A study of the priority substances of the Water Framework Directive ...

..:::::::::: tributyltin compounds
..:::72
30 Tributyltin compounds
� Tributyltin compounds (TBT) are mainly
used for anti fouling on ships.
� TBTs cause imposex in snails.
� In Norway triphenyltin (TPhT) is monitored
alongside with TBT.
� Levels in the environment do not decrease
substantially, and TBT monitoring should continue.
Production and use
TBTs have not been produced in Norway, but
they have to a large extent been used for anti
fouling and wood preservation. There has been
minor use in paint, disinfectants and detergents.
The use of TBT and triphenyltin compounds
(TPhT) is regulated. New use has been banned
since 1990 on smaller boats and new use
(import, export, production sales etc) is banned
from 2003. All TBT anti fouling on ships is
banned from 2008.
Emissions, discharges,
distribution and hot-spots
Norwegian emissions of TBT have dropped
from 58 tons in 1985 via 29 tons in 1995 to
about 7 tons in 2003.
Discharges to water were estimated to be 25
tons in 1995 dropping to 15 tons in 2002, most
discharges are considered to be to water as discharges
are mainly from marinas and shipyards,
but TBT may also leak from other products, or
be released from plastics or wood. TBT wood
preservatives are not included in the emission
estimates, but the tonnage is not large. Removal
of old anti fouling in marinas may cause new
discharges.
Monitoring
Monitoring of TBT has been part JAMP and
time trends exist here. TBT has also been investigated
in several other studies (see references).
Marine sediment
Levels of TBT in marine sediments are very high
in many fjords, harbours and shipyards.
Marine biota
Shellfish in harbours are highly contaminated all
along the coast. Imposex is shown in half the
A study of the priority substances of the Water Framework Directive
TA-2140/2005
FACTS
Cas no.: 56-35-9
Synonyms: TBT, Tributyltin oxide (TBTO), tributyltin fluoride
(TBTF), biomet, butinox, C-Sn-9.
Properties:
Toxic effects: TBT is toxic to humans and very toxic to
marine organisms. TBT also causes imposex in snails.
Log Kow: 3,19 - 3,84
Persistence: Half life in water (hydrolysis / volatilisation)
for TBT is 11 months. By photodegradation, half
life is more than 3 months. In water and sediment
half life is 4 - 5 months (aerobic biodegradation) or 1
- 3 months (anaerobic biodegradation) (CIRCA). In
sediment, degradation may take years (HSDB). TBT
compounds accumulate in organisms. BCF in Blue
mussels (Mytilus edulis) is 10500.
Water solubility: 0,1%
Molecular formula: C 24 -H 54- Sn 2
Metabolites: Hydroxy-tributyltin.
investigated female snail population. Costal
areas in Finnmark have lower levels than average.
Fresh water biota
Levels in burbot (Lota lota) liver in six lakes
have been screened; concentrations are not very
high compared to concentration in marine
biota.
Hotspots
Marinas and shipyards are typical hotspots for
TBT.
Need for further screening and monitoring
There is no need for further screening of TBT in
Norway, but the use has been extensive and levels
in the Norwegian marine environment are
stable high and stable. Continued monitoring of
TBT is therefore necessary.
Analysis
Analysis of tributyltin is well developed and
often part of packages with other organotin
compounds.