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November 2, 2016
Protecting Clean Air in National Parks and Wilderness Areas
In 1977, major amendments to the Clean Air Act (CAA)
increase” in the concentration of particulate matter (5 µg/m3
included provisions for the prevention of significant
annually, or a maximum of 10 µg/m3 during a 24-hour
deterioration (PSD) of air quality. The PSD provisions were
period) may be only about one-fourth the allowable
enacted for several purposes, including
increase in a Class II area (19 µg/m3 and 37 µg/m3,
respectively). The allowable increase of sulfur dioxide
to preserve, protect, and enhance the air quality in
concentrations in Class I areas is even more strictly
national parks, national wilderness areas, national
controlled as compared to the allowable increase in a Class
monuments, national seashores, and other areas of
II area.
special national or regional natural, recreational,
scenic, or historic value; [and]
As specified in the statute, the Class I areas consist of
certain federally protected sites that were in existence on
to insure that economic growth will occur in a
the amendments’ date of enactment, August 7, 1977. The
manner consistent with the preservation of existing
areas that were designated as Class I included national
clean air resources....
parks larger than 6,000 acres, national wilderness areas
larger than 5,000 acres, and certain other sites. Altogether,
Two significant aspects of the PSD provisions relate to
48 National Park System units (managed by the National
federal lands and federal land managers: the classification
Park Service, in the Department of the Interior);
of areas for air quality protection and management, and the
21 wilderness areas in the National Wildlife Refuge System
role of federal land managers in maintaining and improving
(managed by the Fish and Wildlife Service, in the
air quality under the CAA.
Department of the Interior); 86 wilderness areas in the
Classification of Areas
National Forest System (managed by the U.S. Forest
Service, in the Department of Agriculture); and
The PSD provisions establish classifications of air quality
1 international park (managed by a U.S.-Canadian
(42 U.S.C. §7472). Class I areas are those with the highest
commission) were designated as Class I areas—156 sites
air quality and whose air quality is most stringently
in all (see Figure 1).
protected. Class II includes all other areas, unless they are
designated “nonattainment” for one of the U.S.
The PSD provisions (42 U.S.C. §7474) established a
Environmental Protection Agency’s (EPA’s) National
process by which the states can change area designations.
Ambient Air Quality Standards. The CAA provides that in
However, the initial Class I areas cannot be redesignated.
areas designated as Class I, the “maximum allowable
Figure 1. Mandatory Class I National Parks and Wilderness Areas Under the Clean Air Act
Source: CRS, using data from EPA, “Visibility—Regional Haze Program,” at https://www.epa.gov/visibility/visibility-regional-haze-program.
Note: Territories other than the U.S. Virgin Islands are not shown because they contain no Class I areas.
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Protecting Clean Air in National Parks and Wilderness Areas
For new protected areas established after the enactment of
EPA).” (See http://www.nature.nps.gov/air/Pubs/pdf/flag/
the 1977 CAA amendments, the act does not provide for the
FLAG_2010.pdf.)
areas’ automatic designation as Class I. Rather, new
federally protected areas can only be redesignated as Class I
The CAA does not specify how close a new major source
by the state, under the process established in the CAA. The
must be to a Class I area to trigger the consultation
CAA does not specify which agency or official within the
requirement. The FLAG Report states, “Generally, the
state may redesignate an area as Class I; the legislation
permitting authority should notify the FLM of all new or
merely states in Section 164(a) that “a State may
modified major facilities proposing to locate within 100 km
redesignate such areas as it deems appropriate as Class I
(62 miles) of a Class I area. In addition, the permitting
areas.” The section requires public hearings and an analysis
authority should notify the FLM of ‘very large sources’
of the “health, environmental, economic, social, and energy
with the potential to affect Class I areas proposing to locate
effects of the proposed redesignation,” which must be made
at distances greater than 100 km.”
available for public inspection prior to redesignation. To
date, no state has redesignated as Class I any national park
The FLM’s role in CAA decisions is most explicit for, but
or wilderness area established after August 7, 1977.
is not limited to, Class I areas. FLMs also can be involved
in CAA decisions that affect Class II areas, particularly
when scenic vistas are a significant value for the areas.
To date, no state has redesignated as Class I any
According to the FLAG Report, similar criteria apply to
national park or wilderness area established after
Class II areas: “Under the Clean Air Act, the FLM formal
August 7, 1977.
‘affirmative responsibility’ role in the permitting process is
limited to the extent a proposed new or modified source
In addition to Class I and Class II, the statute envisioned the
may affect AQRVs in a Class I area.... Nevertheless, the
possibility of redesignating some areas to a less stringently
FLMs are also concerned about resources in Class II parks
protected Class III, but no state has done so.
and wilderness areas because they have other mandates to
Role of Federal Land Managers
protect those areas as well. The information and procedures
outlined in this document are generally applicable to
Under land management laws such as the National Park
evaluating the effect of new or modified sources on the
System Organic Act and the Wilderness Act, federal land
AQRVs in both Class I and Class II areas.”
managers (FLMs) are responsible for protecting the air
quality for the lands they administer. The CAA also
Besides requiring that major emitting facilities obtain pre-
provides FLMs with means and opportunities to protect air
construction PSD permits, the CAA sets a national goal of
quality for the lands they manage.
preventing future impairment of visibility in Class I areas
and remedying existing impairment. The states are to
An FLM is defined in the CAA as the Secretary of the
develop implementation plans (SIPs) demonstrating
department with authority over the lands in question. In
reasonable progress toward this regional haze goal at 10-
practice, the Secretary has delegated this authority to an air
year intervals. On May 4, 2016, EPA proposed revisions to
quality branch or to the official charged with direct
its Regional Haze Rule (81 Fed. Reg. 26942) that would
responsibility for the land in question. The CAA gives the
strengthen the role of FLMs in the development of these
FLMs certain roles and responsibilities in regulatory
SIPs by requiring states to consult with FLMs earlier in the
decisions that might affect air quality in federally protected
process of developing the plans.
areas.
Additionally, FLMs fulfill their responsibilities for
All CAA regulatory decisions require public notice of the
protection of AQRVs by participating in EPA’s
proposed actions and opportunity for comment. Many CAA
development of air quality regulations. For example, FLMs
provisions also require consultation with FLMs. For
may participate in scoping meetings and other public
example, EPA or the states must consult with FLMs of
forums as regulations are being developed. They also may
Class I areas regarding permits for new major sources of air
support scientific research on the sources and effects of air
pollution that might degrade the air quality of the areas.
pollution on federal lands and resources—for example, by
FLMs would have the opportunity to demonstrate that the
conducting projects to monitor AQRVs on federal lands and
increased pollution would harm the air quality, such as by
by participating in interagency research committees.
reducing visibility.
For Additional Reading
The FLM’s role is an advisory one. As noted in a 2010
For additional information, see CRS Report RL30853,
interagency guidance document known as the FLAG
Report, “Although the FLMs have an ‘
Clean Air Act: A Summary of the Act and Its Major
affirmative
Requirements, by James E. McCarthy and Claudia
responsibility’ to protect AQRVs [air quality-related
Copeland.
values], they have no permitting authority under the CAA,
and they have no authority under the CAA to establish air
quality-related rules or standards. The FLM role within the
James E. McCarthy, Specialist in Environmental Policy
regulatory context consists of considering whether
Laura B. Comay, Analyst in Natural Resources Policy
emissions from a new source, or emission increases from a
IF10496
modified source, may have an adverse impact on AQRVs
and providing comments to permitting authorities (States or
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Protecting Clean Air in National Parks and Wilderness Areas
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