[Federal Register Volume 69, Number 230 (Wednesday, December 1, 2004)]
[Proposed Rules]
[Pages 69864-69878]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 04-26579]
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ENVIRONMENTAL PROTECTION AGENCY
40 CFR Parts 60 and 63
[OAR-2002-0056; FRL-7844-8]
RIN 2060-AJ65
Proposed National Emission Standards for Hazardous Air
Pollutants; and, in the Alternative, Proposed Standards of Performance
for New and Existing Stationary Sources, Electric Utility Steam
Generating Units: Notice of Data Availability
AGENCY: Environmental Protection Agency (EPA).
ACTION: Notice of data availability (NODA).
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SUMMARY: EPA issued a proposed Clean Air Mercury Rule (CAMR) under the
Clean Air Act (CAA) concerning coal- and oil-fired electric utility
steam generating units (power plants) on January 30, 2004,\1\ and a
supplemental proposal on March 16, 2004.\2\ The proposed CAMR
represents the first-ever Federal action to regulate mercury (Hg) from
this source category. The proposed rule presents two primary
alternative approaches to regulating Hg and nickel (Ni) from power
plants. EPA received numerous comments on its proposed regulatory
approaches, including comments on the modeling results EPA obtained
using the Integrated Planning Model (IPM), which is a model that
predicts how the power sector will respond to a particular regulatory
approach, and comments addressing the speciation of Hg. EPA is
currently evaluating those comments to determine how the new data and
information received in the comments, as described below, may affect
the benefit-cost analysis and regulatory options under consideration.
Although we recognize that the public has access to the comments in the
rulemaking docket, we are issuing the NODA, in part, because the Agency
received over 680,000 public comments, including almost 5,000 unique
comments, and the comments present new data and information that are
relevant to the two primary regulatory approaches addressed in the
proposed CAMR.
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\1\ 69 FR 4652, January 30, 2004.
\2\ 69 FR 12398, March 16, 2004.
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We are also issuing the NODA to seek input on our benefits
methodology, which has been preliminarily revised since the CAMR was
proposed. An analysis of benefits and costs is consistent with
principles of good government and the provisions of Executive Order
(EO) 12866. Based on comments received on the proposal and in
furtherance of our obligations under EO 12866, we have preliminarily
revised our approach to analyzing the benefits of reducing Hg emissions
from power plants, and we are seeking comment on that revised approach,
which is described in Section III below. Some of the commenters
suggested approaches that differ from EPA's proposed revised benefits
methodology. We identify those comments in Section III, as well as
other comments that we received that provide analyses relevant to our
refined benefits methodology.
DATES: Comments on the NODA must be received on or before January 3,
2005.
ADDRESSES: Comments on the NODA should be submitted to Docket ID No.
OAR-2002-0056. Comments may be submitted by one of the following
methods:
Federal eRulemaking Portal: http://www.regulations.gov.
Follow the on-line instructions for submitting comments.
Agency Web site: http://www.epa.gov/edocket. EDOCKET,
EPA's electronic public docket and comment system, is EPA's preferred
method for receiving comments. Follow the on-line instructions for
submitting comments.
E-mail: [email protected].
[[Page 69865]]
Mail: Air Docket, Clean Air Mercury Rule, Environmental
Protection Agency, Mail Code: 6102T, 1200 Pennsylvania Avenue, NW.,
Washington, DC 20460. Please include a total of two copies.
Hand Delivery: EPA Docket Center, 1301 Constitution
Avenue, NW., Room B108, Washington, DC. 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 on the NODA to Docket ID No.
OAR-2002-0056. The EPA's policy is that all comments received will be
included in the public docket(s) without change and may be made
available online at http://www.epa.gov/edocket, 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 EDOCKET,
regulations.gov, or e-mail. The EPA EDOCKET and the Federal
regulations.gov websites are ``anonymous access'' systems, 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 EDOCKET or 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.
Docket: All documents in the docket are listed in the EDOCKET index
at http://www.epa.gov/edocket. Although listed in the index, some
information is not publicly available, i.e., CBI or other information
whose disclosure is restricted by statute. Certain other material, such
as copyrighted material, is not placed on the Internet and will be
publicly available only in hard copy form. Publicly available docket
materials are available either electronically in EDOCKET or in hard
copy at the EPA Docket Center, EPA West, Room B102, 1301 Constitution
Avenue, 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: William Maxwell, U.S. EPA, Office of
Air Quality Planning and Standards, Emission Standards Division,
Combustion Group (C439-01), Research Triangle Park, North Carolina
27711, telephone number (919) 541-5430, e-mail at [email protected].
SUPPLEMENTARY INFORMATION:
Outline: The information presented in this NODA is organized as
follows:
I. Additional Information on Submitting Comments
A. How can I help EPA ensure that my comments are reviewed
quickly?
B. What should I consider as I prepare my comments for EPA?
1. Submitting CBI
2. Tips for Preparing Your Comments
II. Electric Utility Sector Modeling and Hg Speciation
A. What is the relevant background?
B. What are the specific issues relevant to electric utility
sector modeling?
1. Overview
2. What is IPM?
3. What specific comments did EPA receive on its IPM modeling in
response to the January 2004 proposal and the March 2004
supplemental proposal?
4. What are the areas of ongoing EPA research?
C. Issues of Hg Speciation
1. Overview
2. What specific comments on Hg speciation did EPA receive in
response to the January 2004 proposal and the March 2004
supplemental proposal?
3. What are the areas of ongoing EPA research?
III. EPA's Proposed Revised Benefits Assessment
A. What is the relevant background?
B. How is EPA estimating reductions in Hg exposure associated
with the CAMR?
C. Step 1 of EPA's Proposed Revised Benefits Methodology:
Analyzing Hg Emissions from Other Sources
1. Overview
2. What specific comments did EPA receive on Hg emissions from
other sources in response to the January 2004 proposal and the March
2004 supplemental proposal?
D. Step 2 of EPA's Proposed Revised Benefits Methodology:
Analyzing Air Dispersion Modeling Capabilities
1. Overview
2. What specific comments did EPA receive on air dispersion
modeling capabilities in response to the January 2004 proposal and
the March 2004 supplemental proposal?
E. Step 3 of EPA's Proposed Revised Benefits Methodology:
Modeling Ecosystem Dynamics
1. Overview
2. What specific comments did EPA receive on modeling ecosystem
dynamics in response to the January 2004 proposal and the March 2004
supplemental proposal?
F. Step 4 of EPA's Proposed Revised Benefits Methodology: Fish
Consumption and Human Exposure
1. Overview
2. What specific comments did EPA receive on fish consumption
patterns in response to the January 2004 proposal and the March 2004
supplemental proposal?
G. Step 5 of EPA's Proposed Revised Benefits Methodology: How
Will Reductions in Population-level Exposure Improve Public Health?
I. Additional Information on Submitting Comments
A. How Can I Help EPA Ensure That My Comments Are Reviewed Quickly?
To expedite review of your comments by Agency staff, you are
encouraged to send a separate copy of your comments, in addition to the
copy you submit to the official docket, to William Maxwell, U.S. EPA,
Office of Air Quality Planning and Standards, Emission Standards
Division, Mail Code C439-01, Research Triangle Park, North Carolina
27711, telephone (919) 541-5430, e-mail [email protected].
B. What Should I Consider as I Prepare My Comments for EPA?
1. Submitting CBI. Do not submit this information to EPA through
EDOCKET, regulations.gov, or e-mail. Clearly mark the part or all of
the information that you claim to be CBI. For CBI information in a disk
or CD ROM that you mail to EPA, mark the outside of the disk or CD ROM
as CBI and then identify electronically within the disk or CD ROM the
specific information that is claimed as CBI. In addition to one
complete version of the comment that includes information claimed as
CBI, a copy of the comment that does not contain the information
claimed as CBI must be submitted for inclusion in the public docket.
Information so marked will not be disclosed except in accordance with
procedures set forth in 40 CFR part 2.
2. Tips for Preparing Your Comments. When submitting comments,
remember to:
a. Identify the rulemaking by docket number and other identifying
information (subject heading, Federal Register date and page number).
b. Follow directions--The Agency may ask you to respond to specific
questions or organize comments by
[[Page 69866]]
referencing a Code of Federal Regulations (CFR) part or section number.
c. Explain why you agree or disagree; suggest alternatives and
substitute language for your requested changes.
d. Describe any assumptions and provide any technical information
and/or data that you used.
e. If you estimate potential costs or burdens, explain how you
arrived at your estimate in sufficient detail to allow for it to be
reproduced.
f. Provide specific examples to illustrate your concerns, and
suggest alternatives.
g. Explain your views as clearly as possible, avoiding the use of
profanity or personal threats.
h. Make sure to submit your comments by the comment period deadline
identified.
II. Electric Utility Sector Modeling and Hg Speciation
A. What Is the Relevant Background?
On January 30, 2004, EPA issued a proposed CAMR under the CAA
concerning power plants.\3\ That proposed rule presents two primary
approaches to regulating Hg and Ni from power plants. Those approaches
are (1) retaining the Agency's December 20, 2000, determination that
regulating power plants under CAA section 112 is ``appropriate and
necessary'' and issuing final emission standards under CAA section
112(d); and (2) revising our December 2000 ``appropriate and
necessary'' determination, removing power plants from the CAA section
112(c) list, and issuing final standards of performance for coal-fired
power plants using a ``cap-and-trade'' methodology.\4\
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\3\ 69 FR 4652, January 30, 2004.
\4\ The Agency also proposed standards of performance for oil-
fired power plants that emit Ni. Although the Agency received
several comments concerning its alternative proposals to regulate Ni
from oil-fired power plants under CAA section 111 and CAA section
112, those comments are not the subject of this NODA. This NODA
instead focuses only on issues related to Hg.
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In response to the January 2004 proposal and the March 2004
supplemental proposal, we received over 680,000 public comments,
including almost 5,000 unique comments. Among other things, the
comments addressed how the power sector could respond to different
levels of control on Hg emissions. In particular, we received comments
on EPA's IPM modeling results, including our modeling assumptions. We
also received modeling analyses conducted by different commenters, some
of which used models and/or assumptions different from EPA's. Based on
the importance of, and the level of interest in, these modeling
analyses, this NODA summarizes the modeling analyses performed by
commenters and solicits comment on the inputs and assumptions
underlying those analyses and other issues related to benefit-cost
analysis.
We also received comments concerning the speciation of Hg. As we
explained in the proposed rule, the degree to which emissions control
devices can remove Hg depends, in large part, on the amount of each
form (or species) of Hg present in the flue gas. The three relevant
species of Hg are elemental Hg (Hg\0\), ionic or oxidized Hg
(Hg+\2\), and particulate Hg (Hgp).\5\ The Hg in
the flue gas from a coal-fired utility unit consists of these three
forms of Hg. Because of the importance of the relationship between Hg
speciation and the level of Hg reduction achievable, we are seeking
additional information on Hg speciation from coal-fired power plants to
further inform our regulatory decision.
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\5\ 69 FR 4652, January 30, 2004.
