Should TBT continue to be considered an issue in dredging port areas? A brief review of the global evidence

Dredging is periodically required to keep channels and maneuvering basins open in many ports around the world. However, the dredging of contaminated sediments may turn this routine procedure into a source of pollution in the receiving water bodies. Many pollutants, such as heavy metals, organic or organometallic compounds are present in high concentrations due to human activities in the coastal areas, where ports are located. Thus, the risks posed by dredging should be carefully evaluated for the conservation of environmental quality. Organotin compounds were extensively used as antifouling biocides worldwide for decades, causing considerable damage to localized coastal areas before being banned by IMO in 2008. Afterward, organotin concentrations decreased in most studied areas, as indicated by several recent studies in the literature. In some instances, however, there are still instances of biological effects of organotins application or legacy pollution being reported. It could be argued that until a complete recovery could be inferred, these hot spots should have organotins included in the evaluation of possible environmental impacts of dredging activities. Besides, when considering naval activities, most currently used antifouling systems still included biocides. The possible risks posed by these alternative technologies should be evaluated in the same way. This article briefly reviews this argument, using the recent literature on this subject.