Document ID: EPA-HQ-OAR-2001-0017-3356
Agency: epa
Document Type: Rule
Title: Interpretation of the National Ambient Air Quality Standards for PM2.5--Correcting and Simplifying Amendment
Posted Date: 2008-01-09T05:00Z

[Federal Register: January 9, 2008 (Volume 73, Number 6)]
[Rules and Regulations]               
[Page 1497-1503]
From the Federal Register Online via GPO Access [wais.access.gpo.gov]
[DOCID:fr09ja08-4]                         

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ENVIRONMENTAL PROTECTION AGENCY

40 CFR Part 50

[EPA-HQ-OAR-2001-0017; FRL-8502-3]
RIN 2060-AO59

 
Interpretation of the National Ambient Air Quality Standards for 
PM2.5--Correcting and Simplifying Amendment

AGENCY: Environmental Protection Agency (EPA).

ACTION: Direct final rule.

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SUMMARY: The EPA recently finalized changes to the data handling 
conventions and computations necessary for determining when the annual 
and 24-hour national ambient air quality standards (NAAQS) for fine 
particles (generally referring to particles less than or equal to 2.5 
micrometers ([mu]m) in diameter, PM2.5) are met. These 
changes were made in support of revisions to the NAAQS for particulate 
matter (PM) that were finalized in the same rulemaking. After 
publication, EPA discovered an inadvertent omission in the rule text 
explaining the procedures for calculating the key statistic (98th 
percentile) involved with determining compliance with the 24-hour 
PM2.5 standard in locations where extra samples of 
PM2.5 in ambient air were taken above the specified sampling 
frequency. If the error in the regulatory text is left unchanged, the 
resulting statistic for calculating compliance with the 24-hour 
PM2.5 standard would be biased low at some samplers, leading 
to potentially incorrect determinations that an area was attaining the 
NAAQS. In this direct final action, EPA is correcting this error. The 
correction involves the replacement of the currently used statistical 
formula and instructions with a simpler look-up table approach which is 
easier for readers to understand and which retains the intended 
numerical consistency with EPA's historic practice.

DATES: This rule is effective on April 8, 2008 without further notice, 
unless EPA receives adverse comment by February 8, 2008. If EPA 
receives adverse comment, EPA will publish a timely withdrawal in the 
Federal Register informing the public that this direct final rule will 
not take effect.

ADDRESSES: Submit your comments, identified by Docket ID No. EPA-HQ-
OAR-2001-0017 by one of the following methods:
     http://www.regulations.gov. Follow the on-line instructions for 

submitting comments.
     E-mail: a-and-r-docket@epa.gov.
     Fax: (202) 566-9744.
     Mail: Review of the National Ambient Air Quality Standards 
(NAAQS) for Particul0ate Matter (PM), Environmental Protection Agency, 
Mailcode: 2822T, 1200 Pennsylvania Avenue, NW., Washington, DC 20460. 
Please include a total of two copies.
     Hand Delivery: EPA Docket Center, 1301 Constitution 
Avenue, NW., EPA Headquarters Library, Room 3334, EPA West Building, 
Washington, DC 20460. Such deliveries are only accepted during the 
Docket's normal hours of operation, and special arrangements should be 
made for deliveries of boxed information.
    Instructions: Direct your comments to Docket ID No. EPA-HQ-OAR-
2001-0017. The EPA's policy is that all comments received will be 
included in the public docket without change and may be made available 
online at: http://www.regulations.gov including any personal 

information provided, unless the comment includes information claimed 
to be Confidential Business Information (CBI) or other information 
whose disclosure is restricted by statute. Do not submit information 
that you consider to be CBI or otherwise protected through 
http://www.regulations.gov or e-mail. The www.regulations.gov Web site is an 

``anonymous access'' system, which means EPA will not know your 
identity or contact information unless you provide it in the body of 
your comment. If you send an e-mail comment directly to EPA without 
going through http://www.regulations.gov, your e-mail address will be 

automatically captured and included as part of the comment that is 
placed in the public docket and made available on the internet. If you 
submit an electronic comment, EPA recommends that you include your name 
and other contact information in the body of your comment and with any 
disk or CD-ROM you submit. If EPA cannot read your comment due to 
technical difficulties and cannot contact you for clarification, EPA 
may not be able to consider your comment. Electronic files should avoid 
the use of special characters, any form of encryption, and be free of 
any defects or viruses. For additional information about EPA's public 
docket, visit the EPA Docket Center homepage at http://www.epa.gov/epahome/dockets.htm
.

