Long term behaviour and degradation kinetics of tributyltin in a marina sediment

Methylation and dealkykation of tin compounds by sulfate- and nitrate-reducing bacteria

In this study, axenic cultures of sulfate-reducing (SRB) and nitrate-reducing (NRB) bacteria were examined for their ability to methylate inorganic tin and to methylate or dealkylate butyltin compounds. Environmentally relevant concentrations of natural abundance tributyltin (TBT) and ¹¹⁶Sn-enriched inorganic tin were added to bacterial cultures to identify bacterial-mediated methylation and dealkylation reactions. The results show that none of the Desulfovibrio strains tested was able to induce any transformation process. In contrast, Desulfobulbus propionicus strain DSM-6523 degraded TBT either under sulfidogenic or non-sulfidogenic conditions. In addition, it was able to alkykate ¹¹⁶Sn-enriched inorganic tin leading to the formation of more toxic dimethyltin and trimethyltin. A similar capacity was observed for incubations of Pseudomonas but with a much greater dealkykation of TBT. As such, Pseudomonas sp. ADR42 degraded 61% of the initial TBT under aerobic conditions and 35% under nitrate-reducing conditions. This is the first work reporting a simultaneous TBT degradation and a methylation of both inorganic tin species and TBT dealkykation products by SRB and NRB under anoxic conditions. These reactions are environmentally relevant as they can control the mobility of these compounds in aquatic ecosystems; as well as their toxicity toward resident organisms.

Fifteen years of imposex and tributyltin pollution monitoring along the Portuguese coast

IMO's Anti-Fouling Systems convention banned the use of organotin-based antifouling systems in 2008 as the ultimate effort to stop tributyltin (TBT) inputs into the marine environment. One of the hazardous effects of TBT is imposex (the superimposition of male sexual characters onto gastropod females), a phenomenon that may cause female sterility and the gastropod populations decline. Despite previous European Union legislation had already been shown effective in reducing the imposex levels along the Portuguese coast, this study intends to confirm these decreasing trends after 2008 and describe the global evolution in the last 15 years. Imposex levels were assessed in two bioindicators - the dog-whelk Nucella lapillus and the netted-whelk Nassarius reticulatus (Gastropoda, Prosobranchia) - in 2011 and 2014, and the results were compared with previous years. Both species showed progressive decreasing trends in imposex levels over the last 15 years; median values of the vas deferens sequence index (VDSI) fell from 3.96 to 0.78 in N. lapillus and from 3.39 to 0.29 in N. reticulatus. The temporal/spatial evolution of imposex suggests an apparent shift of TBT hotspots, being now restricted to fishing ports and marinas in detriment of large commercial harbours where TBT levels fell rapidly. Butyltins were measured in the whole tissues of N. lapillus females collected in 2014: monobutyltin (MBT) varied from < DL (detection limit: 1 ng Sn/g) to 13 ng Sn/g dw, dibutyltin (DBT) from 2.2 to 27 ng Sn/g dw and TBT from 1.5 to 55 ng Sn/g dw. Although TBT body burden has declined over time, the butyltin degradation index ([MBT]+[DBT])/[TBT] exhibited values < 1 in c. a. 90% of the sites assessed, suggesting that recent TBT inputs are still widespread in the Portuguese coast eventually due to illegal use of TBT antifouling systems and TBT desorption from sediments.

Sediments indicate the continued use of banned antifouling compounds

Antifouling paints are widely used to avoid organisms settling on boat hulls. The active ingredients in the paints have differed over the years where lead, TBT, irgarol and diuron have been deemed too harmful to non-target organisms and subsequently been banned within the EU. Most of these compounds however are persistent in the environment and can cause problems long after they are deposited. We have examined if present-day and banned substances used in antifouling paints can be found in sediments in a national park on the Swedish west coast. Sampled locations include waterways, natural harbours and small marinas for leisure crafts to investigate if number of visiting boats affect the concentration of antifouling compounds in sediments. Few significant differences were found when comparing the different locations types, suggesting that overall boat presence is more important than specific mooring sites, however, several banned antifouling compounds were found in the surface sediments.

Organotin persistence in contaminated marine sediments and porewaters: In situ degradation study using species-specific stable isotopic tracers

This paper provides a comprehensive study of the persistence of butyltins and phenyltins in contaminated marine sediments and presents the first data on their degradation potentials in porewaters. The study's aim was to explain the different degradation efficiencies of organotin compounds (OTC) in contaminated sediments. The transformation processes of OTC in sediments and porewaters were investigated in a field experiment using species-specific, isotopically enriched organotin tracers. Sediment characteristics (organic carbon content and grain size) were determined to elucidate their influence on the degradation processes. The results of this study strongly suggest that a limiting step in OTC degradation in marine sediments is their desorption into porewaters because their degradation in porewaters occurs notably fast with half-lives of 9.2 days for tributyltin (TBT) in oxic porewaters and 2.9±0.1 and 9.1±0.9 days for dibutyltin (DBT) in oxic and anoxic porewaters, respectively. By controlling the desorption process, organic matter influences the TBT degradation efficiency and consequently defines its persistence in contaminated sediments, which thus increases in sediments rich in organic matter.

