First assessment of butyltins (BuTs) contamination of the Montenegrin coast (Southeast Adriatic): Tributyltin (TBT) poses a threat to the marine ecosystem.

This study presents the first assessment of butyltins (BuTs) pollution of the Montenegrin coast. The distribution of tributyltin (TBT), dibutyltin (DBT) and monobutyltin (MBT) was investigated in mussels, sediments and water overlying sediment after the sediment resuspension. The results showed that the investigated sites (marinas, ports, shipyards) are contaminated with BuTs (19-402 ng (Sn)/g in mussels; 43-20,641 ng (Sn)/g in sediments; 9-566 ng (Sn)/L in overlying waters). The measured TBT concentrations indicate that toxic effects on marine organisms are expected at most locations. The simultaneous analysis of BuTs and total Sn in sediment cores allowed the assessment of TBT historical input, while it was demonstrated that resuspension of contaminated sediments leads to the release of all BuTs into the water column. This study shows that, despite the ban of TBT-based antifouling paints more than a decade ago, pollution of the marine environment with TBT is still a problem and regular monitoring remains essential.

Imposex assessment and tributyltin levels in sediments along the Atlantic coast of South Africa.

Female marine gastropods develop imposex (growth of penis/vas deferens) when exposed to TBT (tributyltin). Ours, is the first report of an imposex survey associated with TBT in sediment along 920 km of South Africa's Atlantic coastline. We sampled and analysed 1389 individuals of 13 caenogastropod species, and sediment samples from 25 sites, presumed impacted and not impacted by TBT pollution. Imposex was detected in six species not previously reported to suffer from this phenomenon, at eight sites, with up to 100% of females affected. Butyltins were found at quantifiable concentrations at four sites, with TBT and DBT (dibutyltin) concentrations in sediments up to 20 000 µg/kg dry mass (dm) and 3740 µg/kg dm, respectively. These findings are of major concern considering that TBT has been banned globally since 2008 by the International Maritime Organisation (IMO) - more extensive research is required in areas affected by TBT and where aquaculture is present.

First assessment of the effectiveness of the international convention on the control of harmful anti-fouling systems on ships in Tunisia using imposex in Hexaplex trunculus as biomarker.

The global ban on the use of tributyltin (TBT) forced in September 2008 was ratified in Tunisia as late as June 2011. In this context, the present study aims to highlight the consequences of TBT contamination by monitoring 22 Tunisian sites before (2007) and after the ban (2012 and 2016) using as biomarker the occurrence of imposex in Hexaplex trunculus. From 2004 to 2016, complete recovery from imposex was reported in 11 sites. All average imposex indices calculated for each sampling year also decreased: imposex incidence from 61 to 27%, VDSI from 2 to 0.7, and RPLI from 15.7 to 1.6%. Ecological Quality Ratios (EQR) revealed that the sampling sites are in moderate to good ecological status. Overall, the present study confirms the effectiveness of the enacted legislation in reducing the impact of TBT pollution along the Tunisian coast.

Organotins and new antifouling biocides in water and sediments from three Korean Special Management Sea Areas following ten years of tributyltin regulation: Contamination profiles and risk assessment.

A simultaneous monitoring study on organotins (butyltins and phenyltins) and most frequently used alternative antifouling biocides (Irgarol 1051, Diuron, Sea-Nine 211 and M1) in water and sediments (n=44) collected from three Special Management Sea Areas operated by Korean government. The lower concentration of butyltins (BTs) than that of new antifouling biocides (NEW) was found in water but the significant greater concentration of BTs than that of NEW was still found in sediments. The tributyltin (TBT) levels in water exceeded the chronic criterion to protect seawater aquatic life at several sites. Even ten years after the ban of the use of TBT-based antifouling paint, the concentrations of TBT, Diuron and Irgarol 1051 in sediments from shipyards exceeded global sediment quality guidelines and potentially poses adverse risks on marine organisms and extremely high concentration of TBT up to 2304ng/g was found for a sediment collected at a shipyard.

Binary mixture toxicities of triphenyltin with tributyltin or copper to five marine organisms: Implications on environmental risk assessment.