    Docket: All documents in the docket are listed in the 
http://www.regulations.gov index. Although listed in the index, some 

information is not publicly available, e.g., CBI or other information 
whose disclosure is restricted by statute. Certain other material, such 
as copyrighted material, will be publicly available only in hard copy. 
Publicly available docket materials are available either electronically 
in http://www.regulations.gov or in hard copy at the Review of the National 

Ambient Air Quality Standards (NAAQS) for Particulate Matter (PM) 
Docket, EPA/DC, EPA West Building, EPA Headquarters Library, Room 3334, 
Constitution Ave., NW., Washington, DC. The Public Reading Room is open 
from 8:30 a.m. to 4:30 p.m., Monday through Friday, excluding legal 
holidays. The telephone number for the Public Reading Room is (202) 
566-1744, and the telephone number for the Air Docket is (202) 566-
1742.

FOR FURTHER INFORMATION CONTACT: For general questions, please contact 
Mr. Lewis Weinstock, U.S. Environmental Protection Agency, Office of 
Air Quality Planning and Standards, Air Quality Assessment Division, 
Ambient Air Monitoring Group (C304-06), Research Triangle Park, North 
Carolina 27711; telephone number: (919) 541-3661; fax number: (919) 
541-1903; e-mail address: weinstock.lewis@epa.gov. For technical 
questions, please contact Mr. Mark Schmidt, U.S. Environmental 
Protection Agency, Office of Air Quality Planning and Standards, Air 
Quality Assessment Division, Air Quality Analysis Group (C304-04), 
Research Triangle Park, North Carolina 27711; telephone number: (919) 
541-2416; fax number: (919) 541-1903; e-mail address: 
schmidt.mark@epa.gov.

SUPPLEMENTARY INFORMATION:

Table of Contents

I. Why Is EPA Using a Direct Final Rule?
II. Does This Action Apply to Me?
III. Authority
IV. Judicial Review
V. Overview of the October 17, 2006 NAAQS Rule Changes
VI. This Action
VII. Statutory and Executive Order Reviews
    A. Executive Order 12866: Regulatory Planning and Review
    B. Paperwork Reduction Act

[[Page 1498]]

    C. Regulatory Flexibility Act
    D. Unfunded Mandates Reform Act
    E. Executive Order 13132: Federalism
    F. Executive Order 13175: Consultation and Coordination With 
Indian Tribal Governments
    G. Executive Order 13045: Protection of Children From 
Environmental Health and Safety Risks
    H. Executive Order 13211: Actions That Significantly Affect 
Energy Supply, Distribution, or Use
    I. National Technology Transfer Advancement Act
    J. Executive Order 12898: Federal Actions To Address 
Environmental Justice in Minority Populations and Low-Income 
Populations
    K. Congressional Review Act

I. Why Is EPA Using a Direct Final Rule?

    The EPA is publishing this rule to correct and simplify 40 CFR part 
50 to Appendix N, Interpretation of the National Ambient Air Quality 
Standards for PM2.5, without a prior proposed rule because 
we view this as a non-controversial action and anticipate no adverse 
comment. The change does not alter the regulatory requirements on 
affected entities that were promulgated in the final rule that was 
published in the Federal Register on October 17, 2006 (71 FR 61144). 
The amended rule also expresses EPA's actual intentions, as explained 
in that rulemaking. However, in the ``Proposed Rules'' section of 
today's Federal Register, we are publishing a separate document that 
will serve as a proposed rule if EPA receives significant adverse 
comments on this direct final rule. We will not institute a second 
comment period on this action. Any parties interested in commenting 
must do so at this time. For further information about commenting on 
this rule, see the ADDRESSES section of this document. If EPA receives 
adverse comment, we will publish a timely withdrawal in the Federal 
Register informing the public that this direct final rule will not take 
effect. We would address all public comments in any subsequent final 
rule based on the proposed rule.

II. Does This Action Apply to Me?

    Categories and entities potentially regulated by this action 
include:

------------------------------------------------------------------------
                                        NAICS     Examples of regulated
              Category                 code \1\          entities
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Federal government..................     924110  Federal agencies that
                                                  conduct ambient air
                                                  monitoring similar to
                                                  that conducted by
                                                  States under 40 CFR
                                                  part 58 and that wish
                                                  EPA to use their
                                                  monitoring data in the
                                                  same manner as State
                                                  data.
State/territorial/local/tribal           924110  State, territorial, and
 government.                                      local, air quality
                                                  management programs
                                                  that are responsible
                                                  for ambient air
                                                  monitoring under 40
                                                  CFR part 58. The
                                                  proposal also may
                                                  affect Tribes that
                                                  conduct ambient air
                                                  monitoring similar to
                                                  that conducted by
                                                  States and that wish
                                                  EPA to use their
                                                  monitoring data in the
                                                  same manner as State
                                                  monitoring data.
------------------------------------------------------------------------
\1\ North American Industry Classification System.

    This table is not intended to be exhaustive, but rather provides a 
guide for readers regarding entities likely to be regulated by this 
action. This table lists the types of entities that EPA is now aware of 
that could potentially be regulated by this action. Other types of 
entities not listed in the table could also be regulated. If you have 
questions regarding the applicability of this action to a particular 
entity, consult one of the persons listed in the preceding FOR FURTHER 
INFORMATION CONTACT section.

