Analysis of environmental endocrine disrupting chemicals using the E-screen method and stir bar sorptive extraction in wastewater treatment plant effluents

Endocrine disrupting chemicals (EDCs) have become a major issue in the field of environmental science due to their ability to interfere with the endocrine system. Recent studies show that surface water is contaminated with EDCs, many released from wastewater treatment plants (WWTP). This pilot study used biological (E-screen assay) and chemical (stir bar sorptive extraction-GC-MS) analyses to quantify estrogenic activity in effluent water samples from a municipal WWTP and in water samples of the recipient river, upstream and downstream of the plant.The E-screen assay was performed on samples after solid phase extraction (SPE) to determine total estrogenic activity; the presence of estrogenic substances can be evaluated by measuring the 17-β-estradiol equivalency quantity (EEQ). Untreated samples were also assayed with an acute toxicity test (Vibrio fischeri) to study the correlation between toxicity and estrogenic disruption activity.Mean EEQs were 4.7 ng/L (± 2.7 ng/L) upstream and 4.4 ng/L (± 3.7 ng/L) downstream of the plant, and 11.1 ng/L (± 11.7 ng/L) in the effluent. In general the WWTP effluent had little impact on estrogenicity nor on the concentration of EDCs in the river water. The samples upstream and downstream of the plant were non-toxic or weakly toxic (0 < TU < 0.9) while the effluent was weakly toxic or toxic (0.4 < TU < 7.6). Toxicity and estrogenic activity were not correlated.At most sites, industrial mimics, such as the alkylphenols and phthalates, were present in higher concentrations than natural hormones. Although the concentrations of the detected xenoestrogens were generally higher than those of the steroids, they accounted for only a small fraction of the EEQ because of their low estrogenic potency. The EEQs resulting from the E-screen assay and those calculated from the results of chemical analyses using estradiol equivalency factors were comparable for all samples and closely correlated.     

Comparison of natural estrogen removal efficiency in the conventional activated sludge process and the oxidation ditch process

The presence of natural estrogens, 17beta-estradiol (E2), estrone (E1) and estriol (E3), as well as estrogenic activity in wastewater influents and secondary effluents were investigated in 20 full-scale wastewater treatment plants in Japan. In all of the influent samples, natural estrogens were detected at concentrations above the minimum limits of detection (0.5ng/L). The concentrations of natural estrogens detected in the effluent of oxidation ditch plants were generally lower than previously reported values. On the other hand, in the conventional activated sludge plants, increments of E1 during biological treatment were frequently observed although E2 and E3 were removed effectively in the process. The removal rates of natural estrogens or estrogenic activity show no observed statistical relationship with the solids retention time (SRT) and the hydraulic retention time (HRT). However, the plants with high SRT or HRT generally showed high and stable removal of both natural estrogens and estrogenic activity.     

Integration of GC-MSD and ER-Calux® assay into a single protocol for determining steroid estrogens in environmental samples

There are many published studies that use either chemical or biological methods to investigate steroid estrogens in the aquatic environment, but rarer are those that combine both. In this study, gas chromatography with mass selective detection (GC-MSD) and the ER-Calux^® estrogenicity assay were integrated into a single protocol for simultaneous determination of natural (estrone — E1, 17β-estradiol — E2, estriol — E3) and synthetic (17α-ethinylestradiol — EE2) steroid estrogens concentrations and the total estrogenic potential of environmental samples. For integration purposes, several solvents were investigated and the commonly used dimethyl sulphoxide (DMSO) in the ER-Calux^® assay was replaced by ethyl acetate, which is more compatible with gas chromatography and enables the same sample to be analysed by both GC-MSD and the ER-Calux^® assay. The integrated protocol was initially tested using a standard mixture of estrogens. The results for pure standards showed that the estrogenicity calculated on the basis of GC-MSD and the ER-Calux^® assay exhibited good correlation (r² = 0.96; α = 0.94). The result remained the same when spiked waste water extracts were tested (r² = 0.92, α = 1.02). When applied to real waste water influent and effluent samples the results proved (r² = 0.93; α = 0.99) the applicability of the protocol. The main advantages of this newly developed protocol are simple sample handling for both methods, and reduced material consumption and labour. In addition, it can be applied as either a complete or sequential analysis where the ER-Calux^® assay is used as a pre-screening method prior to the chemical analysis.     