Triphenyltin (TPT) often coexists with tributyltin (TBT) and Cu in coastal waters worldwide. The combined toxic effect of TPT and TBT has always been assumed to be additive without any scientific proof, and the combined effect of Cu and TPT on marine organisms has not been vigorously studied. This study, therefore, investigated the acute toxicity of binary mixture of TPT/Cu and TPT/TBT to five selected marine species including Thalassiosira pseudonana, Skeletonema costatum, Tigriopus japonicus, Brachionus koreanus and Oryzias melastigma. The interaction between TPT and TBT or Cu was modeled antagonistic based on concentration addition (CA) model, while it was synergistic according to response addition (RA) model. Both model well predicted the toxicity of binary mixtures to the five organisms. As for the environmental risk assessment, CA overestimated the toxicity in most cases and thus is a more conservative model than RA model for assessing the toxicity of these chemical mixtures.

An assessment of butyltins and metals in sediment cores from the St. Thomas East End Reserves, USVI.

Tributyltin (TBT) concentrations near a marina complex in Benner Bay on St. Thomas, US Virgin Islands, were elevated relative to other areas in a larger study of the southeastern shore of the island. At the request of the USVI Coastal Zone Management Program, sediment cores and surface sediment samples were collected to better define the extent and history of TBT deposition in the vicinity of Benner Bay. The sediment cores were sectioned into 2-cm intervals and dated with 210Pb and 137Cs. The core sections and the surface samples were analyzed for butyltins and 16 elements. Deposition rates varied from 0.07-5.0 mm/year, and were highest in the marina complex. Core ages ranged from 54 to 200 years. The bottoms of the cores contained shell hash, but the top layers all consisted of much finer material. Surface concentrations of TBT exceeded 2000 ng Sn/g (dry weight) at two locations. At a depth of 8 cm TBT exceeded 8800 ng Sn/g in the marina complex sediment. Based on the ratio of tributyltin to total butyltins, it appears that the marina sediments are the source of contamination of the surrounding area. There is evidence that vessels from neighboring islands may also be a source of fresh TBT. Copper concentrations increase over time up to the present. Gradients of virtually all metals and metalloids extended away from the marina complex. NOAA sediment quality guidelines were exceeded for As, Pb, Cu, Zn, and Hg.

Distribution of butyltin compounds in Brazil's southern and southeastern estuarine ecosystems: assessment of spatial scale and compartments.

Butyltin compounds (BTs), including tributyltin (TBT) and its degradation products, dibutyltin and monobutyltin, have been found in a diversity of aquatic systems and causing toxic effects in target and nontarget organisms. They enter in coastal systems through different sources (as antifouling paints, industrial effluents, etc.) where they interact with biotic and abiotic components, and their distribution is commonly determined by the morphological and hydrodynamic conditions of the coastal systems. In this study, we discuss the contamination by BTs on a spatial scale (eight estuaries with three subareas each) and in different compartments of the estuaries (sediments, suspended particulate matter (SPM), and estuarine catfish tissues (liver and gills). Lower concentrations of BTs were found in the sediments (n.d. to 338 ng g(-1)) in comparison to studies before a ban of TBT in antifouling paints was enacted, mostly indicating an old input or preservation related with sediment properties and composition. For SPM samples (n.d. to 175 ng L(-1)) as well as in fish tissues (n.d. to 1426 ng g(-1)), the presence of these compounds was frequent, especially in the fish due to their movement throughout the estuaries and the potential to assess point sources of BTs. These results indicate that BTs persist in the environment, with variation in amounts between investigated estuaries and even at locations inside the same estuary, because of ideal preservation conditions, transport to remote areas, and input from different sources.

Assessment of background concentrations of organometallic compounds (methylmercury, ethyllead and butyl- and phenyltin) in French aquatic environments.