III. Authority

    Two sections of the Clean Air Act (CAA) govern the establishment 
and revision of the NAAQS and supporting appendices detailing 
associated Federal Reference Methods and NAAQS interpretation (data 
handling) procedures.
    Section 108 (42 U.S.C. 7408) directs the Administrator to identify 
and list ``air pollutants'' that ``in his judgment, may reasonably be 
anticipated to endanger public health and welfare'' and whose 
``presence * * * in the ambient air results from numerous or diverse 
mobile or stationary sources'' and to issue air quality criteria for 
those that are listed. Air quality criteria are intended to 
``accurately reflect the latest scientific knowledge useful in 
indicating the kind and extent of identifiable effects on public health 
or welfare which may be expected from the presence of [a] pollutant in 
ambient air * * *.''
    Section 109 (42 U.S.C. 7409) directs the Administrator to propose 
and promulgate ``primary'' and ``secondary'' NAAQS for pollutants 
listed under section 108. Section 109(b)(1) defines a primary standard 
as ``the attainment and maintenance of which in the judgment of the 
Administrator, based on such criteria and allowing an adequate margin 
of safety, are requisite to protect the public health.'' A secondary 
standard, as defined in section 109(b)(2), must ``specify a level of 
air quality the attainment and maintenance of which, in the judgment of 
the Administrator, based on such criteria, is requisite to protect the 
public welfare from any known or anticipated adverse effects associated 
with the presence of [the] pollutant in the ambient air.''

IV. Judicial Review

    Under section 307(b)(1) of the Clean Air Act (CAA), judicial review 
of this direct final rule is available only by filing a petition for 
review in the U.S. Court of Appeals for the District of Columbia 
Circuit by March 10, 2008. Under section 307(d)(7)(B) of the CAA, only 
an objection to this direct final rule that was raised with reasonable 
specificity during the period for public comment can be raised during 
judicial review. Moreover, under section 307(b)(2) of the CAA, the 
requirements established by this action may not be challenged 
separately in any civil or criminal proceedings brought by EPA to 
enforce these requirements.

V. Overview of the October 17, 2006 NAAQS Rule Changes

    On October 17, 2006 (71 FR 61144), EPA amended the primary and 
secondary NAAQS for PM to provide increased protection of public health 
and welfare by revising the NAAQS for PM2.5 and PM10 
(generally referring to particles less than or equal to 10 micrometers 
([mu]m) in diameter). The rule amendments also modified the data 
handling procedures associated with the PM10 and PM2.5 
NAAQS (Appendices K and N of part 50, respectively). Appendix K and N 
describe the procedures and equations for determining whether a 
monitoring site

[[Page 1499]]

meets the PM10 and PM2.5 NAAQS, respectively. 
Appendix N of part 50 (Interpretation of the National Ambient Air 
Quality Standards for PM2.5) was revised to incorporate the 
revised 24-hour NAAQS level (i.e., 35 [mu]g/m\3\), and also to make 
several notable enhancements to the previous data handling conventions 
and computations (adopted at 62 FR 38755, July 18, 1997). These 
enhancements expanded the existing instructions to include relevant 
details for certain special cases previously addressed only in a 1999 
EPA guidance document.\2\ EPA meant to make the rule text more explicit 
in order to avoid regulatory ambiguity in these special cases. The 
special cases addressed in the 1999 EPA guidance are situations in 
which a monitoring agency has performed ``make-up'' or ``supplemental'' 
sampling of PM2.5. The 1999 guidance, but not the previous 
version of Appendix N, provided details about how these samples could 
be taken into account in the calculation of design values used for 
determining whether areas are in compliance with the 24-hour PM2.5 
NAAQS.
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    \2\ Guideline on Data Handling Conventions for the PM NAAQS, 
EPA-454/R-99-008, Office of Air Quality Planning and Standards, U.S. 
Environmental Protection Agency, Research Triangle Park, NC, April 
1999. http://www.epa.gov/ttn/oarpg/t1/memoranda/pmfinal.pdf.

