
Litigation over the CPP has been fierce and unceasing. Opponents unsuccessfully tried to challenge the CPP before it was
even finalized, (60) and filed new challenges as soon as the final CPP was issued. (61) After the D.C. Circuit refused to
immediately stay the CPP, the petitioners obtained an unprecedented decision from the Supreme Court staying the CPP until
litigation over its legality is resolved. (62)
One of the many arguments against the CPP is that the EPA may not rely on its authority to regulate power plant emissions
under Section 111(d) in a manner that leads to widespread emission reductions through the development of renewable energy
sources. The CPP’s critical elements that may lead to “generation-shifting” to other sources of energy, opponents argue, go
beyond the EPA’s authority to regulate “sources” under Section 111(d). (63) In advancing this argument, opponents have
expressly contrasted the EPA’s broader authority under the NAAQS program, claiming that only under that kind of broader
authority could the EPA ensure reductions in greenhouse gas emissions across the economy. (64)
The D.C. Circuit considered the merits of CPP challenges initially en banc, but more than two years after hearing oral
arguments the court has not issued a decision on the CPP’s legality. In the meantime, the CPP and the litigation over it both
remain (65) while the Trump Administration pursues its replacement rule. (66)
c. The EPA’s Limited Progress Regulating Greenhouse Gas Emissions from Other Stationary Source Sectors
In addition to power plants, the EPA regulates pollutants from dozens of other categories of stationary industrial sources, (67)
many of which could potentially be regulated for greenhouse gas emissions. However, despite numerous lawsuits to prompt
action during the Obama Administration, the only progress made thus far has been on methane emissions, further supporting
the conclusion that a comprehensive approach to greenhouse gas regulation under the NAAQS program is preferable to
continuing to pursue emission limitations on a sector-by-sector basis. For example:
* Although the EPA has recognized that “[p]ortland cement is one of the largest stationary source categories of GHG
emissions,” (68) the Agency has declined to set a greenhouse gas NSPS. (69)
* The EPA has made no progress regulating greenhouse gas emissions from refineries. (70)
* The EPA has not issued greenhouse gas emission limits for industrial commercial-institutional boilers. (71)
* The EPA has similarly declined to regulate greenhouse gas emissions from coal mines, citing budgetary and resource
constraints. (72)
* Finally, as regards reductions in emissions of methane–a particularly potent greenhouse gas (73)–the EPA issued
regulations that would have begun to address methane emissions from landfills and the oil and gas sector, but it did not do so
comprehensively. The regulations also only addressed new, and not existing, sources. (74)
The EPA also regulates emissions from stationary sources under the Clean Air Act’s Prevention of Significant Deterioration
(“PSD”) and Title V permitting programs. (75) However, this authority also has not produced significant greenhouse gas
reductions because the Agency does not require permittees to consider alternatives such as renewable energy, and courts
have allowed the EPA to adopt approaches to Best Available Control Technology (“BACT”) requirements that limit
improvements to relatively minor efficiency adjustments rather than substantial changes. (76)
d. The EPA’s Progress Regulating Greenhouse Gases from Mobile Sources
Mobile sources–cars, trucks, airplanes, and other moving vehicles–also are an important source of air pollution. For those
sources, the Act requires that the EPA also establish standards governing emissions of air pollutants that “may reasonably be
anticipated to endanger public health or welfare.” (77) After such an endangerment finding for mobile sources, the EPA must
set standards “which reflect the greatest degree of emission reduction achievable through the application of [available
technology], giving appropriate consideration to cost, energy, and safety factors associated with the application of such
technology.” (78) The Act also authorizes differing standards among classes of vehicles–such as passenger cars versus
trucks, and aircraft, for which the EPA must also set standards for pollutants that “endanger public health or welfare.” (79)
The regulation of new motor vehicles under Section 202 was the focus of Massachusetts v. EPA, (80) and, in concert with
California’s efforts to also move forward with curbing these emissions, the Obama Administration’s EPA made more concrete
progress here than in any other sector. (81) In 2010, the EPA, along with the National Highway Traffic Safety Administration
(“NHTSA”) (82) and California, adopted the first parallel passenger car–otherwise called “light duty vehicle”–greenhouse gas
emission and fuel economy standards, for model years 2012-2016. (83) Two years later, the agencies adopted standards for
vehicles beginning in model year 2017, and running through 2025. (84)
The rulemaking also provided for the EPA to conduct a “mid-term review” of the standards for model years 2022-25. (85) In
January 2017, the EPA completed that mid-term review and issued its “Final Determination” that the original standards for
2022-25 should remain in place. (86) California reached the same result. (87)
Finally, although aircraft emissions account for 12 percent of all United States transportation greenhouse gas emissions and 3
percent of total United States GHG emissions, (88) the Obama Administration’s EPA never imposed any greenhouse gas
regulations for this sector. Thus, despite the EPA’s endangerment finding for aircraft greenhouse gas emissions in 2016, (89)
the Agency did not propose implementing emission standards.
2. De-regulating Greenhouse Gases under the Trump Administration: (Roll) Back to the Future
Fulfilling campaign promises to roll-back environmental regulations, (90) and consistent with his denial of climate change, (91)
in March 2018, President Trump signed Executive Order 13783, directing the EPA to re-evaluate the CPP and the Obama
Administration’s other greenhouse gas regulation efforts. (92) Since that time, the EPA has moved aggressively to delay and
roll back the Obama Administration’s progress.
a. Affordable Clean Energy Rule and Oil and Gas Regulation Roll-backs
In October 2017, the EPA proposed to repeal the CPP, without offering a replacement. (93) Several months later the EPA
solicited comment on a potential replacement rule, (94) and finally, in August 2018, proposed the Affordable Clean Energy
(“ACE”) Rule to replace the CPP. (95) Unlike the CPP’s sector-wide approach to emissions reduction, the ACE Rule considers
only the “best system of emission reduction” that can be applied at a particular source. Consequently, it requires only limited
heat rate improvements at coal-fired power plants. (96)
With regard to the EPA’s separate 2016 rule establishing new source performance standards for fugitive emissions of methane
and other air pollutants from oil and gas sources, (97) the Agency initially sought to temporarily stay implementation of the rule
“pending reconsideration,” under the Clean Air Act Section 307(d). (98) However, the D.C. Circuit vacated that stay, blocking
the EPA’s immediate rollback efforts. (99) Although the EPA also proposed a two-year stay while it reconsiders the 2016 rule,
(100) it never finalized that proposal, but instead has proposed a marked weakening of the rule. (101)
Finally, regarding existing sources of oil and gas methane, in March 2017, the EPA withdrew the ICR for information on
equipment and emissions at oil and gas operation sites, (102) and several states have sued the EPA for failing to move forward
with regulations to curb methane emissions from these sources. (103)
b. Roll-backs of Mobile Source Regulations
The Trump Administration has also been working on roll-backs to greenhouse gas emission reductions from mobile sources.
