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

Update on the status of the contamination by organotin compounds in sediment of Nuevo Gulf, Argentina. Insights from field and experimental studies

Organotin compounds are persistent pollutants and are considered chemicals of high environmental concern. In the present study, the distribution and degradation of tributyltin were evaluated in field sediments and through an ex situ experiment. For this, sediment samples from two locations were analysed: Luis Piedrabuena Harbour, with higher maritime traffic, and Cerro Avanzado, which receives less impact from anthropogenic activities. The results indicated that pollution levels at Luis Piedrabuena Harbour have decreased compared with studies performed 9 years ago for the same area. On the contrary, traces of organotin compounds have been found for the first time at Cerro Avanzado. Moreover, the butyltin degradation index indicated that organotin compounds undergo an advanced degradation process in the collected samples at both sites. Ex situ experiments revealed a limited capacity of sediments to retain tributyltin, and suggested an active role of bioturbation activity in the degradation of these compounds. In addition, visualisation using chemometric techniques (principal components analysis) allowed a simpler analysis of two sediment characteristics: the degree of contamination and the degradation levels of organotin compounds.

Transcriptomics-based analysis reveals the nephrotoxic effects of triphenyltin (TPT) on SD rats by affecting RAS, AQPs and lipid metabolism

Triphenyltin (TPT) is a class of organotin compounds that are extensively used in industry and agriculture. They have endocrine-disrupting effects and cause severe environmental contamination. Pollutants may accumulate in the kidneys and cause pathological complications. However, the mechanism of TPT's toxicological effects on the kidney remains unclear. This study aimed to investigate the toxic effects and mechanism of action of TPT exposure on renal impairment in rats. Male SD rats were divided into four groups: the Ctrl group (control group), TPT-L group (0.5 mg/kg/d), TPT-M group (1 mg/kg/d), and TPT-H group (2 mg/kg/d). After 28 days of exposure to TPT, we observed the morphology and structure of kidney tissue using HE, PASM, and Masson staining. We also detected serum biochemical indexes, performed transcriptome sequencing of rat kidney tissue using RNA-seq. Furthermore, protein expression levels were measured through immunohistochemistry and gene expression levels were determined using RT-qPCR. The study results indicated a decrease in kidney weight and relative kidney weight after 28 days of exposure to TPT. Additionally, TPT caused damage to kidney structure and function, as evidenced by HE staining, PASM staining, and serum biochemical tests. Transcriptomics identified 352 DEGs, and enrichment analyses revealed that TPT exposure primarily impacted the renin-angiotensin system (RAS). The expression levels of water channel proteins were reduced, and the expression levels of RAS and lipid metabolism-related genes (Mme, Ace, Fasn, Cyp4a8, Cpt1b and Ppard) were significantly decreased in the TPT-treated group. In summary, exposure to TPT may impair renal structure and function in rats by affecting RAS, AQPs, and lipid metabolism.

Determination of organotin compounds in marine sediments from Arctic Svalbard and West Antarctic Fildes Peninsula

This study investigated the contamination levels of five typical organotin compounds in Arctic and Antarctic marine sediments. Organotin total concentrations ranged from not detected (ND) to 37.9 ng Sn/g dw and from ND to 34.0 ng Sn/g dw in surface sediments of Svalbard and Fildes Peninsula, respectively. Dibutyltin accounted for 11.3 %-100 % of butyltins in Arctic sediments, whilst diphenyltin was the predominant phenyltin species in both Arctic and Antarctic. However, the concentrations of tributyltin and triphenyltin were lower than low-substituted organotins in the study areas, indicating the effectiveness of international ban on the use of triorganotin-based antifouling paints. No significant difference in organotin contamination was found between Arctic and Antarctic, although the time suffered from human interference was shorter in the Antarctic. Overall, these data can provide a diagnosis of recent organotin inputs in polar regions and serve as a baseline for future study assessing their local applications.

Low-dose tributyltin triggers human chondrocyte senescence and mouse articular cartilage aging

Tributyltin (TBT) is known as an endocrine-disrupting chemical. This study investigated the effects and possible mechanisms of TBT exposure on inducing human articular chondrocyte senescence in vitro at the human-relevant concentrations of 0.01-0.5 μM and mouse articular cartilage aging in vivo at the doses of 5 and 25 μg/kg/day, which were 5 times lower than the established no observed adverse effect level (NOAEL) and equal to NOAEL, respectively. TBT significantly increased the senescence-associated β-galactosidase activity and the protein expression levels of senescence markers p16, p53, and p21 in chondrocytes. TBT induced the protein phosphorylation of both p38 and JNK mitogen-activated protein kinases in which the JNK signaling was a main pathway to be involved in TBT-induced chondrocyte senescence. The phosphorylation of both ataxia-telangiectasia mutated (ATM) and histone protein H2AX (termed γH2AX) was also significantly increased in TBT-treated chondrocytes. ATM inhibitor significantly inhibited the protein expression levels of γH2AX, phosphorylated p38, phosphorylated JNK, p16, p53, and p21. TBT significantly stimulated the mRNA expression of senescence-associated secretory phenotype (SASP)-related factors, including IL-1β, TGF-β, TNF-α, ICAM-1, CCL2, and MMP13, and the protein expression of GATA4 and phosphorylated NF-κB-p65 in chondrocytes. Furthermore, TBT by oral gavage for 4 weeks in mice significantly enhanced the articular cartilage aging and abrasion. The protein expression of phosphorylated p38, phosphorylated JNK, GATA4, and phosphorylated NF-κB-p65, and the mRNA expression of SASP-related factors were enhanced in the mouse cartilages. These results suggest that TBT exposure can trigger human chondrocyte senescence in vitro and accelerating mouse articular cartilage aging in vivo.

