[Federal Register Volume 64, Number 149 (Wednesday, August 4, 1999)]
[Rules and Regulations]
[Pages 42530-42549]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 99-19433]



[[Page 42529]]

_______________________________________________________________________

Part III





Environmental Protection Agency





_______________________________________________________________________



40 CFR Part 58



Air Quality Index Reporting; Final Rule

  Federal Register / Vol. 64, No. 149 / Wednesday, August 4, 1999 / 
Rules and Regulations  

[[Page 42530]]



ENVIRONMENTAL PROTECTION AGENCY

40 CFR Part 58

[FRL-6409-7]
RIN 2060-AH92


Air Quality Index Reporting

AGENCY: Environmental Protection Agency (EPA).

ACTION: Final rule.

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SUMMARY: Today, EPA adopts revisions to the uniform air quality index 
used by States for daily air quality reporting to the general public in 
accordance with section 319 of the Clean Air Act (Act). These changes 
include the addition of the following elements: a new category 
described as ``unhealthy for sensitive groups;'' two new requirements, 
first, to report a pollutant-specific sensitive group statement when 
the index is above 100, and second, to use specific colors if the index 
is reported in a color format; new breakpoints for the ozone 
(03) sub-index in terms of 8-hour average 03 
concentrations; a new sub-index for fine particulate matter 
(PM2.5); and conforming changes to the sub-indices for 
coarse particulate matter (PM10), carbon monoxide (CO), and 
sulfur dioxide (SO2). In addition, EPA is changing the name 
of the index from the Pollutant Standards Index (PSI) to the Air 
Quality Index (AQI). This document discusses the development of related 
informational materials on pollutant-specific health effects and 
sensitive groups and on precautionary actions that can be taken by 
individuals to reduce exposures of concern. This document also 
discusses the interrelationship between the uniform air quality index 
and other programs that provide air quality information and related 
health information to the general public, including State and local 
real-time air quality data mapping and community action programs.

EFFECTIVE DATE: October 4, 1999.

ADDRESSES: A docket containing information relating to EPA's revisions 
of the air quality index (Docket No. A-98-20) is available for public 
inspection in the Air and Radiation Docket and Information Center, U.S. 
Environmental Protection Agency, South Conference Center, Room M-1500, 
401 M St., SW, Washington, DC 20460, telephone (202) 260-7548. The 
docket may be inspected between 8 a.m. and 5:30 p.m. on weekdays, and a 
reasonable fee may be charged for copying. For the availability of 
related information, see SUPPLEMENTARY INFORMATION.

FOR FURTHER INFORMATION CONTACT: Terence Fitz-Simons, EPA (MD-14), 
Research Triangle Park, NC 27711, telephone (919) 541-0889, e-mail 
[email protected]. For health effects information, contact 
Susan Lyon Stone, EPA (MD-15), Research Triangle Park, NC 27711, 
telephone (919) 541-1146, e-mail [email protected].

SUPPLEMENTARY INFORMATION: In compliance with President Clinton's June 
1, 1998 Executive Memorandum on Plain Language in government writing, 
this package is written using plain language. Thus, the use of ``we'' 
or ``us'' in this package refers to EPA. The use of ``you'' refers to 
the reader and may include industry, State and local agencies, 
environmental groups and other interested individuals.

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) The Review of the National Ambient Air Quality Standards for 
Ozone: Assessment of Scientific and Technical Information (``Staff 
Paper'') (EPA-452/R-96-007, June 1996, NTIS # PB-96-203435, $67.00 
paper copy and $21.50 microfiche). (Add a $3.00 handling charge per 
order.)
    (2) Review of the National Ambient Air Quality Standards for 
Particulate Matter: Policy Assessment of Scientific and Technical 
Information (``Staff Paper'') (EPA-452/R-96-013, July 1996, NTIS # PB-
97-115406, $47.00 paper copy and $19.50 microfiche). (Add a $3.00 
handling charge per order.)
    The guidance documents associated with this rulemaking are 
available from EPA's Office of Air Quality Planning and Standards in 
Research Triangle Park, NC. Requests for these publications can be 
mailed to: Terence Fitz-Simons, EPA (MD-14), Research Triangle Park, NC 
27711. Your request may also be phoned in to Terence Fitz-Simons at 
919-541-0889, or sent by e-mail to [email protected].
    (1) Guideline for Public Reporting of Daily Air Quality--Air 
Quality Index (AQI) (EPA-454/R-99-010).
    (2) Guideline for Developing an Ozone Forecasting Program (EPA-454/
R-99-009).
    The following document is available from EPA's Office of Mobile 
Sources (OMS) in Ann Arbor, MI. Requests for this publication can be 
mailed to: Michael Ball, US EPA--National Vehicle and Fuel Emissions 
Laboratory (NVFEL), 2000 Traverwood Dr., Ann Arbor, MI 48103. Your 
request may also be phoned in to Michael Ball at 734-214-4897, or sent 
by e-mail to [email protected].
    (1) Community Action Programs: Blueprint for Program Design (EPA 
420-R-98-003).

Table of Contents

I. Background
    A. What Are the Legislative Requirements?
    B. What Is the History of the Air Quality Index?
    C. What Programs Are Related to the AQI?
    1. Ozone and Particulate Matter NAAQS Revisions
    2. Real-Time Data Reporting Initiative (Ozone Mapping Project)
    3. Community Action Programs
II. Rationale for Final Revisions
    A. What Revisions Did We Propose?
    1. What Were the Proposed General Changes?
    2. What Were the Proposed Changes to the Sub-Indices?
    B. What Were the Significant Comments and Our Responses?
    1. Comments and Responses on General Changes
    2. Comments and Responses on Changes to the Sub-Indices
    C. What Are the Final Revisions?
    1. What Are the General Changes?
    2. What Are the Changes to the Sub-Indices?
    D. What Are the Related Informational Materials?
III. Regulatory and Environmental Impact Analyses
    A. Executive Order 12866: OMB Review of ``Significant Actions''
    B. Regulatory Flexibility Analysis/Small Business Regulatory 
Enforcement Fairness Act
    C. Unfunded Mandates Reform Act
    D. Paperwork Reduction Act
    E. Executive Order 13045: Children's Health
    F. Executive Order 12848: Environmental Justice
    G. Executive Order 12875: Enhancing Intergovernmental 
Partnerships
    H. Executive Order 13084: Consultation and Coordination with 
Indian Tribal Governments
    I. National Technology Transfer and Advancement Act
    J. Congressional Review Act
IV. References

I. Background

A. What Are the Legislative Requirements?

    Section 319 of the Act governs the establishment of a uniform air 
quality index for reporting of air quality. This section directs the 
Administrator to ``promulgate regulations establishing an air quality 
monitoring system throughout the United States which utilizes uniform 
air quality monitoring criteria and methodology and measures such air 
quality according to a uniform air quality index'' and ``provides for 
daily analysis and reporting of air

[[Page 42531]]

quality based upon such uniform air quality index * * *''.

B. What Is the History of the Air Quality Index?

    In 1976, we established a nationally uniform AQI, called the 
Pollutant Standards Index (PSI), for use by State and local agencies on 
a voluntary basis (41 FR 37660). This uniform index was established in 
light of a study conducted by EPA and the President's Council on 
Environmental Quality (CEQ, 1976). This study found that the 55 urban 
areas in the U.S. and Canada reporting an index of air quality used 14 
different indices, in conjunction with different cautionary messages, 
such that in essence 55 different indices were being used to report air 
quality. This diversity of indices sent a confusing message about air 
quality to the public. Based in part on this study, we developed an 
index to meet the needs of State and local agencies that has the 
following advantages: it sends a clear and consistent message to the 
public by providing nationally uniform information on air quality; it 
is keyed as appropriate to the national ambient air quality standards 
(NAAQS) and the significant harm level (SHL) 1 which have a 
scientific basis relating air quality and public health; it is simple 
and easily understood by the public; it provides a framework for 
reflecting changes to the NAAQS; and it can be forecasted to provide 
advance information on air quality.
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    \1\ Significant harm levels are those ambient concentrations of 
air pollutants that present an imminent and substantial endangerment 
to public health or welfare, or to the environment, as established 
in 40 CFR 51.151.
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    The PSI, which is also commonly referred to by some State and local 
agencies as the AQI, includes sub-indices for O3, PM, CO, 
SO2, and nitrogen oxide (NO2), which relate 
ambient pollutant concentrations to index values on a scale from 0 
through 500. This represents a very broad range of air quality, from 
pristine air to air pollution levels that present imminent and 
substantial endangerment to the public. The index has historically been 
normalized across pollutants by defining an index value of 100 as the 
numerical level of the short-term (i.e., averaging time of 24-hours or 
less) primary NAAQS for each pollutant and an index value of 500 as the 
SHL.2 Such index values serve to divide the index into 
categories, with each category being identified by a simple informative 
descriptor. The descriptors are intended to convey to the public 
information about how air quality within each category relates to 
public health, with increasing public health concerns being conveyed as 
the categories range to the upper end of the scale. Additional 
information about the general health effects associated with each 
category, and precautions that sensitive groups and the general public 
can take to avoid exposures of concern, has been made available through 
an informational booklet, updated as appropriate, that also presents 
and explains the PSI (EPA, 1994).
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    \2\ Intermediate index values of 200, 300, and 400 were defined 
and are the basis for the Alert, Warning, and Emergency episode 
levels included in 40 CFR part 51, appendix L, as part of the 
Prevention of Air Pollution Emergency Episodes program. This program 
requires specified areas to have contingency plans in place and to 
implement these plans during episodes when high levels of air 
pollution, approaching the SHL, are in danger of being reached. 
Changes to this emergency episode program will be proposed in the 
near future.
    Below an index value of 100, historically an intermediate value 
of 50 was defined either as the level of the annual standard if an 
annual standard has been established (for PM10 and 
SO2), or as a concentration equal to one-half the value 
of the short-term standard used to define an index value of 100 (for 
O3 and CO). Coarse or inhalable particulate matter, 
PM10, refers to particles with an aerodynamic diameter 
less than or equal to a nominal 10 micrometers.
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    In 1979, we made changes to the AQI, in part to reflect revisions 
to the NAAQS for O3, and to establish requirements for AQI 
reporting (44 FR 27598). The requirement for State and local agencies 
to report the AQI appears in 40 CFR part 58.50, and the specific 
requirements (e.g., what to report, how to report, reporting frequency, 
calculations) are in appendix G to 40 CFR part 58.

C. What Programs Are Related to the AQI?

    Historically, State and local agencies have used primarily the AQI, 
or other AQIs, to provide general information to the public about air 
quality and its relationship to public health. In recent years, many 
States and local agencies, as well as EPA, have been developing new and 
innovative programs and initiatives to provide more information to the 
public, in a more timely way. These initiatives, including real-time 
data reporting through the Ozone Mapping Project and community action 
programs, can serve to provide useful, up-to-date, and timely 
information to the public about air pollution and its effects. Such 
information will help individuals take actions to avoid or reduce 
exposures of concern and can encourage the public to take actions that 
will reduce air pollution on days when levels are projected to be in 
air quality categories of concern to local communities. Thus, these 
programs are significantly broadening the ways in which State and local 
agencies can meet the nationally uniform AQI reporting requirements, 
and are contributing to State and local efforts to provide community 
health protection and to attain or maintain compliance with the NAAQS. 
We and State and local agencies recognize that these programs are 
interrelated with AQI reporting and with the information on the effects 
of air pollution on public health that is generated through the 
periodic review, and revision when appropriate, of the NAAQS.
    The most recent revisions to the O3 and PM NAAQS, the 
Ozone Mapping Project, and community action programs are discussed 
briefly below. In light of the interrelationships among these programs, 
we have developed today's revisions to the uniform AQI with the goal of 
creating a revised AQI that can effectively serve as a nationally 
uniform link across these programs. In so doing, we intend to support 
and encourage State and local participation in real-time data reporting 
initiatives and the development and implementation of community action 
programs that serve public education and health protection goals.
1. Ozone and Particulate Matter NAAQS Revisions
    On July 18, 1997, we revised the primary NAAQS for O3 
and PM based on a thorough review of the scientific evidence linking 
exposures to ambient concentrations of these pollutants to adverse 
health effects at levels allowed by the previous NAAQS. In particular, 
we replaced the 1-hour O3 NAAQS with an 8-hour O3 
NAAQS and supplemented the PM NAAQS with 24-hour and annual standards 
for fine particulate matter (measured as 
PM2.5 3). These decisions were challenged in the 
U.S. Court of Appeals for the District of Columbia Circuit, and on May 
14, 1999, the Court remanded them to the Agency for further 
consideration, principally in light of constitutional concerns 
regarding section 109 of the Act as interpreted by EPA. American 
Trucking Associations v. EPA, Nos. 97-1440, 97-1441 (D.C. Cir. May 14, 
1999). On June 28, 1999, the U.S. Department of Justice on behalf of 
EPA filed a petition for rehearing seeking review of the Court's 
decision by the entire Court of Appeals. The EPA is continuing to 
assess what further legal or administrative proceedings may be 
appropriate in response to the Court's decision, as well