Valuation of ecotoxicological impacts from tributyltin based on a quantitative environmental assessment framework

In the scientific literature, few valuations of biodiversity and ecosystem services following the impacts of toxicity are available, hampered by the lack of ecotoxicological documentation. Here, tributyltin is used to conduct a contingent valuation study as well as cost-benefit analysis (CBA) of measures for improving the environmental status in Swedish coastal waters of the Baltic Sea. Benefits considering different dimensions when assessing environmental status are highlighted and a quantitative environmental assessment framework based on available technology, ecological conditions, and economic valuation methodology is developed. Two scenarios are used in the valuation study: (a) achieving good environmental status by 2020 in accordance with EU legislation (USD 119 household(-1) year(-1)) and (b) achieving visible improvements by 2100 due to natural degradation (USD 108 household(-1) year(-1)) during 8 years. The later scenario was used to illustrate an application of the assessment framework. The CBA results indicate that both scenarios might generate a welfare improvement.

Assessment of organotin and tin-free antifouling paints contamination in the Korean coastal area

Twelve organotins (methyl-, octyl-, butyl-, and phenyl-tin), and eight tin-free antifouling paints and their degradation products were measured in marine sediments from the Korean coastal area, and Busan and Ulsan bays, the largest harbor area in Korea. The total concentration of tin-free antifouling paints was two- to threefold higher than the total concentration of organotins. Principal component analysis was used to identify sites with relatively high levels of contamination in the inner bay area of Busan and Ulsan bays, which were separated from the coastal area. In Busan and Ulsan bays, chlorothalonil and DMSA were more dominant than in the coastal area. However, Sea-Nine 211 and total diurons, including their degradation products, were generally dominant in the Korean coastal area. The concentrations of tin and tin-free compounds were significantly different between the east and west coasts.

Sources and historical record of tin and butyl-tin species in a Mediterranean bay (Toulon Bay, France)

Concentrations of inorganic tin (Sn(inorg)), tributyltin (TBT) and its degradation products dibutyltin (DBT) and monobutyltin (MBT) were measured in surface sediments and in two cores from the Toulon Bay, hosting the major French military harbour. Anticipating planned dredging, the aim of the present work is to map and evaluate for the first time the recent and historic contamination of these sediments by inorganic and organic Sn species derived from antifouling paints used for various naval domains including military, trade, tourism and leisure. Tin and butyl-Sn concentrations in the bay varied strongly (4 orders of magnitude), depending on the site, showing maximum values near the shipyards. The concentrations of total Sn (1.3-112 μg g(-1)), TBT (<0.5-2,700 ng g(-1)), DBT (<0.5-1,800 ng g(-1)) and MBT (0.5-1,000 ng g(-1)) generally decreased towards the open sea, i.e. as a function of both distance from the presumed main source and bottom currents. Progressive degradation state of the butyl-Sn species according to the same spatial scheme and the enrichment factors support the scenario of a strongly polluted bay with exportation of polluted sediment to the open Mediterranean. Low degradation and the historical records of butyl-Sn species in two (210)Pb-dated sediment cores, representative of the Northern Bay, are consistent with the relatively recent use of TBT by military shipyards and confirm maximum pollution during the 1970s, which will persist in the anoxic sediments for several centuries. The results show that (a) degradation kinetics of butyl-Sn species depend on environmental conditions, (b) the final degradation product Sn(inorgBT) is by far the dominant species after 10-12 half-life periods and (c) using recent data to reliably assess former TBT contamination requires the use of a modified butyl-Sn degradation index BDI(mod). Resuspension of extremely contaminated subsurface sediments by the scheduled dredging will probably result in mobilization of important amounts of butyl-Sn species.

Temporal trends (2004-2009) of imposex in rock shells Thais clavigera collected along the Korean coast associated with tributyltin regulation in 2003 and 2008

We investigated the temporal trend in contamination of butyltin compounds (BTs) along the Korean coast using imposex and tributyltin (TBT) burden in gastropods (Thais clavigera) as a biomonitor. Thais clavigera were collected from 26 locations with different shipping activities between 2004 and 2009 after restrictions on TBT-based antifouling paints were imposed in Korea. In the present study, imposex indices and TBT tissue concentrations significantly decreased over time from 2004 to 2009, confirming the effectiveness of TBT regulation. However, imposex in 2009 samples was still found. Significantly high imposex indices and TBT tissue residues were found in large ports containing commercial and ferry services compared with small ports and background areas. Imposex indices in background areas had decreased to zero, suggesting recovery from imposex caused by BT contamination. These results suggest that recovery from TBT contamination occurs faster in areas with very low maritime activities than areas with high maritime activities.

Reed beds may facilitate transfer of tributyltin from aquatic to terrestrial ecosystems through insect vectors in the Archipelago Sea, SW Finland

