Imposex reduction and residual butyltin contamination in southern Brazilian harbors

Imposex incidence in gastropod species from the Colombian Caribbean Coast reveals continued and widespread tributyltin contamination after its global ban

Organotin compounds (OTCs), such as tributyltin (TBT) and triphenyltin (TPhT), are released in aquatic environments from antifouling coatings and can cause imposex, an abnormal condition where female snails develop male sexual characteristics. This study investigates temporal variations in imposex incidence along the Colombian Caribbean coast following the 2008 global ban on TBT-based antifouling paints. Over a 12-year period, we assessed imposex in 1,384 adults snails from six species (58% female and 42% male) during 2012, 2016, and 2023. In 2012, just four years after the ban, imposex incidence in some sites reached 100% in the neogastropods Purpura patula, Stramonita haemastoma, Stramonita rustica, and Thais deltoideia. In 2016, imposex in some sites reached 81% for the mesogastropod Strombus pugilis and 39% for the neogastropod Melongena melongena. By 2023, imposex decreased for the first four neogastropods, persisted for S. pugilis, and increased for M. melongena only in Cartagena Bay and the Tolú marina. These findings indicate a general decline in imposex over time, aligning with the ban, but also suggest potential new sources of contamination as imposex rates increased in some previously unaffected areas.

Effects of tributyltin (TBT) on the intermediate metabolism of the crab Callinectes sapidus

This study investigated if the exposure to tributyltin (TBT), a chemical used worldwide in boat antifouling paints, could result in metabolic disturbances in the blue crab Callinectes sapidus. After the exposure to TBT 100 or 1000 ng.L^-1 for 48 and 96 h, hemolymph and tissues were collected to determine the concentration of metabolites and lipid peroxidation. The levels of glucose, lactate, cholesterol, and triglycerides in the hemolymph were not affected by TBT exposure. Hemolymph protein and heart glycogen increased in the crabs exposed to TBT 1000 for 96 h. Anterior gills protein and lipoperoxidation decreased after 96 h in all groups. These results suggest that C. sapidus can maintain energy homeostasis when challenged by the TBT exposure for 48 h and that metabolic alterations initiate after 96 h.

Subacute and low-dose tributyltin exposure disturbs the mammalian hypothalamus-pituitary-thyroid axis in a sex-dependent manner

Tributyltin (TBT) is an endocrine disruptor chemical (EDC) capable of altering the proper function of the hypothalamus-pituitary thyroid (HPT) axis. This study aimed to evaluate the subacute effects of TBT on the HPT axis of male and female rats. A dose of 100 ng/kg/day TBT was used in both sexes over a 15-day period, and the morphophysiology and gene expression of the HPT axis were assessed. TBT exposure increased the body weight in both sexes, while food efficiency increased - only in male rats. It was also possible to note alterations in the thyroid, with the presence of a stratified epithelium, cystic degeneration, and increased interstitial collagen deposition. A reduction in T3 and T4 levels was only observed in TBT male rats. A reduction in TSH levels was observed in TBT female rats. Evaluating mRNA expression, we observed a decrease in hepatic D1 and TRH mRNA levels in TBT female rats. An increase in D2 mRNA expression in the hypothalamus was observed in TBT male rats. Additionally, no significant changes in TRH or hepatic D1 mRNA expression in TBT male rats or in hypothalamic D1 and D2 mRNA expression in TBT female rats were observed. Thus, we can conclude that TBT has different toxicological effects on male and female rats by altering thyroid gland morphophysiology, leading to abnormal HPT axis function, and even at subacute and low doses, it may be involved in complex endocrine and metabolic disorders.

How protected are marine protected areas: A case study of tributyltin in Latin America

