Butyltin Concentrations Research Articles

Accumulation of butyltin and phenyltin compounds in various fish species.

Concentrations of organotins (OTs) were measured in the muscle of 11 species of fishes from the Port of Osaka and Yodo River, Japan. Tributytin (TBT) and triphenyltin (TPT) compounds were detected in the range of 0.011-0.182 mg/kg wet weight and < 0.001-0.130 mg/kg wet weight, respectively. Concentrations of TBT were higher than those of TPT in the muscle of fish. Concentrations of OTs in fish from sea areas were higher than those from rivers, and the ratios of TBT to total butyltins (BTs) in fish from sea areas were also higher than those from rivers. A similar trend was found for TPT. Logarithm of bioconcentration factor (BCF) of TBT in fish was in the range of 2.7-3.9. No sex differences in TBT and TPT concentrations in Japanese sea perch were observed, and the concentrations of TBT and TPT were not related to total length of fish. No correlation was also observed between the concentration of TBT or TPT and lipid content. The concentrations of BTs and phenyltins (PTs) in organs and tissues of three fish species were determined. TBT was higher concentration in liver, brain, and muscle of white croaker and yellowtail. The ratios of TBT to the total BTs were 30-40%, and the ratios of TPT to total PTs in these fishes were greater than 50% of the total PT concentrations.

Problems associated with an environmental assessment of organotins: Application to the organic polluted saladillo harbor (southern Spain)

AbstractProblems associated with assessing the environmental effects of organotin (OT) include extraction efficiency, whether to filter the water samples, effect of grain size of sediments, and mobility characteristics of OT species from sediments. This study considered these effects on the six OT species tributyltin, dibutyltin, monobutyltin, triphenyltin, diphenyltin, and monophenyltin in seawater and sediments collected from Saladillo Harbor, a representative enclosed area in southern Spain that receives inputs of both OTs and organic matter. Yields of organotin extracted from sediments with a high organic content by using dichloromethane were higher than those obtained by using pentane. Concentrations of butyltins were higher than those of phenyltins. A gradient was observed of decreasing butyltin concentrations in sediments from 280 ng Sn/g in the inner stations to 0.5 ng/g in the outer stations of the harbor. No dissolved organotin compounds were detected in the overlying seawater. Because OTs are related to the presence of organic matter, iron oxyhydroxides, and phylosilicates, they were strongly adsorbed onto particulate matter in both sediment and suspended matter. Low percentages of butyltins, ranging from undetectable to 0.54%, were released by extracting in unpolluted seawater at pH 8 and 5. Higher concentrations were found in finer sediments.

Hepatic butyltin concentrations in beluga whales (Delphinapterus leucas) from the St Lawrence Estuary and northern Quebec, Canada

Butyltin (tributyltin TBT; dibutyltin DBT and monobutyltin MBT) speciation was measured in the liver of beluga whales from the St Lawrence Estuary and Hudson Strait (northern Quebec). Using GC–MS, liver samples were analysed from 21 beluga whales found dead, stranded along the shores of the St Lawrence during the period 1995–1998. In all cases, including a neonate specimen, the liver was contaminated with butyltin compounds with concentrations in the range 0.04–2.1 mg Sn kg−1 on a dry weight basis. Liver samples of five beluga whales from Hudson Strait obtained in the summer of 1998 were also analysed. For these animals, hepatic butyltin concentrations were consistently below the detection limit (<0.5 ng Sn g−1 for MBT and <0.2 ng Sn g−1 for DBT and TBT). Compared with published data on the contamination by TBT of the marine mammals of the St Lawrence in 1988, these contemporary results clearly indicate that the level of contamination of the beluga whales in this coastal marine ecosystem has not decreased ten years after regulating the use of TBT-based antifoulants on small craft. Copyright © 2000 John Wiley & Sons, Ltd.

Hepatic butyltin concentrations in beluga whales?(Delphinapterus leucas) from the St Lawrence Estuary and northern Quebec, Canada

Butyltin (tributyltin TBT; dibutyltin DBT and monobutyltin MBT) speciation was measured in the liver of beluga whales from the St Lawrence Estuary and Hudson Strait (northern Quebec). Using GC–MS, liver samples were analysed from 21 beluga whales found dead, stranded along the shores of the St Lawrence during the period 1995–1998. In all cases, including a neonate specimen, the liver was contaminated with butyltin compounds with concentrations in the range 0.04–2.1 mg Sn kg−1 on a dry weight basis. Liver samples of five beluga whales from Hudson Strait obtained in the summer of 1998 were also analysed. For these animals, hepatic butyltin concentrations were consistently below the detection limit (<0.5 ng Sn g−1 for MBT and <0.2 ng Sn g−1 for DBT and TBT). Compared with published data on the contamination by TBT of the marine mammals of the St Lawrence in 1988, these contemporary results clearly indicate that the level of contamination of the beluga whales in this coastal marine ecosystem has not decreased ten years after regulating the use of TBT-based antifoulants on small craft. Copyright © 2000 John Wiley & Sons, Ltd.

