Accumulation and trophic transfer of organotins in a marine food web from the Danish coastal waters

Abnormalities in eelpout Zoarces viviparus upon chemical exposure

Elevated frequencies of abnormal embryos in female eelpout Zoarces viviparus have been demonstrated in Danish, Swedish and German monitoring programmes at certain geographic locations with high levels of anthropogenic input. Pollutants present in areas with high malformation frequencies were selected and tested in a controlled laboratory experiment for their potential to induce abnormalities among eelpout embryos upon injection into pregnant eelpout. Tributyltin, 2,3,7,8-tetrachlorodibenzo-p-dioxin, pyrene, nonylphenol, 2,2',4,4'-tetrabromophenylether and heptadecafluorooctanesulfonic acid were tested, either individually or combined. Generally, the chemicals were transferred to eggs and/or embryos. Some of the exposures increased the proportion of broods with more than 10% abnormal or 5% malformed embryos, although the average percentages of abnormal development were not affected. Spinal, cranial and eye deformities were evident, similarly to what is seen in nature. Some of the exposures resulted in increased percentages of females with as well a low reproductive capacity as embryos with a low condition index.

Temporal and spatial variability of organotins in an intermittent Mediterranean river

Organotin compounds (OTs) are exclusively anthropogenic and have been widely used for their biocidal properties and as stabilizers in various industrial applications. Hence organotins are common pollutants. Their high toxicity has led to their entry on the EU water framework's priority substances' list. However, few studies are available regarding their behaviour in surface waters, in particular, in intermittent Mediterranean rivers. The Vène is an intermittent river located in Languedoc-Roussillon, southern France. It is the main tributary of an important shellfish farming site: the Thau lagoon. The present study aims at establishing the presence of OTs on a 1.5 km long reach of the river into which a waste water treatment plant (WWTP) discharges. The study is carried out during steady-state flow conditions over two consecutive years and investigates potential OTs sources in everyday domestic activities. Routine field monitoring was carried out over a 5 month period during the springs of 2008 and 2009. The results establish the presence of butyltins and octyltins throughout the 1.5 km long reach at concentrations exceeding the maximum allowable concentration levels imposed by the water framework directive. The WWTP is recognized as an important OTs point source; however, using trace and rare earth elements as tracers, an urban stormwater sewage gutter is identified as a secondary source. Its impact on the river's pollutant loads is however variable in time because of flow intermittency. The paper discusses the need for specific monitoring and management schemes for intermittent rivers.

Reproductive impacts of tributyltin (TBT) and triphenyltin (TPT) in the hermaphroditic freshwater gastropod Lymnaea stagnalis

Tributyltin (TBT) and triphenyltin (TPT) are emblematic endocrine disruptors, which have been mostly studied in gonochoric prosobranchs. Although both compounds can simultaneously occur in the environment, they have mainly been tested separately for their effects on snail reproduction. Because large discrepancies in experimental conditions occurred in these tests, the present study aimed to compare the relative toxicity of TBT and TPT under similar laboratory conditions in the range of 0 ng Sn/L to 600 ng Sn/L. Tests were performed on the simultaneous hermaphrodite Lymnaea stagnalis, a freshwater snail in which effects of TPT were unknown. Survival, shell length, and reproduction were monitored in a 21-d semistatic test. Frequency of abnormal eggs was assessed as an additional endpoint. Triphenyltin hampered survival while TBT did not. Major effects on shell solidity and reproduction were observed for both compounds, reproductive outputs being more severely hampered by TBT than by TPT. Considering the frequency of abnormal eggs allowed increasing test sensitivity, because snail responses to TBT could be detected at concentrations as low as 19 ng Sn/L. However, the putative mode of action of the 2 compounds could not be deduced from the structure of the molecules or from the response of apical endpoints. Sensitivity of L. stagnalis to TBT and TPT was compared with the sensitivity of prosobranch mollusks with different habitats and different reproductive strategies.

Evidence of butyltin biomagnification along the Northern Adriatic food-web (Mediterranean Sea) elucidated by stable isotope ratios

The biomagnification of tributyltin (TBT), dibutyltin (DBT), monobutyltin (MBT), and total butyltins (ΣBT) was analyzed in the Northern Adriatic food-web (Mediterranean) considering trophodynamic interactions among species and carbon sources in the food-web. Although it is acknowledged that these contaminants bioaccumulate in marine organisms, it is still controversial whether they biomagnify along food-webs. A wide range of species was considered, from plankton feeders to top predators, whose trophic level (TL) was assessed measuring the biological enrichment of nitrogen stable isotopes (δ(15)N). Carbon isotopic signature (δ(13)C) was used to trace carbon sources in the food-web (terrestrial vs marine). At least one butyltin species was detected in the majority of samples, and TBT was the predominant contaminant. A significant positive relationship was found between TL and butyltin concentrations, implying food-web biomagnification. Coherently, the Trophic Magnification Factor resulted higher than 1, ranging between 3.88 for ΣBT and 4.62 for DBT. A negative but not significant correlation was instead found between δ(13)C and butyltin concentrations, indicating a slight decreasing gradient of contaminants concentrations in species according to the coastal influence as carbon source in their diet. However, trophodynamic mechanisms are likely more important factors in determining butyltin distribution in the Northern Adriatic food-web.