Due to their adsorptive behavior, organotin compounds (OTCs), such as tributyltin (TBT), are accumulated in aquatic sediments. They resist biodegradation and, despite a ban in 2008, are a potential source for future exposure. Sediment OTCs have mostly been measured from sites of known high concentrations such as ports, shipping lanes, and marine dredging waste sites. The possible flow of OTCs from marine to terrestrial ecosystems, however, has not been studied. In the present study, the authors assessed whether sediments in common reed beds (Phragmites australis) accumulate TBT and whether chironomid (Diptera: Chironomidae) communities developing in reed-bed sediments act as vectors in the transfer of TBT from aquatic to terrestrial ecosystems in the Airisto channel, Archipelago Sea. The authors also investigated whether distance from the only known source and depth and TBT concentration of the adjacent shipping lane affect reed-bed concentrations. Thirty-six sites along the Airisto channel were sampled at 2-km intervals with triplicate samples from reed beds and the adjacent shipping lane for sediment and seven reed-bed sites for chironomids, and these were analyzed with an solid phase extraction liquid chromatography tamdem mass spectrometry method. The closer to the source the sample site was, the higher the measured TBT concentrations were; and the deeper the shipping lane, the lower the concentration of TBT in reed-bed sediments. The chironomid TBT concentrations correlated with reed-bed sediment TBT concentrations and showed evidence of accumulation. Therefore, TBT may be transferred, through the food web, from aquatic to terrestrial ecosystems relatively close to a source through ecosystem boundaries, such as common reed beds, which are areas of high insect biomass production in the Archipelago Sea.

Sediment organic tin contamination promotes impoverishment of non-biting midge species communities in the Archipelago Sea, S-W Finland

Chironomid species are a vital component in many benthic and terrestrial food webs; they have an important role in the detritus cycle, and are an important source of food for many species. We studied how tributyltin (TBT) in brackish water sediments affect the composition of chironomid species communities. Emergence traps were used at selected sites on a TBT gradient in the Archipelago Sea, S-W Finland. Increased sediment TBT concentration was associated with significant chironomid species turnover, which in turn was related to decreased species diversity (number of species and genera). However, the overall number of individuals did not decrease markedly with increasing TBT contamination. This suggests that the ecological role of chironomids in the food web may be preserved even under severe impoverishment of the chironomid community due to organic tin contamination. The increased prevalence of more TBT tolerant species can potentially lead to a transport of organic tin compounds between aquatic and terrestrial food webs. Furthermore, the reduced diversity of an ecologically influential group might lower the resistance of the entire food web to other environmental hazards and perturbations.

Human exposure, biomarkers, and fate of organotins in the environment

Organotin compounds result from the addition of organic moieties to inorganic tin.Thus, one or more tin-carbon bonds exist in each organotin molecule. The organo-tin compounds are ubiquitous in the environment. Organotin compounds have many uses, including those as fungicides and stabilizers in plastics, among others in industry. The widespread use of organotins as antifouling agents in boat paints has resulted in pollution of freshwater and marine ecosystems. The presence of organotin compounds in freshwater and marine ecosystems is now understood to be a threat, because of the amounts found in water and the toxicity of some organotin compounds to aquatic organisms, and perhaps to humans as well. Organotin com-pounds are regarded by many to be global pollutants of a stature similar to biphenyl,mercury, and the polychlorinated dibenzodioxins. This stature results from the high toxicity, persistence, bioaccumulation, and endocrine disruptive features of even very low levels of selected organotin compounds.Efforts by selected governmental agencies and others have been undertaken to find a global solution to organotin pollution. France was the first country to ban the use of the organotins in 1980. This occurred before the international maritime organization (IMO) called for a global treaty to ban the application of tributyltin (TBT)-based paints. In this chapter, we review the organotin compounds with emphasis on the human exposure, fate, and distribution of them in the environment. The widespread use of the organotins and their high stability have led to contamination of some aquatic ecosystems. As a result, residues of the organotins may reach humans via food consumption. Notwithstanding the risk of human exposure, only limited data are available on the levels at which the organotins exist in foodstuffs consumed by humans. Moreover, the response of marine species to the organotins, such as TBT, has not been thoroughly investigated. Therefore, more data on the organotins and the consequences of exposure to them are needed. In particular, we believe the following areas need attention: expanded toxicity testing in aquatic species, human exposure, human body burdens, and the research to identify biomarkers for testing the toxicity of the organotins to marine invertebrates.

Speciation of butyltin derivatives in surface sediments of three southern Brazilian harbors

For the first time, organotin compounds were determined in surface sediment samples collected from São Francisco do Sul, Itajaí-Navegantes and Imbituba Harbors, located in Santa Catarina State, Brazil. Butyltins (BTs) were determined by gas chromatography with a pulsed flame photometric detector (GC-PFPD) after being modified using the Grignard derivatization method. The concentrations of BTs derivatives ranged from n.d. to 1136.6 ng (Sn) g(-1) of dry weight (dw) sediment for tributyltin (TBT), n.d. to 394.4 ng (Sn)g(-1) dw for dibutyltin (DBT) and n.d. to 312.2 ng (Sn) g(-1) dw for monobutyltin (MBT). The highest concentration of total BTs was found at the Itajaí-Açu River dockyard, indicating intense inputs of antifouling paints to the environment. The relative difference in the BTs levels is a particular characteristic of sediments from harbors and may be related to the shipyards and the boat traffic which still use TBT-based antifouling paints.

Temporal trend of butyltins in seawater, sediments, and mussels from Busan Harbor of Korea between 2002 and 2007: tracking the effectiveness of tributylin regulation

Butyltins were determined in seawater, sediments, and mussels (Mytilus edulis) collected from Busan Harbor, the largest commercial harbor in Korea, to assess the contamination status and the effectiveness of tributylin (TBT) restriction. TBT concentrations were found to be 7.6 +/- 8.3 ng Sn/L in seawater, 387 +/- 606 ng Sn/g dry weight (wt) in sediments, and 322 +/- 167 ng Sn/g dry wt in mussels, and are comparable to those in the largest harbors worldwide. TBT levels were highest at locations near shipyards and related facilities. Busan Harbor was characterized by the long-term history of butyltin contamination, based on the lowered TBT/DBT ratios in environmental matrices. The temporal trend of TBT levels decreased significantly in seawater and mussels from 2002 to 2007, probably as a consequence of the legislative action in Korea (MOE Regulation 154/2000). However, TBT in sediments did not show any trend, suggesting a long half-life for TBT, about 17 years, in sediments.