The use of Nucella lapillus (L.) transplanted in cages to monitor tributyltin (TBT) pollution

Specimens of the gastropod Nucella lapillus were transplanted from their natural habitat to sites affected by tributyltin (TBT) pollution to diverse degrees; individuals were held in cages that also included mussels as food. Subsamples were taken from the cages and the natural site at different time intervals (1, 2 and 5 months) to compare growth, imposex (a set of sexual anomalies caused by TBT) and butyltin concentrations accumulated in female tissues. Individuals in cages experienced negligible mortality and considerable growth. In addition, while the Relative Penis Size Index (RPSI, an index of imposex) remained consistent in the natural site through the experiment, it increased markedly at the implant sites; the same applies to the butyltin residues. These results are discussed to conclude that cage transplanting of N. lapillus is a suitable technique that can quickly (i.e. 1 month) detect differences in the level of TBT contamination among sites; however, extrapolation of experimental results to the field seems to require a longer exposure time (at least 5 months). Finally, the use of such an approach is deemed helpful to interpret the relationship between N. lapillus population dynamics and TBT pollution.

Accumulation of butyltin compounds in dolphins stranded along the Mediterranean coasts

Concentrations of tributyltin (TBT) and its degradation products, monobutyltin (MBT) and dibutyltin (DBT), were determined in the liver and kidney of striped dolphins ( Stenella coeruleoalba), bottlenose dolphins ( Tursiops truncatus) and in a fetus of the common dolphin (Delphinus delphi) found stranded along the western Italian and Greek coasts in the period 1992‐1994. Butyltin (BT) compounds were detected in almost all the samples analyzed and were higher in the kidney than in the liver. Total BT concentrations were 0.78‐8.05m gg ˇ 1 wet wt in kidney and 0.015‐1.02m gg ˇ 1 wet wt in liver of S. coeruloealba. Bottlenose dolphins had lower BT concentrations than striped dolphins. Although only one fetal sample was analyzed, it showed the highest BT concentrations of all. Unlike BT concentrations in the other adult dolphins, in the pregnant dolphin they were higher in the liver (4.35 m gg ˇ 1 wet wt), suggesting that BTs are transferred from mother to fetus. No significant differences in BT concentrations were found between sexes. Of the breakdown products, DBT was predominant in most liver samples and MBT was more abundant in kidney. Although BT concentrations are known to be found in cetaceans inhabiting waters of developed countries, our observations strongly suggest that concentrations found in S. coeruleoalba were either similar to or higher than those reported for other Stenella species collected from coastal areas close to harbors or marinas. Copyright # 2000 John Wiley & Sons, Ltd.

Unregulated use of TBT-based antifouling paints in Israel (eastern Mediterranean):high contamination and imposex levels in two species of marine gastropods

The use of tributyltin (TBT)-based antifouling paints is unregulated in Israel, and levels of contamination are high along the Mediterranean coastline there. This is indicated by concentrations of butyltins found in the tissue, and by imposex in the whelks Stramonita haemastoma and Hexaplex trunculus. Both the old (since 1974) and new (since late 1995) marinas we studied are hotspots of pollution. Imposex indices were very high at the old marina (RPSI > 100, VDSI 4 to 5); all female H. trunculus and some S. haemastoma were sterile within a distance of ca 1 km from it. The new marina offered a unique opportunity to witness the rapid and intense response of the whelks to TBT pollution in an open coastline. Despite a marked decrease in levels of contamination at distances of 1 to 2 km from both marinas, there were nevertheless detectable levels of butyltins sufficient to cause imposex in reference sites far from high shipping activity. There is evidence that TBT contamination affects abundance and relative growth rates, of male and female, of the 2 whelks around the marinas. Differences in biological response to TBT were observed between the 2 whelk species: S. haemastoma had higher levels of organotins than H. trunculus in most study sites, which may be related to different sensitivity or accumulation rates. In S. haemastoma a male-biased sex ratio was revealed around the old Tel Aviv marina, which may be derived from either female mortality or from a complete sex change in some females. Further development of marinas at coastal resorts is undesirable, certainly in the absence of regulations limiting the use of TBT-based antifoulants, and the establishment of such regulations is highly recommended.

