2 Federal Register / Vol. 62, No. 138 / Friday, July 18, 1997 / Prepublication

ENVIRONMENTAL PROTECTION

AGENCY

40 CFR Part 50

[ADA–95–58; FRL–5725–3]

RIN–2060–AE57

National Ambient Air Quality

Standards for Ozone

AGENCY: Environmental Protection Agency

(EPA).

ACTION: Final rule.

SUMMARY: This document describes EPA’s

decision to revise the national ambient air

quality standards (NAAQS) for ozone (O3)

based on its review of the available scientific

evidence linking exposures to ambient O3 to

adverse health and welfare effects at levels

allowed by the current O3 standards. The

current 1–hour primary standard is replaced

by an 8–hour standard at a level of 0.08 parts

per million (ppm) with a form based on the

3–year average of the annual fourth-highest

daily maximum 8–hour average O3

concentrations measured at each monitor

within an area. The new primary standard will

provide increased protection to the public,

especially children and other at-risk

populations, against a wide range of O3-

induced health effects, including decreased

lung function, primarily in children active

outdoors; increased respiratory symptoms,

particularly in highly sensitive individuals;

hospital admissions and emergency room

visits for respiratory causes, among children

and adults with pre-existing respiratory

disease such as asthma; inflammation of the

lung, and possible long-term damage to the

lungs. The current 1–hour secondary standard

is replaced by an 8–hour standard identical to

the new primary standard. The new secondary

standard will provide increased protection to

the public welfare against O3-induced effects

on vegetation, such as agricultural crop loss,

damage to forests and ecosystems, and visible

foliar injury to sensitive species.

EFFECTIVE DATE: This rule is effective

September 16, 1997.

ADDRESSES: A docket containing

information relating to the EPA’s review of

the O3 primary and secondary standards

(Docket No. A–95–58) is available for public

inspection in the Central Docket Section of

the U.S. Environmental Protection Agency,

South Conference Center, Room 4, 401 M

St., SW., Washington, DC. This docket

incorporates the docket from the previous

review of the O3 standards (Docket No. A–

92–17) and the docket established for the air

quality criteria document (Docket No.

ECAO–CD–92–0786). The docket may be

inspected between 8 a.m. and 3 p.m. on

weekdays, and a reasonable fee may be

charged for copying. The information in the

docket constitutes the complete basis for the

decision announced in this final rule. For the

availability of related information, see

‘‘SUPPLEMENTARY INFORMATION.’’

FOR FURTHER INFORMATION CONTACT:

David McKee, MD–15, Air Quality Standards

and Strategies Division, Office of Air Quality

Planning and Standards, U.S. Environmental

Protection Agency, Research Triangle Park,

NC 27711; telephone: (919) 541–5288; email: mckee.dave@epamail.epa.gov.

SUPPLEMENTARY INFORMATION:

Availability of Related Information

Certain documents are available from the

U.S. Department of Commerce, National

Technical Information Service, 5285 Port

Royal Road, Springfield, VA 22161.

Available documents include:

(1) Air Quality Criteria for O3 and Other

Photochemical Oxidants (‘‘Criteria

Document’’) (three volumes, EPA/600/P–93–

004aF through EPA/600/P–93–004cF, July

1996, NTIS # PB–96–185574, $169.50 paper

copy, $58.00 microfiche).

(2) The Review of the National Ambient

Air Quality Standards for O3: Assessment of

Scientific and Technical Information (‘‘Staff

Paper’’)(EPA–452/R–96–007, June 1996,

NTIS # PB–96–203435, $67.00 paper copy

and $21.50 microfiche). (Add a $3.00

handling charge per order.)

A limited number of copies of other

documents generated in connection with this

standard review, such as documents

pertaining to human exposure and health risk

assessments, and vegetation exposure, risk,

and benefits analyses can be obtained from:

U.S. Environmental Protection Agency

Library (MD–35), Research Triangle Park,

NC 27711, telephone (919) 541–2777. These

and other related documents are also available

for inspection and copying in the EPA docket

identified under ‘‘ADDRESSES’’.

Electronic Availability

The Staff Paper and human exposure and

health risk assessment support documents are

now available on the Agency’s Office of Air

Quality Planning and Standards (OAQPS)

Technology Transfer Network (TTN) Bulletin

Board System (BBS) in the Clean Air Act

Amendments area, under Title I, Policy/

Guidance Documents. To access the bulletin

board, a modem and communications

software are necessary. To dial up, set your

communications software to 8 data bits, no

parity and one stop bit. Dial (919) 541–5742

and follow the on-screen instructions to

register for access. After registering, proceed

to choice ‘‘<T> Gateway to TTN Technical

Areas’’, then choose ‘‘<E> CAAA BBS’’.

From the main menu, choose ‘‘<1> Title I:

Attain/Maint of NAAQS’’, then ‘‘<P> Policy

Guidance Documents.’’ To access these

documents through the World Wide Web,

click on ‘‘TTN BBSWeb’’, then proceed to

the Gateway to TTN Technical areas, as

above. If assistance is needed in accessing the

system, call the help desk at (919) 541–5384

in Research Triangle Park, NC.

Implementation Strategy for Revised Air

Quality Standards

On Wednesday, July 16, 1997, President

Clinton signed a memorandum to the

Administrator specifying his goals for the

implementation of the O3 and PM standards.

Attached to the President’s memorandum is

a strategy prepared by an interagency

Administration group outlining the next steps

that would be necessary for implementing

these standards. The EPA will prepare

guidance and proposed rules consistent with

the President’s memorandum. Copies of the

Presidential document are available in paper

copy by contacting the U.S. Environmental

Protection Agency Library at the address

under ‘‘Availability of Related Information’’

and in electronic form as discussed above in

‘‘Electronic Availability.’’

The following topics are discussed in this

preamble:

I. Background

A. Legislative Requirements

B. Related Control Requirements

C. Review of Air Quality Criteria and Standards

for O3

D. Summary of Proposed Revisions to the O3

Standards

II. Rationale for the Primary O3 Standard

A. Introduction

B. Elements of the Primary Standard

C. Communication of Public Health Information

III. Rationale for the Secondary O3 Standard

A. Introduction

B. Need for Revision of Current Secondary

Standard

C. Final Decision on the Secondary Standard

IV. Other Issues

A. Cost Considerations

B. Margin of Safety

C. Comment Period

D. 1990 Act Amendments

V. Technical Changes to Part 50

VI. Revisions to Appendices D, E, and H

VII. Regulatory and Environmental Impact

Analyses

A. Executive Order 12866

B. Regulatory Flexibility Analysis

C. Impact of Reporting Requirements

D. Unfunded Mandates Reform Act

E. Environmental Justice

F. Submission to Congress and Comptroller

General

VIII. Response to Petition for Administrator

Browner’s Recusal

IX. References

I. Background

A. Legislative Requirements

Two sections of the Act govern the

establishment, review, and revision of

NAAQS. Section 108 (42 U.S.C. 7408)

directs the Administrator to identify certain

pollutants which ‘‘may reasonably be

anticipated to endanger public health or

welfare’’ and to issue air quality criteria for

them. These air quality criteria are to

‘‘accurately 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
Federal Register / Vol. 62, No. 138 / Friday, July 18, 1997 / Prepublication 3

1 A more complete history of the O3 NAAQS is

presented in section II.B. of the Office of Air Quality

Planning and Standards Staff Paper, Review of National

Ambient Air Quality Standards for O3: Assessment of

Scientific and Technical Information (U.S. EPA, 1996b).

2 The Staff Paper evaluates policy implications of the

key studies and scientific information in the Criteria

Document, identifies critical elements that EPA staff

believes should be considered, and presents staff

conclusions and recommendations of suggested options for

the Administrator’s consideration.

from the presence of [a] pollutant in the

ambient air ***.’’

Section 109 (42 U.S.C. 7409) directs the

Administrator to propose and promulgate

‘‘primary’’ and ‘‘secondary’’ NAAQS for

pollutants identified under section 108.

Section 109(b)(1) defines a primary standard

as one ‘‘the attainment and maintenance of

which in the judgment of the Administrator,

based on [the] criteria and allowing an

adequate margin of safety, are requisite to

protect the public health.’’ The margin of

safety requirement was intended to address

uncertainties associated with inconclusive

scientific and technical information available

at the time of standard setting, as well as to

provide a reasonable degree of protection

against hazards that research has not yet

identified. Both kinds of uncertainties are

components of the risk associated with

pollution at levels below those at which

human health effects can be said to occur

with reasonable scientific certainty. Thus, by

selecting primary standards that provide an

adequate margin of safety, the Administrator

is seeking not only to prevent pollution levels

that have been demonstrated to be harmful

but also to prevent lower pollutant levels that

she finds may pose an unacceptable risk of

harm, even if the risk is not precisely

identified as to nature or degree. The Act

does not require the Administrator to

establish a primary NAAQS at a zero-risk

level but rather at a level that reduces risk

sufficiently so as to protect public health with

an adequate margin of safety. The selection

of any particular approach to providing an

adequate margin of safety is a policy choice

left specifically to the Administrator’s

judgment. Lead Industries Association v.

EPA. (647 F.2d 1130, 1161–62 (D.C. Cir.

1980)).

A secondary standard, as defined in section

109(b)(2), must ‘‘specify a level of air quality

the attainment and maintenance of which in

the judgment of the Administrator, based on

[the] criteria, [are] requisite to protect the

public welfare from any known or anticipated

adverse effects associated with the presence

of [the] pollutant in the ambient air.’’ Welfare

effects as defined in section 302(h) (42

U.S.C. 7602(h)) include, but are not limited

to, ‘‘effects on soils, water, crops, vegetation,

manmade materials, animals, wildlife,

weather, visibility, and climate, damage to

and deterioration of property, and hazards to

transportation, as well as effects on economic

values and on personal comfort and wellbeing.’’

Section 109(d)(1) of the Act requires

periodic review and, if appropriate, revision

of existing air quality criteria and NAAQS.

Section 109(d)(2) requires appointment of an

independent scientific review committee to

review criteria and standards and recommend

new standards or revisions of existing criteria

and standards, as appropriate. The committee

established under section 109(d)(2) is known

as the Clean Air Scientific Advisory

Committee (CASAC), a standing committee

of EPA’s Science Advisory Board.

B. Related Control Requirements

States are primarily responsible for

ensuring attainment and maintenance of

ambient air quality standards once EPA has

established them. Under section 110 of the

Act (42 U.S.C. 7410) and related provisions,

States are to submit, for EPA approval, State

implementation plans (SIP’s) that provide for

the attainment and maintenance of such

standards through control programs directed

to sources of the pollutants involved. The

States, in conjunction with EPA, also

administer the prevention of significant

deterioration programs (42 U.S.C. 7470–

7479) for these pollutants. In addition,

Federal programs provide for nationwide

reductions in emissions of these and other air

pollutants under Title II of the Act (42 U.S.C.

7521–7574), which involves controls for

automobile, truck, bus, motorcycle, nonroad

engine, and aircraft emissions; the new source

performance standards under section 111 (42

U.S.C. 7411); and the national emission

standards for hazardous air pollutants under

section 112 (42 U.S.C. 7412).

C. Review of Air Quality Criteria and

Standards for O3

The last review of O3 air quality criteria

and standards was completed in March 1993

with notice of a final decision not to revise

the existing primary and secondary standards

(58 FR 13008). The current primary and

secondary standards are each set at a level of

0.12 ppm, with a 1–hour averaging time and

a 1-expected-exceedance form, such that the

standards are attained when the expected

number of days per calendar year with

maximum hourly average concentrations

above 0.12 ppm is equal to or less than 1,

averaged over 3 years (as determined by 40

CFR part 50, Appendix H).1

The EPA initiated this current review of

the air quality criteria and standards in

August 1992 with the development of a

revised Air Quality Criteria Document for O3

and Other Photochemical Oxidants,

henceforth the ‘‘Criteria Document.’’ Several

workshops were held by EPA’s National

Center for Environmental Assessment

(NCEA) to discuss health and welfare effects

information during the summer and fall of

1993. An external review draft of the Criteria

Document made available to the public and

to the CASAC in the spring of 1994 was

reviewed at a public CASAC meeting held on

July 20–21, 1994. Based on comments made

at the meeting, NCEA staff prepared a second

external review draft, which was reviewed at

a public CASAC meeting on March 21–22,

1995. At the same meeting, the CASAC also

reviewed draft portions of a staff paper

prepared by the OAQPS, Review of National

Ambient Air Quality Standards for O3:

Assessment of Scientific and Technical

Information (henceforth, the ‘‘Staff Paper’’),

focusing on health effects and the primary

NAAQS.2 Taking into account CASAC and

public comments, staff revised both

documents and made new drafts available for

public and CASAC review during the

summer of 1995. The OAQPS staff also

prepared and made available draft portions of

the Staff Paper focusing on welfare effects

and the secondary standard.

A public CASAC meeting was held on

September 19–20, 1995, at which time

CASAC came to closure in its review of the

draft Criteria Document and the primary

standard sections of the draft Staff Paper. In

a November 28, 1995 letter from the CASAC

chair to the Administrator, CASAC advised

that the final draft Criteria Document

‘‘provides an adequate review of the available

scientific data and relevant studies of O3 and

related photochemical oxidants’’ (Wolff,

1995a). Further, in a November 30, 1995

letter, CASAC advised the Administrator that

the primary standard portion of the draft Staff

Paper ‘‘provides an adequate scientific basis

for making regulatory decisions concerning a

primary O3 standard’’ (Wolff, 1995b). The

final Criteria Document (U.S. EPA, 1996a)

reflects CASAC and public comments

received at and subsequent to the September

1995 CASAC meeting.

Based on comments on the Staff Paper

from the September 1995 CASAC meeting,

revisions were made to the secondary

standard sections of the Staff Paper, which

were reviewed at a public CASAC meeting

held on March 21, 1996. At that meeting and

in a subsequent letter to the Administrator,

CASAC concluded that the secondary

standard sections of the draft Staff Paper

‘‘provide an appropriate scientific basis for

making regulatory decisions concerning a

secondary O3 standard’’ (Wolff, 1996). The

final Staff Paper (U.S. EPA, 1996b) reflects

CASAC and public comments received at and

subsequent to the September 1995 and March

1996 meetings on the primary standard and

secondary standard sections, respectively.

On November 27, 1996 EPA announced its

proposed decision to revise the NAAQS for

O3 (61 FR 65716, December 13, 1996,

hereinafter ‘‘proposal’’) as well as its

proposed decision to revise the NAAQS for

particulate matter (PM). In the proposal, EPA

identified proposed revisions, based on the air

quality criteria for O3, and solicited public

comments on alternative primary and

secondary standards and on the proposed

forms of the standards.
4 Federal Register / Vol. 62, No. 138 / Friday, July 18, 1997 / Prepublication

To ensure the broadest possible public

input on the O3 and PM proposals, EPA took

extensive and unprecedented steps to

facilitate the public comment process beyond

the normal process of providing an

opportunity to request a hearing and receiving

written comments submitted to the

rulemaking docket. The EPA established a

national toll-free telephone hotline to

facilitate public comments on the proposed

revisions to the O3 and PM NAAQS, and on

related notices dealing with the

implementation of revised O3 and PM

standards, as well as a system for the public

to submit comments on the proposals

electronically via the Internet. Over 14,000

calls and over 4,000 electronic mail messages

were received through these channels. The

public could also access key supporting

documents (including the Criteria Document,

Staff Paper, related technical documents and

fact sheets) via the Internet.

The EPA also held several public hearings

and meetings across the country to provide

direct opportunities for public comment on

the proposed revisions to the O3 and PM

NAAQS and to disseminate information to

the public about the proposed standard

revisions. On January 14 and 15, 1997, EPA

held concurrent, 2–day public hearings in

Boston, MA, Chicago, IL, and Salt Lake City,

UT. A fourth public hearing, which focused

primarily on PM monitoring issues, was held

in Durham, NC on January 14, 1997. Over

400 citizens and organizations testified during

these public hearings. EPA also held two

national satellite telecasts to answer questions

on the standards and participated in meetings

sponsored by the Air and Waste Management

Association on the proposed revisions to the

standards at more than 10 locations across the

country. Beyond that, several EPA regional

offices held public meetings and workshops

and participated in hearings that States and

cities held around the country.

As a result of this intensive effort to solicit

public input, over 50,000 written and verbal

comments were received on the proposed

revisions to the O3 NAAQS by the close of

the public comment period on March 12,

1997. The major issues raised in the

comments are discussed throughout the

preamble of this final rule. A comprehensive

summary of all significant comments, along

with EPA’s response to such comments

(hereafter ‘‘Response to Comments’’), can be

found in the docket for this rulemaking

(Docket No. A–95–58).

The focus of this current review of the air

quality criteria and standards for O3 and

related photochemical oxidants is on public

health and welfare effects associated with

exposure to ambient levels of tropospheric

O3. Tropospheric O3 is chemically identical

to stratospheric O3, which is produced miles

above the earth’s surface and provides a

protective shield from excess ultraviolet

radiation. In contrast, tropospheric O3 at

sufficient concentrations has been associated

with harmful effects due to its oxidative

properties and its presence in the air that

people and plants take up during respiratory

processes. Ozone is not emitted directly from

mobile or stationary sources but, like other

photochemical oxidants, commonly exists in

the ambient air as an atmospheric

transformation product. Ozone formation is

the result of chemical reactions of volatile

organic compounds (VOC), nitrogen oxides

(NOx), and oxygen in the presence of sunlight

and generally at elevated temperatures. A

detailed discussion of atmospheric formation,

ambient concentrations, and health and

welfare effects associated with exposure to

O3 can be found in the Criteria Document and

in the Staff Paper.

D. Summary of Proposed Revisions to the O3

Standards

For reasons discussed in the proposal, the

Administrator proposed to replace the current

1–hour primary standard for O3 with an 8–

hour standard set at 0.08 ppm, which would

be met at an ambient air quality monitoring

site when the 3–year average of the annual

third-highest daily maximum 8–hour average

O3 concentration is less than or equal to 0.08

ppm. The proposal solicited comments on

alternative 8–hour standards set at 0.09 ppm,

which generally represents the continuation of

the present level of protection, and 0.07 ppm,

which would be highly precautionary in

nature, as well as on retaining the current

primary standard. The proposal also solicited

comments on alternative forms of the

standard, specific data handling and rounding

conventions used in determining attainment

with the standard, and issues related to the

communication of public health information.

With regard to the secondary standard, the

Administrator proposed to replace the current

1–hour secondary standard with one of two

alternative standards: either one set identical

to the proposed primary standard or a new

seasonal standard expressed as a sum of

hourly O3 concentrations greater than or

equal to 0.06 ppm, cumulated over 12 hours

per day during the consecutive 3–month

period of maximum concentrations during the

O3 monitoring season, set at a level of 25

ppm-hour. The proposal solicited comments

on these two alternatives, as well as on

specific issues related to the form of a

seasonal standard and on an enhanced rural

air quality monitoring network.

II. Rationale for the Primary Standard

A. Introduction

1. Overview . This notice presents the

Administrator’s final decision regarding the

need to revise the current primary O3

standard, and, more specifically, regarding the

averaging time, level, and form of a new

primary standard to replace the current 1–

hour standard. This decision is based on a

thorough review, in the Criteria Document, of

the scientific information on human health

effects associated with exposure to ambient

levels of O3, including evaluation of key

studies published through 1995. This decision

also takes into account:

(1) Staff Paper assessments of the most

policy-relevant information in the Criteria

Document and analyses of human exposure

and risk, presented in the Staff Paper and

supporting technical reports.

(2) CASAC advice and recommendations,

as reflected in discussions of drafts of the

Criteria Document and Staff Paper at public

meetings, in separate written comments, and

in CASAC’s letters to the Administrator.

(3) Public comments received during the

development of these documents, either in

connection with CASAC meetings or

separately.

(4) Extensive public comments received on

the proposal regarding the primary O3

standard.

After taking this information and

comments into account and for the reasons

discussed below in this unit, the

Administrator concludes that revisions to the

current primary standard to provide increased

public health protection are appropriate at this

time to protect public health with an adequate

margin of safety. Further, the Administrator

determines that it is appropriate to establish

a revised 8–hour, 0.08 ppm primary standard

with a form based on the 3–year average of

the annual fourth-highest daily maximum 8–

hour average O3 concentrations measured at

each monitor within an area.

As discussed more fully below in this unit,

the rationale for the final decision regarding

the O3 primary NAAQS includes

consideration of:

(1) Health effects information to inform

judgments as to the likelihood that exposures

to ambient O3 result in adverse health effects

for exposed individuals.

(2) Insights gained from human exposure

and risk assessments to provide a broader

perspective for judgments about protecting

public health from the risks associated with

O3 exposure.

(3) Specific conclusions with regard to the

elements of a standard (i.e., averaging time,

level, and form) that, taken together, would

be appropriate to protect public health with

an adequate margin of safety.

(4) Alternative views of the significance of

the effects and factors to be considered in

policy judgments about the appropriate

elements of the standard.

The health effects information and human

exposure and risk assessments were

summarized in the proposal and are only

briefly outlined below. More fully discussed

in the following units of this preamble is the

Administrator’s rationale, in light of key

issues raised in public comments, for

concluding that it is appropriate to revise the

specific elements of the current standard

including averaging time (Unit II.B.1.), level

(Unit II.B.2.), and form (Unit II.B.3.). Finally,

the related subject of the communication of
Federal Register / Vol. 62, No. 138 / Friday, July 18, 1997 / Prepublication 5

3 ‘‘Acute health effects’’ of O3 are defined as those

effects induced by short-term and prolonged exposures to

O3. Examples of these effects are functional, symptomatic,

biochemical, and physiologic changes.

4 ‘‘Chronic health effects’’ of O3 are defined as those

effects induced by long-term exposures to O2. Examples

of these effects are structural damage to lung tissue and

accelerated decline in baseline lung function.

5 ‘‘Exposures of concern’’ refer throughout to exposures

at and above 0.08 ppm, 8–hour average, at which a range

of health effects have been observed in controlled human

studies, but for which data were too limited to allow for

quantitative risk assessment.

public health information, and the public

comments received on this subject, are

summarized in Unit II.C.

2. Health effects information. The last

review of the air quality criteria for O3

included an evaluation of key studies

published through early 1989 and was the

basis for EPA’s 1993 decision not to revise

the primary standard at that time. However,

in recognition of the large number of new

studies, particularly on 6– to 8–hour

exposures to O3, that had become available

since early 1989 but had not undergone

rigorous assessment and review by CASAC,

the EPA made clear in the 1993 final decision

notice that it would proceed with the next

review as rapidly as possible to consider this

new information. Thus, the current review of

health effects information focused on a large

body of information published since 1989 that

would lead to a more informed decision than

was possible in 1993 as to whether an O3

primary standard with a longer averaging

time was appropriate to protect public health.

The proposal reviewed the human health

effects associated with exposure to ambient

levels of O3 based on an integrative

assessment of human clinical,

epidemiological, and animal toxicological

studies available through 1995, as assessed in

the Criteria Document and Staff Paper. Based

on this information, an array of health effects

has been attributed to short-term (1 to 3

hours), prolonged (6 to 8 hours), and longterm (months to years) exposures to O3.

Acute health effects3 are induced by shortterm exposures to O3 (observed at

concentrations as low as 0.12 ppm), generally

while individuals are engaged in moderate or

heavy exertion, and by prolonged exposures

to O3 (observed at concentrations as low as

0.08 ppm), typically while individuals are

engaged in moderate exertion. Moderate

exertion levels are more frequently

experienced by individuals than heavy

exertion levels. The acute health effects

include transient pulmonary function

responses, transient respiratory symptoms,

effects on exercise performance, increased

airway responsiveness, increased

susceptibility to respiratory infection,

increased hospital admissions and emergency

room visits, and transient pulmonary

inflammation. Based in particular on new

information available since the last review of

the air quality criteria for O3 was completed,

such acute health effects have been observed

following prolonged exposures at moderate

levels of exertion at concentrations of O3 as

low as 0.08 ppm. Groups at increased risk of

experiencing such effects include active

children and outdoor workers who regularly

engage in outdoor activities and individuals

with preexisting respiratory disease (e.g.,

asthma, chronic obstructive lung disease).

Further, it is recognized that some individuals

are unusually responsive to O3 and may

experience much greater functional and

symptomatic effects from exposure to O3 than

the average individual.

With regard to chronic health effects4, the

collective data from studies of laboratory

animals and human populations have many

ambiguities, but provide suggestive evidence

of such effects in humans. It is clear from

toxicological data that O3-induced lung injury

is roughly similar across species (including

monkeys, rats, and mice) with responses that

are concentration dependent. The currently

available information provides at least a

biologically plausible basis for considering

the possibility that repeated inflammation

associated with exposure to O3 over a lifetime

may result in sufficient damage to respiratory

tissue such that individuals later in life may

experience a reduced quality of life, although

such relationships remain highly uncertain.

EPA’s consideration of this health effects

information necessarily included judgments

with respect to when these physiological

effects become so significant that they should

be regarded as adverse to the health of

individuals experiencing the effects. In

making these judgments, the Administrator

looked to guidelines published by the

American Thoracic Society (1985) and the

advice of CASAC. The proposal summarized

the criteria and reasoning for EPA’s

judgments on this issue, upon which the

CASAC panel expressed a consensus view

that these ‘‘criteria for the determination of

an adverse physiological response was

reasonable’’ (Wolff, 1995b). The criteria take

into account the degree of severity of the

effects; the likelihood that the effects would

interfere with normal activity for individuals

with impaired respiratory systems or active

healthy individuals; the likelihood that the

effects would result in additional or more

frequent use of medication, medical

treatment, or emergency room visits for

individuals with impaired respiratory systems;

and the implications of single or repeated

occurrences of the effects for an individual.

Some commenters raised concerns

regarding the criteria used by EPA to make

determinations as to when effects become

adverse, citing CASAC’s closure letter

(Wolff, 1995b) stating that ‘‘there was

considerable concern that the criteria for

grading physiological and clinical responses

to O3 was confusing if not misleading.’’

These concerns with the draft criteria were

discussed at length during a public CASAC

meeting, resulting in very specific agreements

as to how to revise the draft criteria so as to

be consistent with CASAC’s advice

(Transcript of CASAC meeting, September

19–20, 1995, pp. 242–248). Having reached

such specific agreement, CASAC advised that

further review of the final version of these

criteria, subsequently incorporated in both the

final Criteria Document and Staff Paper, was

unnecessary.

Other commenters have questioned

whether judgments made in this review are

consistent with those made in the last review

with regard to when physiological and

clinical effects become adverse to individuals

experiencing such effects. Specifically, the

commenters focused on the judgment stated

in the 1993 final decision notice (58 FR

13008, March 9, 1993) that ‘‘lesser effects

associated with [1– to 3–hour] exposure to O3

in the range of 0.12 ppm to 0.15 ppm

observed in the controlled human studies did

not constitute adverse effects for purposes of

section 109 of the Act.’’ The ‘‘lesser effects’’

referred to in that notice involved responses

of a maximum decrease in lung function [as

measured by forced expiratory volume in 1

second (FEV1)] of from 9 percent to 16

percent for the most sensitive individuals

exposed in this range, with few, if any,

symptoms. The EPA notes that this judgment

is, in fact, consistent with judgments

presented in the 1996 proposal, which

identify moderate and large lung function

decrements (as reflected in EPA’s risk

assessment by FEV1 decreases of ≥ 15

percent and ≥ 20 percent, respectively, with

the most sensitive individuals experiencing

FEV1 decreases as large as 40 percent to 50

percent at 6– to 8–hour exposures in the

range of 0.08 ppm to 0.10 ppm in controlled

human studies), and moderate to severe

symptoms as being adverse.

3. Exposure and risk assessments. To put

judgments about health effects that are

adverse for individuals into a broader public

health context, EPA conducted quantitative

assessments to estimate O3 exposures and

related risks for the general population and

two at-risk groups, ‘‘outdoor children’’ and

‘‘outdoor workers,’’ living in nine

representative U.S. urban areas. This broader

context included consideration, to the extent

possible, of the size of the particular

population groups identified as at risk for

various effects, the estimated number of

people within at-risk groups likely to

experience O3-related adverse effects, the

estimated number of occurrences of such

effects, and the estimated number of people

who would experience exposures of concern5

associated with various air quality scenarios

representing attainment of the current and

alternative 8–hour standards. Consideration

was also given to the kind and degree of

uncertainties inherent in assessing such

exposures and risks. Such considerations

provided a basis for judgments discussed in
6 Federal Register / Vol. 62, No. 138 / Friday, July 18, 1997 / Prepublication

6 This study is one of several studies, mainly conducted

in the northeastern portion of the United States and

southeastern Canada, reporting excess daily respiratoryrelated hospital admissions associated with elevated O3

levels within the general population and, more specifically,

for individuals with asthma.

7 The analyses were conducted for the at-risk population

of outdoor children, the group with the highest exposures

and risks. Outdoor children are the subset of children

between the ages of 6 and 18 years old who tend to be

active outdoors, and include approximately over 30 percent

to 45 percent of all children in this age group in the nine

urban areas analyzed.

8 These changes primarily focused on the air quality

data used in the exposure analysis and on the air quality

adjustment procedures used to simulate ambient O3

concentrations upon attainment of alternative standards.

9 This review focused only on a standard for O3, as the

most appropriate surrogate for photochemical oxidants.

the proposal about the levels of exposure and

risk associated with the current and

alternative standards, which helped inform

judgments about the adequacy of public

health protection afforded by the current and

alternative standards.

Risk estimates were developed for those

effects for which sufficient concentrationresponse information was available from

studies evaluated in the Criteria Document,

including adverse lung function and

respiratory symptom responses. In a separate

analysis, excess respiratory hospital

admissions for individuals with asthma

associated with attainment of alternative

standards were also estimated, using a risk

model for this health endpoint based on the

results of an epidemiological study in New

York City (Thurston et al., 1992) for which

adequate air quality information was available

to assess population risk6. These quantitative

risk estimates (for that subset of O3-related

effects for which information is sufficient to

conduct such quantitative analyses) add to our

understanding of the broader array of health

effects that are associated with exposure to

O3 but for which quantitative risk estimates

could not be developed.

The methodology, results, and key

observations from these assessments were

presented in the proposal. The EPA believes,

and CASAC concurred, that the models

selected to estimate exposure and risk were

appropriate and that the methods used to

conduct the health risk assessment for adverse

lung function and respiratory symptom

responses represent the state of the art.

Nevertheless, the Administrator and CASAC

recognized that there are many uncertainties

inherent in such analyses, and that not all

uncertainties inherent in such analyses could

be quantified and reflected in ranges of risk

estimates (Wolff, 1995b), as discussed in the

proposal and the referenced technical support

documents.

The exposure and risk assessments

available at the time of proposal had been

conducted to evaluate the O3 exposures and

risks associated with attainment of the current

1–hour standard and various alternative 8–

hour standards under consideration early in

the standards review process when the

assessments were initiated. The EPA and

CASAC recognized at that time that

additional alternative standards might need to

be analyzed later in the review process. Upon

deciding to propose a standard with a

concentration-based form in the Fall of 1996,

EPA staff initiated supplemental analyses to

estimate exposures and risks7 for the specific

standard to be proposed and alternative

standards on which the proposal solicited

comment. In conducting these supplemental

analyses, several technical changes were

made based on insights gained from the initial

analyses.8 The supplemental assessment

(Richmond, 1997) was placed in the docket

and on the TTN on February 12, 1997, and

its availability was announced in the Federal

Register notice extending the public

comment period on the proposal, providing

the public the opportunity to comment on the

supplemental assessment (61 FR 7743,

February 20, 1997).

Key observations and results from the

initial and supplemental exposure and risk

assessments that are most pertinent to the

decision to revise the current primary

standard are highlighted in the following unit,

together with discussion of the key issues

raised in public comments on the

methodology and public health implications

of these assessments.

B. Elements of the Primary Standard

In selecting a primary standard for O3, the

Administrator must specify: Averaging time,

O3 concentration (i.e., level), and form (i.e.,

the air quality statistic to be used as a basis

for determining compliance with the

standard).9 All three of these elements are

necessary to define a standard and to

determine the degree of public health

protection afforded by the standard. The

proposal outlined the key factors considered

in selecting each of these elements for the

proposed standard, as well as the range of

options for each element on which the EPA

solicited comment. The factors reflect an

integration of information on acute and

chronic health effects associated with

exposure to ambient O3; expert judgments on

the adversity of such effects for individuals;

and policy judgments, informed by air quality

and exposure analyses and quantitative risk

assessment when possible, as to the point at

which risks would be reduced sufficiently to

achieve protection of public health with an

adequate margin of safety.

