540/09-87-172
TRIBUTYLTIN: POSITION DOCUMENT 1
Office of Pesticide Programs
Office of Pesticides and Toxic Substances
U.S. Environmental Protection Agency
401 M Street, S.W.
Washington, DC 20460
December 1985
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Executive Summary
This Tributyltin Support Document presents the basis for
the initiation of a Special Review of all pesticide products
containing tributyltin (TBT) active ingredients used as paint
additives (antifoulants) to inhibit the growth of certain aquatic
organisms. The TBT paints are primarily applied to boat and ship
hulls._ These TBT compounds include: bis-(tributyltin) oxide,
bis(tributyltin) adipate, bis(tributyltin) dodecenyl succinate,
bis(tributyltin) sulfide, tributyltin acetate, tributyltin acrylate,
tributyltin fluoride, tributyltin methacrylate, and tributyltin
resinate.
The initiation of the Special Review is based on the Agency's
determination that the use of the TBT compounds in antifoulant
paints may result in TBT exposure to nontarget aquatic organisms
at concentrations resulting in acute and chronic effects. The
Agency has determined that the risk criteria, as described in 40
CFR 162.11 are met or exceeded by use of these TBT antifoulant
paints.
The Agency evaluated bioassay studies which indicated that
the TBT compounds are highly toxic, frequently at the parts per
trillion (ppt) level, to nontarget marine and freshwater aquatic
organisms. Toxicity tests have found adverse affects to molluscs
at levels of 60 and 100 ppt. The laboratory toxicity measure
which the Agency used to evaluate the acute hazard was the median
lethal concentration (LC50) which kills 50 percent of the test
organisms after a designated time period. The Agency also reviewed
numerous aquatic toxicity studies which indicate that the TBT
compounds cause chronic hazards such as anatomical abnormalities,
growth effects, and is bioaccumulated.
Environmental monitoring data measuring TBT concentrations
in the Great Lakes and U.S. coastal waters were compared to the
concentrations identified as causing adverse effects in the
laboratory toxicity studies. From this comparison, the Agency
has determined that the risk criteria, as described in 40 CFR
162.11 are met or exceeded by use of these TBT antifoulant paints.
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ACKNOWLEDGEMENTS
Janet L. Anderson
Kyle R. Barbehenn
Michael A. Champ
Stanley A. Cook
John D. Doherty
Robert K. Hitch
Peter Kuch
Thomas W. Purcell
Allan J. Reiter
Michael Rexrode
Philip J. Ross
Myra Smith
Linda K. Vlier
Suzanne Wells
Project Team
Plant Pahtologist, OPP/BUD
Biologist, OPP/HED
Senior Science Advisor, OPPE
Assist. Review Manager, OPP/RD
Toxicologist, OPP/HED
Ecologist, OPP/HED
Supervisory Economist, OPP/BUD
Environmental Scientist, OWRS
Chemist, OPP/HED
Fisheries Biologist, OPP/HED
Attorney, OGC
Microbiologist, OPP/BUD
Senior Review Manager, OPP/RD
Environ. Protection Specialist, OPPE
Additional assistance also provided by:
Robert J. Huggett
Virginia Institute of Marine Science
College of William and Mary
Gloucester Point, Virginia
Peter F. Seligman
Marine Environmental Branch
U.S. Naval Ocean Systems Center
San Diego, California
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TABLE OF CONTENTS
I. INTRODUCTION 1-1
A. General Background and Organization 1-1
B. Legal Background 1-1
C. Chemical Background 1-2
II. ASSESSMENT OF RISK II-l
A. Toxicity of TBT to Nontarget Aquatic
Organi sms 11- 2
B. Exposure: TBT in the Marine and
Freshwater Environment 11-13
C. Risk Summary 11-20
III. BENEFITS III-l
A. Antifoulant Paint Use Pattern III-l
B. Tributyltin Antifoulant Paint Registrations ... III-l
C. Usage of Tributyltin Antifoulant Paints
and Alternatives III-2
D. Benefits of TBT Usage III-3
IV. OTHER REGULATORY CONSIDERATIONS IV-1
A. Expansion of Special Review IV-1
B. Data Call-in Notices IV-2
V. BIBLIOGRAPHY V-l
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3
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I. INTRODUCTION
A. General Background and Organization
The Environmental Protection Agency (EPA) is initiating
a Special Review of all pesticide products containing tributyltin
(TBT) active ingredients used as paint additives (antifoulants)
to inhibit the growth of certain aquatic organisms. The TBT
paints are primarily applied to boat and ship hulls. These
TBT compounds include: bis(tributyltin) oxide, bis(tributyltin)
adipate, bis(tributyltin) dodecenyl succinate, bis(tributyltin)
sulfide, tributyltin acetate, tributyltin acrylate, tributyltin
fluoride, tributyltin methacrylate, and tributyltin resinate.
This Tributyltin Support Document presents the basis for
initiation of the Special Review on these nine active ingredients.
The EPA has determined that the pesticidal use of
these compounds results in TBT exposure to nontarget aquatic
organisms at concentrations resulting in acute and chronic toxicity
and, when applied as antifoulant paints, meet or exceed the risk
criteria as described in 40 CFR 162.11. Accordingly, a Special
Review of products containing these TBT compounds and applied
as antifoulant paint is appropriate to determine whether additional
regulatory actions are required. During the Special Review
process, EPA will carefully examine the risks and benefits of
using TBT products as antifoulants. If the information reviewed
indicates that use of these compounds on other sites results in
exposure to nontarget aquatic organisms, the Special Review may
be extended to include other pesticidal applications of these
products and other TBT active ingredients with registered uses
which result in aquatic acute and/or chronic effects or other
effects of concern.
This Support Document contains four parts. Chapter I is
this Introduction. Chapter II describes the risk to nontarget
aquatic organisms resulting from the use of TBT compounds in
antifoulant paints. Chapter III describes the usage and benefits
of these TBT compounds. Chapter IV outlines other regulatory
considerations associated with the TBT compounds.
B. Legal Background
1. The Statute
A pesticide product may be sold or distributed in
the United States only if it is registered or exempt from regis-
tration under the Federal Insecticide, Fungicide, and Rodenticide
Act (FIFRA) as amended (7 U.S.C. 136 et seq.). Before a product
can be registered, it must be shown that it can be used without
"unreasonable adverse effects on the environment" (FIFRA section
3(c)(5)), that is, without causing "any unreasonable risk to
1-1
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man or the environment, taking into account the economic/
social, and environmental costs and benefits of the use of
the pesticide" (FIFRA section 2(bb)). The burden of proving
that a pesticide meets this standard for registration is at
all times, on the proponent of initial or continued registration.
If at any time the Agency determines that a pesticide no longer
meets this standard for registration, then the Administrator
may cancel the registration under section 6 of FIFRA.
2. The Special Review Process
The term "Special Review" is the name being used
for the process previously called the Rebuttable Presumption
Against Registration (RPAR) process 40 CFR 162.11. Modifications
to the process are described in the final Special Review regu-
lations (50 FR 49003). These regulations will become effective
after 60 days of continuous congressional session after the
issuance of the regulations, which took place on November 19,
1985. These modifications include new risk criteria. Until
these regulations are adopted, the present RPAR procedures
will remain in effect as set forth in 40 CFR 162.11.
The Special Review (RPAR) process provides a
mechanism through which the Agency gathers risk and benefit
information about pesticides which appear to pose risks of
adverse effects to human health or the environment which may be
unreasonable. Through issuance of notices and support documents,
the Agency publicly sets forth its position and invites pesticide
registrants, USDI, USDA, FDA, user groups, environmental groups,
and other interested persons to participate in the Agency's
review of suspect pesticides.
Risk evidence, submitted to and/or gathered by the
Agency, must be evaluated and considered in light of the benefit
information. If the Agency determines that the risks appear
to outweigh the benefits, the Agency can initiate action
under FIFRA to cancel, suspend, and/or require modification
of the terms and conditions of registration.
