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GLIN==> Methyl Mercury Water Quality Criteria

[Federal Register: August 9, 2006 (Volume 71, Number 153)]
[Page 45560-45564]
 From the Federal Register Online via GPO Access [wais.access.gpo.gov]


[EPA-HQ-OW-2006-0656, FRL-8207-3]
Notice of Draft Guidance for Implementing the January 2001 
Methylmercury Water Quality Criterion

AGENCY: Environmental Protection Agency (EPA).
ACTION: Notice of availability and request for comments.


SUMMARY: EPA announces the availability of draft guidance for 
implementing the water quality criterion for methylmercury and requests 
comments on the draft guidance. The draft document provides technical 
guidance to states, territories, and authorized tribes exercising 
responsibility under Clean Water Act (CWA) section 303(c) on how to use 
EPA's fish tissue-based methylmercury criterion recommendation in 
developing their own water quality standards for methylmercury and in 
implementing these standards in Total Maximum Daily Loads (TMDLs) and 
National Pollutant Discharge Elimination System (NPDES) permits. The 
guidance document does not impose any legally binding requirements on 
any entity. It provides various technical and policy approaches to 
implementing the criterion. These approaches are recommendations only. 
States, territories and authorized tribes may choose to implement other 
technically-sound approaches that are consistent with the CWA and EPA's 
implementing regulations.

DATES: Comments must be received on or before October 10, 2006.

ADDRESSES: Submit your comments, identified by Docket ID No. EPA-HQ-OW-
2006-0656, by one of the following methods:
    ? <A HREF="http://www.regulations.gov";>http://www.regulations.gov</A>: Follow the on-line 
instructions for submitting comments.
    ? E-mail: <A HREF="mailto:ow-docket@epa.gov";>ow-docket@epa.gov</A>.
    ? Mail: Water Docket, Environmental Protection Agency, 
Mailcode: 4101T, 1200 Pennsylvania Ave., NW, Washington, DC 20460. 
Please include a total of four copies.
    ? Hand Delivery: EPA Docket Center (EPA/DC), EPA West, Room 
B102, 1301 Constitution Ave., NW., Washington, DC 20460. Please include 
a total of four copies. Such deliveries are only accepted during the 
Docket's normal hours of operation, and special arrangements should be 
made for deliveries of boxed information.
    Instructions: Direct your comments to Docket ID No. EPA-HQ-OW-2006-
0656. EPA's policy is that all comments received will be included in 
the public docket without change and may be made available online at 
<A HREF="http://www.regulations.gov";>http://www.regulations.gov</A>, 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 <A HREF="http://www.regulations.gov";>http://www.regulations.gov</A> or ow-docket@epa.gov. The 
<A HREF="http://www.regulations.gov";>http://www.regulations.gov</A> website is an ``anonymous access'' system, which 
means EPA will not know your identity or contact information unless you 
provide it in the body of your comment. If you send an e-mail comment 
directly to EPA without going through <A HREF="http://www.regulations.gov";>http://www.regulations.gov</A> your 
e-mail address will be automatically captured and included as part of 
the comment that is placed in the public docket and made available on 
the Internet. If you submit an electronic comment, EPA recommends that 
you include your name and other contact information in the body of your 
comment and with any disk or CD-ROM you submit. If EPA cannot read your 
comment due to technical difficulties and cannot contact you for 
clarification, EPA may not be able to consider your comment. Electronic 
files should avoid the use of special characters, any form of 
encryption, and be free of any defects or viruses. For additional 
information about EPA's public docket visit the EPA Docket Center 
homepage at <A HREF="http://www.epa.gov/epahome/dockets.htm";>http://www.epa.gov/epahome/dockets.htm</A>
    Docket: All documents in the docket are listed in the 
<A HREF="http://www.regulations.gov";>http://www.regulations.gov</A> index. Although listed in the index, some 
information is not publicly available, e.g., CBI or other information 
whose disclosure is restricted by statute. Certain other material, such 
as copyrighted material, will be publicly available only in hard copy. 
Publicly available docket materials are available either electronically 