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

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

The ecotoxicology of marine tributyltin (TBT) hotspots: A review

Tributyltin (TBT) was widely used as a highly efficient biocide in antifouling paints for ship and boat hulls. Eventually, TBT containing paints became globally banned when TBT was found to cause widespread contamination and non-target adverse effects in sensitive species, with induced pseudohermaphroditism in female neogastropods (imposex) being the best-known example. In this review, we address the history and the status of knowledge regarding TBT pollution and marine TBT hotspots, with a special emphasis on the Norwegian coastline. The review also presents a brief update on knowledge of TBT toxicity in various marine species and humans, highlighting the current understanding of toxicity mechanisms relevant for causing endocrine disruption in marine species. Despite observations of reduced TBT sediment concentrations in many marine sediments over the recent decades, contaminant hotspots are still prevalent worldwide. Consequently, efforts to monitor TBT levels and assessment of potential effects in sentinel species being potentially susceptible to TBT in these locations are still highly warranted.

A reassessment of TBT action levels for determining the fate of dredged sediments in the United Kingdom

As part of reviewing the United Kingdom (UK) action levels (ALs) of contaminants for managing the disposal of dredged marine sediment material, tributyl tin (TBT) has been reassessed. TBT is a banned biocide capable of causing severe harm to the marine environment. Its presence is routinely screened for prior to marine disposal of dredged sediment material. Dredged sediment TBT concentrations have been studied using UK monitoring data obtained between 2000 and 2018. The changes in these TBT concentrations have guided the reassessment of ALs. Recent toxicity studies have also guided the reassessment of TBT ALs. This study, which itself forms part of a larger review by the Department for Environment, Food and Rural Affairs, has concluded that current UK TBT ALs may no longer be fit for purpose. A more environmentally protective approach for controlling release of TBT into the marine environment is recommended.

An absurd scenario in 2021: Banned TBT-based antifouling products still available on the market

Despite the efforts of the International Marine Organization (IMO), through the International Convention on the Control of Harmful Antifouling Systems on Ships to ban the use of TBT-based antifouling paints (September 2008), and the Rotterdam Convention (RC) to forbid the trade of tributyltin (TBT), the situation does not seem to have significantly changed since 2014 when TBT-based paints were shown to be still being manufactured in the United States and offered for sale in stores throughout the Caribbean and Central America. In fact, this study shows that seven years later the same situation not only persists, but may have an even more global distribution than previously thought.

Evaluation of the effects produced by subacute tributyltin administration on vascular reactivity of male wistar rats

Tributyltin chloride (TBT) is an organotin compound widely used in several high biocides for agroindustrial applications, such as fungicides, and marine antifouling paints leading to endocrine disrupting actions, such as imposex development in mollusks. In female rats, TBT has been shown to promote ovarian dysfunction, reduction of estrogen protective effect in the vascular morphophysiology, at least in part by oxidative stress consequences. Estrogen causes coronary endothelium-dependent and independent vasodilation. However, the TBT effects on cardiovascular system of male rats are not fully understood. The aim of this study was to evaluate the effects of subacute TBT exposure in aorta vascular reactivity from male wistar rats. Rats were randomly divided into three groups: control (C), TBT 500 ng/kg/day and TBT 1000 ng/kg/day. TBT was administered daily for 30 days by oral gavage. We found that TBT exposure enhanced testosterone serum levels and it was also observed obesogenic properties. TBT exposure evoked an increase in endothelium-dependent and independent phenylephrine-induced contraction, associated to an inhibition in eNOS activity. On the other hand, it was observed an enhancement of iNOS and NF-kB protein expression. We also observed an increase in oxidative stress parameters, such as superoxide dismutase (SOD) and catalase expression, and also an increase in malondialdehyde production. Finally, TBT exposure produced aortic intima-media thickness. Taken together, these data suggest a potential cardiovascular toxicological effect after subacute TBT exposure in male rats.

Resveratrol ameliorates polycystic ovary syndrome via transzonal projections within oocyte-granulosa cell communication

Rationale: Polycystic ovary syndrome (PCOS) is closely linked to follicular dysplasia and impaired bidirectional oocyte-granulosa cell (GC) communication. Given that PCOS is a heterogeneous, multifactorial endocrine disorder, it is important to clarify the pathophysiology of this ovarian disease and identify a specific treatment.

Methods: We generated PCOS rat models based on neonatal tributyltin (TBT) exposure and studied the therapeutic effect and mechanism of resveratrol (RSV), a natural plant polyphenol. Transcriptome analysis was conducted to screen the significantly changed pathways, and a series of experiments, such as quantitative real-time polymerase chain reaction (PCR), Western blot and phalloidin staining, were performed in rat ovaries. We also observed similar changes in human PCOS samples using Gene Expression Omnibus (GEO) database analysis and quantitative real-time PCR.

Results: We first found that injury to transzonal projections (TZPs), which are specialized filopodia that mediate oocyte-GC communication in follicles, may play an important role in the etiology of PCOS. We successfully established PCOS rat models using TBT and found that overexpressed calcium-/calmodulin-dependent protein kinase II beta (CaMKIIβ) inhibited TZP assembly. In addition, TZP disruption and CAMK2B upregulation were also observed in samples from PCOS patients. Moreover, we demonstrated that RSV potently ameliorated ovarian failure and estrus cycle disorder through TZP recovery via increased cytoplasmic calcium levels and excessive phosphorylation of CaMKIIβ.