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The comments concerning the impact of different levels of emissions
control on the power sector and the speciation of Hg relate to both of
the two proposed regulatory approaches described above. With respect to
the CAA section 112(d) regulatory approach, the comments are relevant
to whether EPA should adopt a CAA section 112(d) standard that is more
stringent than the floor (i.e., a beyond-the-floor standard) and at
what level such a standard should be set. In evaluating a beyond-the-
floor standard under CAA section 112(d), EPA must consider cost, nonair
quality health and environmental impacts, and energy impacts.\6\ With
respect to the CAA section 111 regulatory approach, the comments are
relevant to the level at which standards of performance should be set.
Similar to the beyond-the-floor analysis under CAA section 112(d), EPA
must consider cost, nonair quality health and environmental impacts,
and energy requirements in defining the best system of emission
reduction under CAA section 111.
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\6\ 42 U.S.C. 7412(d).
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We recognize that the public already has access to the comments
submitted on the January 2004 proposed rule and the March 2004
supplemental proposal. However, because of the large volume of comments
received on those proposals, we issue the NODA today to summarize and
solicit comment on the new data and information presented in the
comments that are relevant to benefit-cost analysis and to the
regulatory approaches under consideration.
The Agency intends to make a final decision on its pending utility
proposal by March 15, 2005. EPA is still considering the comments
submitted on the proposal and supplemental proposal and evaluating
which regulatory approach to pursue.
B. What Are the Specific Issues Relevant to Electric Utility Sector
Modeling?
1. Overview. This section of the NODA addresses how the power
sector is predicted to respond to different levels of emissions
control. As we explained in the proposed CAMR, in designing regulatory
programs for the electric power sector, it is important to consider
(forecast) ways the power sector could respond to such programs.
In the proposed CAMR, EPA provided a forecast of how the power
generation mix in the United States (U.S.) would respond to a
particular regulatory approach.\7\ In response to the proposed rule,
several commenters provided their own forecasts of power sector
response. In some cases, the regulatory scenarios modeled by commenters
were the same or similar to those modeled by EPA. In these cases, we
can better understand the importance of different input assumptions by
comparing and contrasting the modeling performed. In other cases, the
commenters modeled alternative approaches and provided information
about the tradeoffs in regulatory design. The submitted modeling
addresses regulatory alternatives that are both more and less stringent
than our proposal. In all cases, the models are designed to predict a
least-cost solution to meeting electricity demand, subject to the model
input assumptions and constraints imposed. These constraints can
include restrictions on the availability of specific control
technologies. EPA is currently performing an evaluation of the modeling
analyses submitted by commenters.
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\7\ 69 FR 4706, January 30, 2004.
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To aid in our decision-making process, we are seeking comment on
the different input assumptions and constraints and the different
modeled regulatory approaches as presented in the commenter's modeling
analyses described below. We also identify below our questions of
particular interest concerning the new data and information presented
in the comments.
2. What is IPM? EPA uses IPM, developed by ICF Consulting (ICF), to
assess how the electric power industry will respond to various
environmental policies affecting that industry. IPM is a dynamic linear
programming model that can be used to examine air pollution
[[Page 69867]]
control policies for Hg and other pollutants throughout the contiguous
U.S. for the entire power system. IPM finds the least-cost solution to
meeting electricity demand subject to environmental, transmission,
reserve margin, and other system operating constraints for any
specified region and time period. For a given control policy, IPM
provides an electricity generator with various compliance options,
including adding pollution controls, changing fuel type, and changing
dispatch considerations. In addition, IPM provides information on fuel
market interactions and impacts on the cost of electricity.
Through licensing agreements with ICF, IPM is used by both public
and private sector clients. EPA contracted with ICF to develop a
version of IPM that EPA uses for its own power sector modeling. EPA has
used IPM to model the nitrogen oxides (NOX) State
implementation plan (SIP) call, the Clear Skies legislative proposal,
the proposed Clean Air Interstate Rule (CAIR), and the proposed
CAMR.\8\ Documentation for how EPA has configured IPM for pollution
control analysis can be found at http://www.epa.gov/airmarkets/epa-ipm.
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\8\ 69 FR 4652, January 30, 2004.
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Since it began using IPM as a power sector modeling tool, EPA has
periodically reviewed and updated the assumptions and modeling
capability of IPM. These updates have included the addition to IPM of
the capability to model Hg emissions and Hg control costs. However, EPA
recognizes that its Hg-related assumptions are more uncertain than
sulfur dioxide (SO2)- and NOX-related assumptions
due to limited information on controlling Hg from the power sector.
This is because, although we have recent data on Hg emissions from the
power sector, and some data on how the Hg speciation profile influences
the ability to control Hg emissions, the electric power industry has
much less experience implementing Hg controls than it does
SO2 and NOX controls. Further, as described later
in this NODA, the full impact of the mix of the various Hg species
found in the flue gas on the level of control achievable continues to
be investigated.\9\
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\9\ 69 FR 12401, March 16, 2004.
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As discussed further below, some of the commenters submitted
analyses using IPM. EPA's power sector modeling of the proposed CAMR
CAA section 112(d) maximum achievable control technology (MACT)
alternative using IPM 2003 is available in the docket in a memorandum
titled ``Economic and Energy Impact Analysis for the Proposed Utility
MACT Rulemaking'' (OAR-2002-0056-0048). EPA's power sector modeling of
the proposed CAMR CAA section 111 trading rule can also be found in the
docket at OAR-2002-0056-0338 to -0344.
3. What specific comments did EPA receive on its IPM modeling in
response to the January 2004 proposal and the March 2004 supplemental
proposal? During the comment period, EPA received numerous comments
related to the regulatory approaches outlined in the January 2004
proposal and the March 2004 supplemental proposal. EPA received
specific comments on the power sector modeling results from the
following commenters: Center for Clean Air Policy (CCAP) (OAR-2002-
0056-3447); Cinergy (OAR-2002-0056-4317 and -4318); Clean Air Task
Force (CATF), Natural Resources Defense Council (NRDC), et al. (OAR-
2002-0056-3459 and -3460); Edison Electric Institute (EEI) (OAR-2002-
0056-2929, -4894, -4895, and -4896); and Electric Power Research
Institute (EPRI) (OAR-2002-0056-2578).
Two of these commenters submitted the results of power sector
modeling using a version of IPM and two commenters submitted analyses
using a similar linear programming model. The CCAP submitted analyses
of multi-pollutant control options for the power sector using a version
similar to IPM 2003 employing different assumptions about electricity
demand growth and natural gas prices. Cinergy submitted analyses
performed using a version of IPM operated by ICF that included
Cinergy's own unique modeling assumptions. The CATF submitted analyses
on behalf of several environmental groups using EPA's IPM 2003. EEI
submitted an analysis performed by Charles River Associates (CRA) using
the Electric Power Market Model (EPMM; a linear programing model
similar to IPM). The EPRI comments included the same EPMM analysis. The
salient details of the individual analyses are described below.
a. What were the results of CCAP's power sector modeling? CCAP
established a stakeholder policy dialogue on alternative designs of
multi-pollutant legislative programs designed to control emissions from
the power sector. Their analysis was performed using a version of IPM
similar to EPA's IPM 2003 with different assumptions about electricity
demand growth and natural gas prices. Some modeling was conducted using
EPA's IPM 2002 assumptions about demand growth and natural gas prices,
and some modeling analysis was conducted using the Energy Information
Administration (EIA) assumptions about demand growth and natural gas
prices.
CCAP sponsored a series of modeling runs to look at the costs and
benefits of incremental changes in Hg cap levels and timing. The
analysis was based on policy options similar to the Clear Skies
proposal, using the same SO2 and NOX caps and
first phase Hg cap of 26 tons. Among the options analyzed, CCAP
examined three scenarios that implemented incrementally more stringent
Hg requirements in Phase 2: 15-ton cap in 2018 (Clear Skies), 10-ton
cap in 2015, and 7.5-ton cap in 2015.
Although their comments included several other modeling runs, for
comparison purposes EPA has summarized in Table 1 below CCAP's model
runs assuming EIA AEO2003 gas and growth assumptions. EPA notes that
the term ``total installed capacity'' used in Table 1 includes all
currently installed controls and control retrofits needed to meet the
modeled policy. EPA also notes that CCAP's results for the Phase 2 cap
of 15 tons are taken from EPA's analyses of the Clear Skies Act. CCAP
recommended that EPA adopt a tighter Phase 2 cap for the proposed Hg
trading rule, concluding that incremental changes in the timing and
stringency of a Hg cap have, in CCAP's opinion, relatively modest cost
implications.
[[Page 69868]]
Table 1.--Summary of CCAP Power Sector Modeling
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Hg phase 2 cap of 15 tons Hg phase 2 cap of 10 tons Hg phase 2 cap of 7.5 tons
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2010 2020 2010 2020 2010 2020
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Hg emissions.................... 25 tons.................. 18 tons.................. 21 tons.................. 13 tons.................. 19 tons................. 11 tons.
Annual costs ($1999)............ $3.3 billion............. $6.7 billion............. $4.3 billion............. $6.8 billion............. $4.6 billion............ $7.1 billion.
Present value (2005-2025)....... $64.5 billion
$71.3 billion
$75.0 billion
Hg Marginal costs in 2020....... $62,190/lb
$75,190/lb
$88,060/lb
Total installed capacity:
FGD......................... 179 GW................... 228 GW................... 171 GW................... 223 GW................... 174 GW.................. 220 GW.
SCR......................... 173 GW................... 229 GW................... 173 GW................... 214 GW................... 173 GW.................. 213 GW.
ACI......................... 13 GW.................... 40 GW.................... 34 GW.................... 70 GW.................... 46 GW................... 84 GW.
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b. What were the results of Cinergy's power sector modeling?
Cinergy used IPM to analyze the economic and environmental impact of
potential CAIR and Hg policies. Cinergy used a version of IPM offered
by ICF to its private sector clients. In addition, Cinergy provided
their own modeling assumptions that differ from those used by EPA,
including higher electricity demand growth, higher natural gas prices,
different costs for subbituminous coal switching, higher costs for
pollution control retrofits, and a higher discount rate.
The scenarios modeled by Cinergy included a CAIR only scenario,
``CAIR plus Hg trading'' scenario, ``CAIR plus EPA MACT'' scenario, and
``CAIR plus stringent MACT'' scenario. The ``CAIR plus stringent MACT''
scenario has no subcategorization and a 0.88 pounds per trillion
British thermal units (lb/TBtu) rate for all affected units, starts in
2008, and assumes that ACI is not commercially available until 2010.
Results of the Cinergy analysis of Hg reduction scenarios are
summarized in Table 2 below. Present value costs are for a 20-year
period and assume a 7 percent discount rate. Although Cinergy's
modeling assumed the availability of ACI, Cinergy raised concerns about
the availability and performance of ACI in the 2008 to 2010 timeframe.
