TBT in dust around Malta and Gozo with special reference to indoor dust

Abstract

This study aims at determining the concentrations of organotins in the dust found in inhabited houses around Malta and Gozo. A total of 41 samples were taken from houses around Malta and Gozo; 32 from Malta and 9 from Gozo. This was the first study which involved the island of Gozo. The concentrations of the organotins monobutyltin, dibutyltin and tributyltin were measured. This study was carried out together with a parallel study in our laboratory in which the concentrations of the same organotins were measured in outdoor dust. An aim of this study was to compare the results obtained by the two studies. Organotins were extracted from the dust samples in glacial acetic acid and derivatized and extracted in a single step using sodium tetraethylborate and iso-octane. Ultrasonication was used to assist extraction. This study showed that MBT and DBT are found ubiquitously in indoor dust of houses around Malta and Gozo. Higher concentrations were found in Malta houses. TBT is found less frequently, but when encountered, it is found at relatively high levels, especially in the fishing village of Marsaxlokk. No TBT was found in Gozo indoor dust. When compared to a previous study (Baldacchino, 2007), this study has shown that levels of MBT and DBT are higher in this study. Levels of TBT were found to be statistically similar to the levels of the previous study. The organotin levels in indoor dust were also compared to those found in outdoor dust as a result of a parallel study in our laboratory. MBT levels are higher in inside dust while TBT levels are higher in settled outdoor dust. DBT levels were found to be statistically similar. MBT in house dust is probably present by leaching from plastics and furnishings while TBT ends up in indoor dust by entering the house through doors and windows. Dust containing TBT is emitted when ships and boats covered by TBT-based antifouling paint are scraped off of their paint. Even though the use of TBT in antifouling paint has been banned since 2003, it is still found in indoor dust. This could imply that it degrades very slowly or that hulls coated with TBT-based antifouling paints are still being scraped. Both theories are likely to be true, but they have to be proven.