Aquatic Environmental Aspects of Non-Pesticidal Organotin Compounds

Non-pesticidal organotin compounds in Canadian commerce are those of monomethyltin, dimethyltin, monobutyltin, dibutyltin, monooctyltin and dioctyltin. A review is presented of the uses, methods of analysis, environmental occurrence and aquatic toxicity of these compounds, which are scheduled for assessment under the Canadian Environmental Protection Act. It is likely that the most important non-pesticidal route of entry of these compounds to the environment will be through leaching of organotin-stabilized poly(vinyl chloride) by water. Monomethyltin and dimethyltin are widespread in the global environment. Monobutyltin and dibutyltin have been found frequently in harbours, marinas and shipping channels in Canada and elsewhere, arising largely as degradation products from the use of the antifouling agent tributyltin which is now regulated in Canada. There are few reports in the literature on the occurrence of butyltin species as a result of non-pesticidal uses or uses of tributyltin other than as an antifouling agent. Monooctyltin and dioctyltin have not been found to date in Canada or elsewhere in environmental samples. Judging from concentrations which have been reported to date, it appears that the mono- and di-methyltin, butyltin and octyltin species pose no threat to aquatic organisms in Canada vis-à-vis acute toxicity. Data on the persistence of these species in aquatic environments are in some cases fragmentary or non-existent, but in general it appears that these species would not be persistent in aquatic environments, with half-lives estimated to be less than a few months at 20°C.