For the CAIR only scenario, Cinergy's analysis projects a Hg co-
benefit level in 2010 of 38 tons. For the ``CAIR plus Hg trading''
scenario, the Cinergy analysis projected Hg marginal costs from 2010 to
2020 to reach the safety valve price of $35,000/lb. Cinergy's model
also projected lower bituminous coal consumption, 25 percent higher
subbituminous coal consumption, and 10 percent higher lignite coal
consumption when compared to EPA's Hg trading results. For the ``CAIR
plus stringent MACT'' scenario, Cinergy modeling concluded that, due to
the lack of ACI controls, units had to switch to lower Hg coals,
install flue gas desulfurization/selective catalytic reduction (FGD/
SCR), or shut down in order to achieve compliance. In addition, Cinergy
concluded that an unrealistic number of FGD/SCR were installed by 2008
in order to meet the MACT limit (about 10 gigawatt (GW) of FGD and 30
GW of SCR). The Cinergy analysis projected that units burning
subbituminous and lignite coals would shut down for 2 years because no
technologies would exist until 2010 to comply with stringent MACT
emissions limits. Cinergy's analyses predicted that natural gas- and
oil-fired units would be operated to make up the generation short fall.
This resulted in significant increases in power prices and fuel prices
in the short term. Once ACI became available in the model in 2010,
units installed such controls and started operating again.
Table 2.--Summary of Cinergy Power Sector Modeling
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Hg trading plus CAIR Proposed CAMR MACT plus CAIR Stringent MACT plus CAIR
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2010 2020 2010 2020 2010 2020
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Hg emissions.................... 32 tons.................. 26 tons.................. 33 tons.................. 30 tons.................. 9 tons.................. 9 tons.
Present Value ($2000) for 20 $65 billion
year.
$64 billion
$130 billion
Total installed capacity:
FGD......................... 150 GW................... 200 GW................... 160 GW................... 180 GW................... 180 GW.................. 180 GW.
SCR......................... 150 GW................... 160 GW................... 140 GW................... 170 GW................... 165 GW.................. 175 GW.
ACI......................... 10 GW.................... 25 GW.................... 15 GW.................... 20 GW.................... 120 GW.................. 120 GW.
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* Note: No annual costs were provided by Cinergy in their comments.
c. What were the results of CATF's power sector modeling? CATF
modeled two MACT scenarios with the assistance of ICF using EPA's IPM
2003. The two scenarios modeled were: (1) EPA's CAMR MACT alternative
proposal in combination with EPA's CAIR proposal (``CAMR MACT plus
CAIR''), and (2) an ``Alternative Mercury Control Scenario.'' In their
comments, CATF states that their ``Alternate Mercury Control Scenario''
is consistent with EPA's proposed ``CAMR MACT'' approach of basing
subcategories on fuel rank; however, CATF notes that the emission rates
used by EPA in its modeling do not represent what they believe to be
MACT. The CATF states that their analysis is provided to ``demonstrate
that more stringent Hg emission rates are feasible and highly cost-
effective.''
The alternative emission rates CATF evaluated are standards
representing 90 percent Hg reduction (measured as a reduction from the
Hg content in the input coal) for bituminous-fired units,
[[Page 69869]]
1.5 lb/TBtu for subbituminous-fired units, and 4.5 lb/TBtu for lignite-
fired units. As stated in the CATF comments, the 90 percent level was
specified for bituminous-fired units because the version of IPM used by
CATF could not simulate Hg reductions any higher than 90 percent
through the use of retrofitted control technology. EPA notes, however,
that IPM can model reductions greater than 90 percent through fuel
switching, dispatch changes, or retirements.
A summary of the CATF analysis of the EPA proposed ``CAMR MACT plus
CAIR'' and ``Alternative Mercury Control Scenario'' plus CAIR is
provided in Table 3 below. EPA notes that the term ``total installed
capacity'' used in Table 3 below includes all currently installed
controls and control retrofits needed to meet modeled policy. EPA
further notes that EPA's Base Case 2003 projects about 115 GW of
scrubbers and 116 GW of SCR by 2010.
Table 3.--Summary of CATF Power Sector Modeling
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CAMR MACT plus CAIR Alternative Mercury Control Scenario plus CAIR
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2010 2020 2010 2020
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Hg emissions....................... 26 tons..................... 23 tons.................... 12 tons.................... 12 tons.
Annual costs ($1999)............... $5.7 billion................ $7.1 billion............... $8.4 billion............... $7.7 billion.
Total installed capacity:
FGD............................ 193 GW...................... 233 GW..................... 221 GW..................... 224 GW.
SCR............................ 145 GW...................... 177 GW..................... 172 GW..................... 174 GW.
ACI............................ 17 GW....................... 19 GW...................... 102 GW..................... 102 GW.
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* Note: No present value costs were provided by CATF in their comments.
CATF concluded that the ``Alternate Mercury Control Scenario''
results in shifts toward more bituminous coal use (in 2020, about 7
percent from Base Case 2003) and declines in subbituminous and lignite
coal use (in 2020, about 27 percent and 13 percent from Base Case 2003,
respectively). CATF projected a similar shift in reaction to EPA's
proposed ``MACT plus CAIR'' scenario (i.e., increase of about 5 percent
for bituminous, decreases of about 24 percent and 15 percent for
subbituminous and lignite, respectively). In addition, CATF concluded
that the ``Alternate Mercury Control Scenario'' reduces coal use in
2020 by less than 1 percent compared to EPA's proposed ``CAMR MACT plus
CAIR'' scenario, to a level that would be about 6 percent above current
(2001) electric power generation coal consumption.
d. What were the results of EEI's power sector modeling? EEI's
power sector modeling was performed using CRA's EPMM model. As noted
above, EPRI's comments included the same CRA EPMM modeling analysis as
EEI. Some of the EPMM modeling assumptions differ from those of EPA,
including higher natural gas prices, higher electric growth demand,
different Hg co-benefit assumptions for NOX and
SO2 controls, and different costs and performance for ACI.
The scenarios modeled by EEI include a CAIR-only scenario, ``CAIR plus
EPA MACT'' scenario, and three ``CAIR plus Hg trading'' scenarios. EEI
modeled two cases of the EPA-proposed Hg trading scenario with a 34-ton
first-phase cap in 2010 and a 15-ton second phase cap in 2018. (Note
that EPA did not propose a 34-ton first-phase cap but, rather, took
comment on the appropriate level of the Phase 1 cap.) One of EEI's
cases assumed a 2.5 percent annual improvement in variable operating
costs for ACI, and the other did not include this assumption. EEI also
modeled an alternative Hg trading scenario with a 24-ton cap in 2015
and a 15-ton cap in 2018, assuming 2.5 percent annual improvement in
variable operating costs for ACI. Under this alternative option, early
reduction credits can be earned and banked during the period 2010 to
2014 through early application of Hg control technologies (e.g., ACI).
To simulate early reduction credits, the EEI analysis set caps equal to
co-benefits during this period. The co-benefits were defined as the Hg
emissions from the comparable CAIR-only scenario, 39.9 tons in 2010 and
2011, and 38.5 tons for 2012 through 2014.
Results of the EEI analysis of Hg reduction scenarios are
summarized in Table 4 below. Present value costs in Table 4 are for
2004 to 2020 and assume an 8 percent discount rate, consistent with
EEI's analysis. For Hg trading scenarios, EPA notes that EEI projected
emissions of 15 tons in 2020 appear to be an artifact of the grouping
of the 2020 run year with the model end run year of 2040. EPA maintains
that, in a least-cost solution model like EPMM, the model would solve
for the cap in the final run year grouping. Therefore, Hg emissions
reported for trading scenarios in the table below are those projected
for 2019, because EPA believes they better represent emissions in 2020,
i.e., if 2020 had not been grouped with 2040. The Hg trading scenarios
have been modeled without a safety valve.
EEI's analysis also included information on projected technology
retrofits. EEI notes in their comments that these projections reflect
the quantities necessary to comply with the proposed rules and may not
reflect what is feasible to retrofit or what is commercially available.
EEI also noted in their comments, that although they modeled the
availability of ACI at 90 percent removal, the cost and effectiveness
of ACI control technology remains uncertain, especially on
subbituminous coal-fired units.
Table 4.--Summary of EEI Power Sector Modeling*
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Proposed CAMR MACT plus CAIR Hg trading plus CAIR Hg trading plus CAIR (improved ACI Alternative Hg trading plus CAIR
--------------------------------------------------------------------------------- costs) (improved ACI costs)
-------------------------------------------------------------------------------
2010 2020 2010 2020 2010 2020 2010 2020
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Hg emissions**................. 32 tons............ 30 tons........... 34 tons........... 24 tons........... 34 tons........... 24 tons........... 37 tons........... 23 tons.
Annual costs ($1999)........... $4.4 billion....... $6.8 billion...... $2.5 billion...... $8.1 billion...... $2.5 billion...... $8.0 billion...... $2.6 billion...... $7.7 billion.
[[Page 69870]]
Present value (2004-2020)...... $27.8 billion
$19.7 billion
$19.1 billion
$19.4 billion
Hg marginal costs in 2020...... Not applicable
$37,285/lb
$32,536/lb
$32,536/lb
Total installed capacity:
FGD........................ 153 GW............. 180 GW............ 128 GW............ 192 GW............ 128 GW............ 193 GW............ 129 GW............ 195 GW.
SCR........................ 134 GW............. 153 GW............ 120 GW............ 148 GW............ 121 GW............ 148 GW............ 121 GW............ 148 GW.
ACI........................ 67 GW.............. 67 GW............. 16 GW............. 107 GW............ 16 GW............. 112 GW............ 16 GW............. 112 GW.
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
* EPRI comments submitted the same modeling analysis.
** Emission results are presented for 2019.
4. What are the areas of ongoing EPA research? EPA is in the
process of evaluating the above comments and data and, as noted above,
has developed certain preliminary reactions to the comments. We are
seeking comment on certain aspects of the above modeling analyses. As
demonstrated by the above summaries of the comments, estimates of the
impact of Hg regulation on the power sector are sensitive to model
input assumptions. To increase the accuracy of EPA's power sector
modeling as related to forecasting the power sector's response to
environmental regulatory programs, we are seeking comment and/or
additional information to inform our regulatory decision.
Moreover, since the January 2004 proposal and the March 2004
supplemental proposal, we have become aware of new information on the
ability of sorbent injection technologies to remove Hg emissions from
coal-fired power plants (e.g., results of ACI testing over a period of
several months at Southern Company's Plant Gaston, brominated activated
carbon (B*PACTM) injection at Detroit Edison's St. Clair
Power Plant, etc.). To this end, the Agency is seeking updated
information on issues that may be relevant to assessing the assumptions
employed in our power sector modeling (e.g., removal efficiencies,
capital and operating and maintenance (O&M) costs, timeline for
commercialization, balance of plant issues, etc.). Specifically, we are
interested in obtaining information on:
a. In some of EEI's analyses, EEI assumed a 2.5 percent annual
improvement in variable operating costs for ACI. Is it appropriate for
an economic forecast to assume an improvement in costs over time (such
as through technology cost reductions or through future technology
innovation), and, if yes, what level of improvement in costs should be
assumed?
b. Due to model size considerations, limited knowledge on
achievable levels of Hg control, and limited knowledge on assessing the
full impact of the Hg speciation profile on control, IPM has limited Hg
control retrofit options. Currently, IPM assumes that Hg reductions are
achieved only through use of SCR and FGD or ACI (with or without fabric
filter). (EPA notes that Hg reductions in IPM can also be achieved
through fuel switching, dispatch changes, and retirements.) Should
other control options be considered in EPA's power sector modeling
(e.g., retrofit of fabric filters and electrostatic precipitators, pre-
combustion controls, and the optimization of SO2 or
NOX controls)?
c. To the extent commenters believe that control considerations
other than those noted in the proposal or in the preceding paragraphs
should be included in power sector modeling, EPA is seeking data on the
timeline for commercialization, cost, balance of plant issues, and
performance of such control options.
d. CATF and Cinergy both modeled more stringent MACT-type options.