The aim of this work is to estimate background concentrations of organometallic compounds, such as tributyltin (TBT), dibutyltin (DBT), monobutyltin (MBT), triphenyltin (TPhT), diphenyltin (DPhT), monophenyltin (MPhT), methylmercury (MeHg), inorganic mercury (iHg) and diethyllead (Et2Pb) in the aquatic environment at the French national scale. Both water and sediment samples were collected all over the country, resulting in 152 water samples and 123 sediment samples collected at 181 sampling points. Three types of surface water bodies were investigated: rivers (140 sites), lakes (19 sites) and coastal water (42 sites), spread along the 11 French river basins. The choice of sites was made on the basis of previous investigation results and the following target criteria: reference, urban sites, agricultural and industrial areas. The analytical method was properly validated for both matrices prior to analysis, resulting in low limits of quantification (LOQ), good precision and linearity in agreement with the Water Framework Directive demands. The results were first evaluated as a function of their river basins, type of surrounding pressure and water bodies. Later, background concentrations at the French national scale were established for both water and sediment matrices, as well as their threshold, i.e., the concentration that distinguishes background from anomalies or contaminations. Background concentrations in water are ranging between <0.04-0.14 ng Hg. L(-1) for MeHg, <0.14-2.10 ng Hg. L(-1) for iHg, <1.0-8.43 ng Pb. L(-1) for Et2Pb and 0.49-151 ng Sn. L(-1), <0.08-3.04 ng Sn. L(-1) and <0.08-0.25 ng Sn. L(-1) for MBT, DBT and TBT, respectively. For sediments, background concentrations were set as <0.09-1.11 ng Hg. g(-1) for MeHg, <0.06-24.3 ng Pb. g(-1) for Et2Pb and <1.4-13.4 ng Sn. g(-1), <0.82-8.54 ng Sn. g(-1), <0.25-1.16 ng Sn. g(-1) and <0.08-0.61 ng Sn. g(-1) for MBT, DBT, TBT and DPhT, respectively. TBT occurs in higher concentrations than the available environmental protection values in 24 and 38 sampling sites for both water and sediment samples, respectively. Other phenyltins (MPhT and TPhT) did not occur above their LOQ and therefore no background was possible to establish. Throughout this work, which is the first assessment of background concentrations for organometallic compounds at the French national level ever being published, it was possible to conclude that over the last 10-20 years organotin concentrations in French river basins have decreased while MeHg concentration remained stable.

Assessment of imposex and butyltin concentrations in Gemophos viverratus (Kiener, 1834), from São Vicente, Republic of Cabo Verde (Africa).

This work constitutes the first assessment of tributyltin (TBT) pollution levels in the Republic of Cabo Verde (Africa) and proposes the marine gastropod Gemophos viverratus (Kiener, 1834) as a new bioindicator of TBT pollution in the Macaronesia and west coast of Africa. Specimens were collected between August and October 2012 along a gradient of naval traffic in São Vicente Island. The results clearly indicate an increase of imposex levels (percentage of females affected with imposex, 0-100 %; vas deferens sequence index, 0-4.1; relative penis length index, 0-54.6 %) and female TBT contamination (from 5 to 37 ngSn g(-1) dry weight (dw)) from outside to inside the harbour of Porto Grande Bay and identify this area as the focus of TBT pollution in the island. The butyltin degradation index for G. viverratus tissues ranged between 1.3 and 2.2, which being above 1 suggests that a considerable part of TBT inputs to the bay may not be very recent. Sterile females were found inside the harbour with an incidence up to 21.4 %. Considering the existence of a planktonic veliger stage in the life cycle of G. viverratus, it is expected that recruitment of newborn individuals can be supplied from unaffected breeding females inside and outside the Porto Grande Bay, resulting in a reduced impact of TBT pollution on population abundance. G. viverratus is very promising to be used as a simple, inexpensive and efficient novel tool for TBT pollution biomonitoring in the Macaronesia and west coast of Africa, a region for which there is an astonishing lack of information concerning levels and ecological impacts of TBT pollution.

Risk assessment of butyltins based on a fugacity-based food web bioaccumulation model in the Jincheng Bay mariculture area: II. Risk assessment.

A fugacity-based food web bioaccumulation model was constructed, and the biotic concentrations of butyltins in the food web of the Jincheng Bay mariculture area were estimated accordingly, using the water and sediment concentrations described in the accompanying paper (Part I). This paper presents an ecological risk assessment (ERA) and a human health risk assessment (HHRA) of the butyltins, based on the estimated tissue residues in the marine life in this area. The results showed that the ecological risk probability was greater than 0.05. At this level, management control is critical since sensitive marine species would be profoundly endangered by butyltin contamination. Few if any detrimental effects, however, would be generated for humans from exposure to butyltins through seafood consumption. The fugacity-based model can refine the ERA and HHRA of pollutants in marine areas, provide a basis for protecting marine ecology and the security of fishery products, and thus help determine the feasibility of a proposed aquaculture project.

Risk assessment of butyltins based on a fugacity-based food web bioaccumulation model in the Jincheng Bay mariculture area: I. Model development.