Conclusions: Our data indicated that upregulation of CaMKIIβ may play a critical role in regulating TZP assembly and may be involved in the pathogenesis of PCOS associated with ovarian dysfunction. Investigation of TZPs and RSV as potent CaMKIIβ activators provides new insight and a therapeutic target for PCOS, which is helpful for improving female reproduction.

Effects of chronic exposure to environmental levels of tributyltin on the lined seahorse (Hippocampus erectus) liver: Analysis of bioaccumulation, antioxidant defense, and immune gene expression

Tributyltin (TBT), an organotin compound frequently detected in the coastal environments, poses a threat to aquatic organisms. The lined seahorse (Hippocampus erectus) is a vulnerable species found in nearshore water habitats. The mechanisms by which this fish responds to TBT exposure are not yet fully understood. Histological, biochemical, and transcriptional analyses were conducted, and the results showed that 60 days of exposure to 50 and 500 ng/L TBT caused significant tin accumulation and liver damage to seahorses. Antioxidant defenses and immune responses to TBT exposure in the livers of seahorses were further investigated. The enzymatic activity of superoxide dismutase and malondialdehyde content increased, while catalase activity decreased. Transcriptomic analysis revealed that a series of genes involved in the antioxidant defense system were highly induced to protect the hepatic cells from oxidative damage. TBT exposure also resulted in the induction of genes associated with immune and inflammatory processes, representing a stress response to combat the adverse environmental conditions in the exposed seahorses. Furthermore, seahorses showed an increased health risk, according to the elevation of the expression of genes with tumor-promoting effects, when exposed to TBT. These findings contribute to our understanding of the adverse effects of TBT exposure on seahorses, and their potential defense mechanisms.

Functional nanomaterials, synergisms, and biomimicry for environmentally benign marine antifouling technology

Marine biofouling remains one of the key challenges for maritime industries, both for seafaring and stationary structures. Currently used biocide-based approaches suffer from significant drawbacks, coming at a significant cost to the environment into which the biocides are released, whereas novel environmentally friendly approaches are often difficult to translate from lab bench to commercial scale. In this article, current biocide-based strategies and their adverse environmental effects are briefly outlined, showing significant gaps that could be addressed through advanced materials engineering. Current research towards the use of natural antifouling products and strategies based on physio-chemical properties is then reviewed, focusing on the recent progress and promising novel developments in the field of environmentally benign marine antifouling technologies based on advanced nanocomposites, synergistic effects and biomimetic approaches are discussed and their benefits and potential drawbacks are compared to existing techniques.

Effects of microplastics (MPs) and tributyltin (TBT) alone and in combination on bile acids and gut microbiota crosstalk in mice

Microplastics (MPs) and tributyltin (TBT) are both potential environmental pollutants that enter organisms through the food chain and affect bodily functions. However, the effects and mechanisms of MPs and TBT exposure (especially the co-exposure of both pollutants) on mammals remain unclear. In this study, Ф5μm MPs (5MP) was administered alone or in combination with TBT to investigate the health risk of oral exposure in mice. All three treatments induced inflammation in the liver, altered gut microbiota composition and disturbed fecal bile acids profiles. In addition to decreasing triglyceride (TG) and increasing aspartate aminotransferase (AST) and macrophage-expressed gene 1 (Mpeg1), 5MP induced hepatic cholestasis by stimulating the expression of the cholesterol hydroxylase enzymes CYP8B1 and CYP27A1, and inhibiting multidrug resistance-associated protein 2 and 3 (MRP2, MRP3), and bile-salt export pump (BSEP) to prevent bile acids for entering the blood and bile. Correspondingly, 5MP treatment decreased 7-ketolithocholic acid (7-ketoLCA) and taurocholic acid (TCA), which were positively correlated with decreased Bacteroides and Marvinbryantia and negatively correlated with increased Bifidobacterium. In addition, TBT increased interferon γ (IFNγ) and Mpeg1 levels to induce inflammation, accompanied by decreased 7-ketoLCA, tauro-alpha-muricholic acid (T-alpha-MCA) and alpha-muricholic acid (alpha-MCA) levels, which were negatively related to Coriobacteriaceae_UCG-002 and Bifidobacterium. Co-exposure to 5MP and TBT also decreased TG and induced bile acids accumulation in the liver due to inhibited BSEP, which might be attributed to the co-regulation of decreased T-alpha-MCA and Harryflintia. In conclusion, the administration of 5MP and TBT alone and in combination could cause gut microbiome dysbiosis and subsequently alter bile acids profiles, while the combined exposure of 5MP and TBT weakened the toxic effects of 5MP and TBT alone.

Temporal evolution of imposex and butyltin contamination in Gemophos viverratus from São Vicente (Cabo Verde) - a countercurrent trend on the world scenario

Organotin (OT) based Antifouling Systems (AFS) were globally banned by the AFS Convention since 2008, but the Republic of Cabo Verde did not ratify this Convention, nor did it develop a national legislation to control OT-AFS. Gemophos viverratus imposex and butyltin tissue contamination were assessed around the São Vicente Island (Cabo Verde) in 2019 and compared with the data available from 2012. The vas deferens sequence index (VDSI), the relative penis length (RPL), the percentage of females with imposex (%I) and the percentage of sterilized females (%S) in 2019 ranged from 0 to 4.0, 0-84.4%, 0-100% and 0-5.1%, respectively, whilst TBT reached maximum values of ≈30 ng TBT-Sn g^-1 dw in the whelk tissues. These values are very similar to those registered in 2012, which indicates that TBT pollution has not decreased over the years, in contrast to the declining trend observed worldwide.