However, CATF assumed that ACI would be available in 2005 for all coal
types, while Cinergy assumed that ACI would be available in 2010 for
all coal types for one MACT scenario modeled. (EPA notes that for
Cinergy's other modeled scenarios, including a MACT scenario, it
assumed ACI would be available in 2005.) The year of availability for
ACI is an assumption that appears to have made a large difference in
the projected impacts of a MACT-type option. (Note that in a January
2004 white paper, we projected that ACI technology would be available
for commercial application after 2010 and that removal levels in the 70
percent to 90 percent range could be achievable. This assumes the
funding and successful implementation of an aggressive, comprehensive
research and development program at both EPA and the U.S. Department of
Energy (DOE). Such applications represent only the initiation of a
potential national retrofit program, which would take a number of years
to fully implement. Since release of the white paper, we have received
numerous comments on technology and have additional test data. We are
currently evaluating this new information.) \10\ What assumptions for
ACI availability are most appropriate? Specifically, what date of
availability for ACI technology is appropriate to consider in a
modeling analysis, at what quantities, for what coal types, and why?
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\10\ See OAR-2002-0056-0043 and -0463.
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e. EEI estimated that ACI would be less expensive per pound of Hg
removed than EPA has estimated. In addition, Cinergy assumed higher
capital costs for ACI than EPA in its modeled scenarios. Are EPA's Hg
control technology cost assumptions reasonable? Although EPA has
information on the costs of ACI, EPA is seeking additional detailed
data addressing the validity of the costs assumed for ACI.
f. Analyses by commenters and EPA of Hg trading programs indicate
that variations in the first phase cap level and timing impact when the
final cap level will be achieved (i.e., the emissions reduction ``glide
path''). Although banking in the first phase impacts the timing of
achieving the second phase cap, it should not affect the cumulative Hg
emissions reductions ultimately achieved under the program. EPA is
seeking additional comment on the impact banking may have on the timing
of achieving the second phase cap.
g. EPA received comments estimating the co-benefits of Hg
reductions associated with implementation of the proposed CAIR (i.e.,
the level of Hg
[[Page 69871]]
reductions realized as a result of compliance with the proposed CAIR).
Cinergy estimates a co-benefit level in 2010 of 38 tons as compared to
current emissions of 48 tons. EEI estimates a co-benefit level in 2010
of 40 tons. Both groups modeled a 34-ton first phase cap. In light of
these modeling analyses, EPA is seeking additional comment on the
reasonableness of its current IPM assumptions co-benefit reductions.
Emission modification factors (EMF) are one component of the estimated
Hg co-benefits from the proposed CAIR. A comparison of co-benefit
assumptions used in EPA and other modeling is provided in Table 5. We
are also seeking comment on appropriate EMF.
Table 5.--Hg Removal Assumptions for Pollution Control Equipment
--------------------------------------------------------------------------------------------------------------------------------------------------------
EPA 2003 EMFs CRA 2004 EMFs EIA EIA AEO2004 EMFs
-----------------------------------------------------------------------------------------
Name for control Subbit Lignite Subbit Lignite Subbit Lignite
Bit EMF EMF EMF Bit EMF EMF EMF Bit EMF EMF EMF
--------------------------------------------------------------------------------------------------------------------------------------------------------
PC/CS-ESP..................................................... 0.64 0.97 1.00 0.65 0.80 0.90 0.64 0.97 1.00
PC/CS-ESP/FGD................................................. 0.34 0.84 0.56 0.40 0.65 0.65 0.34 0.73 0.58
PC/CS-ESP/FGD-Dry............................................. 0.64 0.65 1.00 0.50 0.85 0.90 0.64 0.65 1.00
PC/CS-ESP/SCR/FGD............................................. 0.10 0.34 0.56 0.15 0.65 0.65 0.10 0.73 0.58
PC/FF......................................................... 0.11 0.27 1.00 0.25 0.35 0.90 0.11 0.27 1.00
PC/FF/FGD..................................................... 0.10 0.27 1.00 0.15 0.25 0.60 0.05 0.27 0.64
PC/FF/FGD-Dry................................................. 0.05 0.75 1.00 0.15 0.75 0.90 0.05 0.75 1.00
PC/FF/SCR/FGD................................................. 0.10 0.15 0.56 0.10 0.25 0.60 0.10 0.27 0.64
PC/HS-ESP..................................................... 0.90 0.94 1.00 0.80 1.00 1.00 0.90 0.94 1.00
PC/HS-ESP/FGD................................................. 0.58 0.80 1.00 0.45 0.70 0.70 0.58 0.80 1.00
PC/HS-ESP/FGD-Dry............................................. 0.60 0.85 1.00 na na na 0.60 0.85 1.00
PC/HS-ESP/SCR/FGD............................................. 0.10 0.75 1.00 0.15 0.70 0.70 0.42 0.76 0.64
--------------------------------------------------------------------------------------------------------------------------------------------------------
Notes: PC: pulverized coal; CS-ESP: cold-side electrostatic precipitator; HS-ESP: hot-side electrostatic precipitator; FGD: flue gas desulfurization;
SCR: selective catalytic reduction; FF: fabric filter; EMF: emission modification factor (% reduction = 1--EMF) EPA 2003 EMFs used by CATF and CCAP
analyses; Charles River Associates (CRA) EMFs used in EEI analysis; AEO2004 EMF used in Energy Information Administration (EIA) modeling.
h. More recent test data than were available at proposal on
subbituminous-fired units equipped with SCR indicate that SCR does not
enhance the oxidation of Hg0 on such coals and, thus, does
not provide for additional capture in a wet scrubber.\11\ Based on
these test data, EPA is considering revising the EMF for subbituminous
coal-fired units equipped with SCR and wet FGD in modeling for the
final rule. For the EMF identified in Table 5 for such units, EPA
recommends the use of the EMF control combination before a SCR is added
(i.e., ascribe no additional control due to the addition of the SCR).
Thus, EPA is considering making the following three changes to the
subbituminous coal EMF used in IPM: for CS-ESP/SCR/FGD, use CS-ESP/FGD
(0.84); for FF/SCR/FGD, use FF/FGD (0.27); and for HS-ESP/SCR/FGD, use
HS-ESP/FGD (0.80). EPA is seeking comment on these proposed EMF
changes.
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\11\ See OAR-2002-0056-1268 and -1270.
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In addition, EPA notes that other recent test data (e.g., DOE- and
EPRI-sponsored testing on Hg controls) may be available that would
influence EMF used in EPA modeling. EPA is seeking comment on the
appropriateness of using other test data for EMF development and
requests that commenters submit any test data that may be relevant.
C. Issues of Hg Speciation
This section addresses the issue of Hg speciation. As explained
further below, we are seeking additional input on the species (or form)
of Hg emitted in the flue gas, the percentage of each species emitted
in the flue gas, and how those percentages in total (i.e., the
speciation profile) affect the analysis of how the power sector could
respond to different levels of emissions control.
1. Overview. To quantify the relative contribution of Hg emissions
from U.S. coal-fired power plants on total nationwide Hg deposition,
the EPA initiated an Information Collection Request (ICR) in 1999 under
the provisions of CAA section 114. During this data collection effort,
incoming coal shipments for all coal-fired power plants in the U.S.
were tested for Hg content (for calendar year 1999) and other selected
coal properties (e.g., ash, sulfur and chlorine content, etc.).
Additionally, during 1999, 81 power plants--chosen to be representative
of the entire U.S. power plant sector--were tested for stack emissions
of Hg using the Ontario-Hydro sampling method. The Ontario-Hydro method
provided EPA with speciated Hg emissions (i.e., Hg0,
Hg+2, and Hgp) for these tested units. Data from
these tests were then extrapolated to all domestic coal-fired power
plants and used to generate a national total Hg emissions estimate for
1999 (48 tons per year). These data were further used to provide a
national estimate of emissions of the three forms of Hg as follows:
Hg0--54 percent, Hg+2--43 percent, and
Hgp--3 percent. Plant-specific estimates based on these data
were used in the IPM modeling activities discussed elsewhere in this
notice. In general, eastern bituminous coals emitted the least amount
of Hg0 (the species most difficult to control); followed by
western subbituminous coals (e.g., Powder River Basin (PRB), etc.); and
the northern and southern lignite coals. To this end, the 1999 ICR data
collection effort provided EPA one of the most comprehensive databases
available to date regarding Hg emissions from coal-fired power plants.
In the proposed CAMR, EPA discussed the relevance and importance of
characterizing the species of Hg emitted in the flue gas and solicited
comment on that issue. EPA received significant public input as a
result. As we and commenters have recognized, the form (or species) of
Hg emitted in the flue gas affects the ability to control Hg emissions
\12\ and the form of Hg released from a stack affects the atmospheric
fate and transport of Hg. The species of Hg, therefore, is relevant to
assessing the costs associated with different levels of Hg emissions
control.
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\12\ 69 FR 4672, January 30, 2004.
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2. What specific comments on Hg speciation did EPA receive in
response to the January 2004 proposal and the March 2004 supplemental
proposal? A number of comments were provided on
[[Page 69872]]
the importance of speciated Hg emission information and potential
atmospheric transformations during the public comment period. Among
these are comments or attachments submitted by the following: EPRI
(OAR-2002-0056-2578); Hubbard Brook Research Foundation (HBRF) (OAR-
2002-0056-2038); Southern Company (OAR-2002-0056-2948); Subbituminous
Energy Coalition (SEC) (OAR-2002-0056-2379); and Utility Air Regulatory
Group (UARG) (OAR-2002-0056-2922 and -2928).
EPRI provided information (in Section A of their report) on plume-
simulating chamber studies that indicate transformation of Hg species
in the plume. This work was followed by studies to evaluate the
speciation changes in actual power plant plumes.
HBRF (in Section 3 of their report) provided comment on the
validity of using an average speciation profile for all coal-fired
power plants. SEC raised questions about the speciation profile for
units burning a mix of coals. Southern Company and UARG indicated that,
because the Hg speciation dictates the level of control that may be
achieved with existing control equipment, different Hg emission limits
must be established for the different coal ranks.
