Inputs, Monitoring and Fate Modelling of Antifouling Biocides in UK Estuaries

The use of antifouling paints containing tributyltin as a biocide is now limited to vessels greater than 25 m in length. Consequently, manufacturers have introduced additional biocides which are generally used in combination with copper. These biocides are termed booster biocides, and currently there are nine approved for use on leisure craft. The environmental impact of tribuyltin and copper on the environment is well documented. However the potential for the other biocides to cause pollution has not been quantified. A survey was therefore performed to determine the quantity of each of the biocides released to coastal waters. Copper(I) oxide was used in highest quantities followed by diuron, copper thiocyanate, Irgarol 1051, zinc pyrithione and dichlofluanid. Monitoring studies agreed with the survey, concentrations of copper being highest followed by diuron and irgarol. High concentrations of zinc were also observed, probably arising from sacrificial anodes. Generally, predictions of biocide concentrations, obtained using an existing exposure model, were similar to measured concentrations, indicating that this model is a useful screening tool for risk assessment purposes.