Insights into the Restoration of Tributyltin Contaminated Environments Using Marine Bacteria from Portuguese Fishing Ports

Tributyltin (TBT) is an organotin chemical mainly used as biocide in marine antifouling paints. Despite the restrictions and prohibitions on its use, TBT is still an environmental problem due to its extensive application and subsequent release into the environment, being regarded as one of the most toxic chemicals released into the marine ecosystems. Microorganisms inhabiting impacted sites are crucial for their restoration since they have developed mechanisms to tolerate and break down pollutants. Nonetheless, transformation products resulting from the degradation process may still be toxic or, sometimes, even more toxic than the parent compound. The determination of the parent and degradation products by analytical methods, although necessary, may not be ecologically relevant since no information is provided regarding their ecotoxicity. In this study, marine bacteria collected from seven Portuguese fishing ports were isolated and grown in the presence of TBT. Bacteria that exhibited higher growth were used to bioremediate TBT-contaminated waters. The potential of these bacteria as bioremediation agents was evaluated through ecotoxicological assays using the sea snail Gibbula umbilicalis as model organism. Data suggested that some TBT-tolerant bacteria, such as Pseudomonas putida, can reduce the toxicity of TBT contaminated environments. This work contributes to the knowledge of TBT-degrading bacteria.

Modified, optimized method of determination of Tributyltin (TBT) contamination in coastal water, sediment and biota in Sri Lanka

Tributyltin (TBT) is a toxic organotin compound that belongs to the group of Persistent Organic Pollutants (POPs) and it is documented to cause severe sexual disorders development in aquatic fauna. According to the present study, The TBT concentration in coastal water ranged from 303 ± 7.4 ngL^-1 to 25 ± 4.2 ngL^-1 wherein sediment was from 107 ± 4.1 ngKg^-1 to 17 ± 1.4 ngKg^-1. TBT in Perna viridis was found to range from 4 ± 1.2 ngKg^-1 to 42 ± 2.2 ngKg^-1 wet weight and in ascending order of the body weight. The highest TBT level in water and sediment was found in the Colombo port where the highest level of TBT in P. viridis (42 ± 2.2 ngKg^-1) was recorded from the Dikkowita fishery harbor. A positive correlation between the number of male P. viridis and TBT level (p < 0.05) suggests possible reproductive impairment in aquatic animals exposed continuously to a high concentration of TBT.

Raposo MM. Optical Fiber Sensors for Biocide Monitoring: Examples, Transduction Materials, and Prospects

Antifouling biocides are toxic to the marine environment impacting negatively on the aquatic ecosystems. These biocides, namely, tributyltin (TBT) and Cu(I) compounds, are used to avoid biofouling; however, their toxicity turns TBT and Cu(I) monitoring an important health issue. Current monitoring methods are expensive and time-consuming. This review provides an overview of the actual state of the art of antifouling paints' biocides, including their impact and toxicity, as well as the reported methods for TBT and Cu(I) detection over the past decade. The principles of optical fiber sensors (OFS) applications, with focus on environmental applications, and the use of organic chemosensors in this type of sensors are debated. The multiplexing ability of OFS and their application on aquatic environments are also discussed.

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.

Imposex Incidence in Gastropod Species from Santa Marta Coastal Zone, Colombian Caribbean Sea

Imposex is a phenomenon widely associated with environmental exposure to organotin compounds which were quite common components of antifouling paints applied on boats and ship hulls. Here we study the incidence of imposex in neogastropods and its relation with water quality and maritime traffic in the coastal strip of Santa Marta, Colombia. Imposex was determined via specialized indexes and related to the organisms' size, somatic conditions, variables of water quality and maritime traffic, in a space-time assessment. There was evidence of imposex in five species Plicopurpura patula, Vasula deltoidea, Stramonita haemastoma, S. floridana, and Gemophos auritulus. Purpura patula and Vasula deltoidea species were found in all sampling sites. The results have proved that imposex is highly influenced by the maritime traffic variable, with greater prevalence during the dry season, and with P. patula being more sensitive than V. deltoidea.

Tributyltin enhanced anxiety of adult male zebrafish through elevating cortisol level and disruption in serotonin, dopamine and gamma-aminobutyric acid neurotransmitter pathways

Tributyltin (TBT), a widely and persistently distributed organontin, has been well documented to disrupt reproduction and behaviors in animals due to its anti-aromatase activity. TBT has been also reported to enhance anxiety in several fish species, whereas the mechanism underlying remains largely unknown. To investigate the disruption of TBT on fish anxiety and the mechanisms possibly involved, adult male zebrafish (Danio rerio) were treated with TBT (100 and 500 ng/L) for 28 days and anxiety behavior was further investigated using a novel tank dive test. Result showed that TBT treatment significantly enhanced the total time of the fish spent in the lower half, delayed the onset time to the higher half of the tank and increased the total duration of freezing of the fish, indicating an enhanced anxiety in TBT-treated fish. Accordingly, TBT sharply elevated the cortisol levels in plasma in a concentration-dependent manner, suggesting that the elevated cortisol level might be involved in the enhanced anxiety. Although the expression of crha was significantly increased and crhbp was significantly decreased in the brain of TBT-treated fish which is consistent to the elevated cortisol level, the expressions of actha and acthb were sharply down-regulated. In contrast, the expressions of genes responsible for the synthesis and action of serotonin (5-HT) (pet1, thp2 and htr1aa), dopamine (DA) (th1, slc6a3, drd2a and drd2b) and gamma-aminobutyric acid (GABA) (gad2 and gabrg2) were all significantly inhibited. The down-regulation of these pivotal genes acting in 5-HT, DA and GABA neurotransmitter systems in response to TBT corresponded well with the TBT-enhanced anxiety in fish. It was thus strongly suggested that these neurotransmitters might be also involved in TBT-enhanced anxiety in adult male zebrafish. The present study extended our understanding of the neurotoxicity of TBT on the anxiety control and behavioral modulation in fish.

