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Comments on Methylmercury Draft Guidance Sought by EPA Five Years After Criterion Set
The Environmental Protection Agency is seeking comments on a draft guidance for states and tribes to develop water quality standards based on methylmercury criterion that the agency issued five years ago.
The purpose of this document, Draft Guidance for Implementing the Methylmercury Water Quality Criterion, is to provide approaches that states and tribes can use to develop standards based on the criterion for methylmercury, a compound known to cause neurological defects in children and pregnant women.
"Our clean water guidance helps states turn mercury science into pollution prevention plans to protect public health and watersheds," Benjamin Grumbles, EPA's assistant administrator for water, said in an Aug. 7 statement to BNA.
Five years ago, EPA for the first time recommended water quality criterion for methylmercury to be set at 0.3 milligrams of methylmercury per kilogram of fish tissue rather than of water. EPA usually sets criteria for compounds in water, not for fish in water. Under Section 303(c) of the Clean Water Act, states and authorized tribes must develop water quality standards based on water quality criteria to protect designated uses of fishable, swimmable waters (216 DEN A-15, 11/9/01 ).
EPA's draft guidance instructs states and authorized tribes on
how to translate fish tissue criterion to concentration in ambient water. It
recommends three approaches that use a bioaccumulative factor (BAF), or the
ratio of methylmercury's concentration in an organism's tissue to its
concentration in the water where the organism lives. BAFs measure a chemical's
potential to accumulate in tissue through exposure to both food and water.
EPA recommends development of site-specific BAFs, use of models using
bioaccumulation factors, or use of EPA's draft default methylmercury
bioaccumulation factors. For each approach, the agency describes benefits and
limitations. The guidance also describes methods for detecting mercury and
methylmercury in fish and water at very low levels in order to develop BAFs.
In the draft guidance, EPA acknowledges that more methylmercury will be detected
in the nation's waters, owing to the greater sensitivity of detection
instruments. EPA also provides a method for directly incorporating the
methylmercury criterion into National Pollutant Discharge Elimination System
(NPDES) permits.
Draft Reflects Best Available Science
Since EPA issued its criterion in 2001, 44 states, one territory, and two tribes
have issued fish consumption advisories for mercury covering 13.2 million lake
acres and 765,000 river miles. Mercury is widely found in the environment,
originating through natural sources, such as volcanic eruptions, and through
man-made processes, such as burning of coal in power plants. The primary route
by which the U.S. population is exposed to methylmercury is through consumption
of fish containing this toxic compound.
In response to questions concerning the five-year gap in issuing guidance, EPA
spokesman Dale Kemery explained that expressing water quality criterion for
methylmercury as a fish and shellfish tissue value "raised several technical and
programmatic implementation challenges, such as how to translate a fish tissue
residue value into a water concentration and ultimately into NPDES permit
limits."
In developing the guidance through a work group including state agencies, Kemery
said, EPA wanted to ensure that the guidance reflected the best available
science to date about mercury, including the technical and scientific
information collected in 2004 and 2005 during the development of the Clean Air
Mercury Rule. The draft guidance, he said, generally consolidates existing EPA
guidance and practice into one document. It addresses questions related to
adoption of water quality standards (for example, site-specific criteria and
variances), assessments, monitoring, total maximum daily loads, and NPDES
permitting issues.
Issues Still the Same
The wastewater treatment community has been waiting for this guidance, according
to Susan Bruninga, public affairs director for the National Association of Clean
Water Agencies.
"We had a number of questions back then and we are hoping this guidance will
answer those questions," Bruninga said.
She said those questions included how to translate bioaccumulated concentrations
of methylmercury in fish tissue into observable permit limits for waters and how
to develop total maximum daily loads, or a total budget for a particular
pollutant, in impaired waters.
In 2001, Chris Hornback, NACWA's regulatory affairs director, said that an
increasing number of states were incorporating methylmercury limits in NPDES
permits because EPA issued the criterion. At the time, Hornback said permit
limits were posing a problem for publicly owned sewage treatment plants because
few control options existed, leaving pollution prevention and best management
practices as some of the only viable means of achieving the limits.
Five years later, Bruninga said, "our issues are still the same."
EPA asks that comments be identified by Docket ID No. EPA-HQ-OW-2006-0656 and
submitted electronically to
http://www.regulations.gov
or e-mailed to ow-docket@epa.gov.
The original and three copies may also be mailed to: Water Docket, Attn. Docket
ID No. EPA-HQ-OW-2006-0656, Environmental Protection Agency (4101T), 1200
Pennsylvania Ave. N.W., Washington, D.C. 20460, or hand delivered to EPA Docket
Center (EPA/DC), EPA West, Room B102, 1301 Constitution Ave. N.W., Washington,
D.C. 20460.
EPA's Draft Guidance for Implementing the Methylmercury Water Quality Criterion
is available at
http://www.epa.gov/waterscience/criteria/methylmercury/guidance-draft.html.
By Amena H. Saiyid