Protected areas (PAs) are dedicated and managed to achieve long-term conservation of nature with associated ecosystem services and cultural values. However, few studies have assessed contamination/pollution, one of the top five biodiversity threats, within these areas. In fact, more than 100,000 molecules used in consumer goods are potentially affecting over 250,000 protected areas distributed worldwide. As a result, chemical appraisal within PAs require specific approaches to be feasible. Herein, an approach for assessment of contamination in marine protected areas (MPAs) spread over large continental and/or global areas was proposed and tested using, as a case study, the impact of tributyltin (TBT) within Latin America. This approach included area delimitation, bibliographic survey, construction of attribute tables, data insertion in a Geographic Information System, overlapping with worldwide shapefiles of PAs, identification of affected PAs and evaluation of impacts using the outcomes against specific environmental quality guidelines/directives. A total of 259 records of TBT occurrence and/or its biological effect within 53 marine protected areas (including biosphere reserves, Ramsar sites and National parks) were gathered. Among affected species, were recorded 18 gastropods exhibiting imposex. In addition, 6 bivalves, 1 crustacean, and 3 fish species presenting TBT residues in tissues were seen in MPAs from Brazil, Argentina, Ecuador, Peru, Chile and Venezuela. Since levels of TBT recorded in several studied MPAs were enough do induce deleterious biological responses over marine biota, it was clear that conservancy goals of some "protected" areas are under threat. Considering that only TBT exposure was appraised, and these areas are likely to be concomitantly exposed to other classes of contaminants, the actual scenario can be even more frightening. Although initially applied as a TBT case study, the present approach enables an overview for other chemicals within protected areas worldwide.

Are antifouling residues a matter of concern in the largest South American port?

In the present study, levels of booster biocides (diuron, Irgarol, chlorothalonil, dichlofluanid and DCOIT), butyltin compounds (TBT, DBT and MBT) and antifouling paint particles (APPs) were assessed in sediments of areas under the influence of the largest Latin American port, marinas, boat traffic and ship/boat maintenance facilities located within Santos-São Vicente Estuarine System (SSES). Contamination profile was directly related to local maritime activities, where sediments from the main navigation channel (MNC) presented low levels of antifouling residues while adjacent areas (AA), characterized by the presence of boats and boatyards, showed higher contamination considering all analyzed residues. Moreover, areas under the influence of fishing boats/yards presented relevant levels of butyltins (ΣBTs > 300 ng g^-1) and APPs (>100 μg g^-1), while marinas dominated by recreational boats showed higher booster biocides occurrence. Sites located nearby shipyards in the MNC and boatyards in the AA presented expressive amounts of APPs (>200 μg g^-1). These APPs represent an important long-term source of biocides to the SSES. Thus, the profile of maritime activities in association to local oceanographic conditions drive the spatial distribution of antifouling residues within SESS, which in some case presented levels above sediment guidelines for TBT, DCOIT and diuron.

Simultaneous analysis of butyltins and total tin in sediments as a tool for the assessment of tributyltin behaviour, long-term persistence and historical contamination in the coastal environment

This study presents a new approach for the investigation of tributyltin (TBT) behaviour and fate in the marine environment. The approach is based on a simultaneous analysis of butyltins (BuTs) and total Sn in sediments, thus enabling an assessment of long-term persistence and historical input of TBT. The study also presents first evaluation of the extent to which the TBT-antifouling paints contribute to the contamination of coastal environments with inorganic Sn; it was demonstrated that the inorganic Sn in the investigated areas primarily originates from TBT degradation. The study was conducted by analyzing BuTs and total Sn in sediments from 34 locations along the Croatian Adriatic coast. The results revealed that 85% of the locations were contaminated with both BuTs and inorganic Sn. The share of ƩBuTs/total Sn was low (<10%) even in sediments with low TBT degradation efficiency (TBT/ƩBuTs >40%), demonstrating that only small portion of TBT introduced into the water column reached the sediment before being degraded. This means that recent TBT input into the marine environment may be at least 10 times higher than the amount estimated if only BuTs levels in sediments are considered. It was also demonstrated that TBT concentration in sediments with TOC <1% is not a good indicator of the overall pollution level, even if TBT/TOC approach is used in pollution assessment. Finally, in situ investigation showed that resuspension of contaminated sediments leads to significant release of MBT and DBT into the water column, whereas TBT mainly remains in sediment.

