AIM

38855

Friday

July 18, 1997

Part V

Environmental

Protection Agency

40 CFR Part 50

National Ambient Air Quality Standards

for Ozone; Final Rule

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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 (03) based on its review of the

available scientific evidence linking

exposures to ambient 03 to adverse

health and welfare effects at levels

allowed by the current 03 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 03

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 03-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

03-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 03 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 03 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; e-mail:

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 03 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 03:

Assessment of Scientific and Technical

Information ("Staff Paper")(EPA-452/R96-007, 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 03 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 03

D. Summary of Proposed Revisions to the

03 Standards

II. Rationale for the Primary 03 Standard

A. Introduction

B. Elements of the Primary Standard

C. Communication of Public Health

Information

III. Rationale for the Secondary 03 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

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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 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 ofuncertainties

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 well-being."

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 03

The last review of 03 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-expectedexceedance 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 03 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 03:

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.

1A more complete history of the 03 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 03:

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.

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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 03

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 03 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 03 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 03 (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 03,

and solicited public comments on

alternative primary and secondary

standards and on the proposed forms of

the standards.

To ensure the broadest possible

public input on the 03 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 03 and PM NAAQS, and on related

notices dealing with the implementation

of revised 03 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 03 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 03

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 03

and related photochemical oxidants is

on public health and welfare effects

associated with exposure to ambient

levels of tropospheric 03. Tropospheric

03 is chemically identical to

stratospheric 03, which is produced

miles above the earth's surface and

provides a protective shield from excess

ultraviolet radiation. In contrast,

tropospheric 03 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

(NO.), 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 03

can be found in the Criteria Document

and in the Staff Paper.

D. Summary of Proposed Revisions to

the 03 Standards

For reasons discussed in the proposal,

the Administrator proposed to replace

the current 1-hour primary standard for

03 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 03

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 03 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 03 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.

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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

03 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 03, 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 03 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 03

concentrations measured at each

monitor within an area.

As discussed more fully below in this

unit, the rationale for the final decision

regarding the 03 primary NAAQS

includes consideration of:

(1) Health effects information to

inform judgments as to the likelihood

that exposures to ambient 03 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 03

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.I.),

level (Unit II.B.2.), and form (Unit

II.B.3.). Finally, the related subject of

the communication of 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 03

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 03, 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 03

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 03 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

(I to 3 hours), prolonged (6 to 8 hours),

and long-term (months to years)

exposures to 03.

Acute health effects 3 are induced by

short-term exposures to 03 (observed at

concentrations as low as 0.12 ppm),

generally while individuals are engaged

in moderate or heavy exertion, and by

prolonged exposures to 03 (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 03 was completed, such

acute health effects have been observed

following prolonged exposures at

moderate levels of exertion at

concentrations of 03 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 03 and may

experience much greater functional and

symptomatic effects from exposure to 03

than the average individual.

With regard to chronic health effects 4 ,

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 03-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 03 over a lifetime may result in

sufficient damage to respiratory tissue

such that individuals later in life may

experience a reduced quality of life,

3 "Acute health effects" of 03 are defined as those

effects induced by short-term and prolonged

exposures to 03. Examples of these effects are

functional, symptomatic, biochemical, and

physiologic changes.

4 "Chronic health effects" of 03 are defined as

those effects induced by long-term exposures to 02.

Examples of these effects are structural damage to

lung tissue and accelerated decline in baseline lung

function.

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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 03 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 03 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

(FEV)] 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 03 exposures and related risks

for the general population and two atrisk 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 atrisk groups likely to experience 03-

related adverse effects, the estimated

number of occurrences of such effects,

and the estimated number of people

who would experience exposures of

concern 5 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 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

concentration-response information was

available from studies evaluated in the

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.

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 risk 6 . 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 03 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 03

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 risks 7 for the

6 This study is one of several studies, mainly

conducted in the northeastern portion of the United

States and southeastern Canada, reporting excess

daily respiratory-related hospital admissions

associated with elevated 03 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

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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 03,

the Administrator must specify:

Averaging time, 03 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 03; 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

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 03 concentrations upon

attainment of alternative standards.

9 This review focused only on a standard for 03,

as the most appropriate surrogate for photochemical

oxidants.