As regards passenger cars, in April 2018, the EPA withdrew its January 2017 Final Determination, and announced it would
reconsider the 2022-25 mobile emission standards. (104) Several months later, the EPA issued a new Proposed Rule, the
“Safer and Affordable Fuel-Efficient Vehicles Rule,” proposing to freeze fuel economy standards and greenhouse gas emission
standards for passenger cars and light trucks at 2020 levels for model years 2021-2026. (105) For its part, California has
announced it will not be undertaking such a re-evaluation, but the EPA is seeking to use this process to revoke California’s
Clean Air Act waiver–and thereby remove California’s independent authority to regulate greenhouse gases from mobile
sources under the Clean Air Act. (106)
As for heavy-duty trucks, although the EPA’s 2016 truck standards included “glider vehicles,” (107) the EPA has proposed to
exempt these vehicles from the standards, which will leave old, less efficient and more polluting engines on the road for many
years. (108) The 2016 standards also provided important requirements for the trailer component of trucks that improve fuel
efficiency and reduce greenhouse gas emission, but the EPA is revisiting that aspect of the standards for trailers. (109)
Finally, as regards aircraft emissions, in pending litigation challenging the biogenic carbon dioxide component of the aircraft
endangerment finding, the EPA has obtained several abeyance orders on the grounds that the parties are discussing a
potential resolution, which likely signals that the EPA has no intention of moving forward with implementing regulations. (110)
c. The EPA’s Broader Roll-back of Science-Based Decision-Making
The Trump Administration’s EPA has also launched initiatives that pose enormous threats to the Agency’s regulation of
pollutants under the entire NAAQS program. These include: (a) a Memorandum suggesting a new and more restrictive view of
the NAAQS program; (111) (b) a Proposed Rule, which, if finalized, would prohibit the EPA from considering vital public health
studies in NAAQS decision-making; (112) and (c) an Advanced Notice of Proposed Rule-making concerning the manner in
which the EPA undertakes cost-benefit analysis, suggesting the EPA might issue uniform regulations elevating compliance
costs, and undermining the consideration of the environmental benefits of NAAQS and other regulations. (113) Taken together,
these EPA initiatives reflect a fundamental assault on the Agency’s decades-long legacy of protecting the American people
from the harmful effects of air pollution.
It remains to be seen how far the Trump Administration will get in fulfilling its deregulatory agenda. Decided cases thus far
suggest that there may be judicially imposed limits on its efforts to elide its statutory mandates and elevate industry interests
above public health and the environment. (114) However, once the Trump Administration leaves, and the EPA is empowered to
once again carry out its statutory mandates, it will be faced with both unraveling the damage wrought, while at the same time
determining anew how to bring the Act to bear on the climate crisis.
At that time, the EPA should not simply return to the Obama Administration’s approach to greenhouse gas regulations. As the
preceding discussion demonstrates, that sector-by-sector approach simply will not bring about the emission reductions
necessary within the timeframe they are needed. Only through the NAAQS program can the EPA work toward the overarching
objective of protecting human health and welfare from the threats posed by greenhouse gas emissions. Moreover, any notion
that proceeding with an incremental approach would allow faster progress with fewer litigation and other delays than pursuing a
greenhouse gas NAAQS has been shattered by the ferocious litigation assault that the fossil fuel and power industry and its
state allies have waged against the CPP and other regulatory initiatives to date.
Rather, when the EPA returns to faithfully implementing the Act, it should restore the central role of science in the Agency’s
decision-making by finally implementing a greenhouse gas NAAQS. As the following sections explain, such a NAAQS is the
Act’s best tool for regulating greenhouse gases.
At the same time, developments in recent years have made implementing a greenhouse gas NAAQS more straightforward,
helping to resolve concerns raised as to whether the global nature of greenhouse gas emissions and climate change make a
greenhouse gas NAAQS feasible. This Part briefly outlines the NAAQS program, and then explains how, and why, a new EPA
should move forward with a greenhouse gas NAAQS as rapidly as practicable.
Although the Clean Air Act has multiple and overlapping programs to address pollution at the individual plant, vehicle class,
and industry sector level, only the NAAQS program requires the EPA to achieve the overarching objective of protecting public
health and welfare from the most pervasive forms of air pollution emitted from “numerous or diverse” sources.
The NAAQS comes into play once the EPA makes a threshold finding that a pollutant, which is present in the ambient air due
to “numerous or diverse mobile or stationary sources,” “cause[s] or contribute[s] to air pollution which may reasonably be
anticipated to endanger public health or welfare.” (115) For greenhouse gases, the EPA made that finding for certain mobile
sources in 2009, (116) and since that time has consistently reiterated that greenhouse gases endanger public health and
welfare. (117)
Once an air pollutant is listed as a NAAQS pollutant, the EPA has one year to issue “air quality criteria” that reflect “the latest
scientific knowledge useful in indicating the kind and extent of all identifiable effects on public health or welfare which may be
expected from the presence of such pollutant in the ambient air, in varying quantities.” (118) Pollutants for which criteria have
been identified are known as “criteria” air pollutants, and the current six “criteria” pollutants are lead, ozone, carbon monoxide,
sulfur oxides, nitrogen oxides, and particulate matter. (119)
At the time these criteria are established, the EPA must also propose primary and secondary air quality standards; these are
the National Ambient Air Quality Standards, or NAAQS. (120) Primary standards are target concentrations of the pollutant in
the air, “the attainment and maintenance of which… are requisite to protect the public health.” (121) Secondary standards are
“the level of air quality” necessary to “protect the public welfare” (122)–expressly defined to include, inter alia, “effects on soil,
water, crops, vegetation, manmade materials, animals, wildlife, weather, visibility, and climate” (123)–from the adverse effects
of “such air pollutants in the ambient air.” (124) The EPA is not permitted to consider cost in determining the standards
necessary to protect public health or welfare. (125)
Once the primary and secondary NAAQS have been established, the EPA, with input from the states, must designate
geographic areas of the nation as being in “attainment”–that is, areas that meet the “national primary or secondary ambient air
quality standard for the pollutant”–or “nonattainment”–that is, areas that do not meet one or both of those standards. (126) This
process may take up to three years to complete. (127)
For areas designated as nonattainment, the EPA is required to determine the dates by which attainment can be achieved.
(128) With respect to a primary air quality standard, the Act provides that ten years is the longest period that may be provided
for reaching attainment. (129) Where an area’s nonattainment designation is with respect to a secondary standard, by contrast,
the EPA must choose the date “by which attainment can be achieved as expeditiously as practicable.” (130) Under the NAAQS
program, the states, and their air quality regions, then play the leading role in bringing about compliance with the NAAQS.
Once the EPA has made its designations, each state must prepare–within three years–a SIP to obtain “implementation,
maintenance and enforcement” of the standards. (131) For nonattainment areas, these plans must include, inter alia, “the
implementation of all reasonably available control measures as expeditiously as practicable….,” (132)
As a practical matter, these broad mandates call for states to take action to reduce emissions on many fronts–from not only
power plants, but also commercial and residential buildings, the transportation sector, the agricultural sector and elsewhere.
Although the myriad of programs and approaches states may take to reduce emissions of listed pollutants are beyond the
scope of this Article, the salient point is that the NAAQS program activates the widest possible approach to tackling these
emissions with maximum flexibility to choose those measures, across multiple sectors, which will allow each state to achieve
SIP emission reduction requirements. (133)
Importantly for purposes of envisioning a greenhouse gas NAAQS, the Clean Air Act also requires that each SIP address
pollution that crosses state lines. Thus, under Section 110(a)(2)(D), each SIP must prohibit sources from emissions “which will
contribute significantly to nonattainment in, or interfere with maintenance by, any other State with respect to any such national
primary or secondary ambient air quality standard….” (134)
The existing NAAQS have brought about enormous reductions in NAAQS pollutants, while also providing large economic
benefits. (135) Because one of the main objections to any NAAQS–and especially over greenhouse gases–concerns the
overall economic impact on regulated businesses, it also bears emphasizing that these benefits have been achieved during
periods of rapid economic growth: the EPA currently states on its website, “[f]rom 1970 to 2015, aggregate national emissions
of the six common pollutants alone dropped an average of 70 percent while gross domestic product grew by 246 percent.”
