Fróðskaparrit - 01.01.1998, Blaðsíða 63

ORGANOTIN OG IMPOSEX f STRANDARØKINUM f FØROYUM
69
tons. By 1985 production had increased to
35 000 tons and was estimated to reach
63 000 tons by 1993 (Blunden and Chap-
man, 1986; WHO, 1980).
Applications of organotin compounds
depend on the nature of the alkylsub-
stituents and can be divided in biocidal and
non-biocidal use. Maximum impact on bio-
logical activity occur for triorganotin com-
pounds which are used as biocides in a
number of areas. Among the most toxic
species are tributyl- and triphenyltin com-
pounds (Bryan et al., 1988; Thain et al.,
1987; Hugget et al., 1992). The most im-
portant application of these compounds
from an environmental point of view, are as
the active compound in antifouling paints
used on the hull of ships (Bryan and Gibbs,
1991). Antifouling paints prevent settle-
ment and growth of bamacles, tubeworms,
algae and other marine organisms on ships.
Settlement of such organisms increase the
hydrodynamic drag and reduces fuel effi-
ciency. Triorganotins are also used in wood
protection against fungal and insect attack
and as pesticides in agriculture, but these
sources are not considered as major con-
tributors to environmental pollution (Blun-
denandEvans, 1989).
Diorganotin compounds are used as heat
and UV-stabilisers in PVC-products and as
catalysts in the production of polyurethane
foams. Monoorganotin compounds are also
used as catalysts in industry. Leaching of
inorganic and organic tin compounds from
PVC materials has been observed. The
rapid increase in production and use of
PVC-products and their subsequent dispos-
il may lead to an accumulation in the envi-
ronment (Quevauviller et al., 1991).
Unintended environmental effects from
organotin compounds were first observed
as development of shell anomalies in Pacif-
ic oysters (Crassostrea gigas) in France in
the early 1970s (Alzieu et al., 1986; Ruiz et
al., 1996). Since then, effects have been re-
ported in a number of species including
fish, gastropođs, crustaceans, echinoderms
and microalgae (Fent and Meier, 1994;
Bryan et ai, 1986; Bushong et al., 1990;
Hall, 1988; Beaumont and Newman, 1986).
In recent years, much attention has been
paid to the introduction of male sex charac-
ters in female snails, known as imposex,
mainly observed in neogastropods (Gibbs
et al., 1987; Horiguchi et al., 1994). This
effect is believed to be a widespread phe-
nomenon (Ellis and Pattisina, 1990) and
has in the open North Sea been related to
shipping traffic intensities (Hallers-Tjab-
bes et al., 1994). In some cases local popu-
lations of dogwhelks (Nucella lapillus)
were reduced or disappeared (Bryan et al.,
1986). Most investigations indicate that
tributyltin (TBT) is responsible for the de-
velopment of imposex in snails (Bryan et
al., 1986). Other compounds and situations
have however been reported to induce this
condition on gastropods (Nias et al., 1993).
Bettin et al. (1996) suggested that TBT-in-
duced imposex is caused by an inhibition of
the cytochrome P-450 dependant aro-
matase system leading to an increase in the
androgen (testosterone) level in the female
gastropods.
Harmful effects of organotin compounds
in the environment led to restrictions on the
use of TBT based antifouling agents in a