Boxall et al (1998) identified nine booster biocides approved for use in amateur and professional antifouling products, namely:

• zinc pyrithion;
• TCMTB (2-thiocyanomethyl-benzothiazole);
• kathon 5287;
• TCMS pyridine (2,3,5,6-tetrachloro-4-sulfuronyl pyridine);
• irgarol 1051;
• diuron;
• dichlofluanid;
• chlorthanonil, and
• zineb

Based on a consideration of their use on pleasure craft in UK coastal water, Boxall et al (1998) estimated that copper (1) oxide is used in the highest quantities, followed by diuron, copper thiocyanate, irgarol 1051, zinc pyrithion and dichlofluanid.

There are four main ways in which antifouling biocides can enter the environment:

• during the application of the antifouling paint to boats or cage fish farm nets;
• leaching from paint on the hulls of vessels or from cage fish farm nets;
• when paint is removed;
• when paint remnants are discarded.

However, the actual input of each biocide to the aquatic environment will depend on the method and location of paint application, the leaching behaviour of the biocide once a painted boat is in the water and the method in which residual antifouling paint is removed from the hull of the boat.

Boxall et al (1998) estimated maximum and minimum quantities of antifouling bioicides distributed or used in the UK in 1 year:

Boxall et al (1998) reported environmental concentrations of 0.004 - 0.130 mg l^-1 for irgarol 1051, 0.013 - 1.0 mg l^-1 for diuron and a median concentration of approximately 7 mg l^-1 for Cu²⁺ in estuaries used by commercial and leisure craft.

Using a model of a marina, Boxall et al (1998) estimated that concentrations of each of highest use biocides in marina water would range from 0.023 - 254 mg l^-1 (although the authors recognised that the model used had some limitations and there may be some over estimation in the concentrations given).

There is limited information for the remaining booster biocides. Irgarol 1051 has a log Kow of 2.8, indicating that it is unlikely to sorb strongly to sediments or suspended solids. The photolysis half-life of 273 days suggested that exposure to light was not a major fate process. Irgarol is also not readily biodegraded and could therefore be considered persistent in the marine environment (Boxall et al 1998).

See elsewhere for diuron and copper.

An exhaustive literature review on the toxicity of booster biocides in antifoulant paints to marine organisms has not been carried out for the purposes of this profile. The information provided in this section is taken from existing review documents (Boxall et al 1998). The most sensitive groups of organisms have been identified.

Toxicity data for the majority of these chemicals are limited. Data cited in Boxall et al (1998) reported LC50 concentrations for irgarol, diuron and dichlofluanid. For fish, these ranged from 300 - 25,000 mg l^-1 and 1 - 16,000 mg l^-1 for algae.  

See elsewhere for diuron and copper.

No bioaccumulation data were reported by Boxall et al (1998) for irgarol or dichlofluanid but log Kow values of 2.8 and 3.7 respectively indicated that irgarol 1051 was unlikely to bioaccumulate and that dichlofluanid had the potential to bioaccumulate. Further information is required to establish the bioaccumulation potential of these substances. 

See elsewhere for diuron and copper.

Potential effects include:

• toxicity of diuron and dissolved copper to aquatic organisms at concentrations in the water column above the EQSs for these substances;
• toxicity of irgarol and dichlofluanid to aquatic organisms in the water column, especially around sites used by leisure craft (marinas, harbours and moorings). There are no standards for these substances and monitoring of environmental concentrations is likely to be limited. A precautionary approach should be adopted in relation to these substances in European marine sites encompassing sites used extensively by leisure craft.

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