Greenhouse gases have several distinguishing characteristics from the existing criteria air pollutants. While some criteria
pollutants travel across state–and even international–borders, existing NAAQS pollutants’ impacts are all closely tied with
where the pollutants are ultimately located, and thus the EPA has been able to set localized pollution concentrations as
attainment objectives.
Greenhouse gases are different. They are broadly dispersed in the atmosphere, not staying within one state, or even the
United States, and their impacts are not tied to pollutant concentrations in any one area. This means that, unlike other NAAQS
pollutants, attainment cannot be measured based on local pollution conditions alone. Moreover, while it has proven difficult to
reach attainment for some of the existing NAAQS pollutants, it is apparent that it will take multiple decades, and require
significant changes to many aspects of the economy as well as those of countries around the world, to reduce greenhouse gas
concentrations to safe levels–regardless of how quickly emissions are reduced.
Relying on these distinguishing characteristics, some have argued that greenhouse gases are not suited for regulation under
the NAAQS program. (137) The issues can be framed in many ways but come down to the same fundamental question: given
the unique nature of greenhouse gases, can the EPA craft a greenhouse gas NAAQS which fits sufficiently within the NAAQS
framework? Or, put another way, would a reviewing court conclude that a greenhouse gas NAAQS is so different from other
NAAQS regulations–and so far-reaching–that Congress could not have intended the EPA to impose it under the existing
statutory scheme? (138)
One way to approach that question would be to focus on the economic implications of a greenhouse gas NAAQS. Some recent
Supreme Court precedents suggest that where an agency initiative will have major economic impacts, the Court will be
skeptical that Congress authorized the agency to act unless the statutory language is unambiguous. (139) For example, in FDA
v. Brown & Williamson Tobacco Corp., the Court concluded that the Food and Drug Administration’s power to regulate drugs
did not encompass the power to regulate tobacco products, because the underlying statute did not make clear that Congress
intended to give the Agency such sweeping authority. (140)
Similarly, in UARG the Court rejected the EPA’s effort to regulate greenhouse gases from certain sources under the Clean Air
Act’s Title V and PSD programs in part on the grounds that “it would bring about an enormous and transformative expansion in
the EPA’s regulatory authority without clear congressional authorization.” (141) The same charge is likely to be levied against a
greenhouse gas NAAQS.
This line of attack should not be an impediment to a greenhouse gas NAAQS, for two reasons. First, unlike the programs at
issue in UARG, the NAAQS program is designed precisely to address pollutants, like greenhouse gases and the other NAAQS
listed pollutants, emitted from “numerous or diverse mobile or stationary sources.” (142) Congress thus plainly anticipated that
through such regulation the EPA would, in fact, impact many activities. Moreover, by directing the EPA to take into account the
“latest scientific knowledge” relevant to the “kind and extent of all identifiable effects of public health or welfare which may be
expected from the presence of such pollutant in the ambient air,” 42 U.S.C. [section] 7408(a)(2), Congress also contemplated
that there might be new economic effects where the science reveals a new air pollution threat. Accordingly, a greenhouse gas
NAAQS would not expand the EPA’s role in the unanticipated manner the Court was concerned about in UARG. (143)
Second, the EPA’s regulation of the existing NAAQS already has far-reaching economic impacts. Indeed, the Supreme Court,
in Whitman v. American Trucking Assns., Inc., has rejected a claim that the EPA exceeded its power in setting NAAQS without
taking cost considerations into account. (144)
Whitman concerned the EPA’s revised NAAQS for particulate matter and ozone. Petitioners claimed the EPA was required to
consider economic implications when revising NAAQS, and that in any event the NAAQS program constituted an
unconstitutional delegation of legislative authority to the EPA. (145) Rejecting both arguments, the Supreme Court unanimously
found that the EPA may not consider costs in setting NAAQS, and that the Agency’s power to make NAAQS determinations
raises no serious constitutional concerns. (146)
This outcome should resolve any similar attack on a greenhouse gas NAAQS. Thus, while establishing and implementing a
NAAQS may have far-reaching economic implications, the Court’s ruling in Whitman makes clear that Congress gave the EPA
precisely that power in the NAAQS program. (147)
Moreover, it bears emphasizing that the EPA has been able to implement the existing NAAQS without adverse economic
effects, and there is no reason to assume a greenhouse gas NAAQS would be different. To be sure, there will necessarily be
large-scale economic adjustments as the nation moves away from a fossil fuel economy to one driven by renewables.
However, the engines of economic growth in the energy industry–a significant source of greenhouse gas emissions–are the
same renewable energy sources that will be central to a greenhouse gas NAAQS program. Solar jobs are growing faster than
any other job sector, and wind and solar energy continue to account for the largest areas of new energy growth across the
economy. (148) Moreover, existing technologies are available to make this transition rapidly, and once the development of new
technologies–which the Act is expressly designed to foster (149)–are considered, as several studies have concluded, there is
no reason that the transition to a 100% renewable energy economy cannot be achieved within several decades. (150)
At bottom, as the nation’s experience with existing NAAQS has shown, the economy can and will adjust to the regulatory
structure necessary to achieve a greenhouse gas NAAQS. The Act contains the necessary flexibility to ensure that the nation
can move toward a NAAQS as expeditiously as possible, without hampering the nation’s ability to continue to thrive as it has
under all the existing NAAQS.
Nonetheless, it remains inevitable that the unique nature of greenhouse gases will raise issues that have not been addressed
in prior NAAQS or the cases considering them. The first set of issues concerns how the EPA will formulate the NAAQS, and
how to comply with the statutory requirement for attainment of a primary standard within ten years. As section 1 below
explains, the fact that it will require multiple decades to stabilize the climate to the point where greenhouse gases no longer
endanger public health and welfare is not an obstacle to a greenhouse gas NAAQS.
The second set of issues concerns how the EPA will address compliance with a greenhouse gas NAAQS, given the global
nature of the climate change problem caused by greenhouse gas emissions. As detailed in section 2 below, particularly in light
of the Paris Agreement, the work that has been done on climate budgets, and the Supreme Court’s decision in Homer, the EPA
can rely on existing Clean Air Act provisions that consider pollution that crosses state and national boundaries in designing a
program whereby each state makes allocated reductions in emissions to contribute to greenhouse gas emission attainment
1. The Time Period Necessary to Achieve Attainment is No Impediment to a Greenhouse Gas NAAQS
a. What a Greenhouse Gas NAAQS Could Look Like
In order to address the various objections to a greenhouse gas NAAQS, one must begin by considering what such a NAAQS
might look like. A NAAQS does not consist solely of a “level”–that is, a concentration of pollutants in the ambient air–but also
an averaging time, and a “form.” The “averaging time” specifies the span of time across which the amount of a pollutant in the
air will be averaged. (151) For example, some NAAQS require a certain average annual level, while others require a certain
average daily level.