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as its relevance to other rulemakings such as this one.
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    \3\ PM2.5 refers to particles with an aerodynamic 
diameter less than or equal to a nominal 2.5 micrometers.
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    With respect to the present rulemaking, we have concluded that it 
is appropriate to proceed with final action on the proposed AQI 
revisions. As indicated previously, section 319 of the Act requires the 
Agency to establish a uniform air quality index, and this requirement 
is independent of the statutory provisions governing establishment and 
revision of the NAAQS. Moreover, there is no statutory requirement that 
the AQI be linked to the NAAQS, although EPA has used NAAQS levels in 
the past as reference points for the establishment of specific 
breakpoints within sub-indices. Nothing in the Court's opinion alters 
the conclusions EPA reached in revising the air quality criteria for PM 
and O3 under section 108 of the Act, or in the NAAQS 
rulemakings, concerning the occurrence of specific health effects at 
varying concentrations of PM and O3 in the air. Regardless 
of the outcome of the remand as to the NAAQS themselves, we believe the 
scientific record and conclusions underlying them are more than 
sufficient as a basis for decisions on the levels at which the public 
should be notified about health risks associated with daily air 
quality.4
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    \4\ Under section 319, the levels that are appropriate for this 
purpose do not necessarily depend on the NAAQS levels that may be 
appropriate under section 109. Depending on how the Agency chose to 
set an ambient standard, for example, it might conclude that the 
standard does not need to preclude certain effects falling below the 
level of public health concern, and at the same time set the AQI in 
such a way as to assure that sensitive individuals who might 
experience those effects receive notification and advice on actions 
they might take to avoid them. Similarly, AQI values might be set 
that are higher than the standard would permit but that would 
require more serious health warnings. This is not to say, however, 
that the levels of the 1997 NAAQS are irrelevant to decisions on the 
AQI breakpoints. To the contrary, the levels of the 1997 NAAQS are 
useful surrogates for a series of scientific conclusions reached in 
the NAAQS rulemakings, based on the revised air quality criteria, 
regarding the nature, extent, and severity of health effects 
associated with varying concentrations of PM and O3 in 
the air. Accordingly, later sections of this notice make reference 
as appropriate to relevant levels of the 1997 NAAQS.
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    We do not regard this notification function as involving the 
constitutional concerns raised in the Court's opinion. The AQI has no 
bearing on pollution control requirements for specific sources; nor 
does it serve to implement the NAAQS involved in the litigation. 
Rather, it provides information on air quality and health that will 
help individual citizens take prudent, self-protective actions to avoid 
or reduce exposures of concern and to avoid contributing to air 
pollution on days when unhealthy air quality is projected. In this 
regard, the AQI is essentially a way of conveying scientific/medical 
advice to the public in an easily understood form.
    As indicated below, there was broad support in public comments for 
modifying and expanding the use of the AQI to take into account the 
expanded understanding of air quality-health relationships that 
resulted from EPA's review of the latest scientific information on the 
effects of PM and O3. Other proposed revisions were designed 
to enhance the effectiveness of the AQI generally. The function the AQI 
serves of conveying to the public information on daily air quality and 
associated health risks is clearly important, and the season of higher 
pollution levels is imminent. For all the above reasons, we see no 
reason to delay final action on the proposed revisions of the AQI. The 
remainder of this section discusses aspects of the O3 and PM 
NAAQS rulemakings as they relate to today's action.
    As a result of the reviews of the scientific information upon which 
the 1997 NAAQS for O3 and PM are based, an expanded 
understanding emerged as to the nature of the relationships between 
exposure to ambient concentrations of these pollutants and the health 
effects likely to be experienced, especially near the level of the 
NAAQS. We and the Clean Air Scientific Advisory Committee (CASAC) 
5 recognized that for these pollutants there may be no 
thresholds below which health effects are not likely to occur, but 
rather a continuum of effects potentially extending down to background 
levels. As ambient concentrations increase, the proportion of 
individuals likely to experience effects and the seriousness of the 
health effects increase. Thus, the 1997 standards were not considered 
risk free. While the standards were intended to protect public health 
with an adequate margin of safety, in accordance with section 109(b) of 
the Act, including the health of sensitive groups, exposures to ambient 
concentrations just below the numerical level of the standards may 
result in exposures of concern for the most sensitive individuals. 
Conversely, exposures to ambient concentrations just above the 
numerical level of the standards are not likely to result in exposures 
of concern for most healthy people. This expanded understanding is 
reflected in the forms of the new standards, which allow for multiple 
days above the numerical level of the standards.
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    \5\ CASAC is a scientific advisory committee established under 
the Act to review the scientific criteria and standards and to 
advise the Administrator on revision of the NAAQS, as appropriate.
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    These understandings were also reflected in CASAC's advice to the 
Administrator during the O3 NAAQS review, urging expansion 
of the public health advisory system (i.e., a uniform AQI) and 
communication to the public of the apparent nonthreshold nature of the 
health effects. More specifically, a number of CASAC panel members 
recommended ``that an expanded air pollution warning system be 
initiated so that sensitive individuals can take appropriate `exposure 
avoidance' behavior'' (Wolff, 1995). Consistent with this advice, in 
the preamble to the proposed revisions to the O3 NAAQS (61 
FR 65733-65734), the Administrator requested comment on the usefulness 
of providing specific health effects information when ambient 
concentrations are around the numerical level of the standard, the 
appropriateness of using the AQI to convey such information to the 
public, the possible addition of two new AQI categories (one just above 
and one just below the numerical level of the standard) and associated 
descriptors and levels, as well as related health effects and 
cautionary statements.
    Broad support for modifying the AQI was received in public comments 
on this aspect of the O3 NAAQS proposal, as discussed in the 
final rule establishing revisions to the O3 NAAQS (62 FR 
38873-38874). Commenters overwhelmingly endorsed expanding the use of 
the AQI for various reasons, although many expressed concern with the 
possible category descriptors suggested in the proposal (i.e., 
``moderately good'' and ``moderately unhealthful''). Many commenters 
felt that an expanded AQI could help particularly sensitive people take 
action to minimize their exposures, and that the AQI could be combined 
with community action programs to reduce ambient concentrations when 
the numerical level of the standard was forecasted to be exceeded. Some 
commenters endorsed increasing the specificity of health and cautionary 
statements related to the AQI categories. Commenters from State and 
local agencies encouraged us to develop any approaches to revising the 
AQI in consultation with them, specifically in the areas of sharing 
real-time monitoring data, risk communication with the public, and 
coordination of a national program.
2. Real-time Data Reporting Initiative (Ozone Mapping Project)
    The Ozone Mapping Project is part of EPA's Environmental Monitoring 
for

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Public Access and Community Tracking (EMPACT) initiative--a new 
approach to providing timely environmental information to communities. 
It is a cooperative effort of the EPA, State and local air pollution 
control agencies, and regional organizations including the Mid-Atlantic 
Regional Air Management Association (MARAMA), the Northeast States for 
Coordinated Air Use Management (NESCAUM), the northeast Ozone Transport 
Commission (OTC), the Lake Michigan Air Directors Consortium (LADCO), 
SouthEast States Air Resource Managers (SESARM), and Central States Air 
Resource Agencies (CenSARA). During the summer of 1998, EPA's Office of 
Air Quality Planning and Standards assumed coordination of the project.
    The Ozone Map provides simple and timely information about ground-
level O3. During the 1998 O3 season it was 
available on EPA's AIRNOW web site (http://www.epa.gov/airnow) and on 
some local television and news reports. It is an animated contour map 
that shows concentrations of O3, in categories ranging from 
good to moderate to varying degrees of unhealthy, based on AQI values, 
as they develop across the eastern United States. In 1998, the map was 
created from real-time, hourly O3 data provided by a network 
of more than 400 air monitoring stations from South Carolina to 
Wisconsin and Maine. When accessed on a computer, cautionary statements 
for each category could be displayed by running a cursor over the 
legend. Also available on the AIRNOW web site were still maps of 
maximum values and forecasted values, and archived animated maps. In 
1999, the ozone mapping coverage is being expanded to include 31 States 
and over 1500 monitors across the eastern and central U.S., and 
California. In addition, TV weather service providers are planning to 
carry the Ozone Map and forecasts as part of their traditional weather 
packages for local TV stations.
    Along with the Ozone Map, the AIRNOW web site contains information 
about O3 health effects in the ``Health Facts'' section, and 
emission reduction activities in the ``What You Can Do'' section. It 
also provides links to real-time data, and community action program web 
sites, that are maintained by State and local agencies around the 
country. The goals of the web site are to: (1) Provide real-time air 
pollution data in an understandable, visual format, (2) provide 
information about the public health and environmental effects of air 
pollution, and (3) provide the public with information about ways in 
which they can protect their health and actions they can take to reduce 
pollution.
3. Community Action Programs
    The implementation of community action programs (also referred to 
as voluntary action programs or episodic emission control programs) is 
becoming increasingly popular across the country as an innovative 
approach used to reduce emissions of O3 precursors, CO, and 
PM. Motivation for implementation of this type of program often stems 
from local government and business concerns about the NAAQS attainment 
status of the area and the restrictions, additional controls, and costs 
associated with being classified as a nonattainment area. Many areas 
are also motivated by public health concerns and believe that 
increasing the amount of air quality information available to sensitive 
populations raises awareness and results in significant health 
benefits. Specific goals which are usually associated with community 
action programs include: (1) Educate the public and enhance protection 
of public health; (2) attain or maintain NAAQS attainment status and 
the associated economic benefits; (3) meet specific emission reduction 
targets; and (4) manage/reduce traffic congestion.
    Community action programs are usually voluntary and generally 
provide multiple steps that the public, business, and industry can take 
to reduce emissions when higher levels of air pollution are forecast to 
occur, including in particular transportation-related measures such as 
trip reduction, postponement of certain activities such as vehicle 
refueling, and maintenance of cars. The programs emphasize educating 
the public about the impact of individual activities on local air 
quality and the basics of air pollution. The educational component of 
these programs also helps to create a strong link between environmental 
goals and associated public health benefits.
    Most of these programs are based on the categories of the AQI and 
make use of the AQI descriptors and related health effects and 
cautionary statements on action days. By linking action days to the 
AQI, local control programs hope to alter individual behavior to reduce 
emissions and to reduce exposures to the population. In addition to 
reduced pollutant exposure of the general population due to improved 
air quality, there are other health benefits directly associated with 
community action programs that can be enhanced by linkage to the AQI. 
Different population groups are more sensitive to the harmful effects 
of the different air pollutants included in the AQI, and the revisions 
to the AQI being adopted today, together with related informational 
materials, will significantly improve the effectiveness of 
communications with these groups. Public education, or programs 
directly targeting these groups, may provide the most significant 
benefits of a community action program. Forecasting days with elevated 
pollution levels, and then communicating effectively about air quality 
and associated health effects, may help these groups selectively limit 
their outdoor activities and, therefore, limit their potential for 
exposures of concern.
    We are committed to providing States and local agencies with 
support in their efforts to meet air quality standards, to inform the 
public about air quality, and to educate the public about the impacts 
of air pollution. The revisions to the AQI being adopted today have as 
a goal the creation of a revised AQI that can effectively serve as a 
nationally uniform link across the range of programs (e.g., real-time 
data reporting initiatives, community action programs) that have these 
functions.
    In support of community action programs, we have developed 
informational materials related to the AQI, including the health 
effects and cautionary statements associated with each category and 
more detailed health effects information (see section II.D.), available 
on the AIRNOW web site, that State and local agencies may use to 
enhance their community action programs. Focusing on transportation 
measures that are often a major component of community action programs, 
EPA's OMS has developed a report entitled, ``Community Action Programs: 
Blueprint for Program Design.'' This document describes the major steps 
needed to put together a successful episodic control program and 
provides criteria that State and local agencies can use to examine and 
evaluate their own programs. The report is available from OMS (see 
Availability of Related Information).

II. Rationale for Final Revisions

    In developing the revisions to the AQI that are being adopted 
today, we sought extensive input from State and local agencies and from 
the public. We sponsored a workshop with State and local agencies, 
participated in numerous meetings, prepared and made available a staff 
draft revision to the AQI sub-index for O3 for use during 
the 1998 O3 season, and conducted several focus groups 
across the nation to obtain public input on the effectiveness of draft 
revisions to the AQI and related O3 maps and informational 
materials. A

[[Page 42534]]

detailed history of the process leading to the proposal and the 
rationale for the proposed revisions are described more fully in the 
December 9, 1998 proposal notice (63 FR 67818-67834). The sub-sections 
below contain a description of the revisions we proposed, a discussion 
of the significant comments we received and our responses to them, and 
a summary of the AQI we are adopting today.

A. What Revisions Did We Propose?

    The primary consideration that shaped the proposed revisions was 
the importance of providing nationally uniform health information 
associated with daily ambient levels of the air pollutants included in 
the index, consistent with the requirement of section 319 of the Act 
for an index to achieve national uniformity in daily air quality 
reporting. More specifically, the proposed changes to the AQI sub-
indices for O3 and PM reflected the 1997 revisions to the 
O3 and PM NAAQS. The proposed general changes to the 
structure of the AQI were based on the expanded understanding that 
emerged during the O3 and PM reviews as to the nature of the 
relationships between exposure to ambient concentrations of these 
pollutants and the health effects likely to be experienced, 
consideration of the implications of changes for the other pollutants, 
and broad input from State and local agencies and the public. The 
proposed general changes to the AQI, together with related 
informational materials, were intended to expand the use of the AQI to 
provide more pollutant-specific health information, especially when 
ambient concentrations are close to the level of the primary NAAQS.
1. What Were the Proposed General Changes?
    a. Categories and related descriptors, index values and colors. The 
AQI currently incorporates the pollutants O3, PM, CO, 
SO2, and NO2. Index values range from 0 to 500 
6, and the index is segmented into five categories named by 
descriptor words that were chosen to characterize the relationship 
between daily air quality and public health. To reflect better the 
current understanding of the health effects associated with exposure to 
these air pollutants, we proposed to revise the AQI categories and 
descriptors, and to associate specific colors with the categories as 
shown below in Table 1.
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    \6\ For NO2, the index ranges from 200 to 500, since 
there is no short-term NAAQS for this pollutant.

    Table 1.--Proposed Category Index Values, Descriptors, and Colors
------------------------------------------------------------------------
      Index values              Descriptor                 Color
------------------------------------------------------------------------
0-50....................  Good..................  Green
51-100..................  Moderate..............  Yellow
101-150.................  Unhealthy for           Orange
                           sensitive groups.
151-200.................  Unhealthy.............  Red
201-300.................  Very unhealthy........  Purple
301-500.................  Hazardous.............  Maroon
------------------------------------------------------------------------

    These proposed changes reflected the addition of a new category 
above an AQI of 100, created by dividing the current ``unhealthful'' 
category into two categories.
    When air quality is in the ``unhealthy for sensitive groups'' 
range, people that are in the sensitive group, whether the sensitivity 
is due to medical conditions, exposure conditions, or inherent 
sensitivity, may experience exposures of concern. However, exposures to 
ambient concentrations in this range are not likely to result in 
exposures of concern for most healthy people. The descriptor 
``unhealthy for sensitive groups'' was chosen to convey this message 
clearly. Participants in focus groups (SAIC 1998) clearly understood 
that ``sensitive groups'' does not refer to the general public, 
indicating that this descriptor effectively communicates the intended 
health message. This category would include a caution that while 
perhaps of interest to all citizens, would be of particular interest to 
individuals and families of individuals who are members of sensitive 
groups.
    As air quality moves into the ``unhealthy'' range, exposures are 
associated with an increase in the number of individuals who could 
potentially experience effects and includes a greater proportion of 
members of the general public. Based on input received in the 
development of the proposal, the descriptor ``unhealthy'' appropriately 
characterizes air quality in this range.
    In addition to an increasing number of exposures of concern, when 
air quality moves into the ``unhealthy'' range and above, individuals 
who were affected at lower levels, typically members of sensitive 
groups, are likely to experience more serious health effects than 
members of the general public. To reflect this understanding, it is 
appropriate to convey two messages in the cautionary statements for 
both the ``unhealthy'' and ``very unhealthy'' categories. One message 
is directed to members of sensitive groups, and the other is directed 
to the general public. The use of a distinct cautionary message for 
members of sensitive groups is entirely consistent with an original 
goal that the index be based on the relationships between pollutant 
concentrations and adverse health effects within various groups, e.g., 
aggravation of disease in people with respiratory disease and incidence 
of respiratory effects in healthy people. Guidance on pollutant-
specific cautionary statements related to the categories of the AQI is 
discussed below in section II.D.
    Consistent with the overarching goal of national uniformity in the 
reporting of air quality, we proposed that the specific colors listed 
in Table 1 be associated with each category. While the AQI can be 
reported without the use of colors (through text and numbers alone), 
when the index is reported using colors, we proposed to require that 
only these specified colors be used. Three examples of AQI reports that 
use color are the color bars that appear in many newspapers, the color 
scales on State and local agency web sites, and the color contours of 
the Ozone Map. We participated in many discussions with State and local 
agencies and associations regarding which specific colors should be 
associated with the AQI categories, particularly above an index value 
of 100. These discussions typically were in the context of either the 
Ozone Mapping Project or community action programs. It was clear that 
the color associated with a category can be part of the health effects 
and cautionary message being conveyed. Were various State and local 
agencies to use different colors to represent the same category, and 
thus the same level of air quality, it could well send a confusing 
message about air quality and associated health effects to the public.
    As an alternative to requiring the use of specified colors, we 
solicited comment on the option of recommending, rather than requiring, 
the use of these colors when reporting agencies choose to report the 
AQI in color format. In soliciting comment on this alternative, we 
sought to allow communities maximum flexibility in AQI reporting, while 
still preserving a nationally uniform AQI. We, therefore, requested 
that commenters addressing this issue discuss how this more flexible 
approach would satisfy the statutory language requiring a nationally 
uniform AQI if different colors may be used across the nation to 
represent the same range of air quality.
    b. Reporting requirements. We proposed to change 40 CFR part 58.50 
to require reporting of the AQI in all

