An integrated assessment of estrogenic contamination and feminization risk in fish in Taihu Lake, China

Occurrence of 17α-ethynylestradiol (EE2) in the environment and effect on exposed biota: a review

17α-ethynylestradiol (EE2) is a synthetic hormone, which is a derivative of the natural hormone, estradiol (E2). EE2 is an orally bio-active estrogen, and is one of the most commonly used medications for humans as well as livestock and aquaculture activity. EE2 has become a widespread problem in the environment due to its high resistance to the process of degradation and its tendency to (i) absorb organic matter, (ii) accumulate in sediment and (iii) concentrate in biota. Numerous studies have reported the ability of EE2 to alter sex determination, delay sexual maturity, and decrease the secondary sexual characteristics of exposed organisms even at a low concentration (ng/L) by mimicking its natural analogue, 17β-estradiol (E2). Thus, the aim of this review is to provide an overview of the science regarding EE2, the concentration levels in the environment (water, sediment and biota) and summarize the effects of this compound on exposed biota at various concentrations, stage life, sex, and species. The challenges in respect of EE2 include the extension of the limited database on the EE2 pollution profile in the environment, its fate and transport mechanism, as well as the exposure level of EE2 for better prediction and definition revision of EE2 toxicity end points, notably for the purpose of environmental risk assessment.

Environmental estrogens in a drinking water reservoir area in Shanghai: occurrence, colloidal contribution and risk assessment

The occurrence and multi-phase distribution of six environmental estrogen compounds were investigated in a drinking water reservoir area by analyzing estrogens in suspended particulate matter (SPM), filtrate (conventional dissolved phase, <1 μm), permeate (truly soluble phase, <1 kDa) and retentate (colloidal phase, 1 kDa to 1 μm). The estrogen concentrations at different sites occurred in the following order: animal feed operation (AFO) wastewater-affected streams>tributaries>main stream channel. Correlation analysis showed that organic carbon (OC) contents had significantly positive correlations with environmental estrogens in filtrate, SPM and colloidal phases, respectively, indicating the important role played by OC. Aquatic colloids, often neglected, showed a much higher sorption capability of environmental estrogens compared to SPM. Similar Kcoc values in three types of sampling sites showed that colloids could be transported from AFO wastewater to tributaries and further into the main river channel. Mass balance calculations showed that 14.5-68.4% of OP, 4.5-32.1% of BPA, 2.0-58.4% of E1, 8.36-72.0% of E2, 0-20.6% of EE2, 3.4-62.7% of E3 and 8.3-36.1% of total estrogens were associated with colloidal fractions, suggesting that the colloids could act as a significant sink for environmental estrogens. Risk assessment demonstrated that the occurrence of environmental estrogens might pose a risk to aquatic organisms in the study area.

Emission estimation and multimedia fate modeling of seven steroids at the river basin scale in China

Steroids are excreted from humans and animals and discharged with wastewaters into the environment, resulting in potential adverse effects on organisms. Based on the excretion rates from different groups of humans and animals, the emissions of seven steroids (estrone (E1), 17β-estradiol (E2), estriol (E3), testosterone (T), androsterone (A), progesterone (P), and cortisol (C)) were comprehensively estimated in 58 river basins of whole China, and their multimedia fate was simulated by using a level III fugacity multimedia model. The results showed that higher emission densities for the steroids were found in the river basins of east China than in west China. This distribution was found to be generally similar to the distribution of Gross Domestic Product (GDP) across China. E3, A, and P displayed higher emission densities than the other steroids in most of the river basins. The total excretion of steroids by humans and animals in China was estimated to be 3069 t/yr. The excretion of steroids from animals was two times larger than that from humans. After various treatments, the total emission of steroids was reduced to 2486 t/yr, of which more than 80% was discharged into the water compartment. The predicted concentrations in water were within an order of magnitude of the measured concentrations available in the literature. Owing to wastewater irrigation, more steroid mass loadings in agricultural soil were found in the basins of Haihe River and Huaihe River in comparison with the other river basins. To the best of our knowledge, this is the first report on the emissions and multimedia fate of seven steroids in the river basins of China.