The “form” of a NAAQS, in turn, describes how compliance with the level will be determined within the averaging time. The
form often includes an element allowing for exceedance of the standard, for a certain number of times over the averaging
period. (152)
Under existing NAAQS these elements are used in combination to address the specific health and welfare effects of different
pollutants. For instance, different levels can be set in relation to different averaging times to capture the health and welfare
effects associated with shorter- and longer-term exposures to specific pollutants. (153)
In contemplating a greenhouse gas NAAQS, a particularly useful model to consider would be the most recent NAAQS the EPA
promulgated for lead. For that standard, based on the close relationship between lead levels in children and effects on IQ, the
EPA determined that “an allowable airborne lead-related loss of two IQ points should be used to set the NAAQS standard.”
(154) To achieve that objective, the EPA established a lead air exposure level, and then found that “the appropriate averaging
time for the air lead level standard is a rolling three-month period with a maximum (not-to-be-exceeded) form evaluated over a
period of three years.” (155)
For a greenhouse gas NAAQS, the endangerment finding, and the 2015 Paris Agreement, provide the EPA with the basis for
determining the first part of the NAAQS. Thus, the EPA has already determined that greenhouse gases endanger public health
and welfare, and in the Paris Agreement, the United States and the rest of the world’s nations agreed that to protect the planet
from these dangers, humanity must hold “the global average temperature to well below 2[degrees] Celsius above pre-industrial
levels and pursue efforts to limit the temperature increase to 1.5[degrees] Celsius above pre-industrial levels….” (156) Thus,
just as the lead NAAQS sought to determine the necessary limitations on airborne lead exposure to avoid a loss of two IQ
points, a greenhouse gas NAAQS would be set based on the limitations on greenhouse gases necessary to achieve no more
than a 1.5[degrees] Celsius increase in temperatures.
b. How a Greenhouse Gas NAAQS can be Formulated
In order to translate a greenhouse gas NAAQS temperature objective into a greenhouse gas standard, the EPA will have to
determine the target concentrations of greenhouse gases necessary to keep global temperatures below the target level–just
as, with lead, the Agency had to find the level of airborne lead exposure that would keep IQ levels from dropping more than two
IQ points. As a threshold matter, because current greenhouse gas concentration levels are far above what is necessary to
stabilize the climate, it is inevitable that these standards must be set far below current levels, which will mean that the entire
country will immediately be in “nonattainment”–that is, out of compliance with the standard. (157)
This status, in turn, would trigger the Act’s Section 172 provisions for nonattainment areas, under which the EPA must establish
an attainment date for the primary standard that may be “no greater than 10 years from the date of designation as
nonattainment, considering the severity of nonattainment and the availability and feasibility of pollution control measures.” (158)
The statute contains no similar deadline for the secondary standard.
In light of current greenhouse gas concentration levels, and the long-lived nature of greenhouse gases in the atmosphere,
there are currently no measures the EPA could require that would achieve attainment for greenhouse gases on this ten-year
primary standard timetable. This is because even if emissions of carbon dioxide and other long-lived pollutants were cut rapidly
to zero, it would still take longer than ten years for atmospheric concentrations to fall to below the primary standard.
Consequently, this statutory deadline for attainment has been the basis for one of the arguments against the suitability of
greenhouse gases for NAAQS designation. In short, the argument goes, because the NAAQS program requires attainment in
no more than ten years, and that cannot be achieved for greenhouse gases, the statute must not permit a greenhouse gas
NAAQS. (159)
To the contrary, as the following subsections explain, this deadline is no impediment at all. (160)
i. The EPA Could Design a Greenhouse Gas NAAQS that Meets the Deadline for a Primary Standard
Although it will take longer than a decade to reach attainment for greenhouse gases, the EPA could design a greenhouse gas
NAAQS that satisfies the requirements for a primary standard. Specifically, one option is for the EPA to rely on the “averaging”
feature of a NAAQS, as the EPA has done for other pollutants. (161) Under this approach, while the EPA would set binding
benchmarks to maximize reductions and insure “reasonable further progress” on a strict timetable toward attainment, (162) the
final attainment level requisite to protect the public health might not be achieved for several decades or even longer.
For several existing NAAQS, the unique nature of the pollutants has led the EPA to measure attainment by considering
average pollutant levels for as long as three years. (163) As has been done for other NAAQS, the three elements of a NAAQS-level, form and averaging time–could be used to structure a NAAQS reflecting the specific harm caused by climate pollutants.
The averaging time for a greenhouse gas NAAQS today could reasonably span decades. Although this is a far longer
averaging time than for other NAAQS pollutants, the approach may be appropriate given both the long-lived nature and effects
of carbon dioxide and other climate pollutants, and the long-term strategies necessary to protect public health and welfare.
Because the EPA has long tailored averaging times to the effects of particular pollutants, it would be within its authority to
follow the same course with greenhouse gases, relying on a longer averaging time to reflect the necessarily slow atmospheric
response of even aggressive steps to curb emissions of carbon dioxide and other long-lived pollutants.
Moreover, such an averaging time could be combined with a form that would comply with the Act’s standard for attainment
within ten years. In particular, the form could allow a certain number of decades of non-attainment over the long averaging
period. If the resulting standard, for example, allowed for seventy years of non-attainment over an averaging time of onehundred years, then so long as attainment has been achieved in year seventy and maintained for the following thirty years,
states will have been in attainment over the entire period.
Assuming, for purposes of discussion, that the EPA determined that the appropriate attainment level is 350 parts-per-million
(ppm) of GtC[O.sub.2eq], (165) the Figure below shows what this might look like.