This approach to selecting a primary

standard was endorsed by CASAC (Wolff,

1995b), particularly through its advice to the

Administrator that ‘‘EPA’s risk assessments

must play a central role in identifying an

appropriate level’’ and its recognition that

‘‘the selection of a specific level and [form]

is a policy judgment.’’ Further, it was the

consensus view of CASAC that the ranges of

8–hour average levels (0.07 to 0.09 ppm) and

forms (concentration-based forms that

generally allow for 1 to 5 exceedances) on

which the proposal solicited comment were

appropriate.

The following discussion focuses primarily

on those considerations that were most

influential in the Administrator’s final

decisions on these elements, taking into

account the comments received on the range

of options identified in the proposal.

1. Averaging time. In proposing to change

the averaging time of the primary standard

from 1 to 8 hours, the Administrator was

concurring with the unanimous

recommendation of CASAC (Wolff, 1995b)

‘‘that the present 1–hour standard be

eliminated and replaced with an 8–hour

standard,’’ and that more research is needed

to resolve uncertainties about potential

chronic effects before appropriate

consideration can be given to establishing a

long-term (e.g., seasonal or annual) primary

standard. The Administrator’s proposed

decision was supported by the following key

observations and conclusions:

(1) The 1–hour averaging time specified in

the current NAAQS was originally selected

primarily on the basis of health effects

associated with short-term (i.e., 1– to 3–hour)

exposures, with qualitative consideration

given to preliminary information on potential

associations with longer exposure periods.

(2) Substantial new health effects

information available for consideration in this

review demonstrates associations between a

wide range of health effects and prolonged

(i.e., 6– to 8–hour) exposures below the level

of the current 1–hour NAAQS.

(3) Results from the quantitative risk

analyses show that attaining a standard with

a 1-hour averaging time reduces the risk of

experiencing health effects associated with

both 1–hour and 8–hour exposures. Likewise,

attaining an 8–hour standard reduces the risk

of experiencing health effects associated with

both 8–hour and 1–hour exposures. Thus,

reductions in risks from both short-term and

prolonged exposures can be achieved through

a primary standard with an averaging time of

either 1 or 8 hours. As a result, establishment

of both 1–hour and 8–hour standards would

not be necessary to reduce risks associated

with the full range of observed acute health

effects.

(4) The 8–hour averaging time is more

directly associated with health effects of

concern at lower O3 concentrations than is the

1–hour averaging time. It was thus the

consensus of CASAC ‘‘that an 8–hour

standard was more appropriate for a human

health-based standard than a 1–hour

standard.’’ (Wolff, 1995b)

(5) While there is a large animal toxicology

database providing clear evidence of

associations between long-term (e.g., from

several months to years) exposures and lung

tissue damage, with additional evidence of

reduced lung elasticity and accelerated loss of

lung function, there is no corresponding
Federal Register / Vol. 62, No. 138 / Friday, July 18, 1997 / Prepublication 7

10 More precisely, exposures at and above 0.08 ppm

refers to estimates of exposures to O3 concentrations ≥

0.081 ppm from the exposure assessment.

11 In terms of the percent of outdoor children estimated

to be exposed to O3 concentrations at and above 0.08 ppm

while engaged in moderate exertion, the current 1–hour

standard results in a range across the seven nonattainment

areas of approximately 0.3 percent to 24 percent of such

children, whereas alternative 8–hour standards, at the

proposed level of 0.08 ppm, result in a significantly more

uniform degree of protection, with ranges of approximately

2 percent to 9 percent, third-highest concentration form,

and 3 percent to 11 percent, fifth-highest concentration

form, across the areas.

evidence for humans. Moreover, the state of

the science has not progressed sufficiently to

permit quantitative extrapolation of the

animal-study findings to humans. Thus, the

Administrator concluded that consideration of

a separate long-term primary O3 standard is

not appropriate at this time. As discussed

below, however, the Administrator considered

the possibility of long-term effects in

selecting the level of an 8–hour standard,

which will provide protection against such

effects to the extent they may occur in

humans, by lowering overall air quality

distributions and, thus, reducing cumulative

long-term exposures.

The public comments reflect broad support

for a standard with an 8–hour averaging time,

either alone or in conjunction with a 1–hour

standard. This support was typically based on

references to:

(1) Evidence of health effects from 6– to

8–hour exposures to O3 concentrations down

to 0.08 ppm, which are lower than those

concentrations that have induced such effects

after 1– to 3–hour exposures, and which are

lower than the 0.12 ppm level of the current

standard.

(2) Analyses indicating that an 8–hour

standard would limit both 1– and 8–hour

exposures.

(3) CASAC’s unanimous agreement that

the current 1–hour standard should be

replaced by an 8–hour standard. In

considering the adequacy of the current 1–

hour standard alone in light of the health

effects evidence, some commenters have

highlighted the statement in the Criteria

Document that there is ‘‘strong evidence that

ambient exposures to O3 can cause significant

exacerbations of preexisting respiratory

disease in the general public at concentrations

below 0.12 ppm.’’ (U.S. EPA, 1996a, p. 7–

171)

Commenters expressing support for an 8–

hour averaging time included not only those

who supported a level of public health

protection consistent with or greater than that

reflected by EPA’s proposed standard, but

also many who disagreed for various reasons

with the need for increased public health

protection beyond that provided by the

current standard. Of those supporting an 8–

hour averaging time but not supporting the

need for increased protection, some expressed

the view that the averaging time of a healthbased standard should be consistent with the

exposures of most concern, while others were

simply neutral between the choices of

retaining the current 1–hour standard and

replacing it with an ‘‘equivalent’’ 8–hour

standard.

The EPA agrees with the considerations

raised by those commenters who favor an 8–

hour standard. Further, in considering the

appropriateness of an 8–hour standard as

compared to a 1–hour standard, EPA also

notes the results of its exposure and risk

assessments which show variability across the

nine urban areas analyzed with regard to the

extent to which the current 1–hour standard,

and alternative 8–hour standards, limit 8–hour

exposures of concern and associated risks of

adverse health effects. As noted in the

proposal and in the supplemental risk

assessment, there is much greater variability

across urban areas, particularly in looking at

the seven current nonattainment areas

examined, in the extent to which the current

1–hour standard limits such exposures of

concern and risks than for the alternative 8–

hour standards. For example, the updated

assessment estimates that the current 1–hour

standard results in 8–hour exposures of

concern at and above 0.08 ppm10 that vary

by almost two orders of magnitude across

these areas. In contrast, alternative 8–hour

standards at the proposed level of 0.08 ppm

result in estimated 8–hour exposures of

concern and risks that are much more

consistent.11 In EPA’s view, the fact that an

averaging time of 8 hours results in a

significantly more uniformly protective

national standard than the current 1–hour

standard is an important public health policy

consideration that supports the selection of an

8–hour averaging time.

Those commenters who did not support

EPA’s proposal for an 8–hour averaging time

generally did not support any revision to the

current standard. These commenters

predominantly focused on two basic points:

The generally improving trends in air quality

under the current standard and associated air

quality management programs, which,

commenters argued, suggest that there is no

need for EPA to adopt any more stringent

standard; and observations made in CASAC’s

closure letter (Wolff, 1995b) with regard to

EPA’s risk assessment not demonstrating any

‘‘bright line’’ threshold of effects or

acceptable risk. With regard to the first issue,

EPA agrees that air quality trends are

improving as a consequence of ongoing

control programs designed to attain the

current NAAQS. The EPA does not, however,

believe that these trends relieve the Agency

of its statutory mandate to review and, if

appropriate, revise the NAAQS on the basis

of the best available scientific evidence to

establish standards that protect public health

with an adequate margin of safety. The fact

that current control programs are resulting in

progress toward improving air quality does

suggest that it is important to ensure that such

progress is maintained during any transition

to a revised standard.

With regard to the second issue,

commenters very frequently quoted from the

CASAC closure letter (Wolff, 1995b) stating

‘‘that there is no bright line’ which

distinguishes any of the proposed standards

(either the level or the number of allowable

exceedances) as being significantly more

protective of public health’’ and that ‘‘the

selection of a specific level and number of

allowable exceedances is a policy judgment.’’

These commenters have variously interpreted

these statements as a CASAC consensus that

the differences in the public health protection

afforded by any of the alternative standards

were too small to be important from a public

health perspective, not statistically

significantly different, or simply not different

at all. Based on these interpretations, the

commenters argued that it is not appropriate

to revise the standard in any way, because a

revised standard would result in disruption to

ongoing programs, additional planning

requirements, and increased implementation

costs, but would provide no or only very little

improvement in public health protection.

The EPA believes that these commenters

have misconstrued or too narrowly interpreted

CASAC’s advice to the Administrator by not

considering the entire range of views and

recommendations included in its closure

letter. Specifically, CASAC began its

summary of recommendations to the

Administrator (Wolff, 1995b) by stating that

‘‘[t]he Panel was in unanimous agreement

that the present 1–hour standard be eliminated

and replaced with an 8–hour standard.’’ This

agreement was based on ‘‘the consensus of

the Panel that an 8–hour standard was more

appropriate for a human health-based

standard than a 1–hour standard.’’ Thus,

CASAC was unequivocal in its advice to the

Administrator with regard to which averaging

time the health effects evidence more strongly

supports. While some commenters have also

quoted statements by individual Panel

members at CASAC meetings suggesting that

choosing between a 1– or 8–hour averaging

time is a ‘‘policy’’ choice, these individual

statements during the course of CASAC’s

review do not contradict nor supersede the

clear and unanimous agreement of CASAC

on averaging time as conveyed to the

Administrator in its closure letter.

In considering these comments, EPA also

believes it is important to put into a public

health perspective CASAC’s observations

about the differences among alternative

standards in protecting the public from the

health effects that were quantitatively

estimated in EPA’s risk assessment. In the

closure letter (Wolff, 1995b), CASAC

observed that ‘‘the differences in the percent

of outdoor children *** responding between

the present standard and the most stringent

proposal *** are small and their ranges

overlap for all health endpoints.’’ Most

importantly, EPA notes that the primary
8 Federal Register / Vol. 62, No. 138 / Friday, July 18, 1997 / Prepublication

12 The EPA recognizes this possibility exists especially

in the very few areas with unusually ‘‘peaky’’ air quality

patterns (i.e., in which the ratio of the 1– and 8–hour

average design values for the current and proposed

standards is greater than 1.5).

standard would provide protection from a

broader array of health effects than it was

possible to consider in its quantitative risk

assessment. This perspective is clearly shared

in particular by those CASAC panel members

who personally favored a level or range of

levels that included the proposed level of 0.08

ppm, in that the closure letter characterizes

their views as reflecting, in part, their

‘‘concern over the evidence for chronic deep

lung inflammation from the controlled human

and animal exposure studies.’’ While the risk

of this effect, as well as other effects related

to 6– to 8–hour exposures in the Criteria

Document and Staff Paper (including

increased airway responsiveness, impairment

of host defenses suggesting an increased

susceptibility to respiratory infection, and

increased emergency room visits, doctor

visits, and frequency of medication use by

individuals with impaired respiratory

systems) could not be quantitatively estimated

in EPA’s risk assessment, EPA believes that

consideration of these effects is nevertheless

important in making public health policy

judgments.

Further, in interpreting CASAC’s

statements on EPA’s risk assessment report

(Whitfield et al., 1996) that there is no

‘‘bright line’’ which distinguishes any of the

standards as being ‘‘significantly’’ more

protective, and that the ‘‘ranges overlap,’’

EPA notes that there are statistically

significant differences in the estimated risks

for the standards analyzed with 1- and 5-

exceedance forms. This information was

presented to CASAC at its September 1995

meeting (CASAC meeting transcript,

September 19–20, 1995, pp. 108–109).

Further, EPA again notes that whether one

judges the differences to be significant or

small can depend on whether one focuses on

percentages, as CASAC’s letter did, or on

total numbers of times that children or other

at-risk individuals experience such effects.

The overlap in the ranges of risk referred to

in the CASAC letter reflect differences

among urban areas used in EPA’s risk

analysis (e.g., air quality, exposure patterns,

environmental factors), not random

uncertainties in risk estimates within any

given urban area. Thus, the fact that the

ranges overlap does not mean that there are

no real or statistically significant differences

in protection among alternative standards. To

the extent that the quoted statements from

CASAC’s closure letter are read as implying

that CASAC considered the differences not to

be statistically significant (or that there are no

differences at all in the protection afforded by

the alternative standards), EPA disagrees with

that reading.

Another group of commenters, while

supporting an 8–hour standard, specifically

opposed replacing the current 1–hour

standard with an 8–hour standard, but favored

instead both 8–hour and 1–hour standards.

These commenters generally felt that a

greater degree of public health protection than

that provided by the proposed standard was

warranted, and that standards based on both

averaging times were necessary to provide the

requisite protection from 1– and 8–hour

exposures of concern. These commenters

generally argued that an 8–hour standard

alone could still allow for high 1–hour

exposures of concern, or that the retention of

the current 1–hour standard was critical to

maintaining current pollution control

measures. As an initial matter, EPA is

delaying revocation of the 1–hour standard to

ensure an effective transition to the 8–hour

standard, as discussed in Unit II.B.4 of this

preamble. While EPA agrees that it is

possible that an 8–hour standard alone could

allow for high 1–hour exposures of concern,

at and above 0.12 ppm,12 EPA’s exposure

assessments estimate that alternative 8–hour

standards, at the proposed level of 0.08 ppm

but with different forms, would be very

effective in limiting 1–hour exposures, and

generally even more effective in limiting 1–

hour exposures of concern than is the current

1–hour standard. More specifically, the

updated assessment estimates that upon

attainment of alternative 8–hour, 0.08 ppm

standards, with forms ranging up to the fifthhighest concentration form, less than 0.1

percent of outdoor children are likely to

experience any 1–hour exposures greater than

0.12 ppm while at heavy exertion levels in

four to seven of the nine urban areas

analyzed, whereas this is true for only two of

the nine areas upon attainment of the current

1–hour standard. In all nine areas both the

current and alternative 8–hour, 0.08 ppm

standards are estimated to limit such

exposures to less than 1 percent of the

outdoor children. Thus, EPA concludes that

an 8–hour averaging time does effectively

limit both 1– and 8–hour exposures of

concern.

For the reasons discussed above in this

unit, and after taking into account the range

of views expressed in the public comments,

the Administrator finds that replacing the

current 1–hour standard with an 8–hour

standard, in combination with the decisions

on level and form described below, is

appropriate to provide adequate and more

uniform protection of public health from both

short-term (1 to 3 hours) and prolonged (6 to

8 hours) exposures to O3 in the ambient air.

2. Level. Taken together, the level and form

of the standard, for a given averaging time,

determine the degree of public health

protection afforded by the standard.

Consideration of the level of the standard

discussed in this unit of the preamble reflects

a recognition of this linkage between level

and form (discussed separately below in Unit

II.B.3).

The Administrator’s decision to propose

the level of an 8–hour primary O3 standard

at 0.08 ppm, and to solicit comment on

alternative levels, necessarily reflected a

recognition, as emphasized by CASAC, that

it is likely that ‘‘O3 may elicit a continuum

of biological responses down to background

concentrations’’ (Wolff, 1995b). Thus, in the

absence of any discernible threshold, it is not

possible to select a level below which

absolutely no effects are likely to occur. Nor

does it seem possible, in the Administrator’s

judgment, to identify a level at which it can

be concluded with confidence that no

‘‘adverse’’ effects are likely to occur. In such

a case, as CASAC has advised, the traditional

paradigm for standard-setting cannot be

applied in the usual way, and assessments of

risk ‘‘must play a central role in identifying

an appropriate level’’ (Wolff, 1995b). Thus,

the Administrator’s task became one of

attempting to select a standard level that

would reduce risks sufficiently to protect

public health with an adequate margin of

safety, since a zero-risk standard is neither

possible nor required by the Act. In this and

other NAAQS reviews the CASAC has

generally recognized that the selection of

specific standards requires that the

Administrator make public health policy

judgments in addition to determinations of a

strictly scientific nature. The Administrator’s

public health policy judgment on the level of

the proposed standard was framed by the

considerations discussed above in this unit

and informed by the following key

observations and conclusions:

(1) During the last review of the O3 criteria

and standards, CASAC concluded that the

existing 1–hour standard set at 0.12 ppm O3

provided ‘‘little, if any, margin of safety,’’

and that the upper end of the range of

consideration for a 1–hour standard should be

0.12 ppm (McClellan, 1989). In addition,

several members of the CASAC panel

recommended that consideration should be

given to a lower 1–hour level of 0.10 ppm

to offer some protection against effects for

which there was preliminary information at

that time of associations with 8–hour

exposures to O3.

Regarding currently available evidence of

O3-related effects:

(2) Based on a significant body of

information available since the last review,

there is now clear evidence from human

clinical studies that O3 effects of concern are

associated with the 6– to 8–hour exposures

tested. Studies were done at 6– to 8–hour

exposure levels of 0.12, 0.10, and 0.08 ppm.

This includes evidence of the following

statistically significant responses at 6– to 8–

hour exposures to the lowest concentration

evaluated, 0.08 ppm O3, at moderate exertion:

lung function decrements, respiratory

symptoms (e.g., cough, pain on deep

inspiration), nonspecific bronchial

responsiveness, and biochemical indicators of

pulmonary inflammation. Field studies
Federal Register / Vol. 62, No. 138 / Friday, July 18, 1997 / Prepublication 9

13 The upper end of this range, 3-expected-exceedances,

was based on air quality comparisons, since risk estimates

were only available at the time of proposal for the 1– and

5-expected-exceedance forms of a 0.09 ppm standard. This

range is consistent with the results of the updated risk

assessment.

provide evidence of similar functional and

symptomatic effects at ambient O3 exposures

that are consistent with the clinical findings.

Laboratory animal studies provide supporting

evidence of O3-induced biochemical

indicators of inflammation and functional

changes.

(3) Numerous epidemiological studies have

reported excess hospital admissions and

emergency department visits for respiratory

causes (for asthmatic individuals and the

general population) attributed primarily to

ambient O3 exposures, including O3

concentrations below the level of the current

standard, with no discernible threshold at or

below this level. The biological plausibility of

attributing such effects to ambient O3

exposures is supported by human studies

showing increased nonspecific bronchial

responsiveness, laboratory animal studies

showing pulmonary changes that decrease the

effectiveness of the lung’s defenses against

bacterial respiratory infections, and the

reasonable anticipation that O3 exposures also

increase the risk of respiratory infections in

humans, based on the many similarities

between animal and human defense

mechanisms.

(4) Long-term laboratory animal studies

suggest that changes in lung biochemistry and

structure may, under certain circumstances,

become irreversible, although it is unclear

whether long-term exposures to ambient O3

levels result in similar chronic health effects

in humans.

Regarding the types and severity of O3-

induced physiological effects that are

considered to be adverse to the health status

of individuals experiencing such effects:

(5) With regard to lung function

decrements and respiratory symptoms, the

Administrator recognized that these O3-

induced effects are transient and reversible,

and concluded that the extent to which such

effects are adverse to the health status of an

individual depends upon the severity,

duration, and frequency with which an

individual experiences such effects

throughout the O3 season. While group mean

responses in clinical studies at the lowest

exposure level tested of 0.08 ppm are

typically small or mild in nature, responses

of some sensitive individuals are sufficiently

severe and extended in duration to be

considered adverse. This would especially be

true to the extent that those individuals likely

to experience such effects would, on average,

experience them several times a year.

(6) With regard to increased hospital

admissions and emergency room visits, the

Administrator judged that such effects are

clearly adverse to individuals.

(7) With regard to pulmonary

inflammation, the Administrator recognized

that singular occurrences of inflammation are

likely reversible and potentially of little

health significance. On the other hand, based

on laboratory animal studies, repeated

inflammatory responses associated with

exposure to O3 over a lifetime have the

potential to result in damage to respiratory

tissue such that individuals later in life may

experience a reduced quality of life.

Furthermore, there is the possibility that

repeated pulmonary inflammatory responses

could adversely affect asthmatic individuals

by resulting in increased medication use,

medical treatment, and/or emergency room

visits and hospital admission. Such effects in

asthmatics are of special concern particularly

in light of the growing asthma problem in the

United States and the increasing rates of

asthma-related mortality and hospitalizations,

especially among children in general and

black children in particular. While O3 has not

been shown to cause asthma, the available

evidence suggests that O3 may exacerbate

asthma. Accordingly, the Administrator

judged that repeated exposures to O3 levels

that produce inflammation of the lungs are

adverse to individuals likely to experience

such exposures over long periods of time.

The Administrator considered the results of

the exposure and risk analyses and the

following key observations and conclusions

from these analyses in putting effects

considered to be adverse to individuals into

a broader public health perspective and in

making judgments about the level of a

standard that would reduce risk sufficiently to

protect public health with an adequate margin

of safety:

(8) The median risk estimates for

respiratory functional and symptomatic

effects, as well as for excess hospital

admissions of asthmatics for respiratory

causes, are approximately the same or only

marginally smaller for some of the 8–hour,

0.09 ppm standard options evaluated

(including those with forms ranging from 1-

to 3-expected-exceedances13) as compared to

the current 1–hour, 0.12 ppm NAAQS (risk

estimates are somewhat larger for an 8–hour,

0.09 ppm, 5-expected-exceedance standard as

compared to those for the current NAAQS).

(9) Within any given urban area,

statistically significant reductions in exposure

and risk associated with respiratory functional

and symptomatic effects result from

alternative 8–hour standards as the level

changes from 0.09 ppm to 0.08 ppm to 0.07

ppm. These reductions represent differences

of hundreds of thousands of times that

children in the nine urban areas included in

the analysis would likely experience such

effects under the range of alternative

standards considered relative to the current

standard. There are significant uncertainties in

such quantitative estimates, however, and

there is no break point or bright line that

differentiates between acceptable and

unacceptable risks within this range.

(10) Similarly, reductions in hospital

admissions for respiratory causes for

asthmatic individuals and the general

population are estimated to occur with each

change in the level of the standard from 0.09

ppm to 0.08 ppm to 0.07 ppm. However,

hospital admissions for asthmatic individuals

associated with ambient O3 exposures within

the range of standard levels under

consideration represent a relatively small

fraction of the total respiratory-related

hospital admissions for asthmatics over the

O3 season.

(11) Estimated exposures to O3

concentrations at and above 0.08 ppm (at

which increased nonspecific bronchial

responsiveness, decreased pulmonary defense

mechanisms, and indicators of pulmonary

inflammation have been observed in humans)

while engaged in moderate exertion are

essentially zero at the 0.07 ppm standard level

(with a 1-expected-exceedance form) for the

seven nonattainment areas evaluated in the

exposure analyses for the at-risk population

of outdoor children. Such exposures of

outdoor children increase to approximately 0

to 1 percent at the 0.08 ppm standard level,

while the estimated range at the 0.09 ppm

standard level increases to approximately 3 to

7 percent of outdoor children for these areas.

(12) While recognizing that sensitive

individuals may experience adverse but

transient effects with a standard set at 0.08

ppm, no CASAC panel member supported

selection of 0.07 ppm as the level of a

primary standard. Of the members who

expressed their personal views, three

indicated a preference for a level of 0.08 ppm,

one for a range of 0.08 to 0.09 ppm, three

for a level of 0.09 ppm (with one of the three

expressing a preference for selecting a form

that would result in equivalent protection to

the current standard), and one for a range of

0.09 to 0.10 ppm, associated with public

advisories for O3 levels at and above 0.07

ppm. Other CASAC panel members also

expressed support for such public notices or

advisories reflecting potential effects for

extremely sensitive individuals associated

with O3 levels as low as 0.07 ppm.

These observations and conclusions

resulted in the Administrator focusing in

particular on the alternative levels of 0.08

ppm and 0.09 ppm, having placed great

weight on the fact that none of the CASAC

panel members expressed support for a

standard set below 0.08 ppm. In deciding

between these two levels, the Administrator

took into account quantitative estimates of the

risks associated with attaining standards set at

these levels for those effects for which such

quantitative risk estimates could be

developed. Other factors that were important

in the Administrator’s proposed decision

include:

(1) Quantitative estimates of 8–hour

exposures of concern (i.e., at and above 0.08

ppm) associated with these standard levels.
10 Federal Register / Vol. 62, No. 138 / Friday, July 18, 1997 / Prepublication

14 These updated risk estimates in terms of the

percentage of outdoor children in the nine urban areas are

roughly comparable to the range of original estimates

presented in Table 1 of the proposal for 1- and 5-expectedexceedance forms of the standards.

15 Approximately 3.1 million outdoor children reside in

these nine urban areas.

(2) The consistency of the clinical, field,

and epidemiological studies, in which effects

were seen not only from controlled exposures

to 0.08 ppm, but also in ambient

environments in which 8–hour average O3

concentrations ranged from above to below

the 0.08 ppm level.

(3) The importance of increased protection

for those sensitive individuals who may

experience respiratory symptomatic and

functional effects at lower O3 concentrations

than the population as a whole.

(4) The uncertainties in considering the

potentially more serious but as yet uncertain

chronic effects.

As discussed above in Unit II.A.3., EPA

completed and made available for public

comment supplemental exposure and risk

assessments subsequent to the proposal. For

any of the alternative standards considered in

the assessment, the new estimates of

exposures at and above 0.08 ppm are

somewhat higher than those available at the

time of proposal, while the new estimates of

risks, for adverse effects including moderate

and large decreases in lung function,

moderate to severe respiratory symptoms, and

hospital admissions for asthmatics, are lower.

However, the relative differences in estimated

exposures and risks between alternative

standard levels remain about the same as at

the time of proposal. Thus, while the

Administrator’s final decision takes into

account the more recent assessments, the

differences in the quantitative results between

the initial and supplemental assessments do

not fundamentally alter the basis for the

judgments expressed at the time of proposal.

To aid in comparing the public health

protection associated with 8–hour standards at

the 0.08 ppm and 0.09 ppm levels,

observations from the updated exposure and

risk assessments for all nine urban areas

evaluated are summarized below (assuming

the third-highest concentration form, which

was the upper end of the range of

consideration for forms for the 0.09 ppm

level).

(1) The percentages of outdoor children

exposed to O3 concentrations at and above

0.08 ppm (at which increased nonspecific

bronchial responsiveness, decreased

pulmonary defense mechanisms, and

indicators of pulmonary inflammation have

been observed in humans) while engaged in

moderate exertion are estimated to be

approximately 3 percent at the 0.08 ppm

standard level, ranging from approximately 2

percent to 10 percent in the nine areas,

increasing to approximately 11 percent at a

standard level of 0.09 ppm, ranging from

approximately 7 percent to 29 percent in the

nine areas.

Updated risk estimates in terms of the

percentages14 and numbers of outdoor

children estimated to experience various

health effects, and the total numbers of

occurrences of these effects in outdoor

children, upon attainment of these two

alternative standards for all nine urban areas

combined15 are as follows:

(2) For moderate lung function (FEV1)

decreases ≥ 15 percent, approximately 6

percent of outdoor children (180,000

children) would experience this effect one or

more times per year (650,000 occurrences) at

the 0.08 ppm standard level, increasing to

approximately 8 percent of outdoor children

(250,000 children and 1,100,000 occurrences)

at the 0.09 ppm standard level.

(3) For large lung function (FEV1)

decreases ≥ 20 percent, approximately 2

percent of outdoor children (58,000 children)

would experience this effect one or more

times per year (100,000 occurrences) at the

0.08 ppm standard level, increasing to

approximately 3 percent of outdoor children

(97,000 children and 220,000 occurrences) at

the 0.09 ppm standard level.

(4) For moderate or severe pain on deep

inspiration, approximately 0.9 percent of

outdoor children (27,000 children) would

experience this effect one or more times per

year (120,000 occurrences) at the 0.08 ppm

standard level, increasing to over 1 percent of

outdoor children (41,000 children and

220,000 occurrences) at the 0.09 ppm

standard level.

Many public commenters supported EPA’s

proposed level of 0.08 ppm for an 8–hour

standard, including most public health

associations and groups of medical

professionals, many citizens, and some States

and regional associations. There were also

large numbers of commenters who expressed

strong views in opposition to the proposed

level. Of those who did not support the

proposed 8–hour level, almost all commenters

representing businesses and industry

associations, many local governmental groups

and private citizens, and some States either

supported no change to the current standard

or, if EPA were to replace the current 1–hour

standard with an 8–hour standard, supported

a level of 0.09 ppm directly or simply one

that would be ‘‘equivalent’’ to the current

standard. On the other hand, environmental

groups, many citizens, and some medical

professionals and researchers supported a

level of 0.07 ppm for an 8–hour standard.

In general, the issues raised by these

groups of commenters can be addressed in

three categories: Comments on the strength

and adequacy of the health effects evidence

upon which the proposed decision was based,

comments on the quantitative exposure and

risk assessments and the extent to which the

assessments either over- or under-predict

exposures and risks among sensitive

populations, and judgments as to whether the

differences in public health protection

provided by alternative standards are

significant from a public health perspective.

Each of these categories of key issues is

discussed separately below.

With regard to the first category of

comments, on the strength and adequacy of

the health effects evidence, commenters who

did not support the need for any increased

protection beyond that provided by the

current standard questioned the adequacy or

highlighted the limitations of the various

types of health effects studies that have

related O3 exposures to adverse effects. For

example, some commenters questioned the

controlled human exposure studies, arguing

that: Many such studies used patterns of

exposures and exercise levels that are not

representative of normal population exposures

to ambient O3; some exposure chambers

using artificially generated O3 may have been

contaminated with other pollutants that could

have accounted for some of the observed

effects; and responses to elevated O3 levels

were compared to responses to air with

essentially no O3 rather than to background

levels typical of ambient air. Some

commenters argued that these flaws in the

study designs would result in overestimating

responses to non-background levels of

ambient O3 or in erroneous findings of

statistical significance. In contrast, others

commented that because the chambers did not

contain other pollutants and natural

pulmonary irritants (e.g., pollens, dust) or a

full range of environmental conditions (e.g.,

high temperatures and humidity) typical of

ambient air, the results may underestimate the

true impact of O3 in the ambient air.

Some commenters also questioned the

summer camp and other field studies and

epidemiological studies reporting increased

hospital admissions and emergency room

visits, arguing that: The responses in these

studies were inherently confounded by

exposures to other pollutants, the camp

studies did not differentiate activity levels of

the participants, and linear regression down to

or below background levels was unjustifiably

used to analyze the results of the hospital

admission studies. These commenters

expressed the view that these and other flaws

call into question any conclusions about

whether the reported associations are causal.

In contrast, other commenters argued that the

hospital admissions reported in these studies

are indicative of a pyramid of adverse health

effects, including increased mortality,

increased visits to emergency and outpatient

departments and physicians, increased

numbers of asthma attacks resulting in

increased medication use, and increased

numbers of restricted activity days and acute

respiratory symptom days, that EPA has not

adequately taken into account. The EPA notes

that these comments are consistent with

statistics published by the U.S. Department of

Health and Human Services, which indicate
Federal Register / Vol. 62, No. 138 / Friday, July 18, 1997 / Prepublication 11

16 The initial risk assessment used both ‘‘Weibull’’ and

‘‘proportional’’ air quality adjustment procedures, whereas

the supplemental risk assessment used a ‘‘proportional’’

air quality adjustment procedure for all nine urban areas.

In responding to comments on the air quality adjustment

procedures, EPA also evaluated an alternative ‘‘quadratic’’

procedure (as discussed in the Response to Comments),

which generally resulted in risk estimates between those

from the Weibull and proportional procedures.

17 The two areas are Houston and parts of Los Angeles

county, which are two of only six areas nationwide with

peak 1– to 8–hour design value ratios greater than 1.5.

that for every hospital admission of an

individual with asthma for respiratory causes,

there are more than five emergency and

outpatient department visits and more than 20

office-based physician visits (U.S. DHHS,

1996).