Survey of imposex in Nucella lapillus as an indicator of tributyltin pollution in Northern Irish coastal waters, 2004 to 2017

Tributyltin (TBT) was a commonly used biocide in anti-fouling paints for marine vessels, however, it had negative impacts on non-target species, including causing imposex in dogwhelks (Nucella lapillus). Since the 1980s, legislation has been introduced to curtail its usage, culminating in a ban by the International Maritime Organisation (IMO) in 2008. In 2004 a national imposex monitoring network was established in Northern Ireland to determine the level and extent of TBT pollution. The level of imposex in N. lapillus was assessed according to the degree of male sexual development in the female using three measures: percentage of imposex-affected females (%I), the relative penis size index (RPSI), and the vas deferens sequence index (VDSI). All sites showed improvement since the initial survey with a reduction in imposex and an improvement in ecological quality under the classification of the Convention for the Protection of the Marine Environment of the North-East Atlantic (OSPAR).

Total tin (TSn) biomagnification: Evaluating organotin trophic flow and dispersion using hepatic TSn concentrations and stable isotope (C, N) data of nektonic organisms from Brazil

A previous investigation of our research team has demonstrated the suitability of using hepatic total tin (ΣSn) concentrations for evaluating dolphin exposure to organotins (OTs). The present study develops the previous technique into three different approaches that comprise data: (1) on hepatic ΣSn concentrations of 121 Guiana dolphins (Sotalia guianensis) from five different coastal areas (CAs): (2) on ΣSn, δ¹³C and δ¹⁵N for 40 dolphins from Rio de Janeiro state (RJ), including ten different delphinid species; as well as (3) on hepatic ΣSn concentrations and δ¹⁵N values on 31 individuals from five different fish species from Sepetiba Bay (SB, Rio de Janeiro-RJ, Brazil). Hepatic ΣSn concentrations of Guiana dolphins from Guanabara Bay (GB, RJ) were significantly higher than those found in other four CAs from S and SE Brazilian regions. Significant positive correlations were found between ΣSn concentrations and δ¹³C data in delphinid species, demonstrating a coast-ocean gradient in dolphin exposure to OTs in RJ state. Significant and positive correlations were observed between ΣSn concentrations and both δ¹⁵N and Trophic Position (TP) values of fish, as well as high values were found for Trophic Magnification Factor (TMF = 3.03) and Trophic Magnification Slope (TMS = 0.14), demonstrating OT biomagnification in SB ichthyofauna.

Histological and Behavioral Toxicity of Tributyltin in the Tropical Guppy Poecilia vivipara

The tropical estuarine guppy Poecilia vivipara was used to address fish early life stage toxicity caused by the antifouling contaminant tributyltin. Six-day-old P. vivipara were exposed for 7 d to control water and waterborne tributyltin at 15.8, 83.8, 716, and 818 ng tin (Sn) L^-1 . After exposure, swimming, feeding, growth, and eye histological endpoints were evaluated. Histopathological analysis of the retinal pigment epithelium (RPE) indicated alterations in pigment positioning at all tributyltin concentrations. A dose-dependent increase in photoreceptor layer disorganization and iris melanin hyperpigmentation was verified, and high frequencies of RPE invaginations and iris epithelial cell atrophy were observed even at the lowest exposure concentration of 15.8 ng Sn L^-1 . At the highest exposure level (818 ng Sn L^-1 ) fish also presented reductions in swimming speed, swimming resistance, daily capture of Artemia nauplii, and growth in weight of 85, 60, 33, and 56% relative to controls, respectively. This association between retinal histopathology and reduced swimming and foraging behavior can reduce recruitment to the adult population. Environ Toxicol Chem 2020;39:1953-1963. © 2020 SETAC.

A quarter century of recovery of the whelk Thais orbita from tributyltin pollution off Perth, Western Australia

Imposex is a condition in which females of dioecious marine snails develop rudimentary male characteristics. It is caused by tributyltin (TBT) used as an antifoulant in vessel paints since the late 1960s. Following the 2008 international ban on TBT, a decreasing rate of imposex has been observed worldwide. In Western Australia, imposex surveys of the whelk Thais orbita up to 2011 in the Perth metropolitan area suggested a decreasing trend but a significant recovery has not been confirmed. Collection of T. orbita from 11 sites in 2019 demonstrated a virtually complete recovery from imposex. Although it is generally accepted that male snails are not affected by TBT, the historical data set allowed confirmation that the male penis is of similar size in T. orbita collected at heavily affected sites and at relatively unaffected sites. Similarly, imposexed female snails had similar shell lengths to female snails at non-impacted sites.

RXR Expression in Marine Gastropods with Different Sensitivity to Imposex Development

The superposition of male sexual characteristics in female marine gastropods (imposex) represents one of the clearest ecological examples of organotin-mediated endocrine disruption. Recent evidences suggest that signaling pathways mediated by members of the nuclear receptor superfamily, RXR and PPARγ, are involved in the development of this pseudohermaphroditic condition. Here, we identified significant differences in RXR expression in two caenogastropod species from Nuevo Gulf, Argentina, Buccinanops globulosus and Trophon geversianus, which present clear contrast in imposex incidence. In addition, B. globulosus males from a polluted and an unpolluted area showed differences in RXR expression. Conversely, PPARγ levels were similar between both analyzed species. These findings indicate specie-specific RXR and PPARγ expression, suggesting a major role of RXR in the induction of imposex.