The challenge of such an approach, of course, would be that there would be no way to determine, in year ten, whether states
had reached “attainment,” because that would only be quantifiable at the end of the averaging period. However, by establishing
binding benchmarks over the averaging period, reflecting the greenhouse gas concentration targets that would need to be
reached at, for example, each ten-year interval in order to achieve the ultimate standard, the EPA could ensure “reasonable
further progress,” (166) “as expeditiously as practicable,” (167) towards the attainment goal. Thus, the EPA would model and
establish shorter-term concentration targets, reflecting the emissions reductions necessary to ensure that the country remains
on track toward the long-term concentration goal over the full averaging period. (168)
In sum, given that the EPA has some flexibility in setting a NAAQS, including the averaging and form elements, there is no
reason that the requirement for attainment within ten years should stand in the way of a greenhouse gas NAAQS primary
ii. The EPA has Discretion to Establish a Secondary NAAQS for Greenhouse Gases that Will Not Be Fully Attained for
To be sure, the long-term averaging approach would be novel. However, even if a reviewing court were to find that the statute
does not permit such a long averaging period for a primary standard, there would still be the secondary NAAQS. Once the EPA
establishes air quality criteria, the Agency must establish not just primary standards necessary to protect public health, but also
the secondary standards necessary to protect public welfare, (169) which is defined to expressly include effects on “weather,
visibility, and climate.” (170)
Because the secondary standard does not contain a specific attainment deadline, such a standard for greenhouse gas
emissions would be–relatively speaking–more straightforward. The EPA would issue standards that will satisfy the ultimate
attainment goal and would determine a pathway toward that goal “as expeditiously as practicable,” (171) considering the
emission reductions necessary for the United States to make an appropriate contribution to reducing worldwide emissions over
That leaves the question as to whether the EPA would have the authority to impose a secondary standard even if there were
no method to appropriately craft a primary standard. Given how the Supreme Court addressed an analogous statutory
interpretation question in UARG v. EPA, (172) the answer is yes. Thus, if the EPA establishes primary and secondary
standards for greenhouse gases, even if a reviewing court were to determine that the primary standard is not allowable, that
should still leave the secondary standard intact. (173)
UARG concerned the regulations the EPA crafted to address greenhouse gas emissions under the Act’s Title V and PSD
permitting programs. (174) The Clean Air Act Section 302(j) defines “major” sources of air pollution to include any stationary
source emitting more than 100 tons per year of “any air pollutant.” (175) The EPA had concluded that since the term “air
pollutant” includes greenhouse gases, the Act requires the Agency to regulate these emissions from major sources. (176)
However, compared to other regulated pollutants, a far greater number of pollution sources emit greenhouse gases above the
statutory threshold for regulation, and thus, according to the EPA, a literal application of the “major source” standard for
greenhouse gas emissions would have encompassed millions of sources. (177) To address that regulatory burden, the EPA
created much higher thresholds for greenhouse gases–the “tailoring rule”–on the grounds that applying the statute to
greenhouse gases would have been otherwise unworkable. (178)
In UARG, the Supreme Court rejected this approach as an impermissible “rewriting of the statutory thresholds,” which must be
done by Congress, not by the EPA. (179) In the majority’s view, the fact that the term “air pollutant” encompassed greenhouse
gases under the “Act-wide definition” does not dictate whether the same term includes greenhouse gases under these
programs. (180) And because the parties agreed that it would be an absurd result to read the statute as requiring permits for
the millions of sources that would arguably be covered at the statutory thresholds, the Court found, Congress must not have
intended the term “air pollutant” in the definition of “major sources” to encompass greenhouse gases. (181)
The question then remained as to whether the Court’s reading of these specific provisions excluded the EPA from engaging in
the regulation of greenhouse gases under these permit programs at all. In particular, Section 165(a)(4) of the PSD program
requires that covered facilities must impose the “best available control technology [BACT] for each pollutant subject to
regulation.” (182) Petitioners argued that if the term “air pollutant” in the definition of “major source” did not include greenhouse
gas emissions, the term “pollutant” in the BACT provision necessarily also excluded greenhouse gas emissions–a result which
would mean that even if a plant were a “major source” due to emissions of other pollutants, it would not be subject to
greenhouse gas PSD BACT requirements. (183)
However, just as the Court had rejected the EPA’s effort to interpret the term “air pollutant” consistently throughout the Act, the
Court also rejected the view that its conclusion about the proper reading of covered pollutants under the definition of a “major
source” dictates the scope of the term throughout the PSD program. (184) Rather, the Court looked at the specific provision at
issue, and concluded that, under the BACT provision, the EPA could reasonably interpret the requirement to impose BACT for
“each pollutant subject to regulation under [the] Act” (185) to include greenhouse gas emissions, without any absurd result.
Thus, with regard to sources that the EPA regulates as major sources due to their emissions of other pollutants, the Court
found that the EPA can require those sources to be subject to BACT for the control of greenhouse gas emissions. (186)
Applying that reasoning here, even if a court were to conclude that the ten-year deadline for a primary standard indicates that
Congress did not intend a primary standard for greenhouse gases–because, like the unachievable numeric limit at issue in
UARG, there is no practical way to achieve that primary standard deadline–that would not resolve whether greenhouse gases
can be regulated under the NAAQS program altogether. It would only resolve that the EPA may not impose a primary standard.
To be more precise, because Section 172(a)(2)(A) provides that “[t]he attainment date for an area designated nonattainment
with respect to a national primaiy ambient air quality standard” (187) shall be no longer than ten years, this result would simply
mean that, as in UARG, the obligation to impose a “national primary ambient air quality standard”–defined under the Act as the
“air quality standards the attainment of which… are requisite to protect the public health” (188)–would not apply to greenhouse
The question would then remain whether greenhouse gases can be regulated under other portions of this Clean Air Act
program. And just as the Court in UARG found that these emissions can be regulated under the BACT provision, there is no
impediment to their regulation under the NAAQS program through a secondary standard.
Indeed, Congress defined a “secondary ambient air quality standard” differently from a primary standard, providing that the
term refers to the “level of air quality the attainment and maintenance of which… is requisite to protect the public welfare [which,
again, includes the climate (189)] from any known or anticipated adverse effects associated with the presence of such air
pollutant in the ambient air.” (190) Following the reasoning in UARG, and given that the Act provides no specific deadline by
which the EPA must require attainment for a secondary standard, there is no reason the term “air pollutant” in the context of a
secondary standard could not include greenhouse gases, regardless of its application to a primary standard. (191)
In sum, just as the Court in UARG concluded the definition of the term “pollutant” can differ within different parts of the PSD
program, there is no reason the definition could not similarly differ under the different parts of the NAAQS program–that is, the
primary, as distinguished from the secondary standard. Furthermore, unlike the Tailoring Rule, where the Court found the
EPA’s reliance on a threshold to exclude certain sources from regulation to be impermissible in the absence of any indication
that this is what Congress had in mind, here the primary and secondary standards are simply different forms of protection, set
out in the statute itself, for regulating the same sources. Thus, the fact that Congress chose to direct the EPA to consider two
different forms of protection indicates that even were a court to reject the promulgation of a primary standard in this instance, it
would still remain within the EPA’s authority to impose the secondary standard.
To be sure, a faithful implementation of even only a secondary standard would still require sweeping changes across the many
sectors with significant greenhouse gas emissions. Consequently, opponents are likely to argue that, in light of UARG even this
more limited approach would go beyond what Congress intended in the NAAQS program.
This argument will have no force. In particular, the problem in UARG was that the definition at issue–of a “major source”–could
not be reasonably applied to greenhouse gases in light of the levels of pollution requiring regulation, and it was on that basis
that the Court found the term “air pollutant” in the definition of “major source” did not include greenhouse gases. (192) In the
NAAQS program, by contrast, Congress expressly provided that in setting a secondary standard, the EPA must determine the
pollutant levels “requisite to protect the public welfare,” which Congress expressly defined as including “effects on… climate,”
(193) and required the EPA to do so only “as expeditiously as practicable.” (194)
Thus, contrary to the situation in UARG, through the secondary standard Congress itself determined that the EPA must
regulate pollutants–like greenhouse gases–causing adverse impacts on the climate. Given that the EPA has already
determined that these pollutants are adversely impacting the climate (and thus public welfare), it will be well within the Agency’s
authority to impose a greenhouse gas NAAQS, which, the Court has also made clear, must be imposed irrespective of
economic factors. (195) In sum, there would be no substantial argument that the EPA lacks the authority to regulate
greenhouse gases under a secondary standard, irrespective of how the authority to impose a primary standard is resolved.
In conclusion, the ten-year deadline for attainment of a primary NAAQS is not an obstacle to a greenhouse gas NAAQS. The
EPA can design a greenhouse gas NAAQS with an average and form that complies with the ten-year primary standard.
Alternatively, it may impose a secondary standard designed to reach attainment as expeditiously as possible.