With regard to studies related to pulmonary

inflammation and chronic respiratory damage,

some commenters argued that the linkage

between repeated inflammatory responses and

chronic respiratory damage was merely

speculation, and, therefore, should not be

considered as part of the basis for decisions

on the primary standard. In contrast, others

commented that animal studies had

demonstrated that repeated pulmonary

inflammation leads to degenerative or

irreversible lung damage, that these studies

are consistent with observations in human

exposure studies, and, therefore, that they

should be considered in decisions on the

standard.

The EPA notes that many of these

comments did not reflect an integrative

assessment of the evidence—the approach

CASAC has historically urged EPA to

follow—but rather a piecemeal look at each

individual study or type of study, which tends

to miss the strength of the entire body of

evidence taken together. Other commenters

did consider the body of evidence in a more

integrative manner, and many of these

commenters expressed the view that the body

of evidence as a whole provided clear

evidence of O3-related effects at and below

O3 concentrations allowed by the current

standard. Some commenters highlighted the

large number of studies that demonstrate

evidence of effects for prolonged exposures

at and below 0.08 ppm, and criticized EPA

for giving too little weight to those studies

which reported serious effects, but for which

the data were not sufficient to do quantitative

risk assessments.

With regard to the second category of

comments, on the exposure and risk

assessments, a number of commenters raised

concerns about key aspects of the

assessments, including the exposure model,

the development of concentration-response

functions, the application of the risk model,

and the measures of risk used to characterize

the results of the assessments. With regard to

the exposure model, a number of commenters

claimed that: The model overestimates the

exertion level that can be achieved by most

children and outdoor workers and the fraction

of time that these groups spend in moderate

or heavy exertion; the model overestimates

outdoor ambient exposures because fixed-site

monitors overestimate outdoor personal

exposures; and the air quality adjustment

procedures used to simulate attainment of the

standards are inappropriate or highly

uncertain. Other commenters expressed

concern that the exposure model may be

significantly underestimating exposures for

children and outdoor workers who repeatedly

exercise due to limitations in the available

human activity pattern data.

As discussed in the proposal, EPA

recognizes that the exposure model

necessarily contains many sources of

uncertainty, although every effort has been

made to account for such uncertainties to the

extent possible. In particular, the model

incorporates and is sensitive to analytical

procedures used to simulate spatial and

temporal distributions of O3 concentrations

that would occur as a result of an area just

attaining any of the alternative standards

addressed in the exposure assessment. These

air quality adjustment procedures are based

on generalized models intended to reflect the

patterns of changes in distributions of O3

concentrations that have historically been

observed in areas implementing control

programs designed to attain the O3 NAAQS.

The EPA recognizes that future changes in air

quality distributions are area-specific, and

will be affected by whatever specific control

strategies are implemented in the future to

attain the revised NAAQS. Thus, generalized

models are expected to be more uncertain for

any given area than when exposure results are

aggregated across many areas (as was done

across the nine urban areas analyzed in EPA’s

exposure assessment).

Some commenters questioned the specific

air quality adjustment procedure used in the

initial and supplemental assessment16, and a

few of these commenters recommended

revisions or alternative procedures that they

believed would be more representative of

historical or projected future air quality

patterns. As discussed in more detail in the

Response to Comments, EPA acknowledges

that both procedures used in the assessments

result in projections of air quality that deviate

to some degree from historical patterns of air

quality changes observed in specific urban

areas, and that other procedures may be more

representative of air quality patterns in

specific areas. While EPA will take these

comments into account as future refinements

are made to the air quality adjustment

procedures used in the exposure model, EPA

believes, and CASAC concurred, that the

procedures used in the assessments conducted

as part of this review are reasonable given the

uncertainties inherent in projecting future

changes in air quality patterns.

In commenting on the air quality

adjustment procedure used in the

supplemental assessment, some commenters

particularly focused on the results for two of

the nine areas analyzed in which, contrary to

results from the initial assessment, lower risks

were estimated for the current standard as

compared to the proposed standard. As

discussed more fully in the Response to

Comments, EPA believes that these results

for each area cannot be distinguished within

the sensitivity of the alternative air quality

adjustment procedures used in the initial and

supplemental assessments. Further, EPA

notes that these two areas have much higher

ratios of peak 1–hour to 8–hour O3

concentrations than the vast majority of areas

in which O3 is monitored17, and it is thus

reasonable to expect that generalized air

quality adjustment procedures would be

particularly uncertain for such areas.

Comments focusing on the development of

concentration- response functions for use in

the risk model have included a number of

claims. Some commenters claimed that EPA

inappropriately selected studies for

developing the functions by excluding studies

that reported lower response rates and by

using only studies conducted by EPA

scientists. Some commenters asserted that

contaminants in the controlled exposure

chambers may be responsible for some of the

effects incorporated into the concentrationresponse functions for O3. Further, some

commenters asserted that it was inappropriate

to extrapolate the concentration-response

functions to background levels or to develop

concentration-response functions for

symptomatic responses in children based on

studies of such responses in adults.

Of the comments focusing on the

application of the risk model, some

commenters claimed that the aggregate risk

results were overstated because of: Many of

the methodological problems noted in the

above summary of comments, the failure to

take into account the known attenuation of

effects, and the assumption of an

inappropriately low background concentration

in calculating risks attributable to nonbackground sources of O3. On the other hand,

other commenters claimed that aggregate risk

results were understated because of:

Methodological problems, noted above, that

underestimate exposures, limiting the

analyses to only a subset of adverse health

effects rather than estimating the full range

of effects that have been attributed to O3, and

by focusing only on nine urban areas rather

than projecting risk reductions from

alternative standards nationally.

While EPA has included comprehensive

responses to these comments in the Response

to Comments, most of the issues and concerns

raised by commenters concerning the health

effects evidence and the methods used in the

exposure and risk assessments are essentially

restatements of concerns raised during the

review of the Criteria Document and the

development and review of these quantitative

assessments as part of the preparation and
12 Federal Register / Vol. 62, No. 138 / Friday, July 18, 1997 / Prepublication

18 The EPA anticipates that additional people would be

protected through regional measures adopted for purposes

of an 8–hour, 0.08 ppm standard.

review of the Staff Paper. EPA presented and

the CASAC reviewed in detail the approaches

used to assess exposure and health risk, the

studies and health effect categories selected

for which concentration-response functions

were estimated, and the presentation of the

exposure and risk results summarized in the

Staff Paper. As stated in the proposal, EPA

believes and CASAC concurred, that the

general models selected to estimate exposure

and risk are appropriate and that the methods

used to conduct the exposure and risk

assessments represent the state of the art.

EPA does not believe that the exposure or

risk assessments are fundamentally biased in

one direction or the other as claimed in some

of the comments.

The Administrator and CASAC have

recognized, however, that there are many

uncertainties inherent in such assessments and

that the resulting ranges of quantitative risk

estimates do not reflect all of the uncertainties

associated with the numerous assumptions

inherent in such analyses (Wolff, 1995b).

EPA summarized some of the most important

caveats and limitations concerning both the

exposure analyses and the risk assessments

for lung function changes, respiratory

symptoms, and hospital admissions in the

proposal. A more complete discussion of

assumptions and uncertainties is contained in

the Staff Paper and technical support

documents (Johnson et al., 1996 a,b;

Whitfield et al., 1996; Richmond, 1997).

With regard to the third category of

comments, reflecting commenters’ judgments

as to whether the differences in public health

protection of alternative standards are

significant from a public health perspective,

EPA notes that highly divergent judgments

were expressed by different groups of

commenters. A large number of commenters

who expressed the view that the differences

in public health protection were not

significant or important enough to warrant

any standard more stringent than the current

standard used CASAC as the basis for their

position, as discussed above in Unit II.B.1. on

averaging time. Others cited small

percentages of outdoor children and other

sensitive groups likely to be affected based

on EPA’s assessment, or even smaller

percentages as modified by analyses

conducted by the commenter to correct

perceived errors in the analyses. In contrast,

other commenters cited large total numbers of

children likely to be affected, not only for the

subset of O3-related effects and the nine areas

analyzed in EPA’s assessments, but also for

a broader array of related effects projected

nationally.

The core issue in this review of the primary

O3 standard, as stated by the Administrator

at the time of proposal, is who is to be

protected, and from what. Clearly, for

pollutants, such as O3, that have no

discernible thresholds for health effects, no

standard can be risk-free. The Administrator’s

task is to select a standard level that will

reduce risks sufficiently to protect public

health with an adequate margin of safety

since a zero-risk standard is neither possible

nor required by the Act. As CASAC and the

Administrator recognize, the selection of a

specific standard level for such pollutants

requires public health policy judgments in

addition to determinations of a strictly

scientific nature.

In making such judgments, the

Administrator rejects the notion that because

standards cannot be risk-free they should not

be revised to provide increased protection for

sensitive populations, particularly including

children in this case, when available evidence

points to greater impacts on public health

than had previously been demonstrated. In

carefully reassessing both those risks to

public health that can be quantified as well

as those for which quantitative risk

information is more limited, the

Administrator has focused on the following

comparisons between the degree of public

health protection likely to be afforded by an

8–hour standard at the proposed level of 0.08

ppm and an alternative standard set at a level

of 0.09 ppm (assuming the same third-highest

concentration form):

(1) Based on EPA’s updated analyses of

estimated moderate or large decreases in lung

function and moderate to severe pain on deep

inspiration in outdoor children in nine urban

areas (Richmond, 1997), a standard set at

0.09 ppm would allow approximately 40

percent to 65 percent more outdoor children

to experience such effects than would a 0.08

ppm standard, and approximately 70 percent

to 120 percent more occurrences of such

effects in outdoor children per year.

(2) While only relatively small percentages

of outdoor children are estimated to

experience such effects, the differences in

these percentages between the two standard

levels represent tens of thousands more

children, and hundreds of thousands more

occurrences of adverse effects in these

children, in these nine urban areas alone, for

a 0.09 ppm standard as compared to a 0.08

ppm standard.

(3) Based on EPA’s updated risk

assessment of increased hospital admissions

in New York City (Richmond, 1997), a

standard set at 0.09 ppm would allow

approximately 40 more excess hospital

admissions of asthmatics within an O3 season

in New York City for respiratory causes as

compared to a 0.08 ppm standard, which

represents approximately a 40 percent

increase in excess O3-related admissions, but

only approximately a 0.3 percent increase in

total admissions of asthmatics. The EPA

believes that while these numbers of hospital

admissions are relatively small from a public

health perspective, they are indicative of a

pyramid of much larger numbers of related

O3-induced effects, including respiratoryrelated hospital admissions among the general

population, emergency and outpatient

department visits, doctors visits, and asthma

attacks and related increased use of

medication that are important public health

considerations.

(4) Based on EPA’s exposure analyses in

the nine urban areas, a standard set at 0.09

ppm would allow more than three times as

many children to experience 8–hour average

exposures of concern as would a 0.08 ppm

standard, with the number of outdoor children

likely to experience such exposures

increasing from approximately 100,000 to

more than 300,000 in the nine urban areas

alone, representing an increase from

approximately 3 percent to approximately 11

percent of the outdoor children likely to

experience such exposures.

(5) These exposures of concern are judged

by EPA to be an important indicator of the

public health impacts of those O3-related

effects for which information is too limited

to develop quantitative estimates of risk, but

which have been observed in humans at a

level of 0.08 ppm for 6– to 8–hour exposures.

Such effects include the following: increased

nonspecific bronchial responsiveness (related,

for example, to aggravation of asthma),

decreased pulmonary defense mechanisms

(suggestive of increased susceptibility to

respiratory infection), and indicators of

pulmonary inflammation (related to potential

aggravation of chronic bronchitis or longterm damage to the lungs).

(6) To put these risks and exposures into

broader perspective, EPA notes that

approximately 46 million more people,

including approximately 13 million more

children and 3 million more individuals with

asthma, live in areas that would not attain a

0.08 ppm standard compared to a 0.09 ppm

standard. The general population as well as

children and asthmatics would breathe cleaner

air as a direct result of control measures

designed to bring areas into attainment with

the proposed standard.18

While recognizing the inherent

uncertainties in these estimates, and after

taking into account the range of views and

judgments expressed in the public comments,

the Administrator finds the public health

impacts described in the proposal, as updated

above, to be important and sufficiently large

as to warrant a standard set at a level of 0.08

ppm, as proposed.

The Administrator recognizes the views of

those who argue that similarly large

improvements in public health protection

would result from a standard set at 0.07 ppm

as compared to the proposed standard, such

that, based on the same reasoning, the

evidence warrants a standard set at 0.07 ppm.

In considering these views, the Administrator

gives significant weight to the following

considerations:

(1) No member of the CASAC panel of

experts supported a standard set lower than
Federal Register / Vol. 62, No. 138 / Friday, July 18, 1997 / Prepublication 13

19 The term ‘‘expected’’ means that the numbers of

exceedances per year are averaged over 3 years and may

be calculated using specific adjustments to account for

missing data.

20 The 1-expected-exceedance form essentially requires

the fourth-highest air quality value in 3 years, based on

adjustments for missing data, to be less than or equal to

the level of the standard for the standard to be met at an

air quality monitoring site.

21 Areas that ‘‘just attain the standard’’ are defined as

those whose design value falls between 0.075 and 0.084

ppm.

22 Peak 8–hour average concentrations are defined in

terms of the fourth-highest daily maximum concentration

in 3 years (i.e., the design value for the current 1-expectedexceedance form of the standard).

23 The results of these air quality analyses are presented

in Freas (1996) and summarized in the proposal for the

third- and fifth-highest concentration forms and the 3– and

5-expected-exceedance forms. Based on these

considerations, and the air quality comparisons in

particular, the Administrator judged that the middle of the

range of exceedances considered, three expected

exceedances, or the comparable third-highest

concentration, represented a reasonable policy choice, and

proposed the 3–year average of the annual third-highest

daily maximum 8–hour average O3 concentrations as the

form of the standard. In recognition of a range of views

on the degree of health protection that would be

appropriate, she also solicited comment on other

concentration-based forms, including the second-, fourth-

, and fifth-highest concentration forms.

0.08 ppm, specifically after considering a

range of alternative standards that included

0.07 ppm.

(2) The most certain O3-related effects,

while judged to be adverse, are transient and

reversible (particularly at O3 exposures below

0.08 ppm), and the more serious effects with

greater immediate and potential long-term

impacts on health are less certain, both as to

the percentage of individuals exposed to

various concentrations who are likely to

experience such effects and as to the longterm medical significance of these effects.

(3) As many commenters have noted, based

on information in the Criteria Document with

regard to ambient concentrations of O3 from

background sources, an 8–hour standard set

at a 0.07 ppm level would be closer to peak

background levels that infrequently occur in

some areas due to nonanthropogenic sources

of O3 precursors, and thus more likely to be

inappropriately targeted in some areas on

such sources.

After taking into account the public

comments, and for the reasons outlined

above, the Administrator finds that a standard

set at a level of 0.07 ppm is not requisite to

protect public health with an adequate margin

of safety.

3. Form. The form of the current 1–hour,

0.12 ppm standard is a ‘‘1-expectedexceedance’’ form. That is, the current

standard is based on the expected19 number

of days per year, on average over 3 years, on

which the level of the standard is exceeded,

and limits that number of expected

exceedances to be less than or equal to 1.0.

In evaluating alternative forms for the

primary standard, the adequacy of the public

health protection provided was the

Administrator’s foremost consideration. The

Administrator also recognized, however, that

concerns have been raised with the current

form since it was promulgated in 1979 due

to the inherent lack of year-to-year stability

in the measure of air quality on which the 1-

expected-exceedance form is based.20 The

CASAC specifically took such concerns into

account in recommending that the current

form be revised and in noting that a more

robust, concentration-based form would

minimize such instability and provide some

insulation from the impacts of extreme

meteorological events that are conducive to

O3 formation (Wolff, 1995b). Such instability

can have the effect of reducing public health

protection by disrupting ongoing

implementation plans and associated control

programs.

As discussed in the proposal, based on

information presented in sections IV. and V.I

of the Staff Paper and the advice of CASAC,

the Administrator focused her consideration

on the following alternatives:

(1) Revising the current 1-expectedexceedance form of the standard to allow for

multiple (up to five) expected exceedances

per year, averaged over 3 years. A multipleexceedance form would be based on a less

extreme air quality statistic and, thus, would

increase the stability of the expectedexceedance form.

(2) Adopting a concentration-based

statistic, such as the 3–year average of the

nth-highest daily maximum 8–hour average

O3 concentration, as an alternative to an

expected exceedance statistic. Air quality

analyses presented in the Staff Paper indicate

that the 3–year averages of the annual third-

, fourth-, and fifth-highest daily maximum 8–

hour concentrations would provide

approximately the same health protection as

the 3-, 4-, and 5-expected-exceedance forms

averaged over the same period, respectively.

It was the consensus of the CASAC Panel

that this range of allowable exceedances (i.e.,

up to 5 exceedances), and the consideration

of comparable concentration-based forms,

was appropriate. Further, CASAC

acknowledged that selecting from within this

range of alternative forms is a policy

judgment, especially given the nature of the

health effects and the absence of a ‘‘bright

line’’ that clearly differentiates between

acceptable and unacceptable risks within this

range. All 10 CASAC Panel members who

expressed specific opinions on the form of the

standard favored one that would allow for

multiple exceedances (Wolff, 1995b).

In reaching her proposed decision on the

form of an 8–hour standard set at 0.08 ppm,

the Administrator had to choose a specific

form within the range of up to 5 allowable

exceedances or up to the comparable fifthhighest concentration, and either an

exceedance-based or a concentration-based

form. As discussed in the proposal, in

considering possible forms within the range

of 1 to 5 exceedances (or their concentrationbased counterparts) the Administrator took

into consideration aggregate risk estimates for

those health effects for which quantitative

risk analyses have been done; estimated

exposures associated with those effects for

which no quantitative risk estimates could be

developed; and the magnitude of peak

measurements of 8–hour average O3

concentrations, and the number of days on

which the level of the standard would likely

be exceeded, based on an analysis of

historical air quality data (Freas, 1996). In

considering exposure and risk estimates

available at the time of proposal for 1– and

5-expected-exceedance forms, the

Administrator noted that the level of the

standard is a more dominant factor in

determining the degree of exposure and risk

reductions achieved, with the form being

associated with smaller differences in risk

estimates within a continuum of risk. In

considering air quality comparisons for

standards across the range of forms

considered, the Administrator focused in

particular on the extent to which alternative

forms would limit the number of days in

which the level of the standard would be

exceeded in areas that just attain the

standard21, and the magnitude of peak 8–hour

average O3 concentrations22 that would occur

in such areas.23 More specifically, the

Administrator took into consideration the

percentage of monitoring sites just attaining

an 8–hour, 0.08 ppm standard that would

have 8–hour peak O3 concentrations above a

benchmark level of 0.09 ppm. This

benchmark level is the upper end of the range

of levels endorsed by CASAC for an 8–hour

O3 standard. The Administrator believes,

given the uncertainties associated with this

kind of complex health decision, that it is an

appropriate goal to limit the percentages of

areas experiencing such daily peaks.

In choosing to propose a concentrationbased form, the Administrator recognized the

advantages of a concentration-based form

over an exceedance-based form. As discussed

in the proposal, the principal advantage of a

concentration-based form is that it is more

directly related to the ambient O3

concentrations that are associated with health

effects. That is, given that there is a

continuum of effects associated with

exposures to varying levels of O3, the extent

to which public health is affected by exposure

to ambient O3 is related to the actual

magnitude of the O3 concentration, not just

whether the concentration is above a specified

level. With an exceedance-based form, days

on which the ambient O3 concentration is

well above the level of the standard are given

equal weight to those days on which the O3

concentration is just above the standard (i.e.,

each day is counted as 1 exceedance), even

though the public health impact on the two

days is significantly different. With a

concentration-based form, days on which

higher O3 concentrations occur would weigh

proportionally more than days with lower O3

concentrations, since the actual concentrations
14 Federal Register / Vol. 62, No. 138 / Friday, July 18, 1997 / Prepublication

are used directly in determining whether the

standard is attained. A concentration-based

form also has greater temporal stability than

the expected-exceedance form and, thus,

would facilitate the development of more

stable implementation programs by the States.

As discussed above in Units II.A.3. and

II.B.2., EPA completed and made available

for public comment supplemental exposure

and risk assessments subsequent to the

proposal. These updated assessments, which

specifically analyzed the third- and fifthhighest concentration-based forms, aid in

comparing the differences in public health

protection among alternative concentrationbased forms within the range considered in

the proposal for 8–hour, 0.08 ppm standards.

Based on these updated assessments, the

Administrator again notes that the level of the

standard is the more dominant factor in

determining the degree of risk reduction

achieved, with these alternative forms being

associated with much smaller differences in

risk estimates within a continuum of risk. For

example, within the nine urban areas included

in the risk assessment, approximately 180,000

outdoor children would experience moderate

lung function (FEV1) decreases ≥ 15 percent

upon attainment of an 8–hour, 0.08 ppm

standard with a third-highest concentration

form, compared to approximately 200,000

outdoor children with a fourth-highest

concentration form and 220,000 outdoor

children with a fifth-highest concentration

form.

The public comments include a large

number that specifically addressed the form

of the standard. Those commenters who

expressed views on the form of the standard

can be divided into three groups, according

to the level of 8–hour standard and the

relative degree of public health protection that

the commenter supported. These groups

include: Commenters who supported an 8–

hour, 0.08 ppm standard to provide increased

public health protection relative to the current

standard; commenters who supported either

an 8–hour, 0.09 ppm standard, or simply an

8–hour standard ‘‘equivalent’’ to the current

standard; and commenters who supported an

8–hour, 0.07 ppm standard to provide a

greater margin of safety than that afforded by

the proposed standard.

The first group included many private

citizens, some medical professionals and

researchers, and some States and local

governmental groups. While a number of

commenters in the first group specifically

supported the proposed third-highest

concentration form, generally for the reasons

presented in the proposal, others supported

either a 1-expected-exceedance form or a

concentration-based form in the upper part of

the range (i.e., the fourth- or fifth-highest

forms). The second group of commenters,

which included many local governmental

groups and private citizens, some States, and

most commenters representing businesses and

industry associations, almost exclusively

supported a concentration-based form in

general, and a form in the upper part of the

range (or above the range) in particular. In

sharp contrast, the third group of commenters,

which included environmental groups, many

private citizens, and some medical

professionals and researchers, almost

exclusively supported a 1-expectedexceedance form in conjunction with an 8–

hour, 0.07 ppm standard to provide the largest

margin of safety within the range of

alternative standards considered.

To the extent that the second and third

groups of commenters argued for a different

level than the Agency adopts today, the

Administrator disagrees with their comments

for the reasons set forth in the discussion of

the standard level above in Unit II.B.2. To the

extent that they argued for more than 5

exceedances (or the concentration-based

equivalent), the Administrator disagrees with

their views because such forms fall outside

the range recommended by CASAC and

would provide less public health protection

than she deems appropriate. To the extent that

the second and third groups of commenters

addressed the merits of particular forms

within the range of forms considered in the

proposal, they raised points similar to those

raised by commenters in the first group.

These points are discussed below.

Among the commenters in the first group

(i.e., those supporting an 8–hour, 0.08 ppm

standard to provide increased public health

protection), many felt that there was no

compelling basis for selecting the thirdhighest rather than the fourth- or fifth-highest

concentration-based form. These commenters

frequently quoted CASAC’s closure letter

(Wolff, 1995b) as stating ‘‘that there is no

bright line’ which distinguishes any of the

proposed standards (either the level or the

number of exceedances) as being significantly

more protective of public health,’’ and that

‘‘the selection of a specific level and number

of allowable exceedances is a policy

judgment.’’ In general, these commenters did

not give weight to the air quality comparisons

that were a major consideration in the

Administrator’s decision to propose the thirdhighest concentration form. Some

commenters seem to view such air quality

comparisons, particularly with regard to

pollutants such as O3 that have no discernible

threshold of effects, as relating more to

people’s perceptions of how well air pollution

is controlled than to any objective measure of

actual risks to public health.

These commenters made a number of

points in questioning the need to specify an

8–hour, 0.08 ppm standard in terms of the

third-highest rather than the fourth- or fifthhighest concentration form. Many noted that

a change to an 8–hour averaging time in and

of itself would appropriately focus air quality

management programs on prolonged

exposures of most concern. Further, many

noted that a level of 0.08 ppm, regardless of

the form within the range of forms considered

in the proposal, would provide significantly

increased protection from O3-related risks to

public health associated with acute effects

(i.e., those resulting from short-term and

prolonged exposures) for which they believe

there is sufficient evidence to be used as a

basis for a standard at this time. Some of

these commenters expressed the view that the

potential for chronic effects (i.e., those

resulting from long-term exposures) would be

better addressed through continued research,

rather than by adding a greater margin of

safety to a revised standard based primarily

on effects of short-term and prolonged

exposures. Many of these commenters

recognized, as did EPA in the proposal, that

there is a continuum of risks associated with

O3 exposures, that no standard can therefore

be risk-free, and that there are large

uncertainties in any estimates of the degree

of protection associated with alternative

forms. In general, these commenters also

noted that, for the same reasons, CASAC

advised that the selection of a form from

within the range considered in the proposal

was a policy judgment, not one that could be

decided on the basis of science alone. In

essence, these commenters argued that a more

restrictive form than the upper part of the

range endorsed by CASAC is not requisite to

protect public health.

In contrast, other commenters in the first

group (i.e., those supporting an 8–hour, 0.08

ppm standard) supported either the proposed

third-highest or second-highest concentration

form or a 1-expected-exceedance form. These

commenters generally gave greater weight to

limiting the magnitude of peak O3

concentrations and the number of days on

which the standard level would be exceeded

in areas meeting such a standard, and, in

some cases, to providing a greater margin of

safety to account for potential chronic effects.

Such views suggest that limiting the number

of days on which the standard level would be

exceeded, for example, is an important factor

in risk communication and in the public’s

understanding of the degree to which a

standard protects people from exposures to

O3 that may interfere with their ability to

engage in normal activities or may result in

the need for increased medication or medical

treatment, especially for those individuals

with asthma or other respiratory diseases. As

discussed above in this unit, although some

of these commenters felt that the third-highest

concentration form would protect public

health while also providing increased

stability, others expressed concern that public

health could be compromised by any form

that allowed for multiple exceedances of the

standard. The advantages of forms that allow

for multiple exceedances, thus providing

increased stability as discussed in the

proposal, and the views of the CASAC panel

members who expressed opinions, all of

whom favored such forms, were not given
Federal Register / Vol. 62, No. 138 / Friday, July 18, 1997 / Prepublication 15

weight by commenters within this group who

supported a 1-expected-exceedance form.

The Administrator has carefully reassessed

the relative risks to public health of specific

forms within the range of the second- to fifthhighest concentration forms or their

exceedance-based equivalents, taking into

account the public comments summarized

above, and the advice from CASAC Panel

members that the current form be replaced by

a form that allows multiple exceedances. In

doing so, the Administrator focused on the

following considerations:

(1) The CASAC advised that

concentration-based forms, within the range

considered up to the fifth-highest

concentration form, are appropriate for a

health-based primary O3 standard, and that

selection from within this range is a policy

judgment that cannot be based on science

alone. This advice reflects CASAC’s

recognition that O3 exhibits a continuum of

effects, such that there is no discernible

threshold above which public health

protection requires that no exposures be

allowed or below which all risks to public

health can be avoided. The CASAC also

recognized that a concentration-based form

would increase the stability of the standard by

providing some insulation from the impacts

of extreme meteorological events (Wolff,

1995b).

(2) Estimates of the differences in risk to

public health, for those effects that could be

considered quantitatively, within a range of

alternative forms from the second- to fifthhighest concentrations (for an 8–hour, 0.08

ppm standard) are relatively small compared

to the differences between alternative levels.

In other words, the choice of level is

substantially more important to the degree of

public health protection afforded by the

standard than the choice of form from within

this range of forms.

(3) Measures that distinguish between the

alternatives within the range of the secondto fifth-highest forms, based on air quality

analyses, reflect considerations related to how

some individuals understand the degree to

which an air quality standard protects public

health. These considerations are a distinct

aspect of risk communication to individual

citizens even though the days on which

exceedances occur are accounted for in

EPA’s quantitative assessments of risks to

public health.

(4) To assess the comparative effect of all

forms within the range of the second- to fifthhighest concentration forms, EPA considered

air quality comparisons for all such forms

(Freas, 1996). These comparisons (based on

1993 to 1995 data) show that 8–hour, 0.08

ppm second- and third-highest concentration

standards are very similar in that each

standard limits the percent of monitoring sites

that would experience peak days above the

benchmark level of 0.09 ppm to 1 percent of

such sites, and the number of days on which

the standards would likely be exceeded in the

worst of 3 years would be no more than 6

and 7, respectively. While less restrictive than

either of these standards, an 8–hour, 0.08 ppm

fourth-highest concentration standard would

be significantly more restrictive than a fifthhighest standard. For example, the 8–hour,

0.08 ppm fourth-highest concentration

standard would limit the percent of

monitoring sites that would experience peak

days about the benchmark level of 0.09 ppm

to 8 percent of such sites, and the number of

days on which the standards would likely be

exceeded in the worst of 3 years would be

no more than nine. In comparison, the fifthhighest concentration standard would limit

the percent of monitoring sites that would

experience peak days about the benchmark

level of 0.09 ppm to 17 percent of such sites,

and the number of days on which the

standards would likely be exceeded in the

worst of 3 years would be no more than 11.

(5) The extent to which the alternatives

within the range of the second- to fifthhighest concentration forms provide

protection against the more serious, but less

certain effects that have been associated with

exposure to O3, including potential chronic

effects, cannot be quantitatively assessed at

this time. Given that all such forms would

result in significant reductions in exposures to

O3 at and above 0.08 ppm (the level where

suggestive evidence of such effects is

available), any form within this range would

provide some margin of safety against these

effects.

Based on these considerations, the

available health effects evidence, the

quantitative assessments contained in the

Criteria Document, Staff Paper, and

supplemental analyses and supporting

documents, and the range of views and

judgments expressed in the public comments

on the appropriate form, the Administrator

has reconsidered the form of the standard that

is requisite to protect public health with an

adequate margin of safety. As an initial

matter, the Administrator has decided to

adopt a concentration-based form which

allows for more than one exceedance. While

the Adminstrator understands the views of the

many citizens who are concerned about a

standard that would allow for multiple days

on which the level of the standard may be

exceeded, the Administrator concludes that

such concerns are more relevant for pollutants

that exhibit a clear threshold of effects than

for pollutants such as O3 that exhibit a

continuum of effects. The Administrator

believes that the public health risks associated

with such pollutants can be appropriately

addressed through a standard that allows for

multiple exceedances to provide increased

stability, but that also significantly limits both

the number of days on which the level may

be exceeded and the magnitude of such

exceedances. This approach recognizes that

exposures associated with such exceedances

are already reflected in the exposure and risk

assessments that were an important

consideration in selecting a 0.08 ppm level

for the primary O3 standard, and that

increased stability in the standard is important

to avoid disruption to ongoing control

programs, and thus to maintain ongoing

public health protection.

Having again concluded that a

concentration-based O3 standard that allows

for multiple exceedances is appropriate, the

Administrator considered the extent to which

the form of an 8–hour standard should be

selected so as to provide a margin of safety

against possible, but uncertain chronic effects.

The Administrator carefully considered the

views of the many commenters who

emphasized the uncertainties in the evidence,

primarily from laboratory animal studies, that

was available in this review of the criteria and

standards to relate long-term exposures to

ambient levels of O3 to possible chronic

effects in humans. These commenters, as did

CASAC, advised that further research into

potential chronic effects in humans should be

continued, and the results considered in the

next review of the O3 standard. The

Administrator is persuaded that the difference

between the margins of safety for these

potential chronic effects afforded by the

alternatives within the range of the secondto fifth-highest concentration forms is not

well enough understood at this time to use as

the basis for choosing the most restrictive

forms (i.e., the second- or third-highest

concentration form). On the other hand, the

Administrator also judges that the relatively

large percentage of sites that would

experience O3 peaks above a benchmark level

of 0.09 ppm even when attaining a fifthhighest concentration standard and the

number of days on which the level of a fifthhighest concentration standard may be

exceeded argue against choosing that form,

which is the least restrictive within the range

considered.