[[Page 45561]]

<A HREF="http://www.regulations.gov";>http://www.regulations.gov</A> or in hard copy at the Water Docket, EPA/DC, EPA 
West, Room B102, 1301 Constitution Ave., NW, Washington, DC. The Public 
Reading Room is open from 8:30 a.m. to 4:30 p.m., Monday through 
Friday, excluding legal holidays. The telephone number for the Public 
Reading Room is (202) 566-1744, and the telephone number for the Water 
Docket is (202) 566-2426).

    Note: The EPA Docket Center suffered damage due to flooding 
during the last week of June 2006. The Docket Center is continuing 
to operate. However, during the cleanup, there will be temporary 
changes to Docket Center telephone numbers, addresses, and hours of 
operation for people who wish to make hand deliveries or visit the 
Public Reading Room to view documents. Consult EPA's Federal 
Register notice at 71 FR 38147 (July 5, 2006) or the EPA Web site at 
<A HREF="http://www.epa.gov/epahome/dockets.htm";>http://www.epa.gov/epahome/dockets.htm</A> for current information on 
docket operations, locations and telephone numbers. The Docket 
Center's mailing address for U.S. mail and the procedure for 
submitting comments to <A HREF="http://www.regulations.gov";>http://www.regulations.gov</A> are not affected by the 
flooding and will remain the same.

FOR FURTHER INFORMATION CONTACT: Jim Pendergast, Standards and Health 
Protection Division, Office of Water, (4305T), Environmental Protection 
Agency, 1200 Pennsylvania Ave., NW, Washington, DC, 20460; telephone 
number: 202-566-0398; fax number: 202-566-0409; e-mail address: <A HREF="mailto:Pendergast.jim@epa.gov";>


I. General Information

A. Does this Action Apply to Me?

    Entities potentially interested in today's notice are those that 
discharge or release mercury and methylmercury to surface waters, and 
federal, state, tribal, and local authorities that regulate 
methylmercury levels in surface water. Categories and entities 
interested in today's notice include but are not limited to:

                                               Examples of potentially
                 Category                         affected entities
State/Local/Tribal Government.............  States, municipalities,
Industry..................................  Mining, coal-fired power
                                             generation, other
                                             industries using mercury in
                                             their processing

    This table is not intended to be exhaustive. Other types of 
entities not listed in the table may also be interested.

B. What Should I Consider as I Prepare My Comments for EPA?

    1. Submitting CBI. Do not submit this information to EPA through 
<A HREF="http://www.regulations.gov";>http://www.regulations.gov</A> 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:
    ? Identify the docket number and other identifying 
information (subject heading, Federal Register date and page number).
    ? Follow directions--The agency may ask you to respond to 
specific questions or organize comments by referencing a Code of 
Federal Regulations (CFR) part or section number.
    ? Explain why you agree or disagree; suggest alternatives 
and substitute language for your requested changes.
    ? Describe any assumptions and provide any technical 
information and/or data that you used.
    ? If you estimate potential costs or burdens, explain how 
you arrived at your estimate in sufficient detail to allow for it to be 
    ? Provide specific examples to illustrate your concerns, and 
suggest alternatives.
    ? Explain your views as clearly as possible, avoiding the 
use of profanity or personal threats.
    ? Make sure to submit your comments by the comment period 
deadline identified.