A fugacity-based model was developed to simulate the bioaccumulation of butyltins in the food web of the Jincheng Bay mariculture area. The predicted biological tissue residues of tributyltin (TBT), dibutyltin (DBT), and monobutyltin (MBT) were 0.04-17.09, 0.14-53.54, and 0.27-108.77 ng-Sn g(-1), respectively, and the predicted values in six mollusca agreed well with the measured ones. The lipid-normalized concentrations did not significantly increase across trophic levels, indicating no biomagnification across aquatic food webs. These results were highly consistent with those observed both in the laboratory and field, which had been reported in numerous references. The explanation, from calculating their flux equilibrium in the food web, was that butyltins were primarily taken in via respiration from the water column by marine organisms. The sensitivities of the model parameters were analyzed, revealing that the hydrophobicity of butyltins played the dominant role in their bioaccumulation phenomena. The verified model predictions of the biotic tissue concentrations of the butyltins could be readily applied to perform internal ecological risk and human health risk assessments in this area.

An assessment of chemical contaminants in sediments from the St. Thomas East End Reserves, St. Thomas, USVI.

The St. Thomas East End Reserves or STEER is located on the southeastern end of the island of St. Thomas, USVI. The STEER contains extensive mangroves and seagrass beds, along with coral reefs, lagoons, and cays. Within the watershed, however, are a large active landfill, numerous marinas, resorts, various commercial activities, an EPA Superfund Site, and residential areas, all of which have the potential to contribute pollutants to the STEER. As part of a project to develop an integrated assessment for the STEER, 185 chemical contaminants were analyzed in sediments from 24 sites. Higher levels of chemical contaminants were found in Mangrove Lagoon and Benner Bay in the western portion of the study area. The concentrations of polychlorinated biphenyls (PCBs), dichlorodiphenyltrichloroethane (DDT), zinc, copper, lead, and mercury were above a NOAA Effects Range-Low (ERL) sediment quality guideline at one or more sites, indicating impacts may be present in more sensitive species or life stages. Copper at one site in Benner Bay was above a NOAA Effects Range-Median (ERM) guideline indicating effects on benthic organisms were likely. The antifoulant boat hull ingredient tributyltin (TBT) was found at the third highest concentration in the history of NOAA's National Status and Trends (NS&T) Program, which monitors the nation's coastal and estuarine waters for chemical contaminants and bioeffects. The results from this project will provide resource managers with key information needed to make effective decisions affecting coral reef ecosystem health and gauge the efficacy of restoration activities.

Assessment of TBT and organic booster biocide contamination in seawater from coastal areas of South Korea.

Seawater samples from major enclosed bays, fishing ports, and harbors of Korea were analyzed to determine levels of tributyltin (TBT) and booster biocides, which are antifouling agents used as alternatives to TBT. TBT levels were in the range of not detected (nd) to 23.9 ng Sn/L. Diuron and Irgarol 1051, at concentration ranges of 35-1360 ng/L and nd to 14 ng/L, respectively, were the most common alternative biocides present in seawater, with the highest concentrations detected in fishing ports. Hot spots were identified where TBT levels exceeded environmental quality targets even 6 years after a total ban on its use in Korea. Diuron exceeded the UK environmental quality standard (EQS) value in 73% of the fishing port samples, 64% of the major bays, and 42% of the harbors. Irgarol 1051 levels were marginally below the Dutch and UK EQS values at all sites.

Assessment of organotin (butyltin species) contamination in marine biota from the Eastern Aegean Sea, Turkey.

The marine environment continues to be adversely affected by tributyltin (TBT) release from maritime traffic. Therefore the concentrations of TBT, dibutyltin (DBT) and monobutyltin (MBT) were measured in barnacles, mussels and fish along the Eastern Aegean coastline. The average concentrations of TBT ng Sn g⁻¹ were found to be 235 in fish, 116 in mussels and 635 in barnacles. The highest concentrations of TBT, DBT and MBT were observed in the barnacles which had been sampled in marinas and harbors. All mussels sampled showed values of TBT+DBT, which were below the "tolerable average residue level (TARL)" as currently accepted. This indicates a lack of risk to the consumer. However, 7 out of the 15 fish sampled displayed TBT+DBT levels above the TARL, which indicates that a fish consumer group may be at risk. Barnacles have high potential as biomonitors for the presence of organotin in the Aegean Sea.

Analysis of ultratrace triorganotin compounds in aquatic organisms by using capillary electrophoresis-inductively coupled plasma mass spectrometry.