For the reasons outlined above, and taking

into account the range of views in the public

comments, the Administrator concludes that

an intermediate form, the fourth-highest

concentration form, would serve to

appropriately balance these public health

considerations in conjunction with the 8–hour

averaging time and 0.08 ppm level selected,

as discussed above in Units II.B.1. and

II.B.2., that are of primary importance in

determining the degree of public health

protection afforded by the standard. In

addition, the Administrator notes that based

on an analysis of air quality in counties that

would attain an 8–hour, 0.08 ppm fourthhighest concentration standard (based on

1993–1995 data), over 99 percent of such

counties would be expected to have four or

fewer days on which the level of the standard

is exceeded in an average year (Freas, 1997).

This number of exceedances is clearly within

the range of multiple exceedances that

CASAC judged to be appropriate for a healthbased primary O3 standard. Thus, in the

Administrator’s judgment, based on the
16 Federal Register / Vol. 62, No. 138 / Friday, July 18, 1997 / Prepublication

information currently available, an 8–hour,

0.08 ppm standard with a fourth-highest

concentration form will protect public health

with an adequate margin of safety.

In the proposal, which maintained the

current approach of using air quality data

from the monitor measuring the highest O3

concentrations in an area to determine

whether the primary standard for O3 is

attained, the Administrator solicited comment

on the alternative of using some form of

averaging across monitors. As discussed in

the proposal, EPA recognized that during the

review of the Staff Paper, a number of

commenters suggested that averaging across

monitors might be appropriate to increase the

degree to which monitoring data used in

determining attainment of the standard

reflects population exposure and aggregate

population health risk. Further, these

commenters suggested that averaging data

from multiple monitors in an area would

produce a more stable measure of air quality

and would take into account broader

population exposure patterns across an area

than would the current approach of

considering data from each monitor

independently.

The Administrator did not propose the use

of spatial averaging because of concerns

outlined in the proposal including: The

difficulty in determining an appropriate level

for a spatially averaged primary standard

given that the bulk of the human health

effects evidence supporting a decision on an

appropriate O3 standard is based on

controlled human exposure studies that relate

known O3 exposures directly to responses in

individuals; and questions as to whether

adequate health protection would be provided

to individuals within the populations that live

or work in communities that routinely

experience higher O3 concentrations within a

broad metropolitan area.

To address these two concerns, it would be

necessary to define criteria for geographic

locations or communities (e.g., spatial

averaging zones) within which the use of

spatially averaged O3 data would be

acceptable. Such criteria would be important

since O3 air quality concentrations can vary

significantly across most urban areas. The

lowest concentrations typically occur in the

urban center and in locations near O3

precursor sources, mid-range concentrations

in neighborhoods and locations surrounding

the urban center, and peak concentrations are

typically measured downwind along the

outermost suburban regions of the urban area.

Also, the location of residences, schools,

parks, and other places where individuals

might be exposed more frequently to ambient

O3 concentrations of concern would be an

important consideration. Unless the O3

concentration gradients within each spatial

averaging zone were relatively homogeneous,

there may be significant numbers of sensitive

individuals exposed to high O3 concentrations

in areas where the spatial average indicates

that the overall air quality is acceptable.

In the proposal, EPA also noted the need

to help State and local governments devise

different O3 monitoring networks by revising

relevant regulations and guidance, should

spatial averaging be adopted. This would

likely involve defining general criteria for

monitoring network design, siting, and spatial

averaging zones in nationally implementable

terms, with case-by-case evaluation of each

monitoring network. The EPA recognized that

this activity would place additional burdens

on State and local air quality management

districts.

In soliciting comment on whether it would

be desirable to adopt some form of spatial air

quality averaging for O3, the Administrator

also solicited comment on specific alternative

approaches that could be used to address the

issues of concern. In particular, the

Administrator was interested in analyses that

inform questions about monitoring network

design, siting requirements, and approaches

for specification of spatial averaging zones;

the distribution of public health protection

that would result from such alternative

approaches; and the extent to which the level

of the standard would need to be adjusted, if

any, to provide public health protection

consistent with the level of protection

contemplated in the proposal.

The EPA received many comments on the

subject of using spatially averaged data to

determine when the primary standard for O3

is attained. Commenters from business and

industry associations frequently supported the

use of spatially averaged data, as did many

local governments and a small number of

States, principally because it would provide

a more stable air quality indicator and would

better represent population exposure and risk.

Some of these commenters felt that the use

of spatial averaging would be consistent with

the use of risk assessment as a policy tool for

standard setting. Many of these commenters

agreed that the heterogeneity of O3

concentrations across geographic areas would

need to be addressed by network design, with

a few expressing the opinion that this would

not be an insurmountable problem given that

there is continual movement of monitors

within existing networks. Some commenters

suggested averaging approaches that included

the use of population weighting of monitored

data, and some supported the use of a public

health information system to allow

individuals residing in ‘‘hot spot’’ areas to

reduce their exposures to O3 concentrations

of concern.

In contrast, environmental associations,

public health professionals, most States, and

many individuals voiced strong concerns that

the use of spatially averaged data would

routinely allow individuals who live or work

in communities with consistently higher O3

levels than those occurring across the broader

urban area to be exposed to concentrations of

concern. Many of these commenters raised

the issue of environmental equity, expressing

the view that communities with consistently

higher O3 concentrations typically are

composed predominantly of individuals of

lower socioeconomic status, or are composed

of a predominantly minority population. The

EPA notes that this view is not consistent

with the air quality data discussed earlier in

this unit, in that O3 concentrations are

typically lower in urban centers than in

locations surrounding or downwind of urban

centers. Some commenters also raised

concerns about the complexity and burdens

associated with redesigning existing

monitoring networks.

Taking into account the comments

received, the Administrator does not find that

the issues of concern, as outlined in the

proposal and above, have been adequately

addressed in this review of the O3 standard.

In particular, while EPA strongly agrees with

the importance of public health advisories in

addition to adequately protective standards,

relying on the use of public health advisories

to provide information for at-risk populations

who may consistently be exposed to localized

O3 concentrations of concern is considered by

the Administrator to be an insufficient

approach to protecting public health with an

adequate margin of safety. Further, the

suggested use of population weighting of

monitored data may, in many cases, be

insufficiently sensitive to local O3 variations

to ensure adequate protection of these

populations from localized O3 concentrations.

Thus, the revised O3 standard will maintain

the current approach of using air quality data

from the monitor measuring the highest O3

concentrations in an area to determine

whether the standard is attained within an

area.

The EPA has also considered spatial

averaging in the context of the decision to

revise the PM NAAQS, in part, by adopting

a form of an annual standard for fine particles

(i.e., PM2.5) that allows for spatial averaging

within appropriate criteria. It is important to

note that different considerations apply in

these two cases. One principal difference is

the nature of the health effects evidence for

O3 and PM2.5. When considering averaging

approaches for O3, it should be recognized

that much of the human health effects

evidence supporting the O3 standard is based

on controlled human exposure studies that

relate individual O3 exposures directly to

responses in individuals, whereas the health

effects evidence supporting the PM2.5

standards is from epidemiological studies

relating community measures of PM2.5

concentrations to population-wide responses.

Thus, information available for determining

an appropriate level of a standard in these two

cases is predominantly individual-oriented in

the case of O3 and community-oriented in the

case of PM2.5. As a consequence, additional

research and exposure and risk assessments

beyond those available in this review would

be necessary to provide a basis for further
Federal Register / Vol. 62, No. 138 / Friday, July 18, 1997 / Prepublication 17

24 For a discussion of these programs, see the proposal.

25 Currently, a PSI value of 100 for O3 corresponds to

an ambient concentration of 0.12 ppm, averaged over 1

hour.

consideration of a spatially averaged standard

for O3. The EPA will continue to explore this

approach.

Another important difference between the

O3 and PM standards is that the suite of

annual and 24–hour PM2.5 standards permits

the use of the 24–hour PM2.5 standard, which

would not be spatially averaged, as a

backstop to control localized ‘‘hot spots,’’

whereas a single O3 standard does not allow

for such a dual approach. Also, EPA notes

that the existence of an established, extensive

O3 monitoring network would require

substantial redesigning and relocation of

monitors for the purpose of spatial averaging,

in contrast to the current absence of such a

network for PM2.5 which can be newly

designed to address community-oriented

monitoring from the outset.

As discussed in the proposal, the

Administrator recognizes that no standard

within the range of levels and forms

considered in this review, including the

selected standard, is risk free, due to the

continuum of risk likely posed by exposures

to ambient O3 potentially down to

background levels. Accordingly, consistent

with CASAC advice, the Administrator

solicited comment in the proposal on

elements of an enhanced public health

advisory system. The Administrator believes

that the information that could be made

available through such a public health

advisory system would be particularly useful

to extremely sensitive individuals in making

personal decisions about avoiding exposures

with the potential to cause transient adverse

effects on days when 8–hour average O3

concentrations are predicted to be at or near

the level of the standard. Approaches to

developing an enhanced system, and

comments received on such approaches, are

discussed in Unit II.C. of this preamble.

4. Final decision on the primary standard.

After carefully considering the information

presented in the Criteria Document and the

Staff Paper, the advice and recommendations

of CASAC, public comments received on the

proposal, and for the reasons discussed above,

the Administrator is replacing the existing 1–

hour, 0.12 ppm primary standard with a new

8–hour, 0.08 ppm primary standard. The new

8–hour standard will become effective

September 16, 1997.

The 8–hour, 0.08 ppm primary standard

will be met at an ambient air quality

monitoring site when the 3–year average of

the annual fourth-highest daily maximum 8–

hour average O3 concentration is less than or

equal to 0.08 ppm. Data handling conventions

are specified in a new Appendix I to 40 CFR

part 50 as discussed in Unit VI below.

In the proposal, EPA proposed that the

revocation of the existing 1–hour O3 standard

be delayed for certain purposes until EPA had

approved State Implementation Plans to

implement the new 8–hour O3 standard. EPA

had proposed continuing the applicability of

the 1-hour standard in this way in order to

facilitate continuity in public health

protection during the transition to a new

standard. (See Memorandum from John S.

Seitz to Mary D. Nichols, November 20,

1996; Docket No. A–95–58, item II–B–3.)

Also, at the time of the proposal of the new

O3 standard, EPA had proposed an

interpretation of the Act in the proposed

Interim Implementation Policy (61 FR 65764,

December 13, 1996) under which the

provisions of subpart 2 of part D of Title I

of the Act would not apply to existing O3

nonattainment areas once a new O3 standard

becomes effective.

In light of comments received regarding

the interpretation proposed in the Interim

Implementation Policy, EPA has reconsidered

that interpretation and now believes that the

Act should be interpreted such that the

provisions of subpart 2 continue to apply to

O3 nonattainment areas for purposes of

achieving attainment of the current 1–hour

standard. As a consequence, the provisions of

subpart 2, which govern implementation of

the 1–hour O3 standard in O3 nonattainment

areas, will continue to apply as a matter of

law for so long as an area is not attaining the

1–hour standard. Once an area attains that

standard, however, the purpose of the

provisions of subpart 2 will have been

achieved and those provisions will no longer

apply. However, the provisions of subpart 1

of part D of Title I of the Act would apply

to the implementation of the new 8–hour O3

standards.

To facilitate the implementation of those

provisions and to ensure a smooth transition

to the implementation of the new 8–hour

standard, the 1–hour standard should remain

applicable to areas that are not attaining the

1–hour standard. Therefore, the 1–hour

standard will remain applicable to an area

until EPA determines that it has attained the

1–hour standard, at which point the 1–hour

standard will no longer apply to that area.

C. Communication of Public Health

Information

Information on the public health

implications of ambient concentrations of

criteria pollutants is currently made available

primarily through two EPA programs. The

first program is designed to prevent ambient

pollutant concentrations from reaching the

significant harm level (i.e., an exposure level

that constitutes an imminent and substantial

endangerment to public health). The second

program is the Pollutant Standards Index

(PSI),24 which is a health advisory system.

The proposal focused on the potentially

expanded use of the PSI in regard to allowing

sensitive individuals to reduce their risk of

exposure. Currently, EPA and local officials

use the PSI as a public information tool to

advise the public about the general health

effects associated with different pollution

levels and to describe whatever precautionary

steps may need to be taken if air pollution

levels rise into the unhealthful range. By

notifying the public when a PSI value

exceeds 100 (which corresponds to the

NAAQS for each criteria pollutant)25, citizens

are given the opportunity to take appropriate

steps to avoid exposures of concern. This use

of the PSI could be expanded to provide more

specific health information for O3

concentrations close to the level of the

primary standard. Given the continuum of

risks associated with exposure to O3, this

information, while perhaps of interest to all

citizens, would be particularly useful to those

individuals who are extremely sensitive to

relatively low O3 concentrations. As an

example, the proposal mentioned the

possibility of expanding the PSI to include

two new descriptive categories in the Index,

one including concentrations within a range

somewhat below the level of the new primary

standard (with a possible descriptor of

‘‘moderately good’’), the other including

concentrations within a range somewhat

above the level of the standard (with a

possible descriptor of ‘‘moderately

unhealthful’’). Such an approach could better

reflect the increased understanding of health

effects associated with O3 exposure

developed during this review, and would be

consistent with the recommendation of a

number of CASAC panel members ‘‘that an

expanded air pollution warning system be

initiated so that sensitive individuals can take

appropriate ’exposure avoidance’ behavior’’

(Wolff, 1995b).

The proposal also discussed the use of

forecasting in combination with this expanded

use of the PSI. For a health advisory system

to be effective, citizens need to be notified

as early as possible to be able to avoid

exposures of concern. The notice indicated

that if the current 1–hour primary NAAQS

for O3 is replaced with an 8–hour standard,

there would clearly be increased value in

using forecasted O3 concentrations in

providing cautionary statements to the public.

Currently, when a health advisory indicates

that the 1–hour O3 PSI value of 100 has been

exceeded, citizens generally have time to

avoid exposures of concern because O3 levels

tend to remain elevated for several hours

during the day. With the new 8–hour

standard, however, this would likely not be

the case, since by the time a PSI value is

reported, the potential for prolonged

exposures of concern would likely have

passed for that day. Forecasting 8–hour

maximum O3 concentrations would facilitate

the risk-reduction function of the PSI by

giving citizens more time to limit or avoid

exposures of concern.

The EPA did not formally propose

revisions to the PSI in the proposal. Instead,

the Administrator requested comment, and
18 Federal Register / Vol. 62, No. 138 / Friday, July 18, 1997 / Prepublication

indicated that the Agency might propose

revisions to the PSI in conjunction with future

proposals associated with the implementation

of a revised NAAQS.

The EPA received a large number of

comments from a wide variety of commenters

on the usefulness of both an expanded health

advisory system and the forecasting of 8–hour

ambient O3 concentrations. Commenters

representing State and local agencies,

business and industry associations, as well as

environmental associations overwhelmingly

endorsed the use of an expanded public health

advisory system and many noted the

importance of forecasting 8–hour O3

concentrations in conjunction with the PSI,

while recognizing a number of issues that

would need to be addressed.

Comments from environmental

associations endorsed increasing the

specificity of warnings with regard to the

health effects that could occur as a result of

exposure, and noted that citizens are capable

of dealing with complex information. These

commenters also took exception to describing

O3 levels around the level of the standard that

have been shown to result in decreased lung

function and increased respiratory symptoms,

as ‘‘moderately good,’’ stating that this

descriptor is misleading and might not be

heeded by people who could, if they fully

understood the nature of the health risk, take

action to minimize their exposures. Other

commenters felt that the descriptors

‘‘moderately good’’ and ‘‘moderately

unhealthful’’ were unnecessarily confusing.

Industry commenters were uniformly

supportive of enhancing the risk reduction

function of the PSI by issuing health

advisories with specific health information at

and above the level of the standard. Several

industry commenters also recommended that

the function of the PSI be combined with the

function of an O3 action system, which would

recommend voluntary actions to reduce

ambient O3 concentrations when the level of

the standard is forecasted to be exceeded.

This would result in a system that not only

could provide accurate health effects

information specific to the members of the

population likely to experience effects, but

also could help prevent exposures to levels of

O3 at or above the level of the standard.

Commenters from State and local air

pollution control authorities strongly endorsed

expanding the use of the PSI and the

utilization of forecasted 8–hour O3

concentrations. These commenters

encouraged EPA to develop any such

approaches to revise the PSI in consultation

with State and local agencies, specifically in

the areas of sharing real-time O3 monitoring

data among neighboring States, risk

communication with the public, and

coordination of a national program. States

also expressed the need for flexibility in the

implementation of such approaches and for

guidance from EPA on technical aspects such

as forecasting.

The EPA will take all of these comments

into consideration when developing a

proposal to revise the PSI (40 CFR 58.50) for

O3. The EPA plans to propose these

revisions, as well as revisions to the

significant harm level program (40 CFR

51.16), at a later date.

III. Rationale for the Secondary O3

Standard

A. Introduction

1. Overview. This notice presents the

Administrator’s final decision regarding the

need to revise the current secondary O3

standard, and more specifically, to replace the

existing 1–hour, 0.12 ppm O3 secondary

NAAQS with a secondary standard equal in

form, level, and averaging time to the new 8–

hour, 0.08 ppm primary standard. This

decision is based on a thorough review of the

scientific information on vegetation effects

associated with exposure to ambient levels of

O3 as assessed in the Criteria Document. This

decision also takes into account:

(1) Staff Paper assessments of the most

policy-relevant information in the Criteria

Document and staff analyses of air quality,

vegetation exposure and risk, and economic

values presented in the Staff Paper, upon

which staff recommendations for a new O3

secondary standard were based.

(2) Consideration of the degree of

protection to vegetation potentially afforded

by the new 8–hour, 0.08 ppm primary

standard compared to alternative secondary

standards.

(3) CASAC advice and recommendations

as reflected in discussion of drafts of the

Criteria Document and Staff Paper at public

meetings, in separate written comments, and

in CASAC’s letter to the Administrator

(Wolff, 1996).

(4) Public comments received during

development of these documents either in

conjunction with CASAC meetings or

separately.

(5) Extensive public comments received on

the proposed decision regarding the

secondary O3 standard.

After taking this information into account and

for the reasons discussed in this Unit, the

Administrator concludes that revisions to the

current secondary standard are appropriate at

this time to provide increased protection

against adverse effects to public welfare, and

that it is appropriate to set the new secondary

standard identical to the new primary

standard.

This review has focused on O3 effects on

vegetation since these public welfare effects

are of most concern at O3 concentrations

typically occurring in the United States. By

affecting commercial crops and natural

vegetation, O3 may also indirectly affect

natural ecosystem components such as soils,

water, animals, and wildlife. Based on the

scientific literature assessed in the Criteria

Document, the Administrator believes it is

reasonable to conclude that a secondary

standard that protects the public welfare

categories of commercial crops and natural

vegetation from known or anticipated adverse

effects would also afford increased protection

to these other related public welfare

categories. With regard to O3 effects on

manmade materials and deterioration of

property, the scientific literature assessed in

the Criteria Document contains little new

information since the last review.

Accordingly, EPA again concludes for the

reasons set forth in 1993 (58 FR 13008,

March 9, 1993) that O3-related effects on

materials do not provide a basis for selecting

an averaging time and level for a secondary

standard. In addition, since the effects of O3

on personal comfort and well-being (e.g.,

nose and throat irritation, chest discomfort,

and cough) have been accounted for in the

review of the primary standard, these effects

are not considered in this review of the

secondary standard.

The vegetation effects information,

exposure and risk assessment, and economic

analyses presented in the Staff Paper and

proposal are briefly outlined in the remainder

of Unit III.A. of this preamble. The key issues

raised in public comments with regard to:

Whether revisions to the current secondary

standard are requisite to protect public

welfare from adverse effects and the specific

elements of a revised secondary standard are

discussed in Unit III.B. along with the

Administrator’s rationale for concluding that

it is appropriate to revise the current

secondary standard to be identical to the new

primary standard.

2. Vegetation effects information.

Exposures to O3 have been associated

quantitatively and qualitatively with a wide

range of vegetation effects such as visible

foliar injury, growth reductions and yield loss

in annual crops, growth reductions in tree

seedlings and mature trees, and effects that

can have impacts at the forest stand and

ecosystem level. Summarized below are key

findings for each of the above effects

categories that are discussed in more detail in

the Criteria Document, Staff Paper, and

proposal.

Visible foliar injury can represent a direct

loss of the intended use of the plant, ranging

from reduced yield and/or marketability for

some agricultural species to impairment of

the aesthetic value of urban ornamental

species. On a larger scale, foliar injury is

occurring on native vegetation in national

parks, forests, and wilderness areas, and may

be degrading the aesthetic quality of the

natural landscape, a resource important to

public welfare.

Ozone can interfere with carbon gain

(photosynthesis) and allocation of carbon

with or without the presence of visible foliar

injury. As a result of decreased carbohydrate

availability, remaining carbohydrates may be

allocated to sites of injured tissue or

employed in other repair or compensatory
Federal Register / Vol. 62, No. 138 / Friday, July 18, 1997 / Prepublication 19

26 The SUM06 exposure index cumulates over a given

time period and diurnal window all hourly O3

concentrations greater than or equal to 0.06 ppm.

processes, thus reducing the carbohydrates

available for plant growth and/or yield.

Growth and yield effects of O3 have been

well documented for numerous species,

including commodity crops, fruits and

vegetables, and seedlings of both coniferous

and deciduous tree species.

Due to a number of differences between

seedlings and mature trees in their responses

to O3 exposures, data from tree seedling

studies cannot, at this time, be extrapolated

to quantify responses to O3 in mature trees.

However, long-term observational studies of

mature trees have shown growth reductions in

the presence of elevated O3 concentrations.

Where these growth reductions are not

attributed to O3 alone, due to the presence of

many other environmental variables, it has

been reported that O3 is a significant

contributor that potentially exacerbates the

effects of other environmental stresses (e.g.,

pests). In addition, studies show that

sensitivity to O3 with respect to visible foliar

injury and growth and yield effects can vary

significantly within and between species for

both crops and trees.

Growth reductions can indicate that plant

vigor is being compromised such that the

plant can no longer compete effectively for

essential nutrients, water, light, and space.

When many O3-sensitive individuals make up

a population, the whole population may be

affected. Changes occurring within sensitive

populations, or stands, if they are severe

enough, ultimately can change community

and ecosystem structure. Structural changes

that alter the ecosystem functions of energy

flow and nutrient cycling can alter ecosystem

succession.

In the CASAC closure letter, all CASAC

panel members agreed that ‘‘damage is

occurring to vegetation and natural resources

at concentrations below the present 1–hour

national ambient air quality standard

(NAAQS) of 0.12 ppm,’’ and the vegetation

experts agreed that ‘‘plants appear to be more

sensitive to O3 than humans’’ (Wolff, 1996).

Further, the CASAC panel agreed ‘‘that a

secondary NAAQS, more stringent than the

present primary standard, was necessary to

protect vegetation from O3’’ (Wolff, 1996).

The Administrator concurred in the proposal

with the unanimous view of CASAC that the

current standard of 0.12 ppm, 1–hour average,

does not provide adequate protection to

vegetation from the adverse effects of O3,

based on the following specific observations

that were taken from key studies and other

biological effects information reported in the

O3 Criteria Document and Staff Paper:

(1) O3 concentrations ≥ 0.10 ppm can be

phytotoxic to a large number of plant species,

and can produce acute foliar injury responses

and reduced crop yield and biomass

production.

(2) O3 concentrations within the range of

0.05 to 0.10 ppm have the potential over a

longer duration of creating chronic stress on

vegetation that can result in reduced plant

growth and yield, shifts in competitive

advantages in mixed populations, decreased

vigor leading to diminished resistance to pest

and pathogens, and injury from other

environmental stresses. Some sensitive

species can experience foliar injury and

growth and yield effects even when

concentrations never exceed 0.08 ppm.

The Administrator further concluded that

the available scientific information supports

the conclusion that a cumulative seasonal

exposure index, such as the proposed SUM06

index,26 is more biologically relevant than a

single event or mean index.

3. Vegetation exposure and risk analyses.

In reaching a judgment in the proposal as to

a standard requisite to protect crops and

vegetation against the adverse effects of O3,

the Administrator took into account several

additional considerations including the extent

of exposure of O3-sensitive species, potential

risks of adverse effects to such species, and

monetized and nonmonetized categories of

increased vegetation protection associated

with reductions in O3 exposures. In so doing,

the Administrator recognized that markedly

improved air quality, and thus significant

reductions in O3 exposures would result from

attainment of the alternative 0.08 ppm, 8–

hour primary standards within the range of 1-

and 5-expected exceedance forms. Thus, as a

matter of policy, the Agency estimated the

increased protection from O3-related effects

on vegetation associated with attainment of

alternative 8–hour, 0.08 ppm primary

standards, and then considered the

incremental protection associated with

attainment of a seasonal secondary standard.

The ability of EPA to characterize O3 air

quality in rural and remote sites was limited

by the available rural O3 monitoring network.

Therefore, EPA conducted national analyses

using geographic information systems (GIS)

and data from existing air quality monitoring

sites to estimate seasonal O3 air quality for

the year 1990, in terms of the 3–month, 12–

hour, SUM06 exposure index. The year 1990

was selected because it was a fairly typical

year in terms of O3 air quality. The estimated

1990 air quality was then used as a baseline

from which to roll back O3 concentrations to

project O3 air quality that would be expected

to occur when alternative standards were just

attained.

The regulatory scenarios examined

included just attaining the existing 1–hour

secondary standard, alternative 8–hour

primary standards in the range of 0.07 to 0.09

ppm, including standards set at 0.08 ppm,

with 1- and 5-expected-exceedance forms,

and a range of seasonal standards using the

SUM06 index, based on a single year of data.

Estimates of air quality associated with

alternative 8–hour primary standards with 1-

and 5-expected-exceedance forms were used

to roughly bound air quality estimates for 8–

hour standards with concentration-based

forms ranging from the annual second- to the

fifth-highest concentration-based forms, and

including the proposed third-highest

concentration-based form.

By comparing these projected air quality

scenarios for alternative standards with maps

showing the growing regions for O3-sensitive

crops and tree seedling species, estimates of

exposures of concern and risks of adverse

effects for various species were developed for

alternative standards. Taking into account the

body of information concerning O3 effects on

vegetation, as presented in the Criteria

Document and Staff Paper and summarized in

the proposal, EPA considered both

quantifiable risks (when exposure-response

functions were available) as well as those

risks that could only be qualitatively

characterized.

The Administrator concluded in the

proposal that attaining a 8–hour, 0.08 ppm

primary standard within the range of forms

under consideration would provide

substantially improved protection of

vegetation from seasonal O3 exposures of

concern. The Administrator recognized,

however, that some areas may continue to

have elevated seasonal exposures, including

forested park lands and other natural areas

and Class I areas that are federally mandated

to preserve certain air quality related values.

In its discussions of uncertainties,

described in the proposal, the CASAC Panel

members expressed concerns about the use of

the GIS methodology to project national O3

air quality and exposures of O3-sensitive

species. As is the case with other analytic

methods (e.g., Krieging, inverse distance

weighting), the GIS methodology contains

numerous assumptions and uncertainties, and

incorporates various databases each with their

own set of uncertainties. As noted in the Staff

Paper and proposal, the EPA and CASAC

recognized that the uncertainties in exposure

and risk estimates derived from the GIS

methodology are large and unquantifiable, but

that the method provides useful information

that is appropriate to consider in comparing

the relative protection afforded by alternative

standards. Further, EPA noted in the Staff

Paper and proposal that the GIS-generated air

quality estimates compare reasonably well

with the limited available O3 monitoring data.

In taking the results from these analyses into

account, the Administrator recognized these

inherent limitations and primarily considered

the comparative results in assessing the

degree of protection afforded by alternative

standards.

While the analyses discussed above

indicated that an 8–hour, 0.08 ppm primary

standard within the range of alternatives

considered, would provide increased

protection for commercial and natural

vegetation, it remained uncertain as to the

extent to which air quality improvements

designed to reduce 8–hour O3 concentrations
20 Federal Register / Vol. 62, No. 138 / Friday, July 18, 1997 / Prepublication

27 Including 15 species, representing approximately 75%

of the U.S. sales of agricultural crops, evaluated in the

National Crop Loss Assessment Network (NCLAN)

studies undertaken in the early to mid-1980’s, which

provide the largest, most uniform database on the effects

of O3 on agricultural crop species.

28 These fruit and vegetable crops constitute

approximately 50% of the Nation’s fruits and vegetable

markets.

would reduce O3 exposures measured by a

seasonal SUM06 index. To further explore

this question, EPA also examined the design

values for alternative 8–hour, 0.08 ppm

standards, within the range of 1- and 5-

expected exceedances, averaged over 3 years,

and a 3–month, 12–hour SUM06 standard for

581 counties (those having sufficient

monitoring data for the period 1991 – 1993).

As discussed in the Staff Paper and proposal,

this analysis revealed that almost all areas

that are within or above a SUM06 range of

25–38 ppm–hours would also have an 8–hour

daily maximum design value of greater than

0.08 ppm. Thus, in those areas in which air

quality monitoring is being conducted, areas

that would likely be of most concern for

effects on vegetation, as measured by the

SUM06 exposure index, would also be

addressed by an 8–hour primary standard set

at a 0.08 ppm level.

4. Monetized estimates of vegetation

protection. As discussed in section VII.F. of

the Staff Paper and in the proposal, EPA

developed monetized estimates of increased

protection associated with several alternative

standards for economically important

commodity crops nation-wide27 and for fruit

and vegetable crops in California.28 These

analyses were based on the GIS-generated

projections of O3 air quality for various

alternative standards. Monetized estimates of

increased protection could not be developed

for other important categories of vegetation,

such as urban ornamentals, Class I areas, and

commercial and other forests because of a

lack of available concentration-response

functions and appropriate economic valuation

models. The available data suggested,

however, that reductions in ambient O3

concentrations resulting from attainment of

alternative standards would confer increased

protection for these categories as well by

reducing biomass loss, protecting functional,

aesthetic, and existing values, and by

preserving biodiversity and native habitats.

As summarized in the proposal, most of the

monetized estimates of increased protection

would accrue from attainment of an 8–hour,

0.08 ppm primary standard, with a smaller

incremental improvement obtained by the

addition of a seasonal secondary standard. In

contrast, the incremental protection obtained

from the addition of a seasonal secondary

standard would be considerably more

significant when compared to an alternative

8–hour primary standard at a level of 0.09

ppm.

B. Need for Revision of the Current

Secondary Standard

Based on the above considerations and the

rationale in the proposal, the Administrator

proposed and sought comment on two

alternative standards, either of which in her

judgment would be appropriate to protect

public welfare from known or anticipated

adverse effects given the available scientific

knowledge. The two alternatives were setting

the revised secondary standard identical to the

proposed 8–hour, 0.08 ppm primary standard,

or establishing a 3–month, 12–hour, SUM06

seasonal secondary standard at the level of 25

ppm–hours. The Administrator recognized

that it would be a reasonable policy choice

to set the revised secondary standard identical

to an 0.08, 8–hour ppm primary standard, but

also recognized that a SUM06 seasonal

standard is more biologically relevant and,

therefore, was also appropriate to consider.

In reaching her final decision on a revised

secondary standard, the Administrator has

taken into account several factors. First, she

again concludes based on information

presented in the Criteria Document and Staff

Paper, and summarized in the proposal and

in this preamble, that the existing secondary

standard does not provide adequate protection

for vegetation against the adverse welfare

effects of O3.

Second, she has considered the comments

made by the CASAC Panel members during

their reviews of these documents and in

CASAC’s closure letter, ‘‘that a secondary

NAAQS, more stringent than the present

primary standard, was necessary to protect

vegetation from O3’’ (Wolff, 1996). These

statements provide strong support to the

Administrator’s judgment that the body of

scientific evidence on O3 effects on

vegetation provides sufficient and compelling

evidence that the current secondary standard

is not adequately protective and should be

revised.

Third, the Administrator recognizes that

significant uncertainties remain with respect

to exposure dynamics, air quality

relationships, and estimates of increased

vegetation protection which are important

factors in selecting an appropriate secondary

standard, as described more fully in the

Criteria Document, Staff Paper and proposal.