[[Page 42535]]

Metropolitan Statistical Areas (MSAs) 7 with a population 
over 350,000, instead of all urbanized areas with a population over 
200,000. This change was proposed for consistency with the other 
monitoring regulations in part 58, which are or will be based on MSAs. 
This proposed change would not, however, have a significant impact on 
who is required to report, since virtually the same number of cities 
would be covered under the proposed reporting requirement as are 
covered under the existing requirement.
---------------------------------------------------------------------------

    \7\ A complete list of MSAs and their boundaries can be found in 
the Statistical Abstract of the United States (1998).
---------------------------------------------------------------------------

    Consistent with early input from State and local agencies, we 
proposed to change the rounding conventions used to calculate index 
values corresponding to pollutant concentrations at and above the 
numerical level of the NAAQS to be consistent with the rounding 
conventions used in defining the NAAQS for each pollutant. This would 
avoid situations where a health advisory could be issued that describes 
the air as unhealthy, when in fact the numerical level of the standard 
has not been exceeded.
    The proposed rule retained the requirements to identify the area 
for which the AQI is being reported, the time period covered by the 
report, the ``critical'' pollutant for which the reported AQI value was 
derived, the AQI value, and the associated category descriptor. 
Recognizing that many agencies use a color format to report the AQI, 
the proposed rule added the requirement to report the associated 
category color if a color format is used. Because different sensitive 
groups are at-risk from different pollutants, issuing advisories for 
all sensitive groups who may be affected at AQI values greater than 100 
clearly improves public health protection. Therefore, the proposed rule 
encouraged, but did not require, that AQI reports include: appropriate 
health effects and cautionary statements, all AQI values greater than 
100, the AQI for sub-divisions of the MSA (if there are important 
differences in air quality across sub-divisions of the MSA), possible 
causes for high index values, and the actual pollutant concentrations. 
These topics were also discussed in our draft ``Guideline for Public 
Reporting of Daily Air Quality--Pollutant Standards Index (PSI)'' that 
was made available on the AIRLINKS web site.
    The proposed rule emphasized the importance of forecasting the AQI 
by specifying that forecasted values should be reported, when possible, 
but did not require that forecasted values be reported. Given the 
importance of the O3 sub-index in a large number of MSAs, 
and the use of an 8-hour averaging time for calculating the 
O3 sub-index value, forecasting the O3 index 
value is now more beneficial than before. For a health advisory system 
to be effective, people need to be notified as early as possible to be 
able to avoid exposures of concern. Because the O3 sub-index 
is based on 8-hour O3 averages, forecasting O3 
concentrations clearly would have increased value in providing 
cautionary statements to the public. We recognized that many State and 
local air agencies are already issuing health advisories based on 
forecasted O3 concentrations. Since we have determined that 
forecasting would add much to the benefits of AQI reporting, we 
indicated that we would be making available guidance on starting a 
forecasting program (EPA 1999b) in an area or MSA where forecasting is 
not presently done. Included in the document is guidance on using 
hourly O3 concentrations as predictors for 8-hour averages.
    c. Index name. Many State and local agencies encouraged us to 
change the name of the PSI to the Air Quality Index, or AQI, since many 
agencies already use the name AQI when reporting the AQI value to the 
public. Most participants in the focus groups preferred the name AQI, 
commenting that it more clearly identified the index as relating to the 
quality of the air rather than to environmental pollution in general. 
Based on these considerations, we solicited comment on changing the 
index name from Pollutant Standards Index (PSI) to Air Quality Index 
(AQI).
2. What Were the Proposed Changes to the Sub-Indices?
    To conform to the proposed general changes to the AQI discussed 
above, and to reflect the recent revisions to the O3 and PM 
NAAQS, we proposed changes to the sub-indices for O3, PM, 
CO, and SO2; no conforming changes are necessary for the 
NO2 sub-index. The proposed sub-indices are summarized below 
in Table 2, in terms of pollutant concentrations that correspond to 
breakpoints in the index, and are discussed in the following sections.

                                       Table 2.--Proposed Breakpoints for O3, PM2.5, PM10, CO, and SO2 Sub-indices
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                              O3                                        PM
                                    -------------------------------------------------------------------------------------
             AQI value                                                                     PM2.5, 24-hr     PM10, 24-hr      CO, 8-hr       SO2, 24-hr
                                                  8-hr (ppm)                1-hr (ppm)     (g/    (g/        (ppm)           (ppm)
                                                                                               m\3\)           m\3\)
--------------------------------------------------------------------------------------------------------------------------------------------------------
50.................................  0.07...............................  ..............              15              50               4            0.03
100................................  0.08...............................            0.12              65             150               9            0.14
150................................  0.10...............................            0.16           * 100             250              12            0.22
200................................  0.12...............................            0.20           * 150             350              15            0.30
300................................  0.40 (1-hr)........................            0.40           * 250             420              30            0.60
400................................  0.50 (1-hr)........................            0.50           * 350             500              40            0.80
500................................  0.60 (1-hr)........................            0.60           * 500             600              50            1.00
--------------------------------------------------------------------------------------------------------------------------------------------------------
* If a different SHL for PM2.5 is promulgated, these numbers will be revised accordingly.

    a. Proposed ozone sub-index. On July 18, 1997, we revised the 
O3 primary NAAQS to replace the 1-hour standard with a new 
standard with an 8-hour average at a level of 0.08 ppm and a form based 
on the 3-year average of the annual fourth-highest daily maximum 8-hour 
average O3 concentrations measured at each monitor within an 
area (62 FR 38856-38896). These proposed revisions were based on 
findings from the most recent review of the NAAQS indicating that the 
new primary standard will provide increased protection to the public, 
especially children active outdoors and other sensitive groups, against 
a wide range of O3-induced health effects, including 
decreased lung function; increased respiratory symptoms; hospital 
admissions and emergency room visits

[[Page 42536]]

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. In setting this standard, we 
recognized that there is no apparent threshold below which health 
effects do not occur, that the standard is not risk free, and, thus, 
that exposures of concern are possible below the numerical level of the 
standard for some extremely sensitive individuals.
    We proposed to set an index value of 100 equal to the level of the 
8-hour O3 standard. Recognizing the continuum of health 
effects, we considered the results of a quantitative risk assessment 
(Whitfield et al., 1996) in selecting 8-hour O3 
concentrations to correspond to index values of 50, 150 and 200. Since 
no human health effects information was available for 8-hour average 
O3 concentrations at significantly higher levels, we 
proposed to retain the breakpoints at the upper end of the AQI scale 
(between the ``very unhealthy'' and ``hazardous'' categories and the 
SHL which corresponds to the top of the PSI scale of 500) in terms of 
the existing 1-hour average concentrations.
    These proposed revisions reflect the new 8-hour O3 NAAQS 
and will in almost all areas result in a more precautionary index than 
the current 1-hour sub-index. However, we recognized that a very small 
number of areas in the U.S. have atypical air quality patterns, with 
very high 1-hour daily peak O3 concentrations relative to 
the associated 8-hour average concentrations. In such areas, the use of 
the current 1-hour sub-index may be more precautionary on a given day 
than the proposed 8-hour sub-index. To allow for the reporting of the 
more precautionary sub-index value, we proposed to retain the 1-hour 
sub-index at and above AQI values of 100 and to allow the reporting of 
the higher of the two O3 sub-index values. Thus, both the 
new 8-hour and the current 1-hour sub-indices, as shown in Table 2, 
were included in the proposed appendix G. Since for the large majority 
of areas the 8-hour sub-index will be more precautionary, we did not 
propose to require all areas to calculate both sub-index values. 
Rather, we proposed to allow areas the flexibility to calculate both 
sub-index values and, when both sub-index values are calculated, to 
require that the higher value be reported. We specifically solicited 
comment on this proposed approach.
    b. Proposed PM sub-index. On July 18, 1997, we revised the PM NAAQS 
by adding a new set of standards for fine particles, or 
PM2.5, set at levels of 15 g/m\3\ (annual) and 65 
g/m\3\ (24-hour average) (62 FR 38652-38760). These revisions 
were based on findings from the most recent review of the PM NAAQS that 
recently published studies have indicated that serious health effects 
were more closely associated with the levels of the smaller particle 
subset of PM10. These health effects include premature 
mortality and increased hospital admissions and emergency room visits, 
primarily in the elderly and individuals with cardiopulmonary disease; 
increased respiratory symptoms and disease in children and individuals 
with cardiopulmonary disease; decreased lung function, particularly in 
children and individuals with asthma; and alterations in respiratory 
tract defense mechanisms. In addition, PM10 standards were 
retained at the same levels of 50 g/m\3\ (annual) and 150 
g/m\3\ (24-hour average) to continue to provide protection 
against health effects associated with the coarse particle subset of 
PM10, including aggravation of asthma and respiratory 
infections. To reflect these revisions to the PM NAAQS, we proposed to 
add a new sub-index for PM2.5, and to make conforming 
changes to the sub-index for PM10, consistent with the 
proposed general changes to the AQI. The proposed sub-indices are 
summarized in Table 2 and discussed below.
    Proposed new PM2.5 sub-index. Consistent with the 
historical method of selecting breakpoints of the AQI, we proposed to 
set an index value of 100 at the level of the 24-hour PM2.5 
NAAQS, 65 g/m\3\, and an index value of 50 at the level of the 
annual NAAQS, 15 g/m\3\. Also consistent with the basic 
structure of the AQI, the proposed upper bound index value of 500 
corresponds to the SHL, established in section 51.16 of the CFR under 
the Prevention of Air Pollution Emergency Episodes program. The SHL is 
set at a level that represents an imminent and substantial endangerment 
to public health. When we propose revisions to the Prevention of Air 
Pollution Emergency Episodes program, the proposal will include a SHL 
for PM2.5. In the interim, we proposed to establish a 
PM2.5 concentration of 500 g/m\3\ to be associated 
with a PM2.5 index value of 500.
    For intermediate breakpoints in the AQI between values of 100 and 
500, PM2.5 concentrations were proposed that generally 
reflect a linear relationship between increasing index values and 
increasing PM2.5 values. The available scientific evidence 
of health effects related to population exposures to PM2.5 
concentrations between the 24-hour NAAQS level and the proposed 
PM2.5 concentration to be associated with a PM2.5 
index value of 500 suggest a continuum of effects in this range, with 
increasing PM2.5 concentrations being associated with 
increasingly larger numbers of people likely experiencing serious 
health effects (62 FR 38675; Staff Paper, p. VII-27). The proposed 
generally linear relationship between AQI values and PM2.5 
concentrations in this range, rounded to increments of 50 g/
m\3\ to reflect the approximate nature of such a relationship, is 
consistent with this evidence.
    Proposed conforming changes to the PM10 sub-index. 
Consistent with the retention of the levels of the PM10 
NAAQS, we proposed to retain the PM10 sub-index generally 
and to add a new breakpoint at an index value of 150 to conform to the 
proposed additional AQI category. We proposed that this breakpoint be 
set at a PM10 24-hour average concentration of 250 
g/m\3\, the mid-point between the breakpoints associated with 
index values of 100 and 200. We believe that the PM10 sub-
index, with this conforming change, remains appropriate for the public 
health protection purposes of the AQI.
    c. Proposed conforming changes to the CO and SO2 sub-
indices. Since the current AQI sub-indices reflect the current NAAQS 
for CO and SO2, the only change we proposed for these sub-
indices was to add a breakpoint to each sub-index at an index value of 
150 to conform to the proposed additional AQI category. We proposed 
that these breakpoints be set at concentrations at the mid-points 
between the breakpoints associated with index values of 100 and 200, 
consistent with the approach described above for conforming changes to 
both the 1-hour O3 sub-index and the PM10 sub-
index. These proposed breakpoints are summarized in Table 2 and will be 
reviewed in conjunction with the future reviews of the CO and 
SO2 NAAQS.

B. What Were the Significant Comments and Our Responses?

    This section describes the significant comments we received on 
proposed revisions to the index and our general responses to them. More 
detailed comment summaries and responses are contained in a Response to 
Comments Document that is available in the docket (see Addresses).
1. Comments and Responses on General Changes
    a. Categories and related descriptors, index values and colors. 
With regard to the proposed changes to the general structure of the 
index, we received comments that focused on two major

[[Page 42537]]

issues. The first major issue was whether to add a category above or 
below the standard, or both. In addition, related to that issue were 
comments about the proposed descriptor for the category we proposed to 
add above the level of the standard. The second major issue regarded 
the particular colors, listed in Table 1, we proposed to associate with 
each category.
    With regard to the general structure of the index, most commenters 
supported our proposal to add a category above the level of the 
standard. However, commenters from environmental groups and several 
States suggested adding a category below the level of the standard to 
provide additional caution for members of sensitive groups, instead of, 
or in addition to one above. These commenters expressed the view that 
the proposed sub-indices, that added a category above the standard, did 
not sufficiently caution members of sensitive groups about health 
effects occurring below the level of the standard. Specifically, their 
comments were in reference only to potential health effects occurring 
below the 8-hour O3 and 24-hour PM2.5 standards. 
Regarding health effects below the PM2.5 standard, one State 
commenter took exception with the statement in the proposal that an 
additional category below the standard, while perhaps meaningful for 
O3, would not be an appropriate distinction for the other 
pollutants in the index. This commenter noted that ``such a distinction 
would be more imperative for other pollutants, especially for PM where 
the level of the 24-hour standard may be less protective of sensitive 
groups than the ozone standard.'' (Docket No. A-98-20, IV-D-19). 
Agreeing with the importance of cautioning sensitive groups below the 
level of the 24-hour PM2.5 standard, another commenter noted 
``We believe that adding a category below the level of the standard is 
of particular importance with respect to fine particles.'' (Docket No. 
A-98-20, IV-D-11). Regarding the O3 sub-index, some of the 
States and the environmental groups that endorsed adding a category 
below the level of the standard supported that position by noting that 
we and CASAC stated that extremely sensitive individuals may be 
affected down to background levels of O3. One comment from 
an environmental group noted that:

The CASAC recognized that for O3 and fine particle 
pollution, ``there are no discernible thresholds below which health 
effects are not likely to occur in the most sensitive individuals' 
as it was advising EPA to set new health standards. We agree with 
CASAC and support the idea of setting ``an expanded air pollution 
warning system (to) be initiated so that sensitive individuals can 
take appropriate exposure avoidance behavior,'' however EPA has 
misrepresented the health threat with the levels it has proposed. 
(Docket No. A-98-20, IV-D-17).