Mussel watch: marine pollution monitoring of butyltins and organochlorines in coastal waters of Thailand, Philippines and India

Contamination by butyltin (BTs) and organochlorine compounds (OCs) in green mussels collected along the coastal areas of Thailand, Philippines and India during the period of 1994–1997 was examined. The BT residues in green mussel were widely detected, suggesting a widespread contamination along the coastal waters of Asian developing countries. Relatively high concentrations of BTs in green mussel were found in high boating activity and coastal aquaculture areas, implying the usage of TBT as a biocide in antifouling paints used on boat hulls and marine aquaculture facilities. The composition of BT derivatives in mussel was in the order of TBT>DBT>MBT, suggesting also the presence of significant butyltin source in Asian coast. BT residues pattern in green mussels from Thailand revealed higher levels in aquaculture than in boating activity sites. This result may indicate that the developing countries showing high economic growth rate (like Thailand) tend to increase the usage of TBT for aquaculture activities. BT contamination levels in Asian developing countries were lower than those in developed nations. However, considering the fact that the unregulated usage of organotins in Asian developing countries and the increasing demand for antifouling paints in Asia–Pacific regions, BTs contamination in aquatic environment may be serious in future. Concentrations of OCs detected in green mussels were lower than BTs. Considerable residues of p, p′ -DDT found in mussel indicated the current usage of DDTs in Asian regions. HCHs and DDTs contamination in India is apparently higher than in other Asian developing countries. The present study clearly indicates that the aquatic environment in Asia–Pacific regions is still being contaminated by some OCs. To our knowledge, this is a first report on the detection of butyltin compounds in green mussels ( Perna viridis) from Thailand, Philippines and India.

Occurrence of butyltin residues in sediment and mussel tissues from the lowermost tennessee river and Kentucky lake, U.S.A.

Surface sediments and mussel samples were collected at six selected locations in the lowermost Tennessee River and Kentucky Lake, U.S.A. and analyzed for butyltin (BT) derivatives. In sediments, total BT concentrations ranged from 6.8 to 356 ng g −1 dry wt. A wide range of concentrations in sediments suggested the presence of localized area of contamination. In mussel tissues, total BT concentrations varied between 26–107 ng g −1 dry wt. BT levels were comparable to the levels reported in mussels from some coastal sites as well as a few freshwater ecosystems. Leaching of tributyltin-containing anti-fouling paints in the ocean-going ships is a source of tributyltin, and discharge of municipal sewage and industrial waste waters in to this watershed may account for the presence of the monobutyltin and dibutyltin derivatives detected in the samples. To our knowledge, this is the first report on the butyltin concentrations in sediment and mussel tissues from the lowermost Tennessee River and Kentucky Lake.

Butyltin compounds in sediment and fish from the Polish Coast of the Baltic Sea.

Concentrations of mono- (MBT), di- (DBT), and tri-(TBT) butyltin compounds were measured in eggs, liver, and muscle of nine species of fish from four regions of the Baltic Sea - the Firth of Vistula, the Gulf of Gdańsk, Puck Bay, and the mouth of the Vistula River. The overall concentration ranges among all the fish sampled from the four sites were: < 7 to 79 ng/g for MBT, 6 to 1100 ng/g for DBT, 7 to 3600 ng/g for TBT, and 16 to 4800 ng/g for total BTs, on a wet wt basis. The highest concentration of total BTs was found in herring liver from the Firth of Vistula (4800 ng/g, wet wt) and in roach muscle from Puck Bay (3300 ng/g, wet wt), while the least concentration was found in burbot eggs and liver from the Vistula River (39 and 32 ng/g, wet wt, respectively). TBT was the major form of BTs present in most samples analyzed. Sediment samples collected from shipyards in the Gulf of Gdańsk contained butyltin concentrations ranging from 1.2 to 46 microg/g (dry wt) for MBT, 2.0 to 42 microg/g for DBT, and 2.6 to 40 microg/g for TBT. As with the fish, the majority of the BTs in sediment were present as TBT, which suggested recent exposure of the aquatic environment of the region to TBT.