Resistance to oxidative damage but not immunosuppression by organic tin compounds in natural populations of Daubenton's bats (Myotis daubentonii)

The acute toxicity of organic tin compounds (OTCs) has been studied in detail. However, due to their complex nature, very little is known about species-specific methods of accumulation and consequences for food-webs. Chironomids, on which e.g. Daubenton's bats feed, may act as vectors for the transport of organic tin compounds from aquatic to terrestrial ecosystems. Bats are prone to environmental toxins because of their longevity and their ecological role as top predators. Organic tin compounds are associated with increased formation of reactive oxygen species and associated oxidative damage as well as suppression of immune function. The present paper investigates whether the OTC, tributyltin (TBT) and its metabolite, dibutyltin (DBT), accumulate in natural populations of Daubenton's bats and whether TBT-associated effects are seen in general body condition, redox balance, redox enzyme activities, associated oxidative damage of red blood cells and complement function. We discovered the concentration of bat fur DBT correlated with local marine sediment TBT concentrations. However, we did not find a correlation between the explanatory factors, bat fur DBT and marine sediment TBT concentrations, and several physiological and physical response variables apart from complement activity. Higher DBT concentrations resulted in weaker complement activity and thus a weaker immune response. Although the observed physiological effects in the present study were not strongly correlated to butyltin concentrations in fur or sediment, the result is unique for natural populations so far and raises interesting questions for future ecotoxicological studies.

Review of measured concentrations of triphenyltin compounds in marine ecosystems and meta-analysis of their risks to humans and the environment

The state of scientific knowledge regarding analytical methods, environmental fate, ecotoxicity and ecological risk of triphenyltin (TPT) compounds in marine ecosystems as well as their exposure and health hazard to humans was reviewed. Since the 1960s, TPT compounds have been commonly applied as biocides for diverse industrial and agricultural purposes. For instance, they are used as active ingredients in antifouling systems on marine vessels and mariculture facilities, and as fungicides in agriculture. Due to their intensive use, contamination of coastal waters by TPT and its products of transformation has become a worldwide problem. The proportion of quantified TPT to total phenyltin compounds in the marine environment provides evidence that TPT is photodegradable in water and sediment but resistant to biotransformation. Concentrations of TPT in marine biota are consistently greater than concentrations in water and sediment, which implies potential of TPT to bioaccumulate. TPT is toxic to both marine plants and animals. The predicted no effect concentration (PNEC) for TPT, as determined by use of the species sensitivity distribution approach, is 0.64 ng L(-1). In some parts of the world, concentrations of TPT in seawater exceed the PNEC, indicating that TPT can pose risks to marine life. Although there is negligible risk of TPT to average human consumers, TPT has been detected in blood of Finnish people and the concentration was greater in fishermen who ate more seafood. It is, therefore, advocated to initiate regular monitoring of TPT in blood and breast milk of populations that consume greater amounts of seafood.

Intake and potential health risk of butyltin compounds from seafood consumption in Korea

Concentrations of butyltin compounds (BTs) were determined in 47 species of seafood commonly consumed in Korea to investigate intakes of BTs from seafood consumption and the potential health risks to the Korean population. The concentrations of BTs (the sum of dibutyltin and tributyltin) in seafood ranged from less than the limit of detection to 96.3 ng/g wet weight, which are levels similar to those reported for other countries. The intake of BTs from seafood consumption by the general population was estimated to be 17.2 ng/kg body weight/day. Fish accounted for 50% of the total intakes of BT, and the next contributor was cephalopods (26%). The estimated intakes for males and females were 18.6 and 15.7 ng/ kg body weight/day, respectively. Among the age groups investigated, children (<2 years and 3-6 years) had higher intakes of BTs compared with adults. The estimated intake of BTs for Korean population groups was 5-8% of the tolerable daily intake of 250 ng/ kg body weight/day set by the European Food Safety Authority. Our results suggest that the Korean population is not expected to exceed the threshold value for adverse health effects.

Influence of triphenyltin exposure on the hypothalamus-pituitary-gonad axis in male Sebastiscus marmoratus

Both triphenyltin (TPT) and tributyltin (TBT) have been used as ingredients of antifouling biocides. However, far fewer studies addressing the reproductive toxicity of TPT on fishes are available than for TBT. The present study was conducted to investigate the effects of TPT at environmentally relevant concentrations on testicular development in male rockfish Sebastiscus marmoratus and to gain insight into its mechanism of action. After exposure for 48 days, the gonadosomatic index had decreased, and there was a reduced number of mature sperm and an abundance of the late stages of spermatocysts in the testes. Although the testosterone levels in the testes were elevated and the 17β-estradiol levels were decreased, spermatogenesis was suppressed. The activity of γ-glutamyl transpeptidase (which is used as a Sertoli cell marker) was decreased after TPT exposure, and serious interstitial fibrosis was observed in the interlobular septa of the testes exposed to TPT. The increased expression of cGnRH-II (chicken-II type gonadotropin-releasing hormone) and sGnRH (salmon-type GnRH), and the decreased expression of LHβ (luteinizing hormone) in the fish brains were detected. The expression of FSHβ (follicle-stimulating hormone) was decreased at day 21, while was increased slightly at day 48. The changes of cGnRH-II, sGnRH, FSHβ and LHβ mRNA levels might have mainly resulted from the alteration of the sex steroids via feedback mechanisms. The decrease of the FSHβ mRNA might have been one of the reasons causing the dysfunction of Sertoli cells, which play a critical role during spermatogenesis. The results suggested that TPT could perturb the function of hypothalamus-pituitary-gonad axis, and inhibiting the spermatogenesis.