C. Chemical Background
1. Registered Uses and Production
There are 20 tributyltin compounds registered as
pesticidal active ingredients. Nine of the TBT compounds are
registered for use in antifoulant paints. Other registered uses
of the TBT's include but are not limited to: use as wood preser-
vatives, textile biocides, disinfectants, use in cooling towers,
paper and pulp mills, and leather processing facilities. Current
annual domestic production of TBT pesticides for these uses is
estimated at approximately 730,000 to 860,000 pounds of active
1-2
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ingredient for the 20 TBT active ingredients. Approximately
a third of the TBT is used in antifoulant paints, one third is
used in wood preservatives, and the remaining third is used
in other pesticidal formulations.
2• Chemical and Physical Characteristics of TBT's in
Antifouling Paints
The tributyltin antifouling paints are chemically
characterized by a tin (Sn) atom covalently bonded to three butyl
(C^Hg-) moieties. A representative TBT active ingredient,
tri-n-butyltin fluoride, may be chemically described by the
following structural formulas for the undissociated (neutral)
pure form of the active ingredient and for the water dissociated
(positively charged) form:
H9C4 — Sn — C4H9 H9C4 — Sn
Elemental or inorganic forms of tin (as in mineral
deposits or tin cans) appear to cause negligible toxicological
effects in man or wildlife. However, in contrast, the TBTs
display an increased fat solubility and consequently, enhanced
ability to penetrate biological membranes, thereby posing a
greater toxicity and environmental risk (Thayer 1984). When
tributyltin is used as an active ingredient in antifouling paint
formulations that are applied for example to boat hulls, the free
TBT ion is leached or released from the paint, providing fresh
toxicant at the wetted paint surface to inhibit growth of fouling
organisms (e.g., barnacles, tubeworms ) .
Table 1 identifies the nine tributyltin active
ingredients under consideration in the Special Review and their
Chemical Abstract Service (CAS) number.
In general, the TBT antifouling paints may be
classified into two categories according to the way the tributyltin
moiety is incorporated into the paint coating and subsequently
released. In the first group, the conventional freely associated
coatings (e.g., TBT oxide or fluoride), the biocide is physically
incorporated into the paint matrix (which contains the pigment,
water-soluble resins, and inert substances). Upon contact with
the marine environment, the surface particles of the paint coating
are dissolved with physical release of the toxic TBT by diffusion.
This category of TBT antifoulant coatings have traditionally
posed a problem of a high early release rate with subsequently
shortened time period of protection from attachment and growth
of fouling organisms (Fisher e_t a±. 1981). In the second
category, the copoylmer paints, the TBT moiety is chemically
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Table 1. Tributyltin Active Ingredients as Used in
Antifoulant Paints
Chemical Abstract
Chemical Name Service Number
bis(tributyltin) oxide 56-35-9
bis(tributyltin) dodecenyl 12379-54-3
succinate
bis(tributyltin) sulfide 4804-30-4
tributyltin acetate 56-36-0
tributyltin acrylate 13331-52-7
tributyltin fluoride 1983-10-4
tributyltin resinate none assigned
tributyltin methacrylate, 2155-70-6,
and copolymer and 26345-187
bis(tributyltin) adipate 7437-35-6
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bonded to a polymer backbone (e.g., TBT methacrylate copolymer).
This bond is designed to be hydrolytically unstable under
slightly alkaline conditions. Therefore, the biocide is
released only by chemical hydrolysis of the tributyltin itself.
This attachment (pendant polymer) accounts for several advantages:
1) release is governed by hydrolysis of the TBT group rather
than dissolution of the paint particle, 2) the release rate
can be better controlled (slowed down) by alteration of the
polymer's water absorption characteristics, and 3) the formulation
is safer for shipyard personnel to handle because the biocide
is released only when wetted and also the polymeric form poses
less irritation to skin and nasal passages. With the exception
of the initial high release rate during the "conditioning"
period (approximately the first month after the freshly painted
hull is placed in the water), these polymeric, film-forming
resin coatings are characterized by a slow dissolution rate from
ship hulls and thus the ability to achieve a constant but prolonged,
low release rate of antifouling toxicant (ibid.).
In general, toxicity of organotin compounds to
aquatic organisms is thought to increase with the number of butyl
substituents from one to three (Laughlin, Norlund, and Linden
1984) and then to decrease with the addition of a fourth butyl
group. In order to assess the fate of a particular tributyltin
derivative in water one must consider the dissociated active
form, the TBT cation (Bu^Sn"1"), and its major metabolites
presumably formed by progressive debutylation to inorganic
tin (Blunden 1984).
Bu3Sn+ —> Bu^Sn2"1" —> BuSn3+ —> Sn4 +
In addition, Matthias and coworkers (1985) have
prepared a manuscript for publication (currently in review by
Analytical Chemistry) containing their findings of relatively
high levels of tetrabutyltin in surface (microlayer) water samples
from Baltimore harbor. This species (Bu4Sn) could possibly be
formed from microbial/photolytic transformation of the tri-
and dibutyl forms which could then be reconverted to the dibutyl
species. The tetrabutyltin species may also be present in
some paint formulations as an impurity in the manufacturing
process. Also, butylmethyltin (Bu3MeSn) has been isolated
from marine sediment samples (ibid.).
Analytical methodology suitable for environmental
monitoring must, in view of the foregoing discussion, be able to
detect at low levels all butyltin and mixed methylbutyltin species
arising from degradation of the TBT cation in marine and fresh-
water environments. Furthermore, because morphological and
toxicological effects have been found to occur in nontarget aquatic
organisms when exposed to TBT concentrations in the parts per
trillion (ppt) range, the analytical methodology must have a
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corresponding low limit of detection. A number of speciation
methods (separation and analysis) have been reported in connection
with environmental monitoring studies; these have been reviewed
by Brinckman (1983). More recently, Brinckman and coworkers have
prepared a manuscript which presents a simple and rapid method
for the speciation of aquatic samples using simultaneous hydri-
dization/extraction with separation by gas chromatography and
detection by flame photometry (Matthias et al. 1985). In using
100 mL salt water samples, the level of detection was said to be
7 ppt of tetrabutyltin, 7 ppt of tributyltin, 3 ppt of dibutyltin,
and 22 ppt of monobutyltin.
Among the methods cited in this Support Document in
connection with environmental monitoring or bioassay studies are
those that measure the four butyltin species (BunSn) and inorganic
tin. They are based upon preliminary extraction and purification
using an organic solvent (benzene, tropolone, hexane, methyl
isobutylketone) followed by formation of a volatile derivative
with a Grignard reagent (butyl-, pentylor hexylmagnesium bromide)
or with sodium borohydride (hydride). Species separation is then
accomplished by either gas chromatography (GC) or programmed warming
in a purge/trap (PT) system with detection of the volatilized
organotin derivative by atomic absorption spectroscopy (AA), flame
photometric detection (FPD) or mass spectroscopy (MS). Detection
limits for tributyltin (cation) in marine water columns have been
reported at 7 ppt (Matthias et al. 1985, using hydridization and
GC/FPD); 20 ppt (Maguire et al. 1982, using butyl or pentyl
derivatives and either GC/FPD or GC/AA) ; 5 ppt (Valkirs ej: al.
1985, using hydrization and PT/AA); and, 5 ppt (Huggett 1985,
using hexyl derivatives and GC/FPD with confirmation by MS). To
achieve these detection limits sample volumes have varied from
500 mL to 2000 mL.
Since higher levels of TBT have usually been observed
in surface microlayer, fish tissues and other sorbing media
including sediment, analytical methods for these specimens have
been cited with higher detection limits. These include 60 to 150
ppt for surface microlayers (Maguire 1982, using 100 mL samples
by GC/FPD); 5000. ppt for marine sediment (Maguire 1982, using 1
gram dry specimens by GC/FPD); and, 80 ppt for fish tissue (Waldock
and Thain 1983, on tissue using flameless AA).
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II- ASSESSMENT OF RISK
The EPA has determined that registered products and
applications for registration of pesticide products containing
the following active ingredients in antifouling paints: bis
(tributyltin) oxide, bis(tributyltin) adipate, bis(tributyltin)
dodecenyl succinate, bis(tributyltin) sulfide, tributyltin
acetate, tributyltin acrylate, tributyltin fluoride, tributyltin
methacrylate, and tributyltin resinate meet or exceed the existing
criteria (40 CFR 162.11) and new risk criteria (50 FR 49003) for
acute and chronic hazard to nontarget aquatic organisms.