Interaction of Galaxolide® with the human and trout estrogen receptor-α

Synthetic musks have been detected in sewage effluents, surface waters, and fish tissues where the polycyclic musk compound, HHCB (Galaxolide®) is the dominant compound in those matrices. In the present study, the Galaxolide® formulation was tested in the yeast estrogenicity screening (YES) assay, and also tested in in vitro and in vivo teleost systems to determine whether it interacts with the estrogen receptor as either an agonist or antagonist. In those tests, Galaxolide® did not act as an estrogen agonist, however there was strong evidence of antagonistic activity as Galaxolide® inhibited the estrogenic activity of 17β-estradiol (E2). In the YES assay based on a recombinant strain of yeast containing the human estrogen receptor (i.e. hERα), Galaxolide® inhibited the effects of E2 in a dose-dependent manner (IC50 = 1.63 × 10⁻⁵ M). In a luciferase reporter gene assay based on the rainbow trout estrogen receptor (i.e. rtER) transfected into a rainbow trout gonadal (RTG-2) cell line, the IC50 for the antagonistic effect of Galaxolide® was 2.79 × 10⁻⁹ M. In an in vivo assay based on modulation of vitellogenin in rainbow trout, Galaxolide® i.p. injected into trout at a dose of 3.64 mg/kg caused inhibition of E2-induced vitellogenin production. That dose is within the range of concentrations of Galaxolide® that have been detected in tissues of fish from contaminated locations.     

Ozonation and activated carbon treatment of sewage effluents: removal of endocrine activity and cytotoxicity

Concerns about endocrine disrupting compounds in sewage treatment plant (STP) effluents give rise to the implementation of advanced treatment steps for the elimination of trace organic contaminants. The present study investigated the effects of ozonation (O₃) and activated carbon treatment (AC) on endocrine activities [estrogenicity, anti-estrogenicity, androgenicity, anti-androgenicity, aryl-hydrocarbon receptor (AhR) agonistic activity] with yeast-based bioassays. To evaluate the removal of non-specific toxicity, a cytotoxicity assay using a rat cell line was applied. Wastewater (WW) was sampled at two STPs after conventional activated sludge treatment following the secondary clarifier (SC) and after subsequent advanced treatments: O₃, O₃ + sand filtration (O_3-SF), and AC. Conventional treatment reduced estrogenicity, androgenicity, and AhR agonistic activity by 78-99% compared to the untreated influent WW. Anti-androgenicity and anti-estrogenicity were not detectable in the influent but appeared in SC, possibly due to the more effective removal of respective agonists during conventional treatment. Endocrine activities after SC ranged from 2.0 to 2.8 ng/L estradiol equivalents (estrogenicity), from 4 to 22 μg/L 4-hydroxytamoxifen equivalents (anti-estrogenicity), from 1.9 to 2.0 ng/L testosterone equivalents (androgenicity), from 302 to 614 μg/L flutamide equivalents (anti-androgenicity), and from 387 to 741 ng/L β-naphthoflavone equivalents (AhR agonistic activity). In particular, estrogenicity and anti-androgenicity occurred in environmentally relevant concentrations. O₃ and AC further reduced endocrine activities effectively (estrogenicity: 77-99%, anti-androgenicity: 63-96%, AhR agonistic activity: 79-82%). The cytotoxicity assay exhibited a 32% removal of non-specific toxicity after O₃ compared to SC. O₃ and sand filtration reduced cytotoxic effects by 49%, indicating that sand filtration contributes to the removal of toxicants. AC was the most effective technology for cytotoxicity removal (61%). Sample evaporation reduced cytotoxic effects by 52 (AC) to 73% (O₃), demonstrating that volatile substances contribute considerably to toxic effects, particularly after O₃. These results confirm an effective removal or transformation of toxicants with receptor-mediated mode of action and non-specific toxicants during O₃ and AC. However, due to the limited extractability, polar ozonation by-products were neglected for toxicity analysis, and hence non-specific toxicity after O₃ is underestimated.     