II. Background and Today's Action

A. What Is Methylmercury and Why Are We Concerned About It?

    Mercury occurs naturally in the earth's crust and cycles in the 
environment as part of both natural and human-induced activities. The 
amount of mercury mobilized and released into the biosphere has 
increased since the beginning of the industrial age. Most of the 
mercury in the atmosphere is elemental mercury vapor, which circulates 
in the atmosphere for up to a year, and, hence, can be widely dispersed 
and transported thousands of miles from sources of emission. Most of 
the mercury in water, soil, sediments, plants, and animals is in the 
form of inorganic mercury salts and organic forms of mercury (e.g., 
methylmercury). Methylmercury most often results from microbial 
activity in wetlands, the water column, and sediments and is the form 
of mercury that presents the greatest risk to human health. Divalent 
mercury, when bound to airborne particles, is readily removed from the 
atmosphere by precipitation and is also dry deposited. Even after it 
deposits, mercury commonly returns to the atmosphere either as a gas or 
associated with particles, and redeposits elsewhere. As mercury cycles 
between the atmosphere, land, and water, mercury undergoes a series of 
complex chemical and physical transformations, many of which are not 
completely understood.
    Exposure to methylmercury can result in a variety of health effects 
in humans. Children who are exposed to low concentrations of 
methylmercury prenatally might be at risk of poor performance on 
neurobehavioral tests, such as those measuring attention, fine motor 
function, language skills, visual-spatial abilities, and verbal memory. 
(NRC 2000, USEPA 2002, USEPA 2005). The primary route by which the U.S. 
population is exposed to methylmercury is through the consumption of 
fish containing methylmercury. For most people, methylmercury exposure 
from consumption of fish and shellfish is not a health concern. Yet, 
the exposure levels at which neurological effects have been observed in 
children can occur via maternal consumption of fish (rather than high-
dose poisoning episodes) (USEPA 2005). The risks from methylmercury in 
fish and shellfish depend on the amount of fish and shellfish eaten and 
the levels of methylmercury in the fish and shellfish. Therefore, the 
Food and Drug Administration (FDA) and the Environmental Protection 
Agency (EPA) are advising women who may become pregnant, pregnant 
women, nursing mothers, and young children to avoid some types of fish 
and eat fish and shellfish that are lower in methylmercury. You can 
find more information about this joint Federal advisory on EPA's Web 
site at <A HREF="http://www.epa.gov/waterscience/fish";>http://www.epa.gov/waterscience/fish</A>.
    In 2000, the National Academy of Sciences (NAS)/National Research 
Council (NRC) reviewed the health studies on methylmercury (NRC 2000). 
In its review of the literature, NRC found neurodevelopmental effects 
to be the most sensitive endpoints and appropriate for establishing a

[[Page 45562]]

methylmercury Reference Dose (RfD) (NRC 2000). EPA defines an RfD as 
``an estimate (with uncertainty spanning perhaps an order of magnitude) 
of a daily oral exposure to the human population (including sensitive 
subgroups) that is likely to be without an appreciable risk of 
deleterious effects during a lifetime. On the basis of the NRC report, 
EPA established an RfD of 0.0001 mg/kg per day (0.0001 milligram of 
methylmercury per day for each kilogram of a person's body mass) in 
2001 (USEPA 2002). EPA believes that exposures at or below the RfD are 
unlikely to be associated with appreciable risk of deleterious effects. 
It is important to note, however, that the RfD does not define an 
exposure level corresponding to zero risk; methylmercury exposure near 
or below the RfD could pose a very low level of risk that EPA deems to 
be non-appreciable. It is also important to note that the RfD does not 
define a bright line, above which individuals are at risk of adverse 
effects (USEPA 2005). NAS determined that EPA's RfD ``is a 
scientifically justified level for the protection of public health.''
    With regard to other health effects of methylmercury, some recent 
epidemiological studies in men suggest that methylmercury is associated 
with a higher risk of acute myocardial infarction, coronary heart 
disease, and cardiovascular disease in some populations. Other recent 
studies have not observed this association. The studies that have 
observed an association suggest that the exposure to methylmercury 
might attenuate the beneficial effects of fish consumption (USEPA 
2005). There also is some recent evidence that exposures of 
methylmercury might result in genotoxic or immunotoxic effects. Other 
research with less corroboration suggests that reproductive, renal, and 
hematological impacts could be of concern. There are insufficient human 
data to evaluate whether these effects are consistent with 
methylmercury exposure levels in the U.S. population (USEPA 2005).