Distribution of synthetic organotins and total tin levels in Mytilus galloprovincialis along the Portuguese coast

Despite the huge amount of literature available on butyltins (BuTs), few studies addressed the environmental levels of phenyltins (PhTs), octyltins (OcTs) and total tin (Sn(T)) in environmental samples. In 2006 a mussel watch survey was developed for the Portuguese coast (total of 29 sampling sites) in order to describe the concentrations of BuTs , PhTs, OcTs and Sn(T) in the whole tissues of Mytilus galloprovincialis (Lamarck, 1819). BuTs were detected in all analyzed samples accounting, in average, for 98.6% of total organotins (Sigma OTs=BuTs+PhTs+OcTs), and presented highest values in the vicinity of harbors. Tributyltin (TBT) was the dominant butyltin, representing, in average, 62% of summation operatorBuTs (Sigma BuTs=TBT+DBT+MBT) suggesting that fresh inputs of TBT are still occurring in the Portuguese coast, particularly near harbors. The contribution of organotin compounds derived from antifouling paints to the total tin levels in M. galloprovincialis is discussed.

Tributyltin-induced Ca(2+) mobilization via L-type voltage-dependent Ca(2+) channels in PC12 cells

The effects of tributyltin (TBT) on cytosolic Ca(2+) concentration ([Ca(2+)](c)) and cell viability were investigated in nerve growth factor-differentiated PC12 cells. TBT concentration dependently increased [Ca(2+)](c) with an EC(50) value of 0.07μM. This effect was markedly reduced by removal of the extracellular Ca(2+) or membrane depolarization with a high K(+) medium, but unaffected by thapsigargin causing depletion of intracellular Ca(2+) stores. The L-type voltage-dependent Ca(2+) channel (VDCC) blocker nicardipine blocked the effect of TBT, but the N-type VDCC blocker ω-conotoxin did not. TBT decreased the number of viable cells with an EC(50) value of 0.09μM. The TBT-induced cell death was prevented by nicardipine or by chelating the cytosolic Ca(2+) with BAPTA-AM, but not by ω-conotoxin. The results show that TBT causes an increase in [Ca(2+)](c) via activating L-type VDCCs, and support the idea that the organotin-induced cell death arises through Ca(2+) mobilization via L-type VDCCs.

Kinetic degradation processes of butyl- and phenyltins in soils

The degradation of organotin compounds (OTC) in agricultural and forest soils is studied in sandy soil samples. Individual experiments involving the three butyl- and the three phenyltins were carried out during 90 d in controlled conditions (darkness, 28 degrees C, aerobic conditions, 13% moisture) and with spiking concentration representative of environmental levels (20-50 micrg(Sn) kg(-1)). After the validation of first-order degradation kinetic model, mechanisms involved throughout the study were considered. Degradation pathways are proposed for butyl- and phenyltins and discussed according to literature data. The degradation of mono- (MBT, MPhT), di-organotins (DBT, DPhT) and TBT is clearly identified as a single successive loss of an organic group whereas TPhT is directly degraded to MPhT. The half-life times were dependent on their substitution degree, ranging from 24 (TPhT) to 220 (MBT) d. The less substituted the OTC is, the more persistent it is. In the range 4.3-5.7, pH does not seem to influence OTC degradation under the present operating conditions. Finally this study shows the significant persistence in soil samples in our experimental conditions for most of studied organotins and highlights the potential impact on soil quality.

TBT and TPhT persistence in a sludged soil

The persistence of tributyltin (TBT) and triphenyltin (TPhT) in soils was studied, taking into consideration the quantity of sewage sludge, TBT and TPhT concentrations in soil as well as the soil pH. The organotin compounds (OTC) were introduced into the soil via a spiked urban sludge, simulating agricultural practise. OTC speciation was achieved after acidic extraction of soil samples followed by gas chromatography-pulsed flame photometric analysis (GC-PFPD). Leaching tests conducted on a spiked sludge showed that more than 98% of TBT are sorbed on the sludge. TBT persistence in soil appeared to depend on its initial concentration in sludge. Thus, it was more important when concentration is over 1000 microg(Sn) kg(-1) of sludge. More than 50% of the initial TBT added into the soil were still present after 2 months, whatever the experimental conditions. The main degradation product appeared to be dibutyltin. About 90% of TPhT were initially sorbed on sludge, whatever the spiking concentration in sludge was. However, TPhT seemed to be quantitatively exchangeable at the solid/liquid interface, according to the leaching tests. It was also significantly degraded in sludged soil as only about 20% of TPhT remain present after 2 months, the monophenyltin being the main degradation product. pH had a significant positive effect on TBT and particularly TPhT persistence, according to the initial amounts introduced into the soil. Thus, at pH over 7 and triorganotin concentration over 100 microg(Sn) kg(-1), less than 10% of TBT but about 60% of TPhT were degraded. When the sludge was moderately contaminated by triorganotins (typically 50 microg(Sn) kg(-1) in our conditions) the pH had no effect on TBT and TPhT persistence.