Invertebrates facing environmental contamination by endocrine disruptors: Novel evidences and recent insights

The crisis of biodiversity we currently experience raises the question of the impact of anthropogenic chemicals on wild life health. Endocrine disruptors are notably incriminated because of their possible effects on development and reproduction, including at very low doses. As commonly recorded in the field, the burden they impose on wild species also concerns invertebrates, with possible specificities linked with the specific physiology of these animals. A better understanding of chemically-mediated endocrine disruption in these species has clearly gained from knowledge accumulated on vertebrate models. But the molecular pathways specific to invertebrates also need to be reckoned, which implies dedicated research efforts to decipher their basic functioning in order to be able to assess its possible disruption. The recent rising of omics technologies opens the way to an intensification of these efforts on both aspects, even in species almost uninvestigated so far.

Tributyltin and triphenyltin induce 11β-hydroxysteroid dehydrogenase 2 expression and activity through activation of retinoid X receptor α

Exposure to the environmental pollutants organotins is of toxicological concern for the marine ecosystem and sensitive human populations, including pregnant women and their unborn children. Using a placenta cell model, we investigated whether organotins at nanomolar concentrations affect the expression and activity of 11β-hydroxysteroid dehydrogenase type 2 (11β-HSD2). 11β-HSD2 represents a placental barrier controlling access of maternal glucocorticoids to the fetus. The organotins tributyltin (TBT) and triphenyltin (TPT) induced 11β-HSD2 expression and activity in JEG-3 placenta cells, an effect confirmed at the mRNA level in primary human trophoblast cells. Inhibition/knock-down of retinoid X receptor alpha (RXRα) in JEG-3 cells reduced the effect of organotins on 11β-HSD2 activity, mRNA and protein levels, revealing involvement of RXRα. Experiments using RNA and protein synthesis inhibitors indicated that the effect of organotins on 11β-HSD2 expression was direct and caused by increased transcription. Induction of placental 11β-HSD2 activity by TBT, TPT and other endocrine disrupting chemicals acting as RXRα agonists may affect placental barrier function by altering the expression of glucocorticoid-dependent genes and resulting in decreased availability of active glucocorticoids for the fetus, disturbing development and increasing the risk for metabolic and cardiovascular complications in later life.

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.

Populations Collapses in Marine Invertebrates Due to Endocrine Disruption: A Cause for Concern?

In the beginning of the twenty first century, the International Program on Chemical Safety published a document entitled Global Assessment of the State-Of-The-Science of Endocrine Disruptors. The work indicated only weak evidence of endocrine-related effects in human populations, and in wild animal populations. This document was revised in 2012 (State of the Science of Endocrine Disrupting Chemicals-2012) (1). The new document and the extensive scientific evidence it provided showed clearly that ED effects could be a risk to human and wildlife health. These works, however, were focused in human health and related animal models, mainly vertebrates and particularly mammals. It can be argued that invertebrates and many other taxa are important parts of all ecosystems, and, in many instances, have been shown to be also vulnerable to endocrine disruption. Thus, this work is aimed to show some observations on important marine invertebrate taxa, from an ecological point of view. The most important example of endocrine disruption in marine wild populations is the imposex response of marine gastropods, known for more than 40 years, and worldwide used to evaluate marine antifouling pollution. Among the mollusks, other important natural resources are bivalve species, used as human food sources and cephalopods, free-living, highly specialized mollusks, and also human food sources. Effects derived from endocrine disruptors in these species indicate that consumption could bring these compounds to human populations in an almost direct way, sometimes without any form of cooking or preparation. While discussing these questions, this work is also aimed to stimulate research on endocrine disruption among the invertebrate taxa that inhabited our oceans, and on which these effects are poorly known today.

Organotin compounds in touristic marinas of the northern Adriatic Sea: occurrence, speciation and potential recycling at the sediment-water interface

Butyltin compound (BTC) contamination was evaluated in two north Adriatic marinas, San Rocco (Italy) and Lucija (Slovenia). BTC sedimentary concentrations (121 ± 46 and 352 ± 30 ng Sn g^-1 in San Rocco and Lucija, respectively) evidenced the past use of antifouling paints, confirmed by the reduced tributyltin content (~ 46%) with respect to the sum of BTC. Elemental and organic carbon isotopic (δ¹³C) analyses of bulk sediments and its lipid and humic substances were performed in order to evaluate their role in BTC partitioning and preservation. The δ¹³C of sedimentary bulk and refractory organic matter suggested that diagenetic processes could play a role in the preservation or release of pollutants. No contamination was found in water collected from the benthic chamber and thus, fluxes at the sediment-water interface were not assessed, except for MBT efflux at Lucija (28.9 ng Sn m^-2 day^-1). Nevertheless, BTC concentrations in porewaters (up to 75 ng Sn l^-1) and rather low sediment-porewater partitioning coefficients (K_d) with respect to the data reported in the literature would suggest a potential risk of the reintroduction of BTC into the water column at both sites: at Lucija, sedimentary contamination is high despite the greater Log K_d, whilst at San Rocco, the low BTC concentration is associated with a reduced sediment affinity.