Combinatorial materials research applied to the development of new surface coatings XV: an investigation of polysiloxane anti-fouling/fouling-release coatings containing tethered quaternary ammonium salt groups

As part of ongoing efforts aimed at the development of extensive structure−property relationships for moisture-curable polysiloxane coatings containing tethered quaternary ammonium salt (QAS) moieties for potential application as environmental friendly coatings to combat marine biofouling, a combinatorial/high-throughput (C/HT) study was conducted that was focused on four different compositional variables. The coatings that were investigated were derived from solution blends of a silanol-terminated polydimethylsiloxane (HO-PDMS-OH), QAS-functional alkoxysilane, and methyltriacetoxysilane. The compositional variables investigated were alkoxysilane functionality of the QAS-functional silane, chain length of the monovalent alkyl group attached to the QAS nitrogen atom, concentration of the QAS-functional alkoxysilane, and molecular weight of the HO-PDMS-OH. Of these variables, the composition of the alkoxysilane functionality of the QAS-functional silane was a unique variable that had not been previously investigated. The antifouling (AF) and fouling-release (FR) characteristics of the 24 unique coating compositions were characterized using HT assays based on three different marine microorganisms, namely, the two bacteria, Cellulophaga lytica and Halomonas pacifica, and the diatom, Navicula incerta. Coatings surfaces were characterized by surface energy, water contact angle hysteresis, and atomic force microscopy (AFM). A wide variety of responses were obtained over the compositional space investigated. ANOVA analysis showed that the compositional variables and their interactions significantly influenced AF/FR behaviors toward individual marine microorganisms. It was also found that utilization of the ethoxysilane-functional QASs provided enhanced AF character compared to coatings based on methoxysilane-functional analogues. This was attributed to enhanced surface segregation of QAS groups at the coating-air interface and confirmed by phase images using AFM.

Interspecies differences in the accumulation of tributyltin and its metabolites under dietary exposure in sea perch, Lateolabrax japonicus, and red sea bream, Pagrus major

Interspecies differences in the accumulation of dietary tributyltin (TBT) between sea perch, Lateolabrax japonicus, and red sea bream, Pagrus major, were studied. Although TBTs in both species reached steady-state condition in low-concentration group (L-group, 200 ng/g nominal concentration) by 1 week, it increased up to the end of exposure in high-concentration group (H-group, 3000 ng/g nominal concentration). In H-group, the accumulation rate of TBT in sea perch from 1 to 2 weeks was much higher than in red sea bream, which were 2.4-fold for sea perch and 1.7-fold for red sea bream, although TBT concentrations were similar between sea perch and red sea bream in L-group. Furthermore, in the H-group, the concentrations of TBT at 1 and 2 weeks were about 1.3- and 1.9-fold, respectively, higher in the sea perch than in the red sea bream. On the other hand, DBT residue in red sea bream was about 1.4-fold higher in sea perch for the L-group but concentrations were similar in both fishes for the H-group. These results suggest that red sea bream could metabolize faster the TBT to DBT than sea perch. This study also reveals that fish probably could absorb TBT through the food chain. The uptake of TBT by fish should be regarded in the real environment, because TBT concentration in seawater has been decreasing and now already at significantly low level.

Immune-regulatory transcriptional responses in multiple organs of Atlantic salmon after tributyltin exposure, alone or in combination with forskolin

Tributyltin (TBT) is a widespread marine pollutant that influences physiological conditions of fish and other aquatic organisms. In addition to effects on reproduction, the immune system has been proposed as a possible target for TBT effects. In the present study, the effects of TBT exposure were examined on the expression of genes involved in immune system compentence in liver and head kidney of Atlantic salmon, in the presence and absence of a second-messenger activator (forskolin). Juvenile salmon were force-fed a diet containing TBT (0-solvent control, 0.1, 1, or 10 mg/kg fish) for 72 h. Consequently, fish from the control group and 10-mg/kg TBT group were exposed to the adenylate cyclase (AC) activator forskolin (200 μg/L) for 2 or 4 h. Forskolin was selected for this study because it is known to exhibit potent immune system enhancement by activating macrophages and lymphocytes. After sacrifice, liver and head kidney were sampled and transcript changes for interleukin (IL)-1β, IL-10, transforming growth factor (TGF) β, interferon (INF) α, INFγ, tumor necrosis factor (TNF) α, Mx3, and insulin-like growth factor (IGF)-1 were determined in both tissues by quantitative polymerase chain reaction (qPCR) using gene-specific primers. TBT, when given alone and also in combination with forskolin, decreased IL-1β, TNFα, IFNγ, IFNα, Mx3, and IGF-1 gene expression. In contrast, IL-10 and TGFβ transcripts were increased after TBT exposure alone and also in combination with forskolin. Generally, these effects were largely dependent on TBT dose and time of exposure when given in combination with forskolin. Overall, our findings suggest a possible immunomodulatory effect of TBT, possibly involving cAMP activation.

The obesogen hypothesis: a shift of focus from the periphery to the hypothalamus

The obesogen concept proposes that environmental contaminants may be contributing to the epidemic of obesity and its related pathology, metabolic disorder. The first references to such a notion appeared at the beginning of the current decade, with the hypothesis that the correlation between increasing incidence of obesity and enhanced industrial chemical production was not simply coincidental, but potentially causally related. The next event was the introduction of the term "obesogen" as representing an environmental pollutant that adversely affects various aspects of adipose tissue functions. More recently, the concept was extended to include substances that may modify metabolic balance at the central, hypothalamic level. The actions of two prime candidate obesogens, tributyltin (TBT) and tetrabromobisphenol A (TBBPA), acting at the central level are the main focus of this review. Having discussed the evidence for contaminant accumulation in the environment and in human tissues and the potential mechanisms of action, data are provided showing that these two widespread pollutants modify hypothalamic gene regulations. Our studies are based on maternal exposure and measurement of effects in the progeny, mainly based on in vivo gene reporter assays. Such models are obviously pertinent to testing current hypotheses that propose that early exposure might exert effects on later development and physiological functions. The potential molecular mechanisms involved are discussed, as are the broader physiological consequences of these hypothalamic dysregulations.