    A State commenter that supported adding a category below the level 
of the standard observed that adding such a category would be 
consistent with EPA's conclusion ``that exposures to ambient 
concentrations just below the numerical level of the standard may 
result in exposures of concern for the most sensitive individuals.'' 
(Docket No. A-98-20, IV-D-19).
    We understand and agree with the issues related to communication of 
risk below the levels of the 24-hour PM2.5 and 8-hour 
O3 standards. For the PM2.5 sub-index, we have 
addressed concerns about health effects below the level of the 24-hour 
PM2.5 standard by revising the PM2.5 sub-index so 
sensitive groups are cautioned below the 24-hour PM2.5 
standard. Based on review of the suggested revisions to the 
PM2.5 sub-index that we received in comments, we believe 
this approach fully addresses their concerns. The revision is discussed 
in section II.B.2 below.
    For better communication of health risk below the 8-hour 
O3 standard, we have addressed the issues raised by 
commenters by revising the O3 sub-index. We have expanded 
the ``moderate'' range of the 8-hour O3 sub-index to make it 
more precautionary. When air quality is in the ``moderate'' range of 
the 8-hour O3 sub-index, we have provided health effects and 
cautionary statements, available in our AQI Reporting Guidance document 
(EPA, 1999a) (discussed in section II.D), that may be used by State and 
local agencies to caution unusually sensitive individuals below the 
level of the 8-hour O3 standard. This revision is discussed 
in section II.B.2 below.
    We do not believe it is necessary or appropriate to change the 
general structure of the index by adding a new category below the level 
of the standard to caution extremely sensitive individuals. Based on 
the concerns of State and local agencies that the addition of two new 
categories would unduly complicate the index, we are adding just one 
new category to maintain the degree of simplicity strongly supported by 
State and local agencies, none of whom advocated the addition of two 
new categories. As described in section II.A.1 above, we believe that 
adding a category above the level of the standard makes a distinction 
that is useful for members of sensitive groups without alarming the 
general public. As noted by one State commenter:

    We are satisfied and support the proposed category index values, 
descriptors and colors. [We] believe that the Air Quality Index * * 
* has been a very effective communication tool during the ozone 
season. It has been our experience that a category above the 
standard provides the proper communication to the affected 
populations without alarming or desensitizing others. (Docket No. A-
98-20, IV-G-04).

    Further, given the changes we have made to the PM2.5 
sub-index, and the expanded ``moderate'' range and the cautionary 
statements we have made available in guidance for use below the level 
of the 8-hour O3 standard, we do not believe a category 
below the level of the standard to caution members of sensitive groups 
would be an appropriate distinction for any of the pollutants included 
in the index. We believe that the approach we have adopted retains the 
simplicity of the index while allowing for more detailed cautionary 
information to be made available to the public when appropriate.
    With regard to the descriptor ``unhealthy for sensitive groups,'' 
some commenters expressed the view that this descriptor is misleading 
because it encompasses a large segment of the population. In addition, 
they argued, the public will not know that for certain pollutants 
healthy people, especially healthy children, are members of sensitive 
groups. Noting that it is prudent policy to assume that most risk 
communication regarding air quality impacts will be limited to the 
general descriptors, some of these commenters requested that if we 
continue to distinguish sensitive groups from the general population, 
that the descriptor be changed from ``unhealthy for sensitive groups'' 
to ``unhealthy for children and other sensitive groups,'' so that the 
public would receive a clear message that children are members of a 
sensitive group that may be at increased risk from exposure to ozone. 
(Docket No. A-98-20, IV-D-2, IV-D-4 and IV-D-11). We agree with the 
view of these commenters, based on the responses of participants in the 
focus groups, that the public will not know that healthy people, 
including healthy children, may be at risk when air quality is in the 
``unhealthy for sensitive groups'' range. The suggested descriptor, 
however, is only appropriate for pollutants for which children are a 
sensitive group. Since the sensitive groups differ from one pollutant 
to another, and children are only part of the sensitive group for 
O3, PM2.5 and NO2, this descriptor is 
not appropriate for the other pollutants. For

[[Page 42538]]

example, the descriptor ``unhealthy for children and other sensitive 
groups'' would not be appropriate for use in the CO sub-index, where 
people with heart disease are the group most at-risk. Use of this 
descriptor when CO levels are above an index value of 100 could lead to 
confusion about the health effects associated with high levels of CO. 
Therefore, we do not believe it would be useful or prudent to adopt the 
descriptor ``unhealthy for children and other sensitive groups.'' To 
increase public awareness that healthy children are members of the 
sensitive group for O3, we are adding the requirement that 
when the AQI value is above 100, reporting agencies include in their 
published report a statement describing the sensitive group for that 
particular pollutant. The reporting requirement for pollutant-specific 
statements describing sensitive groups is discussed below in section 
II.C.1.b on reporting requirements, and listed in appendix G. We 
believe that the requirement for agencies to report the pollutant-
specific statements identifying the groups at risk, when air quality is 
above an index value of 100, will more effectively communicate the risk 
associated with specific air pollutants, and thereby better help 
members of the public reduce personal exposure. To the extent possible 
with AQI reporting, this requirement will also ensure that the public 
is informed that children are part of the sensitive group for 
O3. This requirement will not only improve protection for 
healthy children, but also healthy adults, the elderly, and people with 
heart and lung disease. We believe that another good way to address 
this lack of awareness is to educate the public, and the media and 
health care professionals that inform the public, about the health 
effects message associated with the category ``unhealthy for sensitive 
groups.'' To help accomplish the goal of educating the public, we will 
be expanding the development of education and outreach materials and 
activities as described in section II.D below.
    With regard to the colors listed in Table 1, we received comments 
concerning both the particular colors associated with the different 
categories and whether specific colors should be required or 
recommended. The majority of commenters, including most State and local 
agencies commenting, supported our proposed color scheme. Many of those 
(commenters that did support it), had used the same or a similar color 
scheme associated with either community action programs or ozone maps. 
Commenters that had used the same or a similar color scheme noted that 
it effectively and appropriately portrayed the full range of local air 
quality values. On the other hand, some environmental groups and 
several States commented that the color red should be used for the 
category just above standard, instead of the color orange that we 
proposed. Primarily, these commenters expressed the view that the color 
orange would not send a sufficiently strong message that the standard 
has been exceeded. In the proposal we indicated that because the color 
red sends a strong cautionary message, it is most appropriately used 
when effects are likely to occur in the general population, and when 
more serious effects are likely in members of sensitive groups. Many of 
these commenters noted that since up to 30 percent of the population 
could be considered to be in the sensitive group for O3, 
when the standard is exceeded the general public should be alerted. 
These commenters expressed the view that it is appropriate to use the 
color red just above the level of the standard both to alert the public 
of potential health risks and to encourage emission reduction actions. 
An environmental group commented:

    While individuals that are sensitive to poor air quality may 
look at the daily listing in the newspaper or call a message 
recorded by the state or local air agency, we know from experience 
that air quality does not receive broad public attention until it is 
predicted or reaches the level of ``code red.'' At that point, the 
television and radio media announces that people should restrict 
outdoor activity and take steps to not add more pollution to the air 
by carpooling, using less electricity, or using mass transit. 
(Docket No. A-98-20, IV-D-17).

    Another commenter from a State agency noted:

    Considering that the definition of sensitive individuals for 
ozone includes healthy active children and outdoor workers, a clear 
unambiguous message needs to be sent to the public so that they can 
respond accordingly. For parents of active children, a message which 
states that air quality is unhealthy, and displays it using the 
color red, sends a clear message--even though it may carry with it 
the risk that individuals not in the sensitive population might also 
take exposure avoidance measures. Issuing a message that air quality 
is unhealthy for sensitive individuals and displays it with a code 
orange runs the risk of having sensitive individuals, or those 
guiding sensitive individuals (i.e., doctors and parents) not 
prescribe any avoidance action because of the ambiguity of the 
message. (Docket No. A-98-20, IV-G-19).

    Additionally, these commenters suggested that the color orange be 
used for the category they wanted us to add below the level of the 
standard, as described above.
    In considering these comments, we recognize that the NAAQS are set 
to protect public health with an adequate margin of safety, including 
the health of sensitive groups. When the standards are met, public 
health is protected. Exposures to ambient concentrations just above the 
numerical level of the standards are not likely to result in exposures 
of concern for most healthy people. This is especially true for the 8-
hour O3 standard, which has a concentration-based form 
designed to offer more protection from higher concentrations than from 
multiple smaller exceedances of the standard. The form of the 8-hour 
O3 standard allows for multiple days above the level of the 
standard, provided the 3-year average of the fourth-highest maximum 
concentrations does not exceed the level of the standard. This means 
that public health is protected, even when there are multiple days each 
year when ambient O3 concentrations are above the level of 
the standard, as long as the standard is met. Therefore, it is 
inappropriate on any given day to express a high level of concern when 
air quality just exceeds the level of the standard. Besides sending an 
inaccurate health effects message by using the color red with the 
category ``unhealthy for sensitive groups,'' another concern is the 
potential loss of credibility that could result from repeatedly sending 
a signal disproportionate to the expected incidence of noticeable 
symptoms. If this were to happen, the AQI could lose the power to 
influence people's behavior to protect their health. One commenter from 
a State agency expressed this concern:

    One of our key concerns * * * is that the general public will 
become ambivalent if we forecasted 20, 30, or more Code Red days 
over the course of an ozone season. Under this scenario, people may 
not take adequate precautions to protect themselves when an actual 
unhealthy level is reached. (Docket No. A-98-20, IV-G-05).

    A commenter from another State agency expressed a similar view:

    It is important to make sure that this general message is not 
jeopardized by treating the new 85 ppb, 8-hour standard as the 
bright line between healthy and unhealthy. The Code Red message will 
not be considered credible if it is issued between 40 to 60 times a 
summer in our area. Last year there were 54 days * * * where the 8-
hour standard was exceeded. (Docket No. A-98-20, IV-G-13).

    From the comments we have received and from our focus group 
research, we believe that the color red sends too strong a message for 
use in the

[[Page 42539]]

``unhealthy for sensitive groups category.'' Additionally, based on the 
comments of State and local agencies that have used the same or a 
similar color scheme, we believe that the color orange sends an 
appropriate health message and yet a strong message that the standard 
has been exceeded. One State commenter noted that their environmental 
agency:

has been using a green/yellow/orange/red communication system since 
1993. The media has used the red, orange and yellow air quality 
codes to convey a ``the air is not clean'' message. In general, the 
media has used Code Red to convey a message that air pollution is or 
will be at a near emergency level. Code Orange has connoted ``very 
dirty.'' Code Yellow has, in general, been used to characterize air 
pollution as not too bad--but still not clean. (Docket No. A-98-20, 
IV-G-13).

    Another State commenter noted:

    We disagree, however, with * * * [the] assertion that the ``Code 
Orange'' message in the PSI does not adequately protect public 
health. Our experience * * * has been that the health message can be 
effectively delivered for Code Orange levels. We have received much 
feedback from the general public about our ozone action day program, 
and the resounding message has been: Thank you for this program, I 
can now plan my day to avoid exposure to high levels of ozone. 
(Docket No. A-98-20, IV-G-05).

    In addition, ozone mapping projects have successfully represented 
air quality using the full AQI color scheme. In the Ozone Mapping 
Project, described in section I.C.2, the proposed AQI color scheme was 
used successfully during the 1998 O3 season. Participating 
State and local agencies and regional organizations have selected the 
same color scheme for use in the 1999 O3 season. Having used 
the proposed color scheme in their local O3 map, one 
metropolitan air agency noted that ``EPA's proposed color scheme 
communicates clearly in a logical progression which in our experience 
is already understood by the public and the media.'' (Docket No. A-98-
20, IV-G-11).
    Because we believe the proposed color scheme effectively and 
appropriately communicates the health effects message that was the 
basis for setting the O3 and PM standards, we have adopted 
the color scheme as proposed. However, we strongly agree with the views 
expressed by commenters that it is important for the health effects 
message associated with the category ``unhealthy for sensitive groups'' 
to be effectively communicated to the public, health care providers and 
the media. It is very important that members of sensitive groups, which 
for some pollutants includes healthy children and adults, be alerted to 
potential health risks and that the general public be motivated to take 
emissions reductions measures when air quality is above the level of 
the standard. In response to the concerns expressed by these 
commenters, we are planning to significantly step up the development of 
education and outreach materials and increase activities to get this 
message out, as discussed in section II.D below.
    Only two commenters recommended against requiring specific colors. 
The first commenter did so on the grounds that requiring specific 
colors would be unenforceable, and may lead to frustration and 
conflict. While applauding our goal of establishing a consistent 
message, and agreeing that it is good to have as much national 
consistency as possible, this commenter noted that efforts to legislate 
aesthetics are uncomfortable, unwieldy and ultimately unnecessary. 
(Docket No. A-98-20, IV-D-11). The second commenter noted that some 
States may elect to use Code Red for ozone action programs at levels 
other than what is being proposed and the regulation should not 
preclude them from doing that. (Docket No. A-98-20, IV-D-19). On the 
other hand, there was very strong support in the comments for us to 
require that agencies that use color, use specific colors in AQI 
reporting. All of the other commenters that addressed this issue, 
including a commenter from an environmental organization, supported 
requiring specific colors for all State/local agencies using a color 
format. The commenter from an environmental group noted:

    EPA states that revisions to the PSI have as a goal the creation 
of a nationally uniform link across a range of programs. We urge 
that this uniformity be achieved through the use of a national 
public health warning system that is clear to the public. To this 
end, we do support the EPA requiring that when colors are used by a 
state in its PSI, that the same color system incorporated in the 
PSI, and not variants, be utilized by such state. (Docket No. A-98-
20, IV-D-21).

