[Federal Register Volume 66, Number 6 (Tuesday, January 9, 2001)]
[Notices]
[Pages 1665-1668]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 01-565]


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ENVIRONMENTAL PROTECTION AGENCY

[FRL-6931-5]


National Ambient Air Quality Standards for Sulfur Oxides (Sulfur 
Dioxide); Availability of Information

AGENCY: Environmental Protection Agency (EPA).

ACTION: Notice.

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SUMMARY: The EPA is announcing today the following actions: The 
availability of new information on 5-minute average sulfur dioxide 
(SO2) concentrations in the ambient air; The status of EPA's 
ongoing activities to characterize and address 5-minute peak SO2 
levels that may pose risk to sensitive individuals with asthma, 
including plans to consider taking final action on the proposed 
intervention level program (ILP) for the reduction of SO2 
emissions published on January 2, 1997 and to respond to the remand of 
the final decision on the national ambient air quality standards 
(NAAQS) for SO2 published on May 22, 1996; The solicitation 
of comments on the new air quality information.

DATES: Comments should be submitted on or before March 12, 2001.

ADDRESSES: Comments should be submitted to Susan Lyon Stone, U.S. 
Environmental Protection Agency (MD-15), Research Triangle Park, NC 
27711; email [email protected].

FOR FURTHER INFORMATION CONTACT: Susan Lyon Stone at the same address; 
e-mail [email protected]; telephone (919) 541-1146.

SUPPLEMENTARY INFORMATION: On May 5, 1998, EPA announced its plans for 
responding to a remand of its final decision not to revise the SO2 
NAAQS (61 FR 25566, May 22, 1996) and for final action on the proposed 
ILP (62 FR 210, January 2, 1997); identified interim actions that we 
planned to take to address 5-minute peak SO2 levels that may 
pose risk to sensitive individuals; and solicited new information and 
analyses on 5-minute peak SO2 levels (63 FR 24782). The 
sensitive population for the effects of 5-minute peaks of SO2 
consists of children, adolescents and adults with mild or moderate 
asthma who are physically active outdoors. As discussed in this 1998 
notice, the primary issue in our SO2 NAAQS decision was 
whether a new 5-minute NAAQS was appropriate to protect sensitive 
individuals with asthma from the risk posed by exposure to 5-minute 
SO2 levels of 0.6 ppm or above. Given the available health 
effects information; information as to the localized, infrequent, and 
site-specific nature of the risk involved; and the advice of the Clean 
Air Scientific Advisory Committee (CASAC), the Administrator concluded 
that short-term (i.e., 5-minute) peak concentrations of SO2 
do not constitute a public health problem for which the establishment 
of a NAAQS would be appropriate.
    Consistent with our final SO2 NAAQS decision, and to 
supplement the protection provided by the existing SO2

[[Page 1666]]

NAAQS, we subsequently proposed an ILP to assist States in 
determining whether 5-minute peak concentrations of SO2 
posed a significant health risk in the local population, and if so, to 
identify appropriate remedial measures. A key element of the proposed 
ILP was the establishment of a concern level of 0.6 parts per million 
(ppm), 5-minute average SO2 concentration, and an 
endangerment level of 2.0 ppm, 5-minute average. The proposed ILP would 
require that State and tribal plans contain the authority to take 
whatever action is necessary to prevent further exceedances of such 
concern and endangerment levels when the State/tribe determines that 
intervention is appropriate. The proposed ILP includes factors that the 
State/tribe should consider in making such determinations, including 
the magnitude and frequency of peak concentrations exceeding these 
levels, the history and nature of any citizen complaints, available 
information on potential exposure of sensitive individuals with asthma, 
and information about the source(s) causing the peak SO2 
concentrations. Based on these factors, the proposed ILP provides for 
flexibility for the State/tribe to determine the nature and degree of 
intervention that is warranted in any area and to relocate existing 
SO2 monitors to areas where 5-minute peak concentrations may 
be of concern.
    On January 30, 1998, the Court of Appeals for the District of 
Columbia issued a decision in a case brought by the American Lung 
Association (ALA) and the Environmental Defense Fund, American Lung 
Association v. Browner, No. 134 F.3d 388 (D.C. Cir. 1998) (ALA) that 
challenged our decision not to establish a new 5-minute SO2 
NAAQS. The court found that we had failed to provide an adequate 
explanation for our determination that no revision to the SO2 
NAAQS was appropriate, and remanded the decision to us to more fully 
explain our decision. id. In the absence of any court-established 
deadline for EPA action, EPA agreed with ALA to finalize our response 
to the remand by the end of the year 2000 (63 FR 24782). Subsequently, 
in light of a decision by the court in another case relating to EPA's 
1997 revisions of the NAAQS for ozone and particulate matter, American 
Trucking Associations v. EPA, 175 F.3d 1027, 195 F.3d 4, cert. granted 
120 S. Ct. 2003 (U.S. May 22, 2000) (No. 9901257) (ATA), the ALA agreed 
to extend the time for us to respond to the remand of the SO2 
NAAQS decision to accommodate our need for additional time and pending 
additional court action in the ATA case.
    In conjunction with extension of this schedule, we committed to 
take a number of actions, building upon the actions discussed in our 
1998 notice (63 FR 24782). These ongoing actions focus on broadening 
our efforts to collect and analyze data on 5-minute average SO2 
concentrations, providing further guidance to States on monitoring 5-
minute SO2 concentrations around industrial sources, and 
addressing specific situations relating to short-term SO2 
exposures that are of concern in local communities. c