[Preferential induction of apoptosis in regulatory T cells by tributyltin: possible involvement in the exacerbation of allergic diseases]

OBJECTIVES

Tributyltin (TBT) has been recognized as a particularly important pollutant. Human exposure to TBT persists via consumption of TBT-containing meat and fish products. Although it is well known that high-dose TBT exerts immunotoxic effects such as thymic atrophy, the effect of low-dose TBT exposure on immune responses remains elusive. Our previous studies demonstrated that TBT at environmentally relevant doses promoted T helper (Th)2 polarization via enhancement of Th2 differentiation and preferential induction of apoptosis in Th1, which is associated with the exacerbation of Th2-driven allergic airway inflammation. In the present study, we explored the possibility that TBT might preferentially induce apoptosis in Foxp3(+) regulatory T cells (Treg), which play an indisputable role in the negative regulation of immune responses.

METHODS

We established several independent Treg and Th2 clones and their susceptibilities to TBT-induced apoptosis were examined. To examine whether the susceptibility to TBT-induced apoptosis may be due to the level of glutathione (GSH), we measured the basal GSH levels in Treg and Th2 clones. Intracellular GSH level was measured using high-performance liquid chromatography (HPLC) with a gold electrode.

RESULTS

We show that TBT preferentially induces apoptosis in Treg clones rather than in Th2 clones. The basal levels of GSH in Treg clones were significantly lower than those in Th2 clones.

CONCLUSIONS

The increased susceptibility of Treg clones to TBT-induced apoptosis appeared to result from lower GSH levels in Treg clones, which may detoxify the reactive oxygen species (ROS) induced by TBT treatment. Our results suggest that the preferential induction of apoptosis in Treg over Th2 contributes to the exacerbation of Th2-driven allergic diseases by TBT.

Efficient induction of CCR9 on T cells requires coactivation of retinoic acid receptors and retinoid X receptors (RXRs): exaggerated T Cell homing to the intestine by RXR activation with organotins

The active vitamin A metabolite retinoic acid (RA) imprints gut-homing specificity on lymphocytes upon activation by inducing the expression of α4β7 integrin and CCR9. RA receptor (RAR) activation is essential for their expression, whereas retinoid X receptor (RXR) activation is not essential for α4β7 expression. However, it remains unclear whether RXR activation affects the RA-dependent CCR9 expression on T cells and their gut homing. The major physiological RA, all-trans-RA, binds to RAR but not to RXR at physiological concentrations. Cell-surface CCR9 expression was often induced on a limited population of murine naive CD4(+) T cells by all-trans-RA or the RAR agonist Am80 alone upon CD3/CD28-mediated activation in vitro, but it was markedly enhanced by adding the RXR agonist PA024 or the RXR-binding environmental chemicals tributyltin and triphenyltin. Accordingly, CD4(+) T cells treated with the combination of all-trans-RA and tributyltin migrated into the small intestine upon adoptive transfer much more efficiently than did those treated with all-trans-RA alone. Furthermore, naive TCR transgenic CD4(+) T cells transferred into wild-type recipients migrated into the small intestinal lamina propria following i.p. injection of Ag, and the migration was enhanced by i.p. injection of PA024. We also show that PA024 markedly enhanced the all-trans-RA-induced CCR9 expression on naturally occurring naive-like regulatory T cells upon activation, resulting in the expression of high levels of α4β7, CCR9, and Foxp3. These results suggest that RXR activation enhances the RAR-dependent expression of CCR9 on T cells and their homing capacity to the small intestine.

Concentrations of organotin compounds in various fish species in the Finnish lake waters and Finnish coast of the Baltic Sea

Organotin compounds (OTCs) leaching from the antifouling paints used in boats and ships have contaminated many water areas worldwide. The purpose of this study was to obtain a general view of the organotin contamination in fish in Finnish lake areas and Finnish coast of the Baltic Sea using perch as the main indicator species. Perch sampling covered areas presumed as less contaminated and areas suspected as more contaminated. Besides perch, 12 other species were sampled from sites presumed as less contaminated. OTCs measured were mono-, di- and tributyltin, mono-, di-, and triphenyltin and dioctyltin. The sum concentration of OTCs (SigmaOTCs) in perch in the least contaminated areas of the Baltic Sea were around 20 ng/g fresh weight (fw) and less than 10 ng/g fw in lake areas. In heavily contaminated areas of the Baltic Sea 150-500 ng/g fw in perch were detected. In lake areas the maximum SigmaOTCs in perch was only 30 ng/g fw. With regard to the other species in the Baltic Sea, salmon, sprat, flounder, whitefish, vendace and lamprey contained low concentrations (SigmaOTCs mainly less than 20 ng/g fw), whereas in pike, pike-perch, burbot and bream concentrations were higher. SigmaOTCs in lake fish were generally lower than in the Baltic Sea. In a distance gradient study, SigmaOTCs in perch decreased quickly from nearly 200 ng/g fw at a contaminated harbor area to 35 ng/g fw during a distance of 5 km. Further decrease was slower and reached 15 ng/g fw at 100 km. In a size dependence study triphenyltin showed better correlation with the fish length than tributyltin for all species studied, i.e. for perch (0.16 vs 0.26), pike-perch (0.13 vs 0.24) and roach (0.46 vs 0.80). High correlation for roach may be partly explained by smaller number of samples collected and small length range.

Bioaccumulation of mercury in the pelagic food chain of the Lake Baikal

Mercury (Hg) concentrations were analyzed in the livers of Baikal seals and in plankton, zoobenthos and fish which constitute food items for the seals. Concentrations of Hg in the liver of Baikal seals were up to two orders of magnitude lower than those in seals inhabiting other lakes. The low levels of Hg are due to the low levels of the Hg in the fish from the family Comephoride, which reflect the very low concentrations of Hg in Baikal water. The development stage (pups and adults) and the sex of the seals have significant influence on their hepatic Hg concentrations. The differences between Hg accumulation in adult males, adult females and pups could be attributed to the reproductive cycle of the Baikal seals. In spite of low concentrations, Hg is characterized by high values of the concentration factor (CF) for the livers of for Baikal seals. Biomagnification factors (BMFs) suggest biomagnifications of Hg in the fish-seal trophic link.