The CASAC closure letter highlighted key

uncertainties that hampered the Panel’s ability

to make any recommendations as to an

appropriate form or level for a secondary

standard that would be protective against

adverse effects on vegetation from exposure

to ambient levels of O3. The Panel stated that

‘‘agreement on the level and form of such a

standard is still elusive’’ and ‘‘***there

remain important limitations to our

understanding of the extent of the response

of vegetation to O3 under field conditions’’

(Wolff, 1996). These uncertainties are largely

a result of inadequate rural and remote O3 air

quality data that would allow with greater

certainty determination of the relationships

between O3-related effects being observed in

the field and ambient O3 exposures.

Nevertheless, the alternative standards

proposed by the Administrator are consistent

with the range of views expressed by the

CASAC panel members, and CASAC

recognized that choosing between the two

alternatives is a policy decision that cannot

be based solely on science (Wolff, 1996).

Fourth, the Administrator recognized that

just attaining the 8–hour, 0.08 ppm, 1- and

5-expected exceedance alternatives results in

markedly improved air quality when

compared to just attaining the existing

secondary standard, with only slight

improvements associated with going from a

5- to 1-expected exceedance form.

Fifth, the Administrator has carefully

considered the information and views

provided in the public comments. Though

these comments yielded no new scientific

information relevant to choosing between the

two alternative proposed standards, many

commenters repeated the CASAC’s concerns

over the significant uncertainties remaining in

the database. Many of these commenters

expressed the view that EPA should wait to

set a seasonal secondary standard until better

rural air quality data were available, which

would allow for better characterization of the

magnitude of improvements in public welfare

protection likely to be afforded by such a

standard compared to a revised primary

standard.

In sharp contrast, other commenters

expressed the view that the available data

were sufficient to demonstrate a need to set

a seasonal secondary standard to protect

vegetation against the adverse effects of O3,

and many such commenters recommended the

proposed SUM06 form for such a standard.

A significant number of these commenters

also made recommendations on the

appropriate level for a seasonal SUM06,

generally recommending levels lower than the

proposed 25 ppm-hours, ranging from 8 to 20

ppm–hours. The key source frequently cited

in support of these recommendations is an

article by Heck and Cowling (1997) which

summarizes the outcome of a consensusbuilding workshop sponsored by the Southern

Oxidant Study group on the secondary

standard held in January 1996.

This workshop was attended by 16

scientists with backgrounds in agricultural,

managed forest, natural systems, and air

quality, all of whom are leaders in their fields

and whose research formed the basis of much

of the research examined in the Criteria

Document. These scientists expressed their

judgements on what standard level(s) would

provide vegetation with adequate protection

from O3-related adverse effects.

Though the report identified no new data

in support of the scientists’ recommendations,

the Administrator believes that the report

lends important support to the view that the

current secondary standard is not adequately
Federal Register / Vol. 62, No. 138 / Friday, July 18, 1997 / Prepublication 21

protective of vegetation. Further, the

Administrator believes that the report

foreshadows the direction of future scientific

research in this area, the results of which

could be important in future reviews of the

O3 secondary standard.

As the results of such research become

available, EPA will be in a better position to

characterize rural air quality and the

improvements in vegetation protection that

would result from a seasonal secondary

standard, and to select a standard level that

would provide adequate protection for

vegetation. However, given the present limits

of the scientific evidence of O3-related effects

and of rural air quality data, as discussed in

the Criteria Document, Staff Paper, the

proposal, and by CASAC, the Administrator

has decided that it is not appropriate to move

forward with a seasonal secondary standard

at this time for the reasons described below.

In coming to this conclusion, the

Administrator specifically considered the

significant improvements in public welfare

protection that are expected to be afforded by

the new 8–hour primary standard, as well as

the value of obtaining additional information

to better characterize O3-related effects on

vegetation under field conditions.

C. Final Decision on the Secondary Standard

Based on the scientific evidence, CASAC

advice and recommendations, comments

received on the proposal, and the

considerations summarized above, the

Administrator is replacing the current

secondary O3 standard with an 8–hour

standard, set at a level of 0.08 ppm, identical

in all respects to the new primary standard.

The Administrator judges that this standard

will provide substantially improved protection

for vegetation from O3-related adverse effects

as compared to that provided by the current

1–hour, 0.12 ppm secondary standard, while

allowing time for additional research and the

development of a more complete rural

monitoring network and air quality database

from which to evaluate the elements of an

appropriate seasonal secondary standard.

The decision not to set a seasonal

secondary standard at this time is based in

large part on the Administrator’s recognition

that the exposure, risk, and monetized

valuation analyses presented in the proposal

contain substantial uncertainties, resulting in

only rough estimates of the increased public

welfare protection likely to be afforded by

each of the proposed alternative standards.

These uncertainties were discussed in the

proposal and the Staff Paper and were noted

by CASAC (Wolff, 1996). In light of these

uncertainties, the Administrator has decided it

is not appropriate at this time to establish a

new separate seasonal secondary standard

given the potentially small incremental degree

of public welfare protection that such a

standard may afford. Instead, the

Administrator finds it a reasonable policy

choice to set a new secondary standard

identical to the new primary standard, while

focusing additional research on key areas for

consideration in the next review of the O3

criteria and standards.

Continued research on the effects of O3 on

vegetation under field conditions and on

better characterizing the relationship between

O3 exposure dynamics and plant response

will be important in the next review because:

(1) The available biological database

highlights the importance of cumulative,

seasonal exposures as a primary determinant

of plant responses.

(2) The association between daily

maximum 8–hour O3 concentrations and plant

responses has not been specifically examined

in field tests.

(3) The impacts of attaining an 8–hour,

0.08 ppm primary standard in upwind urban

areas on rural air quality distributions cannot

currently be characterized with confidence

due to limited monitoring data and air quality

modeling in rural and remote areas.

Setting the secondary standard equal to the

primary standard will allow EPA the

opportunity to evaluate more specifically the

improvement in rural air quality and in O3-

related vegetation effects resulting from

measures designed to attain the new primary

standard. This information in turn will allow

for better evaluation of the incremental need

for a separate seasonal secondary standard in

the next review of the O3 criteria and

standards.

In the proposal, the Administrator solicited

comment on the appropriate spatial scale of

an expanded rural monitoring network.

Relatively few comments were received

regarding an expanded rural monitoring

network, but those who did submit comments

were generally in favor of an expanded

network to allow for improved modelling of

long-range transport of O3 and its precursors

and for better characterization of O3 air

quality in rural and remote areas. Those

comments will serve to inform EPA’s

development of revised air quality

surveillance requirements (40 CFR part 58)

that will be proposed at a later date.

With respect to the proposed seasonal

secondary standard only, the proposal sought

comment on whether O3 concentrations from

several monitors should be spatially

integrated when determining compliance with

the standard. Only a few comments were

received, with some supporting and some

opposing spatial integration of O3

concentrations from several monitors.

In view of the Administrator’s decision to

replace the current secondary standard with a

secondary standard which is identical in form,

level, and averaging time to the new 8–hour,

0.08 ppm primary standard, rather than with

a seasonal standard, EPA is not adopting the

use of spatial averaging for the new

secondary standard.

To decrease some of the uncertainties

discussed above and to remedy the lack of air

quality data in rural and remote areas of

commercial or ecological importance for

vegetation, the Administrator reiterates her

intention, expressed in the proposal, to

expand the rural O3 monitoring network. The

EPA will propose revised O3 air quality

surveillance requirements (40 CFR part 58) at

a later date. The EPA is exploring

opportunities to work with other Federal

agencies to develop a coordinated and longterm rural monitoring network.

IV. Other Issues

Several commenters raised key legal and

procedural issues that are discussed below.

These include: (1) Whether EPA must give

consideration to costs and similar factors in

setting NAAQS; (2) whether EPA erred in its

selection of a methodology for determining

the level of a NAAQS that protects public

health with an adequate margin of safety; (3)

whether EPA committed a procedural error

by not extending the comment period; and (4)

whether the 1990 amendments to the Act

preclude EPA from revising the O3 NAAQS

to establish a new 8–hour standard.

Responses to other legal and procedural

issues are included in the Response-toComments Document.

A. Cost Considerations

For more than a quarter of a century, EPA

has interpreted section 109 of the Act as

precluding consideration of the economic

costs or technical feasibility of implementing

NAAQS in setting them. As indicated in the

proposal, a number of judicial decisions have

confirmed this interpretation. Natural

Resources Defense Council v. Administrator,

902 F.2d 962, 972–73 (D.C. Cir. 1990)(PM

NAAQS)(‘‘PM10’’), vacated, in part,

dismissed, 921 F.2d 326 (D.C. Cir.), certs.

dismissed, 498 U.S. 1075, and cert. denied,

498 U.S. 1082 (1991); Natural Resources

Defense Council v. EPA, 824 F.2d 1146,

1157–59 (D.C. Cir. 1987)(en banc)(CAA

section 112 standards for vinyl

chloride)(‘‘Vinyl Chloride’’); American

Petroleum Institute v. Costle, 665 F.2d 1176,

1185–86 (D.C. Cir. 1981)(ozone

NAAQS)(‘‘Ozone’’), cert. denied, 455 U.S.

1034 (1982); Lead Industries Ass’n v. EPA,

647 F.2d 1130, 1148–51 (D.C. Cir.)(lead

NAAQS)(‘‘Lead Industries’’), cert. denied,

449 U.S. 1042 (1980).

Some commenters have argued that costs

and similar factors should, nonetheless, be

considered, both in this rulemaking and in the

rulemaking on proposed revisions to the

NAAQS for particulate matter. Although

most of the commenters’ arguments are

inconsistent with the judicial decisions cited

above, several commenters have argued that

those decisions are not dispositive. For

reasons discussed below and in the Responseto-Comments Document, EPA disagrees with

these comments and maintains its

longstanding interpretation of the Act as

precluding consideration of costs and similar

factors in setting NAAQS.
22 Federal Register / Vol. 62, No. 138 / Friday, July 18, 1997 / Prepublication

29 36 FR 8186, Apr. 30, 1971. EPA has maintained this

interpretation consistently since then.

30 That consideration of such factors was not intended

in NAAQS decisions is also supported by section

109(a)(1). For pollutants for which air quality criteria had

been issued prior to the 1970 amendments, that provision

required EPA to propose NAAQS within 30 days after

enactment and to take final action 90 days later. The

criteria issued previously did not include information on

costs and similar factors, and it would have been difficult

if not impossible for EPA to supplement them in time to

include meaningful consideration of such factors in

NAAQS proposed 30 days after enactment.

31 See, e.g., sections 110(e)(1), 111(a)(1), 231(b) (1970

Act); see also, e.g., sections 113(d)(4)(C)(ii), 125(a)(3),

202(a)(3)(C), 317 (1977 Act).

32 Union Electric Co. v. EPA, 427 U.S. 246, 257–58

(1976).

33 The Senate report on the 1970 amendments stated:

‘‘In the Committee discussions, considerable concern was

expressed regarding the use of the concept of technical

feasibility as the basis of ambient air standards. The

Committee determined that (1) the health of people is more

important than the question of whether the early

achievement of ambient air quality standards protective of

health is technically feasible; and, (2) the growth of

pollution load in many areas, even with application of

available technology, would still be deleterious to public

health.’’

‘‘Therefore, the Committee determined that existing

sources of pollutants either should meet the standard of

the law or be closed down ***.’’

S. Rep. No. 91–1196, at 2–3 (1970).

34 These limitations would, of course, make little sense

if such factors could be considered in setting the NAAQS

themselves.

35 Such requirements ‘‘ ‘are expressly designed to force

regulated sources to develop pollution control devices that

might at the time appear to be economically or

technologically infeasible.’ ’’ Id. (quoting Union Electric

Co. v. EPA, 427 U.S. at 257).

36 In the PM10 case, for example, the Court considered

an argument that EPA should have considered potential

health consequences of unemployment that might result

from revision of the primary NAAQS for PM:

‘‘This claim is entirely without merit. In three previous

cases, this court has emphatically stated that section 109

does not permit EPA to consider such costs in

promulgating national ambient air quality standards ***.

It is only health effects relating to pollutants in the air

that EPA may consider . *** Consideration of costs

associated with alleged health risks from unemployment

would be flatly inconsistent with the statute, legislative

history and case law on this point.’’

902 F.2d at 973 (emphasis in original; citations omitted).

1. Background. Given the nature of the

points raised, a brief review of the issue

seems useful before addressing the comments.

The requirement that EPA establish national

ambient air quality standards for certain

pollutants, to be implemented by the States,

was enacted in 1970 as part of a set of

comprehensive amendments that established

the basic framework for Federal, State, and

local air pollution control. When EPA

promulgated the original NAAQS in 1971, its

first Administrator, William D. Ruckelshaus,

concluded that costs and similar factors could

not be considered in that decision.29 This

conclusion was not challenged in litigation on

the original NAAQS. It has been confirmed

since then, however, by every judicial

decision that has considered the issue.

As discussed below, EPA’s interpretation

rests primarily on the language, structure, and

legislative history of the statutory scheme

adopted in 1970. It is also supported by the

judicial decisions cited above, as well as by

legislative developments since 1970 that

reaffirm Congress’ original approach to the

issue.

Without cataloguing all relevant aspects of

the 1970 amendments and their legislative

history, several basic points should be noted.

Under section 109(b) of the Act, NAAQS are

to be ‘‘based on’’ the air quality criteria

issued under section 108. Under section

108(a)(2), the kind of information EPA is

required to include in criteria documents is

limited to information about health and

welfare effects ‘‘which may be expected from

the presence of [a] pollutant in the ambient

air ***.’’ There is no mention of the costs

or difficulty of implementing the NAAQS,

nor of ‘‘effects’’ that might result from

implementing the NAAQS (as opposed to

effects of pollution in the air).30 By contrast,

Congress explicitly provided for

consideration of costs and similar factors in

decisions under other sections of the Act.31

Moreover, States were permitted to consider

economic and technological feasibility in

developing plans to implement the NAAQS

to the extent such consideration did not

interfere with meeting statutory deadlines for

attainment of the standards.32 Finally, the

legislative history indicated that Congress had

considered the issue and had deliberately

chosen to mandate NAAQS that would

protect health regardless of concerns about

feasibility.33

The first judicial decision on the issue

came in the Lead Industries case. An industry

petitioner argued that EPA should have

considered economic and technological

feasibility in allowing a ‘‘margin of safety’’

in setting primary standards for lead. Based

on a detailed review of the language,

structure, and legislative history of the

statutory scheme, the U.S. Court of Appeals

for the District of Columbia Circuit

concluded that:

This argument is totally without merit. [The

petitioner] is unable to point to anything in either

the language of the Act or its legislative history that

offers any support for its claim ***. To the

contrary, the statute and its legislative history make

clear that economic considerations play no part in

the promulgation of ambient air quality standards

under section 109.

647 F.2d at 1148.

The Court cited a number of reasons for

this conclusion. Id. at 1148–50. Among other

things, it noted the contrast between section

109(b) and other provisions in which

Congress had explicitly provided for

consideration of economic and technological

feasibility, as well as the requirement that

NAAQS be based on air quality criteria

defined without reference to such factors. Id.

at 1148–49 & n.37. The Court also noted that,

in developing plans to implement NAAQS,

States may consider economic and

technological feasibility only to the extent

that this does not interfere with meeting the

statutory deadlines for attainment of the

standards; and that EPA may not consider

such factors at all in deciding whether to

approve State implementation plans. Id. at

1149 n.37 (citing Union Electric Co. v. EPA,

427 U.S. 246, 257–58, 266 (1976)).34

As to the legislative history of the 1970

amendments, the Court observed that:

[T]he absence of any provision requiring

consideration of these factors was no accident; it

was the result of a deliberate decision by Congress

to subordinate such concerns to the achievement of

health goals.

Id. at 1149. Citing several leading Supreme

Court decisions, as well as the Senate report

quoted above, the Court noted that Congress

had intended a drastic change in approach

toward the control of air pollution in the 1970

amendments and was well aware that sections

108–110 imposed requirements of a

‘‘technology-forcing’’ character. Id.35

The Court also noted that Congress had

already acted, in further amendments adopted

in 1977, to relieve some of the burdens

imposed by the 1970 amendments. Id. at 1150

n.38. Observing that Congress had, however,

declined to amend section 109(b) to provide

for consideration of costs and similar factors

as requested by industrial interests, id. n.39,

the Court concluded:

A policy choice such as this is one which only

Congress, not the courts and not EPA, can make.

Indeed, the debates on the [1970 amendments]

indicate that Congress was quite conscious of this

fact***.

*** [I]f there is a problem with the economic

or technological feasibility of the lead standards,

[the petitioner], or any other party affected by the

standards, must take its case to Congress, the only

institution with the authority to remedy the

problem.

Id. at 1150.

After the decision in Lead Industries,

Supreme Court review was sought on the

question whether costs and similar factors

could be considered in setting NAAQS,

among other issues. The Supreme Court

declined to review the decision. Lead

Industries Ass’n v. EPA, 449 U.S. 1042

(1980). The subsequent decisions in Ozone,

Vinyl Chloride, and PM10, cited above,

strongly reaffirmed the interpretation adopted

in Lead Industries.36 Supreme Court review

of the Ozone and PM10 decisions was sought

but denied. American Petroleum Institute v.

Gorsuch, 455 U.S. 1034 (1984); American

Iron and Steel Institute v. EPA, 498 U.S.

1082 (1991).

The Lead Industries opinion focused

largely, though not exclusively, on the 1970

amendments and their legislative history.

Perhaps as a result, it did not canvass all the

factors that, in fact, supported its conclusions

at the time. For example, when Congress

enacted major amendments to the Act in

1977, it was clearly aware that some areas of

the country had experienced difficulty in
Federal Register / Vol. 62, No. 138 / Friday, July 18, 1997 / Prepublication 23

37 See, e.g., H.R. Rep. No. 95–294, at 207–17 (l977).

38 See, e.g., id. at 110–12; id. at 43–51.

39 Section 109(d)(2)(C)(iv). Some commenters have

argued that this provision requires EPA to consider such

effects in setting NAAQS. From the language and structure

of section 109(d), however, it is clear that CASAC’s

responsibility to advise on these factors is separate from

its responsibility to review and recommend revision of air

quality criteria and NAAQS, and that the advice pertains

to the implementation of NAAQS rather than to setting

them. The legislative history confirms this view, indicating

that the advice was intended for the benefit of the States

and Congress. See H.R. Rep. No. 95–294, at 183 (1977).

40 The 1977 amendments also required EPA to prepare

economic impact assessments for specified actions but

limited the requirement to non-health-based standards,

excluding decisions under sections 109 and 112. Section

317; H.R. Rep. No. 95–294, at 51–52 (1977). In this and

other respects, Congress continued the approach it took in

the l970 amendments, making careful choices as to when

consideration of costs and similar factors would be

required and giving paramount priority to protection of

health. See 123 Cong. Rec. H8993 (daily ed. Aug. 4, 1977)

(Clean Air Conference Report (1977); Statement of Intent;

Clarification of Select Provisions), reprinted in 3 Senate

Committee on Environment and Public Works, 95th Cong.,

A Legislative History of the Clean Air Act Amendments

of 1977, at 319 (1978).

41 In the interim, the National Commission on Air

Quality had also submitted its report to Congress as

required by a provision of the 1977 amendments. Among

other things, the Commission recommended that the

statutory approach of requiring NAAQS to be set at levels

necessary to protect public health, without consideration

of economic factors, be continued without change.

National Commission on Air Quality, To Breathe Clean

Air 55 (1981).]

42 As the Administrator indicated in EPA’s proposal to

revise the PM standards:

‘‘[T]hat review has revealed a highly limited data

base—particularly where quantitative studies are

concerned—and a wide range of views among qualified

professionals about the exact pollution levels at which

health effects are likely to occur. The setting of an

‘adequate margin of safety’ below these levels calls for

a further judgment—in an area for which the scientific data

base is even more sparse and uncertain***.’’

‘‘[L]ong and expert review of public health issues has

to date revealed no scientific method of assessing exactly

what level of standards public health requires. The

scientific review indicates substantial uncertainties

concerning the health risks associated with lower levels of

particulate matter.’’

49 FR 10408, 10409, Mar. 20, l984.

43 Congress was clearly aware of the 1987 decision to

revise the PM NAAQS, which among other things

involved changing the indicator for particulate matter from

‘‘total suspended particulate’’ to PM10, because it enacted

special nonattainment provisions, as well as provisions for

PSD increments, applicable to PM10. Sections 188–190;

section 166(f). It was clearly aware of the Vinyl Chloride

decision because it amended section 112 in response to

that decision, essentially creating a new scheme for setting

emission standards for hazardous pollutants.

44 H.R. Rep. No. 101–490, pt. 1, at 145 (1990). See

also S. Rep. No. 101–228, at 5 (1989).

45 Additional responses to points raised by this

commenter and others are included, as appropriate, in the

Response-to-Comments document.

46 Several other commenters argue that the cited

decisions are not dispositive because they held only that

EPA is not required to consider costs and similar factors

in setting NAAQS. As discussed below in connection with

Chevron, however, the decisions clearly concluded that

Congress intended to preclude consideration of such

factors, and that EPA is not free to alter that congressional

choice. Although these conclusions are technically dicta,

nothing in the Court’s opinions suggests that it would have

interpreted section 109 differently had EPA claimed

authority to consider costs and similar factors in NAAQS

decisions. Indeed, the tone of the opinions argues to the

contrary. See, e.g., PM10, 902 F.2d at 973. Cf. Ethyl Corp.

v. EPA, 51 F.3d 1053 (D.C. Cir. 1995).

47 See, e.g., Lead Industries, 647 F.2d at 1146–47,

1153–56, 1160–61, 1167 n.106. In enacting the 1970

amendments, Congress was aware that there were gaps in

the scientific information available then as a basis for

establishing the original NAAQS. See, e.g., S. Rep. No.

91–1196, at 9–11 (1970). If anything, Congress had an

even greater understanding of the point when it enacted

that 1977 amendments without changing the substantive

criteria for setting NAAQS. See H.R. Rep. No. 95–294,

at 43–51, 181–82 (1977).

48 Lead Industries, 647 F.2d at 1147 (quoting Ethyl

Corp. v. EPA, 541 F.2d 1, 24–27 (D.C. Cir.) (en banc),

cert. denied, 426 U.S. 941 (1976)).

attempting to attain some of the NAAQS.37

It was also aware that there might be no

health-effects thresholds for the pollutants

involved, and that significant uncertainties are

inherent in setting health-based standards

under the Act.38 In response, Congress made

significant changes in the provisions for

implementation of the NAAQS, including

changes intended to ease the burdens of

attainment. It also amended sections 108 and

109 in several ways; for example, by

requiring periodic review and, if appropriate,

revision of air quality criteria and NAAQS

and by establishing a special scientific

advisory committee (CASAC) to advise EPA

on such reviews. Notably, Congress

recognized that implementation of NAAQS

could cause ‘‘adverse public health, welfare,

social, economic, or energy effects’’ and

charged CASAC with advising EPA on such

matters.39 Yet it made no changes in sections

109(b) or 108(a)(2); that is, in the substantive

criteria for setting or revising NAAQS. In

other words, Congress chose to address

economic and other difficulties associated

with attainment of the NAAQS by adjusting

the scheme for their implementation, rather

than by changing the instructions for setting

them.40

Congress enacted major amendments to the

Act again in 1990, well after the Lead

Industries and Ozone decisions that

interpreted section 109 as precluding

consideration of costs in NAAQS decisions.41

In doing so, Congress was clearly aware of

intervening developments such as EPA’s

decision to revise the PM NAAQS in 1987—

the result of an elaborate review in which the

Administrator strongly underscored the

scientific uncertainties involved42—and the

Vinyl Chloride case drawing a sharp

distinction between sections 109 and 112 with

regard to consideration of costs and similar

factors.43 Indeed, the legislative history of the

1990 amendments reflects Congress’

understanding that primary NAAQS were to

be based on protection of health ‘‘without

regard to the economic or technical feasibility

of attainment.’’44 Again, however, Congress

chose to respond to severe, widespread, and

persistent problems with attaining the

NAAQS by adjusting the scheme for their

implementation rather than by changing the

basis for setting them. See, e.g., sections 181–

192.

2. Public comments. As noted previously,

a number of commenters have argued that

costs and similar factors should be considered

in EPA’s final decisions on revision of both

the ozone and particulate NAAQS. Aside

from arguments that are simply inconsistent

with the judicial decisions cited above, some

of the commenters argue that those decisions

are not dispositive for a variety of reasons.

One commenter submitted a particularly

comprehensive version of this argument in

the rulemaking on proposed revisions to the

particulate NAAQS; the following discussion

focuses primarily on points raised by that

commenter, among others.45

As a general matter, the commenter

acknowledges that Congress intended to

preclude consideration of economic costs and

similar factors in setting NAAQS. The

commenter argues, however, that this is so

only when the scientific basis for NAAQS is

‘‘clear and compelling’’ or ‘‘unambiguous.’’

From that premise, the commenter advances

three key assertions:

(1) Where non-threshold pollutants are

involved and the health evidence is

ambiguous, section 109 must be interpreted to

allow consideration of all relevant factors,

including the practical consequences of

EPA’s decisions;

(2) To the extent the judicial decisions

cited above are read as precluding this, they

rest on a faulty analysis that pre-dates and

cannot survive scrutiny under Chevron,

U.S.A. v. Natural Resources Defense Council,

467 U.S. 837 (1984);46 and

(3) Because EPA has discretion to consider

costs and similar factors where the health

evidence is ambiguous, it must do so in light

of Executive Order 12866, 58 FR 51735, Oct.

4, 1993, and two recent statutes, the

Unfunded Mandate Reform Act of 1995, 2

U.S.C. secs. 1501–1571 (UMRA), and the

Small Business Regulatory Enforcement

Fairness Act of 1996, Pub. L. No. 104–121,

110 Stat. 857 (SBREFA), which in part

amended the Regulatory Flexibility Act, 5

U.S.C. secs. 601–808.

EPA believes all three assertions are

clearly incorrect. Regarding the first point, it

should be evident, both from previous

NAAQS decisions and from the court

opinions upholding them, that the scientific

basis for NAAQS decisions has never pointed

clearly and unambiguously to a single ‘‘right

answer.’’47 This is inherent in the statutory

scheme for the establishment and revision of

NAAQS, which in effect requires them to be

based on the ‘‘latest scientific knowledge’’ on

potential health and welfare effects of the

pollutant in question. See sections 109(b),

108(a)(2). Although advances in science

increase our understanding of such effects,

they also raise new questions. For this reason,

the key studies for any given decision on

revision of a NAAQS are, almost by

definition, ‘‘at the very ‘frontiers of scientific

knowledge.’ ’’48 That is, studies that call into

question the adequacy of a standard are

always those that go beyond previous
24 Federal Register / Vol. 62, No. 138 / Friday, July 18, 1997 / Prepublication

49 They may have methodological flaws, for example,

but nonetheless report effects that are of serious medical

significance; or they may be of impeccable quality but

involve effects of uncertain significance. Others may

involve results that are striking but hard to explain in terms

of previous knowledge, or results that seem plausible and

important but are not yet replicated by other studies.]

50 See, e.g., Lead Industries, 647 F.2d at 1155–56; H.R.

Rep. No. 94–295, at 43–51 (1977).

51 As previously discussed, the Administrator strongly

emphasized the uncertainties involved in that review. As

a result of the uncertainties, he proposed ‘‘relatively

broad’’ ranges for comment, though he focused on lower

levels within the ranges as providing greater margins of

safety against the health risks involved. See 49 FR 10408,

10409, Mar. 20, l984.

52 See, e.g., Lead Industries, 647 F.2d at 1152–53 &

n. 43, 1159–60; Ozone, 665 F.2d at 1185, 1187; PM10,

902 F.2d at 969–71, 972.

53 Indeed, the present decisions on the NAAQS for PM

and ozone are based on some of the best scientific

information the Agency has ever been able to rely on in

NAAQS decision-making. In particular, the science

underlying these decisions is much more extensive and of

much better quality than the science underlying the

existing NAAQS for PM and ozone.

54 In practice, analysis of this question is sometimes

referred to as a ‘‘Chevron step one’’ analysis.

55 See, e.g., 647 F.2d at 1148–51, 1152–53 & n.43,

1160–61.

56 See 647 F.2d at 1148–51. By contrast, the

commenter’s argument that Congress actually intended

EPA to consider such factors relies heavily on (1)

statements made in subsequent legislative history, most of

which were made in floor debate, that sought to justify

controversial amendments to establish a different program

than the NAAQS and did not involve any proposed

changes in section 109 or related provisions; and (2)

statements in early judicial decisions involving programs

under other statutory provisions. In context, EPA believes

these and other statements cited by the commenter are

consistent with and do not alter the conclusion that

Congress intended to preclude consideration of costs and

similar factors under section 109.

studies—by reporting new kinds of effects,

for example, or effects at lower

concentrations than those at which effects

have been reported previously.

As with pioneering work in other fields,

such studies may have a variety of strengths

and limitations.49 As a result, the validity and

implications of such studies may be both

uncertain and highly controversial. Given the

precautionary nature of section 109,50

however, it is precisely these kinds of studies

that the Administrator must grapple with

when advances in science suggest that

revision of a NAAQS is appropriate.

As a result, the EPA staff typically

recommends for consideration, and the

Administrator may propose for comment, a

range of alternatives based on what the

commenter would call ‘‘ambiguous’’ science.

In this respect, the current reviews of the

NAAQS for ozone and particulate matter are

not unusual and do not differ, for example,

from the review that led to adoption of the

PM10 NAAQS in 1987.51 Indeed, the

NAAQS that were upheld in the Lead

Industries, Ozone, and PM10 decisions were

all based on highly controversial health

evidence; the Lead Industries decision took

note of congressional statements recognizing

that there may be no thresholds for criteria

pollutants; and the Ozone and PM10 decisions

noted the Administrator’s findings that clear

thresholds could not be identified for ozone

and particulate matter, respectively.52 Thus,

the present decisions on revision of the

NAAQS for ozone and particulate matter

cannot be distinguished from those past

decisions in terms of the nature of the health

evidence or pollutants involved.53

Regarding the second of the commenter’s

key assertions, EPA believes it is clear that

the judicial decisions cited above were

correctly decided and continue to be good law

under Chevron. In Chevron, the Supreme

Court essentially reaffirmed the principle that

courts must defer to reasonable agency

interpretations of the statutes they administer

where Congress has delegated authority to

them to elucidate particular statutory

provisions. Where the intent of Congress on

an issue is clear, however, it must be given

effect by the agency and the courts. See 467

U.S. at 842–45. Thus, the first question on

review of an agency’s interpretation under

Chevron is ‘‘whether Congress has directly

spoken to the precise question at issue.’’ If

the court determines that it has not, the

remaining question for the court is ‘‘whether

the agency’s answer is based on a permissible

construction of the statute.’’ 467 U.S. at 842–

43 (footnote omitted). In determining whether

Congress ‘‘had an intention on the precise

question at issue,’’ a court employs

‘‘traditional tools of statutory construction.’’

Id. at 843 n.9.54

In essence, the commenter’s argument here

is that the Lead Industries decision did not

address whether Congress had ‘‘spoken

directly’’ to the precise issue posed by the

commenter; that is, whether section 109 must

be interpreted differently for NAAQS

decisions involving non-threshold pollutants

and ‘‘ambiguous’’ health evidence. The Lead

Industries opinion, which pre-dated Chevron,

did not pose the question in those terms. Its

focus, however, was clearly on what

Congress intended to be the basis for NAAQS

decisions, in a context the Court understood

to involve considerable uncertainty and

debate about the health evidence, as well as

the possibility that there was no threshold for

health effects of the pollutant.55 In short, the

health evidence was hardly ‘‘unambiguous,’’

yet the Court interpreted section 109 as

precluding consideration of costs and similar

factors even in allowing a margin of safety.

Nothing in the Lead Industries decision or in

the subsequent cases suggests in any way that

section 109 should be interpreted differently

based on the nature of the pollutants or health

evidence involved, and the Court’s findings

on congressional intent admit of no

exceptions:

[T]he statute and its legislative history make

clear that economic considerations play no part in

the promulgation of ambient air quality standards

under section 109.

