Status of butyltin contamination in Thailand coastal waters

The aquatic pollution by tributyltin (TBT) arising from anti-fouling paints has been of great concern due to their effect of shell malformation in oysters, mortality of the larvae of mussels and imposex in gastropods, which occur at a very few nanogram per liter of aqueous TBT concentrations. Studies show that TBT is a widespread problem and posing a threat to sensitive species in coastal areas where shipping traffic intensities are above a certain level and in the vicinity of harbours. The occurrences of gastropod imposex and butyltin contamination in seawater, sediments, and green mussels from coastal waters of Thailand have been carried out since 1995 in order to assess the status of TBT contamination in the Thai coastal waters. Studies indicated that TBT contamination was a problem in areas with shipyards and repairing facilities or associated with elevated activities of ocean-going vessels or commercial shipping. The situation of TBT contamination in the Thai waters, however is improving; although several TBT hotspots in sediments still exist in the inner Gulf of Thailand and high levels of imposex are still being reported from the east coast of Phuket Island. Restrictions on the use of TBT antifouling paints are in the process of being implemented whereas Coastal Water Quality Standard for TBT has already been imposed. More data are needed on TBT levels in other marine organisms for further evaluation