Organotin Release from Polyvinyl Chloride Microplastics and Concurrent Photodegradation in Water: Impacts from Salinity, Dissolved Organic Matter, and Light Exposure

Photochemical weathering leads to degradation of microplastics and releases chemical additives, polymeric fragments, and/or byproducts. This study evaluated the release kinetics of organotin compounds (OTCs) from three different sized (10-300 μm) polyvinyl chloride (PVC) microplastics under UV- and visible light irradiation. Four OTCs, dimethyltin (DMT), monomethyltin (MMT), dibutyltin (DBT), and monobutyltin (MBT), were found to release from PVC particles after 24 h leaching in darkness ranging from 2 to 20 μg·g-PVC^-1. Under UV/visible light irradiation, only DMT and DBT were detectable, whereas MMT and MBT were not detected due to rapid photodegradation. The total tin concentrations (including organic and inorganic tins) in the aqueous phase monotonically increased under light exposure. By contrast, they reached plateaus after 24 h in darkness, confirming the photodegradation of OTCs. A release kinetics model was established and correctly interpreted the microplastics size effect on the OTC release process. Finally, the impacts of salinity and dissolved organic matter (DOM) were investigated. The release and photodegradation of OTCs were both inhibited at high salinity conditions, probably due to the enhanced readsorption of OTCs on PVC microplastics and the formation of halogen radicals that were less reactive toward neutral OTCs. The presence of DOM, however, increased OTCs release probably because the excited state triplet DOM (³DOM*) formed and reacted with OTCs from PVC microplastics.

Potential roles of nuclear receptors in mediating neurodevelopmental toxicity of known endocrine-disrupting chemicals in ascidian embryos

Endocrine Disrupting Chemicals (EDCs) are molecules able to interfere with the vertebrate hormonal system in different ways, a major one being the modification of the activity of nuclear receptors (NRs). Several NRs are expressed in the vertebrate brain during embryonic development and these NRs are suspected to be responsible for the neurodevelopmental defects induced by exposure to EDCs in fishes or amphibians and to participate in several neurodevelopmental disorders observed in humans. Known EDCs exert toxicity not only on vertebrate forms of marine life but also on marine invertebrates. However, because hormonal systems of invertebrates are poorly understood, it is not clear whether the teratogenic effects of known EDCs are because of endocrine disruption. The most conserved actors of endocrine systems are the NRs which are present in all metazoan genomes but their functions in invertebrate organisms are still insufficiently characterized. EDCs like bisphenol A have recently been shown to affect neurodevelopment in marine invertebrate chordates called ascidians. Because such phenotypes can be mediated by NRs expressed in the ascidian embryo, we review all the information available about NRs expression during ascidian embryogenesis and discuss their possible involvement in the neurodevelopmental phenotypes induced by EDCs.

Organotin contamination in commercial and wild oysters from China: Increasing occurrence of triphenyltin

Organotin contamination in marine environment has been a public concern for many years due to its adverse impacts on biota and human health. This study investigated levels, distribution and health risks of six organotin compounds: tributyltin (TBT), dibutyltin (DBT), monobutyltin (MBT), triphenyltin (TPhT), diphenyltin (DPhT) and monophenyltin (MPhT) in commercial and wild oysters in China. The total organotin in commercial oysters ranged from 251 to 1949 ng Sn g^-1 dw (dry weight) >. Two endocrine disruptors TBT and TPhT were detected in these samples with the highest level of 68.1 ± 20.1 ng Sn g^-1 dw and 747 ± 7.3 ng Sn g^-1 dw, respectively. For wild oysters, the concentrations of total organotins varied from 33.3 to 2671 ng Sn g^-1 dw. Butyltins were dominated by TBT with the mean level of 26.1 ± 30.0 ng Sn·g^-1 dw and showed no significant spatial variation between the southern and northern coastal zones (p > 0.05). However, compared with the north, phenyltin levels especially TPhT were much higher in the south coastline (246-1484 ng Sn·g^-1 dw) due to the wider use of TPhT-based biocides in local mariculture and agriculture. Health risk assessment indicated that a daily exposure of TPhT-contaminated oysters (including commercial and wild ones) may pose adverse threats to human particularly children as the risk quotients (RQ) were higher than 1. Organotin contamination (e.g., TPhT) still occurs in the South China's coastal zones after the TBT ban, which deserves future research and effective measures to protect the marine ecosystem and human health.

Levels and trends of tributyltin (TBT) and imposex in dogwhelk (Nucella lapillus) along the Norwegian coastline from 1991 to 2017

The banning of organotin biocides, such as tributyltin (TBT), from use in marine antifouling paints is now leading to reproductive health recovery in marine gastropod populations all over the world. TBT induces so-called imposex (superimposition of male sexual characters onto females) in certain marine gastropods, such as the common dogwhelk Nucella lapillus. In this publication, the results of the Norwegian TBT and imposex monitoring in N. lapillus from the period 1991-2017 are presented. Significantly higher levels of TBT and imposex were measured in coastal areas close to shipping lanes along most of the coast prior to 2008 than afterwards. Levels started declining after restrictions were imposed on the use of TBT in all antifouling paint applications, with a total ban in 2008. In 2017, no sign of imposex was found in N. lapillus in any of the monitoring stations along the Norwegian coastline. Based on monitoring data shown herein, the importance of long-term biomonitoring and international chemical regulations, as well as the TBT and imposex story in general, are discussed.