Tributyltin compounds are very effective biocides, toxic to
marine and freshwater organisms at extremely low concentrations.
The use of tributyltin compounds in antifoulant paints, has
resulted in increased concentrations of TBT in harbors, marinas,
and estuaries. Environmental hazard to nontarget organisms
(i.e., nonfouling organisms such as mussels, clams, and oysters)
is highly probable, where TBT concentrations have been measured
at or near the recorded acute and chronic toxicity levels for
various nontarget aquatic organisms including commercially
valuable marine organisms.
EPA has determined that the use of pesticide products
containing bis(tributyltin) oxide, bis(tributyltin) adipate,
bis(tributyltin) dodecenyl succinate, bis(tributyltin) sulfide,
tributyltin acetate, tributyltin acrylate, tributyltin fluoride,
tributyltin methacrylate, and tributyltin resinate when used in
antifoulant paints exceeds the risk criterion for acute and
chronic toxicity as defined in 40 CFR 162.11(a)(3)(i)(B) and 40
CFR 162.11 (a)(3)(ii)(C) which provide that a Special Review
shall be conducted if a pesticide:
"results in a maximum calculated concen-
centration following direct application
to a 6-inch layer of water more than 1/2
the acute LC$Q for aquatic organisms
representative of the organisms likely
to be exposed . . ." (40 CFR 162.11(a)(3)(ii)(B))
Or if use of the chemical:
"can reasonably be anticipated to result
in significant local regional or national
population reductions in nontarget
organisms, or fatality to members of
endangered species." (40 CFR 162.11(a)(3)(ii)(C))
The Agency has issued new Special Review regulations which
include revised risk criteria. Although these criteria are
not in place at the present, we have concluded that these TBT
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products also meet or exceed the new risk criterion (50 FR
49003) because concentrations of TBT in the marine and freshwater
aquatic environments may result
"in residues of the pesticide product or
its ingredients, impurities, metabolites, or
other degradation products in the environ-
ment of nontarget organisms at levels which
equal or exceed concentrations acutely or
chronically toxic to such organisms . . .
at levels which produce adverse reproductive
effects in such organisms as determined
from tests conducted on representative
species or from other appropriate data."
This chapter consists of three sections. The first
discusses the toxicity of TBT to nontarget aquatic organisms;
the second presents the concentrations of TBT which have been
found in the marine and freshwater environments; and the third
section summarizes the potential risk posed by the use of TBT
active ingredients in antifouling paint formulations.
A. Toxicity of TBT to Nontarget Aquatic Organisms
1. Introduction
In this toxicity section, information summarizing
the adequacy of historical bioassay tests and the acute and
chronic toxicity of TBT to fish, algae, crustaceans, and molluscs
will be summarized.
2 . Measurement of Toxicity
Only recently have data been available on the
toxicity and environmental fate of tributyltin compounds, espe-
cially with an interest toward delineating the relationship which
may exist between the number of alkyl groups (i.e., tributyl,
dibutyl, and monobutyl) and the toxicities of these compounds.
Many studies were conducted as static bioassays with nominal non-
measured (estimated) concentrations. Nominal values do not take
into account the tributyltin adsorption onto test containers
resulting in an overestimate of the actual available toxicant
in the solution. Since the concentration of TBT toxicant can be
overestimated, the LC50 reported may underestimate the TBT toxicity
(e.g., while the actual LC5Q may be 60 ppt, the reported value
may be 100 ppt since the TBT concentration was not measured). This
adsorption problem is critical at very low levels (i.e., < 1.0 ppb)
where a 70 percent decrease (almost an order of magnitude) has
been found between nominal and measured concentrations of
tributlytin (M & T Chemical Co., Aug. 1977).
H-2 \\
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Static renewal bioassay testing procedures may
provide accurate estimates of tributyltin concentration if the
test solution renewal period is brief; this procedure eliminates
lengthy resident times and loss of tributyltin by adsorption
and/or subsequent degradation to intermediate forms. Flowthrough
bioassay testing with simultaneous chemical analyses for chemical
speciation of the toxicant in solution is, however, a more
desirable testing approach.
The detection limits of TBT concentration measurement
are of major concern. TBT has been detected in water column
samples using the borohydride method (Matthias et al. 1985) as
low as 7 ppt. This method is most effective with large water
sample sizes. The Virginia Institute of Marine Science (VIMS)
has been able to detect levels of tributyltin as low as 2.0 ppt
(Perkins 1985). The determination of environmental concentrations
in water column samples is critical to the development of a risk
assessment. The inability to measure low ppt levels of TBT can
result in an erroneous assessment of hazard at the sublethal
chronic level.
The following discussion characterizes the concerns
EPA has regarding tributyltin toxicity to nontarget aquatic
organisms subsequent to their exposure to TBT concentrations now
found in harbors, marinas, lakes, and estuaries. Table 2
summarizes the TBT toxicity data used to initiate the Special
Review. It should be noted that different investigators used
different chemical forms (salts) of TBT in conducting the aquatic
toxicity studies. These included the chloride, the bis(tributyltin)
oxide and the methacrylate. Although LC5Q values were reported
using these different forms of TBT, their effect on the final
measured or calculated result is relatively negligible. For
example, the molecular weight ratio between the bis(tributyltin)
oxide and tributyltin chloride is only two-fold, whereas, the
acute toxicities vary across species of fish by approximately
24-fold.
3. Toxicity to Fish
Acute toxicity testing usually measures the lethal
(LC5Q) or effective (EC^Q) concentrations where 50 percent of the
test organisms are killed or significantly affected. Acute
toxicity of bis(tributyltin) oxide (TBTO) to certain freshwater
fish appears to range from 0.96 ppb to 24.0 ppb. Reported 96-hour
LC5Q values (nominal concentrations) for rainbow trout (Salmo
gairdneri), bluegill (Lepomis macrochirus), channel cat fish
(Ictalurus punctatus) , and mummichog (Fundulus heteroclitus) were
6.9, 7.6, 12.0, and 24 ppb, respectively (M & T Chemical Co.
Sept. 1976; Oct. 1976; June 1978). These studies were static
nonrenewal, using nominal concentrations, and may not be sensitive
indicators of actual toxicity (i.e., actual LC50 levels could be
70 percent lower due to adsorption to test container surfaces and
volatilization).
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Table 2. Test Conditions, Procedures, and Results of Tributyltin Toxicity Tests
Test Organism
FISH
Leponis
macrochirus
(Bluegill)
Salmo gairdneri
(Rainbow trout)
Ictalurus
punctatus
(Channel catfish)
Fundulus
heteroclitus
( Mumnichog )
Salmo gairdneri
(Rainbow trout)
Organotin
Ccmpound
TBTO
TBTO
TBTO
TBTO
TBTO
Effect
96-hr LCso =7.6 ppb
(5.6 to 10 ppb)
96-hr LCso =6.9 ppb
(6.27 to 7.8 ppb)
96-hr LCso = 12-° PE*
(7.3 to 20.0 ppb)
96-hr LCso =24.0 ppb
24 hr EC50 = 31.0 ppb
(loss of positive
rheotaxis). Level fron
5850 ppb to 11.7 ppb.
TBTO resulted in damage
to gill epithelium. At
11.7 ppb there was a
flattening of bile duct
columnar epithelial
cells and separation
fron connective tissue
after 5-day exposure.
Destruction of corneal
epithelium occurred
after 7-day exposure
to 11.7 ppb.
Analytical
Methods
Nominal
concentrations
Nominal
concen tra t ions
Nominal
concentra t ions
Nominal
concen tra t ions
Not reported
Type of
Exposure
Static
Static
Static
Static
Continuous
flow stain-
less steel
tanks
Concentration
Levels
5.6, 7.5, 10.0 and
14.0 ppb
4.1, 5.3, 6.8, 8.8,
and 11.0 ppb
7.5, 14.0, 18.0,
24.0 and 28.0
ppb
32.0, 42.0, and
56.0 ppb
5850 to 11.7 ppb
acetone
Reference
M & T
Chemical Co.
(Oct. 1976)
M & T
Chemical Co.
(June 1978)
M & T
Chemical Co.
(Sept. 1976)
M & T
Chemical Co.
