Both legacy and emerging: Organotin pollutants in marine environments

The annual production of organotin has far exceeded that at the end of the last century. Even after various restrictions on the use and consumption substitution of traditional organotin products, organotin pollutants are still considered to have great potential to enter and affect the marine environment. This review introduces the trends in research on marine organotin pollution. According to continuous observations in some sea areas (e.g., European areas, Hong Kong coast), the levels of tributyltins (TBTs) and their products (supposed mainly from antifouling paints applied to ship hulls) remaining in sediments and biota are slowly but gradually decreasing, though new TBT inputs can be occasionally observed. Several reports have observed or speculated on new marine sources of TBTs such as disposal sites for dredged material, aquaculture activities, etc. Possibly due to regional differences in policies or industries, the levels of phenyltins have surpassed butyltins in many Asian sea areas. Additionally, the members reaching the current top production of organotins, such as monobutyltins, methyltins, dibutyltins, tetrabutyltins, may become or have become main organotin pollutants. Therefore, organotins in the marine environment are both legacy and emerging pollutants. For them, there are still some gaps in current research, e.g., the distribution of previously ignored organotin species, and the possible high levels of organotins in marine plastic debris convergence areas. Some explanation and evidence are also needed for phenomena observed in the remote sea areas, such as higher proportions of diorganotins, significantly different from that in the coastal sea areas.