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    The monitoring network used for determining compliance with the 
PM2.5 NAAQS is currently based solely on filter-based 
samplers that typically operate on a 1-in-3 day sampling frequency.\3\ 
Such filter-based samplers can malfunction resulting in missed or 
invalidated samples. The 1999 guidance encouraged monitoring agencies 
to collect make-up samples \4\ for such lost data, and to use the make-
up data in the calculation of the design values for the monitoring 
site. Monitoring agencies may also collect supplemental samples on days 
falling between required sampling days for local purposes, such as to 
better understand the nature and causes of a multi-day PM2.5 
episode. The original (1997) Appendix N did not provide explicit 
procedures addressing make-up or supplemental samples. The 1999 
guidance suggested procedures for calculating design values in these 
cases which would ensure the appropriate treatment of such make-up and 
supplemental samples in the calculation of PM2.5 24-hour 
standard design values.
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    \3\ 40 CFR 58.12(d) describes the required operating schedules 
for manual PM2.5 samplers. Although the majority of such 
samplers must operate on a 1-in-3 day operating schedule, a subset 
of samplers is required to operate on a daily schedule, and samplers 
that are collocated with a continuous operating PM2.5 
monitor may be eligible for a reduction to 1-in-6 days sampling if 
approved by the Regional Administrator.
    \4\ Make-up samples are samples taken to replace missed or 
invalidated required scheduled samples. Make-up samples can be made 
by either the primary or the collocated instruments. Make-up samples 
are either taken before the next required sampling day or exactly 
one week after the missed (or voided) sampling day. The guidance 
also made other suggestions regarding make-up sampling practices.
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    As noted in the preamble to the October 17, 2006 NAAQS rulemaking, 
EPA intended to incorporate into regulation PM2.5 data 
handling procedures that previously had only been stated in guidance. 
71 FR at 61211. In the course of making these intended changes, 
however, an error was made in section 4.5 of Appendix N dealing with 
procedures and equations for calculating the 24-hour PM2.5 
NAAQS under certain conditions. As described in the following section, 
this action was inadvertent, contrary to EPA's stated intentions, and 
necessitates correction.

VI. This Action

    EPA is amending Appendix N in this action to correct the Agency's 
inadvertent error. As a result, the procedures in Appendix N will give 
results that will be identical to the intended formula (instead of the 
formula that was misstated in the October 2006 rulemaking) and also to 
the previous method that had been recommended in EPA guidance. In 
addition, this action simplifies the procedures for calculating 24-hour 
PM2.5 design values.
    As noted, EPA intended in the October 2006 final rule to codify the 
1999 guidance's procedure for avoiding a bias that could be introduced 
into calculations of the 98th percentile concentration if supplemental 
samples are unaccounted for in the statistical calculations. For 
example, if supplemental ambient samples were taken during periods of 
low PM2.5 concentrations, the annual \5\ 98th percentile 
value could be biased low using the previous (1997) Appendix N 
procedures compared with the statistic that would have been generated 
(using that same procedure) if supplemental samples were not taken or 
considered. To minimize this bias, the 1999 guidance and the October 
2006 version of Appendix N based the annual 98th percentile calculation 
on the creditable \6\ number of monitoring samples as defined in 
section 1(c) of the October 2006 version of Appendix N to 40 CFR part 
50.\7\
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    \5\ The term ``annual 98th percentile value'' refers to a 
single-year statistic required for the calculation of 24-hour 
PM2.5 design values and should not be confused with 
procedures required for calculation of the annual form of the 
PM2.5 standard that are not referenced or modified by 
this rulemaking.
    \6\ Creditable samples are samples that are given credit for 
data completeness. They include valid samples collected on required 
sampling days and valid ``make-up'' samples taken for missed or 
invalidated samples on required sampling days.
    \7\ The EPA notes that most sites do not take supplemental 
samples; hence, the total number of samples is generally equal to 
the creditable number of samples. Also, EPA notes that the 
collection of supplemental samples has a negligible impact on the 
determination of attainment for the annual PM2.5 NAAQS 
since the metric for that standard is weighted by quarter. 
Furthermore, data completeness, an integral consideration for 
evaluating attainment of a NAAQS, is based solely on creditable 
samples.
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    In the 2006 rule, EPA intended to encompass certain relevant 
details previously addressed only in the 1999 guidance by expanding the 
existing instructions in the text of Appendix N. The EPA's 1999 
guidance document recommended procedures for calculating regular annual 
PM2.5 98th percentile values for two distinct situations. 
Chapter 1 of the guidance document addressed a monitoring site which 
had sampled solely on official required sample days. One method for 
this situation simply reiterated the formula finalized in 1997 
accompanied by an example. This formula utilized a generic sample count 
(``n'') which was only appropriate when no ``extra'' (non-scheduled) 
samples were taken at the monitoring site during the year. An alternate 
method for the same situation used a table look-up approach, but again 
specified the generic ``n'' and, hence, was also only accurate when 
there were no extra samples taken during the year. Chapter 2 of the 
guidance document explained that modifications should be made to the 
stated techniques if there were extra samples present for a site-year. 
The guidance document recommended: (1) Utilizing a sample count that 
accounted for (specifically, subtracted) extra samples, and, (2) 
incorporating a term (specifically, adding) into the equation 
accounting for the extra sample count. This formula, which was 
misstated in the October 2006 rulemaking, also produced accurate 
results when no extra samples were present since the total ``n'' was 
the same as ``n'' minus ``extra samples'' or zero, and also the extra 
sample term in the equation was zero. Chapter 2 in the guidance 
document also noted that the table look-up approach in Chapter 1 still 
produced the desired result when extra samples were present if only the 
adjusted sample count (``n minus extra samples'') were used in lieu of 
the total sample count (``n''). This approach also produced accurate 
results whether extra samples were present or not.
    In the October 2006 revisions to Appendix N, EPA intended to 
incorporate the ``extra sample''