Relevant dose of the environmental contaminant, tributyltin, promotes histomorphological changes in the thyroid gland of male rats

Organotin compounds, such as tributyltin (TBT), are common environmental contaminants and suspected endocrine-disrupting chemicals. Tributyltin is found in antifouling paints, widely used in ships and other vessels. The present study evaluated whether a 15-day treatment with TBT at a dose of 100 ng/kg/day could induce histomorphological changes in the thyroid gland of rats. TBT promoted relevant alterations in the thyroid architecture, being the most relevant histological findings the presence of increased number of small-size follicles in the treated group. In qualitative analyses, colloid vacuolization, papillary budging structures, cystic degeneration and chronic thyroiditis, were observed. Moreover, histomorphometric analysis showed statistically significant changes in the follicular architecture of TBT-treated rats, mainly a decrease in the follicle area (colloid) and an increased epithelial height that resulted in an increased epithelial height/colloid ratio. Augmented collagen deposition was also seen in the thyroids of treated groups. In immunohistochemical (IHC) analyses, the localization of NIS protein was described and a significant increased proliferation index (evaluated by Ki67 positive cells) in the treated group was reported. As an indirect measurement of oxidative stress, mitochondrial protein SDHA was also analyzed by IHC analysis. Although the cytoplasmic expression of SDHA was observed in both groups, the staining intensity score was higher in TBT-treated group. Our results suggest that besides causing histomorphological changes, environmental relevant dose of TBT treatment can also induce oxidative alterations.

Tributyltin reduces bone mineral density by reprograming bone marrow mesenchymal stem cells in rat

Tributyltin (TBT), a proven endocrine disrupter, was widely used in industry and agriculture. Previous research showed that TBT could alter the balance between osteogenesis and adipogenesis, which may have significant consequences for bone health. Herein, we exposed male rats to TBT chloride (TBTCl) to evaluate the deleterious effects of TBT on bone. Exposure to 50 μg kg^-1 TBT resulted in a significant decrease in bone mineral density (BMD) at the femur diaphysis region in the rat. A dose-dependent increase in lipid accumulation and adipocyte number was observed in the bone marrow (BM) of the femur. Meanwhile, TBTCl treatment significantly enhanced the expression of PPARγ and attenuated the expression of Runx2 and β-catenin in BM. In addition, serum ALP activity of TBT-exposed rats also showed a dose-dependent decrease. These results suggest that TBT could reduce BMD via inhibition of the Wnt/β-catenin pathway and skew the adipo-osteogenic balance in the BM of rats.

Can shell alterations in limpets be used as alternative biomarkers of coastal contamination?

The present study evaluated the association among traditional biochemical biomarkers with biometric, morphometric, and elemental composition of Lottia subrugosa (patelliform gastropod) shells from three multi-impacted coastal areas in Brazil. The study was carried out in Todos os Santos Bay (TSB), Santos/São Vicente Estuarine System (SESS) and Paranaguá Estuarine Complex (CEP), using three sampling sites to seek contamination gradients in each area. Results showed that all biomarkers evaluated responded to environmental contamination, regardless the presence (SESS and CEP) or absence (TSB) of a gradient of contamination. The responses found using biometric and morphometric parameters were consistent with the traditional biomarkers of exposure and effects (lipid peroxidation and DNA damage). Indeed, changes in elemental composition of L. subrugosa shells suggest that exposure to contaminated environments is probably responsible for the alterations detected. Despite the simplicity and lower cost of biometric and morphometric analyzes, these parameters are influenced by natural environmental conditions from which biases may arise. Therefore, these tools should be evaluated through experimental studies before it can be used in future assessments. However, the findings from the present study were observed in three aquatic systems distributed over a wide range of latitudes, which indicates that gastropod shells reflect effects resulting from environmental contamination.

Size, season and origin of gastropods matter in imposex assessments

Through controlled exposure to tributyltin (TBT), the effects of season, size, and population origin were evaluated on imposex incidence in Stramonita brasiliensis. Four experiments were carried out with organisms collected from three different sites on the Brazilian coast (Torres - Rio Grande do Sul, Farol de Santa Marta - Santa Catarina, and Aracruz - Espírito Santo). S. brasiliensis were anesthetized, sexed, measured, classified by size in small (< 30 mm), medium (≥ 30 to ≤ 40 mm), or big (> 40 mm) and injected in the foot muscle with 0.5 μg g^-1 of TBT. Organisms were maintained during one month in aquariums with clear marine water under controlled laboratory conditions. One month after injection, the imposex assessments showed that the population from the southeast (tropical) region was more sensitive to TBT than the population from the south of Brazil (the temperate region). A greater sensitivity in the small and medium categories was observed. Females were also more susceptible to TBT when exposed during their reproductive period. Thus, the present study highlighted the need to ensure that intrinsic biological factors related to organisms are considered in such biomonitoring studies to avoid misinterpretation of results.