    One of the many State commenters agreeing with us that such a 
requirement was necessary for national uniformity, noted that 
``Specific colors * * * associated with each category should be 
required for national uniformity and ease of understanding. Anything 
less would defeat the purpose of a national index for comparing air 
quality in different locales.'' (Docket No. A-98-20, IV-D-07). Another 
State commenter made the point that ``Consistency of message is 
important, especially if the regional nature of many air pollution 
problems is to be communicated effectively.'' (Docket No. A-98-20, IV-
D-01).
    In response to the first commenter's objections, we do not believe 
that requiring specific colors presents any particular enforceability 
problems. This requirement is one of many contained in the 40 CFR part 
58 Ambient Air Quality Surveillance requirements and would be 
enforceable in the same manner and to the same extent as any other 
requirement of this section. As such, we believe there is no difference 
in enforceability between this and a requirement for the use of 
particular descriptors or air quality index values. We expect to work 
with EPA Regional Offices to ensure that they monitor State 
implementation of the revised AQI and work with the States to encourage 
compliance.
    With regard to comments that our requirement would preclude States 
from using other color schemes and action levels in their voluntary 
programs, it is important to note that the AQI addresses the reporting 
of measured air quality and does not impose any requirements or 
limitations on community action programs based on air quality 
forecasts. We recognize that a nationally uniform color scheme for AQI 
reporting will, as a practical matter, complicate a State's efforts to 
use other color schemes in action programs based on predicted air 
quality, but they remain free to do so under our regulations.
    Because it is the fundamental goal of the AQI to provide nationally 
uniform information about daily air quality and the public health 
messages that are appropriately associated with various daily air 
quality levels, in a format that is timely and easily understood, we 
continue to believe that requiring specified colors when the AQI 
categories are reported in color format is both necessary and 
appropriate. Neither of the commenters opposing this requirement 
addressed how a more flexible approach of recommending specific colors, 
thereby allowing the use of different colors to represent the same 
range of air quality, would satisfy the statutory language requiring a 
nationally uniform air quality index. Therefore, we are adopting the 
requirement, as specified in appendix G below, that when State and 
local agencies report the AQI in a color format, that the specific 
colors listed in Table 1 be associated with each category.
    b. Reporting requirements. We received significant comments on 
several issues related to the reporting requirements, including the 
population threshold and other aspects of the reporting requirements, 
the appropriate

[[Page 42540]]

method of monitoring and reporting the PM sub-indices, the effect of 
AQI changes relative to the SHL program, and the effective date of the 
final rule. Since we received no significant comments on our proposal 
to change the rounding conventions for calculating the index to make 
them consistent with the rounding conventions used in defining the 
NAAQS, we are adopting that revision as proposed. With regard to the 
population threshold, one commenter expressed the view that the change 
from requiring AQI reporting in urbanized areas with a population 
greater than 200,000, to requiring reporting in MSAs with populations 
greater than 350,000, would raise the threshold for the requirement and 
appear to mean that large segments of the U.S. population would not 
have access to AQI reporting. (Docket No. A-98-20, IV-D-03). We have 
adopted the requirement for AQI reporting in MSAs with populations 
greater than 350,000 to be consistent with the State/Local Air 
Monitoring Stations (SLAMs) monitoring regulations in 40 CFR part 58, 
since AQI reporting is based on information from SLAMS monitors that 
are located and reported within the context of MSAs. The use of MSAs 
also provides for more stable reporting areas since MSAs are usually 
defined by county boundaries that typically do not change, whereas the 
boundaries for urbanized areas are very irregular, may include parts of 
counties, and may change with each census. In selecting the MSA 
population threshold of 350,000, we tried to make the new reporting 
requirement equivalent to the old one. Under the new requirement, 
virtually the same number of cities will be required to report the AQI 
as were previously. Because urbanized areas and MSAs are not 
equivalent, we realize that some areas will be required to report the 
AQI that were not required to do so before this rulemaking, and vice 
versa. The regulation does not preclude any area from reporting the 
AQI, and we encourage State and local air agencies to report the AQI 
whenever possible so that people will be informed about local air 
quality.
    Another commenter noted that some MSAs fall within the boundaries 
of more than one State, and requested that we identify which of the two 
or more reporting agencies would be responsible for reporting the AQI 
for the MSA. (Docket No. A-98-20, IV-G-15). We expect that decisions 
about AQI reporting in multi-State MSAs will be made by participating 
agencies in the same manner as decisions about activities to implement 
the standards through the State Implementation Plans (SIPs). Guidance 
for air quality planning and implementation in MSAs that fall within 
the boundaries of more than one State generally calls for the 
participating State and local agencies to identify, in the SIPs for 
those States, who will be responsible for the preparation and 
submission of the required elements, including AQI reports. Where a 
local or regional planning organization has been designated to carry 
out such requirements, such an organization is the appropriate one to 
report the AQI. In any case, we encourage AQI reporting on the sub-MSA 
level, especially where the AQI differs within the MSA.
    Another commenter urged us to expand the requirement for AQI 
reporting to areas with populations less than 350,000, if these areas 
are likely not to be in attainment for the 8-hour O3 
standard. To support this position, the commenter noted that 
O3 can be transported long distances downwind from where it 
is generated, resulting in serious air quality problems in downwind 
rural and smaller urban areas. (Docket No. A-98-20, IV-G-27). We agree 
with this commenter that downwind areas may be significantly affected 
by transport of O3 and precursors. In section 5 of appendix 
G, we encourage States to evaluate air quality in affected areas 
downwind of MSAs to identify the potential for significant transport-
related air quality impacts and to expand their AQI reporting to 
address these situations. We have also changed the language in this 
section such that the affected area need not be contiguous to the 
reporting MSA.
    On a related topic, one commenter noted an example in which a MSA 
with a population greater than 350,000, has not registered AQI values 
in excess of 50 (such that AQI reporting would be discretionary), 
although values above 100 are registered infrequently at a national 
monument within the larger air basin. (Docket No. A-98-20, IV-G-17). 
This commenter requested that we revise the reporting requirements to 
add an air quality consideration to the population threshold as a 
second component of AQI reporting. To address one part of this comment, 
we encourage State and local air agencies to report the AQI and issue 
forecasts for national parks or monuments whenever possible, since 
these are places people go to for activities that often involve 
prolonged or vigorous exertion, thereby increasing the risk from air 
pollution. We have worked with the National Park Service to develop 
appropriate guidance for visitors and staff to use when index values 
are expected to be above 100 for O3. To address the other 
part of this comment, section 8 of appendix G describes exceptions 
under which AQI reporting becomes discretionary, either for one 
pollutant or the entire index, for areas with good air quality. 
Regarding these exceptions, a State commenter suggested that we require 
a minimum of 2 years at an AQI value lower than 50 before allowing 
agencies to ``opt out'' of reporting the AQI for a particular 
pollutant, so that for example, one unusually good O3 season 
would not make it possible for an agency to avoid reporting high index 
values in subsequent O3 seasons. (Docket No. A-98-20, IV-D-
06). We believe that requiring 2 years of index values lower than 50 
before allowing State and local agencies discretion in reporting, while 
appropriate in some situations, may be unnecessary in others. We agree 
with this commenter that it is appropriate to require reporting of 
higher index values, even if air quality has been good throughout the 
previous year. Therefore, we have revised section 8 of appendix G, such 
that when the criteria for an exemption are no longer met, the 
responsible agency is required to report the AQI. Another commenter 
expressed the view that we should strengthen the minimum notification 
requirements, so that when the AQI value exceeds 100, State and local 
agencies are required to report the index to all three media (print, 
radio and television) to help ensure that the public is informed that 
the standard has been exceeded. (A-98-20, IV-E-3) We agree that it is 
important to inform the public when the AQI is above 100, and therefore 
have strengthened the reporting provisions in section 6 of appendix G. 
In particular, when the AQI exceeds 100, reporting agencies should 
expand reporting to all major news media, and at a minimum, should 
include notification to the media with the largest market coverages for 
the area in question.
    Looking at these reporting provisions more broadly, we believe that 
it would be very beneficial for reporting agencies to educate the media 
about alternative sources for this information, such as web sites and 
community action programs. Many State and local agencies have web sites 
that provide quick access to timely and accurate air quality and 
related information. For State and local agencies participating in the 
Ozone Mapping Project, the media could be directed to the AIRNOW web 
site as a source of information about O3 air quality and 
associated health effects for yesterday, today and tomorrow. In 
addition, this web site provides in-depth information about 
O3 health effects, sources of emissions and simple

[[Page 42541]]

measures people can take to improve air quality. Community action 
programs also provide timely and accurate information, and are often 
used to inform the public when air quality is predicted to be above an 
index value of 100. Tools and programs such as these can significantly 
improve the timeliness of AQI reporting and provide additional useful 
information. We believe that, in the near future, the AQI will be 
reported by the regional and national media in ways, such as the Ozone 
Map, that will not be limited to specific MSAs. This type of approach 
will help provide AQI reporting for areas that would otherwise not be 
covered, including, in some cases, rural and small urban areas and 
national parks.
    Regarding reporting the PM sub-indices, one commenter requested 
that we clarify whether PM2.5 and PM10 should be 
treated as one pollutant (e.g., reported simply as PM) or two different 
pollutants (e.g., reported separately). (Docket No. A-98-20, IV-D-19). 
We expect State and local air agencies to report PM2.5 and 
PM10 separately, since there are two separate sub-indices 
with different sensitive groups, and different health effects and 
cautionary statements. In response to this comment, we have added 
clarifying language to section 9 in appendix G. In addition, many 
commenters noted that at the present time there is very little 
monitoring for PM (both PM2.5 and PM10) that is 
suitable for use in daily AQI reports, and requested guidance for the 
use of non-reference methods for the purpose of AQI reporting. Since PM 
is often measured at intervals longer than every 24-hours, State and 
local agencies are encouraged to use monitoring data from continuous PM 
monitors for use in AQI reporting, whenever possible. As noted by 
commenters, due to the lack of appropriate monitoring information, at 
this time it may not be possible to report the AQI for PM in many 
locations. To assist State and local agencies in the use of non-
reference methods, we have added language to section 10 of appendix G 
stating that non-reference methods may be used for the purpose of AQI 
reporting if it is possible to demonstrate a simple linear relationship 
between the non-reference and the reference methods.
    Regarding the effect of changes to the AQI on the SHL program, we 
received two significant comments. One commenter noted that our 
proposed changes to the categories, to standardize them such that the 
upper bound falls on an even number, rounded to 50 (e.g., 200), and 
lower bound falls on an odd number (e.g., 201), resulted in the AQI 
breakpoint of 200 being the upper bound of the ``unhealthy'' category, 
rather than the lower bound of the ``very unhealthy'' category, as it 
has been historically. Since the AQI breakpoint of 200 is also commonly 
used as the ``Alert Level,'' or the first stage of an air pollution 
emergency episode in example guidance associated with the SHL program, 
this commenter requested that we leave the AQI value of 200 as the 
lower breakpoint of the ``very unhealthy'' category, so that emergency 
episodes would start when air quality is classified as ``very 
unhealthy'' and include appropriate-sounding health effects and 
cautionary statements. (Docket No. A-98-20, IV-D-22). We are adopting 
the breakpoints as proposed, because we believe that it is important to 
be consistent in the treatment of the category boundaries (e.g., 51 to 
100, 101 to 150, 151 to 200, etc.). When we propose revisions to the 
requirements of the SHL program, we plan to change all references to 
the ``Alert Level'' so they will refer to air quality that exceeds the 
``Alert Level,'' rather than to air quality that reaches the ``Alert 
Level.'' However, State and local agencies should not change their 
emergency episode plans at this point simply because we are adopting 
this consistent approach to setting AQI breakpoints. Eventually, some 
agencies may have to revise emergency episode plans because we have 
revised the AQI value of 200 for the 8-hour O3 sub-index. 
But we do not expect States to make any revisions to their emergency 
episode plans until we promulgate the revised requirements. Finally, 
several commenters noted that in the proposal, we did not specify an 
effective date for the final revisions. Some of these commenters 
suggested that we extend the effective date, with suggestions ranging 
from 60 days to more than a year after publication. We are adopting an 
effective date of 60 days after publication. We believe that this will 
allow adequate time for State and local agencies to revise daily AQI 
reports. We recognize that it may take longer to revise related 
informational materials, such as printed documents, or related programs 
that agencies may want to revise. However, since this rulemaking 
applies only to the requirements for daily reporting of air quality, we 
believe an effective date of 60 days is adequate.
    c. Index name. All commenters that expressed a view on the index 
name supported changing the name of the index from the Pollutant 
Standards Index (PSI) to the Air Quality Index (AQI), because this name 
clearly identifies the index as relating to the quality of the air. 
Accordingly, we are changing the name of the index to the Air Quality 
Index, or AQI.
2. Comments and Responses on Changes to the Sub-Indices.
    All of the comments we received on proposed changes to the sub-
indices focused on the sub-indices that were added for O3 
(8-hour) and PM2.5. Since we did not receive specific 
comments on the conforming changes we proposed to the CO, 
SO2 and PM10 sub-indices, we are adopting these 
sub-indices as proposed.
    a. Ozone sub-index. We received significant comments on two issues 
related to the O3 sub-index. The first group of comments was 
in response to our request for comment on retaining the 1-hour 
O3 sub-index in addition to the 8-hour O3 sub-
index. The second group of comments focused on the appropriateness of 
providing precautionary language below the level of the 8-hour 
O3 standard. Regarding the 1-hour sub-index, almost all of 
the comments that addressed this issue supported retaining the 1-hour 
O3 sub-index. However, one State commenter expressed the 
view that the proposal was unclear regarding how areas that have not 
attained the 1-hour O3 standard are to use the new 8-hour 
O3 sub-index. This commenter also noted that it might be 
confusing to report the AQI based on the 8-hour O3 sub-index 
in an area where the 1-hour O3 standard had not yet been 
attained. (Docket No. A-98-20, IV-D-07). We are requiring that all 
State and local agencies that report the AQI for O3 
calculate the 8-hour O3 sub-index, even if the reporting 
area has not attained the 1-hour standard. In addition to calculating 
the 8-hour O3 sub-index, which is required, the reporting 
agency may also calculate the 1-hour O3 sub-index, but this 
is not required. However, if the reporting agency calculates both 
O3 sub-index values, it is required to report the higher 
index value of the two. The AQI does not relate to attainment status; 
rather, it is a tool for reporting daily air quality and associated 
health information. We are retaining the 1-hour O3 sub-index 
only because we recognize that there are a very small number of areas 
in the U.S. that have atypical air quality patterns, with very high 1-
hour daily peak O3 concentrations relative to 8-hour average 
concentrations. In such areas, an index value greater than 100 might be 
calculated using the 1-hour sub-index, even when the 8-hour sub-index 
might be below 100. For these areas, the use of the 1-hour sub-index is 
clearly more precautionary. Because our major interest is that 
appropriate precautionary messages be issued, we