[[Page 1500]]

adjustment logic into the existing equation method (71 FR at 61211). 
The sample count reference was modified (essentially changing ``n'' to 
``n minus extra samples'') but the ``extra sample'' term was 
inadvertently omitted from equation 5 of section 4.5 (71 FR at 61229). 
That omission would cause significant miscalculations to the annual 
98th percentile value when extra samples are present if the procedure 
were explicitly followed. The presence of extra samples with the 
misstated formula would result in a low bias in ascertaining the 
single-year 98th percentile statistic, as well as in determining the 
resulting PM2.5 NAAQS comparison metric (24-hour design 
value) based on the three-year average of 98th percentile statistics. 
If implemented as explicitly stated, the misstated formula would 
improperly weaken the stringency of the 24-hour PM2.5 NAAQS 
by showing sites and areas to be in attainment of the NAAQS when they 
were actually violating the standard. This situation would result in 
the 24-hour standard no longer being sufficiently stringent in those 
areas to provide requisite protection to public health and welfare, in 
violation of the fundamental requirement for establishing NAAQS in 
section 109(b) of the Act.
    For this direct final rule, EPA considered two possible approaches 
to correct Appendix N. The first would be to correct equation 5 in 
Appendix N, section 4.5 by adding a term and footnote indicating that 
the number of extra samples, if taken, would have to be added to the 
current equation result (i.e., 1 plus the integer part of the product 
of 0.98 and the creditable number of samples) to determine where in the 
ascending data distribution to select the 98th percentile value. Such a 
correction would have restored EPA's intention of preserving numerical 
consistency with previous practice in calculating the related metrics 
for 24-hour PM2.5 design values, but would also have 
preserved a set of procedures that is sensitive to the presence of 
extra samples and is hard to apply without providing relatively complex 
instructions.
    The second possible approach would be to incorporate a table look-
up method into Appendix N instead of using an equation. The direct 
final rule uses this approach. The EPA believes that the incorporation 
of a table look-up method into the Appendix N procedures provides a 
simpler means for calculating 98th percentile values by employing a 
more intuitive descending sort procedure that is unaffected by the 
presence of extra samples in the data distribution being examined. For 
example, if the annual number of creditable samples at a 1-in-3 day 
monitor is 125, then the appropriate 98th percentile value is the third 
maximum value in the descending sort distribution as noted in the 
table. If a 1-in-6 day monitor has recorded 50 creditable samples in a 
year, then the 98th percentile value is the first maximum value in the 
descending sort distribution.
    Accordingly, the rule language of section 4.5(a)(1) of 40 CFR part 
50, Appendix N is amended to replace equation 4.5 with a data look-up 
table (table 1) that determines where in the descending sorted data 
distribution the 98th percentile value is located. EPA is also adding 
rule text to 4.5(a)(1) (labeled ``Regular procedure for identifying 
annual 98th percentile values'' in the rule) to describe the procedures 
for performing the descending sort distribution and for determining the 
appropriate range for selecting the correct 98th percentile value based 
on the creditable number of samples.
    To reiterate, this direct final rule both eliminates the erroneous 
terms in the equation, and replaces the equation-based procedure for 
determining the 98th percentile concentration with a table look-up 
approach that is equivalent to the intended equation-based procedure, 
because the table look-up approach is both correct and much easier to 
understand and execute. In fact, several public comments received on 
the proposed Appendix N procedure (the proposal underlying the 2006 
final rule) for determining 98th percentiles noted that the treatment 
of extra samples (within that procedure) was complex, confusing, and 
difficult to program. Moreover, EPA believes that the equation-based 
procedure itself, especially when the extra sample adjustment is 
properly incorporated, is more indirect and hence more confusing than 
necessary. EPA's 1999 guidance perhaps contributed to the confusion by 
describing multiple methods which could be used for calculating the 
statistical metric. Also, the equation-based procedure promulgated in 
1997 and described in the 1999 guidance utilized an ascending sorted 
data distribution which created another source of confusion. Descending 
sorts are generally utilized more frequently than ascending ones when 
characterizing air quality; for example, other criteria pollutant NAAQS 
focus on a fourth maximum concentration or a second maximum 
concentration. The alternate 98th percentile calculation method 
outlined in the 1999 guidance--the table look-up approach--utilizes 
this more intuitive descending sort. EPA based the 1999 guidance on a 
descending sort since it was thought to be more comprehensible. In 
addition (as outlined in the 1999 guidance), when extra samples were 
present at a site in a given year, the promulgated equation-based 
procedure for the 98th percentile calculation required a critical 
adjustment (an added term) to the associated equation. (As noted 
earlier, this critical adjustment is what was omitted from equation 4.5 
of Appendix N in the 2006 amendments.) However, as correctly stated in 
the 1999 guidance, when extra samples are present and the table look-up 
approach is utilized, no such adjustment is necessary. Thus, in 
conclusion and in retrospect, it would have been better if EPA had 
proposed and promulgated the table look-up approach. Now afforded a 
second opportunity because of the need to address the error of the 
missing term in the equation-based procedure, EPA is opting to switch 
to the table look-up approach in this rulemaking.
    EPA notes the retention of an equation-based procedure (equation 5 
of section 4.5(a)(2) of 40 CFR part 50, Appendix N) to account for 
sites that operate on an approved seasonal sampling schedule. An 
equation-based approach is necessary to account for the different 
number of days present in ``High'' and ``Low'' seasons.