(Sept. 1976)
Chliamovitch
& Kuhn
(1976)
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Table 2. Test Conditions, Procedures, and Results of Tributyltin Toxicity Tests (Continued)
Test Organism
Cyprinodon
variegatus
( Sheepshead
minnow)
33 to 49 ran
Cyprinodon
variegatus
( Sheepshead
minnow)
17 to 25 mm
Salmo gairdneri
(Rainbow trout
yolk sac fry)
Organotin
Compound
TBTO
14C-TBTO
TBTCL
Effect
21-day LCso =0.96 ppb
Total mortality at
3.2 ppb at 14 days.
The maximum observed
bioconcentration fac-
tors were X2120 and
X4580 for the head and
viscera, respectively.
After 58 days the de-
puration of 14C-TBTO
frcm all tissues was
rapid. (52% after 7
days).
10 to 12 day LCioo =
5.0 ppb. Decrease in
growth rate at 0.2 and
1.0 ppb for 110 days.
Toxicity not observed
at 0.2 and 1.0 ppb;
hemoglobin concentra-
tion and erythrocyte
count were reduced in
blood; hyperplasia and
diminished glycogen
content observed in
liver.
Analytical
Methods
AAS measured
concent rat ions
LSC measured
concen tra t ions
Nominal
concentrations
Type of
Exposure
21-day
flow-
through
acute
testing
Exposed to
TBTO for
58 days.
110-day
continuous-
flow expo-
sure
Concentration
Levels
0.33, 0.63, 0.70,
1.5, 3.2.
acetone-methanol
0.96 to 2.07 ppb
acetone
0, 0.2, 1.0, and
5.0 ppb
Reference
Ward
et al.
(1981)
Ward
et al.
(1981)
Seinen
et al.
(1981)
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Table 2. Test Conditions, Procedures, and Results of Tributyltin Toxicity Tests (Continued)
Test Organism
Organotin
Compound
Effect
Analytical
Methods
Type of
Exposure
Concentration
Levels
Reference
ALGAE
Ankistrodesmus
falcatus
(Freshwater algae)
Skeletonema
costatum
(Marine diatoms)
w Thalassiosira
<* pseudonana
(Marine diatoms)
TBTO
TBTO
TBTO
A maximum algal bio-
concentration factor
of 3 x 1()4 was esti-
mated for TBT after
7 days.
72 hr EC50 = 0.33 ppb
72 hr EC5Q = 1.03 ppb
GC and FPD
ICAP
ICAP
Static
Static
Nominal
(only
stock
measured)
Static
Nominal
(only
stock
measured)
20 ppb
methanol
0.5, 1.0, 5.0, 7.5,
10.0, 15.0, and
25.0 ppb
0.5, 1.0, 5.0, 7.5,
10.0, 15.0, and
25.0 ppb
Maguire
et al.
(1984)
Walsh
et al.
(1985)
Walsh
et al.
(1985)
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Table 2. Test Conditions', Procedures, and Results of Tributyltin Toxicity Tests (Continued)
Test Organism
CRUSTACEANS
Crangon crangon
(Shrimp)
Acartia tonsa
(Copepod)
Homarus americanus
M (Lobster larvae)
i
~j
Rhithroponopeus
harrisii
(Mud crab)
Daphnia magna
(Water flea)
Organotin
Compound
TBTO
TBTO
TBTO
TBTO
TBTO
Effect
Larvae 96 hr LC50 =
1.5 ppb. Adult- 96 hour
LC5Q = 41 ppb.
72 hr EC5o = 2.1 ppb
96 hr EC5Q =1.0 ppb
144 hr EC50 =0.4 ppb
90% decrease in growth
at 1.0 ppb.
Bioaccumulation of
4400X in the hepato-
pancreas. No steady
state achieved. Accu-
mulation of TBTO from
food greater than from
only the water
48 hr LC5o =1.67 ppb
(1.01 to 2.5 ppb)
Analytical
Methods
Not reported
Measured con-
centrations
AAS
Nominal
concentra t ions
Measured con-
centration of
•t M .
C14 radio-
assay.
Nominal
concentration
Type of
Exposure
Static re-
newal every
24 hours
Static re-
newal every
24 hours
Pyrex test
tubes
Static re-
newal every
48 hours
Static re-
newal every
24 hours.
Artemia
with con-
centrations
1.23 ug
TBTO/g wet
weight were
fed to
crabs.
Static
Concentration
Levels
Not reported
0.3, 0.5, 1.0, 1.7,
and 3.0 ppb
acetone "
1.0, 5.0, 10.0,
15.0, and 20.0
ppb
0.28 ppb and
6.1 ppb
1.7, 3.0, 5.3, 7.1,
and 13.3 ppb
ethanol
Reference
Thain
(1983)
U'ren
(1983)
Laughlin &
French
(1980)
Evans &
Laughlin
(1984)
M & T
Chemical Co
(Jan. 1976)
-------
Table 2. Test Conditions, Procedures, and Results of Tributyltin Toxicity Tests (Continued)
Test Organism
MOLLUSCS
Crassostrea
virginica
(Eastern oyster
larvae)
Crassostrea gigas
(Pacific oyster
larvae)
Mytilus edulis
(Mussel larvae)
M
v
oo Mytilus edulis
(Mussel larvae)
Crassostrea gigas
(Pacific oyster
spat)
Mytilus edulis
(Mussel spat)
Organotin
Compound
TBTO
TBTO
TBTO
TBTO
Exposure for
45 days to
tributyltin
methacrylate
leachates
Exposure for
45 days to
tributyltin
methacrylate
leachates
Effect
48 hr EC50 - 0.9 ppb
(0.4 to 1.9 ppb)
48 hr LCso =1.6 ppb
48 hr LC5o = 2.3 ppb
15 day LCso =0.1 ppb
long-term effect
Significant reduction
in growth at 0.24 ppb
Significant reduction
in growth at 0.24 ppb
Analytical
Methods
Nominal
Concent rat ion
Not reported
Not reported
Measured con-
centrations
FAAS
Measured daily
for 3 weeks
and every
other day for
the remainder
of the experi-
ment (M&T
standard
method)
Measured daily
for 3 weeks
and every
other day for
the remainder
Type of
Exposure
Static
Static re-
newal every
24 hours
Static re-
newal every
24 hours
Static re-
newal every
72 hours
Flow-
through
Flow-
through
Concentration
Levels
0.1, 0.3, 0.6, 1.0,
3.2, and 5.6 ppb
Not reported
Not reported
10.0, 1.0, and 0.1
ppb
0.24 + 0.23 ppb
for low-level and
2.62 + 1.09 ppb
for hTgh level
0.24 -I- 0.23 ppb
for low- level and
2.62 + 1.09 ppb
for hTgh level
Reference
M&T
Chemical Co
(June 1977)
Thain
(1983)
Thain
(1983)
Beaumont
& Budd
(1984)
Thain &
Waldock
(1985)
Thain &
Waldock
(1985)
-------
Table 2. Test Conditions,.Procedures, and Results of Tributyltin Toxicity Tests (Continued)
Test Organism
Mytilus edulis
(Mussel spat)
(Continued)
Venerupis
decussata
(Clam spat)
Ostrea edulis
(European oyster
spat)
Venerupis
semidecussata
(Clam spat)
Organotin
Compound
Exposure for
45 days to
tributyltin
methacrylate
leachates
Exposure for
45 days to
tributyltin
methacrylate
leachates
Exposure for
45 days to
tributyltin
methacrylate
leachates
Effect
Significant reduction
in growth at 0.24 ppb
Growth inhibited at
2.6 ppb
Growth inhibited at
2.6 ppb
Analytical
Methods
of the experi-
ment (M&T
standard
method)
Measured daily
for 3 weeks
and every
other day for
the remainder
of the experi-
ment (M&T
standard
method).
Measured daily
for 3 weeks
and every
other day for
the remainder
of the experi-
ment (M&T
standard
method).
Measured daily
for 3 weeks
and every
other day for
the remainder
of the experi-
ment (M&T
standard
method) .