Ecological impacts of tributyltin on estuarine communities in the Hastings River, NSW Australia

Oyster (Saccostrea commercialis) biomonitoring, assessment of oyster and gastropod (Bembicium auratum) abundance, and gastropod imposex were used to measure the significance of tributyltin (TBT) contamination in an intertidal mangrove forest. We studied the bioavailable levels of TBT in oysters approximately 1 km downstream and 2 km upstream from a TBT waste disposal site. We found observable declines in the abundance of oysters and gastropods correlated with the bioavailable TBT and these findings were confirmed by mapping oyster beds. Oyster cover near the disposal site ranged from 0% to 5% while downstream and upstream populations ranged in cover from 25-50% to 5-25%, respectively. Similarly, gastropod abundances at the disposal site were only 7% of the downstream population and 17% of the upstream population. Imposex was present in 90% of female B. auratum from populations near the disposal site but this effect declined more sharply than the population level effects.

Environmental genotoxicity and cytotoxicity in the offshore zones of the Baltic and the North Seas

Micronuclei (MN), nuclear buds (NB) and fragmented-apoptotic cells (FA) were analyzed in mature peripheral blood and immature cephalic kidney erythrocytes of flounder (Platichthys flesus), dab (Limanda limanda) and cod (Gadus morhua) from 12 offshore sites in the Baltic Sea (479 specimens) and 11 sites in the North Sea (291 specimens), which were collected during three research vessel cruises in December 2002, 2003 and in September 2004. The highest levels of environmental genotoxicity (frequencies of MN up to 0.5 per thousand, NB - up to 0.75 per thousand) and cytotoxicity (FA - up to 0.53 per thousand) were observed in flatfishes from areas close to oil and gas platforms in the North Sea and in zones related to the extensive shipping and potentially influenced by contamination from large European Rivers (Elbe, Vistula, Oder). In dab from the offshore zones of the North Sea, the levels of nuclear abnormalities were higher as compared to those in dab from the Baltic Sea. Responses in immature kidney erythrocytes were higher than in mature erythrocytes from peripheral blood. MN frequency lower than 0.05 per thousand (the Baltic Sea) and lower than 0.1 per thousand (the North Sea) could be suspected as a reference level in the peripheral blood erythrocytes of flatfish.

Anti-Biofouling Property of a Novel Cross-Linkable Copolymer Grafted a Short Semifluorinated Aromatic Side Chain

Biofouling on underwater engineered structures, especially on ship hulls, results in increased operational and maintenance costs. The traditional methods of protecting marine structures have been the use of toxic antifoulants, such as lead, mercury and tributyltin compounds (TBT). Such heavy metals have proven to be effective in deed, but severe shellfish deformities and the bioaccumulation of heavy metals in ducks, seals and fish lead to the global ban of toxic antifoulants. Therefore, our antifouling strategy is to develop minimally adhesive, mechanically stable and nontoxic fouling release coatings which degrade fouling an organism’s ability to adhere to surfaces. Herein we report on the synthesis and characterization of a novel cross-linkable copolymer grafted a semifluorinated aromatic side chain which was prepared by copolymerization with methyl methacrylate and glycidyl methacrylate. Bulk and surface properties were assessed through 1H NMR and 19F NMR spectra, contact angle measurement. The cross-linkable copolymer was rationally designed for use as coating to prevent marine bioufouling. Apart from the use of methyl methacrylate and glycidyl methacrylate which contained epoxide ring serving as a cross-linked group, the other important monomer―a semifluorinated group substituted styrene monomer was selected to construct a low surface energy material. Finally, the antifouling potential of the designed polymer surface was evaluated employing the fouling diatom Nitzschia in our laboratory. Experimental results indicated the combination of the low surface energy group (semifluorinated segments) and linker group (epoxide ring) allowed the cross-linkable polymer surface possessing a little better antifouling properties than that a standard poly(dimethyl siloxane) (PDMS) coating.

Butyltin compounds and their relation with organic matter in marine sediments from San Vicente Bay-Chile

Tributyltin and its degradation products, mono-and dibutyltin have been determined in sediments collected in some representative sites in San Vicente Bay, Chile. The organic matter contents of sediments and water collected simultaneously from the same sampling sites were also determined. High levels of total organic carbon were found in sediments, especially in those from the northern part of the bay (1.80-8.87%). Good correlations were found between total organic carbon and the oxidizable and refractory carbon fractions. Among the butyltin species determined, TBT presented the highest levels, ranging from 14 to 1,560 ng Sn g(-1) dry weight. Concentration ratios of TBT to DBT ranged between 1.33 and 3.10, showing a high degree of contamination in sediments of this Chilean bay. All data obtained were analysed by the chemometric method of principal components analysis. A strong correlation was found between TBT and DBT concentrations in sediments, the different organic matter contents in sediments and water. In marine organisms only TBT was detected, containing the filterer organism Semele solida higher level than Perumytilus purpuratus and Pyura chilensis (220, 150 and 120 ng Sn g(-1) dry weight, respectively). For the alga Rodoficea iridae the TBT concentration was 60 ng Sn g(-1) dw. Comparatively, these values are higher than those reported for the same kind of marine organisms worldwide. The different samples from San Vicente Bay were found to be contaminated by TBT. This contamination can be attributed to the different anthropogenic activities taking place in the bay.