Accumulation of Butyltins in Sediments and Lipid Tissues of the Asian Clam, Potamocorbula amurensis, Near Mare Island Naval Shipyard, San Francisco Bay

Studies of butyltin compounds in soil, benthic sediments and the Asian clam Potamocorbula amurensis were conducted at the former Mare Island Naval Shipyard, and nearby Mare Island and Carquinez Straits in San Francisco Bay, California. Soils from a sandblast abrasives dump site at the shipyard contained low concentrations of mono-, di- and tributyltin (0.3–52 ng/g, total butyltin). Similarly, concentrations of total butyltin in benthic sediments from nearby Mare Island and Carquinez Straits ranged from 1.3 to 8.1 ng/g. In contrast, clams accumulated much greater concentrations (152–307 ng/g, total butyltin). Tributyltin (TBT) and dibutyltin (DBT) made up from 54–85% to 15–46%, respectively, of the total butyltin body burden of the clams. Biota Sediment Accumulation Factors (BSAFs) for butyltins in Potamocorbula were in reasonable agreement with literature values; they are greater than those of neutral hydrophobic compounds, suggesting that partitioning and binding processes may be involved in bioaccumulation. Tributyltin is a potent endocrine disrupting chemical. There is potential for long-term chronic effects of TBT in San Francisco Bay.

Immunotoxicity of Environmentally Relevant Concentrations of Butyltins on Human Natural Killer Cells in Vitro

The widespread environmental contamination, bio-accumulation, and toxic effects of butyltins (BTs) in wildlife is well documented, but the role of BTs in debilitating human immune function mediated through natural killer (NK) lymphocytes (a primary immune defense against tumor and virally infected cells) has not been described. In this study, we assessed the effects of in vitro exposure to a range of concentrations (encompassing environmentally relevant concentrations) of MBT, DBT, and TBT on human natural killer lymphocytes obtained from adult male and female donors. TBT inhibited the tumor-killing capacity of NK cells when the NK cells were pretreated in vitro at 200 nM for as little as 1 h. Inhibition of NK cytotoxic function ranged from 40 to greater than 90%. The toxic potential of butyltins followed the order of TBT > DBT > MBT. Conjugation assays revealed that after a 24-h exposure to TBT, there was about a 50% decrease in NK cell binding to tumor cells, indicating alteration of the NK cell receptors for tumor cells. Analysis of whole-blood samples for BTs revealed the presence of detectable concentrations of MBT, DBT, and TBT in all of the donors, indicating possible exposure of NK cells to BTs in the blood. The results of this study provide evidence that butyltin compounds significantly inhibit NK cell function and possible NK cell-mediated immunotoxic potential in humans.

Horizontal distribution of butyltins in surface sediments from an enclosed bay system, Korea

Tributyltin (TBT), dibutyltin (DBT), and monobutyltin (MBT) compounds were quantitatively determined from surface sediment samples (total 59 stations) covering a whole basin where harbors, shipyards, and aquaculture farms were located. Butyltin compounds were detected from all the stations covering 640 km2 of an enclosed bay system. TBT concentrations ranged from 4 to 382 ng/g as tin on a dry weight basis, and total butyltin concentrations, from 27 to 1763 ng/g. Horizontal distribution of TBT concentration showed apparent negative gradients from harbors and shipyards, indicating that its contamination was closely related to boating and dry-docking activities. However, TBT concentrations were decreased steeply from source areas. Elevated DBT and MBT levels in creeks imply the possible input of DBT from industrial wastewater. Total butyltin concentrations in sediments are significantly correlated with particulate organic carbon concentration for the subset of stations that are distant from source areas.

Occurrence of Butyltin Compounds in Human Blood

Residues of butyltin compounds, including mono- (MBT), di- (DBT) and tributyltins (TBT), were measured in human blood collected from central Michigan, U.S.A. MBT, DBT, and TBT were detected in 53, 81, and 70% of the 32 blood samples examined. Concentrations of butyltins were in the order of MBT > DBT ≥ TBT, with total butyltin concentrations ranging from less than the limit of detection to 101 ng/mL. Exposure of humans to butyltin compounds used as stabilizers or as biocides in household articles has been regarded as a source in addition to the ingestion of contaminated foodstuffs. There was no significant difference in concentrations of butyltin compounds between sexes. Concentrations of butyltin compounds did not exhibit pronounced age-dependency, which is different from those observed for persistent pollutants such as polychlorinated biphenyls (PCBs). In general, concentrations of butyltins measured in blood were less than that affected human natural killer lymphocytes (a primary immune defense against...