Type of
Exposure
Flow-
through
Flow-
through
Flow-
through
Concentration
Levels
0.24 + 0.23 ppb
for low-level and
2.62 + 1.09 ppb
for hTgh level
0.24 + 0.23 ppb
for low- level and
2.62 + 1.09 ppb
for high level
0.24 + 0.23 ppb
for low- level and
2.62 + 1.09 ppb
for hTgh level
Reference
Thain &
Waldock
(1985)
Thain &
Waldock
(1985)
Thain &
Waldock
(1985)
-------
Table 2. Test Conditions, Procedures, and Results of Tributyltin Toxicity Tests-(Continued)
Test Organism
Organotin
Conpound
Effect
Analytical
Methods
Type of
Exposure
Concentrat ion
Levels
Referenc
Ostrea edulis
(European oyster
spat)
Crassostrea gigas
(Pacific oyster)
Ostrea edulis
.(European oyster)
TBTO
TBTO
TBTO
M
O
Crassostrea gigas
(Pacific oyster
spat)
TBTO
Nassarius
obsoletus
(Mud snail)
Alumacide
TBT paint
Growth effected at
0.02 ppb (marginal).
At 0.06 ppb growth
rate was severely
curtailed after 10
days.
Bioaccumulation of
2000 to 6000 fold after
22 days (poor diet
was noted).
Bioaccuraulation of
1000 to 1500 fold
after 22 days (poor
diet was noted).
Spat grew poorly at
TBT concentrations of
0.15 ppb; developed
pronounced thickening
of upper shell valve.
Bioconcentration
(Flesh) after 56 days
exposure to 0.15 ppb
was about XI1400 fold.
Anatomical abnormality
consisting of super-
imposition of male
characteristics on
female snails.
Nominal con-
centration
renewed every
day. (M&T
standard
method).
FAAS measured
for the first
5 days of
exposure and
FAAS measured
for the first
5 days of
exposure and
on alternate
days until the
completion.
FAAS measured
(M&T Standard
method)
Static
renewal
24 hours
0.02 to 2.0 ppb
Flow-
through
Flow-
through
0.15 and 1.25 ppb
0.15 and 1.25 ppb
Static re-
newal 24
hours
0.08 to 1.2 ppb
Not reported
Not reported
Not reported
QC
Gas Chironiatography
Flame •photometric Detection
Thain &
Waldock
(1985)
Waldock,
Thain, an
Miller
(1983)
Waldock,
Thain, an
Miller
(1983)
Waldock
Thain
(1983)
Smith
(1981)
FAAS = Flameless Atomic Absorption Spectrophotometry
LSC = Liquid Scintillation Counting
-------
(r . Ward (Ward e_t al. 1981) found that sheepshead minnow
fi Pfun " varieqat"s) exposed to TBTO for 21 days (measured
riowthrough system) had an LC50 of 0.96 ppb and total mortality
fh i ?ayS at a Concentration of 3.2 ppb. It was further noted
tnat after exposure to TBTO (0.96 to 2.07 ppb) for 58 days, the
maximum observed bioconcentration factors were 2120X and 4580X
SS-!^ and viscera/ respectively. He also noted that after an
aaaitional 58 days (i.e., 116 days total) the depuration, or
elimination, of TBTO from all tissue was rapid (52% after 7 days
post-exposure).
Chronic effects on fish were found by Seinen e_t aJ .
11981) after subjecting rainbow trout yolk sac fry to 110 day
exposure to concentrations of tributyltin chloride (continuous-flow
exposure, nominal concentrations). A 10 to 12 day LC100 of 5
ppb was estimated using concentration levels 0.2, 1, and 5 ppb.
Although, young trout exposed to tributyltin chloride concen-
trations of 0.2 and 0.1 ppb did not exhibit mortality, there was
a significant reduction in growth (40% decrease in body weight),
decrease in hemoglobin content, hyperplasia of liver cells, and
diminished glycogen content in liver. Chilamovitch and Kuhn
(1976) noted histological and hematological effects on rainbow
trout after continuous exposure to TBTO. Damage to gill epithelium
was recorded at 1.7 ppb. At 11.7 ppb with 5 days of exposure,
there was a flattening of bile duct columnar epithelial cells and
separation of these cells from connective tissue. Destruction of
corneal epithelium was observed following 7 days of exposure to
11.7 ppb.
4. Toxicity to Algae
The toxicity of tributyltin compounds to algae has
not been intensively studied. Maguire et al. (1984) noted that
the freshwater algae (Ankistrodesmus falcatus) possesses a mechanism
for sequential debutylation of TBTO. However, Walsh et al. (1985)
found that TBTO inhibited population growth and cell survival of
marine unicellular algae Skeletonema costatum and Thalassiosira
pseudonana at low concentrations (72 hour EC5Q of 0.33 ppb and
EC5Q of 1.03 ppb, respectively).
5. Toxicity to Crustaceans
The toxicity of tributyltin to crustaceans was
evaluated by several researchers. Laughlin (1980) using nominal
concentrations in a static daily renewal, found that lobster larvae
(Homarus americanus) exhibited a 90 percent decrease in growth
at 1 ppb. U'ren (1983) calculated a 144 hour EC$Q for marine
copepods (Acartia tonsa) at 0.4 ppb (measured concentrations
static daily renewal). Thain (1983) reported 96 hours LCsg values
for larvae and adult shrimp (Crangon crangon) at 1.5 and 41 ppb,
respectively.
11-11 °*~
-------
Tributyltin bioaccuraulation in crustaceans was
demonstrated by Evans and Laughlin (1984) with their work on mud
crabs (Rhithroponopeus harrisii) exposed to radiocarbon labeled
TBTO. The test measured the short-term effects of exposure to
labeled test concentrations in water (9.28 ppb) and food (Artemia,
1.23 ppb). Four-day bioaccumulation factors ranged up to 4400 in
the hepatopancreas with no indication that a steady state equili-
brium had been approached. Accumulation of tributyltin from food
was greater than that from the water.
6. Toxicity to Molluscs
Acute toxicity of TBTO to certain molluscs appears
to range from 0.1 to 2.3 ppb. Reported 48-hour LC^Q values for
Eastern oyster larvae (C_. virginica), Pacific oyster larvae
(C_. gigas) and mussel larvae (M. edulis) were 0.9, 1.6 and 2,3
ppb, respectively (M & T Chemical Co. June 1977; and Thain
1983). A 15-day LC5Q of 0.1 ppb was also reported for mussel
larvae (M_. edulis) (Beaumont and Budd 1984).
Anatomical abnormalities attributed to tributytins
were found in certain intertidal mud snails (Massarius obsoletus)
living near yacht basins (Long Island Sound and Southport, CT).
Smith (1981), by investigating this phenomenon it was noted that
these dioecious snails had developed male characteristics on
apparently normal female reproductive anatomy. The correlation
between tributyltin concentration and these abnormalities was
later confirmed in laboratory studies.
European researchers have found a significant corre-
lation between the TBTO concentration levels in certain estuarine
areas and shellfish deformity. Waldock and Thain (1983) in England
found that Pacific oyster (Crassostrea gigas) spat (set oyster
larvae) grew poorly in TBTO concentrations of 0.15 ppb, and
developed pronounced thickening of the upper shell valve. Bio-
concentration factors, after 56 days exposure to 0.15 ppb TBTO,
were 11,400X. Alzieu e_t al. (1980) observed similar malformations
in C. gigas and attributed it to the presence of organotin (TBTO
and TBTF) in the French shellfish regions. Beaumont and Budd
(1984) noted that common mussel (Mytilus edulis) larvae did not
survive past 5 days at a TBTO exposure concentration of 10 ppb,
or longer than 10 days at a TBTO level of 1 ppb. They concluded
that the high TBT levels found at several estuarine sites are
associated with adult shellfish population reductions in these
areas (a 15 day LC50 of 0.1 ppb was estimated). Thain and Waldock
(1985) tested several shellfish larvae with tributyltin methacrylate
leachates in measured flow-through systems. They found that Pacific
oyster (Crassostrea gigas), mussel (Mytilus edulis), and clam
(Venerupis decussata) showed a significant reduction in growth at
0.24 ppb. A static renewal (nominal concentrations) test with
spat of the European flat oyster (Ostrea edulis) demonstrated
that growth rate was severely curtailed following exposure to
0.06 ppb TBTO.
II-l?
