This document provides information about tributyltin (TBT) compounds, specifically tributyltin oxide (TBTO). It discusses that TBTO is a common organotin compound used as a biocide in antifouling paints for boats. While an effective biocide, concerns about its toxicity and bioaccumulation in food chains have led to increased regulations and bans on its use. TBTO is toxic to aquatic organisms and high levels of exposure in humans can cause skin, eye and respiratory irritation along with organ damage. Most regulations on TBTO arose from cases of sexual abnormalities in snail species and now aim to decrease its use in antifouling paints.

1.
Pollutants'
Chemistry
Tributyltin
compounds
Joel
Emmanuel
Bortoni-­‐González
June
11th,
2013

2. Introduction
Tributyltin
(TBT),
(C4H9)3Sn,
is
a
chemical
used
mostly
in
biocides
in
the
form
of
other
compounds
like
tributyltin
hydride,
(C4H9)3SnH,
and
tributyltin
oxide,
C24H54OSn2,
due
to
the
fact
that
TBT
by
itself
is
unstable
and
will
break
down
unless
combined.
It
is
part
of
the
aromatic
hydrocarbon
chemical
family.
These
types
of
hydrocarbons
have
alternating
double
and
single
bonds
between
carbon
atoms
forming
rings,
like
benzene
in
Figure
1.
The
term
aromatic
has
nothing
to
do
with
the
physical
property
of
aromaticity,
a
chemical
property
that
describes
the
way
in
which
a
conjugated
ring
of
unsaturated
bonds,
lone
pairs
or
empty
orbitals
exhibit
a
stabilization
stronger
than
would
be
expected
by
the
stabilization
of
conjugation
alone,
but
rather
to
the
fact
that
these
chemical
compounds
have
a
scent,
sweet
in
most
cases.
Figure
1.
Benzene
model
where
the
circle
denotes
the
alternating
double
and
single
bonds
between
carbon
atoms.
The
most
common
TBT
compound
is
the
tributyltin
oxide
(TBTO)
and
has
been
the
subject
of
most
TBT
tests.
This
compound
and
other
eight
TBT
compounds
are
referred
to
as
organotins.
Characteristics
TBT
compounds
are
liquids
often
colorless,
unlike
TBTO
that
tends
to
have
a
slightly
yellow
color,
and
have
an
odor
similar
to
gasoline.
TBTO
is
insoluble
in
water
due
to
the
fact
that
they
react,
but
is
soluble
in
hexane
and
most
organic
solvents
(ethanol,
ether,
halogenated
hydrocarbons,
etcetera)
and
is
flammable
but
does
not
form
explosive
mixtures
with
air.
Its
melting
point
is
located
around
53ºC
and
its
boiling
point
around
193ºC
and
it
has
a
density
of
1.103
g/ml
at
20ºC.
It
breaks
down
slowly
in
the
presence
of
oxygen,
light
or
heat.
Prominent
uses
TBTO
is
an
effective
biocidal
preservative
for
wood,
cotton
textiles,
paper
and
paints
and
stains
for
residential
homes.
Mainly,
it
is
added
as
an
antifouling
agent
in
numerous
formulations
of
marine
paints
and
boat
hulls,
docks,
fishnets
and
buoys
to
discourage
the
growth
of
marine
organisms
such
as
barnacles,
bacteria,
tubeworms,
mussels
and
algae.