Oxidative removal of aqueous steroid estrogens by manganese oxides

This study investigated the oxidative removal of steroid estrogens from water by synthetic manganese oxide (MnO₂) and the factors influencing the reactions. Using 1 × 10⁻⁵ M MnO₂ at pH 4, estrone (E1), 17β-estradiol (E2), estriol (E3) and 17α-ethinylestradiol (EE2), all at 4 × 10⁻⁶ M, were rapidly removed within 220 min, indicating the effectiveness of MnO₂ as an oxidizing agent towards estrogens. E2 removal increased with decreasing pH over the tested range of 4-8, due most likely to increased oxidizing power of MnO₂ and a cleaner reactive surface in acidic solutions. Coexisting metal ions of 0.01 M (Cu(II), Zn(II), Fe(III) and Mn(II)) and Mn(II) released from MnO₂ reduction competed with E2 for reactive sites leading to reduced E2 removal. Observed differential suppression on E2 removal may be related to different speciations of metals, as suggested by the MINTEQ calculations, and hence their different adsorptivities on MnO₂. By suppressing the metal effect, humic acid substantially enhanced E2 removal. This was attributed to complexation of humic acid with metal ions. With 0.01 M ZnCl₂ in solutions containing 1 mg l⁻¹ humic acid, the binding of humic acid for Zn(II) was determined at 251 mmol g⁻¹. An in vitro assay using human breast carcinoma MCF-7 cells indicated a near elimination of estrogenic activities without secondary risk of estrogen solutions treated with MnO₂. Synthetic MnO₂ is therefore a promising chemical agent under optimized conditions for estrogen removal from water. Metal chelators recalcitrant to MnO₂ oxidation may be properly used to further enhance the MnO₂ performance.     

Identification of estrogen-like effects and biologically active compounds in river water using bioassays and chemical analysis

The Nackdong River is the longest river in South Korea and passes through major cities that have several industrial complexes, including chemical, electric, and petrochemical complexes, and municipal characteristics such as apartment complexes. Along the river, the Gumi region has an electric industrial complex and an apartment complex that may be possible point sources of xenoestrogens such as phenolic compounds. To identify the causative chemicals for estrogenic activity in the river water of this region, bioassay-directed chemical analysis was performed. All samples from six sampling sites (an upstream point: S1; hot spot points: S2-1, S2-2, and S2-3; and downstream points: S3, and S4) showed estrogenic activity in the E-screen assay, with bio-EEQs (17β-E₂-equivalent quantities) ranging from 25.35-677.15 pg/L. Samples from S2-2, the sampling point downstream of the junction of stream water, and domestic and industrial wastewater, contained the highest estrogenic activity. Since the bio-EEQ of the organic acid fraction (F2) of the S2-2 sample had the highest activity (823.25 pg-EEQ/L) and F2 may contain phenolic compounds, GC-MS analyses for phenolic xenoestrogens were conducted with the organic acid fractions of the river water samples. Six estrogenic phenolic chemicals, 4-NP, BPA, 4-t-OP, 4-t-BP, 4-n-OP, and 4-n-HTP, were detected, with the highest concentrations (I-EEQ) found in S2-2 (231.80 pg/L). Among these phenolic chemicals, 4-NP was the most potent estrogen (bio-EEF; 8.12 × 10^− 5) and acted as a full agonist. Furthermore, 4-NP was present at levels (2.0 µg/L in S2-2) that can induce VTG induction in fish (>1 µg/L). In addition, we confirmed that river water (S2-2) significantly increased serum VTG levels in crucian carp (Carassius auratus) in a fish exposure experiment under laboratory conditions. Therefore, phenolic xenoestrogens, especially 4-NP, may be the main causative compounds responsible for the estrogenic effect on the Nackdong River.     