Butyltin Concentrations in Sediments and Blue Mussels (Mytilus edulis) of the Southern Gulf of St. Lawrence, Canada

Profiles of the butyltins tributyltin (TBT) and dibutyltin (DBT) in sediments were obtained in 1996 from four sites frequented by commercial and/or recreational ships in the southern Gulf of St. Lawrence: Summerside (Prince Edward Island, PEI), Pictou (Nova Scotia, NS), Miramichi (New Brunswick, NB), Shediac (NB) and one reference site: Cardigan (PEI). Sediments from Shediac and Summerside were the most contaminated with both TBT and DBT showing in the surficial sediments levels reaching 83.4 ng Sn g−1 (d.w.) for Shediac. Seasonal monitoring of levels of TBT and DBT in wild blue mussels, Mytilus edulis, was also conducted at these same sites in 1995 and 1996 with the addition of a second reference site in 1996 - Richibucto (NB). Mussels from all sites, except Richibucto, were contaminated by TBT at levels ranging from 7 ng Sn g−1 (d.w.) in Cardigan to 426 ng Sn g−1 (d.w.) in Summerside in 1995 and from below the detection limit in Richibucto to 671 ng Sn g−1 (d.w.) in Summerside in 1996. DBT was also present in most samples at concentrations reaching 161 ng Sn g−1 (d.w.) in 1995 and 378 ng Sn g−1 (d.w.) in 1996 in samples from Summerside. The highest levels correspond to moderately high contamination with the potential of causing deleterious effects in biota. In most sampling sites, no clear relationship could be established between butyltin concentrations found in sediment and in mussels. Our results suggest that inputs of TBT from June to September, at least in the southern Gulf of St. Lawrence, are still well above expected levels after eight years of TBT-paint regulation. The main source would appear to be pleasure boating activities with a lower but chronic contribution from the commercial fleet.

Butyltin compounds in river otters (Lutra canadensis) from the northwestern United States.

Butyltin compounds, including mono-, di-, and tributyltin (MBT, DBT, and TBT) were measured in livers of 40 adult river otters (Lutra canadensis) collected from rivers and coastal bays in Washington and Oregon, USA. Butyltins were found in all the river otters, at a concentration range of 8.5-2,610 ng/g, WW. The greatest concentration of total butyltins of 2,610 ng/g, WW, was found in a river otter collected in Puget Sound from Fort Ward, Washington. River otters collected near areas with major shipping activities, such as the Puget Sound, contained significantly greater concentrations (geometric mean: 367 ng/g, WW) of butyltins than those from rivers. Among butyltin compounds, MBT and DBT predominated in livers. The concentrations of butyltins in river otters ranged from comparable (Puget Sound) to less (rivers) than what was found in coastal cetaceans.

Butyltin Contamination in Marine Mammals – A Review

In order to understand organotin accumulation in marine mammals, the present study determined the concentrations of butyltins (BTs) in various tissues and organs and described their distribution patterns relative to sex, age and geographical factors. Both cetaceans and pinnipeds showed higher BTs concentrations in the liver amongst various tissues and organs. In addition, noticeably high concentrations were found in the hair of pinnipeds, indicating possible excretion of BTs through shedding. BTs composition in mammals and their prey organisms suggested that pinnipeds have a stronger capacity to degrade BTs as compared to cetaceans. No age trends of BTs concentrations were observed in pinnipeds, while cetaceans showed increasing levels in immature growth stages. Comparing butyltin concentrations in various marine mammals, cetaceans retained higher butyltin concentrations than pinnipeds. These specific accumulation patterns found in marine mammals are probably attributable to the lower breakdown capacity of BTs in cetaceans and the significant excretion of BTs through shedding in pinnipeds. Unlike organochlorines, comparable residue levels of butyltins were found in male and female marine mammals. Such a trend suggests that butyltins are less transferable through gestation and lactation from mother to fetus/pup. On a global perspective, residue levels were found to be prominent in the coastal waters of developed nations. The present contamination by BTs may pose a considerable toxic threat to some coastal species of cetaceans. A relatively high percentage of BTs in total tin was found in the liver of cetaceans. This finding suggests that the hepatic tin in cetaceans exists predominantly in organic forms such as butyltin compounds, implying further that tin residues in marine mammals mostly reflects input from anthropogenic sources.