TBT is still a matter of concern in Peru

Tributyltin (TBT) environmental concentrations as well as imposex levels have been declining in several coastal areas worldwide. However, recent studies have shown that TBT contamination is still an important issue along some Latin American coastal areas. Thus, the incidence of imposex and butyltin compounds (BTs) in sediments and gastropod tissues was spatially and temporally (2009 and 2012) appraised in Lima (Peru) along potential TBT sources (harbors and marinas). Despite the general pattern of reduction close to Callao harbor, a clear increment in the levels of imposex (RPLI = 0.0 to 8.4 and 0.0 to 28.4/VDSI = 0.0 to 3.3 and 0.0 to 3.5) and TBT in tissues (25 to 112 and 62 to 146 ng Sn g^-1) of Thaisella chocolata were seen from 2009 to 2012 in two sampling sites, respectively, located nearby a newly established marina. Thus, despite the international restrictions on the use of TBT-based antifouling paints are apparently reducing the inputs at international harbors, the present study clearly shows that marinas are still acting as important sources of TBT to the study area due possibly to the lack of legal restrictions on production, trading and/or use of TBT. The present findings reinforce what has been seen along many other Latin American coastal areas.

Assessment of organotins and imposex in two estuaries of the northeastern Brazilian coast

Butyltin compounds (BTs) were used worldwide, especially because of their properties as biocides. Due to its high toxicity, the use of tributyltin (TBT) in antifouling paints has been prohibited in most countries. The occurrence and impact of BTs were assessed in surface sediments and in Stramonita rustica populations of two tropical estuaries that host major ports in northeastern Brazil. ΣBT concentrations ranged from <LOQ to 542ngSng^-1 dry weight in sediments while imposex was not observed in S. rustica. This is in contrast to previous studies that reported high incidence of imposex at the same sites. Butyltin degradation index indicates recent input of TBT at levels that might trigger imposex in gastropod species more sensitive than S. rustica. These results emphasize the need of more rigorous controls by local authorities since Brazil has restricted the use of TBT-based antifouling paints.

Butyltin contamination in Northern Chilean coast: Is there a potential risk for consumers?

Imposex is the superimposition of non-functional male sex organs in gastropod females. This syndrome is a hormonal imbalance induced by tributyltin (TBT) which have been used in antifouling paints formulation. The present study aimed to perform an integrated environmental assessment of imposex and butyltin (BT) contamination using surface sediments and tissues of Thaisella chocolata (an edible gastropod) from northern Chile. The results showed imposex incidence in 11 out of 12 sites. In the most contaminated sites, which are areas under the influence of maritime activities, and also used for fishing and aquaculture, RPLI were over 60 and VDSI over 4 (high incidence of sterile females). Exceptionally high contamination levels and evidences of fresh inputs of tributyltin (TBT) were detected along the studied area. TBT levels above 300 and 90ngSng^-1, respectively, were recorded in sediments and edible gastropod tissues of 6 sites. Thus, a daily ingestion of 90 to 173g of T. chocolata foot (4 to 8 organisms) from the most contaminated sites will certainly lead to the consumption of BT exceeding the tolerable daily intake recommended by European Food Safety Authority. It is reasonable to consider that human risk is even higher if daily consumption of additional seafood is considered. Moreover, some contaminated sites were located within the marine reserve "Isla Grande Atacama", indicating that even marine protected areas are under the influence of TBT contamination. These findings suggest that current levels of TBT in the studied area are sufficient to induce harmful effects on the environment and constitutes a potential threat to seafood consumers. Thus, national regulatory actions toward environmental protection and food safety of local populations are still mandatory, even after 8years of the TBT global ban by IMO.