Evaluation of a photocatalytic reactor membrane pilot system for the removal of pharmaceuticals and endocrine disrupting compounds from water

A photocatalytic reactor membrane pilot system, employing UV/TiO₂ photocatalysis, was evaluated for its ability to remove thirty-two pharmaceuticals, endocrine disrupting compounds, and estrogenic activity from water. Concentrations of all compounds decreased following treatment, and removal followed pseudo-first-order kinetics as a function of the amount of treatment. Twenty-nine of the targeted compounds in addition to total estrogenic activity were greater than 70% removed while only three compounds were less than 50% removed following the highest level of treatment (4.24 kW h/m³). No estrogenically active transformation products were formed during treatment. Additionally, the unit was operated in photolytic mode (UV only) and photolytic plus H₂O₂ mode (UV/H₂O₂) to determine the relative amount of energy required. Based on the electrical energy per order (EEO), the unit achieved the greatest efficiency when operated in photolytic plus H₂O₂ mode for the conditions tested.     

Photoelectrocatalytic COD determination method using highly ordered TiO2 nanotube array

This work focuses on the experimental studies of a photoelectrocatalytic method for COD determination in a thin-cell reactor based on a highly effective TiO₂ nanotube array electrode. The effect of preparation parameters on the photoelectrocatalytic performance of TiO₂ nanotube array electrodes including the electrolyte, anodic potential, anodic time, solution pH, calcination temperature and time was examined. The TiO₂ nanotube array electrode prepared in preparation parameters at 1% HF electrolyte solution, anodic potential 20 V, anodic time 5 min, calcination temperature 450 °C with highly photoelectrocatalytic performance was chosen as the working electrode. When it is used in a thin-cell photoeletrocatalytic reactor for COD determination, it requires about 1-5 min to complete the oxidation of organics without further titration, much faster than the standard K₂Cr₂O₇ method (2-4 h). It consumes very limited harmless and inexpensive supporting electrolyte, free from secondary pollution. A wide dynamic working range of 0-850 mg/L can be achieved by this method, much wider than any other photoeletrocatalytic methods using TiO₂ nanoparticles or nanofilms in the reported literature. The effects of the water components were studied to propose the TiO₂ nanotube array method. Real sample analyses were also carried out and the COD value of real samples determined by this method agreed well with the standard dichromate method, and it shows good accuracy, stability and reproducibility.     

Understanding the gap between the estrogenicity of an effluent and its real impact into the wild

To study the reliability between in vitro and in vivo data collected downstream 2 sewage treatment plants (STP) as well as from bleached kraft mill industry (BKME), 5 rivers (3 impacted and 2 references) were investigated in the Walloon region (southern of Belgium). For the in vitro part of the work, water samples were collected to measure the estrogenicity of the ‘out’ effluent compared to reference sample point by MCF-7 assay. Results indicated significant estrogenicity of effluents from STP and BKME and a weak estrogenicity in reference sites. However, estradiol equivalents (EEQ) estimated into rivers were probably too low to impact wild population. Chemical analysis of 13 compounds of interest indicated that extraction procedure used in this study gave low recoveries of estrogen-like xenobiotics, leading to probably under-estimated MCF-7 responses. Surprisingly, a full scan mode has revealed an unexpected compound in the sample of BKME which was: 7-isopropyl-1,1,4a-trimethyl-1,2,3,4a,9,10,10a-octahydrophenanthrene, a product of pulp mill manufacture. In parallel to in vitro, in vivo assessment of estrogenic impact of effluent was followed on the gudgeon (Gobio gobio). Samples were achieved during 2 different periods of the reproductive cycle, resting period (RP) and pre-spawning period (pSP). Unspecific physiological parameters to estrogenic exposure (gonadosomatic index and systematic testis cell counting) displayed no significant differences related to endocrine disruption of the reproductive tract, only differences were correlated with the reproductive state of fish (RP versus pSP). Concerning the potent biomarker of estrogen exposure, vitellogenin (vtg), only basal induction was revealed but not related to estrogenic exposure. Nevertheless, vtg over-expression was found for male fish presenting a feminization of the reproductive tract captured downstream the STP station of Wégnez in the Vesdre River. Intersexuality, another indicator of the estrogenicity impact in fish, was observed in every site. Actually, ovotestis was systematically formed by protoplasmic oocyte observed in low percentage in every group analysed (impacted and references). Moreover, in fish captured in Wégnez, oocyte diameter was significantly higher compared to the other groups. In this study, only moderate to none impact in population of gudgeon was noticed. Moreover, in this case no discrepancy between in vitro and vivo was viewed although both approaches revealed gaps in monitoring effluent incidence into the environment. We should remain careful in the interpretation when only partial approaches are used in order to characterize impact in the aquatic milieu.     