Butyltin species in benthic and pelagic organisms of the Saguenay Fjord (Canada) and Imposex occurrence in common whelk (Buccinum undatum)

The distribution and accumulation of butyltins in various tissues of 13 benthic and pelagic species living in the sub-Arctic Saguenay Fjord (Canada) were investigated. Butyltin contamination was ubiquitous in this ecosystem with tributyltin (TBT) biota to sediment accumulation factors (BSAF) ranging between 0.22 and 11, but without any important biomagnification between trophic levels. The large range of butyltin compounds accumulating within different tissues of the species collected from all trophic levels was from 7 to 1238 ng Sn g(-1) d.w. and indicates an exceptional contamination level only found in northern coastal areas exposed to an intensive traffic of commercial ships. Results show that bioaccumulation in organisms depends on three main factors: (1) the actual contamination level in their habitat, (2) their assimilation pathway by water, sediment or diet, and (3) their ability to metabolize TBT and excrete metabolites. By their lack of an efficient TBT degradation system, bivalves are subject to accumulate more butyltins (from 890 to 993 ng Sn g(-1) d.w. for TBT and from n.d to 138 ng Sn g(-1) d.w. for metabolites) whereas most burrow-dwelling organisms are able to degrade TBT and their butyltin levels ranged from 86 to 239 ng Sn g(-1) d.w. for TBT and from 7 to 106 ng Sn g(-1) d.w. for metabolites. Acadian redfish (Sebastes fasciatus) feeding preferentially on shrimps and small crustaceans rich in TBT showed a contamination level about three times higher than eelpout (Licodes vahlii). The latter species living in contact with the sediment and feeding on worms and other burrowing species had a lower proportion of TBT in their tissues. Finally, deleterious effects of butyltins in the Saguenay Fjord were assessed by the significant occurrence of Imposex in common whelk (Bucinum undatum) in two sites from Baie des Ha! Ha!. Results revealed that the effects of Imposex were accentuated close to the source of contamination, at Port-Alfred harbour, since the total of imposexed whelks collected at site A (the mouth of Baie des Ha! Ha!) was 12.5% and reached 52.6% at site B (Port Alfred). Although the incidence or frequency of imposex was low in site A compared to site B, the relative penile length index (RPL) values, a measure of the degree or severity of imposex, was similar at both sites indicating the presence of TBT with higher concentrations in site B.

Butyltin compounds in a sediment core from the old Tilbury basin, London, UK

Sections from a sediment core taken from the River Thames were analysed for butyltin species using gas chromatography with species-specific isotope dilution mass spectrometry. Results demonstrated that in most samples tributyltin concentrations of 20-60 ng/g accounted for <10% of the total butyltin species present, which is in agreement with data from other sediment samples which were historically contaminated with tributyltin. Vertical distribution of the organotin residues with depth throughout the core, with data on organochlorine compounds and heavy metals allowed for the construction of a consistent hypothesis on historical deposition of contaminated sediments. From this it was possible to infer that the concentrations of tributyltin in sediments deposited during the early 1960s were in the order of 400-600 microg/g by using degradation rate constants derived by other workers. Such values fall well within the range quoted for harbour sediments in the literature.

Glutamate Excitotoxicity Is Involved in Cell Death Caused by Tributyltin in Cultured Rat Cortical Neurons

Tributyltin, an endocrine-disrupting chemical, has been used as a heat stabilizer, agricultural pesticide, and component of antifouling paints. In this study, the neurotoxicity of tributyltin was investigated in cultured rat cortical neurons. Tributyltin caused marked time- and dose-dependent increases in the number of trypan blue-stained cells. Measurement of extracellular glutamate concentration showed that glutamate release was induced by tributyltin. Application of the glutamate receptor antagonists MK-801 and CNQX decreased the neurotoxicity. These results suggest that released glutamate and glutamate receptors are involved in tributyltin toxicity. Next, we examined whether various factors, believed to be involved in glutamate excitotoxicity also influence tributyltin toxicity. Cell death induced by tributyltin was found to be reduced by alpha-tocopherol (a membrane-permeable antioxidant), SB202190 (a p38 mitogen-activated protein kinase inhibitor), and U-0126 (an extracellular signal-regulated protein kinase kinase inhibitor). MK-801 and CNQX decreased the phosphorylation of ERK, but not that of p38. A caspase-3 inhibitor had no effect on tributyltin toxicity, and tributyltin did not change the nuclear morphology. These results suggest that the glutamate excitotoxicity caused by tributyltin is unrelated to apoptosis. In conclusion, we demonstrated that tributyltin induced glutamate release and subsequent activation of glutamate receptors, leading to neuronal death. We propose two independent neuronal death pathways by tributyltin; one is glutamate receptor-dependent cell death via ERK phosphorylation, and the other may be glutamate receptor-independent cell death via p38 activation.