VII. Statutory and Executive Order Reviews

A. Executive Order 12866: Regulatory Planning and Review

    This action is not a ``significant regulatory action'' under the 
terms of Executive Order 12866 (58 FR 51735, October 4, 1993) and is 
therefore not subject to review under the Executive Order.

B. Paperwork Reduction Act

    This action does not impose an information collection burden under 
the provisions of the Paperwork Reduction Act, 44 U.S.C. 3501 et seq. 
There is no information collection requirement directly associated with 
revisions to a NAAQS or supporting appendices under section 109 of the 
CAA.
    Burden means the total time, effort, or financial resources 
expended by persons to generate, maintain, retain, or disclose or 
provide information to or for a Federal agency. This includes the time 
needed to review instructions; develop, acquire, install, and utilize 
technology and systems for the purposes of collecting, validating, and 
verifying information, processing and maintaining information, and 
disclosing

[[Page 1501]]

and providing information; adjust the existing ways to comply with any 
previously applicable instructions and requirements; train personnel to 
be able to respond to a collection of information; search data sources; 
complete and review the collection of information; and transmit or 
otherwise disclose the information.
    An agency may not conduct or sponsor, and a person is not required 
to respond to a collection of information unless it displays a 
currently valid OMB control number. The OMB control numbers for EPA's 
regulations in 40 CFR are listed in 40 CFR part 9.

C. Regulatory Flexibility Act

    The Regulatory Flexibility Act (RFA) generally requires an agency 
to prepare a regulatory flexibility analysis of any rule subject to 
notice and comment rulemaking requirements under the Administrative 
Procedure Act or any other statute unless the agency certifies that the 
rule will not have a significant economic impact on a substantial 
number of small entities. Small entities include small businesses, 
small organizations, and small governmental jurisdictions.
    For purposes of assessing the impacts of today's rule on small 
entities, small entity is defined as: (1) A small business whose parent 
company has fewer than 100 or 1,000 employees, or fewer than 4 billion 
kilowatt-hr per year of electricity usage, depending on the size 
definition for the affected North American Industry Classification 
System code; (2) a small governmental jurisdiction that is a government 
of a city, county, town, school district or special district with a 
population of less than 50,000; and (3) a small organization that is 
any not-for-profit enterprise which is independently owned and operated 
and is not dominant in its field.
    After considering the economic impacts of this direct final rule on 
small entities, I certify that this action will not have a significant 
economic impact on a substantial number of small entities. This direct 
final rule will not impose any requirements on small entities because 
it does not impose any additional regulatory requirements.

D. 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 
one year. Before promulgating an EPA rule for which a written statement 
is needed, section 205 of the UMRA generally requires EPA to identify 
and consider a reasonable number of regulatory alternatives and adopt 
the least costly, most cost-effective or least burdensome alternative 
that achieves the objectives of the rule. The provisions of section 205 
do not apply when they are inconsistent with applicable law. Moreover, 
section 205 allows EPA to adopt an alternative other than the least 
costly, most cost-effective or least burdensome alternative if the 
Administrator publishes with the final rule an explanation why that 
alternative was not adopted. Before EPA establishes any regulatory 
requirements that may significantly or uniquely affect small 
governments, including Tribal governments, it must have developed under 
section 203 of the UMRA a small government agency plan. The plan must 
provide for notifying potentially affected small governments, enabling 
officials of affected small governments to have meaningful and timely 
input in the development of EPA regulatory proposals with significant 
Federal intergovernmental mandates, and informing, educating, and 
advising small governments on compliance with the regulatory 
requirements.
    This rule contains no Federal mandates (under the regulatory 
provisions of Title II of the UMRA) for State, local, or tribal 
governments or the private sector. The rule imposes no enforceable duty 
on any State, local or tribal governments or the private sector.
    The correcting and simplifying change does not create additional 
regulatory requirements on affected entities compared to those that 
were promulgated in the final rule that was published in the Federal 
Register on October 17, 2006. The rule change only corrects and 
simplifies one error in Appendix N of part 50 (Interpretation of the 
National Ambient Air Quality Standards for PM2.5). Thus, 
this final rule is not subject to the requirements of section 202 and 
205 of the UMRA.
    EPA has determined that this direct final rule contains no 
regulatory requirements that might significantly or uniquely affect 
small governments. The correcting and simplifying change does not 
create additional regulatory requirements.