Spatiotemporal appraisal of TBT contamination and imposex along a tropical bay (Todos os Santos Bay, Brazil)

A spatiotemporal evaluation of butyltin contamination was performed between 2010 and 2012 along Todos os Santos Bay (Northeast Brazil) using surface sediments, bivalve tissues (Anomalocardia brasiliana and Mytella guyanensis), and imposex occurrence (Stramonita rustica). The spatial study detected high tributyltin (TBT) levels (maximum values of 262 ng Sn g (-1) - 21,833 ng Sn g(-1) of total organic carbon - for surface sediments and 421 ng Sn g(-1) for bivalve tissues) in the innermost part of the bay. The TBT levels detected in M. guyanensis tissues might cause human health risk since local population consumes these organisms. These high concentrations observed in the bivalves might result in ingestions higher than the safe limits established by European Food Safety Authority (250 ng TBT kg(-1) day(-1)). Considering the temporal evaluation, no difference (p > 0.05) was observed between TBT concentrations in sediments obtained during the two sampling campaigns (2010/2011 and 2012). However, the increasing predominance of TBT metabolites (butyltin degradation index (BDI) >1) in more recent sediments indicates further degradation of old TBT inputs. In spite of that, recent inputs are still evident at this region. Nevertheless, a reduction of imposex parameters in S. rustica over the last decade suggests an overall decline in the TBT contamination, at least in the outermost and possible less impacted region of the bay. The TBT contamination is probably reducing due to the national and international legislative restrictions on the use of TBT as antifouling biocide. The contamination levels, however, are still relevant especially in the inner part of Todos os Santos Bay since they are above those that are likely to cause toxicity to the biota.

Sex steroid imbalances in the muricid Stramonita haemastoma from TBT contaminated sites

Imposex incidence, organotin tissue levels, and sex steroid (free and esterified testosterone and estradiol) levels were assessed in Stramonita haemastoma from Babitonga Bay (Santa Catarina State, Southern Brazil). The imposex levels showed a reduction when compared to a previous evaluation performed in the same area. In spite of that, the detected imposex incidence indicated the occurrence of tributyltin (TBT) inputs that were still able to produce endocrine disruption in local gastropods. In addition, a high level of organotins was observed in tissues of imposexed females. These females also showed a hormonal imbalance, especially in the total testosterone/total estradiol ratio. These findings obtained under realistic field conditions suggest that the steroid pathway could be responsible by the imposex induction after exposure to TBT. In this case, measurements of sex steroid levels can be an additional evidence for monitoring sites and impose affected gastropod populations.

Butyltin and PAH Contamination of Mar del Plata Port (Argentina) Sediments and Their Influence on Adjacent Coastal Regions

The distribution of butyltins (BTs) and polycyclic aromatic hydrocarbons (PAHs) were studied in surface sediments to assess how relevant is Mar del Plata port (Argentina) as a source of contamination to the surrounding environments. Within the port, TBT concentrations ranged from 24.2 to 150 ng Sn g(-1) and PAHs (Σ16) from 180 to 17,094 ng g(-1). At the surrounding beaches, PAHs were detected at low concentrations and TBT concentrations reached 10.9 ng Sn g(-1). Although those low levels indicate that the Port might not be an important source of contamination to the surrounding beaches, the very low TOC content and the coarse grain size of the beaches sediments could explain the sedimentary levels. The results show a reduction in TBT levels in Mar del Plata port after national and international use restrictions of TBT-based antifouling paints.

Evaluation of the use of Olivella minuta (Gastropoda, Olividae) and Hastula cinerea (Gastropoda, Terebridae) as TBT sentinels for sandy coastal habitats

Tributyltin (TBT) contamination is still recorded in the environment even after its ban in antifouling paints. Since most biomonitors of TBT contamination, through imposex evaluation, are hard-bottom gastropods, the identification of soft-bottom sentinels has become useful for regions where rocky shores and coral reefs are absent. Thus, an evaluation of Olivella minuta and Hastula cinerea as monitors of TBT contamination was performed in two sandy beaches located under influence area of São Sebastião harbor (São Paulo state, Brazil), where previous and simultaneous studies have reported environmental contamination by TBT. In addition, the imposex occurrence in H. cinerea was assessed in an area with low marine traffic (Una beach), also located in São Paulo State. A moderate imposex incidence in O. minuta was detected in Pernambuco (% I = 9.36, RPLI = 4.49 and RPLIstand = 4.27) and Barequeçaba (% I = 2.42, RPLI = 0.36 and RPLIstand = 0.81) beaches, indicating TBT contamination. In contrast, more severe levels of imposex were recorded for H. cinerea in Una beach (% I = 12.45) and mainly in Barequeçaba beach (% I = 98.92, RPLI = 26.65). Our results suggest that O. minuta and H. cinerea have good potential as biomonitors for TBT based on their wide geographical distribution, common occurrence in different coastal sediment habitats, easy collection, and association with TBT-contaminated sediments.

