THE ecological cost of preventing marine life from colonising the bottoms of boats continues to mount. A new herbicide that was widely adopted after paint containing tributyl tin was banned from use on small boats in 1988 is turning up in increasing quantities in the coastal waters of Europe.
Irgarol 1051 is a triazine herbicide manufactured by the Swiss company Ciba Geigy. It is added to a new generation of copper-based antifouling paints used by most owners of small boats. The metal paint controls aquatic animals, while the triazine inhibits the growth of algae on boat hulls.
Biologists are warning that little is known about the toxicity of Irgarol 1051 to other marine organisms, or its behaviour in the environment, but that what is known is worrying.
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Concern has grown in the past year, following the publication of reports of Irgarol 1051 at high concentrations in both the south of France and the coastal waters of southern England. Papers due to be published soon will report findings in the waters of Lake Geneva and Sweden. British researchers say they have also found it in other English estuaries.
James Readman, of the International Atomic Energy Agency鈥檚 marine environment laboratory in Monaco, raised the alarm a year ago when he reported in the journal Environmental Science and Technology that the herbicide was widespread in coastal waters all along the C么te d鈥橝zur. The highest levels, up to 1.7 micrograms per litre, were within 5 kilometres of exclusive yachting marinas at Monaco and Antibes. Readman told New 杏吧原创: 鈥淲e cannot assess the likely environmental damage from this herbicide because there is as yet very little toxicity data.鈥�
Mark Gough, a marine biologist until recently with the National Rivers Authority in Portsmouth, reported in Marine Pollution Bulletin in October that Irgarol was widespread along the south coast of England, from Kent to Hampshire, with concentrations up to 0.6 micrograms per litre near Portsmouth and in the Medway and Hamble estuaries. The Hamble is one of Britain鈥檚 busiest yachting centres, with five marinas.
Gough also found high concentrations in sediments. He described his work as a 鈥減reliminary assessment鈥� and called on the NRA to commission follow-up work. But his unit has since shut and no one is working on the problem any longer.
Fauzi Mantoura of the Plymouth Marine Laboratory has found the chemical in the Tamar, Thames and Mersey estuaries. 鈥淲e know very little about it,鈥� he says. One risk, he says, is that it will inhibit the growth of algae along shorelines, preventing biological communities from establishing themselves.
In the early 1980s, researchers from the Plymouth laboratory were among the first to uncover the unexpected toxicity of TBT, which killed oysters and caused whelks to change sex, even at extremely low concentrations. In one French bay alone the high level of TBT cost the oyster fishery $150 million during the 1980s.
Other, so far unpublished, discoveries of Irgarol 1051 have been made in Switzerland, where Kristin Becker of the Ecole Polytechnique in Lausanne has found it in Lake Geneva, and in Sweden, where Lilian Tornqvist of the National Chemicals Inspectorate has found it around marinas on the west coast near Gothenburg.
An assessment of antifouling products by the pesticides division of the Swedish inspectorate has concluded that the compound tends to accumulate in fish and that it degrades at a 鈥渧ery slow鈥� rate in both freshwater and seawater. It is likely to accumulate in water and sediments.
Ciba-Geigy said this week that its own investigations have shown 鈥渘o effects [in fish] at or below 6 micrograms per litre鈥� and that 鈥渟ignificant environmental side effects are not expected as long as the concentration of Irgarol 1051 in the seawater is below this figure鈥�.
Ecologists do not question Ciba鈥檚 toxicological data, but say it does not answer the basic questions about the compound鈥檚 impact on ecosystems. Readman says: 鈥淰ery little [toxicological] information on the compound is available.鈥� Current data from the manufacturer relate to acute toxicity, he says, but there is 鈥渘o information relating to sublethal effects鈥�. Gough fears changes to plankton brought on by stress which 鈥渃ould possibly induce subsequent ecological changes鈥�.