647 F.2d at 1148.

Alternatively, the commenter argues that

the Lead Industries case decided the issue

incorrectly in light of the principles

announced subsequently in Chevron. In this

context, the commenter essentially argues that

the Lead Industries decision rested on two

factors that are no longer probative: (1) That

there was no indication that Congress meant

to allow consideration of costs in NAAQS

decisions, and (2) that Congress specifically

provided for such consideration in other

sections of the Act but not in section 109. On

the first point, the commenter argues that

EPA is free under Chevron to consider costs

and similar factors (by reinterpreting section

109) unless there is evidence that Congress

intended to restrict its discretion. As to the

second point, the commenter argues that

similar reasoning was rejected in Vinyl

Chloride.

In Vinyl Chloride, however, an en banc

decision that post-dated Chevron, the Court

essentially underscored the point that such

issues cannot be decided mechanically but

must turn, instead, on more analytical

attention to relevant indicia of congressional

intent. See, e.g., 824 F.2d at 1157 n.4; id. at

1157–63. With reference to NAAQS

decisions in particular, the Court concluded

that there were concrete indications of

congressional intent to preclude consideration

of costs and similar factors; for example, the

fact that section 108 ‘‘enumerate[s] specific

factors to consider and pointedly exclude[s]

feasibility.’’ 824 F.2d at 1159. In a later case,

moreover, the same Court held that EPA

could not consider certain factors, in

decisions under section 211(f)(4) of the Act,

for reasons exactly parallel to those that the

commenter criticizes in Lead Industries. See

Ethyl Corp. v. EPA, 51 F.3d 1053, 1057–63

(D.C. Cir. 1995).

Beyond this, the commenter’s

characterization of the Lead Industries

decision ignores or discounts much of the key

evidence cited by the Court, including the

language, structure, and legislative history of

the statutory scheme established in 1970, for

its conclusion that Congress intended to

preclude consideration of costs and similar

factors in NAAQS decisions.56 As indicated

above, the Vinyl Chloride and PM10 cases,

both of which post-dated Chevron, reached

the same conclusion.

Moreover, this series of decisions went far

beyond mere deference to an agency

interpretation. As indicated in the Vinyl

Chloride case, the Lead Industries court found

‘‘clear evidence’’ of congressional intent,

which was to limit the factors EPA may

consider under section 109. 824 F.2d 1159.

Consistent with Chevron, these findings were

based on traditional tools of statutory

construction. See id. at 1157–59; Lead

Industries, 647 F.2d at 1148–51. In terms of

the analytical framework later established by

Chevron, these were Chevron step one

findings, meaning that the statute spoke
Federal Register / Vol. 62, No. 138 / Friday, July 18, 1997 / Prepublication 25

57 The commenter argues that the post-Chevron cases

accepted the Lead Industries analysis uncritically rather

than re-examining it under Chevron. Clearly, this elevates

form over substance. It is true that neither case referred

to Chevron in discussing the point at issue. In Vinyl

Chloride, however, the Court retraced the steps in the Lead

Industries analysis in some detail, characterized some of

the key evidence reviewed in that analysis in terms going

beyond mere rote repetition (e.g., ‘‘a far clearer statement

than anything in the present case that Congress considered

the alternatives’’), and used Chevron-like language in

discussing the significance of that evidence; that is, that

it demonstrated congressional intention on the point at

issue. E.g., 824 F.2d at 1159. Given that the Vinyl

Chloride case was decided 3 years after Chevron, that it

was an en banc decision of the D.C. Circuit involving

interpretation of statutory language very similar to that in

Lead Industries, and that the Court cited Chevron twice

in analyzing the language and history of section 112, it

seems highly unlikely that the Court was unmindful of

Chevron principles in concluding that Congress intended

to preclude consideration of costs under section 109 but

not under section 112.

In the PM10 decision, the Court confirmed the sharp

distinction it had drawn, based on such evidence of

congressional intent, between sections 109 and 112 in

Vinyl Chloride. 902 F.2d at 972–73. Although discussion

of the point was brief and did not mention Chevron, the

industry petitioner raising the point had cited Chevron in

arguing that the Lead Industries interpretation was not

binding, and that EPA’s decision on the PM10 standards

should be reversed on the ground that it rested on a legal

position that EPA unjustifiably believed was mandated by

Congress. Reply Brief of the American Iron and Steel

Institute at 11 & n.10, Natural Resources Defense Council

v. Administrator, 902 F.2d 962 (D.C. Cir. 1990) (Nos. 87–

1438 et al.). Thus, Chevron issues were properly before

the Court and were brought squarely to its attention.

58 See also 52 FR 24854, July 1, 1987.

59 126 Cong. Rec. 21452, 21455 (1980) (Description of

Major Issues and Section-By-Section Analysis of

Substitute for S. 299).

directly to the issue and that the courts, as

well as the agency, must give effect to

Congress’ intent as so ascertained. See 467

U.S. at 842–43.57 Thus, absent a more recent

legislative enactment overriding that intent,

EPA has no discretion to alter its

longstanding interpretation that consideration

of costs and similar factors is precluded in

NAAQS decisions under section 109.58

As to the commenter’s third key assertion,

Executive Order 12866 (58 FR 51735,

October 4, 1993) UMRA sections 202 and

205, and the Regulatory Flexibility Act

(RFA), as amended by SBREFA, do not

conflict with this interpretation or require a

different result. Basically, the commenter

argues that the Executive Order, UMRA, and

the RFA (as amended by SBREFA) require

agencies to use cost (or similar factors) as a

decisional criterion in making regulatory

decisions, and that this modifies the Clean Air

Act’s directive that EPA is precluded from

considering costs when setting a NAAQS.

The commenter’s argument is flawed on a

number of grounds. First, UMRA and the

RFA (as amended by SBREFA) do not

conflict with section 109 because they do not

apply to this decision, as discussed in Unit

VIII of this preamble. Second, the Executive

Order and both statutes are quite clear that

they do not override the substantive

provisions in an authorizing statute. Third, the

commenter’s premise that UMRA and the

RFA (as amended by SBREFA) establish

substantive decisional criteria that agencies

are required to follow is wrong.

As a matter of law, the Executive Order

cannot (and does not purport to) override the

Clean Air Act. The Executive Order does not

conflict with section 109 because the

requirement that agencies ‘‘select approaches

that maximize net benefits’’ does not apply

if a ‘‘statute requires another regulatory

approach.’’ EO 12866, sec. (1)(a), 58 FR

51735, Oct. 4, 1993. More generally, the

Executive Order provides that agencies are to

adhere to its regulatory principles only ‘‘to

the extent permitted by law.’’ Id., sec. (1)(b).

UMRA sections 202 and 205 do not apply

to this decision, as discussed in Unit VII of

this preamble. Even when they do apply to

a regulatory action, they do not establish

decisional criteria that an agency must follow,

much less override decisional criteria

established in the statute authorizing the

regulatory action. UMRA does not require an

agency to select any particular alternative.

Rather, an agency can select an alternative

that is not the least costly, most cost-effective

or least burdensome if the agency explains

why, sec. 205(b)(1). Such an explanation is

not required if the least costly, most costeffective or least burdensome alternative

would have been ‘‘inconsistent with law,’’

sec. 205(b)(2), and the only alternatives that

an agency should consider are ones that

‘‘achieve[] the objectives of the rule,’’ sec.

205(a). The UMRA Conference Report

confirms that UMRA does not override the

authorizing statute. ‘‘This section [202] does

not require the preparation of any estimate or

analysis if the agency is prohibited by law

from considering the estimate or analysis in

adopting the rule.’’ 141 Cong. Rec. H3063

(daily ed. March 13, 1995).

The RFA (as amended by SBREFA) also

does not apply to this decision, as discussed

in Unit VII of this preamble. As is the case

with UMRA, even when the RFA (as

amended by SBREFA) does apply to a

regulatory action, it does not establish

decisional criteria that an agency must follow,

much less override the underlying substantive

statute. When the RFA was adopted in 1980,

Congress made clear that it did not alter the

substantive standards contained in authorizing

statutes: ‘‘The requirements of section 603

and 604 of this title [to prepare initial and

final regulatory flexibility analyses] do not

alter in any manner standards otherwise

applicable by law to agency action.’’ Section

606 of the RFA. The legislative history

further explains that section 606 ‘‘succinctly

states that this bill does not alter the

substantive standard contained in underlying

statutes which defines the agency’s

mandate.’’59 When Congress passed

SBREFA in 1996 and amended parts of the

RFA, it did not amend section 606.

Even when a regulatory decision is subject

to sections 603 and 604 and an agency is

therefore required to analyze alternatives that

minimize significant economic impacts on

small entities, the RFA (as amended by

SBREFA) does not establish decisional

criteria that an agency is required to follow.

Both section 603 and 604 provide that the

alternatives an agency should consider are to

be ‘‘consistent with the stated objectives of

applicable statutes.’’ Sec. 603 and 604(a)(5).

Furthermore, although the RFA (as amended

by SBREFA) requires agencies to consider

alternatives that minimize impacts on small

entities subject to the rules’ requirements and

to explain their choice of regulatory

alternatives, it does not require agencies to

select such alternatives. For these reasons, the

RFA (as amended by SBREFA) does not

conflict with or override the Clean Air Act’s

preclusion of considering costs and similar

factors in setting NAAQS.

3. Conclusion. In summary, EPA believes

that the judicial decisions cited above are

both correct and dispositive on the question

of considering costs in setting NAAQS, and

that the Agency is not free to reinterpret the

Act on that question.

B. Margin of Safety

Several commenters questioned the

approach used by the Administrator in

specifying O3 standards that protect public

health with an adequate margin of safety.

Rather than the integrative approach applied

by the Administrator, these commenters

maintained that EPA must employ a two-step

process. The line of argument was that the

Administrator must first determine a ‘‘safe

level’’ and then apply a margin of safety

taking into account costs and societal impacts.

It was argued that this was the only approach

that would enable the Administrator to reach

a reasoned decision on a standard level that

protects public health against unacceptable

risk of harm, such that any remaining risk

was ‘‘acceptable.’’ In effect, these

commenters argued that the Administrator

must adopt the two-step methodology

endorsed in Vinyl Chloride, 824 F.2d 1146,

for setting hazardous air pollutant standards

under section 112.

In recognition of the complexities facing

the Administrator in determining a standard

that protects public health with an adequate

margin of safety, the courts have declined to

impose any specific requirements on the

Administrator’s methodological approach.

Thus, in Lead Industries the court held that

the selection of any particular approach to

providing an adequate margin of safety ‘‘is

a policy choice of the type Congress

specifically left to the Administrator’s

judgment. This court must allow him the

discretion to determine which approach will

best fulfill the goals of the Act.’’ 647 F.2d

at 1161–62. As a result, the Administrator is

not limited to any single approach to

determining an adequate margin of safety and

may, in the exercise of her judgment, choose

an integrative approach, a two-step approach,
26 Federal Register / Vol. 62, No. 138 / Friday, July 18, 1997 / Prepublication

60 This comment period reflects an extension of 22 days

beyond the 67–day comment period originally announced

in the proposal.

or perhaps some other approach, depending

on the particular circumstances confronting

her in a given NAAQS review.

With respect to the approach advanced in

comment, the PM10 case made clear that the

two-step process endorsed in Vinyl Chloride

was necessary because of the need under

section 112 of the Act to ‘‘sever

determinations that must be based solely on

health considerations from those that may

include economic and technical

considerations.’’ 902 F.2d at 973. Because the

Administrator may not consider cost and

technological feasibility under section 109,

however, the court concluded that ‘‘the

rationale for parsing the Administrator’s

determination into two steps is inapposite.’’

Id.

Because such factors as the nature and

severity of the health effects involved, the

size of the sensitive population(s) at risk, the

types of health information available, and the

kind and degree of uncertainties that must be

addressed will vary from one pollutant to

another, the most appropriate approach to

establishing a NAAQS with an adequate

margin of safety may be different for each

standard under review. Thus, no generalized

paradigm such as that imbedded in EPA’s

cancer risk policy can substitute for the

Administrator’s careful and reasoned

assessment of all relevant health factors in

reaching such a judgment. As noted above,

both Congress and the courts have left to the

Administrator’s discretion the choice of

analytical approaches and tools, including risk

assessments, rather than prescribing a

particular formula for reaching such

determinations. Because of the inherent

uncertainties that the Administrator must

address in margin of safety determinations,

they are largely judgmental in nature,

particularly with respect to non-threshold

pollutants, and may not be amenable to

quantification in terms of what risk is

‘‘acceptable’’ or any other metric. In view of

these considerations, the task of the

Administrator is to select an approach that

best takes into account the health effects and

other information assessed in the air quality

criteria for the pollutant in question and to

apply appropriate and reasoned analysis to

ensure that the scientific uncertainties are

taken into account in an appropriate manner.

In this instance, the Administrator has

clearly articulated the factors she has

considered, the judgments she has had to

make in the face of uncertain and incomplete

information, and alternative views as to how

such information should be interpreted, in

reaching her decision on standard

specifications that will protect public health

with an adequate margin of safety. See Unit

II of this preamble. Her conclusions on these

matters are fully supported by the record.

C. Comment Period

A number of commenters maintained that

EPA erred by not extending the comment

period for the review of the O3 standards by

at least 60 days. The commenters further

maintained there was no justification for

keeping the O3 standard review on the same

schedule as the PM NAAQS, since the O3

review is not subject to a court-ordered

deadline as is PM.

The EPA believes that there are benefits to

reviewing the O3 and PM NAAQS on the

same schedule, for the reasons set forth in the

proposal, and that the period available for

public comment was sufficient. All interested

parties have had ample notice that EPA

intended to complete this review of the O3

standards on an expedited basis. The EPA

first announced its intention in a March 9,

1993, Federal Register notice (58 FR 13008)

when the Administrator announced her

commitment to expedite the review in light

of new scientific evidence of the effects of

O3 on human health. In a February 3, 1994,

Federal Register notice (59 FR 5164), the

Administrator announced a schedule for

completion of the scientific assessment and

review of the standards, including

opportunities for public comment. This

schedule called for proposal in mid-1996 and

a final decision as to whether to revise the

O3 standard by mid–1997. On June 12, 1996,

in an advance notice of proposed rulemaking

(61 FR 29719), the Administrator announced

her decision to delay the O3 proposal

schedule in order to place it on the same

schedule as the PM standard review. In that

notice, she explained her rationale for

reviewing the O3 and PM NAAQS on the

same schedule and pointed to the benefits of

developing integrated implementation

strategies. She also provided advance notice

of the kinds of revisions to the primary and

secondary O3 NAAQS that she was

considering proposing. In effect, the delay of

the O3 proposal provided interested parties an

additional 5 months to review EPA’s

assessments of the scientific and technical

information, as well as staff and CASAC

recommendations as to whether revisions

were appropriate. With this background, EPA

believes all interested parties had ample

opportunity to develop specific comments on

the O3 proposal during the 89 days allotted

for public comment.60

Another commenter raised a more specific

issue in requesting a 60–day extension of the

public comment period. This commenter

maintained that such an extension was

necessary because EPA did not make publicly

available certain O3 exposure and health risk

assessment reports and an explanatory

memoranda in a timely manner. In response,

EPA notes that the documents in question

were entered into the docket on February 12,

1997, and placed on the OAQPS Technology

Transfer Bulletin Board on February 13,

1997, so that they would have wide public

circulation. Because this commenter’s

organization was aware that the reports were

under preparation and had expressed interest

in receiving them, copies were sent directly

to the responsible staff person on February

12, 1997. Given that these reports build on

analyses and methodologies that were

available to the public during the scientific

phase of the O3 NAAQS review, well in

advance of the proposal, and that the new

analyses and explanatory memorandum were

only 120 pages in length, EPA believes that

this commenter had sufficient time to review

the material and prepare comments before the

close of the comment period on March 12,

1997.

D. 1990 Act Amendments

Contrary to the view expressed in some

public comments, EPA maintains that the

provisions of subpart 2 of Part D of Title I

of the Clean Air Act, enacted in 1990, do not

preclude EPA from revising the O3 standard.

The provisions of subpart 2 simply do not

limit EPA’s clear authority under section 109

to revise the standard.

The basic contention of the commenters is

that because the provisions of subpart 2 are

linked to the current 1–hour, 0.12 ppm O3

standard, they prohibit EPA from revising the

O3 standard. These provisions, however, do

not lead to such a conclusion. Moreover, the

view expressed in these comments ignores

provisions indicating that Congress believed

that EPA could revise the O3 NAAQS.

At the outset, it should be noted that

Congress expressly authorized EPA to revise

any ambient air quality standard in section

109. That section, which requires EPA to

review and revise, as appropriate, each

NAAQS every 5 years, contains no language

expressly or implicitly prohibiting EPA from

revising a NAAQS. If Congress had intended

to preclude EPA from reviewing and revising

a NAAQS, which is one of EPA’s

fundamental functions, Congress would have

specifically done so. Clearly, Congress knew

how to preclude EPA from exercising

otherwise existing regulatory authority and

did so in other instances. See section

202(b)(1)(C)(expressly precluding EPA from

modifying certain motor vehicle standards

prior to model year 2004); section

112(b)(2)(preventing EPA from adding to the

list of hazardous air pollutants any air

pollutants that are listed under section 108(a)

unless they meet the specific exceptions of

section 112(b)(2)); section 249(e)(3), (f) and

section 250(b)(limiting EPA’s authority

regarding certain clean-fuel vehicle

programs). No such language was included in

either section 109 or elsewhere in the Act and

no such implication may properly be based

on the provisions of subpart 2 of Part D of

Title I.

Second, other provisions of the Act

expressly contemplate EPA’s ability to revise

any NAAQS, and provide no indication that

such ability is limited to standards other than
Federal Register / Vol. 62, No. 138 / Friday, July 18, 1997 / Prepublication 27

those whose implementation is the subject of

subparts 2, 3 and 4 of Part D. For example,

section 110(a)(2)(H)(i) provides that SIPs are

to provide for revisions ‘‘from time to time

as may be necessary to take account of

revisions of such national primary or

secondary ambient air quality standard ***.’’

Section 107(d)(1)(A) provides a process for

designating areas as attainment,

nonattainment, or unclassifiable ‘‘after

promulgation of a new or revised standard for

any pollutant under section 109 ***.’’ Section

172(e) addresses modifications of national

primary ambient air quality standards.

Finally, section 172(a)(1) expressly

contemplates that EPA may revise a standard

in effect at the time of enactment of the 1990

Clean Air Act Amendments. Section

172(a)(1)(A) provides EPA with authority to

classify nonattainment areas on or after the

designation of an area as nonattainment with

respect to ‘‘any revised standard, including a

revision of any standard in effect on the date

of the enactment of the Clean Air Act

Amendments of 1990.’’ Plainly, Congress

had no intention of prohibiting EPA from

revising any of the ambient standards in

effect at the time of the enactment of the 1990

amendments.

Third, the provisions of subpart 2 of Part

D do not support the contention that they

somehow preclude EPA from exercising its

authority to revise the NAAQS under section

109. The fact that Congress laid out an

implementation program for the O3 standard

existing at the time of the 1990 amendments

in no way suggests that Congress intended to

preclude EPA from exercising the authority

it provided EPA to revise the NAAQS when

the health data on which EPA bases such

decisions warranted a change in the standard.

Contrary to this contention, section 181(a)

does not preclude the designation of areas as

nonattainment for O3 that have design values

less than 0.121 ppm. EPA has designated as

nonattainment numerous areas whose design

value was less than 0.121 ppm, but which

violated the existing 1–hour, 0.12 ppm O3

standard. These areas, referred to as

‘‘nonclassifiable nonattainment areas,’’

include ‘‘submarginal’’ areas (i.e., O3

nonattainment areas with design values below

0.121 ppm), (See 57 FR 13498, 13524–27,

April 16, 1992). These areas include areas

that were designated nonattainment prior to

the 1990 amendments and whose

nonattainment designation Congress required

to be continued after 1990. See section

107(d)(1)(C)(i). Clearly, Congress did not

prohibit the designation of areas as

nonattainment for O3 with design values

below 0.121 ppm; in fact, in some cases,

Congress required it. Furthermore, the

position advanced by the commenters would

mean that, in effect, Congress in the 1990

amendments legislatively revised the thenexisting 1–hour, 0.12 ppm O3 standard to a

0.121 ppm standard. There is no indication

that Congress intended to do that.

In addition, the fact that Congress directed

EPA to use ‘‘the interpretation methodology

issued by the Administrator most recently’’

before the date of the enactment of the Clean

Air Act Amendments of 1990 in the context

of subpart 2 does not add any support to the

commenters’ position; it merely shows that

Congress intended the existing 1–hour, 0.12

ppm standard to be implemented in a

specified way, not that Congress intended to

preclude EPA from using its otherwise

applicable authority to revise the standard.

The EPA also disagrees with the contention

that sections 172(a)(1)(C) and (a)(2)(D),

which provide that the general classification

and attainment date provisions of section 172

do not apply to areas for which classifications

or attainment dates ‘‘are specifically provided

under other provisions of this part,’’ support

the conclusion that Congress intended to

prohibit EPA from revising the O3 standard.

These provisions simply mean that where

Congress elsewhere provided for specific

classifications and attainment dates, as in the

case of subpart 2 regarding the 1–hour, 0.12

ppm standard, EPA is not to modify those

classifications or dates. The EPA is not

purporting to do this. These provisions do not

lead to the conclusion that because Congress

established them for the O3 standard in effect

at the time of the 1990 amendments,

Congress meant that EPA could not revise

that standard in order to appropriately protect

public health.

EPA does not accept the thesis that

revising the O3 standard forces EPA to

violate other provisions of the Act and,

therefore, is not an ‘‘appropriate’’ revision of

the standard under section 109. Revising the

O3 standard in accordance with the language

of section 109 does not result in EPA

violating any provision of the Act. On the

other hand, a determination by EPA that the

O3 standard should not be revised, even

though EPA concludes that it needs to be

revised to protect public health with an

adequate margin of safety, would violate

section 109.

Also, EPA does not believe that carrying

out the provisions of section 109 to set a new

O3 standard to protect public health with an

adequate margin of safety somehow ‘‘risks

undermining both perceptions and reality of

the functioning of our democratic form of

government.’’ EPA is merely implementing

the words of the Clean Air Act, a statute

passed by the Congress and signed by the

President. To refuse to revise the standard

notwithstanding the need to protect public

health as enunciated in section 109 would

thwart the objectives of those who passed and

signed the Clean Air Act on behalf of the

American public.

Finally, for the reasons stated above,

EPA’s analysis of its ability to implement the

revised O3 standard under the provisions of

subpart 1 of Part D of Title I does not support

the view that Congress prohibited EPA from

revising the standard. Congress clearly

specified an approach to the implementation

of the 1–hour, 0.12 ppm O3 standard in the

provisions of subpart 2 of Part D. EPA

believes that the clear and express linkage of

that approach to the 1–hour, 0.12 ppm

standard indicates that it may implement a

revised O3 standard in accord with the

general principles of subpart 1 of Part D, as

informed by the no-backsliding principle

embodied in section 172(e). That Congress

directed specifically how EPA and the States

should implement the 1–hour, 0.12 ppm O3

standard does not carry with it the implication

that Congress intended to prohibit EPA from

exercising its otherwise clear and express

authority to revise that standard in order to

carry out one of its fundamental missions, the

establishment of ambient air quality standards

to protect public health with an ample margin

of safety. If Congress had intended to prohibit

EPA from exercising such a fundamental

authority it would have clearly specified (as

it did in other instances) that EPA could not

do so.

The EPA also disagrees with the contention

that a revised O3 standard may not be

implemented for so long as the current 1–

hour, 0.12 ppm O3 standard remains in effect.

The fact that the provisions of subpart 2 of

Part D are focused on the implementation of

the current standard does not mean that, if a

new or revised O3 standard is promulgated

pursuant to section 109, the new standard

could not simultaneously be implemented

under the provisions of section 110 and

subpart 1 of Part D, which apply regardless

of the criteria pollutant of concern. There is

no language in sections 181 or 182 that

precludes the implementation of a different

standard under other authority; those

provisions simply govern the implementation

of the 1–hour, 0.12 ppm O3 standard. EPA

further notes that it has historically had more

than one primary standard for criteria

pollutants (e.g., annual and 24–hour PM10

and sulfur dioxide standards, and 8–hour and

1–hour CO standards) and believes that had

Congress wanted to preclude EPA from

implementing two primary O3 standards

simultaneously it would have expressly

precluded EPA from doing so. Thus, EPA

does not believe that it must repeal the 1–

hour, 0.12 ppm O3 standard before it can

promulgate and implement a new primary O3

standard.

V. Technical Changes to Part 50

In the proposal, the EPA proposed two

alternative secondary standards: (1) A

secondary standard set identical to the

proposed 0.08 ppm, 8-hour primary standard;

or (2) a seasonal secondary standard

expressed in the SUM06 form. For the

reasons discussed in Unit III, the EPA has

decided to promulgate a secondary ambient

air quality standard for O3 that is identical to

the primary ambient air quality standard.
28 Federal Register / Vol. 62, No. 138 / Friday, July 18, 1997 / Prepublication

61 The term precision is used to denote both the

reproducibility of a measurement under a constant set of

conditions, as well as other components of measurement

uncertainty such as instrument drift and relative bias.

Accordingly, the language adopted in the

final regulation (40 CFR 50.10) has been

revised to reflect this change.

In the proposal, the regulatory text in

§ 50.9 inadvertently included language about

what it means when the standard is not met,

that should have been discussed in 40 CFR

part 50, Appendix H. Therefore this sentence

has been removed from § 50.10(b), and the

discussion moved to the new Appendix I to

40 CFR part 50, which now provides

additional clarification on calculations for

sites with less than complete data, as

discussed in Unit VI. of this preamble.

VI. Revisions to Appendices D, E, and H

The EPA is finalizing the changes to

Appendices D and E to 40 CFR part 50, that

were proposed and described in the proposal.

No adverse comments were received on these

changes.

Because the revocation of the existing 1–

hour standard will become effective at a later

date (as discussed above in Unit II.B.4.), EPA

is retaining Appendix H in its current form.

A new Appendix I explains the computations

necessary for determining when the new 8–

hour primary and secondary standards are

met.

The new Appendix I addresses data

completeness requirements, data reporting,

handling, and rounding conventions, and

example calculations. The discussion in this

unit sometimes refers to the contents of the

new Appendix I as revisions to Appendix H,

so as to highlight how the new Appendix I

differs from the current Appendix H. For

example, the example calculations in

Appendix I differ from those in Appendix H

to reflect the final form of the new 8–hour

primary standard.

In the proposal, two alternative secondary

standards were proposed, and the proposed

changes to Appendix H addressed both

alternatives: A secondary standard set

identical to the proposed 0.08 ppm, 8–hour

primary standard; or a seasonal secondary

standard expressed in the SUM06 form. For

the reasons discussed above, the

Administrator has decided to set the

secondary standard identical to the primary

standard as reflected in Appendix I.

Key elements of Appendix I, particularly as

they differ from those of Appendix H, are

outlined below.

A. Data Completeness

One key change to Appendix H,

incorporated into Appendix I, for the new

0.08 ppm, 8–hour primary and secondary

standards is that no numerical adjustment is

made to the measured 8–hour concentrations

to account for missing or incomplete data as

was the case with the 1–hour standard.

Instead, the EPA has decided to replace the

methodology used to adjust the computation

of estimated exceedances for missing data

under the 1–hour standard with new data

completeness requirements for the 8–hour

standards.

The EPA proposed that, in order to

determine that the 8–hour standards have

been met at a monitoring site during the

current 3–year period, revisions to Appendix

H would require 90 percent data

completeness, on average, with no single year

at the site having less than 75 percent data

completeness. A site could be found not to

have met the standards with less than

complete data. Almost all commenters

supported deleting the estimated exceedances

missing data adjustment procedure of the

current 1–hour standard and replacing it with

minimum data completeness requirements.

Several commenters felt that the proposed

data completeness requirement might be too

stringent and would be difficult to attain.

Other commenters recommended that some

consideration be made for hours lost due to

instrument calibration. A few commenters

thought that EPA should establish higher

minimum data completeness requirements.

Based on its analysis of available air

quality data, the EPA believes that, with the

changes to the proposal described below, the

data completeness requirement in Appendix I

is reasonable given that 90 percent of all

monitoring sites that currently operate on a

continuous basis meet this objective. The

EPA believes that a missing hour during the

day resulting from instrument calibration

should not negatively impact the ability of a

monitoring site to meet the data completeness

requirements because data completeness is

based on the number of days with valid daily

maximum 8–hour concentrations, not on the

number of non-missing hours.

In the proposal, the EPA sought comment

on whether meteorological data could provide

an objective basis for determining, on a day

for which there is missing data, that the

meteorological conditions were not conducive

to high O3 concentrations, and therefore, that

the day could be assumed to have an 8–hour

daily maximum O3 concentration less than

0.08 ppm. Under the 0.12 ppm 1–hour

standard, a missing day is assumed less than

the level of the standard only if the two

adjacent days are non-missing, and the daily

maximum 1–hour concentration on each of

those days is less than or equal to 0.09 ppm.

In the proposal, the EPA specifically

requested comment on the appropriateness of

using data on meteorological conditions, as

well as on other information that would

permit better definition of those necessary

conditions likely to result in peak 8–hour O3

concentrations in the ranges of concern. Most

commenters expressing an opinion supported

the use of meteorological data, as well as

ambient data from nearby monitoring sites to

establish that missing hours could be assumed

less than the level of the standard. Days

assumed less than the level of the standard

would be counted as non-missing when

computing whether the data completeness

requirements have been met at the site.

Taking these comments into account, EPA

has revised the proposed revisions to

Appendix H, as reflected in Appendix I, to

count missing days assumed less than the

standard when computing whether the data

completeness requirement has been met. EPA

will develop guidance on methodologies

necessary for using meteorological data and

ambient measurements to make such

determinations.

Several commenters expressed concerns

about the possibility that stratospheric O3

intrusion from aloft or forest fires may lead

to exceedances of the level of the standard,

particularly within the context of peak O3

concentrations that have been observed at

background sites. Commenters expressed

concern that such events could lead to

violations of the 8–hour standard and,

therefore, they questioned the attainability of

the proposed standard. Consistent with a

forthcoming update to EPA’s policy on

natural events for the new 8–hour standard,

EPA has revised Appendix H to specifically

address this concern by stating that whether

to use data affected by stratospheric O3

intrusion or other natural events when

determining if the standards have been met

is subject to the approval of the appropriate

Regional Administrator.

B. Data Handling and Rounding Conventions

For the reasons cited above, and taking into

account the advice of CASAC, the

Administrator has set the level of the new 8–

hour primary and secondary standards at 0.08

ppm. As EPA explained in the proposal, the

level of the 8–hour standard is expressed to

the second decimal place, 0.08 ppm, with the

support of CASAC and in part to reflect

uncertainties in the health effects evidence

upon which the proposed standard is based.

More specifically, these uncertainties include

the measurement uncertainty and

representativeness inherent in the reported

ambient O3 concentrations used in field and

epidemiological studies and the uncertainty in

the exposure estimates upon which

quantitative risk assessments have been

based. In the proposal, EPA stated its belief

that expressing the proposed standard to the

second decimal place is also consistent with

the quality assurance guidelines that indicate

the precision61 for such O3 measurements

shall be within ± 15 percent.

To determine whether the standard is met,

EPA proposed that the calculated value of the

third-highest maximum 8–hour average

concentrations, averaged over 3 years, is

compared to the level of the standard. It is

the level of the standard, 0.08 ppm, expressed

to two decimal places that determines the

number of significant digits to be used when

comparing air quality measurements to the
Federal Register / Vol. 62, No. 138 / Friday, July 18, 1997 / Prepublication 29

62 One individual commenter provided an analysis of

current monitoring technology and suggested that the

precision and accuracy data supported setting the standard

to three decimal places and rounding the annual average

third-highest 8–hour average concentration up at 0.001

ppm. EPA believes that the precision and accuracy data

cited by the commenter does not capture all of the

uncertainty inherent in ambient air quality measurements.

standard. The EPA proposed that, for hourly

data, 8–hour average O3 concentrations

computed from such hourly data, and the 3–

year averages of the third highest maximum

8–hour average concentrations, that the third

decimal place is carried forward as the

rounding digit, and the insignificant digits are

truncated. To compare the calculated 3–year

average O3 concentration to the level of the

standard, the third decimal place of the

calculated value is rounded. The current

rounding convention is to round up digits

equal to or greater than 5.