A microwave-assisted extraction used to extract trace triorganotin from aquatic organisms and a sensitive analytical method for the determination of ultratrace triorganotin (namely trimethyltin, triethyltin, tripropyltin and tributyltin) with capillary electrophoresis-inductively coupled plasma mass spectrometry were firstly described in this study. The extraction method is simple, effective and can be used to extract trace triorganotin in aquatic organisms within several min. The analytical method has a much lower detection limit of 0.2-0.7 ng Sn/mL for triorganotin compounds, and can be used to determine trace triorganotin in aquatic organisms directly without any derivatization and preconcentration. Using above methods, we have successfully determined trimethyltin, triethyltin, tripropyltin and tributyltin in dried Mya arenaria Linnaeus and Corbicula fluminea within 17 min with a recovery of 93-104% and a RSD (relative standard deviation, n=6) of 2-5%. Our results showed that dried M. arenaria Linnaeus contained an extremely high tributyltin of 5.1 microg Sn/g dried weight, indicating that it may be a good biomarker for the organotin pollution in ocean.

Assessment of antifouling biocides contaminations in Maizuru Bay, Japan.

The concentrations of organotin compounds in the aquatic environment of Maizuru Bay and their spatial distribution are discussed. The concentrations of tributyltin (TBT) compounds in water samples ranged from 0.001 to 0.002 microg l(-1), and monobutyltin compounds were the dominant species among the butyltin compounds. TBT concentrations in Maizuru Bay are low compared with other coastal waters of Japan. Drastic differences in TBT concentrations were not observed among the Maizuru Bay sites. Phenyltin compounds were not detected in the water samples. Concentrations of TBT and triphenyltin (TPT) in sediment from Maizuru Bay ranged, respectively, from 0.9 to 11 microg kg(-1), from 0.2 to 17 microg kg(-1) dry weight (dw). TBT concentrations in Maizuru Bay were lower than those in other coastal areas of Japan. TPT concentrations were greater than TBT concentrations in the fishing port. The concentrations of TBT and TPT in blue mussels (M. galloprovincialis) from Maizuru Bay were in the range of 2.4 to 9.3 microg kg(-1) and 0.2-13 microg kg(-1) wet weight (ww), respectively. A tolerable average residue level (TARL) was estimated at 74.8 microg kg(-1) from a tolerable daily intake (TDI) of 0.25 bis(tributyltin)oxide microg kg(-1) body weight day(-1). TBT concentrations detected in blue mussel samples were lower than the TARL values. The acceptable concentration of TPT, which were calculated using acceptable daily intake instead of TDI, was 127 microg kg(-1). Concentrations of TPT in blue mussel samples were also lower than the TARL. TBT compounds in blue mussel samples were at similar levels among the various sampling sites, indicating that TBT is not currently being used in ship hull paints; the ratios of degradation products of TBT and TPT were greater than those of the parent compounds. Concentrations of alternative biocides in water samples were also investigated in the bay. Although Sea-Nine 211, M1, and Pyrithiones were not detected, Diuron and Irgarol 1051 were detected at 0.010-0.257 and at 0.002-0.018 microg l(-1), respectively. Concentrations of Diuron were great in the shipping route and near the shipyard, whereas the concentration of Irgarol 1051 was great at the fishing port. Concentrations of Diuron and Irgarol 1051 in sediment from Maizuru Bay ranged, respectively, from <0.08 to 12, from <0.08 to 9.8 microg kg(-1) dw, respectively. Despite being a semi-enclosed bay, we found that sediment in Maizuru Bay is not contaminated by alternative biocides to the degree found in other coastal areas. Copper concentrations of sediment were at ordinary levels, and those of blue mussels were slightly lower than those reported previously in other coastal areas of Japan. In both the sediment and blue mussels, there was no correlation between the presence of copper and antifouling biocides.

Development of a low-cost method of analysis for the qualitative and quantitative analysis of butyltins in environmental samples.