-------
According to Waldock and Thain (1983), oysters (£.
gigas and O. edulis) rapidly bioaccumulate TBT and reach an
equilibrium uptake after exposure, and subsequently are slow to
depurate this uptake. Using measured concentrations in a 21-day
continuous-flow system, Waldock and Thain exposed C. gigas and
O. edulis (10 g wet weight) to TBTO concentrations of 1.25 and
0.15 ppb. C. gigas accumulated a high body level of tributyltin
that ranged from 2000- to 6000-fold. 0. edulis maintained under
the same conditions only concentrated tributyltin from 1000- to
1500-fold. This twofold to fourfold difference in tissue concen-
tration of tributyltin between species correlates with the threefold
to ninefold difference found in the field.
The probability of food chain accumulation was
addressed by Laughlin, French, and Guard (1984), studying
tributyltin uptake by marine mussels (Mytilus sp.). TBT
bioaccumulated from 1000 to 6000 times and was attributed more
to food intake than to direct absorption from water or sediment.
Given its high lipophilicity TBT is likely to be
bioaccumulated by several organisms. Laboratory studies may '
underestimate the extent of bioaccumulation as they are generally
of insufficient duration to allow all compartments within the
test vessel (food material, feces, water, test organisms, vessel
walls, etc.) to reach equilibrium. Studies are needed to evaluate
the subsequent toxicity problems associated with high bioaccumu-
lation of TBT.
B. Exposure: TBT in the Marine and Freshwater Environment
In addition to review of available bioassay and aquatic
toxicity data, the Agency has also evaluated data available on
TBT concentrations in water samples analyzed from both marine and
freshwater environments. Analytical methods sensitive to the ppt
level have only recently been developed and monitoring data using
this new methodology are currently very limited. Some of this
information is shown in Table 3. Data from Canadian harbors in
Lake Superior and Lake Ontario are included to provide some
indication of the likely contamination levels in Great Lakes
harbors and other freshwater bodies with similar water craft use
patterns.
The data from San Diego Bay, at present, is one of the
most systematic analyses of tributyltin levels in a U.S. bay or
estuary (Valkirs et al., 1985). On the basis of informal surveys
of local retail outlets, Valkirs and coworkers estimated that the
use of tributyltin on recreational craft in this bay greatly
increased during the course of the study. This appears to be
reflected by a sharp elevation in the concentration of TBT in the
waters near Shelter Island Yacht harbor where a study maximum.of
930 ppt tributyltin was measured. This investigation in the
Shelter Island waters is particularly significant because
11-13
-------
antifouling paints are likely to have been the only source of
tributyltin in that area (i.e. there are no drydock TBT discharges
or other TBT point discharges identified in the area). In relation
to the entire San Diego Bay study, it should be noted that,
although tributyltin is thought to readily bind to sediment,
(U.S. Naval Sea Systems Command 1984) divers taking discrete
water samples 10 cm above the bottom sediments found approximately
the same concentrations as were detected in surface water samples.
Figure 1 identifies the location of the sampling stations.
The monitoring data discussed above may not be totally
comparable to values (LCso's etc.) reported in aquatic toxicity
studies. Most aquatic toxicity studies are conducted with
filtered water into which the toxin has been initially dissolved.
The monitoring data reviewed above represent unfiltered water
analyses which would, perhaps, include sediment bound toxin and
even, perhaps, tributyltin which had been assimilated into plank-
tonic organisms. Further investigation as to whether or not a
large proportion of aqueous TBT would be in a bound form is
needed. If binding is found to be significant then the toxico-
logical significance will have to be determined.
There is also reason to believe that the monitoring data
might underestimate the hazard. The Great Lakes and Chesapeake
Bay researchers with whom the Agency has been in direct contact
state that none of their samples have been taken in the late
spring when freshly painted boats would be launched. Monitoring
by Waldock and Miller (1983) in an English estuary found highest
annual concentrations in May (corresponding to the postwinter
launching of pleasure craft).
In addition to the samples noted in Table 3 are samples
collected by Virginia Institute of Marine Science (VIMS) upstream
.and downstream (as influenced by tidal action) from large
commercial ships moored near the Elizabeth River in Hampton Roads.
The concentration of tributyltin above the ships was approximately
5 ppt. The concentration in the surface water downstream from
ships was 13 ppt. Figure 2 identifies the sampling stations used
for the VIMS one day study.
Attempts were made during the Annapolis and Great Lake
studies to measure, the concentration of tributyltin in the
surface microlayer—where high concentrations of lipophilic
pesticides have been found, as noted from other studies in the
literature. Contamination of the water surface is presumed to be
injurious to floating fish eggs such as croaker, herring, and
shad species. Unfortunately no completely satisfactory method of
sampling such a thin layer of the water column is available.
11-14
-------
Table 3.
Tributyltin Concentrations (ng/L = ppt) for Water Samples)V Collected
at Indicated Stations with Analytical Method Noted
Location
Annapolis, MD
Across harbor
frcm city docks
Marina in Back
Creek
Lake Superior
(Marathon)
Lake Ontario
(Toronto Harbor)
Lake Ontario
(Hamilton Harbor)
Lake Ontario
(Whitby Harbor)
San Diego Bay2/
Station 3-2
3 Jan 83
Station 3-3
3 Jan 83
it
14 Feb 84
Station 3-4
3 Jan 83
ii
Station 4
3 Jan 83
ii
14 Feb 84
Station 5
3 Jan 83
n
14 Feb 84
lan Diego Bay
Station 1
3 Jan 83
n
Concentration
(ppt TBT+J
34
71
20
840
160
50
50
130
100
550
180
10
110
ND
30
30
ND
ND
10
ND
10
Sample Type
Depth (Meters)
1
1
5
5
5
5
0.3-0.6
BottomV
0.3-0.6
Bottom
0.3-0.6
0.3-0.6
Bottom
0.3-0.6
Bottom
0.3-0.6
0.3-0.6
Bottom
0.3-0.6
0.3-0.6
Bottom
Analytical
Method
Hydride deriviti-
zation, GC/FPD
Hydride deriviti-
zation, GC/FPD
Pentyl deriviti-
zation GC/FPD
Pentyl deriviti-
zation GC/FPD
Pentyl deriviti-
zation GC/FPD
n
Hydride deriviti-
zation, AA^/
n
n
M
n
n
n
n
n
M
n
H
Hydride derviti-
zation, AA
n
Ref.
1
1
2
2
2
2
3
3
3
3
3
3
3
3
3
3
3
3
3
. 3
11-15
-------
Table 3. Tributyltin Concentrations (ng/L = ppt) for Water Samples^/ Collected
at Indicated Stations with Analytical Method Noted (Continued)
Location
San Diego (Cont.)
Station 2-1
3 Jan 83
n
20 Jun 84
7 Mar 85
25 Sep 85
Station 2-2
3 Jan 83
"
14 Feb 84
2 Jul 85
25 Sep 85
Station 2-3
3 Jan 83
11
14 Feb 84
Station 3-1
3 Jan 83
11
14 Feb 84
18 Dec 84
Elizabeth River, Near
Norfolk, Va5/
16 Sep 1985
Station 1
Station 2
Station 3
Station 4
Station 5
Station 6
Station 7
Station 8
Concentration
(ppt TBTf)
60
100
270
290
780
50
60
350
490
930
20
40
200
180
140
200
210
6
6
7
12
21
63
49
39
Sample Type
Depth (Meters)
0.3-0.6
Bottom
0.3-0.6
0.3-0.6
0.3-0.6
0.3-0.6
Bottom
0.3-0.6
0.3-0.6
0.3-0.6
0.3-0.6
Bottom
0.3-0.6
0.3-0.6
Bottom
0.3-0.6
0.3-0.6
1
1
n
n
n
it
»
n
Analytical Ref.
Method
Hydride deriviti- 3
zation, AA
3
3
3
3
3
3
3
3
3
3
3
3
3
3
3
3
Hexyl deriviti- 4
zation
n 4
4
11 4
4
" 4
4
" 4
11-16
-------
I/ All water samples were whole. No filtered samples were made.
2/ See Figure 1 for location of sampling stations.
3/ Bottom samples were taken 10 cm from the bottom by scuba divers,
4/ AA Hydrogen flame atomic absorption spectrcphometry.
