Ecotoxocicological assessment of antifouling biocides and non-biocidal antifouling paints

1. Introduction

The present study includes ecotoxicological properties and risk assessment with relation to active substances in antifouling paints and to chemical compounds leaching from non-biocidal paints. Recently, the properties of a number of active substances in marine bottom paints for pleasure craft and larger vessels with regard to health and the environment were assessed in the report "Survey and assessment of antifouling products for pleasure craft in Denmark" (Madsen et al. 1998) prepared by CETOX (Centre for Integrated Environment and Toxicology) and the National Environmental Research Institute (NERI). These assessments (Madsen et al. 1998) were completed in three months, which did not allow a more detailed examination of the available information on the active substances. On the basis of the recommendations in the "Survey and assessment of antifouling products for pleasure craft in Denmark", the active substances, copper, 4,5-dichloro-2-n-octyl-4-isothiazolin-3-on (DCOI) and zinc pyrithione were selected for a more careful assessment of their environmental hazard.

The assessment of copper is based on a study of available literature focusing the relations between the speciation, bioavailability and ecotoxicity of copper.

The very scanty literature published on DCOI and zinc pyrithione has necessitated the inclusion of investigations carried out by the manufacturers, Rohm and Haas and Arch Chemicals. This material was supplemented with new investigations of the biodegradability of the two substances in Danish coastal sediments under aerobic and anaerobic conditions. Furthermore, the effect of degradation and sorption to sediment on the aquatic toxicity of the two biocides was illustrated in laboratory tests with the marine crustacean Acartia tonsa. The information on the degradation, distribution and toxicity of the biocides in the marine environment was used for a risk assessment based on the following two scenarios: a Danish pleasure craft harbour and a busy navigation route. The two scenarios are defined in such a way that the estimated exposure concentrations (Predicted Environmental Concentration, PEC) are expected to be realistically conservative resulting in the estimated PEC values only seldom being exceeded in practice (see Appendix 1 for a more detailed description of the calculation of PEC).

The ecotoxicological properties of an epoxy-based and a silicone-based paint without biocides were examined in studies of the toxicity of water samples from leaching tests. In these tests, the ratio of painted area to liquid volume was 13-14 times higher than this ratio is expected to be in a harbour with a large amount of pleasure craft. The ecotoxicological studies included tests with the marine green alga Skeletonema costatum and tests for acute and chronic toxicity to A. tonsa.