Distribution of butyltins at dredged material dumping sites around the coast of China and the potential ecological risk

Previous research has found butyltin pollution at dumping sites, which are the final fate of dredged material mostly originating from harbors and navigation systems. The distribution and impacts of butyltins were assessed in sediments at 12 dumping sites of China. Total butyltins (monobutyltin, dibutyltin, and tributyltin) concentrations ranged from 1.76 to 486.62 ng Sn g^-1 dw. This study also presents evidence of considerable historic inputs of tributyltin (TBT) to Dumping sites 01, 05, 06, 08, 09 and 11, with evidence of heavier recent TBT input at Dumping site 04 and 10. The butyltin contamination at dumping sites was comparatively light and historic compared to research in other countries, but was more serious than other sea regions. TBT levels at Dumping site 09 probably have negative effects on biological systems. Overall, more attention should be paid to the level and impacts of butyltins in the sediment at dumping sites in China.

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

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

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.

Characterization and comparison of transcriptional activities of the retinoid X receptors by various organotin compounds in three prosobranch gastropods; Thais clavigera, Nucella lapillus and Babylonia japonica

Two cDNAs of RXR were isolated, for the first time, from the ivory shell, Babylonia japonica, and the transcriptional activities were tested in vitro to compare with other gastropod (Thais clavigera and Nucella lapillus) RXR isoforms. The transcriptional activities of all of these RXR isoforms were significantly induced by mammalian RXR agonist, 9-cis retinoic acid (9cRA). The transcriptional activity of T. clavigera RXR-1 was also examined by using 9cRA and 16 organotin compounds, and significant ligand-dependent transactivations were observed by 9cRA and 5 organotins (tributyltin (TBT), tetrabutyltin (TeBT), tripropyltin (TPrT), tricyclohexyltin (TcHT) and triphenyltin (TPhT)). These 5 organotins also induced significant transcriptional activities in N. lapillus and B. japonica RXR isoforms. These 4 organotins, except for TeBT, have been reported to promote the development of imposex after a month of a single injection each, using female T. clavigera. To investigate the function of gastropod RXR isoforms, the effects of mammalian specific pan-agonist, PA024, and pan-antagonist, HX531, were examined, and significant induction of transcriptional activity by PA024 was demonstrated in these gastropod RXR isoforms. The additions of HX531 significantly suppressed the transcriptional activities of these gastropod RXR isoforms by 9cRA and 5 organotins. Using the mammalian two retinoic acid response elements, the transcriptional activities by 2 agonists, 9cRA and PA024, were different among the RXR isoforms of each gastropod species. With retinoid X response element (RXRE), transcriptional activities of TcRXR-1, BjRXR-1, and NlRXRa were significantly higher than those of TcRXR-2, BjRXR-2, and NlRXRb. Transcriptional activities of TcRXR-2, BjRXR-2, and NlRXRb, however, were significantly higher than those of TcRXR-1, BjRXR-1, and NlRXRa with thyroid hormone response element, TREpal. Thus, induction of imposex in prosobranch gastropods is strongly suggested to be triggered by 9cRA and certain organotins, such as TBT and TPhT through the activation of RXRs. These gastropod RXRs might control the different gene transcription by forming homo- or heterodimer complex with their own isoforms. These findings will contribute to our understanding of the fundamentals of the endocrine system in molluscs, particularly on RXR signaling pathway.

From TBT to booster biocides: Levels and impacts of antifouling along coastal areas of Panama

Antifouling biocides in surface sediments and gastropod tissues were assessed for the first time along coastal areas of Panama under the influence of maritime activities, including one of the world's busiest shipping zones: the Panama Canal. Imposex incidence was also evaluated in five muricid species distributed along six coastal areas of Panama. This TBT-related biological alteration was detected in three species, including the first report in Purpura panama. Levels of organotins (TBT, DBT, and MBT) in gastropod tissues and surficial sediments ranged from <5 to 104 ng Sn g^-1 and <1-149 ng Sn g^-1, respectively. In addition, fresh TBT inputs were observed in areas considered as moderate to highly contaminated mainly by inputs from fishing and leisure boats. Regarding booster biocides, TCMTB and dichlofluanid were not detected in any sample, while irgarol 1051, diuron and DCOIT levels ranged from <0.08 to 2.8 ng g^-1, <0.75-14.1 ng g^-1, and <0.38-81.6 ng g^-1, respectively. The highest level of TBT (149 ng Sn g^-1) and irgarol 1051 (2.8 ng g^-1), as well as relevant level of DCOIT (5.7 ng g^-1), were detected in a marina used by recreational boats. Additionally, relatively high diuron values (14.1 ng g^-1) were also detected in the Panama Canal associate to a commercial port. DCOIT concentrations were associated with the presence of antifouling paint particles in sediments obtained nearby shipyard or boat maintenance sites. The highest levels of TBT, irgarol 1051, and diuron exceeded international sediment quality guidelines indicating that toxic effects could be expected in coastal areas of Panama. Thus, the simultaneous impacts produced by new and old generations of antifouling paints highlight a serious environmental issue in Panamanian coastal areas.

Tributyltin and Zebrafish: Swimming in Dangerous Water

Zebrafish has been established as a reliable biological model with important insertion in academy (morphologic, biochemical, and pathophysiological studies) and pharmaceutical industry (toxicology and drug development) due to its molecular complexity and similar systems biology that recapitulate those from other organisms. Considering the toxicological aspects, many efforts using zebrafish models are being done in order to elucidate the effects of endocrine disruptors, and some of them are focused on tributyltin (TBT) and its mechanism of action. TBT is an antifouling agent applied in ship's hull that is constantly released into the water and absorbed by marine organisms, leading to bioaccumulation and biomagnification effects. Thus, several findings of malformations and changes in the normal biochemical and physiologic aspects of these marine animals have been related to TBT contamination. In the present review, we have compiled the most significant studies related to TBT effects in zebrafish, also taking into consideration the effects found in other study models.