Venezuelan Caribbean Sea under the threat of TBT

Although environmental tributyltin (TBT) contamination is considered a solved problem, imposex occurrence in Plicopurpura patula as well as butyltins (BTs) contamination in sediments and tissues were detected along 700 km of the Caribbean coastal shore. Areas under the influence of five main ports of Venezuela were covered, as well as large marinas and sites located away from expected sources. Marinas were the most contaminated areas, whilst imposex incidence and TBT levels were relatively low in areas nearby commercial harbors. Thus, it is evident that marinas have become the main source of fresh TBT to the region. This might explain why imposex incidence seems to be widely distributed along the Venezuelan coast, since leisure boats are circulating along the whole coastal region. In fact, this could be the pattern for other areas of the Caribbean Sea.

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.

Study of photocatalytic degradation of tributyltin, dibutylin and monobutyltin in water and marine sediments

This study reports on the first assessment of the treatment of sediments contaminated by organotin compounds using heterogeneous photocatalysis. Photocatalysis of organotins in water was carried out under realistic concentration conditions (μgL(-1)). Degradation compounds were analyzed by GC-ICP-MS; a quasi-complete degradation of tributyltin (TBT) in water (99.8%) was achieved after 30min of photocatalytic treatment. The degradation by photolysis was about (10%) in the same conditions. For the first time decontamination of highly polluted marine sediments (certified reference material and harbor sediments) by photocatalysis proves that the use of UV and the production of hydroxyl radicals are an efficient way to treat organotins adsorbed onto marine sediment despite the complexity of the matrix. In sediment, TBT degradation yield ranged from 32% to 37% after only 2h of irradiation (TiO2-UV) and the by-products: dibutyltin (DBT) and monobutyltin (MBT) were degraded very rapidly in comparison with TBT. It was shown that during photocatalysis of organotins in sediments, the hydroxyl radical attack and photolysis are the two ways for the degradation of adsorbed TBT.

Bioaccumulation of butyltins and liver damage in the demersal fish Cathorops spixii (Siluriformes, Ariidae)

The toxicity of butyltin compounds (BTs), mainly tributyltin (TBT), has been reported in different organisms. However, such an analysis in fish after field exposure with reference to the related biomarkers has not been commonly observed in the literature. This study presents the uptake of BTs in the liver of a neotropical marine catfish Cathorops spixii in Paranagua Bay, an important estuarine system located in southern Brazil. Two different areas, close to and distant from the harbor, were used for chemical analysis evaluation of hepatotoxicity through genetic, enzymatic, and histopathological biomarkers. The presence of polycyclic aromatic hydrocarbons in bile was also considered as a biomarker. The results showed a significant relationship between TBT levels and the inhibition of biotransformation enzymes and high occurrence of melanomacrophages in fish collected close to the harbor site. These effects were linked to the absence of TBT metabolites in the liver. In the second site, the presence of DBT was associated with an increase in EROD and GST activity. The larger amount of DNA damage as well as the highest oxidative stress was noted in fish from the less TBT-polluted area, where DBT and bile PAHs occurred. These findings showed different impact levels due to or increased by the chronic exposure of biota to BTs.

Bioluminescent yeast assay for detection of organotin compounds

Organotin compounds are toxic and endocrine disrupting compounds, which have been intensively used as antifouling paints for ship hulls and thus are widely spread in the environment. They are suspected to cause imposex, the formation of male characteristics in female gastropods, because of the activation of retinoid X receptor (RXR) at very low environmental concentrations. Here we report the development and optimization of a bioluminescent yeast assay for the detection of organotin compounds based on the interaction with a hybrid RXR and subsequent expression of a reporter luciferase gene. This assay is highly specific toward organotin compounds and natural ligands of the RXR. It detects tributyltin and triphenyltin in nanomolar concentrations (detection limits were found to be 30 nM and 110 nM, respectively) and allows small-scale high-throughput analyses. Furthermore it was possible to measure tributyltin directly in untreated spiked sediments. Thus, the results provided within one working day can be used for the assessment of bioavailability and mixture effect of organotin compounds in environmental samples.