3. Quality
regulations
Most
of
the
international
regulations
on
TBTO
derived
from
previous
cases
of
imposex
on
several
snail
species
in
France
and
Great
Britain.
Nowadays
regulations
tend
to
decrease
the
use
of
TBT
based
antifoulings.
In
1987
a
Europe-­‐wide
ban
of
its
use
on
boats
of
under
25
meters
long
was
established.
In
the
United
Kingdom
the
use
of
TBT
based
paints
continues
on
larger
vessels
and
it
remains
at
present
the
most
effective
means
of
controlling
fouling.
In
November
1998
the
International
Maritime
Organization
made
the
decision
to
introduce
a
worldwide
ban
of
the
use
of
TBT
in
antifouling
paints
for
most
ships
from
January
2003,
a
ban
that
has
been
in
place
for
several
years
mainly
in
countries
with
a
lot
of
maritime
activity,
such
as
Japan.
Pressure
for
a
complete
ban
of
TBT
in
antifouling
paints
has
been
increasing
due
to
evidence
that
it
is
bio-­‐accumulating
in
food
chains,
with
particularly
high
levels
being
found
in
marine
mammals.
Toxicity
Since
TBTO
is
used
mostly
on
products
that
will
be
in
touch
with
water
studies
of
the
effects
of
TBTO
products
on
living
organisms
have
been
primarily
performed
on
aquatic
life.
Effects
of
TBT
products
on
humans
are
not
clear,
but
several
incidents
of
human
exposure
to
the
biocide
have
been
reported:
underwear
treated
with
TBT
has
caused
severe
skin
irritation
to
its
wearer,
shipyard
workers
exposed
to
TBT
dust
and
vapors
developed
breathing
problems,
irritated
skin,
headaches,
colds,
flu,
fatigue
dizziness
and
stomach
ache.
TBT
exposure
can
also
irritate
the
eye
and
mucous
membranes
and
prolonged
exposure
may
cause
liver
and
kidney
damage.
M
&
T
Chemicals,
one
of
the
main
producers
of
TBTO,
claim
that
workers
exposed
to
this
substance
metabolize
it
within
3
days.
Single
exposure
of
TBTO
on
rats
demonstrated
a
transient
increase
in
adrenal
weight
shortly
after
exposure
and
a
transient
effect
on
thyroid
follicles;
these
effects
are
reversible.
Inhalation
studies
of
a
single
4
hours
exposure
of
rats
to
aerosols
of
TBTO
showed
irritation
and
enteritis.
Studies
where
10
male
and
10
female
rats
were
exposed
to
saturated
gases
of
TBTO
didn't
show
any
death
occurring
during
exposure
for
7
hours
or
in
the
following
14
days
observation
period.
Short
term
exposure
of
TBTO
on
10
male
and
10
female
rats
involving
repeated
inhalation
in
"nose
only"
chambers
during
4
hours
5
days
per
week
produced
sever
toxic
effects,
inflammatory
reactions
in
the
total
respiratory
tract
and
histological
changes
in
the
lymphatic
organs
were
observed;
5
males
and
6
females
died
during
this
study.
In
mammals,
high
levels
of
TBTO
can
affect
the
endocrine
glands,
upsetting
the
hormone
levels
in
the
pituitary,
gonad
and
thyroid
glands.
Large
doses
of
TBT
have
been
shown
to
damage
the
reproductive
and
central
nervous
systems,
bone
structure
and
the
gastrointestinal
track
of
mammals.
A
large
number
of
studies
have
been
conducted
showing
that
TBTO
causes
depression
of
immune
functions
dependant
on
the
thymus.
These
effects
occur
at
doses
lower
than
those
that
cause
other
toxicity;
the
critical
effect
for
TBTO
is
immunotoxicity.

4. Cancer
assessment
has
been
conducted
in
rats
and
mice
following
oral
exposure.
Increases
in
benign
pituitary
tumors,
in
pheochromocytomas
and
in
parathyroid
tumors
at
the
highest
dose
tested
were
shown.
It
is
unclear
if
TBTO
is
responsible
for
these
tumors
since
the
strain
of
rats
used
they
normally
occur
with
variable
incidence.
The
mice
didn't
show
any
sign
of
a
tumor
due
to
TBTO.
Eco
toxicity
Much
of
the
concern
of
the
use
of
tributyltin
stems
from
its
use
as
a
marine
antifoulent
in
paints.
This
compound
is
slowly
released
from
the
paint
on
the
hull
of
the
boat
into
the
adjoining
water
hindering
the
growth
and
attachment
of
a
variety
of
organisms
to
the
boat.
Consequently,
tributyltin
concentrations
in
harbors
and
bays
in
Great
Britain,
France
and
the
United
States
were
high
enough
to
significantly
affect
oyster
and
mussel
production.
Imposex,
the
development
of
male
characteristics
in
females,
has
been
initiated
by
TBT
exposure
in
several
snail
species.
In
laboratory
tests,
reproduction
was
inhibited
when
female
snails
exposed
to
50
ppt
of
TBT
developed
male
characteristics,
such
as
male
genitalia.
Imposex
was
also
noted
in
the
mud
snail
at
less
that
3
ppt
of
TBT.
TBT
is
extremely
toxic
to
crustaceans.
Lobster
larvae
show
a
nearly
complete
decrease
in
growth
at
just
1
ppb
of
TBT.
Molluscs,
used
as
indicators
of
TBT
pollution
because
of
their
high
sensitivity
to
those
chemicals,
react
adversely
to
very
low
levels
of
TBT
(0.06-­‐2.3
ppb
of
TBT).
They
release
TBT
very
slowly
from
their
bodies
after
it
has
been
absorbed.
TBT
toxicity
in
the
field
may
be
substantially
underestimated
in
laboratory
studies.
TBT
binds
to
the
sides
of
containers
and
plankton,
which
contributes
to
this
underestimation
of
its
potential
toxicity.
Generally,
the
larvae
of
any
tested
species
are
more
sensitive
of
tributyltin
exposure
than
the
adults.
Some
fish
can
degrade
TBT
due
to
special
enzymes
that
these
fishes
contain.
In
the
Chinook
salmon,
once
absorbed
it
breaks
down
into
di-­‐n-­‐butyltin
(DBT).
Rainbow
trout
eggs
are
killed
between
10-­‐12
days
of
TBT
exposure
at
5
ppb.
At
lower
levels
no
deaths
occurred,
but
blood
and
liver
metabolism
changes
were
noticed.
Growth
reduction
and
liver
changes
also
occurred
in
young
trout
exposed
to
lower
levels
of
tributyltin
chloride.
Also,
after
seven
days
of
low
level
TBTO,
the
corneal
membranes
of
the
rainbow
trout's
eyes
were
destroyed.
TBTO
has
been
shown
to
inhibit
cell
survival
of
marine
unicellular
algae
at
very
low
concentrations.
Pollution
in
Arcachon
Bay
and
beginning
of
the
ban
on
its
use
Until
the
mid
1970's,
Arcachon
Bay
had
been
an
important
area
for
oyster
culture,
with
production
of
10,000-­‐15,000
tons
per
year,
covering
substantial
areas
of
the
tidal
mud
flats.
The
bay
was
also
popular
with
leisure
craft,
with
vessels
numbers
increasing
from
7,500
in
the
mid
1970's
to
15,000
at
the
start
of
the
1980's.
Estimated
inputs
of
TBT
to
the
bay
peaked
at
around
8
kg
per
day.
Imposex
was
first
observed
in
the
bay
in
1970,
affecting
the
predator
oyster
drill,
leading
rapidly
to
its
near
extirpation
from
the
bay.
TBT
was
identified
as
the
responsible
agent
only
in
the
early
1980's.