Occurrence and removal of N-nitrosamines in wastewater treatment plants

The presence of nitrosamines in wastewater might pose a risk to water resources even in countries where chlorination or chloramination are hardly used for water disinfection. We studied the variation of concentrations and removal efficiencies of eight N-nitrosamines among 21 full-scale sewage treatment plants (STPs) in Switzerland and temporal variations at one of these plants. N-nitrosodimethylamine (NDMA) was the predominant compound in STP primary effluents with median concentrations in the range of 5-20 ng/L, but peak concentrations up to 1 μg/L. N-nitrosomorpholine (NMOR) was abundant in all plants at concentrations of 5-30 ng/L, other nitrosamines occurred at a lower number of plants at similar levels. From concentrations in urine samples and domestic wastewater we estimated that human excretion accounted for levels of <5 ng/L of NDMA and <1 ng/L of the other nitrosamines in municipal wastewater, additional domestic sources for <5 ng/L of NMOR. Levels above this domestic background are probably caused by industrial or commercial discharges, which results in highly variable concentrations in sewage. Aqueous removal efficiencies in activated sludge treatment were in general above 40% for NMOR and above 60% for the other nitrosamines, but could be lower if concentrations were below 8-15 ng/L in primary effluent. We hypothesize that substrate competition in the cometabolic degradation explains the occurrence of such threshold concentrations. An additional sand filtration step resulted in a further removal of nitrosamines from secondary effluents even at low concentrations. Concentrations released to surface waters were largely below 10 ng/L, suggesting a low impact on Swiss water resources and drinking water generation considering the generally high environmental dilution and possible degradation. However, local impacts in case a larger fraction of wastewater is present cannot be ruled out.     

Comparison of six different sewage treatment processes—Reduction of estrogenic substances and effects on gene expression in exposed male fish

Treated sewage effluents often contain a mixture of estrogenic compounds in low concentrations. The total combined activity of these, however, may be sufficiently high to affect the reproduction of aquatic vertebrates. The introduction of advanced treatment technologies has been suggested as a way to remove micro-contaminants, including estrogenic substances. In this study, one municipal influent was treated with six different processes in parallel on a semi-large scale in order to assess their potential to reduce substances that could contribute to estrogenic effects in male fish. The effluent from a conventional, activated sludge treatment line was compared to a similarly treated effluent with a final sand-filtering step. The addition of ozonation (15 g O₃/m³), a moving bed biofilm reactor (MBBR) or both in combination was also evaluated. There was also a separate treatment line that was based on a membrane bioreactor. A small battery of hepatic estrogen-responsive genes was measured in the exposed fish using quantitative PCR. Concentrations of steroid estrogens and estrogenic phenols in the effluents were measured by GC-ECNI-MS. The ozonated effluents were the only tested effluents for which all measured biological effects in exposed fish were removed. Chemical data suggested that the MBBR technology was equally effective in removing the analyzed estrogens; however, elevated expression of estrogen-responsive genes suggested that some estrogenic substances were still present in the effluent. The membrane bioreactor removed most of the measured estrogens and it reduced the induction of the estrogen-responsive genes. However, fish exposed to this effluent had significantly enlarged livers. Given that the same influent was treated in parallel with a broad set of technologies and that the chemical analyses were combined with an in vivo assessment of estrogenic responses, this study provides valuable input into the assessment of advanced treatment processes for removing estrogenic substances.     