Availability of Information on 5-Minute SO2 
Concentrations

    This section discusses new information that is now available on 5-
minute SO2 concentrations, and includes descriptions of the 
nature of such data in EPA's Aerometric Information Retrieval System 
(AIRS) and data in other formats, and analyses that we have conducted 
of these data. Our 1998 solicitation of new information and analyses on 
5-minute peak SO2 levels (63 FR 24782) resulted in the 
submission of relatively little additional 5-minute SO2 
monitoring data. On June 30, 2000, we directly requested the assistance 
of EPA's Regional Offices and the State and Territorial Air Pollution 
Program Administrators/Association of Local Air Pollution Control 
Officers (STAPPA/ALAPCO) in obtaining any additional 5-minute 
SO2 monitoring data that may have been collected but not 
submitted to AIRS.\1\ In response to this request, we have received 
from nine States additional 5-minute SO2 monitoring data 
from more than 48 monitoring sites, recorded during the period 1994-
2000. We note, however, that the newly submitted data generally have a 
number of limitations, such that neither EPA nor the States express any 
opinions about the validity of these data at this time. More 
specifically, much of the data has been provided to us in a variety of 
formats not directly compatible with AIRS; only one State and the 
District of Columbia submitted their additional data into AIRS. Most of 
the data files lacked information on monitor location and type, or 
nearby source types, and a number of States have warned us that the 
data have not been subjected to appropriate quality assurance/quality 
control (QA/QC) procedures.\2\ To the extent possible and appropriate, 
we are working with States to address these limitations. However, at 
this time, we do not believe it is appropriate to disseminate or rely 
on these data. At such time as the data are validated, they will be 
available to the public in AIRS.
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    \1\ Robert Perciasepe, Assistant Administrator for Air and 
Radiation, to S. William Becker, Executive Director, STAPPA/ALAPCO, 
June 30, 2000; Robert Perciasepe, Assistant Administrator for Air 
and Radiation, to EPA Regional Administrators, Regions I-X, June 30, 
2000.
    \2\ For example, in our preliminary review, we have noted that a 
number of recorded values appear to have been automatically flagged 
by the data loggers as reflecting monitor malfunctions and 
calibration measurements.
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    To supplement prior assessments \3\ and improve our understanding 
of the frequency, magnitude, and number of locations at which high 5-
minute concentrations of SO2 may be occurring, we have 
undertaken analyses of the data in AIRS that include the following 
activities:
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    \3\ Prior assessments were done as part of our 1996 review of 
the SO2 NAAQS and are available in the docket for that 
rulemaking (Docket No. A-84-25).
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    (1) We have evaluated monitoring data from 83 monitoring sites 
reporting 5-minute concentrations in 14 States to determine the 
frequency of peak concentrations greater than or equal to 0.6 ppm, the 
variations of such frequencies across locations, whether there are 
industrial sources located nearby that may be contributing to measured 
peak concentrations, and the size of the surrounding population within 
a 5-km radius of the monitor.
    (2) Since we have AIRS data from far more monitoring sites (695) 
recording 1-hour average concentrations than from monitors recording 5-
minute concentrations, we have constructed and applied mathematical 
models to aid in estimating the potential for the occurrence of 5-
minute peak concentrations at and above 0.6 ppm SO2 at 
locations where only 1-hour average concentrations are available. These 
models are based on determining the relationships of 5-minute peak 
concentration distributions \4\ to 1-hour mean concentration 
distributions and evaluating the statistical strength of these 
relationships.
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    \4\ Five-minute peak concentrations are taken to be the maximum 
5-minute block average within each hour.
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    Although we intend to extend these analyses to include additional 
data to the extent they become certified for inclusion in AIRS, we have 
substantially completed the analyses described above. A draft report 
summarizing our preliminary findings has been placed on EPA's website 
at http://www.epa.gov/ttn/amtic.