5/ See Figure 2 for location of sampling stations.
References
1. Matthias et al. 1985.
2. Macguire et al. 1982.
3. Valkirs et al. 1985.
4. Perkins 1985.
-------
Figure 1. Navy Sampling Stations in San Diego Bayl/
3. COMMERCIAL BASIN
2. SHELTER ISLAND
YACHT BASIN
4. COMMERCIAL
DRYDOCX
5. NAVAL STATION
NORTH ISLAND
NAS
1. COAST
GUARD
STATION
. . . , COMMERCIAL
BASIN
YACHT REPAIR
FACILITIES
FISHERMAN PT
SAN DIEGO BAY
£/ Valkirs et al. 1985.
11-18
-------
lgure 2. Virginia Institute of Marine Science Sampling
Stations in the. Elizabeth River EstuaryV
I/ R.J. Huggett, Virginia Institute of Marine Science
-------
Both the Annapolis and Great Lakes studies indicated, however,
that the concentration is much higher in the raicrolayer and
the Agency is concerned about risks that this contamination
may pose.
C. Risk Summary
After extensive evaluation of published reviews,
consultation with various Federal and State laboratories, and
review of EPA data files, EPA has concluded that tributyltin
(TBT) in antifouling paints may be a potential hazard to nontarget
aquatic organisms in areas of high boat traffic, marinas, and
estuaries. The toxicity and threat of TBT exposure to aquatic
organisms satisfies the existing risk criteria (40 CFR 162.il)
and the new risk criteria (50 FR 49003) for acute and chronic
hazards to nontarget aquatic organisms as defined earlier in this
chapter. A summary of aquatic toxicity values is presented as
follows:
1) Molluscs: Acute LCso = °*1 to 2'3 PPb
Chronic effects: 0.06 to 0.24 ppb
Bioaccumulation: 2000- to 11,000-fold;
very slow depuration.
2) Fish: Acute LC5Q = 0.96 to 24.0 ppb
Chronic effects: 0.2 to 10.0 ppb
Bioaccumulation: 2120- to 4580-fold; rapid
depuration.
3) Crustaceans: Acute LCso = 0.3 to 41.0 ppb
Chronic effects: 1.0 ppb
Bioaccumulation: 4400-fold; greater
accumulation from food than from water
4) Algae: Acute LCso = 0.33 to 1.03 ppb
Bioaccumulation: 8000- to 30,000-fold;
toxic in some species, depuration in
others.
Environmental concentrations of tributyltin are listed in
Table 3. Several locations appear to have tributyltin concen-
trations equal to, or greater than, toxicity values for nontarget
aquatic organisms. The following conclusions may be made regarding
toxicity and exposure at some of the locations:
1) Annapolis:
tributyltin concentrations of .034
to .071 ppb may cause acute mollusc,
and chronic mollusc effects.
11-20
-------
2) San Diego Bay: tributyltin concentrations of
.01 to .93 ppb may cause acute
and chronic effects in several
aquatic taxa (i.e., fish, mollusc,
crustaceans, algae).
3) Lake Superior: tributyltin concentrations of .02
ppb may cause chronic mollusc
effects.
4) Lake Ontario: tributyltin concentrations of .05
to .84 ppb may cause acute and
chronic effects in several aquatic
taxa (i.e., fish, mollusc, crusta-
ceans, algae).
5) Norfolk, VA: tributyltin concentrations of .006
to .06 ppb may cause chronic mollusc
effects.
EPA is concerned about the acute and chronic toxicity
potential of tributyltin compounds to nontarget aquatic
organisms. Water samples have been found to contain TBT
levels that may have direct affects on aquatic organism popu-
lations (molluscs). The TBT compounds may bioaccumulate in
aquatic biota and may pose a hazard to the food chain as they
are passed from lower to higher trophic levels. Adsorption
of tributyltin compounds to sediment may have long-term toxicity
effects on benthic browsing organisms (crustaceans, snails,
etc.). Contamination of estuarine areas at sublethal concen-
trations can influence fecundity of several aquatic taxa from
fish to zooplankton, thus influencing population dynamics.
The present use of tributyltin in antifouling paints presents
a potential hazard to nontarget aquatic organisms.
The tributyltin compounds are acutely and chronically
toxic to molluscs at low levels (0.06 to 2.3 ppb) depending
upon molluscs species. A correlation between environmental
concentrations of tributyltin and declining populations of
nontarget organisms has been demonstrated in Europe through
the works of Waldock and Thain, Beaumont, and Alzieu. Laboratory
toxicity testing,, environmental monitoring, and bioaccumulation
studies have corroborated the conclusion that tributyltin
antifouling paints may be responsible for the decline of several
mollusc populations.
Based on these findings, Great Britain and France
have regulated or curtailed the use of tributyltins in antifouling
paints. Effective January 1, 1986 Great Britain is banning:
a) copolymer formulations containing more that 7.5% organotin
(measured as tin in the dry paint film) and b) those paints
s
3°
11-21 ^
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based on copper or other antifouling systems containing more
than 2.5% organotin (measured in the same way). In effect (b)
will ban the supply of existing "free association" paints while
allowing the minimum use of tributyltin compounds as a performance
booster in other antifouling systems Great Britain will review
these levels in time for the 1987 painting season with a view
to reducing them in line with advances in paint technology. In
addition, the British government proposes to establish an
ambient water quality target for organotin concentrations.
France has recently extended its ban another 2 years
on use of organotin paints for all boats less than 25 meters in
length. The French experience shows that a ban on the use of
TBT on pleasure craft can be highly effective. In 1982 the
industry producing organotin compounds measured concentrations
in Arcachon Bay and found levels 3 times higher than those
known to cause malformation in Pacific Oysters. Since the
implementation of the first ban (1983 to 1985), the recovery
of oysters has been carefully monitored. In the Arcachon Bay
in 1980 and 1981, C.gigas were very badly affected. Within
some areas, 95-100% of the two year old oysters showed
deformation of the shells. In 1982, the first effective
year of the ban, the incidence of shell deformation was down
to 70-80% and in 1983 to 45-50%. Even more important has
been the reduction in number of oysters from the same areas
showing deformities in both upper and lower shells. This
was between 70 and 90% in 1980 and 1981 but zero in 1983.
A similar recovery has occurred with spatfall; in 1980 and
1981 there was none, but in 1982 it was good and in 1983
it was excellent (Vosser 1985).
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III.
BENEFITS
trih .The.A9encY will perform a benefits analysis for the
Qiim • during the Special Review. The following information
summarizes available information on the usage of tributyltin
antifoulant paints.
A* Antifoulant Paint Use Pattern
Antifouling paints containing TBT or copper compounds
are applied primarily to vessel hulls to control the growth of
rouiing organisms. The paints are also used to control fouling
organisms on docks, buoys and other marine structures. Fouling
is caused by the attachment of marine organisms to surfaces that
are submerged or in contact with fresh or salt water. Species
which cause fouling include algae, bacteria, barnacles, tubeworms,
nydroids, and sponges. These organisms increase hull friction
and weight which reduces speed and increases fuel consumption.
In addition, fouling may cause deterioration to the hull coatings,
possibly resulting in corrosion.
Antifouling paints containing tributyltin(s) are registered
for use on wood, fiberglass, aluminum, steel, and cement hulls.
These paints are applied to pleasure crafts, commercial vessels,
and military ships. The U.S. Navy, the major domestic user of
antifouling paints, is considering a conversion from cuprous oxide
to a combination of tributyltin compounds and cuprous oxide in
its antifouling paints. The Navy has proposed to use a copolymer
paint with very low leach levels to minimize the the environmental
loading of tributyltins.
The U.S. Navy is planning to replace the copper-based
paints it is currently using on its steelhulled vessels with
copolymer antifouling paints containing tributyltin and copper
compounds. Five to twenty percent of the fleet would be treated
annually with full replacement anticipated by 1991 at the earliest.
A maximum annual increase of 100 vessels would be treated with an
average of 900 pounds of tributyltin per vessel, constituting an
additional use of approximately 90,000 pounds of tributyltin
active ingredient per year (U.S. Naval Sea Systems Command 1984).