3. What are the areas of ongoing EPA research? EPA is evaluating
all of the comments on speciation that it received in response to the
proposed CAMR. To further aid in our review of these comments, to
supplement our existing 1999 ICR database, and to aid in our decision-
making process, EPA is seeking additional comment on the following
areas.
a. We have received numerous comments on subcategorization by coal
type and the speciation profiles resulting from the combustion of
various coal types. We are seeking additional specific data and
information on the speciation profiles of various types and blends of
fuels.
b. Commenters have questioned the appropriateness of using a
standard (or average) speciation profile in modeling analyses conducted
for all coal-fired power plants. The Agency is seeking comment on if/
when a standard (or average) speciation profile should be used for
either the CAA section 111 or CAA section 112 regulatory approach.
c. Is it currently feasible, or will it be feasible within the
compliance timeframes of the proposed rule, to accurately monitor a
source's Hg emissions by species?
III. EPA's Proposed Revised Benefits Assessment
A. What Is the Relevant Background?
Consistent with EO 12866, EPA included a benefits assessment in the
proposed CAMR. EPA received comments on that assessment. Based on those
comments and in furtherance of our obligations under EO 12866, we have
preliminarily revised our proposed approach to analyzing the benefits
associated with Hg emission reductions from power plants. We explain
below our proposed revised benefits methodology. We also identify below
comments received on the proposed CAMR that provide analyses or
information relevant to our proposed revised benefits approach. We
further identify those commenters that presented approaches that differ
from our revised approach, as described below. We seek comment on our
proposed revised benefits methodology and on the strengths and
weaknesses of the analytical approaches presented in the comments to
the extent they relate to our proposed revised benefits methodology.
Although this section of the NODA addresses the benefits analysis
that we must prepare for purposes of EO 12866, we recognize that the
costs and benefits of reducing emissions are often inter-related. Thus,
to the extent that we receive any comments or other information in the
process of completing the benefits assessment for purposes of EO 12866
and to the extent that such information bears on the statutory factors
relevant to setting either a beyond-the-floor standard for Hg under CAA
section 112(d) or a standard of performance for Hg under CAA section
111, we intend to evaluate and consider that information as we make a
final decision as to which regulatory approach to pursue.
B. How Is EPA Estimating Reductions in Hg Exposure Associated With the
CAMR?
EPA's proposed revised benefits analysis attempts to estimate the
extent to which adverse human health effects will be reduced as a
result of reducing Hg emissions from coal-fired power plants.
Translating estimates of reductions in Hg emissions from coal-fired
power plants to health outcomes in humans is a function of a number of
complex chemical, physical, and biological processes, as well as a wide
variety of human behaviors and responses.
The relevant events and processes include the following:
The magnitude and nature of current and forecasted Hg
emissions from coal-fired power plants, as well as the magnitude and
species of current Hg emissions from other sources, both domestic and
international.
The physical transport of vapor and particle-phase Hg
emissions in the air, as well as the chemical transformations that
occur to Hg as it reacts with other chemical species in the atmosphere.
The deposition of inorganic Hg onto terrestrial and
aquatic surfaces, and the transport of Hg from terrestrial systems to
surface water bodies.
The biological, chemical, and physical processes that
control the rate of methylmercury (MeHg) production in surface waters
and aquatic sediments and the bioavailability of Hg to organisms.
The composition and complexity of aquatic food webs and
species-specific factors such as diet composition, chemical
assimilation efficiencies, and metabolism that affect the
bioaccumulation of MeHg in fish.
The extent to which specific water bodies are used for a
variety of fishing activities, either by individuals or commercially.
Different human fish consumption behaviors, including for
specific subpopulations.
The human response to MeHg exposure.
EPA's proposed revised benefits methodology attempts to
characterize, either directly or indirectly, each of the above events
and processes. EPA specifically is seeking to estimate the reduction in
exposure to MeHg associated with reducing Hg emissions from coal-fired
power plants. We are seeking comment on our proposed revised benefits
approach, as described below. As noted above, we are also seeking
comment on the comments that we received that are relevant to our
proposed revised benefits methodology.
The following sections describe each of the steps of our proposed
revised benefits methodology. Those steps can be categorized broadly as
follows:
Quantify Hg emissions that are projected from U.S. coal-
fired power plants under the Base Case and CAMR and then quantify Hg
emissions that result from sources other than U.S. coal-fired power
plants. The power sector modeling described above and in more detail at
http://www.epa.gov/airmarkets/epa-ipm/ will assist in the
quantification of Hg from U.S. coal-fired power plants.
Model the atmospheric dispersion, atmospheric speciation,
and deposition of Hg.
[[Page 69873]]
Model the link between changes in Hg deposition and
changes in the MeHg concentration in fish.
Assess the types and amounts of fish consumed by U.S.
consumers and, from that, assess the resulting MeHg exposure.
Assess how reductions in human exposure to MeHg affects
human health.
C. Step 1 of EPA's Proposed Revised Benefits Methodology: Analyzing Hg
Emissions From Other Sources
1. Overview. As stated in the proposed CAMR, Hg exposure is both a
domestic and a global issue. From a domestic perspective, power plants
are one source of Hg air emissions, but there are other domestic
sources of man-made Hg. Mercury also enters the atmosphere from a
variety of natural processes, including, for example, volcanic
eruptions, groundwater seepage, and evaporation from the oceans.
EPA currently does not have an inventory of natural or re-emitted
sources suitable for modeling purposes. EPA does, however, have
inventories concerning man-made domestic and international sources of
Hg. These inventories have been used over the past decade in air
quality and air deposition modeling.13 14 They are important
because the first step of EPA's proposed revised benefits methodology
is to quantify Hg emissions that result from sources other than U.S.
coal-fired power plants. In particular, the inventories enable us to
establish upwind and downwind boundary conditions to apportion exposure
to non-natural domestic and international sources of Hg emissions.
---------------------------------------------------------------------------
\13\ Pacyna, J.M., E.G. Pacyna, F. Steenhuisen, S. Wilson. 2003.
Mapping 1995 Global Anthropogenic Emissions of Mercury. Atmosph.
Env., 37, p. 109-117.
\14\ Seigneur, C., K. Vijayaraghavan, K. Loman, P.
Karamchandani, C. Scott. 2004. Global Source Attribution for Mercury
Deposition in the United States. Environ. Sci. Technol., 38, p. 555-
569.
---------------------------------------------------------------------------
The inventory sets that EPA currently is considering using include
an update/modification to the 1999 National Emissions Inventory (NEI)
for all U.S. anthropogenic sources for criteria pollutants and for all
U.S. anthropogenic non-power plant sources for Hg emissions, the 1995
Canadian criteria pollutant inventory for Canadian anthropogenic
sources, and the 2000 Hg inventory for Canadian anthropogenic
sources.\15\ EPA is also planning on using GEOS-CHEM for modeling
boundary conditions representing the global background.\16\
---------------------------------------------------------------------------
\15\ The update of the 1999 NEI (1) updates emissions of
criteria pollutants to 2001, (2) removes fugitive dust sources of Hg
in the few States where the original 1999 NEI includes them, and (3)
replaces the 1999 NEI estimates of 1999 Hg emissions from medical
waste incinerators with more recent data on 2002 emissions. The
original 1999 NEI is posted at http://www.epa.gov/ttn/chief/net/1999inventory.html. The 2001 criteria pollutant inventory for U.S.
sources is available in EPA Docket ID No. OAR-2003-0053, and is the
same as made available in the Notice of Data Availability for the
Clean Air Interstate Rule (69 FR 47828, August 6, 2004). The
updated/modified 1999 U.S. Hg inventory and the Canadian inventory
for all pollutants are posted at http://www.epa.gov/ttn/chief/emch/invent/index.html.
\16\ See http://www-as.harvard.edu/chemistry/trop/geos/.
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EPA is also aware of research conducted by EPA and others (e.g., at
Cheeka Peak, WA; Steubenville, OH; Mauna Loa, HI; Mt. Bachelor, OR; and
Okinawa).\17\ That research, for example, provides important
information about Hg fate and transport and relative domestic and
international source contributions. The research also provides
speciated high altitude atmospheric measurements of Hg. These
measurements may improve our understanding of the atmospheric reactions
that alter the chemical species of Hg in the atmosphere and that
ultimately impact fate and transport of emissions originating in Asian
countries and other international sources. This research is, therefore,
directly relevant to the first step of our preliminary proposed revised
benefits methodology, as it affects our ability to estimate the U.S.
power plant contribution to total Hg deposition within the U.S. EPA is
seeking comment on this step of its proposed revised benefits
methodology.
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\17\ See http://oaspub.epa.gov/eims/eimsapi.dispdetail?deid=56181.
---------------------------------------------------------------------------
2. What specific comments did EPA receive on Hg emissions from
other sources in response to the January 2004 proposal and the March
2004 supplemental proposal? EPA received a number of public comments
that are relevant to the issue of assessing Hg emissions from sources
other than U.S. coal-fired power plants, including comments from the
Center for Energy and Economic Development (CEED) (OAR-2002-0056-2256);
EPRI (OAR-2002-0056-2578); HBRF (OAR-2002-0056-2038); National Mining
Association (OAR-2002-0056-2434); TXU Energy (OAR-2002-0056-1831); and
UARG (OAR-2002-0056-2922). Some of these comments employed different
approaches for simulating boundary conditions for apportioning Hg
exposure from domestic and international sources, and we are interested
in obtaining public input on these alternative approaches and analyses.
D. Step 2 of EPA's Proposed Revised Benefits Methodology: Analyzing Air
Dispersion Modeling Capabilities
1. Overview. The second step of our proposed revised benefits
methodology requires modeling the atmospheric dispersion, atmospheric
speciation, and deposition of Hg. This is a critical step in our
analysis because to evaluate the benefits of reducing Hg emissions from
coal-fired power plants, we need to understand how Hg moves through the
atmosphere and how it is ultimately deposited.
Over the past decade, EPA has used a variety of analytical and
numerical simulation tools to project the atmospheric transport,
chemistry, and deposition of both criteria (e.g., ozone, fine
particles, etc.) and toxic (e.g., Hg) air pollutants. These models
range in complexity from simple, one-layer Gaussian dispersion models
(e.g., Industrial Source Complex (ISC3) model \18\) to more complex,
multi-layer Lagrangian puff-type trajectory models (e.g., Hybrid Single
Particle Lagrangian Integrated Trajectory (HYSPLIT) model\19\), and
finally to complex three-dimensional (3-D) Eulerian grid models (e.g.,
Community Multiscale Air Quality (CMAQ) model 20 21 22
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\18\ See http://www.epa.gov/scram001/tt22.htm#isc; http://www.epa.gov/scram001/userg/regmod/isc3v2.pdf; and http://www.epa.gov/scram001/7thconf/iscprime/useguide.pdf.
\19\ See http://www.arl.noaa.gov/ready/hysplit4.html.
\20\ Amar, P., R. Bornstein, H. Feldman, H. Jeffries, D. Steyn,
R. Yamartino, Y. Zhang. 2004. Review of CMAQ Model, December 17-18,
2003. See http://hill.nccr.epa.gov/air/interstateairquality/pdfs/PeerReview_of_CMAQ.pdf.
\21\ Community Multiscale Air Quality (CMAQ) Model
Documentation. See http://hill.nccr.epa.gov/air/interstateairquality/pdfs/CMAQ_Documentation.pdf.