Imposex in Morula Granulata as Bioindicator of Tributyltin (TBT) Contamination in the Dampier Archipelago, Western Australia

This study was undertaken to examine the use of imposex in the tropical neogastropod whelk Morula granulata as bioindicator of tributyltin (TBT) contamination. Samples were collected from sites throughout the Dampier Archipelago; both impact sites close to intensive shipping activity and remote control sites. TBT in this area originates mainly from commercial vessels using the Port of Dampier that are >25 m in length and exempt from legislation controlling the use of TBT in antifouling paints. A field survey was undertaken in July 1997; 100 M. granulata were taken at each of 18 sites with varying vessel activity, and examined for imposex. The level of TBT contamination in the Archipelago was low; ranging from <0.3 to 25 ng Sn l −1 in water,<0.3 to 80 ng Sn g− 1 in oyster tissue ( Saccostrea cuccullata – prey of M. granulata), and <0.3 to 33 ng Sn g −1 in whelks. Percentage of imposex in M. granulata ranged from 0% to 57%, and was correlated with distance to vessel activity ( r=0.646, p<0.05). The only significant relationship of imposex with butyltin concentrations was with TBT in oysters ( r=0.826, p<0.05), and dibutyltin (DBT) in whelks ( r=0.783, p<0.05). It is postulated that this is because of interspecies variation in ability to metabolize TBT to DBT and MBT (monobutyltin), as well as induction of imposex in earlier life stages, so that imposex in adults could be a reflection of prior contamination. M. granulata is a suitable bioindicator of TBT contamination in the Dampier Archipelago, which could be used throughout the Indo-Pacific given its abundance in the region.

Galveston Bay: Temporal Changes in the Concentrations of Trace Organic Contaminants in National Status and Trends Oysters (1986-1994)

The temporal distributions for six classes of trace organic contaminants (chlordanes, DDTs, dieldrin, PAHs, PCBs, and butyltins) in oysters from six Galveston Bay sites from National Oceanic and Atmospheric Administration’s National Status and Trends (NS&T) Mussel Watch Program are compared with other NS&T sites from the Gulf of Mexico as well as all NS&T sites of the United States (East Coast, West Coast, and Gulf of Mexico). Decreases in the median for the Gulf-wide concentration of chlordanes, dieldrin, and butyltins occurred during 1986–1994. The Gulfwide median concentrations of DDTs, PAHs, and PCBs exhibited a strong cyclic distribution with time. For Galveston Bay oysters, “high” concentration is defined as the concentration greater than the median plus one standard deviation for all Gulf of Mexico sites. The percentage of sites having high concentrations during 1986–1994 for Galveston Bay oysters are 49% for dieldrin, 45% for butyltins, 40% for chlordanes, 38% for PCBs, 30% for PAHs, and 21% for DDTs. For PCBs, 43% of Galveston Bay oyster samples analyzed over the first 9 yr have concentrations high enough for potential biological effects to be observed in oysters. The percentages in other agents were chlordanes (22%), butyltins (22%), dieldrin (5%), and PAHs (4%). National Academy of Science-proposed regulatory limits for oysters were exceeded in only 2% of Galveston Bay samples for DDTs and 1% for PCBs. All other contaminants were below proposed NAS limits.

The value of imposex in the dogwhelk Nucella lapillus and the common whelk Buccinum undatum as indicators of TBT contamination

Summary Measures of imposex in the Dogwhelk N. lapillus and the Common Whelk B. undatum were used, together with analyses of butyltins in tissue and sediment samples, to assess current levels of TBT contamination in four sealochs, which are subject to different kinds and intensities of boat use and fish farming. Imposex in N. lapillus is a specific response to TBT and some related organotins and, as would be expected therefore, indices of imposex correlated with concentrations of butyltins in tissues. Data from this species, and sediments, indicate that TBT contamination in three of the sealochs (Loch Sween, Loch Crinan and Killary Harbour) is now low. It has decreased significantly in Loch Sween and Loch Crinan during the past decade. There were higher levels of pollution in Sullom Voe, where oil tankers are a source of TBT. This was reflected in measures of imposex and concentrations of butyltins in tissue samples but not of those in sediments, which were surprisingly low. Imposex was recorded in most samples of B. undatum examined in this study but it is not a useful indicator of butyltin contamination. The condition was severe in some places where pollution was low and, conversely, absent or poorly developed in others, where it was high. There was no correlation between the severity of imposex and tissue concentrations of butyltins in this species.