Simultaneous abiotic reduction-biotic oxidation in a microbial-MnO2-catalyzed Fenton-like system

The possibility of simultaneous activity of superoxide-mediated transformations and heterotrophic aerobic bacterial metabolism was investigated in catalyzed H₂O₂ propagations (CHP; i.e., modified Fenton's reagent) systems containing Escherichia coli. Two probe compounds were used: glucose for the detection of heterotrophic metabolism of E. coli, and tetrachloromethane (CCl₄) for the detection of superoxide generated in a MnO₂-catalyzed CHP system. In the MnO₂-catalyzed CHP system without bacteria, only CCl₄ loss was observed; in contrast, only glucose degradation occurred E. coli systems without CHP reagents. In combined microbial-MnO₂ CHP reactions, loss of both probes was observed. Glucose assimilation decreased and CCl₄ transformation increased as a function of H₂O₂ concentration. Central composite rotatable experimental designs were used to determine that the conditions providing maximum simultaneous abiotic-biotic reactions were a biomass level of 10⁹ CFU/mL, 0.5 mM H₂O₂, and 0.5 g MnO₂. These results demonstrate that bacterial metabolism can occur in the presence of superoxide-mediated transformations. Such coexisting reactions may occur when H₂O₂ is injected into MnO₂-rich regions of the subsurface as a microbial oxygen source or for in situ oxidation; however, process control of such coexisting transformations may be difficult to achieve in the subsurface due to heterogeneity. Alternatively, hybrid abiotic reduction-biotic oxidation systems could be used for the treatment of industrial effluents or dilute solvent wastes that contain traces of highly halogenated compounds.     

An assessment of estrogenic organic contaminants in Canadian wastewaters

A suite of 30 primarily estrogenic organic wastewater contaminants was measured in several influent/effluent wastewater samples from four municipal wastewater treatment plants and effluents from one bleached kraft pulp mill (BKME) using an ultra-trace analytical method based on gas chromatography-high resolution mass spectroscopy (GC-HRMS). In vitro recombinant yeast assay detection of the estrogenic equivalent (EEq) on whole and solid phase extracted (SPE) and fractionated wastewater was also performed. 19-norethindrone was the most frequently detected and abundant (26-224 ng/L) of all the synthetic estrogens/progesterones in the influent samples. 17alpha-ethinylestradiol was the more frequently detected synthetic estrogen/progesterone in the effluents occurring at or below 5 ng/L with some sporadic occurrences of up to 178 ng/L. The greatest levels of steroidal estrogens in municipal effluents were E1>E2>E3 which were all <20 ng/L. Nonylphenol and di(2-ethylhexyl) phthalate were found to be the highest non-steroidal synthetic compounds surveyed in both municipal influent and effluent samples, both occurring at 6-7 microg/L in municipal effluents. BKME contained relatively large amounts of the plant sterol stigmasterol (4 microg/L) but low amounts of fecal sterols, and steroidal estrogens (E2 only at 6 ng/L) when compared to the municipal effluents. In vitro EEq in the wastewater surveyed ranged from 9-106 ng E2/L and ranked from municipal influent>municipal effluent approximately BKME, with most of the estrogenicity fractionating in the 100% methanol SPE fraction followed by a secondary amount in the diethyl ether (for municipal) or methyl-tert butyl ether (for BKME) SPE fractions. Most correlations between chemical and in vitro estrogenic equivalency were weak (p>0.05 in most cases). Unexpected inverse correlations between in vitro estrogenic activity and concentrations of the estrogenic contaminant bisphenol A were found which likely contributed to the weakness of these correlations. A modified toxicity identification and evaluation procedure was continued with the SPE extracts from the more potent 100% methanol SPE fractions of municipal effluent. High performance liquid chromatography band elution retention times, based on in vitro estrogen detection, indicated that steroidal estrogens such as E2 were responsible for most of the estrogenicity of the samples. Subsequent collection and GC-MS analysis of active bands did not confirm the presence of steroidal estrogens, but expanded the possibility of phthalate esters (i.e. dibutyl phthalate) and natural sterols (i.e. beta-sitosterol) contributing to the overall estrogenic load.     