\22\ Byun, D.W., N. Moon, D. Jacob, R. Park. Linking CMAQ with
GEOS-CHEM. See http://hill.nccr.epa.gov/air/interstateairquality/pdfs/GEOSCHEMforCMAQ_Description.pdf.
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EPA and others have been using a suite of complex numerical models
to assess the transport and fate of Hg emissions in the local,
regional, and global atmosphere. In the Utility Report to Congress, EPA
relied heavily on the ISC3 dispersion model to assess near-field Hg
deposition effects.\23\ The HYSPLIT model has also been used
extensively in the Great Lakes and Chesapeake Bay watersheds to analyze
source-receptor relationships for Hg deposition in these areas.\24\ The
[[Page 69874]]
Regional Modeling System for Aerosols and Deposition (REMSAD),\25\ a 3-
D Eulerian grid model, has been used in recent years for several State-
based total maximum daily load (TMDL) assessments for Hg deposition to
local watersheds.\26\ In addition, REMSAD was used to assess the
depositional changes associated with the implementation of the Clear
Skies Act of 2003.\27\
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\23\ U.S. EPA. February 1998. op. cit. pp. ES-16, ES-20, and 7-
28.
\24\ Cohen, M., R. Artz, R. Draxler, P. Miller, L. Poissant, D.
Niemi, D. Ratte, M. Deslauriers, R. Duval, R. Laurin, J. Slotnick,
J. Neetesheim, J. McDonald. 2004. Modeling the Atmospheric Transport
and Deposition of Mercury to the Great Lakes. Environ. Res., 95, p.
247-265.
\25\ See http://remsad.saintl.com/.
\26\ ICF Consulting. August 5, 2004. EPA Region 6--REMSAD Air
Deposition Modeling in Support of TMDL Development for Southern
Louisiana. Final Report. Prepared for EPA Region 6.
\27\ See http://epa.gov/clearskies/air_quality_tech.html.
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More recently, EPA and EPRI have applied 3-D Eulerian modeling
platforms to assess both domestic and global Hg deposition,
respectively. EPA has been evaluating the atmospheric transport,
transformation, and deposition of Hg using the CMAQ model over four 1-
month periods (two in 1995 and two in 2001) and over the entire year of
2001.\28\ CMAQ uses a ``one-atmosphere'' approach and addresses the
complex physical and chemical interactions known to occur among
multiple pollutants in the free atmosphere. The spatial resolution
(i.e., the ability to observe concentration or depositional gradients/
differences) of the gridded output information from CMAQ is generally
considered to be either 36 kilometers (km), 12 km, or 4 km; however, to
date, CMAQ results have only been developed for Hg modeling at the 36
km resolution. In simulating the transport, transformation, and
deposition of pollutants, CMAQ resolves 14 vertical layers in the
atmosphere, and employs finer-scale resolution near the surface to
simulate deposition to both terrestrial and aquatic ecosystems. CMAQ
transport is defined using a higher-order meteorological model,
commonly the Fifth-Generation Pennsylvania State University/National
Center for Atmospheric Research mesoscale model (MMM5) \29\ (current
modeling analyses are planning to use calendar year 2001 meteorological
data).
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\28\ Bullock, O., K. Brehme. 2002. Atmospheric Mercury
Simulation Using the CMAQ Model: Formulation Description and
Analysis of Wet Deposition Results. Atmosph. Environ., 36, p. 2135-
2146.
\29\ See http://www.mmm.ucar.edu/mm5/mm5-home.html.
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Currently, EPA is planning to use REMSAD and CMAQ for modeling the
atmospheric dispersion, speciation, and deposition of Hg. EPA is
specifically planning to use CMAQ version 4.4 with Hg with a horizontal
resolution of 36 km and 14 vertical layers and REMSAD version 7.13 also
with a horizontal resolution of 36 km and 14 vertical layers. As
described above, EPA is planning to use the GEOS-CHEM global model for
boundary conditions input to both REMSAD and CMAQ. EPA is seeking
comment on its proposed use of REMSAD and CMAQ to evaluate how Hg moves
through the atmosphere and how it will ultimately be deposited.
An important aspect of the second step of our proposed revised
benefits methodology is the evaluation of the REMSAD and CMAQ modeling.
In evaluating modeling, we seek to compare the simulated results with
ambient monitoring information to assess the quality of the modeled
simulations. The Mercury Deposition Network (MDN) provides the only
source of routinely available empirical domestic Hg deposition
information. MDN is a collaborative network involving several
organizations (e.g., United States Geological Survey (USGS), National
Oceanic and Atmospheric Administration, EPA) and is part of the
National Atmospheric Deposition Program (NADP) network of sites across
the U.S.\30\ As of spring 2003, the MDN contained approximately 90
sites across the U.S. and Canada, which provide measurements of wet
deposition of total Hg, integrated over weekly intervals.
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\30\ See http://nadp.sws.uiuc.edu/mdn/.
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We recognize the need to complement the MDN wet deposition
measurements with dry deposition measurements because it is not clear
how significant dry Hg deposition is to total ecosystem deposition.
Currently, there is no recognized field method for measuring dry
deposition. State-of-the-art atmospheric models indicate that the rate
of dry deposition of Hg can be of a similar order of magnitude as wet
deposition. Although the current extent of the MDN is relatively
limited--as compared to the extensive networks for ozone and fine
particles--EPA believes that the MDN data are the best available to
evaluate the predictive capabilities of regional- and national-scale
models. The MDN was not developed to monitor deposition near large
sources and is of limited use for evaluating near-field deposition from
models. We are seeking comment on how to use the MDN or related
information in evaluating the numerical modeling analyses discussed
above.
2. What specific comments did EPA receive on air dispersion
modeling capabilities in response to the January 2004 proposal and the
March 2004 supplemental proposal? We received a number of public
comments on the use of analytical and numerical models for assessing
the impacts of the proposed regulatory programs on Hg deposition
patterns. Among these are comments or attachments submitted by the
following: CEED (OAR-2002-0056-2256); CATF, NRDC, et al. (OAR-2002-
0056-3460); EPRI (OAR-2002-0056-2578); and UARG (OAR-2002-0056-2922).
Some of these commenters suggested alternative approaches to assessing
the atmospheric transport and deposition of Hg, and we seek comment on
those approaches.
E. Step 3 of EPA's Proposed Revised Benefits Methodology: Modeling
Ecosystem Dynamics
1. Overview. In the above steps of our proposed revised benefits
methodology, we seek to quantify changes in Hg deposition associated
with Hg reductions from U.S. coal-fired power plants. The third step
involves modeling affected ecosystems. As we explained in the proposed
CAMR, the main route of human exposure to MeHg is through consumption
of fish containing elevated levels of MeHg. Accordingly, to estimate
the changes in human exposure to MeHg that may result from reductions
in Hg emissions from U.S. coal-fired power plants, we must first
quantify how changes in Hg deposition from U.S. coal-fired power plants
(forecasted using the models described above) translate into changes in
MeHg concentrations in fish. Quantifying the linkage between different
levels of Hg deposition and fish tissue MeHg concentration is the third
step of our proposed revised benefits methodology.
To effectively estimate fish MeHg concentrations in a given
ecosystem, it is important to understand that the behavior of Hg in
aquatic ecosystems is a complex function of the chemistry, biology, and
physical dynamics of different ecosystems. The majority (95 to 97
percent) of the Hg that enters lakes, rivers, and estuaries from direct
atmospheric deposition is in the inorganic form.\31\ Microbes convert a
small fraction of the pool of inorganic Hg in the water and sediments
of these ecosystems into the organic form of Hg (MeHg). MeHg both
bioconcentrates and biomagnifies. In the environment this process is
referred to as bioaccumulation. MeHg is the only form of Hg that
biomagnifies in organisms.\32\
[[Page 69875]]
Ecosystem-specific factors that affect both the bioavailability of
inorganic Hg to methylating microbes (e.g., sulfide, dissolved organic
carbon) 33 34 and the activity of the microbes themselves
(e.g., temperature, organic carbon, redox status) \35\ determine the
rate of MeHg production and subsequent accumulation in fish. The extent
of MeHg bioaccumulation is also affected by the number of trophic
levels in the food web (e.g., piscivorus fish populations) because MeHg
biomagnifies as large piscivorus fish eat smaller organisms. These and
other factors can result in considerable variability in fish MeHg
levels among ecosystems at the regional and local scale.
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\31\ Lin, C-J., S.O. Pehkonen. 1999. The Chemistry of
Atmospheric Mercury: A Review. Atmospheric Environment, 33, p. 2067-
2079.
\32\ Bloom, N.S. 1992. On the chemical form of mercury in edible
fish and marine invertebrate tissue. Canadian Journal of Fisheries
and Aquatic Sciences, 49, p. 1010-1017.
\33\ Benoit, J., C.C. Gilmour, R.P. Mason, A. Heyes. 1999.
Sulfide controls mercury speciation and bioavailability to
methylating bacteria in sediment pore waters. Environ. Sci. Tech.,
33(6), p. 951-957.
\34\ Benoit, J.M., R.P. Mason, C.C. Gilmour, G.R. Aiken. 2001.
Constants for mercury binding by dissolved organic matter isolates
in the Florida Everglades. Goechim. Cosmochim. Acta, 65, p. 4445-
4451.
\35\ Hammerschmidt, C.R. and W.F. Fitzgerald. 2004. Geochemical
controls on the production and distribution of mercury in near-shore
marine sediments. Environ. Sci. Tech., 38(5), p. 1480-1486.
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To analyze the link between Hg deposition and MeHg concentrations
in fish in aquatic ecosystems across the U.S., EPA currently is
considering using EPA's Office of Water's Mercury Maps (MMaps).\36\
MMaps, which has been peer reviewed by EPA scientists and is currently
undergoing external peer review, provides a quantitative spatial link
between air deposition of Hg and MeHg in fish tissue. The external peer
review materials will be placed in the docket as soon as they are
available. The MMaps model suggests that changes in steady-state
concentrations of MeHg in fish will be proportional to changes in Hg
inputs from atmospheric deposition if air deposition is the only
significant source of Hg to a water body; and if the physical,
chemical, and biological characteristics of the ecosystem remain
constant over time. This model is best applied to ecosystems where
atmospheric deposition is the principal source of Hg to a water body
and assumes that the physical, chemical, and biological characteristics
of the ecosystem remain constant over time. EPA recognizes that
concentrations of MeHg in fish are not expected to be at steady state.
We also recognize that the requirement that all other conditions remain
constant over time inherent in the MMaps methodology is not likely to
be met. We further recognize that many water bodies, particularly in
areas of historic gold and Hg mining in western States, contain
significant nonair sources of Hg. Finally, we recognize that MMaps does
not provide for a calculation of the time lag between a reduction in Hg
deposition and a reduction in the MeHg concentrations in fish.
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\36\ Description of EPA's Mercury Maps model--http://www.epa.gov/waterscience/maps/ and September 2001 Mercury Maps Peer
Reviewed Final Report--http://www.epa.gov/waterscience/maps/report.pdf.