B. What Is the Current Methylmercury Criterion?

    In a January 8, 2001, Federal Register notice (66 FR 1344), EPA 
announced the availability of its recommended water quality criterion 
for methylmercury. The methylmercury water quality criterion is derived 
from the methylmercury RfD (described above) and data about the target 
population to be protected (i.e., exposure parameters and assumptions). 
The equation for calculating the methylmercury fish tissue residue 
water quality criterion for the protection of human health is:


TRC = Fish tissue residue criterion (mg methylmercury/kg fish 
tissue) for freshwater and estuarine fish and shellfish
RfD = Reference Dose (based on non-cancer human health effects). For 
methylmercury the RfD is 0.0001 mg/kg BW-day (0.1 ug/kg BW-day)
RSC = Relative source contribution (subtracted from the RfD to 
account for marine fish consumption) estimated to be 2.7 x 10-5 mg/
kg BW-day
BW = Human body weight default value of 70kg (for adults)
FI = Fish intake at trophic level (TL) i (i = 2, 3, 4); total 
default intake is 0.0175 kg fish/day for general adult population. 
Trophic level breakouts for the general population are: TL2 = 0.0038 
kg fish/day; TL3 = 0.0080 kg fish/day; and TL4 = 0.0057 kg fish/day.

    This equation and all values used in the equation are described in 
Water Quality Criterion for the Protection of Human Health, 
Methylmercury (USEPA 2001b). This equation is essentially the same 
equation used in the 2000 Human Health Methodology to calculate a water 
quality criterion for a pollutant that may cause non-cancer health 
effects, but is rearranged to solve for a protective concentration in 
fish tissue rather than in water. Thus, the equation does not include a 
bioaccumulation factor (BAF) or drinking water intake value 
(methylmercury exposure from drinking water is negligible (USEPA 
2001a)). Incorporating the relevant values into the above equation, EPA 
obtained a fish tissue concentration (TRC) of 0.3 mg methylmercury/kg 
fish as the concentration in fish tissue that should not be exceeded. 
EPA's preference is for states and authorized tribes to use local or 
regional consumption rates, if these would better reflect the target 

C. What Is The Draft Implementation Guidance?

    In the 2001 Federal Register notice of the availability of EPA's 
recommended water quality criterion for methylmercury, EPA stated that 
it would develop associated procedures and guidance for implementing 
the criterion. We are issuing that draft guidance today. The guidance 
will assist states in developing a water quality criterion for 
methylmercury in their water quality standards. States can either adopt 
EPA's recommended criterion or another criterion that is scientifically 
defensible and consistent with the Act and its implementing 
regulations. 40 CFR 131.11(a)(2).
    This guidance document presents suggested approaches to criteria 
adoption and implementation. These approaches are recommendations and 
do not represent the only technically defensible approaches. The 
discussion in the guidance document is intended solely as guidance. 
This guidance does not change or, substitute for, applicable sections 
of the CWA or EPA's regulations; nor is it a regulation itself. Thus, 
it does not impose legally binding requirements on EPA, states, 
authorized tribes, or the regulated community and may not apply to a 
particular situation. EPA, state, territorial, and tribal decision 
makers retain the discretion to adopt approaches on a case-by-case 
basis that differ from this guidance where appropriate.

