United States
                   Environmental Protection
                   Agency
Office of Water
4304T
EPA-822-F-02-003
December 2002
CvEPA    Fact  Sheet
     Summary
                   Notice of Ambient   Water Quality Criteria
                    Document for Tributyltin (TBT) -  Draft
     The U.S. Environmental Protection Agency has published a draft ambient water quality criteria
     document for tributyltin (TBT) for scientific and technical input. Draft acute and chronic criteria
     recommendations have been developed to protect aquatic life in both freshwater and saltwater.
     When finalized, these draft criteria can form the basis for state and tribal water quality standards.
     Background

     The U.S. Environmental Protection Agency (EPA)
     has published a draft ambient water quality criteria
     document for tributyltin (TBT) for scientific and
     technical input. This document contains draft
     ambient water quality criteria to protect aquatic
     organisms and their uses. These draft criteria are
     technical information for states and tribes and, in
     themselves, have no binding legal effect. When
     finalized, these criteria can form the basis for state
     and tribal water quality standards. These draft
     TBT criteria are published pursuant to Section
     304(a) of the Clean Water Act.

     What is tributyltin?

     Tributyltin is one of several organotin compounds
     with several industrial uses. Organotins are
     organometallic compounds; they contain one or
     more direct links between a carbon atom and a
     metal atom.

     How is TBT used?

     Tributyltin is primarily used as a biocide in
     antifouling paints applied to ship hulls to keep
     barnacles and other organisms from attaching to
     the hull. TBT remains effective over long periods
     on the ship hull because it is released very slowly
     from the hull into the water column over time.
     This keeps organisms from attaching to the hull.
What are the environmental effects of TBT?

Tributyltin is extremely toxic to aquatic life. It is
especially toxic to bivalves, such as oysters and
other mollusks. It is an endocrine-disrupting
chemical that causes severe reproductive effects
in aquatic organisms.  In addition, recent studies
show that exposure to TBT makes oysters very
susceptible to infection and death from exposure
to pathogens.

What are the new draft criteria
concentrations?
In August 1997, EPA published a draft ambient
water quality criteria document for TBT which
contained freshwater and saltwater criteria.
With this notice, EPA is issuing new draft
criteria for TBT.  The  primary difference
between the initial draft and the new draft
criteria is that the saltwater chronic criterion has
been lowered from a four-day average of 0.01
ug/1, not to be exceeded more than once in three
years, to a four-day average of 0.001 ug/1, not to
be exceeded more than once in three years. EPA
set the criterion at this level to protect saltwater
organisms from the adverse reproductive effects
of tributyltin that have been observed in
laboratory and field studies and because
exposure to TBT can make saltwater organisms
more vulnerable to infection from pathogens.
                                                    Freshwater Aquatic Life:

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EPA has determined that, except possibly where a
locally important species is very sensitive,
freshwater aquatic life and their uses should not be
affected unacceptably if the four-day average
concentration of tributyltin does not exceed 0.063
ug/L more than once every three years on the
average and if the one-hour average concentration
does not exceed 0.46 ug/L more than once every
three years on the average.


Saltwater Aquatic Life:

EPA has determined that, except possibly where a
locally important species is very sensitive,
saltwater aquatic life and their uses should not be
affected unacceptably if the four-day average
concentration of tributyltin does not exceed 0.001
ug/L more than once every three years on the
average and if the one-hour average concentration
does not exceed 0.38 ug/L more than once every
three years on the average.
How do I obtain a copy of the document?

Copies of the complete document, titled
"Ambient Aquatic Life Water Quality Criteria
for Tributyltin (LBL) - Draft" (EPA-822-B-02-
001) may be obtained from EPA's Water
Resource Center by phone at 202-566-1729, or
by e-mail to waterpubs(giepamail.epa.gov. or by
conventional mail to EPA Water Resource
Center, RC-4100T,  1200 Pennsylvania Ave.,
Washington, DC 20460. The document is also
available electronically at:
www.epa.gov/waterscience/criteria/tributyltin.
What are the environmental benefits from these
new draft criteria?

The new TBT draft criteria provide more
protection for commercially and ecologically
important species, including oysters.  The revised
saltwater chronic criterion protects saltwater
organisms from the adverse growth and
reproductive effects of TBT.

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