Photoassisted reduction of metal ions and organic dye by titanium dioxide nanoparticles in aqueous solution under anoxic conditions

The photoassisted reduction of metal ions and organic dye by metal-deposited Degussa P25 TiO₂ nanoparticles was investigated. Copper and silver ions were selected as the target metal ions to modify the surface properties of TiO₂ and to enhance the photocatalytic activity of TiO₂ towards methylene blue (MB) degradation. X-ray powder diffraction (XRPD), X-ray photoelectron spectroscopy (XPS), and transmission electron microscopy (TEM) were used to characterize the crystallinity, chemical species and morphology of metal-deposited TiO₂, respectively. Results showed that the particle size of metal-deposited TiO₂ was larger than that of Degussa P25 TiO₂. Based on XRPD patterns and XPS spectra, it was observed that the addition of formate promoted the photoreduction of metal ion by lowering its oxidation number, and subsequently enhancing the photodegradation efficiency and rate of MB. The pseudo-first-order rate constant (k_obs) for MB photodegradation by Degussa P25 TiO₂ was 3.94 × 10^− 2 min^− 1 and increased by 1.4-1.7 times in k_obs with metal-deposited TiO₂ for MB photodegradation compared to simple Degussa P25 TiO₂. The increase in mass loading of metal ions significantly enhanced the photodegradation efficiency of MB; the k_obs for MB degradation increased from 3.94 × 10^− 2 min^− 1 in the absence of metal ion to 4.64-7.28 × 10^− 2 min^− 1 for Ag/TiO₂ and to 5.14-7.61 × 10^− 2 min^− 1 for Cu/TiO₂. In addition, the electrons generated from TiO₂ can effectively reduce metal ions and MB simultaneously under anoxic conditions. However, metal ions and organic dye would compete for electrons from the illuminated TiO₂.     

Short-term exposure to the environmentally relevant estrogenic mycotoxin zearalenone impairs reproduction in fish

Zearalenone (ZON) is one of the worldwide most common mycotoxins and exhibits estrogenic activity in the range of natural steroid estrogens such as 17β-estradiol (E2). The occurrence of ZON has been reported in drainage water, soil, wastewater effluents and rivers, but its ecotoxicological effects on fish have hardly been investigated.In this study the estrogenic potency of the ZON was compared to E2 in a recombinant yeast estrogen screen (rYES) and the effects of waterborne ZON exposure on reproduction, physiology and morphology of zebrafish (Danio rerio) were investigated in a 42-day reproduction experiment. E2 as well as ZON evoked a sigmoid concentration-response curve in the rYES with a mean EC₅₀ of 2 and 500 μg/L, respectively, resulting in an E2:ZON EC₅₀ ratio of 1:250. Exposure to ZON for 21 days reduced relative spawning frequency at 1000 and 3200 ng/L to 38.9 and 37.6%, respectively, and relative fecundity at 100, 320, 1000 and 3200 ng/L to 74.2, 41.7, 43.8 and 16.7%, respectively, in relation to the 21-day pre-exposure period. A 4.4 and 8.1 fold induction of plasma vitellogenin (VTG) was observed in male zebrafish at 1000 and 3200 ng/L ZON, respectively. Exposure to ZON did not affect fertility, hatch, embryo survival and gonad morphology of zebrafish.The results of this study demonstrate that although ZON possesses a moderate estrogenic potency in vitro, it exhibits a comparably strong effect on induction of VTG and reproduction in vivo. This indicates that ZON might contribute to the overall estrogenic activity in the environment and could therefore pose a risk for wild fish in their natural habitat.     