D. Why Did EPA Draft This Guidance?

    The methylmercury criterion is expressed as a fish and shellfish 
tissue value, and this raises both technical and programmatic 
implementation questions. EPA expects that, as a result of the revised 
methylmercury water quality criterion, together with a more sensitive 
method for detecting mercury in effluent and the water column, and 
increased monitoring of previously unmonitored waterbodies, the number 
of waterbodies that states report on CWA section 303(d) lists as 
impaired due to methylmercury contamination might continue to increase. 
Development of water quality standards, NPDES permits, and TMDLs 
present challenges because these activities typically have been based 
on a water concentration (e.g., as a measure of mercury levels in 
effluent). This guidance addresses issues associated with states and 
authorized tribes adopting the new water quality criterion into their 
water quality standards programs and implementation of the revised 
water quality criterion in TMDLs and NPDES permits. Further, because 
atmospheric deposition serves as a large source of mercury for many 
waterbodies, implementation of the criterion involves coordination 
across various media and program areas.

E. What Does the Draft Guidance Recommend?

    For states and authorized tribes exercising responsibility under 
CWA section 303(c), this document provides technical guidance on how 
they might want to use the recommended 2001 fish tissue-based criterion 
to develop their own water quality standards for

[[Page 45563]]

methylmercury. States and authorized tribes may decide to adopt the EPA 
recommended methylmercury fish tissue-based criterion based on the 
national default fish consumption rate or translate the tissue value to 
a water column value through use of methylmercury BAFs. If a state or 
authorized tribe decides to translate the fish tissue criterion to a 
water column criterion, EPA recommends three approaches for relating a 
concentration of methylmercury in fish tissue to a concentration of 
methylmercury in ambient water: (1) Deriving site-specific 
methylmercury BAFs; (2) using bioaccumulation models; and (3) using 
EPA's draft default methylmercury BAFs. All three approaches have 
limitations, such as the amount of data necessary to develop a BAF. 
This guidance discusses the advantages and limitations of each approach.
    States and authorized tribes may also consider calculating their 
own fish tissue criteria or adopting site-specific criteria for 
methylmercury to reflect local or regional fish consumption rates or 
relative source contributions. This guidance also discusses variances 
and use attainability analyses relating to methylmercury.
    This document describes analytical methods for determining the 
concentrations of mercury and methylmercury in both tissue and water. 
These methods can detect mercury and methylmercury in tissue and water 
at very low levels--well below the levels of the previous criterion for 
mercury in the water column and the current criterion of methylmercury 
in fish tissue. This document also provides guidance for field sampling 
plans, laboratory analysis protocols, and data interpretation that is 
based on previously published EPA guidance on sampling strategies for 
contaminant monitoring. This guidance also describes how states can 
assess the attainment of water quality criteria and protection of 
designated uses by comparing sampling data to water quality criteria.
    This guidance also discusses approaches for the development of 
TMDLs for waterbodies impaired by mercury. This includes approaches for 
TMDLs for waterbodies where much of the mercury is from atmospheric 
sources and suggestions regarding how such TMDLs can take into account 
ongoing efforts to address sources of mercury, such as programs under 
the Clean Air Act (CAA) and pollution prevention activities.
    EPA's Technical Support Document for Water Quality-based Toxics 
Control (TSD), EPA 505/2-90-001, explains how to implement criteria 
expressed in terms of pollutant concentrations in water in NPDES 
permits. States that decide to implement the methylmercury tissue 
criterion as a water concentration for NPDES permits should continue to 
use the TSD guidance. However, for states that decide to implement the 
methylmercury tissue criterion directly, that is, without translating 
it into a water column value, the TSD doesn't provide relevant 
guidance. Today's draft guidance also includes a recommended approach 
for directly incorporating the methylmercury tissue criterion in NPDES 