2. The Unique Nature of the SIPs That Will Address Greenhouse Gas Emissions Also Poses No Obstacle to a Greenhouse
Another principal argument against a greenhouse gas NAAQS has been the claim that there is no reasonable approach to
apportioning greenhouse gas emission reductions, given that emissions all over the world have the same impacts on climate
change and their well-mixed nature. (196) Developments over the past few years also address these concerns. First, with
regard to international emissions, the 2015 Paris Agreement gives the EPA the framework to determine the greenhouse gas
reductions necessary in the United States to achieve a greenhouse gas NAAQS. Second, once a United States carbon budget
is established, the Supreme Court’s 2014 decision in Homer demonstrates that the EPA has the necessary discretion to
reasonably apportion emission reductions within each nonattainment area. Moreover, the significant work that went into
developing the CPP provides a critical starting point from which the EPA can build in order to develop a NAAQS program that
will address greenhouse gas emissions in the context of state SIPs. (197)
One obvious obstacle to a greenhouse gas NAAQS has been how the EPA would determine the levels of greenhouse gas
emission reductions necessary to move towards attainment. With traditional NAAQS pollutants, which have more localized
(even if cross-border) effects, the EPA can set attainment levels, and air quality agencies can develop SIPs that will achieve
that end level of attainment (again, taking into account cross-border pollution) on the determined schedule. For greenhouse
gases, of course, there is no obvious approach to prescribing what each state must do to move toward attainment.
The significant research that has been done in recent years on carbon budgets addresses this threshold concern. In particular,
scientists have evaluated how much more greenhouse gases can be emitted into the atmosphere to avoid exceeding 1.5
Celsius of warming. (198) This body of research provides the EPA with a new tool on which to rely when evaluating the
emission reductions necessary to move toward attainment goals.
As with all NAAQS, the EPA will be charged with determining those emission reductions based on the best available science.
(199) For present purposes, it is sufficient to note that one recent scientific study concluded that to avoid exceeding 1.5 Celsius
of warming, the remaining carbon budget is approximately 477 billion tons, or approximately 13 years at current emissions
levels. (200) This will provide the EPA with the requisite baseline to develop a greenhouse gas NAAQS.
a. Clean Air Act Section 179B Calls on the EPA, in Considering SIPs, to Take Emissions from Outside the United States into
Account, and the Paris Agreement Provides a Framework for Approaching That Task
While determining a global carbon budget will provide the initial baseline from which to allocate carbon emission reductions, the
obvious next step requires the EPA to determine how much of those reductions will come from the United States, which will in
turn become the baseline from which to allocate reductions among states. (201)
The EPA’s authority to establish a United States allocation derives from Clean Air Act Section 179B, in which Congress
explicitly addressed the problem of taking pollution emitted from outside the country into account in the NAAQS program. (202)
In particular, Section 179B expressly provides for the EPA to approve SIPs that would otherwise comply with the Act “but for
emissions emanating from outside of the United States.” (203) Thus, if there is a reasonable basis on which the EPA can
determine the levels of emissions from outside the United States that are the obstacle to attainment for greenhouse gases,
they can be taken into account in establishing a greenhouse gas NAAQS. (204)
Five years ago, it was considerably more difficult to articulate how the EPA could make these determinations. First, how would
the EPA determine what portion of the carbon budget the United States would be limited to? Second, on what basis could the
EPA presume that other countries would take the steps necessary to reduce their own emissions in the manner required to
stay within the overall budget, and thus move the world toward attainment?
The carbon budget work discussed above, taken together with the 2015 Paris Agreement, significantly advance the feasibility
of such allocations and assumptions.
To achieve the Paris Agreement’s objectives, countries established “nationally determined contributions” (“NDCs”) reflecting
their commitments to necessary emission reductions. (205) To date, the initial NDCs are insufficient to achieve the Paris
Agreement’s goals. Thus, for example, one analysis indicates that the current United States NDC, which is “reducing its
greenhouse gas emissions by 26%-28% below its 2005 level in 2025 and to make best efforts to reduce its emissions by 28%,”
(206) is only about one-fifth of the reductions required for the country to make the necessary contribution to reducing
greenhouse gas emissions. (207) Collectively, the world’s existing NDCs are far below the requisite reductions required to
achieve the Paris Agreement’s emission temperature increase targets. (208)
However, the Paris Agreement’s “ratchet mechanism” expressly contemplates the submission of increasingly ambitious NDCs,
in order to limit warming to the temperature target set out in the Agreement. (209) Thus, given the temperature targets of the
Paris Agreement and the commitment of the world’s nations to achieving those targets, the EPA could reasonably assume that
countries around the world will, over time, take the necessary steps to reduce emissions sufficiently to move toward the
attainment objective. (210)
The Paris Agreement and the work on climate budgets thus provide the EPA with multiple avenues for determining the
domestic carbon budget it could rely on as a baseline to establish state NAAQS, as discussed in the next subsection. For
example, under the most ambitious approach, the EPA could look at all other nations’ NDCs at the time it conducts its analysis
and determine that the United States carbon budget should be the remaining emissions that would be available to reach
attainment, assuming those NDCs are not further strengthened. This would have the benefit of not requiring more ambitious
NDCs in order to achieve attainment, but, depending on the level of the NDCs at the time the EPA undertakes this evaluation,
such an approach may leave an unworkably small emissions budget for the United States.
Alternatively, the EPA might set a greenhouse gas NAAQS by relying on the United States’ then-current NDC as the country’s
emission goal, if that NDC were science-based and appropriate for reaching the temperature targets set out in the Paris
Agreement. Under this scenario, when the United States submits increasingly ambitious NDCs, as expressly contemplated by
the Paris Agreement, the NAAQS would be adjusted to reflect the latest emission reduction goals. The strength of this
approach would be that, if the NDC were science-based and sufficient, the EPA would not need to determine the United States
carbon budget, and instead would incorporate the NDC determined by the government as a whole.
As a third alternative, rather than relying on the NDCs, the EPA could rely on the carbon budget research work itself to
determine the levels of emissions reduction the United States must achieve to reach attainment, assuming each country
reduces its emissions to the levels required to meet the Paris Agreement’s goals, as each party to the agreement has
committed to do. As noted, present research suggests the United States budget to limit temperature rise to well below
2[degrees] Celsius averages 25 GtC[O.sub.2]eq to 57 GtC[O.sub.2]eq. (211) To even meet even these more moderate goals,
United States global emissions would need to peak by 2020, decline sharply thereafter, and typically reach zero net emissions
by 2050. (212)
This Article does not argue that the EPA should pursue any particular approach to the allocation question in order to set a
baseline carbon budget for the United States. Rather, these options merely serve to illustrate that, in light of the research on
carbon budgets and the 2015 Paris Agreement, the EPA can reasonably rely on Section 179B to determine the level of
greenhouse gas reductions that will collectively be required by the United States, by finding that the states will reach attainment
“but for emissions emanating from outside of the United States.” (213) The next section considers how that U.S carbon budget
can reasonably be allocated among the states. (214)
b. The Supreme Court’s Decision in Homer Demonstrates that the EPA Can Meaningfully Apportion Greenhouse Gas
Reductions Within the United States, and the Clean Power Plan Provides an Initial Structure from Which the EPA Can Frame a
Greenhouse Gas NAAQS
Once the EPA has determined the level of emission reductions the United States will need to achieve to move towards
attainment, the remaining task will be to apportion those reduction obligations among the states. Because each state’s
greenhouse gas emissions are well-mixed in the atmosphere, it is more challenging to consider how that apportionment might
be carried out for a greenhouse gas NAAQS than for the existing NAAQS pollutants. However, two developments in the past
five years suggest a possible path forward on this issue: the Supreme Court’s 2014 decision in Homer, and the CPP.
First, the Supreme Court explained in Homer that, in crafting the Clean Air Act, Congress recognized that “[a]ir pollution is
transient, heedless of state boundaries.” (215) Section 110(2)(D) of the Act addresses this problem, providing that state SIPs
must contain provisions to prohibit emissions that would “contribute significantly to nonattainment in… any other state….,” (216)
This “Good Neighbors” Provision addresses how emissions among the states may impact each state’s ability to implement its
respective SIPs.
