The
use of the antifouling agent tributyltin (TBT),
which was previously used in ship paints, has
been banned for pleasure craft since 1991 after
serious effects were found in oysters. The shipping
industry has since been looking for new antifouling
agents, especially because of the EU ban on TBT
for commercial ships from 2008. One of the new
agents is zinc pyrithione (ZPT) which is known
as an active ingredient in dandruff shampoo and
cosmetics. ZPT is being marketed together with
the chemically related agent copper pyrithione
(CPT) as easily degradable and light-sensitive,
and they are both already fairly widely used in
Scandinavia.
Researchers at the National
Environmental Research Institute of Denmark (NERI)
have shown that ZPT in the marine environment
is quickly converted to CPT, which is both more
stable and more toxic than ZPT. Tests showed that
up to 50 per cent of the added ZPT was converted
into CPT, and that both substances turned out
to be much more stable under the natural light
conditions in water than expected.
The researchers' tests also
showed that ZPT may harm bacteria, algae and small
animals both in the water and on the seabed in
the marine environment, even at very low concentrations
and brief exposure.
Analysis, fate and toxicity
of Zink- and copper pyrithione in the marine environment.
I. Dahllöf et al. TemaNord 2005:550
http://www.norden.org/pub/miljo/miljo/sk/TN2005550.pdf
Hjorth, M., Dahllöf, I.
& Forbes, V.E. 2006: Effects of the function
of three trophic levels in marine plankton communities
under stress from the antifouling compound zinc
pyrithione. - Aquatic Toxicology 77: 105-115.
Grunnett, K.S. & Dahllöf,
I. 2005: Environmental fate of the antifouling
compound zinc pyrithione in seawater. - Environmental
Toxicology and Chemistry 24(12): 3001-3006.
Maraldo, K. & Dahllöf,
I. 2004: Indirect estimation of degradation time
for zinc pyrithione and copper pyrithione in seawater.
- Marine Pollution Bulletin 48: 894-901.
Maraldo, K. & Dahllöf,
I. 2004: Seasonal variations in the effect of
zinc pyrithione and copper pyrithione on pelagic
phytoplankton communities. - Aquatic Toxicology
69: 189-198.
Petersen, D.G., Dahllöf,
I. & Nielsen, L.P. 2004: Effects of zinc pyrithione
and copper pyrithione on microbial community function
and structure in sediments. - Environmental Toxicology
and Chemistry 23(4): 921-928.