F. Are There Particular Issues on Which EPA is Requesting Comment?

    EPA requests comments only on the draft methylmercury criterion 
implementation guidance. EPA is not requesting comments on the 2001 
methylmercury criterion itself. Although EPA solicits comment on the 
entire draft guidance, it is particularly interested in the following 
1. Implementation Approach for NPDES Permits Where the Criterion Is 
Implemented as a Fish Tissue Value
    Today's guidance presents a recommended approach for directly 
incorporating the methylmercury tissue criterion in NPDES permits. This 
approach does not rely upon a state developing a bioaccumulation factor 
to convert the methylmercury tissue criterion into a water 
concentration equivalent. The approach recommends that facilities that 
use, accept or receive mercury into their wastewaters develop mercury 
minimization plans. For discharges that are small contributors of 
mercury to a watershed or do not use mercury in their processes, the 
approach recommends that current permit effluent levels remain 
constant. EPA expects that most facilities will fall into this category 
due to significant loadings from other sources (e.g., air deposition, 
abandoned mines). For discharges that are significant contributors of 
mercury to a watershed and use mercury in their processes, the approach 
recommends that permit effluent limits ensure the attainment of water 
quality standards. EPA expects that few dischargers should fall into 
this category. For new or increased discharges, the approach recommends 
that permit effluent limits hold watershed loadings constant using 
antidegradation principles.
    EPA solicits comment on the recommendations for directly 
incorporating the methylmercury tissue criterion in NPDES permits. The 
draft guidance recommends that a permitting authority could reasonably 
conclude that reasonable potential exists if two conditions are present 
(1) The NPDES permitted discharger has mercury in its effluent at a 
quantifiable level and (2) fish tissue from the waterbody into which 
the discharger discharges exceeds the fish tissue water quality 
criterion. EPA specifically solicits comment on alternate methods, 
based on using other information, for determining that there is 
reasonable potential to exceed the water quality standard where fish 
tissue data show that the methylmercury tissue criterion in a water 
quality standard is achieved.
2. Applying Water Quality Variances on a Watershed or State-Wide Basis
    Traditionally, states establish water quality variances that are 
specific to a pollutant and a facility. EPA recognizes that, for 
mercury, there are situations where a number of NPDES dischargers are 
located in the same area or watershed and the justification supporting 
granting a variance applies to all of the dischargers. Two states, Ohio 
and Michigan, have already developed variances that apply to multiple 
discharges for mercury. Today's guidance encourages states and 
authorized tribes to consider establishing a multiple-discharger 
variance for a group of dischargers collectively.
    EPA solicits comment on whether it should discuss multi-discharge, 
watershed, or state-wide variances in the final guidance.

G. References Cited

NRC (National Research Council). 2000. Toxicological effects of 
methylmercury. Committee on the Toxicological Effects of 
Methylmercury. National Academy Press. Washington, DC.
USEPA (U.S. Environmental Protection Agency). 1991. Technical 
Support Document for Water Quality-based Toxics Control. EPA 505/2-
90-001. U.S. Environmental Protection Agency, Office of Water 
Enforcement and Permits and Office of Water Regulations and Standards.
USEPA (U.S. Environmental Protection Agency). 2001a. Water quality 
criteria: Notice of Availability of water quality criterion for the 
protection of human health: Methylmercury. U.S. Environmental 
Protection Agency, Office of Water, Washington, DC. Fed. Regist., 66:1344.
USEPA (U.S. Environmental Protection Agency). 2001b. Water quality 
criterion for the protection of human health: Methylmercury. EPA-
823-R-01-001. U.S. Environmental Protection Agency, Office of Water, 
Washington, DC.
USEPA (U.S. Environmental Protection Agency). 2002. Integrated Risk 
Information System (IRIS). Methylmercury. U.S. Environmental 
Protection Agency, Office

[[Page 45564]]

of Research and Development, National Center for Environmental Assessment.
USEPA (U.S. Environmental Protection Agency). 2005. Regulatory 
Impact Analysis of the Clean Air Mercury Rule. Final Report. EPA-
452/R-05-003. U.S. Environmental Protection Agency, Office of Air 
Quality Planning and Standards, Air Quality Strategies and Standards 
Division, Research Triangle Park, NC.

    Dated: August 3, 2006.
Benjamin H. Grumbles,
Assistant Administrator for Water.
[FR Doc. 06-6803 Filed 8-8-06; 8:45 am]


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