In the proposal, EPA recognized that the

level of public health protection afforded by

the use of the current rounding convention

could be increased by replacing the current

rounding convention with a convention that

defined the smallest increment above the

level of the standard to be 0.001 ppm for the

purposes of determining whether the standard

has been met. The EPA solicited comment on

the use of such an alternative rounding

convention, with regard to potential increased

public health protection, as well as to

potential effects on the probability of

attainment misclassifications and on the

stability of the standard.

Of the many States that commented

specifically on the rounding convention, most

State agencies cited concerns by their

monitoring staffs about the precision and

accuracy of measured O3 concentrations in

ambient environments and recommended

maintaining the current rounding convention.

A tribal association also supported the current

rounding convention. Other State agencies

felt that newer instruments were capable of

supporting a rounding convention set at 0.001

ppm. Of those environmental and health

associations that commented, all supported

replacing the current rounding convention

with the alternative 0.001 ppm convention.62

All industry and trade associations that

commented on rounding recommended that

EPA retain the current rounding convention.

After taking these comments into account,

EPA has decided that the current rounding

approach is appropriate for comparing

monitoring data to the level of the standard

expressed to two decimal places. The current

rounding procedure has the effect of reducing

the probability of misclassifying an

attainment area as nonattainment and of

producing a more stable attainment test. The

EPA believes that measures that promote a

stable control program will lead to greater

long-term health protection and risk

reduction. For the reasons stated above, and

taking into account the uncertainty in the

exposure estimates upon which quantitative

risk assessments have been based,

measurement uncertainty, data

representativeness, and the desirability of

these resulting effects, EPA is retaining the

current rounding convention and finalizing

the data handling and rounding conventions,

in Appendix I, as proposed.

VII. Regulatory and Environmental

Impact Analyses

As discussed in Unit IV of this preamble,

the Clean Air Act and judicial decisions make

clear that the economic and technological

feasibility of attaining ambient standards are

not to be considered in setting NAAQS,

although such factors may be considered in

the development of State plans to implement

the standards. Accordingly, although, as

described below, a Regulatory Impact

Analysis (RIA) has been prepared, neither the

RIA nor the associated contractor reports

have been considered in issuing this final

rule.

A. Executive Order 12866

Under Executive Order 12866, 58 FR

51735 (October 4, 1993), the Agency must

determine whether a regulatory action is

‘‘significant’’ and, therefore, subject to Office

of Management and Budget (OMB) review

and other requirements of the Executive

Order. The order defines ‘‘significant

regulatory action’’ as any regulatory action

that is likely to result in a rule that may:

(1) Have an annual effect on the economy

of $100 million or more or adversely affect

in a material way the economy, a sector of

the economy, productivity, competition, jobs,

the environment, public health or safety, or

State, local, or tribal governments or

communities.

(2) Create a serious inconsistency or

otherwise interfere with an action taken or

planned by another Agency.

(3) Materially alter the budgetary impact of

entitlements, grants, user fees, or loan

programs or the rights and obligations of

recipients thereof.

(4) Raise novel legal or policy issues

arising out of legal mandates, the President’s

priorities, or the principles set forth in the

Executive Order.

In view of its important policy

implications, this action has been judged to

be a ‘‘significant regulatory action’’ within

the meaning of the Executive Order. As a

result, under section 6 of the Executive Order,

EPA has prepared an RIA, entitled

‘‘Regulatory Impact Analysis for Particulate

Matter and Ozone National Ambient Air

Quality Standards and Proposed Regional

Haze Rule (July 1997).’’ This RIA assesses

the costs, economic impacts, and benefits

associated with potential State

implementation strategies for attaining the

PM and O3 NAAQS and the proposed

Regional Haze Rule. Changes made in

response to OMB suggestions or

recommendations will be documented in the

public docket and made available for public

inspection at EPA’s Air and Radiation Docket

Information Center (Docket No. A-95-58).

The RIA will be publicly available in hard

copy by contacting the U.S. Environmental

Protection Agency Library at the address

under ‘‘Availability of Related Information’’

and in electronic form as discussed above in

‘‘Electronic Availability.’’

B. Regulatory Flexibility Analysis

The Regulatory Flexibility Act (RFA), 5

U.S.C. 601 et seq., provides that, whenever

an agency is required to publish a general

notice of rulemaking for a proposed rule, the

agency must prepare an initial regulatory

flexibility analysis for the proposed rule

unless the head of the agency certifies that the

rule ‘‘will not, if promulgated, have a

significant economic impact on a substantial

number of small entities’’ (section 605(b)).

The EPA certified each of the proposed

NAAQS rules based on its conclusion that the

rule would not establish requirements

applicable to small entities and therefore

would not have a significant economic impact

on small entities within the meaning of the

RFA. See 61 FR 65638, 65668 (PM

proposal); 61 FR 65716, 65746 (ozone

proposal), both published on December 13,

1996. Accordingly, the Agency did not

prepare an initial regulatory flexibility

analysis for the proposed rule, but it did

conduct a more general analysis of the

potential impact on small entities of possible

State strategies for implementing any new or

revised NAAQS.

At the heart of EPA’s certification of the

proposed NAAQS rule was the Agency’s

interpretation of the word ‘‘impact’’ as used

in the RFA. Is the ‘‘impact’’ to be analyzed

under the RFA a rule’s impact on the small

entities that will be subject to the rule’s

requirements, or the rule’s impact on small

entities in general, whether or not they will

be subject to the rule? In the case of NAAQS

rules, the question arises because of the

congressionally-designed mixture of Federal

and State responsibilities in setting and

implementing the NAAQS.

As EPA explained in the proposal, NAAQS

rules establish air quality standards that States

are primarily responsible for meeting. Under

section 110 and part D of Title I of the CAA,

every State develops a State Implementation

Plan (SIP) containing the control measures

that will achieve a newly promulgated

NAAQS. States have broad discretion in the

choice of control measures. As the U.S.

Supreme Court noted in Train v. NRDC:

[P]rimary [NAAQS] deal with the quality of

outdoor air and are fixed on a nationwide basis at

a level which the agency determines will protect

the public health. It is the attainment and

maintenance of these standards which section

110(a)(2)(A) requires that State plans provide. In

complying with this requirement, a State’s plan

must include ‘‘emission limitations’’ which are

regulations of the composition of substances
30 Federal Register / Vol. 62, No. 138 / Friday, July 18, 1997 / Prepublication

63 It is worth noting that Federal rules that apply

nationally also play a role in reducing emissions governed

by NAAQS. For instance, EPA rules under Title II of the

CAA require reductions in ozone-forming emissions from

on and off-road vehicles and the fuels that power them.

When EPA issues such rules, it conducts the analysis

required under the RFA. For example, EPA performed

regulatory flexibility analyses for the reformulated gasoline

rule issued under section 211(k) of the CAA. See 59 FR

7716, February 16, 1994.

emitted into the ambient air from such sources as

power plants, service stations and the like. They are

the specific rules to which operators of pollution

sources are subject and which, if enforced, should

result in ambient air which meets the national

standards.

The Agency is plainly charged by the Act with

the responsibility for setting the national ambient

air standards. Just as plainly, it is relegated to a

secondary role in the process of determining and

enforcing the specific, source-by-source emission

limitations which are necessary if the national

standards are to be met. Under 110(a)(2), the

Agency is required to approve a State plan which

provides for the timely attainment and maintenance

of the ambient air standards, and which also

satisfies that section’s other general requirements.

The Act gives the agency no authority to question

the wisdom of a State’s choices of emission

limitations if they are part of a plan which satisfies

the standards of 110(a)(2) and the Agency may

devise and promulgate a plan of its own only if

the state fails to submit an implementation plan

which satisfies those standards. Section 110(c).

421 U.S. 60, at 78–79 (1975) (emphasis in

original). In short, NAAQS rules themselves

do not establish any control requirements

applicable to small entities. State rules

implementing the NAAQS may establish such

requirements and the extent to which they do

depends primarily on each State’s strategy for

meeting the NAAQS.63

To determine the proper interpretation of

‘‘impact’’ under the RFA, EPA considered

the RFA’s stated purpose, its requirements for

regulatory flexibility analyses, its legislative

history, the amendments made by the Small

Business Regulatory Enforcement Fairness

Act of 1996 (SBREFA)(Pub. L. 104–121),

and caselaw. The EPA concluded that all of

these traditional tools of statutory

construction point in one direction—that an

agency is required to assess the impact of a

rule on the small entities that will be subject

to the rule’s requirements, because the

purpose of a regulatory flexibility analysis is

to consider ways of easing or even waiving

a rule’s requirements as they will apply to

small entities, consistent with the statute

authorizing the rule. That purpose cannot be

served in the case of the rules like the

NAAQS that do not have requirements that

apply to small entities.

More specifically, EPA noted that its

interpretation of ‘‘impact’’ flows from the

express purpose of the RFA itself. As the

RFA’s ‘‘Findings and Purposes’’ section

(Pub. L. 96–354, section 2) makes clear,

Congress enacted the RFA in 1980 out of

concern that agencies were writing one-sizefits-all regulations that in fact did not fit the

size and resources of small entities. Congress

noted that it is generally easier for big

businesses to comply with regulations, and

that small businesses are therefore at a

competitive disadvantage in complying with

uniform rules. Congress also noted that small

entities’ relative contribution to the problem

a rule is supposed to solve may not warrant

applying the same requirements to large and

small entities alike. In the RFA itself,

Congress therefore stated:

It is the purpose of this Act to establish as a

principle of regulatory issuance that agencies shall

endeavor, consistent with the objectives of the rule

and of applicable statutes, to fit regulatory and

informational requirements to the scale of the

businesses, organizations, and governmental

jurisdictions subject to regulation.

[Pub. L. 96–354, section 2(b).]

The EPA further noted that the RFA

sections governing initial and final regulatory

flexibility analyses reflect this statement of

purpose. RFA sections 603 and 604 require

that initial and final regulatory flexibility

analyses identify the types and estimate the

numbers of small entities ‘‘to which the

proposed rule will apply’’ (sections 603(b)(3)

and 604(a)(3)). Similarly, they require a

description of the ‘‘projected reporting,

recordkeeping and other compliance

requirements of the proposed rule, including

an estimate of the classes of small entities

which will be subject to the requirement’’

(sections 603(b)(4) and 604(a)(4)). At the

core of the analyses is the requirement that

agencies identify and consider ‘‘significant

regulatory alternatives’’ that would

‘‘accomplish the stated objectives of

applicable statutes and which minimize any

significant economic impact of the proposed

rule on small entities’’ (section 603(c) and

604(a)(5)). Among the types of alternatives

agencies are to consider are the establishment

of different ‘‘compliance or reporting

requirements or timetables’’ for small entities

and the exemption of small entities ‘‘from

coverage of the rule, or any part’’ of the rule

(section 603(c)(1) and (4)). The RFA thus

makes clear that regulatory flexibility

analyses are to focus on how to minimize rule

requirements on small entities.

As EPA further explained, since regulatory

flexibility analyses are not required for a rule

that will not have a ‘‘significant economic

impact on a substantial number of small

entities,’’ it makes sense to interpret

‘‘impact’’ in light of the requirements for

such analyses. Regulatory flexibility analyses,

as described above, are to consider how a rule

will apply to small entities and how its

requirements may be minimized with respect

to small entities. In this context, ‘‘impact’’ is

appropriately interpreted to mean the impact

of a rule on the small entities subject to the

rule’s requirements.

The Agency cited two Federal court cases

in support of its interpretation. In Mid-Tex

Elec. Co-op v. FERC, 773 F.2d 327, 342

(D.C. Cir. 1985), petitioners claimed that the

RFA required an agency to analyze the

effects of a rule on small entities that were

not regulated by the rule but might be

indirectly impacted by it. Petitioners noted

that the Small Business Administration (SBA)

also interpreted the RFA to require analysis

of a rule’s impact on small entities not

regulated by the rule, and argued that the

court should defer to the SBA’s position in

light of its compliance monitoring role under

the RFA. After reviewing the RFA’s

‘‘Findings and Purposes’’ section, its

legislative history, and its requirements for

regulatory flexibility analyses, the Mid-Tex

court rejected petitioners’ interpretation. As

the court explained:

The problem Congress stated it discerned was

the high cost to small entities of compliance with

uniform regulations, and the remedy Congress

fashioned—careful consideration of those costs in

regulatory flexibility analyses—is accordingly

limited to small entities subject to the proposed

regulation. *** [W]e conclude that an agency may

properly certify that no regulatory flexibility

analysis is necessary when it determines that the

rule will not have a significant economic impact

on a substantial number of small entities that are

subject to the requirements of the rule.

Id. at 342. Notably, Congress let this

interpretation stand when it recently amended

the RFA in enacting the SBREFA.

The EPA also cited a recent case affirming

the Mid-Tex court’s interpretation. In United

Distribution Companies v. FERC, 88 F.3d

1105, 1170 (D.C. Cir. 1996), the court noted

that the Mid-Tex court:

*** conducted an extensive analysis of the RFA

provisions governing when a regulatory flexibility

analysis is required and concluded that no analysis

is necessary when an agency determines ‘‘that the

rule will not have a significant economic impact

on a substantial number of small entities that are

subject to the requirements of the rule’’.

Id., citing and quoting Mid-Tex (emphasis

added by United Distribution court).

The Agency went on to explain that given

the Federal/State partnership for attaining

healthy air, the proposed NAAQS, if adopted,

would not establish any requirements

applicable to small entities. Instead, any new

or revised standard would establish levels of

air quality that States would be primarily

responsible for achieving by adopting plans

containing specific control measures for that

purpose. The proposed NAAQS rule was thus

not susceptible to regulatory flexibility

analysis as prescribed by the amended RFA.

Since it would establish no requirements

applicable to small entities, it afforded no

opportunity for EPA to fashion for small

entities less burdensome compliance or

reporting requirements or timetables, or

exemptions from all or part of the rule. For

these reasons, EPA certified that the proposed

rule ‘‘will not, if promulgated, have a

significant economic impact on a substantial

number of small entities,’’ within the

meaning of the RFA. Because EPA was not

required to prepare an initial regulatory
Federal Register / Vol. 62, No. 138 / Friday, July 18, 1997 / Prepublication 31

64 Contrary to what some commenters assumed, the SIP

requirements of subpart 2 of part D of Title I will not apply

to SIPs to implement the revised ozone NAAQS. Those

requirements were enacted by Congress in 1990 to address

nonattainment of a 0.12 ppm 1-hour ozone NAAQS. To

the extent those requirements remain in effect, they apply

only to SIPs for areas still in nonattainment with that

standard; they do not apply to SIPs for areas in

nonattainment only with respect to the ozone NAAQS

adopted today. Further, to the extent SIPs for areas in

nonattainment with the previous ozone standard remain

subject to subpart 2 requirements, there will be no

incremental change in the impact on sources regulated by

the States’ SIPs pursuant to the requirements as a result

of today’s promulgation.

flexibility analysis for the rule, it was also not

required to convene a Small Business

Advocacy Review Panel for the rule under

RFA section 609(b) as added by SBREFA.

Notwithstanding its certification of the

proposed rule, EPA recognized that the

proposed NAAQS, if adopted, would begin a

process of State implementation that could

eventually lead to small entities having to

comply with new or different control

measures, depending on the implementation

plans developed by the States. EPA also

recognized that the CAA does not allow EPA

to dictate or second-guess how States should

exercise their discretion in regulating to attain

any new or revised NAAQS. Under those

circumstances, EPA concluded that the best

way to take account of small entity concerns

regarding any new or revised NAAQS was to

work with small entity representatives and

States to provide information and guidance on

how States could address small entity

concerns when they write their

implementation plans.

In line with this approach, as part of the

RIA it prepared for the proposed NAAQS,

EPA analyzed how hypothetical State plans

for implementing the proposed rule might

affect small entities. The analysis was

necessarily speculative and limited, since it

depended on projections about what States

might do several years in the future and did

not take into account any new strategies that

might be developed and recommended by the

FACA subcommittee formed to help devise

potential strategies for implementing a new or

revised NAAQS (see discussion of RIA and

FACA process in the previous Unit of this

notice). Nevertheless, the analysis provided as

much information on potential small entity

impacts as was reasonably available at the

time of the proposed rule.

The Agency also took steps to ensure that

small entities’ voices were heard in the

NAAQS rulemaking itself. With Jere Glover,

Chief Counsel for Advocacy of the SBA,

EPA convened outreach meetings modeled on

the SBREFA panel process to solicit and

convey small entities’ concerns with the

proposed NAAQS. Two meetings were held

as part of that process, on January 7 and

February 28, 1997, with a total attendance of

41 representatives of small businesses, small

governments and small nonprofit

organizations. Both meetings were attended

by representatives of SBA and the Office of

Management and Budget, as well as of EPA.

The key concerns raised by small entities at

those meetings related to the scientific

foundation of the proposed NAAQS and the

potential cost of implementing it, the same

concerns raised by other industry commenters

on the proposed rule. The Agency produced

a report on the meetings to ensure that small

entity concerns were part of the rulemaking

record when EPA made its final decision on

the proposal.

In light of States’ pivotal role in NAAQS

implementation, EPA also undertook a

number of additional activities to assist and

encourage the States to be sensitive to small

entity impacts as they implement any new or

revised NAAQS. With the SBA, EPA began

an interagency panel process to collect advice

and recommendations from small entity

representatives on how States could lessen

any impacts on small entities. The EPA plans

to issue materials in two phases to help States

develop their implementation plans. In view

of States’ discretion in implementing the

NAAQS, these materials will mostly take the

form of guidance, which is not subject to the

RFA’s requirement for initial regulatory

flexibility analysis. (Under RFA section 603,

that requirement applies only to binding rules

that are required to undergo notice-andcomment rulemaking procedures.) But

regardless of the form such materials take,

EPA is employing panel procedures to ensure

that small entities have an opportunity to raise

any concerns prior to the materials being

issued in draft form.

To supplement the input the Agency

receives from the ongoing CAAAC process

(described earlier in this Unit of this

preamble), EPA also added more small entity

representatives to the subcommittee on

implementation of any new or revised

NAAQS. These representatives have formed

a small entity caucus to develop and bring to

the subcommittee a focused approach to small

entity issues. These new subcommittee

members are also part of the group in the

aforementioned panel process. By means of

these various processes, EPA hopes to

promote the consideration of small entity

concerns and advice throughout the NAAQS

implementation process.

In response to the proposed rule, a number

of commenters questioned EPA’s decision to

certify that the proposed NAAQS will not

have a significant impact on a substantial

number of small entities. Some commenters

disagreed with EPA’s view that the proposed

NAAQS would not establish regulatory

requirements applicable to small entities.

These commenters argued that a number of

control requirements applicable to small

entities would automatically result from

promulgation of the proposed NAAQS, such

as new reasonable further progress, SIP and

Federal Implementation Plan (FIP)

requirements. Other commenters stated that it

is possible for EPA to assess the impacts of

the NAAQS revision on small entities and

that, to a limited extent, EPA has already

done so. Further, a number of commenters

argued that EPA has a legal obligation under

the RFA, as amended by SBREFA, to choose

a NAAQS alternative that minimizes the

impact on small entities. Some commenters

questioned EPA’s interpretations of the MidTex and United Distribution cases. In

addition, other commenters stated that EPA’s

position regarding the NAAQS and the RFA

is inconsistent with its past practice and the

legislative history of the RFA. Finally, a few

commenters noted that the panel process EPA

conducted for the proposed NAAQS did not

satisfy the requirements of SBREFA.

EPA disagrees that promulgation of the

NAAQS will automatically result in control

requirements applicable to small entities that

EPA can and must analyze under the RFA.

As noted previously, a NAAQS rule only

establishes a standard of air quality that other

CAA provisions call on States (or in case of

State inaction, the Federal government) to

achieve by adopting implementation plans

containing specific control measures for that

purpose. Following promulgation of a new or

revised NAAQS, section 110 of the CAA

requires States and EPA to engage in a

designation process to determine what areas

within each State’s borders are attaining or

not attaining the NAAQS. Under section 110

and parts C and D of Title I of the CAA,

States then conduct a planning process to

develop and adopt their SIPs. Depending on

an area’s designation for the particular

NAAQS, these and other Title I provisions

require a State’s SIP to contain certain control

programs in addition to the control measures

that the State decides are also needed to attain

and maintain the NAAQS.

The fact that the CAA requires SIPs to

contain certain control programs under certain

circumstances does not mean that EPA either

can or must conduct a regulatory flexibility

analysis of a rule establishing a NAAQS. Just

from the standpoint of feasibility, EPA cannot

know which areas will be subject to what

mandatory SIP programs until after the

designation process is completed. Beyond

that, any mandatory SIP programs are still

implemented by the States, and States have

considerable discretion in how they

implement them. For instance, the reasonable

further progress requirement under section

172 leaves States broad discretion to

determine the rate of progress and the control

measures to achieve that progress.64 As a

result, EPA cannot be certain where and how

any mandatory programs will be implemented

with respect to small (or large) entities. Much

less can EPA know about how States will

exercise their discretion to develop additional

controls needed to attain and maintain the

NAAQS.

Even if EPA could know exactly how any

mandatory SIP programs would apply to

small entities, the purpose of the RFA is not

served by attempting a regulatory flexibility

analysis of State implementation of those
32 Federal Register / Vol. 62, No. 138 / Friday, July 18, 1997 / Prepublication

65 If and when the Agency issues any rules addressing

State implementation of any statutorily required actions,

EPA would analyze and address the impact of those rules

on small entities as appropriate under the RFA.

programs. As explained previously, the RFA

and the caselaw interpreting it clearly

establish that the purpose of the RFA is to

promote Federal agency efforts to tailor a

rule’s requirements to the scale of the small

entities that will be subject to it. That purpose

cannot be served in the case of a NAAQS rule

since the rule does not establish requirements

applicable to small entities. In promulgating

a NAAQS, the only choice before EPA

concerns the level of the standard, not its

implementation. While mandatory SIP

programs may ultimately follow from

promulgation of the NAAQS, there is nothing

EPA can do in setting the NAAQS to tailor

those programs as they apply to small entities.

Whether and how the programs will apply in

particular nonattainment areas is beyond the

scope of the NAAQS rulemaking and, indeed,

beyond EPA’s reach in any rulemaking to the

extent the applicability and terms of the

programs are prescribed by statute.65

Moreover, any mandatory SIP programs are

supplemented by discretionary State controls

that EPA has no power to tailor under the

RFA or the CAA (see Train v. NRDC, quoted

previously).

The commenters’ suggestions for

minimizing the potential impact of the

NAAQS rule on small entities run afoul of

both the RFA and the CAA. Some suggested

that EPA set a less stringent standard (or no

standard at all in the case of PM2.5) to reduce

the chance that small entities would become

subject to new or tighter SIP requirements.

Others suggested that EPA require States to

exempt small entities from new or tighter SIP

requirements. However, as explained in a

previous Unit of this notice addressing the

Agency’s authority to consider factors other

than public health in setting primary NAAQS,

the RFA neither requires nor authorizes EPA

to set a less stringent NAAQS than the

applicable CAA provisions allow in order to

reduce potential small entity impacts. Indeed,

the RFA provides that any means of

providing regulatory flexibility to small

entities be consistent with the statute

authorizing the rule. Moreover, even if EPA

set a less stringent standard, States could still

exercise their discretion to obtain any needed

emission reductions from small entities. As

the Supreme Court in Train v. NRDC made

clear, EPA has no authority to forbid States

from obtaining reductions from any particular

category of stationary sources, including

small entities. See also, Virginia v. EPA, No.

108 F.3d 1397, 1408 (D.C. Cir. 1997),

quoting Union Electric v. EPA, 427 U.S. 246,

269 (1976) (‘‘section 110 left to the states the

power to determine which sources would be

burdened by regulations and to what extent’’).

EPA’s approval of SIPs for the new or

revised NAAQS also will not establish new

requirements, but will instead simply approve

requirements that a State is already imposing.

And again, EPA does not have authority to

disapprove a State’s plan except to the extent

that the plan fails to demonstrate attainment

and maintenance of the NAAQS as required

by Title I of the CAA. In cases where EPA

promulgates a FIP, EPA might establish

control requirements applicable to small

entities, and in such a circumstance, EPA

would conduct the analyses required by the

RFA.

Some commenters argued that under the

RFA as amended by SBREFA, EPA now has

an obligation to choose the alternative that

minimizes the impact on small entities when

setting the NAAQS. As indicated above, EPA

disagrees with the commenters’ argument for

the reasons stated in the Unit of this notice

discussing the Agency’s authority to consider

costs and other factors not related to public

health in setting and revising primary

NAAQS. In a nutshell, both the text and

legislative history of the RFA make clear that

the RFA does not override the substantive

provisions of the statute authorizing the rule,

but only requires agencies to identify and

consider ways of minimizing the economic

impact on small entities subject to the rule in

a manner consistent with the authorizing

statute.

Some commenters disagreed with EPA’s

interpretation of the Mid-Tex and United

Distribution cases. In particular, these

commenters noted that in those cases the

relevant regulatory agency, FERC, wholly

lacked jurisdiction to regulate the small

entities at issue. According to these

commenters, EPA does have the ability and

jurisdiction to regulate small entities in the

case of the NAAQS, and therefore EPA’s

reliance on Mid-Tex and United Distribution

is misplaced.

The commenters’ attempt to distinguish the

FERC cases from the NAAQS rulemaking

wholly overlooks the courts’ reasoning, which

in fact fully supports EPA’s certification of

the proposed NAAQS. As described above,

the Mid-Tex court exhaustively reviewed the

relevant sections of the RFA and its

legislative history. Its analysis revealed that

Congress passed the RFA out of concern with

one-size-fits-all regulations and fashioned a

remedy limited to regulations that apply to

small entities. This principle is fully

applicable to the NAAQS, which creates no

rule requirements that apply to small entities.

The fact that FERC had no regulatory

authority over the small entities indirectly

affected by its rules played no essential role

in the court’s rationale. FERC could (and

apparently did in the Mid-Tex rulemaking)

estimate the potential indirect impact of its

rules on small entities. Presumably, FERC

could have also mitigated any indirect impact

by changing some aspect of the rule (or else

the small entities would have had no

incentive to sue the agency). The court

nevertheless found it unnecessary for FERC

to do either, based on its reading of the RFA

as limited to analysis of a rule’s impact on

the small entities subject to the rule’s

requirements. In reaching its decision, the

court noted that requiring agencies to

‘‘consider every indirect effect that any

regulation might have on small businesses

*** is a very broad and ambitious agenda,

*** that Congress is unlikely to have

embarked on *** without airing the matter.’’

Mid-Tex, 773 F.d. at 343.

The commenters also overstate EPA’s

regulatory authority over small entities with

respect to the regulation of criteria pollutants.

Various CAA provisions authorize EPA to

regulate various types of sources at the

Federal level to accomplish specified goals.

However, EPA’s authority to more generally

regulate sources, including small entities, in

the manner of SIPs is limited to instances of

State default of SIP responsibilities. When

that occurs, EPA may issue a FIP containing

specific control measures, and to the extent

a proposed FIP would establish control

measures applicable to small entities, EPA

would analyze the small entity impact of

those measures as required by the RFA. In

1994, for example, EPA prepared an initial

regulatory flexibility analysis when it

proposed a FIP for Los Angeles. See 59 FR

23264, May 5, 1994.

As noted above, Congress let the Mid-Tex

interpretation stand when it recently amended

the RFA in enacting SBREFA. If it had

disagreed with the court’s decision, it would

have revised the relevant statutory provisions

or otherwise indicated its disagreement when

it enacted SBREFA. Instead, Congress

actually reinforced the Mid-Tex court’s

interpretation of the RFA in enacting section

212(a) of SBREFA. That section requires that

an agency issue a ‘‘small entity compliance

guide’’ for ‘‘each rule *** for which an

agency is required to prepare a final

regulatory flexibility analysis under section

604’’ of the RFA. The guide is ‘‘to assist

small entities in complying with the rule’’ by

‘‘explain[ing] the actions a small entity is

required to take to comply’’ with the rule

(SBREFA section 212(a)). Obviously, it

makes no sense to prepare a small entity

compliance guide for a rule that does not

apply to small entities. SBREFA thus stands

as further confirmation that Congress

intended regulatory flexibility analyses to

address only rules that establish requirements

small entities must meet. Since SBREFA’s

passage, the United Distribution court has

affirmed the Mid-Tex court’s interpretation.

Some commenters noted that EPA’s

informal panel process did not comply with

the requirements of SBREFA. The EPA did

not convene a SBREFA panel because such

a panel is not required for rules like the

NAAQS that do not apply to small entities.

Under the RFA as amended by SBREFA,

since the Agency certified the proposal, it was

not required to convene a panel for it.

Nevertheless, EPA conducted the voluntary
Federal Register / Vol. 62, No. 138 / Friday, July 18, 1997 / Prepublication 33

66 As commenters pointed out, the RIA for the proposed

PM NAAQS does state that ‘‘[t]he screening analysis ***

provides enough information for an initial regulatory

flexibility analysis (RFA) if such an analysis were to be

done.’’ That statement was mistaken and was not made

in the RIA for the proposed ozone NAAQS. While both

RIAs attempted to gauge the potential impact on small

entities of State implementation of the proposed NAAQS,

neither could or did identify any specific control or

information requirements contained in the NAAQS rule

that would apply to small entities. Indeed, both RIAs made

clear that the impact being analyzed was that of potential

State measures to attain the NAAQS, and that such an

analysis was inherently speculative and uncertain. Thus,

the RIAs actually confirm EPA’s statement in the

preambles for the proposed NAAQS that conducting a

complete regulatory flexibility analysis is not feasible for

rules setting or revising a NAAQS.

panel process described above, as well as

other voluntary small business outreach

efforts. The process could not comply with

the analytical requirements of the RFA for the

reasons given above. However, it could and

did ensure that EPA heard directly from small

entities about the NAAQS proposals.

A few commenters stated that EPA’s view

of the NAAQS and the RFA is inconsistent

with EPA’s past positions regarding the RFA

and NAAQS revisions. Some commenters

also cited the Regulatory Impact Analysis for

the proposed NAAQS and noted that this

analysis demonstrates EPA’s ability to

estimate the impact of the NAAQS on small

entities, thereby undercutting EPA’s argument

that it is not able to perform a regulatory

flexibility analysis when setting the NAAQS.

Past Federal Register notices make clear

that the nature of the NAAQS makes a

regulatory flexibility analysis inapplicable to

NAAQS rulemakings. For instance, in 1984,

EPA stated that a ‘‘NAAQS for NOx by itself

has no direct impact on small entities.

However, it forces each State to design and

implement control strategies for areas not in

attainment.’’ 49 FR 6866, 6876, February 23,

1984; see also, 50 FR 37484, 37499,

September 13, 1985; 50 FR 25532, 25542,

June 19, 1985 (NAAQS for NO2 do not

impact small entities directly). EPA stated

again in 1987 that the NAAQS ‘‘themselves

do not contain emission limits or other

pollution controls. Rather, such controls are

contained in State implementation plans.’’ 52

FR 24634, 24654, July 1, 1987.

EPA has typically performed an analysis to

assess, to the extent practicable, the potential

impact of retaining or revising the NAAQS

on small entities, depending on possible State

strategies for implementing the NAAQS.

These analyses have provided as much insight

into the potential small entity impacts of

implementing revised NAAQS as could be

provided at the NAAQS rulemaking stage. In

some instances, these preliminary ‘‘analyses’’

were described as ‘‘regulatory flexibility

analys[es]’’ or as analyses ‘‘pursuant to this

[Regulatory Flexibility] Act.’’ See, e.g., 52

FR 24634, 24654, July 1, 1987; 50 FR 37484,

37499, September 13, 1985.

However, these analyses were based on

hypothetical State control strategies, and EPA

made the point on various occasions that any

conclusions to be drawn from such analyses

were ‘‘speculative,’’ given that the NAAQS

themselves do not impose requirements on

small entities. Although these past analyses

reflected the Agency’s best efforts to evaluate

potential impacts, they were not regulatory

flexibility analyses containing the necessary

elements required by the RFA. These

analyses, for example, did not describe the

‘‘reporting, recordkeeping and other

compliance requirements’’ of the proposed

NAAQS rules that would apply to small

entities, since the NAAQS rules did not apply

to small entities. Nor did they determine how

the proposed NAAQS rules could be eased or

waived for small entities. Such an analysis is

not possible in the case of the NAAQS. To

the extent EPA labeled these analyses

regulatory flexibility analyses in the past, that

label was inappropriate. EPA’s current

practice is to describe such an analysis more

accurately as a ‘‘general analysis of the

potential cost impacts on small entities.’’ See,

e.g., 61 FR 65638, 65669, 65747, December

13, 1996 (current O3 and PM NAAQS

proposals).66 EPA’s analytical approach to

small entity impacts of the NAAQS has thus

remained consistent over time.