A rigorous small area modelling-study for the helicobacter pylori epidemiology

This paper presents an investigation into spatial risk differences over small distances for the Helicobacter pylori infection in the city of Leipzig, Germany and two rural districts. A model, using Bayesian inference, was developed that adjusts the risk for individual-specific factors, and for spatial or individual over-dispersion, respectively. Additionally, the model takes into account conditional spatial autocorrelation. We found a significant positive association to the H. pylori infection risk for: “more than three children live in the household” (OR = 2.4, p = 0.001), “more persons live per sq.m than average” (OR = 1.4, p = 0.03), “home situated at main road” (OR = 1.4, p = 0.04) and “using well water” (OR = 2.3, p = 0.05). A protective effect was identified for “travelled to low prevalence region” (OR = 0.4, p < 0.0001) and “born in Germany” (OR = 0.2, p < 0.0001). Three administrative areas with significantly increased spatial risk were identified: one in the rural district and two in the city of Leipzig. The model explained 24.9% of the total deviance. Contrary to expectations, the largest part of deviance of the data was not explained by the identified significant risk factors, but by individual-specific heterogeneities. We conclude that further - so far not discussed - factors influence the risk and the spatial variation of the H.pylori infection. Furthermore, from the results we speculate about a possible impact of long-time air pollution and surface water.     

Development of a TiO2 modified optical fiber electrode and its incorporation into a photoelectrochemical reactor for wastewater treatment

Electrochemical advanced oxidation processes (EAOPs) are used to chemically burn non biodegradable complex organic compounds that are present in polluted effluents. A common approach involves the use of TiO₂ semiconductor substrates as either photocatalytic or photoelectrocatalytic materials in reactors that produce a powerful oxidant (hydroxyl radical) that reacts with pollutant species. In this context, the purpose of this work is to develop a new TiO₂ based photoanode using an optic fiber support. The novel arrangement of a TiO₂ layer positioned on top of a surface modified optical fiber substrate, allowed the construction of a photoelectrochemical reactor that works on the basis of an internally illuminated approach. In this way, a semi-conductive optical fiber modified surface was prepared using 30 μm thickness SnO₂:Sb films on which the photoactive TiO₂ layer was electrophoretically deposited. UV light transmission experiments were conducted to evaluate the transmittance along the optical fiber covered with SnO₂:Sb and TiO₂ showing that 43% of UV light reached the optical fiber tip. With different illumination configurations (external or internal), it was possible to get an increase in the amount of photo-generated H₂O₂ close to 50% as compared to different types of TiO₂ films. Finally, the electro-Fenton photoelectrocatalytic Oxidation process studied in this work was able to achieve total color removal of Azo orange II dye (15 mg L⁻¹) and a 57% removal of total organic carbon (TOC) within 60 min of degradation time.     

Genotoxicity of platinum in embryos of zebrafish (Danio rerio) and ramshorn snail (Marisa cornuarietis)

The metal platinum is inter alia used for industrial and medical purposes. Due to its application in automobile catalytic converters and as an anti-cancer drug, Pt enters the aquatic environment via road runoff and hospital sewage and raises concerns about its environmental impact and toxicity to organisms. Therefore, the genotoxicity of Pt at 0, 0.1, 1, 10, 50, 100 and 200 μg/l PtCl₂ was tested on two freshwater organisms, zebrafish (Danio rerio) and ramshorn snail (Marisa cornuarietis) using the single cell gel electrophoresis, also called comet assay. PtCl₂ did not show any genotoxicity for D. rerio at the tested concentrations, whereas significantly elevated DNA damage was observed in M. cornuarietis at 1 μg/l PtCl₂ and beyond. The results of the study suggest a high sensitivity of M. cornuarietis concerning the genotoxic impact of PtCl₂.