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Despite these limitations of this model, EPA is unaware of any
other tool for performing a national-scale assessment of the change in
fish MeHg concentrations resulting from reductions in atmospheric
deposition of Hg. As with all other aspects of our proposed revised
benefits methodology, we seek comment on the use of the steady-state
linear relationship between air deposition and MeHg concentrations in
fish (i.e., MMaps) and how the results of the application of this
relationship should be interpreted to account for the inherent
limitations described above.
To supplement the MMaps methodology, EPA is currently pursuing a
number of case studies examining Hg deposition and bioaccumulation of
MeHg in fish tissue. Dynamic ecosystem scale models are being used to
estimate ecosystem response times following reductions in atmospheric
Hg emissions, and to explore the uncertainty around the proportional
relationship used by the MMaps model. In this project, EPA is
considering modeling eight case studies spanning a range of ecosystem
types and characteristics in the Eastern and Midwestern U.S. Dynamic
watershed, water body, and aquatic bioaccumulation models will be
linked and applied to selected ecosystems, and sensitivity analyses
will be run to provide a context for estimating the range in the
magnitude and timing of changes in fish MeHg concentrations in response
to declines in Hg deposition that expected as the result of regulation
of power plants. More information on the models EPA is considering
using in the case studies (WASP, GBMM, SERAFM, EFDC, WhAEM2000, BASS,
E-MCM) can be found on the Council for Regulatory Environmental
Modeling (CREM) Models Knowledge Base (www.epa.gov/crem) and the Web
site for the Ecosystem Research Division of the Office of Research and
Development (ORD) (http://www.epa.gov/athens/).
In pursuing these case studies, EPA is seeking information on the
strengths and weaknesses of different approaches for modeling the
anticipated response of fish tissue MeHg concentrations to declines in
deposition for a national-scale benefits methodology. The case studies
will help determine the potential magnitude of response of the MeHg
concentration in fish in marine and freshwater systems if atmospheric
deposition from power plants are reduced, and what the expected time
lag will be before a response is observed in fish. To complement these
case studies, EPA is interested in both empirical information collected
from ecosystems across the U.S. or modeled scenarios that show the
temporal dynamics of Hg in different ecosystems.
The case studies will also help determine the effects of ecosystem
properties other than total Hg loading on accumulation in organisms and
suggestions for how such information should be incorporated into the
exposure analysis. To complement these case studies, EPA is interested
in both empirical information collected from ecosystems across the U.S.
or modeled scenarios that show the effects of ecosystem properties
other than total Hg loading on accumulation in organisms in different
ecosystems and, specifically, on new knowledge related to factors
affecting methylation and demethylation in a range of aquatic ecosystem
types.
Using the best-available scientific understanding of key processes,
these case studies will provide estimates of average rates and a
distribution of Hg methylation rates and MeHg bioaccumulation factors
(BAF) in different aquatic systems (freshwater and marine) across the
U.S. for use in modeling. EPA seeks comment on data and/or analytical
tools that can be used to forecast methylation rates and
bioaccumulation rates in aquatic ecosystems.
These case studies should provide detailed information on time lag,
important ecosystem properties other than deposition rates, Hg
methylation rates, and Hg BAF that can be used to inform how the
results of a national-scale MMaps application should be interpreted. We
are seeking information on the strengths and weaknesses of applying
MMaps to modeling the anticipated response of fish tissue MeHg
concentrations to declines in Hg deposition for a national-scale
benefits methodology. Additionally, EPA intends to document these case
studies in the electronic docket for the CAMR and to make this
information available to the public on the ORD's website as soon as
possible.
There are two final issues on which we are seeking comment that are
relevant to the third step in our proposed revised benefits
methodology. First, MMaps is designed to simulate natural freshwater
systems. We currently do not have an appropriate
[[Page 69876]]
method for assessing how a change in the deposition of Hg relates to a
change in the concentration of MeHg in fish tissue in fish found in
marine environments and/or farm-raised species. We recognize, however,
that marine and farm-raised species comprise a large proportion of the
fish consumed by the U.S. population and, likely account for a
significant fraction of the overall exposure. We are aware that EPRI
has submitted an analysis that assumes the changes in Hg deposition
resulting from regulation of emissions from coal-fired power plants
will have an effect on MeHg concentrations in estuarine and marine
species (salt-water species) proportional to the reduction in global
emissions.\37\ We are evaluating EPRI's proposed approach, but are also
seeking comment on other potential approaches for analyzing effects in
salt-water marine fish populations.
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\37\ See OAR-2002-0056-2578, -2589, and -2593.
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Second, as noted above, MMaps does not account for the time lag
that exists between reducing Hg deposition and reducing MeHg
concentrations in fish. MMaps instead assumes that a change in Hg
deposition immediately translates into a change in MeHg fish tissue
concentration. We are evaluating other tools that will enable us to
assess this time lag issue. In particular, we are aware of the Mercury
Experiment To Assess Atmospheric Loading In Canada and the U.S.
(METAALICUS) study, which was cited in a number of comments received by
EPA on the proposed CAMR. In METAALICUS, newly deposited Hg appeared to
be more available to bacteria to convert to MeHg than Hg that was in
the system for longer periods of time (i.e., historically deposited
Hg).\38\ These results suggest that lakes receiving the bulk of their
Hg directly from deposition to the lake surface would see fish MeHg
concentrations respond more rapidly to changes in atmospheric Hg
deposition than lakes receiving most of their Hg from terrestrial
runoff. These data also imply that systems with a greater surface-area-
to-watershed-area ratio that receive most of their inputs directly from
the atmosphere may respond more rapidly to changes in emissions and
deposition of Hg than those receiving significant inputs of Hg from the
catchment area. We emphasize that the METAALICUS experiment is ongoing,
and conclusions are still being refined. We do not know whether the
METAALICUS results, or ones similar, would be found in different
ecosystems. We are especially interested in information that can be
used to extend or extrapolate the results of the METAALICUS experiment
to other freshwater systems, and information on Hg cycling and
bioavailability in coastal and marine ecosystems.
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\38\ H. Hintelmann, R. Harris, A. Heyes, J.P. Hurley, C.A.
Kelly, D.P. Krabbenhoft, S. Lindberg, J.W.M. Rudd, K.J. Scott, V.S.
St. Louis. 2002. Reactivity and mobility of new and old mercury
deposition in a boreal forest ecosystem during the first year of the
METAALICUS study. Environ. Sci. Tech., 36, p. 5034-5040.
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2. What specific comments did EPA receive on modeling ecosystem
dynamics in response to the January 2004 proposal and the March 2004
supplemental proposal? EPA received several comments addressing
existing MeHg accumulation in fish and anticipated MeHg fish
concentrations associated with reductions in Hg emissions from coal-
fired power plants. Several groups submitted independent analyses of
the changes in fish MeHg concentrations expected as the result of
changes in Hg deposition. Among these are comments or attachments
submitted by the following: Bad River Band of Lake Superior Tribe of
Chippewa Indians (OAR-2002-0056-2118); Environmental Defense (OAR-2002-
0056-2878); EPRI (OAR-2002-0056-2578, -2589, and -2593); HBRF (OAR-
2002-0056-2038); Northeast States for Coordinated Air Use Management
(NESCAUM) (OAR-2002-0056-2887 and -2890); and TXU Energy (OAR-2002-
0056-1831). We are seeking comment on the analyses provided by the
commenters.
F. Step 4 of EPA's Proposed Revised Benefits Methodology: Fish
Consumption and Human Exposure
1. Overview. Step 4 in EPA's proposed revised benefits methodology
addresses the relationship between reductions in MeHg concentrations in
fish tissue and reductions in human exposure to MeHg. Fish obtained
through commercial sources or noncommercial fishing activities come
from both saltwater environments (including estuaries, bays, and the
open ocean), and freshwater rivers, streams, lakes, and ponds.
Consumption of fish is the primary pathway for human exposure to
MeHg. The fourth step in our methodology requires both an assessment of
MeHg concentrations in freshwater and saltwater fish and an assessment
of human consumption patterns of such fish. In this regard, we have
been evaluating several databases for estimating MeHg concentrations in
fish and consumption rates of such fish.
EPA's ongoing freshwater fish study, among other things,
incorporates information from EPA's National Listing of Fish Advisories
(NLFA), which contains approximately 80,000 samples of MeHg in fish
tissue from both freshwater and saltwater species.\39\ These data are
voluntarily submitted by State agencies to the EPA and provide
extensive coverage for the Eastern half of the U.S. Although the method
of collection can vary by State, the NLFA data generally represent a
combination of data collected from areas of increased angling activity
and areas of suspected contamination. To the extent that the NLFA data
are concentrated in areas of suspected contamination, the MeHg
concentrations in fish based on these data may be biased and
overestimate exposure to anglers and their families. The potential
existence of this bias reflects the varying data collection
methodologies that are selected by each State.
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\39\ U.S. EPA. August 2004. 2003 National Listing of Fish
Advisories. Office of Water. EPA-823-F-04-016. Additional
information available at http://map1.epa.gov/.
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To supplement the NLFA data, EPA is considering using the recently
completed 4-year field study, entitled the National Study of Chemical
Residues in Lake Fish Tissue, which is also referred to as the National
Fish Tissue Study (NFTS). The database contains about 1,000 samples of
freshwater fish from 500 different lakes across the U.S.\40\ The NFTS
is a 4-year national screening-level freshwater fish contamination
study. It is also the first national fish tissue survey to be based on
a statistical (random) sampling design, and it will generate data on
the largest set of persistent bioaccumulative and toxic chemicals ever
studied in fish. The statistical design of the study allows EPA to
develop national estimates of the mean concentrations of 268 chemicals
in fish tissue from lakes and reservoirs of the lower 48 States. EPA
will conduct a quality assurance analysis on the data for each year of
the study. Additional information concerning NFTS is available at
http://www.epa.gov/waterscience/fishstudy/.
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\40\ U.S. EPA. November 2001. National Fish Tissue Study. EPA-
823-F-01-028. See http://www.epa.gov/waterscience/fishstudy/.
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For saltwater fish, there are fewer samples of fish tissue MeHg
data, relative to freshwater information. EPA is considering the use of
the Mercury in Marine Life database (available through the NLFA) that
provides data on the level of Hg contamination in the estuaries and
marine environments nationwide, and the U.S. Food and Drug
Administration's (FDA) database of MeHg concentrations in fish.\41\
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\41\ U.S. Food and Drug Administration. Mercury in Fish: FDA
Monitoring Program (1990-2003). See http://www.cfsan.fda.gov/frf/seamehg2.html.
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[[Page 69877]]
With the above information on MeHg concentrations in fish tissue in
fresh- and salt-water fish, the next question is how do we compute
exposures to affected populations? We recognize that our analysis must
be based on MeHg estimates for fish that are typically consumed by the
U.S. population. The NLFA contains samples that vary by size (i.e.,
several are taken from fish that are potentially consumable based on
size, while other samples are taken from smaller fish that are not
likely to be consumed) and by species. To estimate the MeHg content in
fish species that are typically consumed, EPA is evaluating the
application of the NLFA and NFTS data to a statistical model developed
by Dr. Stephen Wente, USGS, the National Descriptive Model of Mercury
and Fish Tissue (NDMMFT).\42\ The model uses statistical procedures to
estimate a relationship between fish size and MeHg concentrations,
while controlling for fish species, sampling method, location, and
other factors. EPA intends to conduct a peer review of the application
of this model to the NLFA and NFTS data and will place the appropriate
materials in the docket when available.