E. Executive Order 13132: Federalism

    Executive Order 13132 (64 FR 43255, August 10, 1999), requires EPA 
to develop an accountable process to ensure ``meaningful and timely 
input by State and local officials in the development of regulatory 
policies that have federalism implications.'' ``Policies that have 
federalism implications'' is defined in the Executive Order to include 
regulations that have ``substantial direct effects on the States, on 
the relationship between the national government and the States, or on 
the distribution of power and responsibilities among the various levels 
of government.''
    This direct final rule does not have federalism implications. It 
will not have substantial direct effects on the States, on the 
relationship between the national government and the States, or on the 
distribution of power and responsibilities among the various levels of 
government, as specified in Executive Order 13132. The change being 
made only corrects and simplifies one error in Appendix N of part 50 
(Interpretation of the National Ambient Air Quality Standards for 
PM2.5); thus, Executive Order 13132 does not apply to this 
final rule.

F. Executive Order 13175: Consultation and Coordination With Indian 
Tribal Governments

    Executive Order 13175, entitled ``Consultation and Coordination 
with Indian Tribal Governments'' (65 FR 67249, November 9, 2000), 
requires EPA to develop an accountable process to ensure ``meaningful 
and timely input by tribal officials in the development of regulatory 
policies that have tribal implications.'' This direct final rule does 
not have tribal implications, as specified in Executive Order 13175. 
The change being made only corrects and simplifies one error in 
Appendix N of part 50 (Interpretation of the National Ambient Air 
Quality Standards for PM2.5). Thus, Executive Order 13175 
does not apply to this rule.

G. Executive Order 13045: Protection of Children From Environmental 
Health and Safety Risks

    Executive Order 13045: ``Protection of Children from Environmental 
Health Risks and Safety Risks'' (62 FR 19885, April 23,1997) applies to 
any rule that: (1) Is determined to be ``economically significant'' as 
defined under Executive Order 12866, and (2) concerns an environmental 
health or safety risk that EPA has reason to believe may have a 
disproportionate effect on children. If the regulatory action meets 
both criteria,

[[Page 1502]]

the Agency must evaluate the environmental health or safety effects of 
the planned rule on children, and explain why the planned regulation is 
preferable to other potentially effective and reasonably feasible 
alternatives considered by the Agency.
    EPA interprets Executive Order 13045 as applying only to those 
regulatory actions that are based on health or safety risks, such that 
the analysis required under section 5-501 of the Order has the 
potential to influence the regulation. This direct final rule is not 
subject to Executive Order 13045 because, while it is based on the need 
for monitoring data to characterize risk, this direct final rule itself 
does not establish an environmental standard intended to mitigate 
health or safety risks.

H. Executive Order 13211: Actions That Significantly Affect Energy 
Supply, Distribution, or Use

    This rule is not subject to Executive Order 13211, ``Actions 
Concerning Regulations That Significantly Affect Energy Supply, 
Distribution, or Use'' (66 FR 28355 (May 22, 2001)) because it is not a 
significant regulatory action under Executive Order 12866.

I. National Technology Transfer Advancement Act

    As noted in the proposed rule, Section 12(d) of the National 
Technology Transfer 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 any new technical standards for 
environmental monitoring and measurement. Ambient air concentrations of 
PM2.5 are currently measured by the Federal reference method 
in 40 CFR part 50, Appendix L (Reference Method for the Determination 
of Fine Particulate as PM2.5 in the Atmosphere) or by 
Federal Reference Method or Federal Equivalent Method that meet the 
requirements in 40 CFR part 53.

J. Executive Order 12898: Federal Actions To Address Environmental 
Justice in Minority Populations and Low-Income Populations

    Executive Order 12898 (59 FR 7629 (Feb. 16, 1994)) establishes 
federal executive policy on environmental justice. Its main provision 
directs federal agencies, to the greatest extent practicable and 
permitted by law, to make environmental justice part of their mission 
by identifying and addressing, as appropriate, disproportionately high 
and adverse human health or environmental effects of their programs, 
policies, and activities on minority populations and low-income 
populations in the United States.
    EPA has determined that this direct final rule will not have 
disproportionately high and adverse human health or environmental 
effects on minority or low-income populations because it does not 
affect the level of protection provided to human health or the 
environment. The rule merely amends the October 17, 2006, final PM 
NAAQS rule (71 FR 61144) by correcting and simplifying existing 
PM2.5 data handling conventions and computations.