Homer, the Supreme Court’s most recent case addressing cross-state air pollution, concerned how the EPA could
appropriately address upwind pollution traveling into downwind states. Relying on the Good Neighbors Provision, the EPA
crafted a regulation–called the Transport Rule–under which each upwind state meaningfully contributing to this problem would
be required to implement cost-effective pollution controls. In particular, under the EPA’s two-step approach, the Agency first
identifies which states contribute at least 1% of one of the NAAQS pollutants to a downwind state. Then, under step two, the
EPA determines the cost level at which the contributing states, taken together, would sufficiently reduce their contributions, and
crafts state emission budgets based on those results. (217)
The D.C. Circuit concluded that the EPA’s approach was impermissible because, among other concerns, it did not limit
emission controls within each state to the state’s proportional contribution to pollution in downwind states. According to the
majority opinion, the Agency had exceeded its discretion by focusing on the most cost-effective pollution reduction measures,
rather than limiting the regulations to what was necessary to reduce each state’s emissions based solely on those
contributions. (218)
In a 6-2 decision, the Supreme Court disagreed. Noting that the Good Neighbors Provision is aimed at eliminating “‘amounts’ of
pollution that ‘contribute significantly to nonattainment’ in downwind states,” the Court explained that the statute “calls upon the
agency to address a thorny causation problem: How should the EPA allocate among multiple contributing upwind States
responsibility for a downwind State’s excess pollution?” (219) Because the EPA’s approach to addressing that thorny problem-by limiting regulation to those states contributing more than 1% of a NAAQS pollutant to a downwind state, and then, among
those qualifying states, eliminating emissions based on cost-thresholds that apply uniformly across states and sources–was
“an efficient and equitable solution to the allocation problem,” the Court determined that it was a permissible approach under
the statute. (220)
Here, the EPA could similarly craft an “efficient and equitable solution to the allocation problem” as regards greenhouse gas
emissions, by determining the most cost-effective means to reduce those emissions, and using those results to develop state
emission budgets. Homer thus supports the proposition that the EPA should have sufficient discretion to apportion greenhouse
gas emission reductions among the states in a manner that will equitably address each state’s contribution to greenhouse gas
To be sure, the Court in Homer explained that the EPA may not require any one state to reduce pollution “more than the
amount necessary to achieve attainment in every downwind state to which it is linked.” (221) Subsequently, the D.C. Circuit
ruled in favor of several as-applied challenges to the Transport Rule, finding that the manner in which parts of the Rule
allocated pollution-reduction obligations meant that several states were impermissibly required to reduce pollution below the
levels necessary to ensure attainment in linked downwind states. (222)
The uniform nature of greenhouse gases makes this limitation irrelevant to a greenhouse gas NAAQS. In particular, all states
will be uniformly linked to each other, as each state will be contributing to all states’ greenhouse gas NAAQS exceedances.
(223) Thus, the disproportionate burdens which were at issue in Homer would not be present for a greenhouse gas NAAQS.
Second, the CPP, which is premised on modifications to SIPs in carrying out compliance, as provided in Section 111(d), could
also provide a useful framework for developing the SIP approaches necessary to implement a greenhouse gas NAAQS. (224)
In the CPP, the EPA began by determining the emissions reductions that could be achieved by implementing the Best System
of Emission Reduction (“BSER”) for power plants, as required by Clean Air Act Section 111. (225) Through that analysis, the
EPA calculated the overall emission reductions that each state must achieve, without dictating that those reductions come from
the power plants themselves. (226)
For a greenhouse gas NAAQS, the EPA’s analysis at this step of the process would be to determine the overall annual
greenhouse gas emissions coming from all sectors in the United States, and to compare that to the United States carbon
budget. Comparing those values will allow the EPA to determine the overall level of emission reductions necessary. (227)
For the CPP, in the next step of the process the EPA provided each state with “broad flexibility” as to the manner in which it
would achieve the required emission reductions. (228) In particular, although a state could simply choose to incorporate the
plant-specific performance requirements that the EPA had determined to be BSER, the state could alternatively adopt a
different approach, so long as it would achieve the same “state-specific CO2 goals.” (229) Thus, critically for comparing the
CPP to a greenhouse gas NAAQS, the CPP provided states “considerable flexibility” to determine both how to best allocate the
reduction goals and the timeframes for implementation. (230) The CPP also included programs to speed adoption of renewable
energy and energy efficiency measures that could help states achieve their emission reduction goals. (231)
Many of these elements can be appropriately modified for a greenhouse gas NAAQS. Thus, for example, applying the same
approach as in Homer, the EPA might determine the most cost-effective thresholds of measures that can be taken to
sufficiently reduce the country’s emissions to stay within the carbon budget. Applying these measures across sectors in each
state, the EPA could then reasonably allocate emission reduction targets among states.
Once that is accomplished, and relying on the CPP model, the EPA could then provide each state with flexibility in how it will
achieve the required emission reductions, along with federal programs–such as renewable energy and energy efficiency
initiatives–that will assist the states in meeting their goals. Under that approach, as with the CPP, each state would ultimately
be permitted to develop the SIP measures most appropriate for that state, as long as those measures will accomplish the
required emission reductions. And, with each state taking the required measures, the United States would be reducing its
emissions as necessary to make its appropriate contribution towards overall attainment goals. (232)
Putting these pieces together, then, it is apparent that the Act contains the necessary provisions to design and implement a
NAAQS for greenhouse gas emissions. First, the EPA would add greenhouse gases to the list of criteria air pollutants,
establish air quality criteria, and set primary and secondary standards. Second, the EPA would–either through reliance on
carbon budgeting research or through some other appropriate method–rely on Section 179B to determine the United States’
contribution toward greenhouse gas emission reductions over time. And third, the EPA would rely on Section 110(d) to
reasonably apportion those domestic emissions among the states.
The final concerns with a greenhouse gas NAAQS are whether such regulations would preclude action on greenhouse gases
under Clean Air Act Section 111(d) and whether, if the EPA were to move forward, Congress might amend the Clean Air Act to
remove the EPA’s power to regulate. (233) As this Part explains, neither of these concerns should be an obstacle to the EPA
finally proceeding with greenhouse gas NAAQS regulations.
Clean Air Act Section 111 provides that, upon listing a stationary source category, and identifying new source standards, the
EPA must also set such standards for existing sources in that category under Section 111(d), “for any air pollutant (i) for which
air quality criteria have not been issued or which is not included on a list published under” Section 108–the NAAQS program.
(234) The CPP was promulgated pursuant to this Clean Air Act authority.
When the EPA was promulgating the CPP, it was natural to ask whether, in light of this restrictive language prohibiting Section
111 (d) regulations for NAAQS pollutants, a greenhouse gas NAAQS would preclude the CPP. Years after the CPP was
issued, however, that concern has lost much of its force, for several reasons. First, while a pre-existing greenhouse gas
NAAQS may have precluded the CPP, the most reasonable reading of Section 111 (d) is that imposing such a NAAQS now
would have no effect on a pre-existing regulation under Section 111(d). In particular, the exclusion prevents a Section 111(d)
rule for pollutants as to which “air quality criteria have… been issued” previously, or which have been “included on [the] list” of
NAAQS. (235) Thus, the plain language suggests that if a Section 111 (d) Rule precedes a NAAQS, the 111 (d) Rule would not
be excluded by the NAAQS.
