Organotin compounds are amongst the worst environmental pollutants in history because of their unforeseen stability in the environment and adverse effects on marine organisms, including both direct toxicity and indirect consequences such as endocrine disruption. Many studies are addressed the spread of organotin contamination and the mechanisms for toxicity in aquatic organisms; these are summarized in dedicated sections on organotin compounds in this volume.
As a consequence of such research, the application of organotin compounds has now been banned by IMO and inputs to the marine environment will be reduced in the near future. However, to what extent an how quickly will organotin pollution be improved by this prohibition? The answer is uncertain. Many issues remain concerning the timescales of recovery of the marine environment from organotin contamination. Probably the most serious of these is the legacy organotin loadings in sediment. Organotin compounds may be reversibly adsorbed on to sediment, or entrained as paint particles, and are likely to remain stable for long time, with a strong possibility of gradual re-elution from sediment to the water column. Close to shipping channels, harbours and ports, dredging of heavily contamination sediment may be needed to maintain access, promoting the likelihood of enhanced remobili-zation. The spread of organotin contamination to the deep sea environment confirms concerns over long-distance transport and even indicates potential for recirculation back to coastal waters by currents. Furthermore, some fish back forth between deep sea and shallow coastal waters, crossing and extending contamination boundaries. These phenomenon present additional risks for marine organisms in shallow water, and, potentially, human consumers. The elucidation of contaminant transport processed to deep sea environments in an important prerequisite if steps are to be taken to reduce such pathways. Our closing concern is over organotins is the presence of relatively high concentrations in marine mammals compared other marine organisms. This is an emerging, and potentially serious, characteristic of organotin pollution and one which requires better understanding of the mechanisms of organotin metabolism in different taxonomic groups.