Status of Ongoing Activities

    This section discusses the status of our ongoing activities to 
characterize and address 5-minute peak SO2 levels

[[Page 1667]]

that may pose risk to sensitive individuals with asthma. These 
activities include: (1) Efforts to obtain State certification of newly 
submitted 5-minute SO2 monitoring data and related 
information, to be followed by analysis of this additional certified 
data, as appropriate; (2) development of guidance on monitoring 5-
minute SO2 concentrations; (3) additional 5-minute 
SO2 air quality monitoring, in coordination with States' and 
industry's monitoring activities; (4) consideration of taking final 
action on the proposed ILP; and (5) consideration of our response to 
the remand of our 1996 SO2 NAAQS decision.
    We are now in the process of working with States who submitted new 
5-minute SO2 monitoring data to facilitate their 
certification of the data. We are also working to obtain related 
information, as appropriate, such as monitor location, nearby source 
types, and surrounding population. To the extent that such information 
warrants further analysis, we intend to extend the analyses discussed 
above to include these data, and to complete these analyses by mid-
2001.
    In a separate but related effort, we are evaluating our ambient air 
monitoring regulations and approaches. As part of a broad, integrated 
monitoring strategy for all the criteria pollutants, which we expect to 
propose late Spring 2001, we also expect to propose regulatory changes 
necessary to reflect current data needs, which in part will involve 
SO2 monitoring. We initially proposed revisions to 
regulations at 40 CFR parts 53 and 58 to modify reference and 
equivalent methods for SO2 and to revise the minimum 
requirements for ambient monitoring in compliance with the 
SO2 NAAQS in order to facilitate additional monitoring of 5-
minute concentrations (60 FR 58959, March 7, 1995). We will consider 
the input received from the earlier proposal in developing these 
changes.
    In addition, we also intend to issue a guideline specifically on 
SO2 monitoring. We have already developed a draft guideline, 
which is intended to assist State and local air pollution control 
agencies in evaluating their networks and the appropriateness of 
revising those networks to better address the potential for 5-minute 
concentrations of concern. The draft guideline provides relevant 
background information, summarizes recommended procedures for network 
review, suggested procedures for review of available ambient data to 
determine the potential for high 5-minute concentrations, and 
recommendations for short-term monitoring network design, including 
cost estimation procedures to help assess the costs of network 
revisions. This draft document may be obtained at EPA's website at 
http://www.epa.gov/ttn/amtic. In addition to these efforts, we will 
work with the States to facilitate implementation of the SO2 
monitoring guideline and the broader integrated monitoring strategy.
    We are also starting to develop plans for collecting additional 5-
minute SO2 air quality monitoring data. We intend to work 
with States and industry to elicit their support and participation in 
this project, which we expect will provide important new information as 
to the likelihood and nature of 5-minute peak SO2 
concentrations that may now be occurring around various types of 
industrial facilities. We anticipate that this project will take 
approximately two years, including planning, coordination, data 
collection and analysis. We expect that this information will help 
inform our response to the remand of the SO2 NAAQS decision 
as well as the next periodic review of the SO2 NAAQS.
    In our consideration of taking final action on the proposed ILP (62 
FR 210, January 2, 1997), we will take into account comments received 
in response to this notice as well as comments received on our 1997 
proposed action. We received 62 comments on the proposed ILP, of which 
11 comments were from State and local agencies and a related 
organization, 38 comments were from individual industry commenters and 
trade groups, four were from public advocacy groups, and four comments 
were from private citizens. Many commenters supported the proposed ILP 
and its flexible implementation strategy, while others commented that 
States already have sufficient regulatory authority to deal with 
sources emitting high 5-minute peaks of SO2 that may pose a 
risk to the health of asthmatic individuals living nearby, and 
therefore an additional regulatory program is not necessary. The 
commenters disagreed about the significance of the health effects 
associated with exposure to short-term peaks of SO2, 
particularly at the concern level (0.6 ppm SO2, 5-minute 
average). Some expressed the view that the health effects associated 
with exposures at this level are not significant enough to warrant 
remedial action, while others expressed the view that this level was 
not sufficiently health protective and urged us to set the concern 
level at a lower concentration (e.g., 0.3 ppm SO2, 5-minute 
average). Many commenters expressed concern about the costs associated 
with implementing the proposed ILP, especially when compared to the 
relatively small size of the sensitive population (i.e., individuals 
with asthma who are active outdoors) that might be affected. In 
addition, some State and local agency commenters expressed concern 
about the costs associated with the additional source-based monitoring 
(e.g., for monitor purchase, monitor relocation, or additional staff 
members) that might be needed to implement the proposed ILP.
    With regard to moving forward with a final ILP, we note that the 
results of the data analyses completed to date continue to suggest that 
there may be a number of locations in the country where repeated 
exposures to 5-minute peak SO2 levels of 0.60 ppm and above 
could pose a risk of significant health effects. Taking into account 
this information, the results of planned additional analyses, and 
public comments, we will consider taking final action on an ILP. We 
anticipate reaching a final decision on an ILP by the summer of 2001, 
as a separate matter from our consideration of our response to the 
remand of the 1996 SO2 NAAQS decision.\5\
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    \1\ Although we are in the process of considering whether to 
move forward with an ILP during the same time that we continue to 
consider our response to the remand in the ALA case, it is important 
to note that we view our ILP activities and our response to the ALA 
remand as independent actions. Our consideration of taking final 
action on the proposed ILP is not intended as a substitute for a 
decision on the ALA remand, nor is it intended to indicate that we 
have reached any particular outcome regarding the need for a revised 
SO2 NAAQS. Regardless of our decision in response to the 
ALA remand, we believe that it is appropriate at this time to 
consider taking final action on an ILP to provide any supplementary 
protection from exposures of concern to short-term SO2 
peaks that may be appropriate.
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    Since the court decision in the ALA case, remanding our decision 
not to revise the SO2 NAAQS, we have continued to take a 
number of actions relating to 5-minute SO2 peaks of 0.6 ppm 
or greater, including the solicitation and review of additional 
information and analyses described above. Although we continue to 
evaluate this and other information in light of the ALA remand, the 
ruling of the Court of Appeals for the District of Columbia Circuit in 
the ATA case, and its subsequent appeal to the United States Supreme 
Court, has created potential uncertainty regarding the appropriate 
framework for decisions under section 109. As a result, we believe that 
the better course of action is to await a decision from the Supreme 
Court, which is expected during the spring of 2001, before responding 
to the ALA remand of our SO2 NAAQS decision. This will 
better enable us to