[[Page 42542]]

are not retaining a complete 1-hour O3 sub-index with 
``good'' and ``moderate'' categories. Likewise, when ambient 8-hour 
O3 concentrations are greater than 0.374 ppm, reporting 
agencies must calculate the index value using the 1-hour O3 
sub-index. This is because no human health effects information is 
available for higher 8-hour average O3 concentrations to use 
as a basis for selecting 8-hour breakpoints and for developing 
appropriate health effects and cautionary statements. We believe that 
since State and local agencies are required to report the name of the 
pollutant responsible for an index value greater than 100, but not the 
associated averaging period, using the 8-hour O3 sub-index 
should not be confusing in areas that have not yet attained the 1-hour 
O3 standard.
    Regarding the issue of alerting sensitive individuals below the 
level of the 8-hour O3 standard, some commenters not only 
suggested adding a category below the level of the standard, but also 
suggested reducing the lower bound of the ``moderate'' category. 
(Docket No. A-98-20, IV-D-11, IV-D-17, IV-D-19, IV-G-21). We are not 
adding a category below the level of the standard as discussed in 
section II.B.1. above. However, to be somewhat more precautionary, we 
have expanded the ``moderate'' range by reducing the lower bound of 
this category from 0.070 ppm to 0.065 ppm O3, 8-hour 
average. We believe that setting the breakpoint between the ``good'' 
and ``moderate'' categories at this lower level, is appropriate, based 
in part on risk estimates done in conjunction with the review of the 
O3 NAAQS which suggested that risk to healthy people likely 
becomes negligible at this level (Whitfield et al., 1996). This change 
is also responsive to comments from State agencies that the proposed 
range of the ``moderate'' category was so narrow (spanning only 15 ppb 
O3, as compared to 20 ppb range used in the Ozone Map in 
1998) that it would be more difficult to forecast accurately and also 
would provide too quick a transition from good to unhealthy. (Docket 
No. A-98-20, IV-D-10, IV-G-04). Conversely, an industry group and a 
State commenter took exception to issuing a ``limited health notice'' 
for O3 that we proposed as the purpose of the ``moderate'' 
category. (Docket No. A-98-20, IV-D-12, IV-G-14). The State commenter 
objected to the use of the term ``health notice'' below the level of 
the standard because it implies that the standard is not protective of 
public health. In addition to stating that the ``limited health 
notice'' associated with moderate air quality is inconsistent with the 
8-hour O3 standard because the standard is intended to 
protect public health, even the health of sensitive populations, with 
an adequate margin of safety, the industry commenter expressed the view 
that we should omit from our materials the health effects and 
cautionary statements suggesting that air quality meeting the level of 
the standard is a threat to health. We agree with the industry and 
State commenters that since the 8-hour O3 standard is 
intended to protect public health, including the health of sensitive 
groups, with an adequate margin of safety, that the term ``limited 
health notice'' may be misleading. However, we continue to believe that 
it is appropriate to provide guidance with cautionary language for 
extremely sensitive individuals, not populations or groups, below the 
level of the standard. This approach is consistent with the advice of 
CASAC, and the way we discussed expanding the use of the AQI, 
specifically to caution extremely sensitive individuals below the level 
of the O3 standard, in the O3 proposal and final 
decision notices.
    b. PM2.5 sub-index. We received a number of comments 
regarding the PM2.5 sub-index, almost all of them focusing 
on our proposal to set the index value of 100 at the level of the 24-
hour standard (65 g/m3). Some commenters 
recommended setting an index value of 100, or otherwise providing for 
cautionary messages, at concentrations lower than 65 g/
m3. One commenter, for example, stated that under the 
proposal ``many areas of the country will likely violate the annual 
standard of 15 g/m3 without ever (or hardly ever) 
reaching a PSI of 100 or a category indicating some degree of 
unhealthfulness. This situation will result in an inconsistent and 
inappropriate message to the public, especially given the severe health 
effects associated with fine particles.'' (Docket No. A-98-20, IV-D-
11).
    In light of these comments, we have reexamined the basis for 
selecting PM2.5 AQI breakpoints and agree that the sub-index 
as proposed would not adequately caution sensitive groups about 
potential risks associated with short-term exposures to 
PM2.5. This is essentially because the proposed 
PM2.5 sub-index was developed using the Agency's historical 
approach to selecting index breakpoints, which on examination does not 
correspond well with the way the PM2.5 standards were 
intended to function. The historical practice has been simply to set 
the AQI value of 100 at the level of the short-term standard for a 
pollutant (in this case, the 24-hour PM2.5 standard) and the 
AQI value of 50 at the level of the annual standard, if there is one, 
or at one-half the level of the short-term standard.8 This 
method of structuring the index is appropriate for a ``typical'' suite 
of air-quality standards, which includes a short-term standard designed 
to protect against the health effects associated with short-term 
exposures and an annual standard designed to protect against health 
effects associated with long-term exposures. In such cases, the short-
term standard in effect defines the level of health protection provided 
against short-term risks and thus is a useful benchmark against which 
to compare daily air-quality concentrations.
---------------------------------------------------------------------------

    \8\ See 63 FR 67819, 67829 (Dec. 9, 1998).
---------------------------------------------------------------------------

    In the case of the PM2.5 standards, however, EPA took a 
different approach to protecting against health risks associated with 
short-term exposures. For reasons discussed in the preamble to the 
final standards, the annual and 24-hour PM2.5 standards were 
designed to work together for this purpose, and the intended level of 
protection against short-term risk is not defined by the 24-hour 
standard but by the combination of the two standards working in 
concert. Indeed, the annual PM2.5 level of 15 g/
m3 was intended to serve as the principal vehicle for 
protection against short-term PM2.5 exposures (by reducing 
the entire distribution of PM2.5 concentrations in an area), 
with the short-term standard serving essentially to provide 
supplemental protection in special situations. 9 Given the 
respective roles of the two standards, setting the AQI value of 100 at 
the level of the 24-hour standard would not reflect the short-term 
health risks associated with lower concentrations, which the annual 
standard was designed to address. Accordingly, we agree that it is 
appropriate to caution members of sensitive groups below the level of 
the 24-hour standard and believe this should be done in a way that 
reflects the intended roles of both standards in protecting against 
short-term risks.
---------------------------------------------------------------------------

    \9\ See 62 FR 38669-71, 38676-77 (July 18, 1997).
---------------------------------------------------------------------------

    It would also be inappropriate to compare daily air-quality 
concentrations directly with the level of the annual standard (by 
setting the AQI value of 100 at that level), because the annual 
standard represents an average of many daily concentrations rather than 
daily values per se. In the circumstances, we believe the guiding 
principle for PM2.5 should be to set the AQI value of 100 in 
a way that, at least conceptually, reflects the general level of health 
protection against short-term risks

[[Page 42543]]

provided by the annual and 24-hour standards in combination. This 
approach, although inexact, is consistent with the historical approach, 
in that the underlying logic of that approach, as applied to a typical 
suite of standards, is also to set the AQI value of 100 in a way that 
reflects the level of protection provided against short-term risks--
that is, by setting it at the level of the short-term standard that 
provides the protection. In the case of PM2.5, as indicated 
above, the level of the 24-hour standard (65 g/m3) 
is too high to reflect the intended level of protection, and the level 
of the annual standard (15 g/m3) is too low. 
Between the two values, the available health studies indicate a 
continuum of risks associated with increasing PM concentrations, 
although with significant uncertainties as to the extent of the risk 
associated with single peak exposures.10 Consistent with 
EPA's general practice of setting AQI breakpoints in symmetrical 
fashion where health effects information does not suggest particular 
levels,11 we concluded that it is appropriate to set the AQI 
value of 100 at the mid-point of the range between the annual and the 
24-hour PM2.5 standards (40 g/m3). Given 
that decision, we also concluded that it is appropriate to retain the 
level of the annual standard for an AQI value of 50, as proposed, and 
to set the AQI level of 150 at the level of the 24-hour standard.
---------------------------------------------------------------------------

    \10\ See 62 FR 38670, 38677 (July 18, 1997).
    \11\ See 63 FR 67824, 67832 (Dec. 9, 1998).
---------------------------------------------------------------------------

    To reiterate, the purpose of setting the AQI value of 100 somewhat 
below the level of the 24-hour standard was to reflect the dual role of 
the annual and 24-hour PM2.5 standards in protecting against 
short-term risks, and the aim was to select a breakpoint that would 
serve as a rough surrogate for the general level of protection provided 
by the two standards in combination. Given the nature of the standards 
and the available health information, a more exact approach was not 
possible. In this regard, setting the breakpoint at the mid-point of 
the range between the annual and 24-hour standards, as opposed to a 
level somewhat higher or lower within that range, simply reflected 
EPA's general practice of setting symmetrical breakpoints as indicated 
above, and does not imply any sort of health-effects threshold. In 
particular, it does not reflect a judgment about the extent of the risk 
associated with single peak concentrations of PM2.5, as to 
which the available health information is inconclusive, or the level at 
which EPA might set a 24-hour standard if the annual standard did not 
serve as the primary vehicle for protection against such 
concentrations. As with other AQI breakpoints, it also has no effect on 
the degree of control required of specific sources.
    In short, EPA's decision to treat the annual standard as the 
principal vehicle for protecting against short-term PM2.5 
concentrations, although judged to be the best approach based on the 
available health information, does present a different situation than 
that involved in previous AQI rulemakings. As discussed in the preamble 
to the final standards, the annual standard was intended to reduce all 
PM2.5 concentrations, including short-term peaks, in an area 
sufficiently to protect public health with an adequate margin of 
safety, aside from special situations which the 24-hour standard was 
designed to address. As one commenter suggested, however, it would be 
possible for an area to violate the annual standard without ever 
experiencing (or seldom experiencing) daily peaks that exceeded the 
level of the 24-hour standard. Moreover, it might be difficult, if not 
impossible, to predict in advance whether the annual standard will be 
attained in a given area. For these reasons, as well as the 
uncertainties in the available health information, it is inherently 
difficult to judge the significance of single peak concentrations when 
they occur. In view of the various uncertainties involved, particularly 
sensitive individuals may wish to avoid exposure to such 
concentrations, especially concentrations that approach the level of 
the 24-hour standard. To facilitate such choices, consistent with the 
purposes of the AQI and the advice of CASAC, we believe that cautioning 
members of sensitive groups in the range of 40 to 65 g/
m3 is appropriate.
    We did not receive any comments on the proposal to establish a 
concentration of 500 g/m3 to be associated with a 
PM2.5 index value of 500, or our method of selecting the 
intermediate breakpoints. Therefore, we are adopting 500 g/
m3 as the upper bound of the index.12 For 
intermediate breakpoints in the AQI between values of 150 and 500, we 
have adopted PM2.5 concentrations that generally reflect a 
linear relationship between increasing index values and increasing 
PM2.5 values. As discussed in the proposal, the generally 
linear relationship between AQI values and PM2.5 
concentrations in this range, rounded to increments of 50 g/
m3 to reflect the approximate nature of such a relationship, 
is consistent with the health effects evidence that was the basis for 
the PM standards.
---------------------------------------------------------------------------

    \12\ As discussed in the proposal, should the final SHL for 
PM2.5, when promulgated, be different from this 
concentration, we will revise this PM2.5 sub-index 
accordingly.
---------------------------------------------------------------------------

C. What Are the Final Revisions?

    The sub-sections below only summarize changes to the regulatory 
text. They do not describe all aspects of 40 CFR part 58.50 or appendix 
G.
1. What Are the General Changes?
    Based on the proposed structure of the AQI, the comments we 
received and our responses to them, as discussed above, we are adopting 
the following changes to the general structure and reporting 
requirements to the AQI.
    a. Categories and related descriptors, index values and colors. We 
are adopting the index values, descriptors and associated colors listed 
in Table 1 above.
    b. Reporting requirements. We are revising 40 CFR 58.50 to require 
reporting of the AQI in all MSAs with a population over 350,000. In 
appendix G, we are adopting rounding conventions to be used to 
calculate index values that are consistent with the rounding 
conventions used in defining the NAAQS for each pollutant.
    The final rule retains the requirements to identify the area for 
which the AQI is being reported, the time period covered by the report, 
the ``critical'' pollutant for which the reported AQI value was 
derived, the AQI value, and the associated category descriptor. The 
final rule adds two requirements: (1) To report the associated category 
color if a color format is used and, (2) to report the pollutant-
specific sensitive group for any reported index value greater than 100. 
The final rule encourages, but does not require, that AQI reports 
include: appropriate health effects and cautionary statements, all AQI 
values greater than 100, the AQI for sub-divisions of the MSA (if there 
are important differences in air quality across sub-divisions of the 
MSA), possible causes for high index values, and the actual pollutant 
concentrations.
    In the case of rural or small urban areas that are significantly 
affected by pollutants transported from a MSA where the AQI is 
reported, the final rule recommends that the MSA report the AQI for the 
affected areas as well. In addition, when the AQI is greater than 100, 
reporting agencies should expand AQI reporting to include all major 
news media. The final rule continues to allow agencies to discontinue 
reporting for any pollutant, if index values for that pollutant have 
been below 50 for an entire season or a year. However, if in subsequent 
years pollutant levels rise

[[Page 42544]]

such that index values for that pollutant would be above 50, then the 
final rule requires that AQI reporting for that pollutant resume. The 
final rule emphasizes the importance of forecasting the AQI by 
specifying that forecasted values should be reported, when possible, 
but does not require that forecasted values be reported.
    c. Index name. We are adopting the name the Air Quality Index or 
AQI.
2. What Are the Changes to the Sub-Indices?
    Based on the proposed sub-indices, the comments we received and our 
responses to them, as discussed above, we are adopting new sub-indices 
corresponding to the 8-hour O3 standard and the 
PM2.5 standards, as well as conforming changes to the CO, 1-
hour O3, PM10, and SO2 sub-indices. 
The adopted breakpoints for the O3 (8-hour and 1-hour) 
PM2.5, PM10, CO and SO2 sub-indices 
are listed in Table 3.

                                           Table 3.--Breakpoints for O3, PM2.5, PM10, CO, and SO2 Sub-indices
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                              O3                                        PM
                                    -------------------------------------------------------------------------------------
             AQI value                                                                     PM2.5, 24-hr     PM10, 24-hr   CO, 8-hr (ppm)    SO2, 24-hr
                                                  8-hr (ppm)                1-hr (ppm)     (g/    (g/                        (ppm)
                                                                                                m3)             m3)
--------------------------------------------------------------------------------------------------------------------------------------------------------
50.................................  0.06...............................  ..............              15              50               4            0.03
100................................  0.08...............................            0.12              40             150               9            0.14
150................................  0.10...............................            0.16              65             250              12            0.22
200................................  0.12...............................            0.20           * 150             350              15            0.30
300................................  0.40 (1-hr)........................            0.40           * 250             420              30            0.60
400................................  0.50 (1-hr)........................            0.50           * 350             500              40            0.80
500................................  0.60 (1-hr)........................            0.60           * 500             600              50           1.00
--------------------------------------------------------------------------------------------------------------------------------------------------------
* If a different SHL for PM2.5 is promulgated, these numbers will be revised accordingly.

    These sub-indices are presented in more detail in appendix G to 
reflect the changes to the numerical rounding conventions for 
calculating index values.