Malformations of the endangered Chinese sturgeon, Acipenser sinensis, and its causal agent

The anadromous Chinese sturgeon (Acipenser sinensis) is endangered and listed among the first class of protected animals in China. The possible causes for the decline of this species are the effects of synthetic chemicals, and loss of critical habitat. Chinese sturgeon in the Yangtze River have accumulated triphenyltin (TPT) to 31-128 ng/g wet weigh (ww) in liver, which is greater than the concentrations of tributyltin (<1.0 ng/g ww). Maternal transfer of TPT has resulted in concentrations of 25.5 +/- 13.0 ng/g ww in eggs of wild Chinese sturgeon, which poses a significant risk to the larvae naturally fertilized or hatched in the Yangtze River. The incidence of deformities in fry was 7.5%, with 1.2% of individuals exhibiting ocular abnormal development, and 6.3% exhibited skeletal/morphological deformations. The incidences of both ocular and skeletal/morphological deformations were directly proportional to the TPT concentration in the eggs of both the Chinese sturgeon and the Siberian sturgeon (Acipenser baerii) in controlled laboratory studies. The rates of deformities in the controlled studies were consistent with the rates caused at the similar concentrations in eggs collected from the field. Thus, TPT is the causal agent to induce the malformation of larvae of Chinese sturgeon. The incidence of deformed larvae of Chinese sturgeon is an indicator of overall population-level effects of TPT on Chinese sturgeon, because TPT at environmentally relevant concentrations can result in significantly decrease both quality and quantity of eggs and spawning frequency of fish.

Endocrine disrupters as obesogens

The recent dramatic rise in obesity rates is an alarming global health trend that consumes an ever increasing portion of health care budgets in Western countries. The root cause of obesity is thought to be a prolonged positive energy balance. Hence, the major focus of preventative programs for obesity has been to target overeating and inadequate physical exercise. Recent research implicates environmental risk factors, including nutrient quality, stress, fetal environment and pharmaceutical or chemical exposure as relevant contributing influences. Evidence points to endocrine disrupting chemicals that interfere with the body's adipose tissue biology, endocrine hormone systems or central hypothalamic-pituitary-adrenal axis as suspects in derailing the homeostatic mechanisms important to weight control. This review highlights recent advances in our understanding of the molecular targets and mechanisms of action for these compounds and areas of future research needed to evaluate the significance of their contribution to obesity.

Minireview: the case for obesogens

Obesity and obesity-related disorders, such as type 2 diabetes, hypertension, and cardiovascular disease, are epidemic in Western countries, particularly the United States. The conventional wisdom holds that obesity is primarily the result of a positive energy balance, i.e. too many calories in and too few calories burned. Although it is self-evident that fat cannot be accumulated without a higher caloric intake than expenditure, recent research in a number of laboratories suggests the existence of chemicals that alter regulation of energy balance to favor weight gain and obesity. These obesogens derail the homeostatic mechanisms important for weight control, such that exposed individuals are predisposed to weight gain, despite normal diet and exercise. This review considers the evidence for obesogens, how they might act, and where future research is needed to clarify their relative contribution to the obesity epidemic.

The legal design of the international and European Union ban on tributyltin antifouling paint: direct and indirect effects

The Convention on the Control of Harmful Anti-fouling Systems on Ships (AFS Convention), which was adopted in 2001 and will come into force in September 2008, bans the use of TBT (tributyltin) antifouling paint on ships. The EU (European Union) effectively implemented the Convention on 1 January 2008 by enforcing a similar ban. Several states have national restrictions and bans in place. The regulation on TBT antifouling paint aims at checking the risk of adverse effects on marine ecosystems. The legal and political situation is, however, characterized by complex relations between different layers of legislation, the use of several different legal techniques, and levels of ambition. The international and EU bans thereby cause some indirect effects, which are only partly included in what is seen as 'the TBT issue' and so only partly assessed in the legal process of the ban. This article discusses the expediency of the existing legislation and legal strategies aimed at reducing the negative environmental effects of TBT-like toxins in marine ecosystems and indirect effects of such actions. It considers the adequacy and limits of current regulatory approaches for handling complex environmental problems, such as TBT in antifouling paint.

TBT contamination of remote marine environments: ship groundings and ice-breakers as sources of organotins in the Great Barrier Reef and Antarctica

Remote marine environments such as many parts of the Great Barrier Reef (GBR) and the Antarctic are often assumed to be among the most pristine natural habitats. While distance protects them from many sources of pollution, recent studies have revealed extremely high concentrations of organotins in areas associated with shipping activities. Sediments at sites of ship groundings on the GBR have been found to contain up to 340,000 microg Sn kg(-1). Very high concentrations (up to 2290 microg Sn kg(-1)) have been detected in nearshore Antarctic sediments adjacent to channels cut through sea ice by ice-breaking vessels. In both cases, the bulk of the contamination is associated with flakes of antifouling paint abraded from vessel hulls, resulting in patchy but locally intense contamination of sediments. These particulates are likely to continue releasing organotins, rendering grounding sites and ice-breaking routes point-sources of contamination of surrounding environments. While the areas exposed to biologically-harmful concentrations of leached chemicals are likely to be limited in extent (1000-10,000 m(2)), deposition of antifouling paints constitutes a persistent ecological risk in otherwise pristine marine environments of high conservation value. The risk of contamination of GBR and Antarctic sediments by organotins needs to be considered against an important alternative risk: that less effective antifouling of ships hulls may increase the frequency of successful invasions by non-indigenous species. Additional options to minimise ecological risk include accident prevention and reducing organotin contamination from grounding sites through removal or treatment of contaminated sediments, as has been done at some sites in the GBR.