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 (concentrationbased forms that generally allow for I 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 i-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 i-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 i-hour averaging time reduces

the risk of experiencing health effects

associated with both i-hour and 8-hour

exposures. Likewise, attaining an 8-

hour standard reduces the risk of

experiencing health effects associated

with both 8-hour and i-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 i-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 03 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 longterm (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

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 03 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 03

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 03 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

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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 health-based

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 ppm' 0 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." 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

10 More precisely, exposures at and above 0.08

ppm refers to estimates of exposures to 03

concentrations > 0.081 ppm from the exposure

assessment.

11 In terms of the percent of outdoor children

estimated to be exposed to 03 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.

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

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

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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 i-hour standard with an 8-hour

standard, but favored instead both 8-

hour and i-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 i-hour exposures of

concern, or that the retention of the

current i-hour standard was critical to

maintaining current pollution control

measures. As an initial matter, EPA is

delaying revocation of the i-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 i-hour exposures

of concern, at and above 0.12 ppm,' 2

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 i-hour exposures, and

generally even more effective in limiting

i-hour exposures of concern than is the

current i-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 i-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 i-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 i-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 03 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

03 standard at 0.08 ppm, and to solicit

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).

comment on alternative levels,

necessarily reflected a recognition, as

emphasized by CASAC, that it is likely

that "03 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 standardsetting 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 03

criteria and standards, CASAC

concluded that the existing 1-hour

standard set at 0.12 ppm 03 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 03.

Regarding currently available

evidence of (3-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 03 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 03, at moderate

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exertion: lung function decrements,

respiratory symptoms (e.g., cough, pain

on deep inspiration), nonspecific

bronchial responsiveness, and

biochemical indicators of pulmonary

inflammation. Field studies provide

evidence of similar functional and

symptomatic effects at ambient 03

exposures that are consistent with the

clinical findings. Laboratory animal

studies provide supporting evidence of

03-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 03 exposures, including 03

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 03 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 03

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

03 levels result in similar chronic health

effects in humans.

Regarding the types and severity of

03-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

03-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

03 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

03 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 asthmarelated mortality and hospitalizations,

especially among children in general

and black children in particular. While

03 has not been shown to cause asthma,

the available evidence suggests that 03

may exacerbate asthma. Accordingly,

the Administrator judged that repeated

exposures to 03 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-expectedexceedances' 3 ) as compared to the

13 The upper end of this range, 3-expectedexceedances, was based on air quality comparisons,

since risk estimates were only available at the time

ofproposal for the 1 and 5-expected -exceedance

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 03 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 03

season.

(11) Estimated exposures to 03

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-expectedexceedance 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

forms of a 0.09 ppm standard. This range is

consistent with the results of the updated risk

assessment.

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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 03

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 03 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.

(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 03 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 03 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 thirdhighest 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 03 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

percentages 14 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 combined 15 are as

follows:

(2) For moderate lung function (FEVI)

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 (FEVI)

decreases > 20 percent, approximately 2

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-expected -exceedance forms of

the standards.

15 Approximately 3.1 million outdoor children

reside in these nine urban areas.

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 underpredict 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

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various types of health effects studies

that have related 03 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 03; some exposure

chambers using artificially generated 03

may have been contaminated with other

pollutants that could have accounted for

some of the observed effects; and

responses to elevated 03 levels were

compared to responses to air with

essentially no 03 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 nonbackground levels of ambient 03 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 03 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 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 03-related effects at

and below 03 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 03 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 03 concentrations that have

historically been observed in areas

implementing control programs

designed to attain the 03 NAAQS. The

EPA recognizes that future changes in

air quality distributions are areaspecific, 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 assessment 6 , 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

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.

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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

03 concentrations than the vast majority

of areas in which 03 is monitored' 7

, 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

concentration-response functions for 03.

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

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.

concentration in calculating risks

attributable to non-background sources

of 03. 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 03, 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 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 concentrationresponse 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.I. 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 03-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 03 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 03, that

have no discernible thresholds for

health effects, no standard can be riskfree. 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

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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 03 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 03-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 03-induced effects,

including respiratory-related 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 03-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 long-term 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 0.08 ppm, specifically after

considering a range of alternative

standards that included 0.07 ppm.