One commenter noted that the legislative

history of the RFA suggests that the RFA was

intended to apply to the NAAQS. As noted

previously, EPA’s reading of both the RFA

and SBREFA, based on the language of the

statute as amended and its legislative histories

and applicable caselaw, is that the RFA

requirements at issue do not apply to the

NAAQS. The legislative history cited by the

commenter does not change this conclusion.

In fact, the statement by Senator Culver on

which the commenter relies does not indicate

that the NAAQS should be subject to

regulatory flexibility analyses. Rather,

Senator Culver uses the NAAQS as an

example of the type of standard that agencies

would not change as a result of the

Regulatory Flexibility Act. According to

Senator Culver, Section 606 ‘‘succinctly

states that this bill does not alter the

substantive standard contained in underlying

statutes which defines the agency’s

mandate.’’ 126 Cong. Rec. S 21455 (Aug. 6,

1980) daily ed. After citing CAA section 109,

Senator Culver goes on to describe EPA’s

bubble policy (which addresses the limits on

emissions from a particular facility) as the

type of flexible regulation that agencies

should consider, once EPA has set a NAAQS.

‘‘The important point for purposes of this

discussion is that the ‘bubble concept’, a type

of flexible regulation, in no manner altered

the basic statutory substantive standard of the

EPA *** . No regulatory flexibility analysis

alters the substantive standard otherwise

applicable by law to agency action.’’ Id.

Thus, contrary to the suggestion of the

commenter, Senator Culver’s statement

actually confirms that the time to consider

regulatory flexibility is when regulations

applicable to sources are being established,

not when a NAAQS itself is being set.

Under section 604 of the RFA, whenever

an agency promulgates a final rule under

section 553 of the Administrative Procedure

Act, after being required by that section or

any other law to publish a general notice of

proposed rulemaking (NPRM), the agency is

required to prepare a final regulatory

flexibility analysis. RFA section 605(b)

provides, however, that section 603 (re initial

regulatory flexibility analyses) and section

604 do not apply if the agency certifies that

the rule will not have a significant economic

impact on a substantial number of small

entities and publishes such certification at the

time of publication of the NPRM or at the

time of the final rule.

As noted above, EPA certified today’s rule

at the time of the NPRM. After considering

the public comments on the certification, EPA

continues to believe that today’s rule will not

have a significant economic impact on a

substantial number of small entities for the

reasons explained above and that it therefore

appropriately certified the rule. Further, as

required by the CAA, EPA is promulgating

today’s rule under CAA section 307(d). For

all the foregoing reasons, EPA has not

prepared a final regulatory flexibility analysis

for the rule. The Agency has nonetheless

analyzed in the final RIA for the rule the

potential impact on small entities of

hypothetical State plans for implementing the

NAAQS. The Agency also plans to issue

guidance to the States on reducing the

potential impact on small entities of

implementing the NAAQS.

C. Impact on Reporting Requirements

There are no reporting requirements

directly associated with the finalization of

ambient air quality standards under section

109 of the Act (42 U.S.C. 7409). There are,

however, reporting requirements associated

with related sections of the Act, particularly

sections 107, 110, 160, and 317 (42 U.S.C.

7407, 7410, 7460, and 7617).

D. Unfunded Mandates Reform Act

Title II of the Unfunded Mandates Reform

Act of 1995 (UMRA), Pub. L. 104–4,

establishes requirements for Federal agencies

to assess the effects of their regulatory actions

on State, local, and tribal governments and

the private sector. Under section 202 of the

UMRA, EPA generally must prepare a

written statement, including a cost-benefit

analysis, for proposed and final rules with

‘‘Federal mandates’’ that may result in

expenditures by State, local, and tribal

governments, in the aggregate, or by the

private sector, of $100 million or more in any

one year. This requirement does not apply if

EPA is prohibited by law from considering

section 202 estimates and analyses in

adopting the rule in question. Before

promulgating an EPA rule for which a written

statement is needed, section 205 of the
34 Federal Register / Vol. 62, No. 138 / Friday, July 18, 1997 / Prepublication

67 As noted in Unit VII.B. of this preamble, a NAAQS

rule only establishes a standard of air quality that other

provisions of the Act call on States (or in the case of State

inaction, the Federal government) to achieve by adopting

implementation plans containing specific control measures

for the purpose. Thus, it is questionable whether the

NAAQS itself imposes an enforceable duty and thus

whether it is a significant Federal mandate within the

meaning of UMRA. EPA need not and does not reach this

issue today. For the reasons given in this unit, even if the

NAAQS were determined to be a significant Federal

mandate, EPA does not have any obligations under

sections 202 and 205 of UMRA, and EPA has met any

obligations it would have under section 204 of UMRA.

68 In addition to the estimates and assessments described

in section 202 of UMRA, written statements are also to

include an identification of the Federal law under which

the rule is promulgated (section 202(a)(1) of UMRA) and

a description of outreach efforts under section 204 of

UMRA (section 202(a)(5) of UMRA). Although these

requirements do not apply here because a written statement

is not required under section 202 of UMRA, this preamble

identifies the Federal law under which this rule is being

promulgated and a written statement describing EPA’s

outreach efforts with State, local, and tribal governments

will be placed in the docket.

69 One commenter argued that in reviewing the SO2

NAAQS, EPA determined that it need not revise the SO2

NAAQS, but could instead pursue an alternative regulatory

program under other authority. This commenter argued that

EPA has similar flexibility in reviewing the PM and Ozone

NAAQS, and thus UMRA requires EPA to identify the

least burdensome alternative (such as retaining the current

NAAQS) as part of that process. As discussed more fully

above at Unit IV of this preamble, EPA does not agree

that it has flexibility to choose such an alternative; nor

does EPA agree with the commenter’s characterization of

the action it took in deciding not to revise the SO2

NAAQS. In fact, in deciding not to revise the SO2

NAAQS, EPA determined, for reasons independent of

section 303 of the Clean Air Act that a NAAQS revision

was not warranted. See 61 FR 25566, 25575, May 22,

1996.

UMRA generally requires EPA to identify

and consider a reasonable number of

regulatory alternatives and adopt the least

costly, most cost-effective, or least

burdensome alternative that achieves the

objectives of the rule. These requirements do

not apply when they are inconsistent with

applicable law. Moreover, section 205 allows

EPA to adopt an alternative other than the

least costly, most cost-effective, or least

burdensome alternative if the Administrator

publishes with the final rule an explanation

of why that alternative was not adopted.

Before EPA establishes any regulatory

requirements that may significantly or

uniquely affect small governments, including

tribal governments, it must have developed

under section 203 of the UMRA a small

government agency plan. The plan must

provide for notifying potentially affected

small governments, enabling officials of

affected small governments to have

meaningful and timely input in the

development of EPA regulatory proposals

with significant Federal intergovernmental

mandates, and informing, educating, and

advising small governments on compliance

with the regulatory requirements. Section 204

of UMRA requires each agency to develop

‘‘an effective process to permit elected

officers of State, local and tribal governments

*** to provide meaningful and timely input’’

in the development of regulatory proposals

containing a significant Federal

intergovernmental mandate.67

The EPA has determined that the

provisions of sections 202 and 205 of the

UMRA do not apply to this decision. ‘‘Unless

otherwise prohibited by law,’’ EPA is to

prepare a written statement under Section 202

of UMRA that is to contain assessments and

estimates of the costs and benefits of a rule

containing a Federal mandate. Congress

clarified that ‘‘unless otherwise prohibited by

law’’ referred to whether an agency was

prohibited from considering the information

in the rulemaking process, not to whether an

agency was prohibited from collecting the

information. The Conference Report on

UMRA states, ‘‘This section [202] does not

require the preparation of any estimate or

analysis if the agency is prohibited by law

from considering the estimate or analysis in

adopting the rule.’’ 141 Cong. Rec. H3063

(daily ed. March 13, 1995). Because the

Clean Air Act prohibits EPA, when setting

the NAAQS, from considering the types of

estimates and assessments described in

section 202, UMRA does not require EPA to

prepare a written statement under section

202.68 The requirements in section 205 do not

apply because those requirements only apply

to rules ‘‘for which a written statement is

required under section 202 ***.’’

The EPA has determined that the

provisions of section 203 of UMRA do not

apply to this decision. Section 203 only

requires the development of a small

government agency plan for requirements

with which small governments might have to

comply. Since setting the NAAQS does not

establish requirements with which small

governments might have to comply, section

203 does not apply. The EPA acknowledges,

however, that any corresponding revisions to

associated State implementation plan

requirements and air quality surveillance

requirements, 40 CFR part 51 and 40 CFR

part 58, respectively, might result in such

effects. Accordingly, EPA will address

unfunded mandates as appropriate when it

proposes any revisions to 40 CFR parts 51

and 58.

With regard to the outreach described in

UMRA section 204, EPA did follow a

process for providing elected officials with an

opportunity for meaningful and timely input

into the proposed NAAQS revisions, although

EPA did not describe this process in the

proposal. The EPA conducted a series of preproposal outreach meetings with State and

local officials and their representatives that

permitted these officials to provide

meaningful and timely input on issues related

to the NAAQS and the monitoring issues

associated with them. Beginning in January,

1996, EPA briefed State and local air

pollution control officials at national meetings

with State and Territorial Air Pollution

Program Administrators (STAPPA)/

Association of Local Air Pollution Control

Officials (ALAPCO) in Washington DC,

North Carolina, Chicago and Nevada. The

EPA also held briefings for the Washington

DC representatives of several State and local

organizations, including National Conference

of State Legislators, U.S. Conference of

Mayors, National Governors Association, and

National League of Cities, and STAPPA/

ALAPCO. EPA also held separate briefings

and discussions with State and local officials

at meetings set up by the National Governors

Association, the U.S. Conference of Mayors

and the Council of State Governments. The

EPA also conducted in-depth briefings at

each EPA regional office and regional staff

also had several meetings and discussions

with their State counterparts about the

standards. The efforts described above, which

provided elected officials with opportunity for

meaningful and timely input into the

proposed NAAQS revisions, met any

requirements imposed by section 204. The

docket will contain a written statement

describing these outreach efforts, including a

summary of the comments and concerns

presented by State, local, and tribal

governments and a summary of EPA’s

evaluation of those comments and concerns.

Several commenters disagreed with EPA

that UMRA sections 202, 203 and 205 do not

apply to this decision. These commenters

argued that EPA is not prohibited from

considering costs in setting NAAQS under

the Clean Air Act and applicable judicial

decisions. Some commenters also expressed

the view that there is no conflict between

UMRA and the Clean Air Act with regard to

the NAAQS. These commenters argued that

UMRA and the NAAQS can be

‘‘harmonized’’ by reading UMRA as an

information gathering statute and that EPA

should therefore perform the analyses

required by UMRA, regardless of whether

costs may be considered. Finally, at least one

commenter argued that in past NAAQS

reviews, EPA did not dispute its UMRA

obligations.

As discussed more fully in Unit IV of this

preamble, EPA is prohibited from considering

cost in setting the NAAQS. Given that fact

(as noted in Unit IV preamble), sections 202

and 205 do not apply.69 As the Conference

Report clarifies, UMRA itself states that the

section 202 estimates and analyses are not

required in cases such as the NAAQS, where

an agency is prohibited by law from

considering section 202 estimates and

analyses. Reading UMRA in the manner

suggested by the commenters would

effectively read this provision out of UMRA;

UMRA contains an exception for rules like

the NAAQS, it must be given effect.

With regard to EPA’s position regarding

UMRA in previous NAAQS review exercises,

EPA simply made plain in those situations

that because it did not plan on revising the

NAAQS, it determined, without further
Federal Register / Vol. 62, No. 138 / Friday, July 18, 1997 / Prepublication 35

review, that UMRA sections 202, 203 and

205 did not apply. EPA thus stated that:

Because the Administrator has decided not to

revise the existing primary NAAQS for SO2, this

action will not impose any new expenditures on

governments or on the private sector, or establish

any new regulatory requirements affecting small

governments. Accordingly, EPA has determined

that the provisions of section 202, 203 and 205 do

not apply to this final decision.

61 FR 25566, 25577, May 22, 1996; See also

61 FR 52852, 52856, October 8, 1996 (Same

statement for NO2 NAAQS). As this

statement makes clear, EPA only determined

that UMRA sections 202, 203 and 205 did not

apply to the NAAQS when EPA fails to

revise the standard. Having made that

determination, EPA had no reason to

catalogue additional bases for finding UMRA

inapplicable. Nothing in that statement was

intended to preclude EPA, or precludes EPA,

from concluding for other reasons (such as

those discussed above) that UMRA also does

not apply when EPA in fact revises an

applicable NAAQS.

E. Environmental Justice

Executive Order 12848 requires that each

Federal agency make achieving

environmental justice part of its mission by

identifying and addressing, as appropriate,

disproportionately high and adverse human

health or environmental effects of its

programs, policies, and activities on

minorities and low-income populations. These

requirements have been addressed to the

extent practicable in the RIA cited above.

F. Submission to Congress and the

Comptroller General

Under 5 U.S.C. 801(a)(1)(A), as added by

the Small Business Regulatory Enforcement

Fairness Act of 1996 (SBREFA), EPA

submitted a report containing this rule and

other required information to the U.S. Senate,

the U.S. House of Representatives, and the

Comptroller General of the United States

prior to publication of the rule in today’s

Federal Register. This rule is a ‘‘major rule’’

for purposes of SBREFA.

VIII. Response to Petition for

Administrator Browner’s Recusal

On March 13, 1997, the Washington Legal

Foundation (WLF), filed a petition with EPA

asking that I, Carol Browner, disqualify

myself in rulemaking regarding the NAAQS

for PM and O3. The petition claims that my

public statements indicate a ‘‘clear and

convincing showing’’ that I had ‘‘already

decided to revise the NAAQS for PM and

ozone’’ and that I therefore ‘‘could not give

meaningful consideration’’ to comments

adverse to the proposed rule. On May 12,

1997, EPA’s General Counsel, Jonathan Z.

Cannon, sent a letter to WLF regarding the

petition. This letter and the WLF petition

were then placed in the dockets for the

proposed O3 and PM standards pending

‘‘consideration and final response in

connection with the Agency’s final actions.’’

Contrary to WLF’s assertions, I have

maintained an open mind throughout these

proceedings, and have based today’s

decisions on the rulemaking record—

including consideration of comments opposed

to the proposal. The law does not require the

Administrator of EPA to disqualify herself

merely for expressing views on a proposed

regulation; in fact, it is part of my

responsibility to engage in the public debate

on the proposals. Moreover, the assertions in

WLF’s petition do not accurately represent

my views. The petition takes quotes out of

context and repeatedly misinterprets my

statements. For example, WLF quotes a

statement that I made at the Children’s

Environmental Health Network Research

Conference as an indication that I had

‘‘prejudged the issue.’’ However, my

statement that ‘‘I will not be swayed’’ did not

refer to adopting the NAAQS as proposed.

Instead, as is clear from reviewing the entire

speech, I was addressing my broader concern

about children’s health and the range of EPA

standards affecting children’s health. I also

appeared at several congressional hearings

and testified before members of Congress,

some of whom were strongly opposed to the

proposals. At those hearings, I explained the

basis for the proposals and put forward the

reasons why I concluded the proposals were

appropriate, given the information before me

at the time. At the same time, I made clear

that I took very seriously my obligation to

keep an open mind, and to consider fully and

fairly all significant comments that the

Agency received. For these reasons and

others, as set forth in Mr. Cannon’s May 12,

1997 response to WLF, which I adopt in full,

I have decided not to recuse myself from any

aspect of considering revisions to the

NAAQS for O3 and PM. Accordingly, I am

hereby denying WLF’s petition.

IX. References

(1) American Thoracic Society. (1985)

Guidelines as to what constitutes an adverse

respiratory health effect, with special reference to

epidemiologic studies of air pollution. American

Review of Respiratory Disease.. 131: 666–668.

(2) Freas (1996) Ambient air quality

relationships among alternative ozone air quality

standards. Internal memorandum from Warren P.

Freas to file, U.S. EPA, EMAD/OAQPS/OAR,

RTP, NC, dated October 30, 1996. Docket No. A–

95–58 Item II–B–6.

(3) Freas (1997) Ambient air quality

relationships for counties meeting alternative air

quality standards. Internal memorandum from

Warren P. Freas to file, U.S. EPA, EMAD/OAQPS/

OAR, RTP, NC, dated July 1, 1997. Docket No.

A–95–58 Item xxx.

(4) Heck, Walter W. And Ellis B. Cowling.

January, 1997. EM Journal. ‘‘The Need for a Long

Term Cumulative Secondary Ozone Standard - An

Ecological Perspective.’’ Air and Waste

Management Association, Pittsburgh, PA.; pp. 23–

33.

(5) Johnson, T; Capel, J.; Mozier, J.; McCoy, M.

(1996a) Estimation of ozone exposures experienced

by outdoor children in nine urban areas using a

probabilistic version of NEM. Prepared by IT/Air

Quality Services for U.S. EPA, OAQPS; Research

Triangle Park, NC, August.

(6) Johnson, T.; Capel, J.; McCoy, M.; Mozier,

J. (1996b) Estimation of ozone exposures

experienced by outdoor workers in nine urban areas

using a probabilistic version of NEM. Prepared by

IT/Air Quality Services for U.S. EPA, OAQPS;

Research Triangle Park, NC, August.

(7) McClellan, R. O., (1989) Letter from

Chairman of Clean Air Scientific Advisory

Committee to the EPA Administrator, dated May

1, 1989. EPA–SAB-CASAC-LTR–89–019.

(8) Richmond (1997) Supplemental ozone

exposure and health risk analyses. Internal

memorandum from Harvey M. Richmond to Karen

M. Martin, U.S. EPA, AQSSD/OAQPS/OAR, RTP,

NC, dated February 11, 1997. Docket No. A–95–

58 Item IV–A–1.

(9) Seitz (1996) Revocation date for the existing

1–hour ozone standards. Internal memorandum

from John S. Seitz to Mary D. Nichols, U.S. EPA,

OAQPS/OAR, RTP, NC, dated November 20,

1996. Docket No. A–95–59 Item II–B–3.

(10) Thurston, G.D.; Ito, K.; Kinney, P.L.;

Lippmann, M. (1992) A multi-year study of air

pollution and respiratory hospital admissions in

three New York State metropolitan areas: results

for 1988 and 1989 summers. Journal of Exposure

Analysis and Environmental Epidemiology. 2:429–

450.

(11) U.S. Department of Health and Human

Services (1996) Vital and health statistics: current

estimates from the national health interview survey,

1994. Hyattsville, MD: Public Health Service,

National Center for Health Statistics; DHHS

publication no. (PHS) 96–278.

(12) U.S. Environmental Protection Agency

(1996a) Air quality criteria for Ozone and related

photochemical oxidants. Research Triangle Park,

NC: Office of Health and Environmental

Assessment, Environmental Criteria and

Assessment Office; EPA report nos. EPA/600/AP–

93/004a–c.

(13) U.S. Environmental Protection Agency

(1996b) Review of the national ambient air quality

standards for ozone: assessment of scientific and

technical information. OAQPS staff paper.

Research Triangle Park, NC: Office of Air Quality

Planning and Standards; EPA report no. EPA–452/

R–96–007. Available from: NTIS, Springfield, VA;

PB96–203435.

(14) Whitfield, R.G.; Biller, W.F.; Jusko, M.J.;

Keisler, J.M. (1996) A probabilistic assessment of

health risks associated with short-term exposure to

tropospheric ozone. Report prepared for U.S. EPA,

OAQPS. Argonne National Laboratory; Argonne,

IL, June. (For copies, contact Harvey M.

Richmond, U.S. Environmental Protection Agency,

OAQPS, MD–15, Research Triangle Park, N.C.

27711, (919) 541–5271.)

(15) Wolff, G. T., (1995a) Letter from Chairman

of Clean Air Scientific Advisory Committee to the

EPA Administrator, dated November 28, 1995.

EPA–SAB–CASAC–LTR–96–001.

(16) Wolff, G. T., (1995b) Letter from Chairman

of Clean Air Scientific Advisory Committee to the

EPA Administrator, dated November 30, 1995.

EPA–SAB–CASAC–LTR–96–002.

(17) Wolff, G. T., (1996) Letter from Chairman

of Clean Air Scientific Advisory Committee to the

EPA Administrator, dated April 4, 1996. EPA–

SAB–CASAC–LTR–96–006.
36 Federal Register / Vol. 62, No. 138 / Friday, July 18, 1997 / Prepublication

List of Subjects in 40 CFR Part 50

Environmental protection, Air pollution

control, Carbon monoxide, Lead, Nitrogen

dioxide, Ozone, Particulate matter, Sulfur

oxides.

Dated: July 16, 1997.

Carol M. Browner,

Administrator.

Therefore, for the reasons set forth in the

preamble, title 40, chapter I, part 50 of the

Code of Federal Regulations is amended as

follows:

PART 50—NATIONAL PRIMARY AND

SECONDARY AMBIENT AIR QUALITY

STANDARDS

1. The authority citation for part 50

continues to read as follows:

Authority: Secs. 109 and 301(a), Clean Air Act,

as amended (42 U.S.C. 7409, 7601(a)).

2. Section 50.9 is revised to read as

follows:

§ 50.9 National 1–hour primary and

secondary ambient air quality standards for

ozone.

(a) The level of the national 1-hour primary

and secondary ambient air quality standards

for ozone measured by a reference method

based on Appendix D to this part and

designated in accordance with part 53 of this

chapter, is 0.12 parts per million (235 μg/m3).

The standard is attained when the expected

number of days per calendar year with

maximum hourly average concentrations

above 0.12 parts per million (235 μg/m3) is

equal to or less than 1, as determined by

Appendix H to this part.

(b) The 1–hour standards set forth in this

section will no longer apply to an area once

EPA determines that the area has air quality

meeting the 1–hour standard. Area

designations are codified in 40 CFR part 81.

3. Section 50.10 is added to read as

follows:

§ 50.10 National 8–hour primary and

secondary ambient air quality standards for

ozone.

(a) The level of the national 8–hour

primary and secondary ambient air quality

standards for ozone, measured by a reference

method based on Appendix D to this part and

designated in accordance with part 53 of this

chapter, is 0.08 parts per million (ppm), daily

maximum 8–hour average.

(b) The 8–hour primary and secondary

ozone ambient air quality standards are met

at an ambient air quality monitoring site when

the average of the annual fourth-highest daily

maximum 8–hour average ozone

concentration is less than or equal to 0.08

ppm, as determined in accordance with

Appendix I to this part.

4. Appendix D is amended by revising

references 8 and 9 and by removing all of the

text and figures immediately following

‘‘Figure 2, Schematic Diagram of a Typical

UV Photometric Calibration System (Option

1), through the end of Appendix D.

Appendix D to Part 50—Measurement

Principle and Calibration Procedure for

the Measurement of Ozone in the

Atmosphere

*****

6. References.

*****

8. Transfer Standards for Calibration of Ambient

Air Monitoring Analyzers for Ozone, EPA

publication number EPA–600/4–79–056, EPA,

National Exposure Research Laboratory,

Department E, (MD–77B), Research Triangle Park,

NC 27711.

9. Technical Assistance Document for the

Calibration of Ambient Ozone Monitors, EPA

publication number EPA–600/4–79–057, EPA,

National Exposure Research Laboratory,

Department E, (MD–77B), Research Triangle Park,

NC 27711.

*****

Appendix E [Removed and Reserved]

5. Appendix E is removed and reserved.

6. Appendix H is amended by revising the

appendix heading to read ‘‘Appendix H To

Part 50—Interpretation of The 1-Hour

Primary and Secondary National Ambient Air

Quality Standards for Ozone’’.

7. Appendix I is added to read as follows:

Appendix I to Part 50—Interpretation of

the 8–Hour Primary and Secondary

National Ambient Air Quality

Standards for Ozone

1. General.

This appendix explains the data handling

conventions and computations necessary for

determining whether the national 8–hour primary

and secondary ambient air quality standards for

ozone specified in § 50.10 are met at an ambient

ozone air quality monitoring site. Ozone is

measured in the ambient air by a reference method

based on Appendix D of this part. Data reporting,

data handling, and computation procedures to be

used in making comparisons between reported

ozone concentrations and the level of the ozone

standard are specified in the following sections.

Whether to exclude, retain, or make adjustments to

the data affected by stratospheric ozone intrusion

or other natural events is subject to the approval

of the appropriate Regional Administrator.

2. Primary and Secondary Ambient Air Quality

Standards for Ozone.

2.1 Data Reporting and Handling Conventions.

2.1.1 Computing 8–hour averages. Hourly

average concentrations shall be reported in parts

per million (ppm) to the third decimal place, with

additional digits to the right being truncated.

Running 8–hour averages shall be computed from

the hourly ozone concentration data for each hour

of the year and the result shall be stored in the first,

or start, hour of the 8–hour period. An 8–hour

average shall be considered valid if at least 75%

of the hourly averages for the 8–hour period are

available. In the event that only 6 (or 7) hourly

averages are available, the 8–hour average shall be

computed on the basis of the hours available using

6 (or 7) as the divisor. (8–hour periods with three

or more missing hours shall not be ignored if, after

substituting one-half the minimum detectable limit

for the missing hourly concentrations, the 8–hour

average concentration is greater than the level of

the standard.) The computed 8–hour average ozone

concentrations shall be reported to three decimal

places (the insignificant digits to the right of the

third decimal place are truncated, consistent with

the data handling procedures for the reported data.)

2.1.2 Daily maximum 8–hour average

concentrations. (a) There are 24 possible running

8–hour average ozone concentrations for each

calendar day during the ozone monitoring season.

(Ozone monitoring seasons vary by geographic

location as designated in part 58, Appendix D to

this chapter.) The daily maximum 8–hour

concentration for a given calendar day is the

highest of the 24 possible 8–hour average

concentrations computed for that day. This process

is repeated, yielding a daily maximum 8–hour

average ozone concentration for each calendar day

with ambient ozone monitoring data. Because the

8–hour averages are recorded in the start hour, the

daily maximum 8–hour concentrations from two

consecutive days may have some hourly

concentrations in common. Generally, overlapping

daily maximum 8–hour averages are not likely,

except in those non–urban monitoring locations

with less pronounced diurnal variation in hourly

concentrations.

(b) An ozone monitoring day shall be counted

as a valid day if valid 8–hour averages are available

for at least 75% of possible hours in the day (i.e.,

at least 18 of the 24 averages). In the event that

less than 75% of the 8–hour averages are available,

a day shall also be counted as a valid day if the

daily maximum 8–hour average concentration for

that day is greater than the level of the ambient

standard.

2.2 Primary and Secondary Standard-related

Summary Statistic. The standard-related summary

statistic is the annual fourth-highest daily maximum

8–hour ozone concentration, expressed in parts per

million, averaged over three years. The 3–year

average shall be computed using the three most

recent, consecutive calendar years of monitoring

data meeting the data completeness requirements

described in this appendix. The computed 3–year

average of the annual fourth-highest daily

maximum 8–hour average ozone concentrations

shall be expressed to three decimal places (the

remaining digits to the right are truncated.)

2.3 Comparisons with the Primary and

Secondary Ozone Standards. (a) The primary and

secondary ozone ambient air quality standards are

met at an ambient air quality monitoring site when

the 3–year average of the annual fourth-highest

daily maximum 8–hour average ozone

concentration is less than or equal to 0.08 ppm. The

number of significant figures in the level of the

standard dictates the rounding convention for

comparing the computed 3–year average annual

fourth-highest daily maximum 8–hour average

ozone concentration with the level of the standard.

The third decimal place of the computed value is

rounded, with values equal to or greater than 5

rounding up. Thus, a computed 3–year average

ozone concentration of 0.085 ppm is the smallest

value that is greater than 0.08 ppm.

(b) This comparison shall be based on three

consecutive, complete calendar years of air quality

monitoring data. This requirement is met for the

three year period at a monitoring site if daily

maximum 8–hour average concentrations are
Federal Register / Vol. 62, No. 138 / Friday, July 18, 1997 / Prepublication 37

available for at least 90%, on average, of the days

during the designated ozone monitoring season,

with a minimum data completeness in any one year

of at least 75% of the designated sampling days.

When computing whether the minimum data

completeness requirements have been met,

meteorological or ambient data may be sufficient

to demonstrate that meteorological conditions on

missing days were not conducive to concentrations

above the level of the standard. Missing days

assumed less than the level of the standard are

counted for the purpose of meeting the data

completeness requirement, subject to the approval

of the appropriate Regional Administrator.

(c) Years with concentrations greater than the

level of the standard shall not be ignored on the

ground that they have less than complete data.

Thus, in computing the 3–year average fourth

maximum concentration, calendar years with less

than 75% data completeness shall be included in

the computation if the average annual fourth

maximum 8–hour concentration is greater than the

level of the standard.

(d) Comparisons with the primary and secondary

ozone standards are demonstrated by examples 1

and 2 in paragraphs (d)(1) and (d) (2) respectively

as follows:

(1) As shown in example 1, the primary and

secondary standards are met at this monitoring site

because the 3–year average of the annual fourthhighest daily maximum 8–hour average ozone

concentrations (i.e., 0.084 ppm) is less than or

equal to 0.08 ppm. The data completeness

requirement is also met because the average percent

of days with valid ambient monitoring data is

greater than 90%, and no single year has less than

75% data completeness.

EXAMPLE 1. AMBIENT MONITORING SITE ATTAINING THE PRIMARY AND SECONDARY OZONE STANDARDS

Year Percent

Valid Days

1st Highest

Daily Max

8–hour

Conc. (ppm)

2nd Highest

Daily Max

8–hour

Conc. (ppm)

3rd Highest

Daily Max

8–hour

Conc. (ppm)

4th Highest

Daily Max

8–hour

Conc. (ppm)

5th Highest

Daily Max

8–hour

Conc. (ppm)

1993 .................................................................................. 100% 0.092 0.091 0.090 0.088 0.085

1994 .................................................................................. 96% 0.090 0.089 0.086 0.084 0.080

1995 .................................................................................. 98% 0.087 0.085 0.083 0.080 0.075

Average ..................................................................... 98% 0.084

(2) As shown in example 2, the primary and

secondary standards are not met at this monitoring

site because the 3–year average of the fourthhighest daily maximum 8–hour average ozone

concentrations (i.e., 0.093 ppm) is greater than 0.08

ppm. Note that the ozone concentration data for

1994 is used in these computations, even though

the data capture is less than 75%, because the

average fourth-highest daily maximum 8–hour

average concentration is greater than 0.08 ppm.

EXAMPLE 2. AMBIENT MONITORING SITE FAILING TO MEET THE PRIMARY AND SECONDARY OZONE STANDARDS

Year Percent

Valid Days

1st Highest

Daily Max

8–hour

Conc. (ppm)

2nd Highest

Daily Max

8–hour

Conc. (ppm)

3rd Highest

Daily Max

8–hour

Conc. (ppm)

4th Highest

Daily Max

8–hour

Conc. (ppm)

5th Highest

Daily Max

8–hour

Conc. (ppm)

1993 .................................................................................. 96% 0.105 0.103 0.103 0.102 0.102

1994 .................................................................................. 74% 0.090 0.085 0.082 0.080 0.078

1995 .................................................................................. 98% 0.103 0.101 0.101 0.097 0.095

Average ..................................................................... 89% 0.093

3. Design Values for Primary and Secondary

Ambient Air Quality Standards for Ozone.

The air quality design value at a monitoring site

is defined as that concentration that when reduced

to the level of the standard ensures that the site

meets the standard. For a concentration-based

standard, the air quality design value is simply the

standard-related test statistic. Thus, for the primary

and secondary ozone standards, the 3–year average

annual fourth-highest daily maximum 8–hour

average ozone concentration is also the air quality

design value for the site.

[FR Doc. 97–18580 Filed 7–17–97; 8:45 am]

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