Aerobic biodegradation of organotin compounds in activated sludge batch reactors

The biodegradation behavior of four organotin (OT) compounds, namely tributyltin (TBT), dibutyltin (DBT), monobutyltin (MBT) and triphenyltin (TPhT), was studied in lab-scale activated sludge batch reactors. The activated sludge was spiked with the OT compounds at a level of 100 microg l(-1) as Sn. Determination of the OT compounds by GC-FPD after ethylation in the dissolved and particulate phase revealed that 24 h after the start of the experiments, almost the total of OT compounds has been removed from the dissolved phase and is associated with the suspended solids. Calculation of mass balance in batch reactors showed that OT compounds biodegradation was performed via a sequential dealkylation process. Removals due to biodegradation were differentiated according to the parent compound. In experiments with non-acclimatized biomass, a percentage of 27.1, 8.3, 73.8 and 51.3 was still present as TBT, DBT, MBT and TPhT, respectively, at the end of the experiment (18th day). Half-lives (t1/2) of 10.2 and 5.1 days were calculated for TBT and DBT, respectively, whereas apparent t1/2 values could not be determined for MBT and TPhT (t1/2>18 days). The capacity of activated sludge to biodegrade OT compounds in the absence of supplemental substrate indicated that these compounds can be metabolized as single sources of carbon and energy in activated sludge systems. Excluding TBT, the presence of low concentrations of supplemental substrate did not affect the biodegradation potential of activated sludge. The acclimatization of biomass on OT compounds enhanced significantly biodegradation, resulting in significant decreases of half-lives of OT compounds. As a result in the presence of acclimatized biomass, half-lives of 1.4, 3.6, 9.8 and 5.0 days were calculated for TBT, DBT, MBT and TPhT, respectively.

Antiproliferative effect of butyltin in MCF-7 cells

Humans are exposed to tributyltin compounds primarily through the intake of marine food. Previous reports on toxic effects to humans are limited to a few in vitro studies giving conflicting results regarding their effects on the aromatase enzyme and androgen receptor (AR) responses. The present study evaluates the estrogenic potential of three butyltin compounds (mono-, di-, and tributyltin) in an in vitro system based on the E-Screen assay. None of the butyltin compounds tested was estrogenic in the concentration range assayed (0.01-1000 nM). However, both dibutyltin dichloride (DBT) (500 nM) and tributyltin chloride (TBT) (10 nM) inhibited 17beta-estradiol-induced cell proliferation. DBT (500 nM) and TBT (10 nM) also significantly reduced testosterone-induced cell proliferation, and the inhibition by TBT was rescued by increasing the concentration of testosterone. The present study did not confirm the inhibition of aromatase as the mechanism for an endocrine effect of butyltin compounds; moreover, the inhibition of cell proliferation by DBT and TBT occurred at concentrations at which no cytotoxicity was observed. The exact mechanism by which TBT and DBT inhibit cell proliferation remains unexplained, but it might be essentially independent of the estrogen receptor. Therefore, these compounds may not be termed classical endocrine disruptors, but rather as compounds that cause a functional anti-estrogenic response.

Biogeochemistry of organotin compounds and tin in a forested catchment in Germany

Organotin compounds (OTC) are highly toxic pollutants that have been shown to affect many aquatic ecosystems. Little is known about the input and fate of OTC in terrestrial ecosystems. Here, soil pools, concentrations and fluxes in bulk precipitation, throughfall, fog, litterfall and runoff of OTC and Sntotal were investigated in a forested ecosystem (Picea abies, Karst.) in NE Bavaria, Germany. The concentrations of OTC and Sntotal were generally in the order fog>throughfall>bulk precipitation. Average concentrations of OTCtotal ranged from 57 ng Sn l(-1) in fog to 5.8 ng Sn l(-1) in bulk precipitation. Concentrations of Sntotal were in the same order but between 490 ng Sn l(-1) in fog and 140 ng Sn l(-1) in bulk precipitation, on average. Average OTCtotal concentrations in litterfall were 12.9 ng Sn g(-1) and those of Sntotal in litterfall 38 ng Sn g(-1). All OTC concentrations in runoff were lower than in bulk precipitation, while those of Sntotal were similar to the concentrations in bulk precipitation. Monobutyltin was the dominating OTC in bulk precipitation, throughfall, fog and litterfall, but was seldom detected in the runoff. The annual total deposition of OTCtotal (calculated as throughfall + litterfall) was 172 mg Sn ha(-1) year(-1), with 45 mg Sn ha(-1) year(-1) represented by litterfall. The annual runoff from the catchment of OTCtotal amounted to 25 mg Sn ha(-1) year(-1). The total deposition of Sntotal was 4.9 g Sn ha(-1) year(-1), of which 0.2 g Sn ha(-1) year(-1) was litterfall. The annual runoff of Sntotal was 2.4 g Sn ha(-1) year(-1). The mass balance showed a high retention of OTC and Sntotal in the catchment. The forest soils act as a strong sink for OTC and Sntotal. Only small amounts of deposited OTC are released to runoff. The ratio of soil pools to annual accumulation for total OTC (46 years) indicates that OTC inputs have been occurring already for many decades or have been substantially higher in the past than today.