(2) The most certain 03-related effects,

while judged to be adverse, are transient

and reversible (particularly at 03

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 long-term medical significance

of these effects.

18 The EPA anticipates that additional people

would be protected through regional measures

adopted for purposes ofan 8 hour, 0.08 ppm

standard.

(3) As many commenters have noted,

based on information in the Criteria

Document with regard to ambient

concentrations of 03 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 03

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 "-

expected -exceedance" form. That is, the

current standard is based on the

expected 19 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 03 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.1 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

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.

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allow for multiple (up to five) expected

exceedances per year, averaged over 3

years. A multiple-exceedance 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 03 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-expectedexceedance 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 fifth-highest

concentration, and either an

exceedance-based or a concentrationbased form. As discussed in the

proposal, in considering possible forms

within the range of 1 to 5 exceedances

(or their concentration -based

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 03

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-expectedexceedance 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

standard2 , and the magnitude of peak

8-hour average 03 concentrations 2 2 that

would occur in such areas. 2 3 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 03 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 03 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

concentration-based 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 03 concentrations that are

associated with health effects. That is,

given that there is a continuum of

effects associated with exposures to

varying levels of 03, the extent to which

public health is affected by exposure to

ambient 03 is related to the actual

magnitude of the 03 concentration, not

just whether the concentration is above

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 -expected -exceedance 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-expectedexceedance 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 03 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.

a specified level. With an exceedancebased form, days on which the ambient

03 concentration is well above the level

of the standard are given equal weight

to those days on which the 03

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 03 concentrations occur

would weigh proportionally more than

days with lower 03 concentrations,

since the actual concentrations are used

directly in determining whether the

standard is attained. A concentrationbased 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

fifth-highest concentration-based forms,

aid in comparing the differences in

public health protection among

alternative concentration-based 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 (FEV)

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;

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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 -exceed ance 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 concentrationbased 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 third-highest 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

third-highest concentration form. Some

commenters seem to view such air

quality comparisons, particularly with

regard to pollutants such as 03 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 fifth-highest 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 03-related risks to

public health associated with acute

effects (i.e., those resulting from shortterm 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 03 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 03 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 03 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 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 fifth-highest

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 03 standard, and

that selection from within this range is

a policy judgment that cannot be based

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on science alone. This advice reflects

CASAC's recognition that 03 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 fifth-highest

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

second- to 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 secondto fifth-highest 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 fourthhighest concentration standard would

be significantly more restrictive than a

fifth-highest 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 fifth-highest

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 fifth-highest concentration

forms provide protection against the

more serious, but less certain effects that

have been associated with exposure to

03, including potential chronic effects,

cannot be quantitatively assessed at this

time. Given that all such forms would

result in significant reductions in

exposures to 03 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 03

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 03

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 03 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 03 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 03

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

second- to 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 03 peaks above a

benchmark level of 0.09 ppm even when

attaining a fifth-highest concentration

standard and the number of days on

which the level of a fifth-highest

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.I. 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

fourth-highest 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,

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1997). This number of exceedances is

clearly within the range of multiple

exceedances that CASACjudged to be

appropriate for a health-based primary

03 standard. Thus, in the

Administrator's judgment, based on the

information currently available, an 8-

hour, 0.08 ppm standard with a fourthhighest 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 03 concentrations in an area to

determine whether the primary standard

for 03 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 03 standard is based on

controlled human exposure studies that

relate known 03 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 03

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 03

data would be acceptable. Such criteria

would be important since 03 air quality

concentrations can vary significantly

across most urban areas. The lowest

concentrations typically occur in the

urban center and in locations near 03

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 03 concentrations

of concern would be an important

consideration. Unless the 03

concentration gradients within each

spatial averaging zone were relatively

homogeneous, there may be significant

numbers of sensitive individuals

exposed to high 03 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 03

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 03,

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 03 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 03 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 03 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 03 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 03

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 03

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 03 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 03

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 03 variations to ensure

adequate protection of these

populations from localized 03

concentrations. Thus, the revised 03

standard will maintain the current

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approach of using air quality data from

the monitor measuring the highest 03

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., PM 2 .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 03 and PM 2 .

