Kortlægning og vurdering af antibegroningsmidler
til lystbåde i Danmark

Summary

The monitoring data for tributyltin (TBT) in Danish harbours for pleasure craft are relatively old, and no analyses have been made after the ban of the use of TBT for pleasure craft was effected in 1991. Analyses of samples collected before the regulation show TBT concentrations in the water from below 0.1 to 0.9µgTBT/l. Higher concentrations of TBT have been found in marine sediments as concentrations between 30 and 4950 g TBT/kg dry weight have been measured in Danish marine areas.

Analyses of Diuron in Århus County have shown concentrations of up to 1.07 g/l in the peak season. Diuron was measured at 0.028 g/l at a distance of 500 metres outside a harbour in which the concentration of Diuron in the harbour itself was up to 0.83 ) g/l. Irgarol was monitored in the same series of analyses, and the combined impact of the two herbicides in the harbours ranged between 0.092 and 1.37 g/l. The sum of the concentrations of the herbicides was 0.041 g/l at a distance of 500 meters outside a harbour.

Danish analyses of total copper have shown concentrations at approx. 1 g/l in freshwater and seawater while 0.l to 87 mg/kg dry weight have been seen in sediment from the North Sea at the Danish/German west coast.

Irgarol has been analysed in samples from Danish harbours which were collected in 1996. Considerable amounts of Irgarol have been detected in the water in which Irgarol was present in concentrations of up to 2.3 g/l. Recent measurements of Irgarol in Danish marine sediments have shown typical concentrations between 10 and 25 g/kg dry weight in harbours for pleasure craft.

There are no available data on concentrations of Sea-Nine and zinkpyrithione in the environment.

Relevant information for an environmental and health hazard assessment of the antifoulants is presented in Tables A and B.

Table A
Health classification and environmental properties

1: Primary degradation means that the chemical is transformed into more or less stable degradation products. Ultimate degradation (mineralisation) means that the chemical is degraded to harmless compounds as e.a. carbon dioxide, water and biomass.
2: t½ is the estimated half-life for aerobic degradation.
3: Irgarol and Sea-Nine have been classified in the present study.
 

Table B
Measured concentrations of antifoulants in the environment and proposals for quality criteria

1 : Samples were collected outside harbours and in marine coastal areas.
2: Criterion based on 20% dry weight content in sediments (EU 1997).
3: Criteria from other countries than Denmark.
 

The antifoulants assessed here are all potentially harmful to humans as indicated by the risk phrases in Table A. The antifoulants are also highly toxic to organisms living in aquatic environments. TBT, Diuron and Irgarol are poorly degradable (Table A) and the concentrations of these chemicals, which have been observed in water and sediment samples, are of considerable environmental concern. The potential environmental risk related to the other antifoulants is less clear on the basis of the available data. The toxic cobbler may be more or less inactivated in the environment when the copper is released from the antifouling paint. The biodegradation of Sea-Nine and zinkpyrithione, including the effect of degradation on aquatic toxicity, has not been sufficiently evaluated in this study.

Mechanical cleaning technologies are the most obvious alternatives to biocide based antifouling paints as attempts to develop biocide-free antifouling paints have not yet been successful. Today, the development of mechanical cleaning technologies has only just started and the practical implementation of such methods in Denmark is very limited. However, the methods that are being developed now (especially in Sweden) will probably reach an applicability within a few years that will be sufficient to meet the need for a biocide-free antifouling technology.