K. 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. 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 publication of the rule in the Federal Register.
    A Major rule cannot take effect until 60 days after it is published 
in the Federal Register. This action is not a ``major rule'' as defined 
by 5 U.S.C. 804(2). This rule will be effective on April 8, 2008.

List of Subjects in 40 CFR Part 50

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

    Dated: November 29, 2007.
Stephen L. Johnson,
Administrator.

0
For the reasons stated in the preamble, title 40, chapter I, part 50 of 
the Code of Federal Regulations is amended as follows:

PART 50--[AMENDED]

0
1. The authority citation for part 50 continues to read as follows:

    Authority: 42 U.S.C. 7401 et seq.

0
2. Appendix N is amended by:
0
a. Revising section 2.0(c);
0
b. Revising section 4.2(c); and
0
c. Revising section 4.5, as follows:

Appendix N to Part 50--Interpretation of the National Ambient Air 
Quality Standards for PM2.5

* * * * *

2.0 Monitoring Considerations

* * * * *
    (c) Section 58.12 of this chapter specifies the required minimum 
frequency of sampling for PM2.5. Exceptions to the 
specified sampling frequencies, such as a reduced frequency during a 
season of expected low concentrations (i.e., ``seasonal sampling''), 
are subject to the approval of EPA. Annual 98th percentile values 
are to be calculated according to equation 5 in section 4.5 of this 
appendix when a site operates on a ``seasonal sampling'' schedule.
* * * * *

4.2 24-Hour PM2.5 NAAQS

* * * * *
    (c) The procedures and equations for calculating the 24-hour 
standard design values are given in section 4.5 of this appendix.
* * * * *

4.5 Procedures and Equations for the 24-Hour PM2.5 NAAQS

    (a) When the data for a particular site and year meet the data 
completeness requirements in section 4.2 of this appendix, 
calculation of the 98th percentile is accomplished by the steps 
provided in this subsection. Table 1 of this appendix shall be used 
to identify annual 98th percentile values, except that where a site 
operates on an approved seasonal sampling schedule, equation 5 of 
this appendix shall be used instead.
    (1) Regular procedure for identifying annual 98th percentile 
values. Identification of annual 98th percentile values using the 
regular procedure (table 1) will be based on the creditable number 
of samples (as described below), rather than on the actual number of 
samples. Credit will not be granted for extra (non-creditable) 
samples. Extra samples, however, are candidates for selection as the 
annual 98th percentile. [The creditable number of samples will 
determine how deep to go into the data distribution, but all samples 
(creditable and extra) will be considered when making the percentile 
assignment.] The annual creditable number of samples is the sum of 
the four quarterly creditable number of samples.
    Procedure: Sort all the daily values from a particular site and 
year by descending value. (For example: (x[1], x[2], x[3], * * *, 
x[n]).

[[Page 1503]]

In this case, x[1] is the largest number and x[n] is the smallest 
value.) The 98th percentile is determined from this sorted series of 
daily values which is ordered from the highest to the lowest number. 
Using the left column of table 1, determine the appropriate range 
(i.e., row) for the annual creditable number of samples for year y 
(cny). The corresponding ``n'' value in the right column 
identifies the rank of the annual 98th percentile value in the 
descending sorted list of daily site values for year y. Thus, 
P0.98, y = the nth largest value.

                                 Table 1
------------------------------------------------------------------------
                                             P0.98, y is the nth maximum
  Annual creditable number of samples for    value of the year, where n
             year ``y'' (cny)                   is the listed number
------------------------------------------------------------------------
1-50......................................  1
51-100....................................  2
101-150...................................  3
151-200...................................  4
201-250...................................  5
251-300...................................  6
301-350...................................  7
351-366...................................  8
------------------------------------------------------------------------

    (2) Formula for computing annual 98th percentile values when 
sampling frequencies are seasonal.
    Procedure: Calculate the annual 98th percentiles by determining 
the smallest measured concentration, x, that makes W(x) greater than 
0.98 using equation 5 of this appendix:
[GRAPHIC] [TIFF OMITTED] TR51AD07.000

Where:

dHigh = number of calendar days in the ``High'' season;
dLow = number of calendar days in the ``Low'' season;
dHigh + dLow = days in a year; and
[GRAPHIC] [TIFF OMITTED] TR51AD07.001

Such that ``a'' can be either ``High'' or ``Low''; ``x'' is the 
measured concentration; and ``dHigh/(dHigh + 
dLow) and dLow /(dHigh + 
dLow)'' are constant and are called seasonal ``weights.''
    (b) The 24-hour standard design value is then calculated by 
averaging the annual 98th percentiles using equation 6 of this 
appendix:
[GRAPHIC] [TIFF OMITTED] TR51AD07.002

    (c) The 24-hour standard design value (3-year average 98th 
percentile) is rounded according to the conventions in section 4.3 
of this appendix before a comparison with the standard is made.
[FR Doc. 07-5954 Filed 1-8 -08; 8:45 am]

BILLING CODE 6560-50-P