Contamination and Biomethylation of Organotin Compounds in Pearl/Fish Culture Areas in Japan

Uwakai of Japan is famous for pearl and yellowtail fish culture. Recently, pearl culture farming in that region has suffered from a low production of pearls. An illegal use of organotin antifouling paints on fishing nets was reported. In the line of pollution studies, thus, the present investigation was carried out to examine the contamination status and fate of organotin compounds. Totally, 23 water, 10 sediment and 8 pearl oyster tissue samples were analyzed for tributyltin (TBT), triphenyltin (TPT), and their breakdown products (di- and mono compounds) by gas chromatography combined with inductively coupled plasma mass spectrometry (GC/ICP-MS). The results show that the TBT concentrations in water, sediment and biota were in the range from 0.11 to 10.6 ng Sn l(-1), 0.35 to 2500 ng Sn g(-1), and 50.4 to 181 ng Sn g(-1), respectively. The values for sediment and biota are expressed on the dry-weight basis. Triphenyltin in water, sediment and biota were in the range from 0.009 to 0.108 ng l(-1), non-detect to 12.7 ng g(-1), and non-detect to 6.83 ng g(-1), respectively. Although the TBT concentration in seawater is below the tentative assessment level of 10 ng l(-1) set by the Japanese Environment Agency in 1992, it may cause endocrine disruption/other effects in aquatic organisms. Octyltin compounds (mono-, di- and trioctyltin) were also quantified in seawater and sediment. The detection of dibutyldimethyltin (DBDMT) and tributylmonomethyltin (TBMMT) in sediment (methylated butyltins comprised 2.8-31% of total butyltins), and TBMMT in seawater suggested that biomethylation of anthropogenic tributyltins is a significant transformation pathway in the coastal environment.

Sorption of tributyltin onto a natural quartz sand

The aim of this study is to understand the sorption of tributyltin (TBT) onto natural quartz sand by classical batch experiments and spectroscopic surface analyses. At pH<6, the major species of TBT is the cation TBT(+). Due to the presence of both the cationic part and the butyl chains, TBT should present amphiphilic properties. For concentrations lower than 40 microM, TBT sorption occurs as a homovalent 1:1 cation exchange between either H(+) or Na(+) and TBT(+). The increasing affinity of TBT with respect to the different materials follows the series kaolinite<<natural sand<treated sand<pure quartz. From XPS analyses, where the chemical environment of Sn did not change, indicating possible complete reversibility of the TBT sorption, it seems that inner-sphere surface complexes could be formed due to the increase in the 3d-level binding energy. At TBT concentrations higher than 100 microM, we showed by flotation experiments and XPS analysis that the surface becomes hydrophobic. After one monolayer was formed, the TBT sorption could thus be due to hydrophobic interaction between the butyl chains of the sorbed TBT and those of the TBT still available from the bulk solution. This mechanism is consistent with surface condensation and the shape of the sorption isotherm.

Dithioerythritol (DTE) prevents inhibitory effects of triphenyltin (TPT) on the key enzymes of the human sex steroid hormone metabolism

Organotins are known to induce imposex (pseudohermaphroditism) in marine neogastropods and are suggested to act as specific endocrine disruptors, inhibiting the enzyme-mediated conversion of steroid hormones. Therefore, we investigated the in vitro effects of triphenyltin (TPT) on human 5alpha-reductase type 2 (5alpha-Re 2), cytochrome P450 aromatase (P450arom), 17beta-hydroxysteroid dehydrogenase type 3 (17beta-HSD 3), 3beta-HSD type 2 and 17beta-HSD type 1 activity. First, the present study demonstrates that significant amounts of TPT occurred in the blood of eight human volunteers (0.17-0.67 microg organotin cation/l, i.e. 0.49-1.92 nmolcation/l). Second, TPT showed variable inhibitory effects on all the enzymes investigated. The mean IC(50) values were 0.95 microM for 5alpha-Re 2 (mean of n=4 experiments), 1.5 microM for P450arom (n=5), 4.0 microM for 3beta-HSD 2 (n=1), 4.2 microM for 17beta-HSD 3 (n=3) and 10.5 microM for 17beta-HSD 1 (n=3). To exclude the possibility that the impacts of TPT are mediated by oxidizing essential thiol residues of the enzymes, the putative compensatory effects of the reducing agent dithioerythritol (DTE) were investigated. Co-incubation with DTE (n=3) resulted in dose-response prevention of the inhibitory effects of 100 microM deleterious TPT concentrations on 17beta-HSD 3 (EC(50) value of 12.9 mM; mean of n=3 experiments), 3beta-HSD 2 (0.90 mM; n=3), P450 arom (0.91 mM; n=3) and 17beta-HSD 1 (0.21 mM; n=3) activity. With these enzymes, the use of 10mM DTE resulted in an at least 80% antagonistic effect, whereas, the effect of TPT on 5alpha-Re 2 was not compensated. In conclusion, the present study shows that TPT acts as an unspecific, but significant inhibitor of human sex steroid hormone metabolism and suggests that the inhibitory effects are mediated by the interaction of TPT with critical cysteine residues of the enzymes.

Determination of methylmercury and butyltin compounds in marine biota and sediments using microwave-assisted acid extraction, solid-phase microextraction, and gas chromatography with microwave-induced plasma atomic emission spectrometric detection

A method is described for the determination of methylmercury and butyltin compounds in marine sediment and tissue using microwave-assisted acid extraction or digestion and solid-phase microextraction (SPME) followed by analysis using gas chromatography with microwave-induced plasma atomic emission spectrometric detection (GC-MIP-AES). Using the SPME-GC-MIP-AES method, enrichment factors for methylmercury and butyltin compounds of 50-100 were achieved, as compared to the typical hexane extraction, and measurements in marine tissue and sediment matrixes were possible at 1-2 microg/kg (methylmercury) and 10-100 ng/kg (butyltins). The SPME-GC-MIP-AES method was validated using several marine sediment and tissue matrix certified reference materials (CRMs) with certified values for methylmercury and butyltin compounds. The SPME-GC-MIP-AES method was used to measure methylmercury in four marine tissue CRMs ranging from oyster tissue at 13.0 +/- 1.0 microg/kg to fish tissue at 397 +/- 13 microg/kg (as Hg dry mass). Results from the SPME-GC-MIP-AES method were used in conjunction with results from other techniques to assign certified values for methylmercury in oyster, mussel, and fish tissue CRMs. Mono-, di-, and tributyltin were measured in three sediment CRMs at concentration levels of (0.08 +/- 0.03)-(0.35 +/- 0.05) mg/kg (as Sn dry mass).