The effect of in vitro exposure to tributyltin on the immune competence of Chinook salmon (Oncorhynchus tshawytscha) leukocytes

We evaluated the direct effects of in vitro exposures to tributyltin (TBT), a widely used biocide, on the cell-mediated immune system of Chinook salmon (Oncorhynchus tshawytscha). Splenic and pronephric leukocytes isolated from juvenile Chinook salmon were exposed to TBT (0, 0.1, 0.2, 0.3, 0.4, 0.5, and 0.6 mg/l) in cell cultures for 24 h. Effects of TBT on cell viability, induction of apoptosis, and mitogenic responses were measured by flow cytometry. Splenic and pronephric leukocytes in the presence of TBT experienced a concentration-dependent decrease in viability in cell cultures. Apoptosis was detected as one of the mechanisms of cell death after TBT exposure. In addition, pronephric lymphocytes exhibited a greater sensitivity to TBT exposure than pronephric granulocytes. The functional ability of splenic B-cells to undergo blastogenesis upon lipopolysaccharide stimulation was also significantly inhibited in the presence of 0.05, 0.07, or 0.10 mg/l of TBT in the cell cultures. Flow cytometric assay using a fluorescent conjugated monoclonal antibody against salmon surface immunoglobulin was employed for the conclusive identification of B-cells in the Chinook salmon leukocytes. Our findings suggest that adverse effects of TBT on the function or development of fish immune systems could lead to an increase in disease susceptibility and its subsequent ecological implications.

Biomagnification profiles of tributyltin (TBT) and triphenyltin (TPT) in Japanese coastal food webs elucidated by stable nitrogen isotope ratios

The measurement of organotins in the various biotas of coastal food webs with stable nitrogen isotope ratios (delta(15)N), which increase 3.4 per thousand per trophic level, can provide a biomagnification profile of organotins through food web. In this study, various biological samples were collected from three localities in Western Japan between 2002 and 2003 for analyses. Tributyltin (TBT) and triphenyltin (TPT) were still detected with a maximum of 99.5 and 8.7 ng wet weight g(-1), respectively. Unlike TBT, significant biomagnification of TPT through the food web (expressed by delta(15)N) was found in all three localities. The log transformed octanol-water partition coefficient (log K(ow)) of TPT of 2.11-3.43 was overlapped by, but was slightly lower than, that of TBT of 3.70-4.70. Thus, this study demonstrates that although these chemicals have a log K(ow) lower than 5, at least TPT undergoes significant biomagnification through the food web.

Reproductive inhibition and transgenerational toxicity of triphenyltin on medaka (Oiyzias latipes) at environmentally relevant levels

An increasing number of studies have reported unexpectedly high body burdens of triphenyltin (TPT) in wild fishes around the world. To assess the effects of TPT on fish, we exposed pairs of medaka (Oryzias latipes) to different levels of TPT for 5 weeks, and the reproduction responses and transgenerational effects were studied. The results demonstrated that TPT exposure markedly suppressed the spawning frequency, spawned egg number, egg quality and gonad development, and induced teratogenesis, such as hemorrhaging, eye defects, morphological malformation and conjoined twins, less hatchability, and swim-up failure in the F1 generation, thereby resulting in a significant decrease in the capacity to produce viable offspring (p < 0.01). The residual TPT levels in the exposure fish are in the range of 6.52 +/- 0.56 to 5595 +/- 1016 ng of TPT/g of wet weight, similar to those reported in wild fish around the world, indicating TPT contamination in the real world would have a significant adverse effect on the health of fish population. Down-regulation of vitellogenin (VTG) genes in the female of the TPT exposure groups was recognized as a cause for the decreased fecundity. Expressions of VEGFs and PAX6 associated with vascular or ocular development respectively, were measured in hemorrhaging and eye defects embryos and showed good correlations with response outcomes.

Tributyltin impairs dentin mineralization and enamel formation in cultured mouse embryonic molar teeth

Tributyltin (TBT), earlier used as an antifouling agent in marine paints, causes damage to the aquatic ecosystem, for example, impaired shell calcification in oysters. TBT affects hard tissue mineralization even in mammals: delayed bone mineralization has been observed in rodents exposed to TBT in utero. To see if TBT interferes with tooth development, especially dental hard tissue formation, we exposed mouse E18 mandibular first and second molars to 0.1, 0.5, 1.0, and 2.0 microM TBT chloride in organ culture for 7-12 days. The amount of enamel was assessed and the sizes of the first molars were measured from photographs taken after the culture. TBT concentration dependently impaired enamel formation (p < 0.001) and reduced tooth size (p < 0.001). Histological analysis showed slight arrest of dentin mineralization and enamel formation in first molars exposed to 0.1 microM TBT. At the concentration of 1.0 microM the effect was overt. The differentiation of ameloblasts in the mesial cusps was retarded but TBT had no effect on odontoblast morphology. The dental epithelium showed enhanced apoptosis. The failure of ameloblasts to form enamel was likely to be secondary to the effect of TBT on dentin mineralization. In the second molars, where predentin deposition had not started, ameloblasts and odontoblasts were nonpolarized and proliferative. The results showed that TBT concentration dependently impairs dental hard tissue formation and reduces tooth size in cultured mouse embryonic molars. The effects depend on the stage of tooth development at the start of exposure and may involve epithelial-mesenchymal interactions.

Inshore/offshore gradients of imposex and organotin contamination in Nassarius reticulatus (L.) along the Portuguese coast

Imposex and organotin (OT) tissue contamination of the netted whelk Nassarius reticulatus (L.) were assessed in the continental shelves around the main estuaries of the central coast of Portugal (Lisbon: Tagus estuary; Setúbal: Sado estuary) and the main coastal lagoon in the Southern of Portugal (Faro: Ria Formosa). Pollution levels were higher in areas of more intense boat traffic and shipyard activities and imposex showed a clear decreasing gradient from the estuaries to the offshore, in relation to a similar gradient of tissue contamination by tributyltin. Remarkably, imposex was extensively spread over the adjacent continental shelves of Tagus and Sado estuaries. The current work shows that TBT pollution is undoubtedly a matter of concern not only for the above estuaries where harbours are implanted but also for the adjacent continental shelves, regardless the massive dilution of contaminants that may occur in these deeper areas.