5 . When considering

averaging approaches for 03, it should

be recognized that much of the human

health effects evidence supporting the

03 standard is based on controlled

human exposure studies that relate

individual 03 exposures directly to

responses in individuals, whereas the

health effects evidence supporting the

PM 2 .5 standards is from epidemiological

studies relating community measures of

PM 2 .5 concentrations to populationwide responses. Thus, information

available for determining an appropriate

level of a standard in these two cases is

predominantly individual-oriented in

the case of 03 and community-oriented

in the case of PM 2 .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 consideration

of a spatially averaged standard for 03.

The EPA will continue to explore this

approach.

Another important difference between

the 03 and PM standards is that the

suite of annual and 24-hour PM 2 .5

standards permits the use of the 24-

hour PM 2 .

5 standard, which would not

be spatially averaged, as a backstop to

control localized "hot spots," whereas a

single 03 standard does not allow for

such a dual approach. Also, EPA notes

that the existence of an established,

extensive 03 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

PM 2 .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 03

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 03 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 03

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 03

standard be delayed for certain purposes

until EPA had approved State

Implementation Plans to implement the

new 8-hour 03 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 IIB-3.) Also, at the time of the proposal

of the new 03 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 03

nonattainment areas once a new 03

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 03

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 i-hour 03

standard in 03 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 03 standards.

To facilitate the implementation of

those provisions and to ensure a smooth

transition to the implementation of the

new 8-hour standard, the i-hour

standard should remain applicable to

areas that are not attaining the i-hour

standard. Therefore, the i-hour

standard will remain applicable to an

area until EPA determines that it has

attained the i-hour standard, at which

point the i-hour standard will no

longer apply to that area.

C. Corn m unication of Public Health

Inform ation

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) 2 5

, 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 03 concentrations

24 For a discussion of these programs, see the

proposal.

25 Currently, a PSI value of 100 for 03

corresponds to an ambient concentration of 0.12

ppm, averaged over 1 hour.

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close to the level of the primary

standard. Given the continuum of risks

associated with exposure to 03, this

information, while perhaps of interest to

all citizens, would be particularly useful

to those individuals who are extremely

sensitive to relatively low 03

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 03 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 03 is

replaced with an 8-hour standard, there

would clearly be increased value in

using forecasted 03 concentrations in

providing cautionary statements to the

public. Currently, when a health

advisory indicates that the 1-hour 03

PSI value of 100 has been exceeded,

citizens generally have time to avoid

exposures of concern because 03 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 03

concentrations would facilitate the riskreduction 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 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

03 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 03 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 03 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 03 action system, which would

recommend voluntary actions to reduce

ambient 03 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 03 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

03 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 03 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 03. 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 03

Standard

A. Introduction

1. Overview. This notice presents the

Administrator's final decision regarding

the need to revise the current secondary

03 standard, and more specifically, to

replace the existing 1-hour, 0.12 ppm

03 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 03 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 03

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 03 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 03 effects

on vegetation since these public welfare

effects are of most concern at 03

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concentrations typically occurring in

the United States. By affecting

commercial crops and natural

vegetation, 03 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 03 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 03-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 03 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 03 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 processes, thus reducing

the carbohydrates available for plant

growth and/or yield. Growth and yield

effects of 03 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 03 exposures, data

from tree seedling studies cannot, at this

time, be extrapolated to quantify

responses to 03 in mature trees.

However, long-term observational

studies of mature trees have shown

growth reductions in the presence of

elevated 03 concentrations. Where these

growth reductions are not attributed to

03 alone, due to the presence of many

other environmental variables, it has

been reported that 03 is a significant

contributor that potentially exacerbates

the effects of other environmental

stresses (e.g., pests). In addition, studies

show that sensitivity to 03 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 03-

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 03 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 03" (Wolff, 1996). The

Administrator concurred in the proposal

with the unanimous view of CASAC

that the current standard of 0.12 ppm,

i-hour average, does not provide

adequate protection to vegetation from

the adverse effects of 03, based on the

following specific observations that

were taken from key studies and other

biological effects information reported

in the 03 Criteria Document and Staff

Paper:

(1) 03 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) 03 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, 2 6 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 03, the Administrator

took into account several additional

considerations including the extent of

exposure of 03-sensitive species,

potential risks of adverse effects to such

species, and monetized and

nonmonetized categories of increased

vegetation protection associated with

reductions in 03 exposures. In so doing,

the Administrator recognized that

markedly improved air quality, and thus

significant reductions in 03 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 03-related

26 The SUM06 exposure index cumulates over a

given time period and diurnal window all hourly

03 concentrations greater than or equal to 0.06 ppm.