D. What Are the Related Informational Materials?

    The primary documents associated with the AQI and this rulemaking, 
are our guidance on AQI reporting, ``Guideline for Public Reporting of 
Daily Air Quality--Air Quality Index (AQI)'' (EPA 1999a), and our 
guidance on AQI forecasting, ``Guideline for Developing an Ozone 
Forecasting Program'' (EPA 1999b). These documents are available on 
AIRLINKS (http://www.epa.gov/airlinks). The AQI Reporting document 
contains information regarding the AQI requirements and 
recommendations, example AQI reports, and a list of MSAs required to 
report the AQI. It also includes pollutant-specific health effects and 
cautionary statements for use with the index, for O3, 
PM2.5, PM10, CO, and SO2. The AQI 
Forecasting document explains the steps necessary to start an air 
pollution forecasting program. Included in the document is guidance on 
using hourly O3 concentrations as predictors for 8-hour 
averages.
    Other related informational materials are also available. The 
brochure ``The Pollutant Standards Index'' (EPA 1994) contained general 
information about the health effects and air quality, and general 
precautions that sensitive groups and the general public can take to 
avoid exposures of concern. It is being revised to be consistent with 
the new name (i.e., the Air Quality Index brochure), with final 
revisions to the AQI, and will identify sensitive groups in the health 
effects statements for each of the pollutants, and include the 
pollutant-specific health effects and cautionary statements discussed 
above. A colorful fact sheet, called the ``Air Quality Guide,'' 
provides information about the AQI, O3 health effects and 
the sources of ground-level O3 is available on the AIRNOW 
web site. A revised booklet, ``SMOG--Who Does It Hurt?,'' provides 
information for the general public about O3 health effects 
and is based on scientific information gained in the recent review of 
the O3 standard. ``SMOG--Who Does It Hurt?'' was designed to 
provide, in simple language, enough detail for individuals to 
understand who is at most risk from O3 exposure and why, the 
nature of O3 health effects, and a detailed explanation of 
how individuals can reduce the likelihood of exposure using common 
everyday activities as examples. We are also developing a shorter, 
summary pamphlet about O3 health effects to complement the 
``SMOG--Who Does It Hurt?'' booklet. We expect the AQI brochure, 
``SMOG--Who Does It Hurt?'' and the shorter summary pamphlet about 
O3 health effects to be available in paper format and on the 
AIRNOW web site early in the 1999 ozone season. In addition, we will 
translate the Air Quality Guide, the AQI brochure, ``SMOG--Who Does It 
Hurt?'', and the shorter summary pamphlet into Spanish. These materials 
will be available on a Spanish page on the AIRNOW web site.
    There are other materials available on the AIRNOW web site that 
provide general information about O3. Information about 
ground-level as contrasted to stratospheric O3 may be found 
in EPA's publication ``Ozone: Good Up High, Bad Nearby.'' The EPA's 
video, ``Ozone Double Trouble'' also provides information about ground-
level and stratospheric O3 and the health effects associated 
with exposure to ground-level O3, or smog.
    In addition to the products discussed above, to address the 
concerns of commenters that when air quality is in the ``unhealthy for 
sensitive groups'' range the public will not understand that the 
standard has been exceeded or who is at risk, we are going to 
significantly increase education and outreach related to the AQI. At 
this point, we are still in the process of planning specific new 
products or activities, but have decided what general direction these 
efforts will take. First, we plan to increase our contacts with the 
news providers to better inform them about the importance of including 
accurate, timely and understandable information in their broadcasts and 
reporting, and to enlist them as full partners in the implementation of 
the AQI. Second, we plan to form new associations with health care 
providers to keep them informed about air pollution health effects, 
since these professionals are the most trusted source of health effects 
information. Third, we plan to increase direct outreach to the public 
through a variety of means, including materials tailored to school-age 
children, the Spanish-speaking community, and others. Finally, we plan 
to work with public health interest organizations to support

[[Page 42545]]

their efforts to provide more immediate and interactive education and 
outreach to all of these groups.

III. Regulatory and Environmental Impact Analyses

A. Executive Order 12866: OMB Review of ``Significant Actions''

    Under Executive Order 12866, the Agency must determine whether a 
regulatory action is ``significant'' and, therefore, subject to Office 
of Management and Budget (OMB) review and the requirements of the 
Executive Order. The order defines ``significant regulatory action'' as 
one that may:
    (1) Have an annual effect on the economy of $100 million or more or 
adversely affect in a material way the economy, a sector of the 
economy, productivity, competition, jobs, the environment, public 
health or safety, or State, local, or tribal governments or 
communities;
    (2) Create a serious inconsistency or otherwise interfere with an 
action taken or planned by another Agency;
    (3) Materially alter the budgetary impact of entitlements, grants, 
user fees, or loan programs or the rights and obligations or recipients 
thereof; or
    (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. The EPA has determined that the revisions to air 
quality index reporting in this final rule would not 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, and therefore did not 
prepare a regulatory impact assessment. The OMB has advised us this 
final decision should be construed as a ``significant regulatory 
action'' within the meaning of Executive Order 12866. Accordingly, this 
action was submitted to the OMB for review. Any changes made in 
response to OMB suggestions or recommendations will be documented in 
the public record and made available for public inspection at EPA's Air 
and Radiation Docket Information Center (Docket No. A-98-20).

B. Regulatory Flexibility Analysis/Small Business Regulatory 
Enforcement Fairness Act

    Under the Regulatory Flexibility Act (RFA), 5 U.S.C. 601 et seq., 
EPA must prepare a regulatory flexibility analysis assessing the impact 
of any proposed or final rule on small entities. Under 6 U.S.C. 605(b), 
this requirement may be waived if EPA certifies that the rule will not 
have a significant economic impact on a substantial number of small 
entities. Small entities include small businesses, small not-for-profit 
enterprises, and governmental entities with jurisdiction over 
populations less than 50,000 people.
    Today's final decision to revise the AQI program modifies existing 
air quality reporting requirements for MSA's with populations over 
350,000 people. Today's final decision will not establish any new 
regulatory requirements affecting small entities. On the basis of the 
above considerations, EPA certifies that today's final decision will 
not have a significant economic impact on a substantial number of small 
entities within the meaning of the RFA. Based on the same 
considerations, EPA also certifies that the new small-entity provisions 
in section 244 of the Small Business Regulatory Enforcement Fairness 
Act (SBREFA) do not apply.

C. Unfunded Mandates Reform Act

    Title II of the Unfunded Mandates Reform Act of 1995 (UMRA), Public 
Law 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 to State, local and tribal governments, in 
the aggregate, or to the private sector, of $100 million or more in any 
1 year. In addition, 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.
    The EPA has determined that today's final decision would not 
include a Federal mandate that may result in estimated costs of $100 
million in any 1 year to either State, local, or tribal governments, in 
the aggregate, or to the private sector. Accordingly, EPA has 
determined that the provisions of section 202 of the UMRA do not apply 
to this rulemaking. With regard to section 203 of the UMRA, EPA has 
determined that this rule contains no regulatory requirements that 
might significantly or uniquely affect small governments. This rule 
requires reporting of the Air Quality Index only in MSAs with 
populations greater than 350,000, and therefore does not affect small 
governments.

D. Paperwork Reduction Act

    Today's final decision does not establish any new information 
collection requirements beyond those which are currently required under 
the Ambient Air Quality Surveillance Regulations in 40 CFR part 58 (OMB 
#2060-0084, EPA ICR No. 0940.15). Therefore, the requirements of the 
Paperwork Reduction Act do not apply to today's action.

E. Executive Order 13045: Children's Health

    Executive Order 13045, entitled ``Protection of Children from 
Environmental Health Risks and Safety Risks'' (62 FR 19885, April 23, 
1997), requires Federal agencies to ensure that their policies, 
programs, activities, and standards identify and assess environmental 
health and safety risks that may disproportionately affect children. To 
respond to this order, agencies must explain why the regulation is 
preferable to other potentially effective and reasonably feasible 
alternatives considered by the agency. In today's final decision, EPA 
identified children as one of the sensitive groups which may be at 
increased risk of experiencing the effects of concern following 
exposure to O3, PM2.5 and NO2.5. The 
AQI categories, descriptors, and health effects and cautionary 
statements as proposed, for the first time reflect consideration of the 
increased health risk to children which may result from such exposures. 
Promulgation of the proposed AQI is one potentially effective 
alternative that was considered. However, based on comments that the 
public may not be aware that healthy, active children are included in 
the sensitive groups for O3, PM2.5 and 
NO2, we have adopted the additional requirement that 
reporting agencies must include a pollutant-specific statement of the 
sensitive groups when an index value of 100 is exceeded. For example, 
when reporting an AQI value of 110 for ozone, the reporting agency must 
include a statement that children and people with asthma are the groups 
most at risk. Whenever the AQI value is above 100 for a pollutant, and 
children are one of the sensitive groups for that pollutant, the AQI 
report must include a statement

[[Page 42546]]

that children are at risk. Therefore, today's action does comply with 
the requirements of E.O. 13045.

F. Executive Order 12848: 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 in the United 
States.
    The nature of today's action is to inform the general public, 
including minorities and low-income populations, about the nature of 
the air pollution in the areas in which they live. Today's action 
establishes a uniform tool for States to use to develop programs which 
will caution particularly sensitive people to minimize their exposures 
and educate the public about general health effects associated with 
exposure to different pollution levels. States may also use information 
established as part of the AQI to trigger programs designed to reduce 
emissions to avoid exceedances of the NAAQS. Therefore, today's action 
will help facilitate public participation, outreach, and communication 
in areas where environmental justice issues are present.

G. Executive Order 12875: Enhancing Intergovernmental Partnerships

    Under Executive Order 12875, EPA may not issue a regulation that is 
not required by statute and that creates a mandate upon a State, local 
or tribal government, unless the Federal government provides the funds 
necessary to pay the direct compliance costs incurred by those 
governments, or we will consult with those governments. If EPA complies 
by consulting, Executive Order 12875 requires us to provide to OMB a 
description of the extent of our prior consultation with 
representatives of affected State, local and tribal governments, the 
nature of their concerns, copies of any written communications from the 
governments, and a statement supporting the need to issue the 
regulation. In addition, Executive Order 12875 requires us to develop 
an effective process permitting elected officials and other 
representatives of State, local and tribal governments ``to provide 
meaningful and timely input in the development of regulatory proposals 
containing significant unfunded mandates.''
    Today's rule implements requirements set forth in section 319 of 
the Act and thus is required by statute. This rule does not establish a 
wholly new requirement but rather modifies existing reporting 
requirements which State and local governments have been implementing 
for approximately 20 years. While these changes are significant in many 
ways, they are not expected to result in a significant increase in 
reporting burdens. Nonetheless, EPA engaged in extensive consultation 
with State and local governments in the development of the proposed and 
final rules, and this consultation is discussed and documented 
elsewhere in today's notice and in the notice of proposed rulemaking.

H. Executive Order 13084: Consultation and Coordination With Indian 
Tribal Governments

    Under Executive Order 13084, EPA may not issue a regulation that is 
not required by statute, that significantly or uniquely affects the 
communities of Indian tribal governments, and that imposes substantial 
direct compliance costs on those communities, unless the Federal 
government provides the funds necessary to pay the direct compliance 
costs incurred by the tribal governments, or EPA will consult with 
those governments. If EPA complies by consulting, Executive Order 13084 
requires us to provide to OMB, in a separately identified section of 
the preamble to the rule, a description of the extent of our prior 
consultation with representatives of affected tribal governments, a 
summary of the nature of their concerns, and a statement supporting the 
need to issue the regulation. In addition, Executive Order 13084 
requires us to develop an effective process permitting elected 
officials and other representatives of Indian tribal governments ``to 
provide meaningful and timely input in the development of regulatory 
policies on matters that significantly or uniquely affect their 
communities.''
    Today's rule implements requirements specifically set forth by the 
Congress in section 319 of the Act without the exercise of any 
discretion by us. Accordingly, the requirements of section 3(b) of 
Executive Order 13084 do not apply to this rule.
    This rule governs the reporting of air quality by States for MSAs 
and, in some cases, areas that are significantly affected by transport 
of pollutants from MSAs. In extensive public and intergovermental 
coordination efforts during the development of the proposal, EPA 
received no information which would suggest that the rule will impose 
new requirements on Indian tribal governments nor will it significantly 
or uniquely affect communities of Indian tribal governments. To the 
extent that air pollution from upwind MSAs significantly affects any 
lands within Indian country, this impact is not a result of, or 
affected by, today's rule and would be addressed under existing 
requirements governing the implementation of air quality standards.

I. National Technology Transfer and Advancement Act

    Section 12(d) of the National Technology Transfer and Advancement 
Act of 1995 (NTTAA), Public Law 104-113, section 12(d) (15 U.S.C. 272 
note) directs EPA to use voluntary consensus standards in its 
regulatory activities unless to do so would be inconsistent with 
applicable law or otherwise impractical. Voluntary consensus standards 
are technical standards (e.g., materials specifications, test methods, 
sampling procedures, and business practices) that are developed or 
adopted by voluntary consensus standards bodies. The NTTAA directs EPA 
to provide Congress, through OMB, explanations when the Agency decides 
not to use available and applicable voluntary consensus standards. This 
action does not involve technical standards. Therefore, EPA did not 
consider the use of any voluntary consensus standards.

J. Congressional Review Act

    The Congressional Review Act, 5 U.S.C. 801 et seq., as added by the 
Small Business Regulatory Enforcement Fairness Act of 1996, generally 
provides that before a rule may take effect, the agency promulgating 
the rule must submit a rule report, which includes a copy of the rule, 
to each House of the Congress and to the Comptroller General of the 
United States. The EPA will submit 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 the publication of the rule in the Federal Register. This rule is 
not a ``major rule'' as defined by 5 U.S.C. 804(2).

IV. References

CEQ, (1976) A Recommended Air Pollution Index, report prepared by 
the Federal Interagency Task Force on Air Quality Indicators, 
Council on Environmental Quality, Environmental Protection Agency, 
and Department of Commerce.
EPA, (1994) Measuring Air Quality: The Pollutant Standards Index, 
U.S. Environmental Protection Agency, Office of Air Quality Planning 
and Standards (MD-10), Research Triangle Park, NC, 27711, EPA 451/K-
94-001.

[[Page 42547]]

EPA, (1999a) Guideline for Public Reporting of Daily Air Quality--
Air Quality Index (AQI), U.S. Environmental Protection Agency, 
Office of Air Quality Planning and Standards, Research Triangle 
Park, NC, 27711, EPA-454/R-99-010.
EPA, (1999b) Guideline for Developing an Ozone Forecasting Program, 
U.S. Environmental Protection Agency, Office of Air Quality Planning 
and Standards, Research Triangle Park, NC, 27711, EPA-454/R-99-009.
EPA, (1999c) The Air Quality Index, U.S. Environmental Protection 
Agency, Office of Air Quality Planning and Standards, Research 
Triangle Park, NC, 27711, in preparation.
Science Applications International Corporation, (1998) Report of 
Eight Focus Groups on the Ozone Map, the Pollutant Standards Sub-
index for Ozone, and the Ozone Health Effects Booklet, Science 
Applications International Corporation, McLean, VA.
U.S. Department of Commerce, (1998) Statistical Abstract of the 
United States, U.S. Bureau of the Census.
Whitfield, R.G.; Biller, W.F.; Jusko, M.J.; Keisler, JM (1996) A 
probabilistic assessment of health risks associated with short-term 
exposure to tropospheric ozone. Report prepared for U.S. EPA, OAQPS. 
Argonne National Laboratory; Argonne, IL.
Wolff, G.T., (1995) Letter from Chairman of the Clean Air Scientific 
Advisory Committee to the EPA Administrator, dated November 30, 
1995. EPA-SAB-CASAC-LTR-96-002.