Environmental levels, toxicity and human exposure to tributyltin (TBT)-contaminated marine environment. a review. b_antizar@hotmail.com

Tributyltin (TBT) is a toxic chemical used for various industrial purposes such as slime control in paper mills, disinfection of circulating industrial cooling waters, antifouling agents, and the preservation of wood. Due to its widespread use as an antifouling agent in boat paints, TBT is a common contaminant of marine and freshwater ecosystems exceeding acute and chronic toxicity levels. TBT is the most significant pesticide in marine and freshwaters in Europe and consequently its environmental level, fate, toxicity and human exposure are of current concern. Thus, the European Union has decided to specifically include TBT compounds in its list of priority compounds in water in order to control its fate in natural systems, due to their toxic, persistent, bioaccumulative and endocrine disruptive characteristics. Additionally, the International Maritime Organization has called for a global treaty that bans the application of TBT-based paints starting 1 of January 2003, and total prohibition by 1 of January 2008. This paper reviews the state of the science regarding TBT, with special attention paid to the environmental levels, toxicity, and human exposure. TBT compounds have been detected in a number of environmental samples. In humans, organotin compounds have been detected in blood and in the liver. As for other persistent organic pollutants, dietary intake is most probably the main route of exposure to TBT compounds for the general population. However, data concerning TBT levels in foodstuffs are scarce. It is concluded that investigations on experimental toxicity, dietary intake, potential human health effects and development of new sustainable technologies to remove TBT compounds are clearly necessary.

Stramonita haemastoma as a bioindicator for organotin contamination in coastal environments

Stramonita haemastoma was investigated as a suitable bioindicator of TBT and TPhT contamination in the tropical Atlantic Ocean by: 1. Imposex induction in healthy females after inoculation with TBT and TPhT in the laboratory; and 2. Determining incidence of imposex in S. haemastoma collected from areas with various levels of tributyltin (TBT) and triphenyltin (TPhT) and determining the concentrations of these chemical in its tissues and that of its prey, the mussell Perna pernas. Imposex intensities and organotin concentrations in tissues showed good correlation, indicating S. haemastoma as a reliable bioindicator of TBT and TPhT contamination in coastal waters. Body burden threshold of TBT and TPhT for imposex induction was estimated to be 10-20 ng g(-1).

Triphenyltin alters androgen metabolism in the sea urchin Paracentrotus lividus

Androgen metabolism (androstenedione and testosterone) has been assessed in the digestive tube and gonads of the echinoderm Paracentrotus lividus exposed to different concentrations of the biocide triphenyltin (TPT) in a semi-static water regime for 4 weeks. Key enzymatic activities involved in both synthesis and metabolism of androgens, namely 17beta-hydroxysteroid dehydrogenases (17beta-HSDs), 3beta-HSDs, 5alpha-reductases, P450-aromatase, palmitoyl-CoA:testosterone acyltransferases (ATAT) and testosterone sulfotransferases (SULT), were investigated in digestive tube and/or gonads of control and TPT-exposed specimens in an attempt to see whether androgen metabolism was altered by exposure. In agreement with previous data for vertebrates, exposure to TPT led to a concentration dependent decrease of P450-aromatase that was statistically significant at the highest TPT concentration tested (225ng/L). Additionally, increased metabolism of testosterone to form dihydrotestosterone (DHT) and 5alpha-androstane-3beta,17beta-diol was observed, suggesting increased 5alpha-reductase activity in the gonads of TPT-exposed individuals. Interestingly, exposure to TPT induced testosterone conjugating activities in organisms exposed to medium (SULT) and high (ATAT and SULT) TPT concentrations. Despite the changes of androgen metabolizing enzymes, testosterone levels in gonads remained rather stable. In contrast, an increase in testosterone and a concomitant decrease in estradiol were observed in the coelomic fluid of TPT-exposed organisms. Overall, the data indicate the ability of TPT to modulate androgen metabolism and circulating steroid levels in P. lividus and suggest the existence of regulatory mechanisms to maintain stable endogenous levels of testosterone in gonads. This study also contributes to a better knowledge of echinoderm endocrinology.

Accumulation of organotin compounds and mercury in harbour porpoises (Phocoena phocoena) from the Danish waters and West Greenland

The concentrations of butyltin (summation operatorBT=TBT+DBT+MBT) and mercury (Hg) were determined in the liver of 35 harbour porpoises (Phocoena phocoena), which were found dead along the coastlines or caught as by-catch in the Danish North Sea and the Inner Danish waters. In addition, three harbour porpoises hunted in West Greenland were analysed. High levels of butyltin and mercury, within the range of 68-4605 mg BT/kg ww and 0.22-92 mg Hg/kg ww, were found in the liver of the Danish harbour porpoises and both substances tend to accumulate with age. The levels in the harbour porpoise from West Greenland were 2.0-18 mg BT/kg ww and 6.3-6.9 mg Hg/kg ww, respectively. The concentrations of butyltin and mercury were both found to be higher in stranded than in by-caught harbour porpoises but only the butyltin concentration was significantly higher in stranded porpoises in the age group 1-5 years. These substances are suspected of inducing adverse effects on immune and endocrine systems in mammals and they may thereby pose a threat to the animals. This study suggests that organotin compounds are also important, when assessing the risks of contaminants on the health and viability of harbour porpoises in Danish waters.