Most analytical methods for butyltins are based on high resolution techniques with complicated sample preparation. For this study, a simple application of an analytical method was developed using High Performance Liquid Chromatography (HPLC) with UV detection. The developed method was studied to determine tributyltin (TBT), dibutyltin (DBT) and monobutyltin (MBT) in sediment and water samples. The separation was performed in isocratic mode on an ultra cyanopropyl column with a mobile phase of hexane containing 5% THF and 0.03% acetic acid. This method was confirmed using standard GC/MS techniques and verified by statistical paired t-test method. Under the experimental conditions used, the limit of detection (LOD) of TBT and DBT were 0.70 and 0.50 microg/mL, respectively. The optimised extraction method for butyltins in water and sediment samples involved using hexane containing 0.05-0.5% tropolone and 0.2% sodium chloride in water at pH 1.7. The quantitative extraction of butyltin compounds in a certified reference material (BCR-646) and naturally contaminated samples was achieved with recoveries ranging from 95 to 108% and at %RSD 0.02-1.00%. This HPLC method and optimum extraction conditions were used to determine the contamination level of butyltins in environmental samples collected from the Forth and Clyde canal, Scotland, UK. The values obtained severely exceeded the Environmental Quality Standard (EQS) values. Although high resolution methods are utilised extensively for this type of research, the developed method is cheaper in both terms of equipment and running costs, faster in analysis time and has comparable detection limits to the alternative methods. This is advantageous not just as a confirmatory technique but also to enable further research in this field.

Assessment of tributyltin contamination in a shipyard area using a mussel transplantation approach.

Mussels (Mytilus galloprovincialis) were transplanted to seven stations around a large shipyard for 126 days to evaluate tributyltin (TBT) contamination. Although the application of TBT-based paints to ships is totally banned in Korea, butyltin compounds were found to accumulate in mussels following transplantation. Concentrations of TBT and total butyltins in transplanted mussels near the shipyard were in the range of 40-350 ng Sn/g and 74-530 ng Sn/g on a dry weight basis, respectively. Obviously, low TBT concentrations (6.0-53 ng Sn/gdw) were determined in mussels at four stations outside the shipyard. A negative gradient of TBT concentrations and TBT portion to total butyltin concentrations were found in both the surface water and transplanted mussels according to distance from the shipyard. In addition, TBT concentrations in surface water and transplanted mussels showed significant correlation (r(2) = 0.71; p < 0.001). These results indicate that the shipyard still releases fresh TBT into surrounding waters even after TBT regulation in Korea, and mussel transplantation is useful in evaluating TBT contamination in shipyard area.

Assessment of sediment contamination in Casco Bay, Maine, USA.

The current status of contaminant concentrations in Casco Bay, decadal trends of these contaminants and changes in their geographical distribution are assessed using sediment samples collected approximately 10 years apart. In general, regulated contaminants appeared to be decreasing in concentration. Total PAH and dioxins/furans concentrations did not significantly change over this period. Total organochlorine pesticides, 4,4-DDE, 4,4-DDD, total DDT, PCB, tributyltin and total butyltin decreased in concentration. Trace element concentrations in sediments decreased at the majority of the sampling sites for chromium, nickel, and selenium while arsenic, cadmium, copper, lead, mercury, silver, and zinc remained relatively constant. None of the contaminants measured has increased by more than a factor of 2. Selected sites located in the Inner Bay, where concentrations are higher and new inputs were more likely, showed increased concentrations of contaminants. Most contaminants were not found at concentrations expected to adversely affect sediment biota based on ERL/ERM guidelines.

Integrative assessment of organotin contamination in a southern European estuarine system (Ria de Aveiro, NW Portugal): tracking temporal trends in order to evaluate the effectiveness of the EU ban.

Organotin (OT) compounds have been used as biocide agents in antifouling paints since the mid 1960s and are now ubiquitous in the marine environment. Due to their high toxicity to non-target species they were banned from antifouling paints in the European Union in 2003 (2002/62/EC directive). The aim of the present work is to assess any obvious decline of the OT environmental levels at Ria de Aveiro (NW Portugal) after the ban. The organotins - monobutyltin (MBT), dibutyltin (DBT), tributyltin (TBT), monophenyltin (MPT), diphenyltin (DPT), triphenyltin (TPT), monoctyltin (MOT), dioctyltin (DOT) and trioctyltin (TOT) - were quantified in the gastropod Nassarius reticulatus, in the mussel Mytilus galloprovincialis and in sediments. Imposex (imposition of male characters on females of gonochorist gastropods) in N. reticulatus was additionally used as a biomarker of TBT pollution. Time comparisons show a slight decrease of imposex between 2003 and 2005 probably as a consequence of the EU ban, though in some cases this trend seems to have started earlier since 2000. The fraction of TBT relatively to its metabolites has been decreasing over the last years but still remains high suggesting that there are still recent inputs of this compound into the study area.