Is aphallic vas deferens development in females related to the distance from organotin sources? A study with Stramonita haemastoma

Imposex, a syndrome characterized by the appearance of a penis and/or vas deferens in female gastropods due the presence of organotins in environment, is still observed in Brazilian gastropod populations, as in other countries, even after the tributyltin (TBT) ban. Nevertheless, the progressive controls on the use of organotins in antifouling systems at national and international levels and the consequent reduction of their environmental concentrations have led to changes in the characteristics of imposex development observed in Stramonita haemastoma. Populations of this species were analyzed on the coast of Rio de Janeiro (Brazil) between 2007 and 2008, and the developmental pathways associated with the syndrome were identified. Compared with previous works, it was noted that imposex expression was reduced in most of Guanabara Bay. Aphallic imposex development, on the other hand, showed a marked increase. The pathways of imposex development were also evaluated in a temporal data series from a fixed sampling station at Vermelha beach, and the incidence of aphallic imposex development was found to show a marked increase from 1998 onward. Furthermore, the observation of either the presence or absence of a penis in imposex-affected females may indicate that penis development is related to the contaminant exposure level and that the decreasing TBT concentrations in the local environment result in the predominance of an aphallic route of imposex development. These findings support the idea that imposex female aphally in this species could be a dose-dependent response, rather than a genetic anomaly.

Species-specific differences in the inhibition of human and zebrafish 11β-hydroxysteroid dehydrogenase 2 by thiram and organotins

Dithiocarbamates and organotins can inhibit enzymes by interacting with functionally essential sulfhydryl groups. Both classes of chemicals were shown to inhibit human 11β-hydroxysteroid dehydrogenase 2 (11β-HSD2), which converts active cortisol into inactive cortisone and has a role in renal and intestinal electrolyte regulation and in the feto-placental barrier to maternal glucocorticoids. In fish, 11β-HSD2 has a dual role by inactivating glucocorticoids and generating the major androgen 11-ketotestosterone. Inhibition of this enzyme may enhance glucocorticoid and diminish androgen effects in fish. Here, we characterized 11β-HSD2 activity of the model species zebrafish. A comparison with human and mouse 11β-HSD2 revealed species-specific substrate preference. Unexpectedly, assessment of the effects of thiram and several organotins on the activity of zebrafish 11β-HSD2 showed weak inhibition by thiram and no inhibition by any of the organotins tested. Sequence comparison revealed the presence of an alanine at position 253 on zebrafish 11β-HSD2, corresponding to cysteine-264 in the substrate-binding pocket of the human enzyme. Substitution of alanine-253 by cysteine resulted in a more than 10-fold increased sensitivity of zebrafish 11β-HSD2 to thiram. Mutating cysteine-264 on human 11β-HSD2 to serine resulted in 100-fold lower inhibitory activity. Our results demonstrate significant species differences in the sensitivity of human and zebrafish 11β-HSD2 to inhibition by thiram and organotins. Site-directed mutagenesis revealed a key role of cysteine-264 in the substrate-binding pocket of human 11β-HSD2 for sensitivity to sulfhydryl modifying agents.

High tributyltin and imposex levels in the commercial muricid Thais chocolata from two Peruvian harbor areas

The first appraisal of butyltin (BT) contamination linked with imposex incidence in Peruvian coastal areas was performed in the present study. Imposex occurrence and BT levels in female bodies were analyzed in the rock snail Thais chocolata distributed along 10 sites in areas under the influence of Callao and Chimbote Harbors. Imposex levels associated to high tributyltin (TBT) concentrations were observed in six of 10 studied sites, and the highest imposex levels were seen in gastropods collected near the harbor terminals. Tributyltin concentrations were the highest reported for gastropod mollusks (up to 662 ng Sn g(-1)) in recent studies. Although TBT-based antifouling paints have been banned globally (International Maritime Organization, 2008), the combination of high imposex and TBTs level with butyltin degradation index values indicated fresh TBT inputs in these Peruvian coastal areas. Thus, the need to implement local regulatory strategies related to the use of TBT-free antifouling paints is urgent, as is a thorough assessment of the effectiveness of the TBT global ban. Moreover, the wide distribution of T. chocolata combined with its capability to elicit imposex and bioaccumulate BTs renders this a good sentinel species for TBT contamination along the western South American coast.