Sensitivity of the vitellogenin assay to diagnose exposure of fathead minnows to 17α-ethynylestradiol

Vitellogenin is frequently used as a biomarker of exposure to environmental estrogens due to its specificity and sensitivity. Appropriate incorporation of this biomarker into environmental monitoring and assessment necessitates evaluation of its critical performance parameters. In this study, we characterize the sensitivity of both vitellogenin gene (vtg) mRNA transcripts in liver and protein (VTG) in plasma over a range of concentrations and exposure durations. Male fathead minnows were exposed to 17α-ethynylestradiol (EE2) in a flow-through system for 2, 4 and 7 days at multiple EE2 concentrations in order to provide information regarding the sensitivity of each of these biomarkers to diagnose exposure to this representative estrogen. Measurements of the expression of the vitellogenin gene and protein both reliably detected exposures to EE2 at concentrations of 5ng/l and higher at all time points. Vtg mRNA and plasma VTG appear to have similar sensitivities, though the lower variability in VTG in control fish may make it more sensitive to small changes in expression compared to vtg. For lower concentrations, sensitivity may be improved by increasing exposure duration. A sample size of ∼12 fish was sufficient in many cases to produce a statistically significant increase in vitellogenin. Larger sample sizes may provide more sensitivity at low concentrations, but detecting exposure to estrogens in the lower range of environmentally relevant concentrations may need larger sample sizes. These data will assist in designing experiments that have sufficient statistical power necessary to determine if fish have been exposed to estrogens.

The levels of PAHs and aryl hydrocarbon receptor effects in sediments of Taihu Lake, China

A total of 16 priority polycyclic aromatic hydrocarbons (PAHs) in sediment samples from Taihu Lake were analyzed by instruments, and sediment extracts were assayed for aryl hydrocarbon receptor (AhR)-mediated ethoxyresorufin-o-deethylase (EROD) induction using a rat hepatoma cell line (H4IIE). The cause-effect relationship between the observed EROD activity and chemical concentrations of PAHs was examined. Our results showed that sediment extracts could induce significant AhR effects, and the bioassay-derived 2,3,7,8-tetrachlorodibenzo-p-dioxin equivalents of raw extracts (TEQ(bio)s) ranged from 2.7 to 39.8 pg g(-1) dw. Chemical analysis showed that 16 PAHs were all detected in all samples, and their total concentrations (Σ16PAHs) ranged from 179.8 to 1,669.4 ng g(-1) dw. The abundance of sedimentary PAHs in the three regions (Meiliang Bay, Gonghu Bay, and Xukou Bay) showed a decreasing trend from the inflow region to the outflow region. Chemical analysis-derived TEQs (TEQ(cal)s) contributed by PAHs ranged from 1.6 to 20.7 pg g(-1) dw. The mean contribution rates (CRs) of PAHs to TEQ(bio)s were 48.9%. In Meiliang Bay, EROD effects of 60% samples were caused by PAHs whose CRs were more than 60%, while in most sampling sites of Gonghu Bay and Xukou Bay, the CRs of PAHs to TEQ(bio)s were basically below 40%. In addition, preliminary ecological risk assessment found that PAHs in sediments have very low ecological impact based on the chemical data of PAHs, while the sediments might pose an unacceptable risk to aquatic organisms and their predators based on the data of TEQ(bio). These findings showed that EROD effects of sediment extracts from Taihu Lake were also caused by other compounds, such as dioxins, polychlorinated biphenyls, etc., together.

Long-term exposure investigating the estrogenic potency of estriol in Japanese medaka (Oryzias latipes)

The growth, development, and ERα and Vtg-I gene expressions of Japanese ricefish (Oryzias latipes; medaka) exposed to different concentrations of estriol (E3), including one environmentally relevant concentration, during embryo-adult life stages were evaluated. At the early life stage, fertilized eggs were exposed to 5, 50, 500, 5000ng/L E3 for 15days, and the hatched fry were exposed continuously to the same concentrations for an additional 15days. Exposure to 500 and 5000ng/L E3 resulted in adverse effects on hatchability and time to hatching. At 5000ng/L, the gross abnormality rate was increased and the number of females that hatched was twice that of males. When the fish were exposed to 5-5000ng/L E3 for further 60days, the male hepatosomatic index (HSI) was increased at 5000ng/L. The female gonadosomatic index (GSI) was decreased at 500 and 5000ng/L E3, while the male GSI at 5000ng/L E3 was increased and sex reversal was also found at this concentration. Quantitative RT-PCR showed that the hepatic vitellogenin-I (Vtg-I) genes were up-regulated in females at 500 and 5000ng/L E3 and in males at all E3 concentrations, whereas E3 did not affect estrogen receptor α (ERα) mRNA transcription. These results showed that E3 at environmental concentration of 5ng/L has no adverse effects on growth and development of the Japanese medaka. However, in this study, if we only focused on Vtg gene change in males, E3 had strong estrogenic effects on male medaka under the conditions of these experiments.