B. Tributyltin Antifoulant Paint Registrations
As earlier indicated, nine tributyltin compounds are
registered for use in antifouling paints. The TBT antifoulant
paints are formulated as single active ingredient formulations,
as multiple TBT formulations, as any one of the TBT's in combi-
nation with copper-based compounds (usually cuprous oxide),
and as multiple TBT's plus copper-based compound formulations.
-------
There are approximately 340 federally registered anti-
fouling paints containing tributyltin active ingredients. Review
of these registrations indicates that the most frequently registered
tributyltins are bis(tributyltin) oxide (161 registrations),
tributyltin fluoride (141 registrations), and tributyltin metha-
crylate (52 registrations). The 152 single active ingredient
formulations generally range between 5 and 20 percent active
ingredient. In formulations with two or more tributyltin
compounds, active ingredients generally range from 6 to 13
percent. In formulations with tributyltins and copper compounds,
tributyltins range from less than 1 to 20 percent. The number
of free association paint formulations as compared to the copolymer
paint formulations is not known at this time.
C. Usage of Tributlytin Antifoulant Paints and Alternatives
Current annual domestic usage of TBT pesticides for all
uses including industrial processing water, nonindustrial
processing water, wood preservatives, and antifouling paints,
is estimated at approximately 730,000 to 860,000 pounds of active
ingredients. Current domestic usage of tributyltins in antifouling
paints ranges between 250,000 to 300,000 pounds active ingredient
annually. Bis(tributyltin) oxide, accounts for 75,000 to 100,000
pounds used annually, or approximately one-third the tributyltin
used as an antifoulant. Estimated annual antifoulant usage is
100,000 to 125,000 pounds of tributyltin methacrylate, 60,000
to 70,000 of tributyltin fluoride, 7,500 to 15,000 pounds of
bis(tributyltin) adipate, and 5,000 to 10,000 pounds of
tributyltin acetate. Tributyltin acrylate and tributyltin
resinate annual usage are quite low, on the order of a few
hundred pounds each. There appears to be no recent usage of
bis(tributyltin) dodecyl succinate, and bis(tributyltin) sulfide.
Many TBT antifoulant paints contain copper, or copper
containing compounds, and cuprous oxide is still the main alter-
native to tributyltin in paint formulations. Other copper
compounds, such as metallic copper, are also registered for use.
Copper compounds are effective against the same antifouling
organisms as the tributyltins; however, they tend to be corrosive
to metal, especially aluminum. An insulative coating is recommended
on steel hulls prior to copper-based antifoulant paint application.
Label recommendations generally do not recommend copper-containing
paints for aluminum boat hulls.
Depending upon the type of paint and whether there is
copper or tributyltin biocides in the formulation, the antifouling
compound may be leached from the paint, activated by periodical
scrubbing of the outer paint layer, or exposed by gradual erosion
of the paint as the vessel moves through the water (ablative
process). The ablative process is the newest antifouling system
in which the pesticide is part of the paint polymer. As the
III-2
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vessel moves through the water, the outer paint layer is removed
and a new layer of the antifouling paint is activated. The
advantage of ablative paints is that they eliminate the requirement
r scrubbing the underwater hull surface. Tributyltin paints
are n°fc corrosive to metal such as aluminum and eliminate the
need for a protective coating between the metal and the antifouling
paint, except when copper compounds are included in the paint
lormulation. Tributyltins also provide longer protection against
antifoulrng organisms than the more commonly used cuprous oxide
compounds, thus reducing a ship's drydock time.
D. Benefits of TBT Usage
Sufficient data are currently unavailable to the Agency
to determine the use patterns and possible cost savings attri-
butable to current and planned applications of TBT antifouling
paints on commercial, recreational, and nonnaval military vessels.
The U.S. Navy Environmental Assessment stated that the
conversion from nonablative copper-based paints to ablative
tributyltin paints will result in fuel savings, elimination of
underwater hull cleaning, and increased operational readiness.
The U.S. Navy estimated that use of tributylin paints would
result in a 15 percent savings in fuel consumption, amounting
to an annual savings of $150 million once the entire fleet is
treated with these paints. Eliminating the need for underwater
hull cleaning between maintenance overhauls would save an
estimated $5 million annually. Increased operational readiness,
which is not amenable to quantification, relates to less time
in port, longer range, and greater speed (U.S. Naval Sea Systems
Command 1984).
III-3
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IV* OTHER REGULATORY CONSIDERATIONS
A* Expansion of Special Review
Tne Special Review of bis(tributyltin) oxide, bis
adiPate, bis(tributyltin) dodecenyl succinate,
srr* n) sulfide' tributyltin acetate, tributyltin
^•h ^- ?'• butyltin fl°uride, tributyltin methacrylate, and
crioutyitin resinate is being initiated based on acute and
cnronic toxicity to nontarget aquatic organisms. The focus of
tne review, at this time, is on the use of these compounds as
antitouiant paints. However, if information evaluated during
tne special Review indicates that the use of these compounds on
other sites (including but not limited to cooling towers,
textiles, etc.), results in exposure to nontarget aquatic
organisms, or that any other criteria are met or exceeded, the
Special Review may be expanded to include those pesticidal uses
as well. Additionally, because most tributyltins pose similar
toxicity to nontarget aquatic organisms, and several tributyltin
compounds, in addition to the nine compounds under Special Review,
are registered for sites which may result in exposure to nontarget
aquatic organisms, the Special Review may be expanded to include
a much larger subset of the tributyltin compounds than the
original nine. These additional chemicals include:
Tributyltin Compounds
Code No. Chemical
083102 Bis(tributyltin) salicylate
083103 Bis(tributyltin) succinate
083104 Bis(tributyltin) sulfosalicylate
083106 Tributyltin benzoate
-083107 Tributyltin chloride
083108 Tributyltin chloride complex of
ethylene oxide condensate of
abietylamine
083109 Tributyltin linoleate
083110 Tributyltin monopropylene glycol
malate
083111 Tributyltin neodecanoate
083115 Tributyltin isopropyl succinate
083118 Tributyltin maleate
At this time the Special Review is based on chronic and
acute toxicity to nontarget aquatic organisms; however, the
Agency is also concerned about the toxicity of these compounds
to humans.
IV-1
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The animal toxicity data base to assess potential human
toxicity is highly deficient for all TBT compounds under review
(Doherty Memo Dec. 11, 1985) although there are some useful
studies particularly with tributyltin oxide. The available
information (obtained mostly with tributyltin oxide) indicates
concerns over immunotoxicity, teratogenicity, dermal toxicity,
inhalation toxicity, and endocine effects. The Agency cannot
evaluate any human risks associated with the use of TBT compounds
at this tjLme both because the effects are not adequately studied
and because we have no reliable estimates of exposure either
through the food chain (e.g. oysters) or directly through use
(e.g. applicators). Should new information enable the Agency
to identify a potential human health trigger, the Special Review
may be expanded to include such risks.
The Agency is also concerned that the use of TBT
pesticidal products may adversely affect one or more endangered
species. If information is obtained which supports this concern,
the Special Review may be expanded to include consideration of
these hazards.
B. Data Call-In Notices
The Agency also intends to issue Data Call-in Notices
under the authority of section 3(c)(2)(B) of FIFRA. This section
of FIFRA provides the Administrator with the authority to require
that information be provided to the Agency, which is determined
necessary to support the continued registration of a pesticide
product. It also provides the authority to set specific timeframes
for conducting the required studies and providing the data to the
Agency. The Agency may issue a notice of intent to suspend
registrations of affected products if registrants fail to comply
with the requirements of the notices.
Data Call-in Notices are being developed requiring data
for the nine tributyltin compounds under Special Review. Data
required will include, at a minimum, leaching rate data by
paint formulation, acute and chronic bioassay studies, bio-
accumulation and biomagnification data, analytical methodology,
environmental transport data, environmental monitoring data,
and monitoring of exposure to workers applying and removing
paints, as well as data quantifying TBT residues in fish and
shellfish, and the volume of active ingredient used on the various
sites for which these products are registered. Additionally, the
Agency will conduct a comprehensive review of the data needed to
support registrations of other tributyltin pesticidal active
ingredients and may issue additional Data Call-in Notices concerning
other tributyltin compounds.
IV-2
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