5. Had
the
adverse
effects
been
limited
to
the
loss
of
this
species,
considered
a
pest
within
the
shellfish
industry
for
its
damage
of
oyster
stocks,
little
if
any
action
may
have
followed.
However,
this
early
warning
was
followed
by
failure
of
the
oyster
stocks
themselves.
Despite
a
normal
spawning
event
in
the
summer
of
1976,
few
of
the
larvae
survived.
Larval
settlement
largely
failed
through
the
late
1970's
and
into
the
1980's,
resulting
in
massive
financial
losses
by
the
shellfish
industry.
By
1981,
oyster
production
had
fallen
to
only
3,000
tons.
In
addition
to
reproductive
failure,
adult
oysters
were
rendered
unsaleable
by
shell
deformation
leading,
in
sever
cases,
to
ball
shaped
specimens.
Such
observations
predated
analytical
techniques
sensitive
enough
to
describe
in
detail
environmental
distributions
of
TBT.
In
1986
the
first
survey
of
organotins
in
the
waters
of
Archon
Bay
was
provided,
while
sediments
data
were
not
available
until
the
1990's.
Nevertheless,
the
severity
of
impacts
on
the
ecology
of
Archon
Bay,
manifest
in
heavy
financial
losses,
was
sufficient
to
stimulate
relatively
swift
action
by
the
French
government.
Acting
on
the
best
information
available
linking
the
oyster
collapse
to
the
presence
of
TBT
paints
to
small
vessels
(less
than
25
meters
long)
in
1982,
beginning
the
ban
on
said
boats.
These
controls
undoubtedly
markedly
reduced
TBT
inputs
to
marinas
throughout
France.
In
the
case
of
Arcachon,
implementation
was
probably
aided
by
the
local
provenance
of
many
boat
owners
and
their
interest
in
preserving
a
local
industry.
Sources
Concise
International
Chemical
Assessment
Document
14:
Tributyltin
Oxide.
-­‐
Dr.
Robert
Benson;
World
Health
Organization.
Tributyltin.
-­‐
Extension
Toxicology
Network.
Retrieved
from:
http://pmep.cce.cornell.edu/profiles/extoxnet/pyrethrins-­‐ziram/tributyltin-­‐
ext.html
Tributyltin
(TBT)
antifoulants:
a
tale
of
ships,
snails
and
imposex.
-­‐
David
Santillo,
Paul
Johnston
and
William
J.
Langston.
Tributyltin
pollution
on
a
global
scale.
An
overview
of
relevant
and
recent
search:
impacts
and
issues.
-­‐
Dr.
Simon
Walmsley;
World
Wildlife
Fund.