Degradation of antifouling biocides

The relative biodegradability in seawater of a number of compounds in current use in antifouling paints viz. Sea-Nine™ 211 antifoulant (4,5-dichloro-2-n-octyl-4-isothiazolin-3-one), Irgarol(R) 1051 (2-methylthio-4-tert-butylamino-6-cyclopropylamino-s-triazine), diuron (3-(3,4-dichlorophenyl)l-l-dimethylurea), chlorothalonil (tetrachloroisophthalonitrile) and TBTO (tributyltin oxide) was investigated. The disappearance of the each compound from seawater was monitored over 8 w by bioassay using the ship-fouling diatom Amphora coffeaeformis. The results show, that under the test conditions employed, biodegradability ranges from very readily biodegradable (Sea-Nine 211) to non-biodegradable (diuron and Irgarol 1051). The results are discussed in relation to published data on biocide degradation.