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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 03

air quality in rural and remote sites was

limited by the available rural 03

monitoring network. Therefore, EPA

conducted national analyses using

geographic information systems (GIS)

and data from existing air quality

monitoring sites to estimate seasonal 03

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 03 air quality. The estimated

1990 air quality was then used as a

baseline from which to roll back 03

concentrations to project 03 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-expectedexceedance 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 fifthhighest 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 03-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 03 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

03 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 03 air quality and

exposures of 03-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 03 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 03 concentrations would

reduce 03 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-wide 2 7 and for

fruit and vegetable crops in California. 2 8

These analyses were based on the GISgenerated projections of 03 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 03

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

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 03

on agricultural crop species.

28 These fruit and vegetable crops constitute

approximately 50% of the Nation's fruits and

vegetable markets.

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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 03.

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 03" (Wolff, 1996).

These statements provide strong support

to the Administrator's judgment that the

body of scientific evidence on 03 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 0 3. 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 03 under field

conditions" (Wolff, 1996). These

uncertainties are largely a result of

inadequate rural and remote 03 air

quality data that would allow with

greater certainty determination of the

relationships between 03-related effects

being observed in the field and ambient

03 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 03, 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 consensus-building

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 03-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

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 03 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 03-

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 03-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 03 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 03-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

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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

03 criteria and standards.

Continued research on the effects of

03 on vegetation under field conditions

and on better characterizing the

relationship between 03 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 03 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 03-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 03 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 03

and its precursors and for better

characterization of 03 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 03

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 03

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 03 monitoring network. The EPA

will propose revised 03 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 long-term 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 03 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

Response-to-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.

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. 2 9 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.

2936 FR 8186, Apr. 30, 1971. EPA has maintained

this interpretation consistently since then.

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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. 3 1 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

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), I1 1(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).

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)). 3 4

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.

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).

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 A ss'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.3 6 Supreme Court review of

the Ozone and PM1 0 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 attempting to attain some of the

NAAQS. 3 7 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

36 In the PM 10 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).

37 See, e.g., H.R. Rep. No. 95 294, at 207 17

(1977).

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

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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.3 9

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. 4' 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

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-healthbased 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 1970

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).]

in which the Administrator strongly

underscored the scientific uncertainties

involved 4 2 -and the Vinyl Chloride case

drawing a sharp distinction between

sections 109 and 112 with regard to

consideration of costs and similar

factors. 4 3 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." 4 4 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. 4 5

As a general matter, the commenter

acknowledges that Congress intended to

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, 1984.

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 PM1 o, because it enacted special

nonattainment provisions, as well as provisions for

PSD increments, applicable to PM1 0 . 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.

44H.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.

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 predates 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." 4 7 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

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., PM1 0 , 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).

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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 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. 4 9 As a

result, the validity and implications of

such studies may be both uncertain and

highly controversial. Given the

precautionary nature of section 109, 5 0

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 PM 10 NAAQS in 1987. 5 1 Indeed, the

NAAQS that were upheld in the Lead

Industries, Ozone, and PM1 0 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 PM1 o decisions

noted the Administrator's findings that

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)).

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, 1984.

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

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

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

PM 10 , 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.

for health effects of the pollutant.5 5 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).

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

1160 61.

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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. 5 6

As indicated above, the Vinyl Chloride

and PM 10 cases, both of which postdated 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 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

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.

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.

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

In the PM1 0 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 PM1 0 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.

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. ' 5 9 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

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

(Description of Major Issues and Section -By-Section

Analysis of Substitute for S. 299).

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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 03 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, 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 PM 10 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 03

standards by at least 60 days. The

commenters further maintained there

was no justification for keeping the 03

standard review on the same schedule

as the PM NAAQS, since the 03 review

is not subject to a court-ordered

deadline as is PM.