[[Page 1668]]

review and assess all relevant information, including the court's 
opinion and any additional analyses and technical information, that 
could shed additional light on the appropriate response to the remand. 
We intend to publish our schedule for considering the relevant 
information and responding to the remand by mid-2001.

Request for Comments

    We are soliciting comments on the data analyses and preliminary 
findings in our draft report that is now available, to better inform 
future actions to reduce the health risk that may be posed by potential 
exposures of exercising asthmatics to short-term peaks of 
SO2. More specifically, we solicit comments on the 
following: the appropriateness of using 1-hour average SO2 
monitoring data as one element in our efforts to estimate the potential 
for 5-minute peak concentrations greater than or equal to 0.6 ppm 
SO2; the usefulness of these types of analyses in 
identifying the need for additional monitoring or other actions and the 
sources likely to contribute to high 5-minute SO2 
concentrations; and, for the purpose of assessing the need for 
additional monitoring around SO2 sources, the 
appropriateness of using just the hourly maximum 5-minute average 
SO2 concentrations, rather than all the 5-minute averages in 
an hour, including any relevant data storage and management 
considerations. We will consider this information in the context of 
taking final action on the proposed ILP, conducting future analyses of 
5-minute SO2 air quality data, responding to the ALA remand 
and conducting the next periodic review of the SO2 NAAQS.

    Dated: January 3, 2001.
Robert Perciasepe,
Assistant Administrator for Air and Radiation.
[FR Doc. 01-565 Filed 1-8-01; 8:45 am]
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