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\42\ See http://water.usgs.gov/pubs/sir/2004/5199/.
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We are also collecting information on fish consumption rates by
different affected populations, particularly in the eastern half of the
U.S. We recognize that many Americans consume seafood or freshwater
fish; however, some subpopulations in the U.S. (e.g., Native Americans,
Southeast Asian Americans, and lower income subsistence fishers) may
rely on fish as a primary source of nutrition and/or for cultural
practices. Therefore, they may consume larger amounts and different
parts of fish than the general population and may potentially be at a
greater risk to the adverse health effects from MeHg due to increased
consumption/exposure. We intend to use the following consumption data
to complete our analysis concerning the relationship between reductions
in MeHg concentrations in fish tissue and reductions of human exposure
to MeHg.
a. Women of childbearing age--the National Health and Nutrition
Examination Survey (NHANES) provides information based on the women who
participated in the study.\43\
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\43\ Center for Disease Control. National Health and Nutrition
Examination Survey. National Center for Health Statistics. See
http://www.cdc.gov/nchs/nhanes.htm and http://www.cdc.gov/mmwr/preview/mmwrhtml/mm5343a5.htm.
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b. Children--Exposure Factors Handbook and NHANES provide
information.
c. Subsistence fishers and ``high-end'' consumers (including, but
not limited to Native Americans and Asian Americans)--The Exposure
Factors Handbook provides information for subsistence Native American
fishers; Journal articles (Peterson, et al., 1994; \44\ Hutchinson, et
al., 1994 \45\) provide data for specific subpopulations such as
specific Native American tribes and the Asian American population
(i.e., Hmong) located in the Eastern half of the U.S. Peterson, et al.
(1994) assesses the fishing activity of the Chippewa in Minnesota and
Wisconsin. Hutchinson, et al. (1994) assesses the fishing activities of
the Hmong living in Minnesota, Wisconsin, and Michigan. Other studies
exist for these populations, but they do not address consumption
behavior in the Eastern half of the U.S. EPA is interested in
additional information for subsistence anglers (freshwater and/or
saltwater), and for Native Americans or Southeast Asian Americans
living in the Eastern half of the U.S.
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\44\ Peterson, D.E., M.S. Kanarek, M.A. Kuykendall, J.M.
Diedrich, H.A. Anderson, P.L. Remington, and T.B. Sheffy. 1994.
``Fish Consumption Patterns and Blood Mercury Levels in Wisconsin
Chippewa Indians.'' Environmental Health 49(1):53-58.
\45\ Hutchinson, R., and C.E. Kraft. 1994. ``Hmong Fishing
Activity and Fish Consumption.'' Journal of Great Lakes Research
20(2):471-487.
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Finally, EPA notes that the Methyl mercury Water Quality Criterion,
which establishes a MeHg fish concentration designed to be protective
of human health, estimates fish consumption rates. EPA is seeking
comment on whether the MeHg fish concentration set forth in the Water
Quality Criterion or the fish consumption rates used in the Water
Quality Criterion could be used for local, regional, or national
assessments.\46\
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\46\ 66 FR 1345, January 8, 2001.
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2. What specific comments did EPA receive on fish consumption
patterns in response to the January 2004 proposal and the March 2004
supplemental proposal? Several commenters identified existing fish
consumption data, including: CATF, NRDC, et al. (OAR-2002-0056-3460);
EEI (OAR-2002-0056-2929); EPRI (OAR-2002-0056-2578); Forest County
Potawatomi Community (OAR-2002-0056-2173); Minnesota Conservation
Federation, et al. (OAR-2002-0056-2415); and Southern Environmental Law
Center (OAR-2002-0056-4222). We are seeking comment on the usefulness
of the data provided by the commenters.
G. Step 5 of EPA's Proposed Revised Benefits Methodology: How Will
Reductions in Population-Level Exposure Improve Public Health?
A variety of human health effects are associated with MeHg
exposure. Published MeHg research suggests there may be neurological
effects during fetal and child development, including intelligence
quotient (IQ) decrements and more subtle effects on the ability to
learn.\47\ Numerous studies suggest that fish consumption has a
beneficial cardiovascular effect in adult males as a result of its n-3
fatty acids (e.g., Omega-3 fatty acids, etc.). However, research also
raises the possibility that MeHg in fish can reduce the
cardioprotective effects of fish consumption in adult
males.48 49 50
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\47\ National Academy of Sciences. July 2000. Toxicological
Effects of Methylmercury. National Academy of Sciences/National
Research Council; National Academy Press.
\48\ Yoshizawa, et al. 2002. ``Mercury and the Risk of Coronary
Heart Disease in Men.'' New England Journal of Medicine; Nov. 2002;
347(22): 1755-60.
\49\ Guillar, et al. 2002. ``Mercury, Fish Oils, and the Risk of
Myocardial Infarction.'' New England Journal of Medicine; Nov. 2002;
347(22): 1747-54.
\50\ Salonen, et al. 1995. ``Intake of Mercury from Fish, Lipid
Peroxidation, and the Risk of Myocardial Infarction and Coronary
Cardiovascular, and Any Death in Eastern Finnish Men.'' American
Heart Association, 1995.
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The state-of-the-science regarding neurodevelopmental effects in
children has been more thoroughly evaluated and reviewed than that for
other health effects. A review by the National Academy of Sciences
(NAS), published in July 2000, concluded that neurodevelopmental
effects are the most sensitive and well-documented effects of MeHg
exposure. EPA subsequently established a reference dose (RfD) \51\ of
0.0001 milligrams per kilogram of body weight per day (mg/kg/day)
derived from a neurodevelopmental endpoint based on the NAS review. NAS
determined that EPA's RfD ``is a scientifically justified level for the
protection of public health.'' \52\
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\51\ ``In general, the RfD is an estimate (with uncertainty
spanning perhaps an order of magnitude) of a daily exposure to the
human population (including sensitive subgroups) that is likely to
be without an appreciable risk of deleterious effects during a
lifetime.'' See http://www.epa.gov/iris/subst/0073.htm.
\52\ National Academy of Sciences. July 2000. op. cit.
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The RfD was based on three epidemiological studies of prenatal MeHg
exposure in the Faroe Islands, New Zealand, and Seychelles Islands.
These studies examined neurodevelopmental outcomes through the
administration of numerous tests of
[[Page 69878]]
cognitive functioning.53 54 55 These tests provided partial
or full assessments of IQ, problem solving, social and adaptive
behavior, language functions, motor skills, attention, memory, and
other functions. NAS found that all three studies are ``well-designed,
prospective, longitudinal studies.'' \56\
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\53\ Myers, et al. 2003. ``Prenatal Methylmercury Exposure from
Ocean Fish Consumption in the Seychelles Child Development Study.''
The Lancet. Vol. 361; May, 2003.
\54\ Crump, et al. 1998. ``Influence of Prenatal Mercury
Exposure Upon Scholastic and Psychological Test Performance:
Benchmark Analysis of a New Zealand Cohort.'' Risk Analysis, 18(6):
701-713.
\55\ Grandjean. 1997. Cognitive Deficit in 7-Year-Old Children
with Prenatal Exposure to Methylmercury. Neurotoxicology, 19(6):
417-428.
\56\ National Academy of Sciences. July 2000. op. cit. at 267.
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EPA is considering using these three studies to conduct a benefits
assessment. Specifically, EPA is considering focusing on IQ decrements
associated with prenatal MeHg exposure as the initial endpoint for
quantification and valuation of health benefits of reduced exposure to
MeHg. This initial focus in IQ as the neurodevelopmental endpoint for
quantification was supported by participants in a Hg neurotoxicity
workshop held by EPA in November 2002.\57\ Reasons for focusing on IQ
include the availability of thoroughly-reviewed, epidemiological
studies assessing IQ and/or related cognitive outcomes suitable for IQ
estimation; and the availability of well-established methods and data
for the economic valuation of avoided IQ deficits. EPA recognizes that,
although IQ is a good metric of the cognitive impacts of prenatal MeHg
exposure, IQ is not a comprehensive measure of the neurodevelopmental
effects of MeHg exposure.
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\57\ See http://www.epa.gov/ttn/ecas/regdata/Benefits/mercuryworkshop.pdf pdf.
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To potentially support a benefits estimation, EPA is working with
researchers from Harvard University to analyze whether data from the
Faroe Islands, New Zealand, and Seychelles Islands studies on the
relationship between prenatal MeHg exposure and neurodevelopmental
outcomes can be integrated. The study is intended to estimate the
relationship between the exposure to MeHg and decrements in full-scale
IQ, based on all three studies. The Harvard study will likely assume a
linear dose-response relationship. The Faroe Islands and Seychelles
Islands studies did not conduct the complete battery of tests used to
estimate full-scale IQ. Therefore, the study is designed to use the
results from the tests administered to predict full-scale IQ. This
analysis will be peer-reviewed and placed in the docket as soon as it
is available.
EPA is considering using a K-model to fit population-level dose-
response relationships to the pooled data from the three studies. EPA
is also considering, for the purposes of a national-level benefits
assessment, to set K = 1, which assumes a linear relationship between
exposure and effects.
The practicality of using a linear (K = 1) model is the primary
reason that the Agency is considering use of such a model. A linear
model would allow us to estimate the benefits of reductions in exposure
due to power plants without a complete assessment of the other sources
of exposure. Other models would require information on the joint
distribution of exposure from power plants and other sources to
estimate the benefits of reducing the exposure due to power plants,
which would require much more precise information about consumption
patterns than a K-model would require.
EPA is seeking comment on all aspects of the methodology for
estimating the relationship between reductions in MeHg exposure and
improvements in health. In particular, we are seeking comment on the
following:
a. The focus on neurodevelopmental health of children.
b. The selection of IQ as an endpoint for quantification of
neurodevelopmental effects and whether it is an appropriate endpoint
for benefits analysis for reduced exposure to MeHg.
c. Whether other neurodevelopmental effects can be quantified and
are amenable to economic valuation.
d. Whether, and if so how, data from the Faroe Islands, New
Zealand, and Seychelles Islands studies can be integrated for the
purposes of a benefits assessment.
e. The choice of the K = 1 model for the estimating the
relationship between exposure and IQ and practical alternatives to that
approach.
f. The appropriateness and consistency of using a linear dose-
response model given the RfD established by EPA in 2001 (reflecting the
NAS review in 2000), which assumes a threshold dose below which there
is not likely to be an appreciable risk of deleterious effects during a
lifetime.
List of Subjects
40 CFR Part 60
Environmental protection, Administrative practice and procedure,
Air pollution control.
40 CFR Part 72 and 75
Environmental protection, Air pollution control, Electric
utilities.
Dated: November 29, 2004.
Stephen D. Page,
Director, Office of Air Quality Planning and Standards.
[FR Doc. 04-26579 Filed 11-30-04; 8:45 am]
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