Potential environmental implications of emerging organic contaminants in Taihu Lake, China: comparison of two ecotoxicological assessment approaches

In this study, the hazard quotient (HQ) and a novel enhanced integrated biomarker response (EIBR) were applied to indirectly/directly estimate the ecotoxicological risk of emerging organic contaminants in Taihu Lake. Nine out of sixteen target compounds were detected in most sampling points at comparable concentrations (1.58-206.95 ng/L). Simultaneously, changes in multi-biomarkers were measured in caged fish for 28 days. The 0HQ results preliminarily indicated that most water areas were at significant risk for adverse effects to aquatic organisms (HQ>10). The prioritisation was then ranked and 17α-ethinylestradiol, diethylstilbestrol and 17β-estradiol were regarded as the greatest hazards. The EIBR, covering multi-biomarkers and their weighting, was applied to field study, and Zhushan Bay was suggested as the most stressful place, followed by Meiliang Bay. The HQ showed significant positive linear correlation with the EIBR (r=0.848, P<0.001), suggesting mutual consistency between the two approaches based on laboratory and field study in ecotoxicological risk assessment.

Transgenic (cyp19a1b-GFP) zebrafish embryos as a tool for assessing combined effects of oestrogenic chemicals

Endocrine disrupting chemicals and especially oestrogen receptor (ER) agonists have been extensively studied over the years due to their potential effects on sexual development and reproduction in vertebrates, notably fish. As ER agonists can exist as complex mixtures in the aquatic environment, evaluating the impact of combined exposure on oestrogenic effects has become increasingly important. Use of predictive models such as concentration addition (CA) and independent action (IA) has allowed assessment of combined estrogenic effects of complex multi-compound mixtures of ER agonists in various fish in vitro and in vivo experimental models. The present work makes use of a transgenic zebrafish strain, tg(cyp19a1b-GFP), which expresses the green fluorescent protein (GFP) under the control of the cyp19a1b (brain aromatase or aromatase B) gene to determine the oestrogenic potency of ER agonists alone or in mixtures. In these studies, tg(cyp19a1b-GFP) zebrafish embryos were exposed for four days (from one to five days post fertilization) to five different oestrogenic chemicals; 17α-ethinylestradiol (EE2), 17β-estradiol (E2), estrone (E1), bisphenol A (BPA) and 4-tert-octylphenol (OP), and three mixtures of up to four of these compounds. The mixture of BPA, OP and E2 was also tested with primary cultures of rainbow trout hepatocytes by analysing the ER-mediated induction of the oestrogenic biomarker vitellogenin in order to compare the performance of the two methods for assessing oestrogenic effects of complex mixtures. The three tested mixtures were predominantly acting in an additive manner on the expression of GFP. Additivity was indicated by the overlap of the 95% confidence interval of the concentration response curves for the observed data with the CA and IA prediction models, and model deviation ratios within a factor of two for a majority of the mixture concentrations. However, minor deviations determined as more than additive effects for the mixture of EE2, E1 and E2 and less than additive effects for the mixture of BPA, OP, EE2 and E1 were observed at the higher mixture concentrations tested. The successful prediction of additivity by CA and IA in tg(cyp19a1b-GFP) zebrafish embryos and deviations at high mixture concentrations seemed to correspond well to results obtained in the rainbow trout hepatocyte assay. The present results clearly show the usefulness of combining predictive modelling and use of in vitro bioassays for rapid screening of oestrogenic effects of complex mixtures and environmental samples.

Interaction of 17β-estradiol and ketoconazole on endocrine function in goldfish (Carassius auratus)

An understanding of the effects of toxic mixtures of endocrine disrupting chemicals (EDCs) on aquatic organisms is challenging as these organisms are exposed to multiple classes of contaminants in their natural habitat. The aim of the present study was to evaluate the interactions of two classes of EDCs, 17β-estradiol (E2) and ketoconazole (KTC), on endocrine function in male goldfish (Carassius auratus), including vitellogenesis, metabolic capability and serum steroid synthesis. Changes in vitellogenin (VTG) concentration, liver 7-ethoxyresorufin-O-deethylase (EROD) activity and circulating serum E2 level were examined. The expression of related genes was also determined using quantitative real-time polymerase chain reaction. Exposure to E2 caused a significant increase in VTG concentrations which corresponded with the gene expression of VTG and estrogen receptor (ER) in males, which were further elevated after combined exposure to E2 and KTC, indicative of a synergetic relationship. Exposure to E2 also resulted in a distinct increase in serum steroid biosynthesis and associated cytochrome P450 (CYP) aromatase expression after 10 days. However, these changes were inhibited by the presence of KTC, which acted as a steroidogenic inhibitor in fish. Moreover, KTC significantly decreased liver EROD activity and increased the related gene expression of CYP1A. However, these KTC-mediated metabolic reactions in goldfish were up-regulated following exposure to KTC in combination with E2. These findings reveal complex interactions on endocrine functions in male goldfish when exposed to multiple contaminations and may provide a better understanding of the effects of toxic mixtures.