The EPA believes that there are

benefits to reviewing the 03 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

03 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 03 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 mid1996 and a final decision as to whether

to revise the 03 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 03 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 03 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

03 NAAQS that she was considering

proposing. In effect, the delay of the 03

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

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comments on the 03 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 03 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

03 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 03 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 03 standard,

they prohibit EPA from revising the 03

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 03 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

60 This comment period reflects an extension of

22 days beyond the 67 day comment period

originally announced in the proposal.

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

1 12(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 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 03 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 03 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 03 standard.

These areas, referred to as "nonclassifiable nonattainment areas,"

include "submarginal" areas (i.e., 03

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 03 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 then-existing 1-hour, 0.12

ppm 03 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 03 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

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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 03 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 03 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 03 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 03

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 03 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 03 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

03 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 03

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 03 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 03 standard

may not be implemented for so long as

the current 1-hour, 0.12 ppm 03

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 03 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 03 standard. EPA

further notes that it has historically had

more than one primary standard for

criteria pollutants (e.g., annual and 24-

hour PM 10 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 03 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 03 standard before it can

promulgate and implement a new

primary 03 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 03 that is identical to the primary

ambient air quality standard.

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

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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

03 concentrations, and therefore, that

the day could be assumed to have an 8-

hour daily maximum 03 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 03 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 03 intrusion from aloft or

forest fires may lead to exceedances of

the level of the standard, particularly

within the context of peak 03

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 03 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 03 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

precision 6' for such 03 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 standard. The EPA

proposed that, for hourly data, 8-hour

average 03 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 03

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 03

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

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.

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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:

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 thirdhighest 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.

(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 03 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 congressionallydesigned 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 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 1 10(a)(2) and the

Agency may devise and promulgate a plan of

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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. 6 3

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-size-fits-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:

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 ozoneforming 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.

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

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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 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-and-comment

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 Mid-Tex 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

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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. 6 4 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 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

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.

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.

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 PM 2 .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-sizefits-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

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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 MidTex 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 MidTex 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 MidTex 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 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 NO 2 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 03

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

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.

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(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 UMRA generally requires EPA to

identify and consider a reasonable

number of regulatory alternatives and

adopt the least costly, most costeffective, 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. 6 7

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

NAAQS rule only establishes a standard of air

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

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.

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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.6 9 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 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

SO 2, 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 NO 2 NAAQS).

As this statement makes clear, EPA only

69 One commenter argued that in reviewing the

S02 NAAQS, EPA determined that it need not

revise the S02 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 S02 NAAQS.

In fact, in deciding not to revise the S02 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.

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 03.

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 03 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

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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 03 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

I 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. 0., (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 I 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, IEL,

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.

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 gg/m 3).

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 gg/m 3 ) 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

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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 Standardrelated Summary Statistic. The standardrelated 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 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 fourth-highest 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

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90%, and no single year has less than 75%

data completeness.

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

1st Highest 2nd Highest 3rd Highest 4th Highest 5th Highest

Year Percent Daily Max Daily Max Daily Max Daily Max Daily Max

Valid Days 8-hour 8-hour 8-hour 8-hour 8-hour

Conc. (ppm) Conc. (ppm) Conc. (ppm) Conc. (ppm) 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

A ve ra ge ...................................................................... 9 8% 0 .0 84

(2) As shown in example 2, the primary average ozone concentrations (i.e., 0.093 capture is less than 75%, because the average

and secondary standards are not met at this ppm) is greater than 0.08 ppm. Note that the fourth-highest daily maximum 8 hour

monitoring site because the 3 year average of ozone concentration data for 1994 is used in average concentration is greater than 0.08

the fourth-highest daily maximum 8 hour these computations, even though the data ppm.

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

1st Highest 2nd Highest 3rd Highest 4th Highest 5th Highest

Year Percent Daily Max Daily Max Daily Max Daily Max Daily Max

Valid Days 8-hour 8-hour 8-hour 8-hour 8-hour

Conc. (ppm) Conc. (ppm) Conc. (ppm) Conc. (ppm) 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 0.10 1 0 .097 0.095

A ve ra ge ...................................................................... 8 9% 0 .0 93

3. Design Values for Primary and

Secondary AmbientAir 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]

BILLING CODE 6560-50-F

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