Organotin contamination in sediments from the Western Mediterranean enclosures following 10 years of TBT regulation

Organotin (OT) compounds, namely butyl and phenyl, were measured in 38 recent sediments collected in harbours of the Western Mediterranean Sea (Northern: 4 and Southern: 9) and domestic and industrial sewage disposal sites (Northern: 9 and Southern: 1). Butyltins were the predominant tin species identified as being tributyltin (TBT) widespread in the whole area which suggests recent inputs of OTs. The highest levels of TBT were detected in commercial harbours associated with inputs from large vessels (average value: 5.0 microg TBT g(-1). Moreover, relatively high TBT values were also detected in fishing and recreational boating areas (average level ca. 1.0 microg TBTg(-1)). Phenyltin derivatives occurred at lower levels than butyltins being the monophenyltin the predominant compound (average values 45-945 ng g(-1)). The large predominance of the phenyltin degradation products (i.e. mono and diphenyltin) over the parent compound (i.e. triphenyltin) suggests that there are almost no recent inputs of these compounds. Furthermore, a comparative study of the OT occurrence in the sewage sludge disposal sites offshore Barcelona and Almeria (domestic) and into the Tarragona harbour (industrial) shows that domestic primary sewage sludge effluents can contribute to coastal OT pollution (244ng TBT g(-1)). Nevertheless, sewage sludge is a secondary source of OT contamination in the coastal environment in comparison to commercial harbours. In a comparative study with previous data collected in the late 1980s, the present study reveals that OT regulations established in the Mediterranean region in 1991 on the use of TBT-based antifouling paints have been effective in marinas, but reveals a significant TBT contamination in commercial and fishing harbours.

Butyltin compounds in human liver

Intake of marine food is the main source of butyltin exposure in humans. Health effects following exposure to butyltin compounds are usually in the immune system, but endocrine effects of butyltin from a variety of marine species have been documented. The information on human exposure to butyltin compounds and hepatic deposition is limited. The present study include 18 consecutively sampled human livers analyzed for butyltin compounds. Dibutyltin (DBT) concentrations varied between 0.8 and 28.3 ng/g with a mean concentration of 9.0 ng/g. Significantly lower concentrations of monobutyltin (MBT) were observed, ranging from 0.3 to 4.7 ng/g with a mean value of 1.6 ng/g. Age and DBT/MBT ratio were significantly associated. We suggest that younger men have more recent exposures or have a lower capacity to debutylate DBT than older men and would therefore potentially be more susceptible to butyltin toxicity. Given the interperson variability observed in our limited group of men, we cannot exclude that thresholds for either immunotoxicity or effects on the endocrine system may occur due to exposure to butyltin compounds alone or in combination with other environmental toxicants with similar target organs.

Status of persistent organic pollutants in the sediment from several estuaries in China

Sediment samples from three estuaries on the east coast of China were analyzed for persistent organic pollutants. Total PCB, PAH, and DDT concentrations in the sediments from Minjiang, Jiulongjiang, and Zhujiang estuaries ranged from 2 to 14 ng/g, 400 to 1500 ng/g, and 6 to 73 ng/g, respectively, in the sediments from these estuaries. The sources of PAH contamination were inferred from PAH compositions, with pyrogenic PAHs being the dominant source for Minjiang Estuary and petroleum related PAHs being the primary contributors to Jiulongjiang and Zhujiang estuaries. The high concentrations of DDT in the sediments from these estuaries were likely the result of widespread use of DDT in China in the 1960s and 1970s. Butyltin compounds were detected in the sediment from Jiulongjiang Estuary and Victoria Harbor, Hong Kong. Presence of butyltin compounds probably result from the shipping activities in these estuaries. Butyltin compounds were not detected in the sediments from Minjiang and Zhujiang estuaries. Contaminant concentrations were generally below levels expected to affect benthic organisms with the exception of DDTs.

Temporal fluctuations of tributyltin in the bivalve Venerupis decussata at five stations in southwest Spain

Filter feeding clams, Venerupis decussata, were sampled every 4 months for 8 years at five locations on the southwest Spain coast and analysed for organotins. All the stations showed a significant sinusoidally shaped seasonal evolution pattern for tributyltin (TBT) superimposed upon a linear decreasing tendency. The amplitude and frequency of fluctuations differed among stations and were correlated to the harbour activities. Fluctuations were greatest at stations with the greatest TBT presence. The long-term trend of TBT in clams indicated half-life values of about 7-14 years. During 1993, water and sediment samples were also collected at monthly intervals and analysed. Correlations between TBT bivalve contents and water concentrations were higher than those found between biota and sediments.