List of Subjects in 40 CFR Part 58

    Environmental protection, Air pollution control, Intergovernmental 
relations, Reporting and recordkeeping requirements.

    Dated: July 23, 1999.
Carol M. Browner,
Administrator.

    Accordingly, 40 CFR part 58 is amended as follows:

PART 58--AMBIENT AIR QUALITY SURVEILLANCE

    1. The authority citation for part 58 continues to read as follows:

    Authority: 42 U.S.C. 7410, 7601(a), 7613, and 7619.

    2. Section 58.50 is revised to read as follows:


Sec. 58.50  Index reporting.

    (a) The State shall report to the general public through prominent 
notice an air quality index in accordance with the requirements of 
appendix G to this part.
    (b) Reporting is required by all Metropolitan Statistical Areas 
with a population exceeding 350,000.
    (c) The population of a Metropolitan Statistical Area for purposes 
of index reporting is the most recent decennial U.S. census population.
    3. Appendix G to part 58 is revised to read as follows:

Appendix G to Part 58--Uniform Air Quality Index (AQI) and Daily 
Reporting

General Requirements

    1. What is the AQI?
    2. Why report the AQI?
    3. Must I report the AQI?
    4. What goes into my AQI report?
    5. Is my AQI report for my MSA only?
    6. How do I get my AQI report to the public?
    7. How often must I report the AQI?
    8. May I make exceptions to these reporting requirements?

Calculation

    9. How does the AQI relate to air pollution levels?
    10. Where do I get the pollutant concentrations to calculate the 
AQI?
    11. Do I have to forecast the AQI?
    12. How do I calculate the AQI?

Background and Reference Materials

    13. What additional information should I know?

General Requirements

1. What Is the AQI?

    The AQI is a tool that simplifies reporting air quality to the 
general public. The AQI incorporates into a single index 
concentrations of 5 criteria pollutants: ozone (O3), 
particulate matter (PM), carbon monoxide (CO), sulfur dioxide 
(SO2), and nitrogen dioxide (NO2). The scale 
of the index is divided into general categories that are associated 
with health messages.

2. Why Report the AQI?

    The AQI offers various advantages:
    a. It is simple to create and understand.
    b. It conveys the health implications of air quality.
    c. It promotes uniform use throughout the country.

3. Must I Report the AQI?

    You must report the AQI daily if yours is a metropolitan 
statistical area (MSA) with a population over 350,000.

4. What Goes Into My AQI Report?

    i. Your AQI report must contain the following:
    a. The reporting area(s) (the MSA or subdivision of the MSA).
    b. The reporting period (the day for which the AQI is reported).
    c. The critical pollutant (the pollutant with the highest index 
value).
    d. The AQI (the highest index value).
    e. The category descriptor and index value associated with the 
AQI and, if you choose to report in a color format, the associated 
color. Use only the following descriptors and colors for the six AQI 
categories:

                        Table 1.--AQI Categories
------------------------------------------------------------------------
           For this AQI             Use this descriptor   And this color
----------------------------------------------------------------1-------
0 to 50..........................  ``Good''............  Green.
------------------------------------------------------------------------
51 to 100........................  ``Moderate''........  Yellow.
------------------------------------------------------------------------
101 to 150.......................  ``Unhealthy for       Orange.
                                    Sensitive Groups''.
------------------------------------------------------------------------
151 to 200.......................  ``Unhealthy''.......  Red.
------------------------------------------------------------------------
201 to 300.......................  ``Very Unhealthy''..  Purple.
------------------------------------------------------------------------
301 and above....................  ``Hazardous''.......  Maroon.\1\
------------------------------------------------------------------------
1 Specific colors can be found in the most recent reporting guidance
  (Guideline for Public Reporting of Daily Air Quality--Air Quality
  Index (AQI)).

    f. The pollutant specific sensitive groups for any reported 
index value greater than 100. Use the following sensitive groups for 
each pollutant:

------------------------------------------------------------------------
 When this pollutant has an index value  Report these sensitive groups *
            above 100 * * *                            * *
------------------------------------------------------------------------
Ozone..................................  Children and people with asthma
                                          are the groups most at risk.
------------------------------------------------------------------------
PM2.5..................................  People with respiratory or
                                          heart disease, the elderly and
                                          children are the groups most
                                          at risk.
------------------------------------------------------------------------
PM10...................................  People with respiratory disease
                                          are the group most at risk.
------------------------------------------------------------------------
CO.....................................  People with heart disease are
                                          the group most at risk.
------------------------------------------------------------------------
SO2....................................  People with asthma are the
                                          group most at risk.
------------------------------------------------------------------------

[[Page 42548]]


NO2....................................  Children and people with
                                          respiratory disease are the
                                          groups most at risk.
------------------------------------------------------------------------

    ii. When appropriate, your AQI report may also contain the 
following:
    a. Appropriate health and cautionary statements.
    b. The name and index value for other pollutants, particularly 
those with an index value greater than 100.
    c. The index values for sub-areas of your MSA.
    d. Causes for unusual AQI values.
    e. Actual pollutant concentrations.

5. Is My AQI Report for My MSA Only?

    Generally, your AQI report applies to your MSA only. However, if 
a significant air quality problem exists (AQI greater than 100) in 
areas significantly impacted by your MSA but not in it (for example, 
O3 concentrations are often highest downwind and outside 
an urban area), you should identify these areas and report the AQI 
for these areas as well.

6. How Do I Get My AQI Report to the Public?

    You must furnish the daily report to the appropriate news media 
(radio, television, and newspapers). You must make the daily report 
publicly available at one or more places of public access, or by any 
other means, including a recorded phone message, a public Internet 
site, or facsimile transmission. When the AQI value is greater than 
100, it is particularly critical that the reporting to the various 
news media be as extensive as possible. At a minimum, it should 
include notification to the media with the largest market coverages 
for the area in question.

7. How Often Must I Report the AQI?

    You must report the AQI at least 5 days per week. Exceptions to 
this requirement are in section 8 of this appendix.

8. May I Make Exceptions to These Reporting Requirements?

    i. If the index value for a particular pollutant remains below 
50 for a season or year, then you may exclude the pollutant from 
your calculation of the AQI in section 12.
    ii. If all index values remain below 50 for a year, then you may 
report the AQI at your discretion. In subsequent years, if pollutant 
levels rise to where the AQI would be above 50, then the AQI must be 
reported as required in sections 3, 4, 6, and 7 of this appendix.

Calculation

9. How Does the AQI Relate to Air Pollution Levels?

    For each pollutant, the AQI transforms ambient concentrations to 
a scale from 0 to 500. The AQI is keyed as appropriate to the 
national ambient air quality standards (NAAQS) for each pollutant. 
In most cases, the index value of 100 is associated with the 
numerical level of the short-term standard (i.e., averaging time of 
24-hours or less) for each pollutant. Different approaches are taken 
for NO2, for which no short-term standard has been 
established, and for PM2.5, for which the annual standard 
is the principal vehicle for protecting against short-term 
concentrations. The index value of 50 is associated with the 
numerical level of the annual standard for a pollutant, if there is 
one, at one-half the level of the short-term standard for the 
pollutant, or at the level at which it is appropriate to begin to 
provide guidance on cautionary language. Higher categories of the 
index are based on increasingly serious health effects and 
increasing proportions of the population that are likely to be 
affected. The index is related to other air pollution concentrations 
through linear interpolation based on these levels. The AQI is equal 
to the highest of the numbers corresponding to each pollutant. For 
the purposes of reporting the AQI, the sub-indexes for 
PM10 and PM2.5 are to be considered 
separately. The pollutant responsible for the highest index value 
(the reported AQI) is called the ``critical'' pollutant.

10. Where Do I Get the Pollutant Concentrations To Calculate the 
AQI?

    You must use concentration data from population-oriented State/
Local Air Monitoring Station (SLAMS) or parts of the SLAMS required 
under 40 CFR 58.20 for each pollutant except PM. For PM, you need 
only calculate and report the AQI on days for which you have 
measured air quality data (e.g., particulate monitors often report 
values only every sixth day). You may use particulate measurements 
from monitors that are not reference or equivalent methods (for 
example, continuous PM10 or PM2.5 monitors) if 
you can relate these measurements by statistical linear regression 
to reference or equivalent method measurements.

11. Do I Have to Forecast the AQI?

    You should forecast the AQI to provide timely air quality 
information to the public, but this is not required. If you choose 
to forecast the AQI, then you may consider both long-term and short-
term forecasts. You can forecast the AQI at least 24-hours in 
advance using the most accurate and reasonable procedures 
considering meteorology, topography, availability of data, and 
forecasting expertise. The document ``Guideline for Developing an 
Ozone Forecasting Program'' (the Forecasting Guidance) will help you 
start a forecasting program. You can also issue short-term forecasts 
by predicting 8-hour ozone values from 1-hour ozone values using 
methods suggested in the Reporting Guidance, ``Guideline for Public 
Reporting of Daily Air Quality.''

12. How Do I Calculate the AQI?

    i. The AQI is the highest value calculated for each pollutant as 
follows:
    a. Identify the highest concentration among all of the monitors 
within each reporting area and truncate the pollutant concentration 
to one more than the significant digits used to express the level of 
the NAAQS for that pollutant. This is equivalent to the rounding 
conventions used in the NAAQS.
    b. Using Table 2, find the two breakpoints that contain the 
concentration.
    c. Using Equation 1, calculate the index.
    d. Round the index to the nearest integer.

                                                            Table 2.--Breakpoints for the AQI
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                             These breakpoints                                                Equal these AQIs * *
-----------------------------------------------------------------------------------------------------------------------*-----------
                                                                       PM10                                                               Category
         O3 (ppm)  8-hour          O3 (ppm)  1-   PM2.5  (g/    CO (ppm)     SO2 (ppm)     NO2 (ppm)      AQI
                                      hour 1          m>g/m3)           m3)
--------------------------------------------------------------------------------------------------------------------------------------------------------
0.000-0.064......................  ............   0.0-15.4            0-54       0.0-4.4      0.000-0.034       (2)       0-50      Good.
0.065-0.084......................  ............  15.5-40.4          55-154       4.5-9.4      0.035-0.144       (2)       51-100    Moderate.
0.085-0.104......................  0.125-0.164   40.5-65.4         155-254       9.5-12.4     0.145-0.224       (2)       101-150   Unhealthy for
                                                                                                                                     sensitive groups.
0.105-0.124......................  0.165-0.204   4 65.5-150.4      255-354       12.5-15.4    0.225-0.304       (2)       151-200   Unhealthy.
0.125-0.374......................  0.205-0.404   4 150.5-250.4     355-424       15.5-30.4    0.305-0.604    0.65-1.24    201-300   Very unhealthy.
(3)..............................  0.405-0.504   4 250.5-350.4     425-504       30.5-40.4    0.605-0.804    1.25-1.64    301-400   ....................
(3)..............................  0.505-0.604   4 350.5-500.4     505-604       40.5-50.4    0.805-1.004    1.65-2.04    401-500   Hazardous.
--------------------------------------------------------------------------------------------------------------------------------------------------------
1 Areas are generally required to report the AQI based on 8-hour ozone values. However, there are a small number of areas where an AQI based on 1-hour
  ozone values would be more precautionary. In these cases, in addition to calculating the 8-hour ozone index value, the 1-hour ozone index value may be
  calculated, and the maximum of the two values reported.

[[Page 42549]]


2 NO2 has no short-term NAAQS and can generate an AQI only above an AQI value of 200.
3 8-hour O3 values do not define higher AQI values ( 301). AQI values of 301 or higher are calculated with 1-hour O3 concentrations.
4 If a different SHL for PM2.5 is promulgated, these numbers will change accordingly.

    ii. If the concentration is equal to a breakpoint, then the 
index is equal to the corresponding index value in Table 2. However, 
Equation 1 can still be used. The results will be equal. If the 
concentration is between two breakpoints, then calculate the index 
of that pollutant with Equation 1. You must also note that in some 
areas, the AQI based on 1-hour O3 will be more 
precautionary than using 8-hour values (see footnote 1 to Table 2). 
In these cases, you may use 1-hour values as well as 8-hour values 
to calculate index values and then use the maximum index value as 
the AQI for O3.
[GRAPHIC] [TIFF OMITTED] TR04AU99.044

Where:

Ip = the index value for pollutantp
Cp = the truncated concentration of          
pollutantp
BPHi = the breakpoint that is greater than or equal to 
Cp
BPLo = the breakpoint that is less than or equal to 
Cp
IHi = the AQI value corresponding to BPHi
Ilo = the AQI value corresponding to BPLo.

    iii. If the concentration is larger than the highest breakpoint 
in Table 2 then you may use the last two breakpoints in Table 2 when 
you apply Equation 1.

Example

    iv. Using Table 2 and Equation 1, calculate the index value for 
each of the pollutants measured and select the one that produces the 
highest index value for the AQI. For example, if you observe a 
PM10 value of 210 g/m3, a 1-hour 
O3 value of 0.156 ppm, and an 8-hour O3 value 
of 0.130 ppm, then do this:
    a. Find the breakpoints for PM10 at 210 g/
m3 as 155 g/m3 and 254 g/
m3, corresponding to index values 101 and 150;
    b. Find the breakpoints for 1-hour O3 at 0.156 ppm as 
0.125 ppm and 0.164 ppm, corresponding to index values 101 and 150;
    c. Find the breakpoints for 8-hour O3 at 0.130 ppm as 
0.125 ppm and 0.374 ppm, corresponding to index values 201 and 300;
    d. Apply Equation 1 for 210 g/m3, 
PM10:
[GRAPHIC] [TIFF OMITTED] TR04AU99.045

    e. Apply Equation 1 for 0.156 ppm, 1-hour O3:
    [GRAPHIC] [TIFF OMITTED] TR04AU99.046
    
    f. Apply Equation 1 for 0.130 ppm, 8-hour O3:
    [GRAPHIC] [TIFF OMITTED] TR04AU99.047
    
    g. Find the maximum, 203. This is the AQI. The minimal AQI 
report would read:
    v. Today, the AQI for my city is 203 which is very unhealthy, 
due to ozone. Children and people with asthma are the groups most at 
risk.

Background and Reference Materials

13. What Additional Information Should I Know?

    The EPA has developed a computer program to calculate the AQI 
for you. The program works with Windows 95, it prompts for inputs, 
and it displays all the pertinent information for the AQI (the index 
value, color, category, sensitive group, health effects, and 
cautionary language). The EPA has also prepared a brochure on the 
AQI that explains the index in detail (The Air Quality Index), 
Reporting Guidance (Guideline for Public Reporting of Daily Air 
Quality) that provides associated health effects and cautionary 
statements, and Forecasting Guidance (Guideline for Developing an 
Ozone Forecasting Program) that explains the steps necessary to 
start an air pollution forecasting program. You can download the 
program and the guidance documents at www.epa.gov/airnow.

[FR Doc. 99-19433 Filed 8-3-99; 8:45 am]
BILLING CODE 6560-50-P