Moreover, any argument that a new greenhouse gas NAAQS could somehow eliminate a pre-existing Section 111(d) regulation
for greenhouse gases like the CPP would be inconsistent with both the text of this provision and the logic behind it. The text
addresses the EPA’s mandate to issue Section 111(d) regulations, confining that mandate to pollutants “for which [NAAQS]
have not been issued or which is not included on [the] list” of criteria air pollutants. (236) Nothing in that language states, or
even suggests, that if a NAAQS is issued after a Section 111(d) regulation, the Section 111(d) regulation somehow disappears.
It is also unclear how Congress would have intended such a result to work. Most importantly, under the NAAQS program, the
addition of a pollutant to the list of criteria air pollutants and issuance of air quality criteria are only the first steps towards the
control of such a pollutant–which does not occur until SIPs are approved several years later. Thus, reading this language to
immediately cancel a Section 111(d) regulation as soon as a pollutant is listed under Section 108 would mean that Congress
intended a significant gap in the regulation of the same pollutants that are so severe that they are found to endanger public
health and welfare. Nothing in the text or legislative history suggests such a counter-intuitive result. Rather, at minimum the
Section 111(d) regulation would remain in effect until the NAAQS regulation is implemented through SIP approvals.
Second, while it will take several years to implement the SIPs for a greenhouse gas NAAQS, the many years of delay
surrounding the CPP–which has been stayed since shortly after it was finalized–demonstrate that there is no basis to assume
that regulating under the Section 111 sector-by-sector approach can bring about emission reductions more quickly. Indeed, the
Trump Administration is now working to repeal the CPP or at least significantly weaken it. (237) Although there will be strong
grounds to challenge these regulatory roll-back efforts, the salient point is that these developments demonstrate there are no
longer likely to be significant timing gains to be had from regulating these sources’ greenhouse gas emissions through the CPP
rather than a NAAQS.
Finally–and perhaps most importantly–once SIPs that include greenhouse gas emissions are in effect, regulations under
Section 111(d) should no longer be necessary, because the sources that would have become subject to 111(d) source
regulations will all be regulated under the NAAQS program. Thus, although a greenhouse gas NAAQS may preclude the EPA
from issuing new Section 111(d) rules for those pollutants following the NAAQS promulgation–the most important aspects of
those standards would simply be incorporated into the SIPs. (238)
That leaves the uncertain question as to the outcome of the CPP. If the current EPA finalizes the proposed repeal (239) and/or
completes its replacement rule limited to modest improvements of the plants themselves, (240) states and environmental
advocacy groups are likely to challenge the new regulation as contrary to the Act. If they prevail, the appropriate relief could be
for the Court to reinstate the CPP by vacating the repeal–in which case, the CPP would still precede a greenhouse gas
NAAQS, and remain in place. (241) On the other hand, if such a challenge were to fail, then it would be even clearer that there
is no meaningful trade-off to be made between the CPP and a greenhouse gas NAAQS.
To be sure, these outcomes remain uncertain, and regardless of the 111(d) exclusion, as a practical matter a new
administration may find itself faced with a choice between re-starting the process of regulating stationary sources on a sectorby-sector level under Section 111(d) or proceeding with a greenhouse gas NAAQS. For all the reasons discussed herein,
however, the argument that the EPA should avoid a greenhouse gas NAAQS to clear a path for more timely and efficient
regulation of greenhouse gases from stationary sources under Section 111 has far less force than it may have had years ago.
For all these reasons, concerns about the impacts of a greenhouse gas NAAQS on the EPA’s power to regulate these
emissions under Section 111(d) should not stand in the way of the EPA finally moving forward.
A last major objection posed to a greenhouse gas NAAQS concerns the possibility that Congress might amend the statute to
expressly preclude the EPA’s authority to issue a NAAQS for greenhouse gases. The recent election results, which have given
Democrats control of the House of Representatives, certainly alleviates that concern in the short-term. More importantly,
however, because the decade-long uncertainty about the scope of the EPA’s power poses obstacles to other efforts to address
the climate crisis, this concern also should also not deter the EPA from moving forward. (242)
For example, numerous municipalities have recently filed tort suits seeking to hold fossil fuel companies financially responsible
for the harms their activities are causing through rising sea levels, severe weather, and other consequences of climate change.
(243) Defendants have been seeking dismissal of these cases by arguing, inter alia, that plaintiffs’ claims are barred in light of
the EPA’s authority to regulate greenhouse gases under the Clean Air Act, and two cases have already been dismissed largely
on that basis. (244)
To be sure, in 2011 the Supreme Court ruled that federal nuisance claims against power plants over greenhouse gas
emissions are displaced by Clean Air Act Section 111, because that provision expressly provides for the EPA to regulate those
plants’ greenhouse gas emissions (which it did with the CPP). (245) However, in more recent cases defendants and their allies
are arguing that even entities that are not regulated under Section 111 remain immune from tort liability, on the grounds that
any and all such regulation of greenhouse gases must be done by the EPA in light of its comprehensive power under the Clean
Air Act. (246)
If it turns out the EPA cannot enact a greenhouse gas NAAQS, these defenses to climate change tort suits will have less force.
Accordingly, resolving the scope of the EPA’s power to regulate under a NAAQS–even if it meant Congress expressly
removing that power–may be an improvement over the current status quo, under which the possibility of a greenhouse gas
NAAQS theoretically exists, but the EPA refuses to act.
Similarly, opponents of greenhouse gas regulation under other provisions of the Clean Air Act have referred to the EPA’s
unutilized authority to impose a greenhouse gas NAAQS to object to addressing the climate crisis with other tools in the Act
itself. For example, in seeking to restrict the EPA’s authority to address greenhouse gas emissions from aircraft, opponents
have argued that the EPA cannot act because the EPA has not acted to regulate greenhouse gases under the NAAQS
program. (247)
Accordingly, the current status quo arguably provides the worst of all worlds: no greenhouse gas NAAQS, but the outstanding
possibility of such regulations being used to oppose other regulatory efforts.
In short, it is painfully clear–more than ten years after the Supreme Court established greenhouse gases are an air pollutant
that the Clean Air Act is designed to address–that the fear of legislative change should not delay action to harness the Act’s
strongest tool to fight the largest air pollution threat facing the nation and the world. Indeed, given how close humanity has
come to the tipping point where the worst effects of climate change simply cannot be forestalled, (248) it matters less and less
with each passing year whether Congress removes a power that the EPA refuses to invoke.
At bottom, although the outcome may be uncertain, when the EPA returns to its science-based mission in a new administration,
it will be time to act on a greenhouse gas NAAQS. The worst outcomes–be it a legislative removal of the EPA’s authority, a
court ruling that the EPA has no power to act, or any other outcome that does not actually result in the outcome sought–will be
no worse than the current status quo, and can only provide guidance for what comes next. The world simply cannot wait
another decade to resolve any remaining questions about this crucial EPA power.
(*) Senior Attorney, Center for Biological Diversity Climate Law Institute and Professorial Lecturer in Law, George Washington
University Law School. Georgetown University Law Center, J.D. 1993. The authors thank Lisa Heinzerling, Sean Hecht, Kevin
Bundy, and Shaye Wolf for their valuable insight and thoughtful feedback. [c] 2019, Howard M. Cryst…
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