Environmental Toxicology and Chemistry
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17α‐Ethinylestradiol alters reproductive behaviors, circulating hormones, and sexual morphology in male fathead minnows (<i>Pimephales promelas)</i> Abstract Ecologically relevant indicators of endocrine disruption in fish must be linked with measures of reproductive success. The ability of male fathead minnows (Pimephales promelas ) to compete for, maintain, and defend a spawning substrateis paramount to reproductive success. The present study quantified alterations in male fathead minnow reproductive behaviors after exposure to environmentally relevant concentrations (0, 10, 20, or 40 ng/L) of 17α‐ethinylestradiol (EE2 ) for 21 d. A video‐based behavioral quantification system examined changes in male‐male competitive behaviors (chasing and head‐butting) and ability of males to maintain spawning substrates (nibbling and scrubbing). Behaviors analyzed included time under the spawning substrate, frequency of substrate cleaning, and conspecific aggression. Plasma hormone levels (11‐ketotestosterone [11‐KT], testosterone, and estradiol [E2 ]), vitellogenin (VTG), secondary male characteristics (tubercle count and dorsal nape pad rank), gonadosomatic index (GSI), and gonad histology also were evaluated. Exposure to 40 ng/L of EE2 decreased the ability of exposed males to compete with control males for spawning substrates (p = 0.09). Furthermore, exposed males displayed reduced frequency of substrate cleaning activities as well as chasing male competitors (p ≤ 0.05). 11‐Ketotestosterone, testosterone, and E2 were lower, and VTG was notably higher, in EE2 ‐exposed males compared with control males (p ≤ 0.03). 17α‐Ethinylestradiol exposure in males also was associated with reductions in tubercles; lower GSI, gonadal maturity ranks, and number of resorbed tubercles; and presence of an ovipositor (p ≤ 0.001). These data reveal alterations in male reproductive behavior that coincide with decreased hormone levels and secondary sex characteristics. Behavioral endpoints to discern potential ecological consequences in fish exposed to low concentrations of endocrine‐disrupting chemicals may provide sensitive and functional indices of effect.
Environmental Toxicology and Chemistry - Tập 28 Số 5 - Trang 953-961 - 2009
Concentration dependence of biotransformation in fish liver S9: Optimizing substrate concentrations to estimate hepatic clearance for bioaccumulation assessment Abstract In vitro bioassays to estimate biotransformation rate constants of contaminants in fish are currently being investigated to improve bioaccumulation assessments of hydrophobic contaminants. The present study investigates the relationship between chemical substrate concentration and in vitro biotransformation rate of 4 environmental contaminants (9‐methylanthracene, pyrene, chrysene, and benzo[a ]pyrene) in rainbow trout (Oncorhynchus mykiss ) liver S9 fractions and methods to determine maximum first‐order biotransformation rate constants. Substrate depletion experiments using a series of initial substrate concentrations showed that in vitro biotransformation rates exhibit strong concentration dependence, consistent with a Michaelis–Menten kinetic model. The results indicate that depletion rate constants measured at initial substrate concentrations of 1 μM (a current convention) could underestimate the in vitro biotransformation potential and may cause bioconcentration factors to be overestimated if in vitro biotransformation rates are used to assess bioconcentration factors in fish. Depletion rate constants measured using thin‐film sorbent dosing experiments were not statistically different from the maximum depletion rate constants derived using a series of solvent delivery–based depletion experiments for 3 of the 4 test chemicals. Multiple solvent delivery–based depletion experiments at a range of initial concentrations are recommended for determining the concentration dependence of in vitro biotransformation rates in fish liver fractions, whereas a single sorbent phase dosing experiment may be able to provide reasonable approximations of maximum depletion rates of very hydrophobic substances. Environ Toxicol Chem 2015;34:2782–2790. © 2015 SETAC
Environmental Toxicology and Chemistry - Tập 34 Số 12 - Trang 2782-2790 - 2015
Wastewater treatment plants as a pathway for aquatic contamination by pharmaceuticals in the Ebro river basin (Northeast Spain) Abstract The occurrence of 28 pharmaceuticals of major human consumption in Spain, including analgesics and anti‐inflam‐matories, lipid regulators, psychiatric drugs, antibiotics, antihistamines, and β‐blockers, was assessed along the Ebro river basin, one of the biggest irrigated lands in that country. Target compounds were simultaneously analyzed by off‐line solid‐phase extraction, followed by liquid chromatography‐tandem mass spectrometry. The loads of detected pharmaceuticals and their removal rates were studied in seven wastewater treatment plants (WWTPs) located in the main cities along the basin. Total loads ranged from 2 to 5 and from 0.5 to 1.5 g/d/1,000 inhabitants in influent and effluent wastewaters, respectively. High removal rates (60–90%) were achieved mainly for analgesics and anti‐inflammatories. The other groups showed lower rates, ranging from 20 to 60%, and in most cases, the antiepileptic carbamazepine, macrolide antibiotics, and trimethoprim were not eliminated at all. Finally, the contribution of WWTP effluents to the presence of pharmaceuticals in receiving river waters was surveyed. In receiving surface water, the most ubiquitous compounds were the analgesics and anti‐inflammatories ibuprofen, diclofenac, and naproxen; the lipid regulators bezafibrate and gemfibrozil; the antibiotics erythromycin, azithromycin, sulfamethoxazole, trimethoprim, and less frequently, ofloxacin; the antiepileptic carbamazepine; the antihistamine ranitidine; and the β‐blockers atenolol and sotalol. Although levels found in WWTP effluents ranged from low μg/L to high ng/L, pharmaceuticals in river waters occurred at levels at least one order of magnitude lower (low ng/L range) because of dilution effect. From the results obtained, it was proved that WWTP are hot spots of aquatic contamination concerning pharmaceuticals of human consumption.
Environmental Toxicology and Chemistry - Tập 26 Số 8 - Trang 1553-1562 - 2007
From macroplastic to microplastic: Degradation of high‐density polyethylene, polypropylene, and polystyrene in a salt marsh habitat Abstract As part of the degradation process, it is believed that most plastic debris becomes brittle over time, fragmenting into progressively smaller particles. The smallest of these particles, known as microplastics, have been receiving increased attention because of the hazards they present to wildlife. To understand the process of plastic degradation in an intertidal salt marsh habitat, strips (15.2 cm × 2.5 cm) of high‐density polyethylene, polypropylene, and extruded polystyrene were field‐deployed in June 2014 and monitored for biological succession, weight, surface area, ultraviolet (UV) transmittance, and fragmentation. Subsets of strips were collected after 4 wk, 8 wk, 16 wk, and 32 wk. After 4 wk, biofilm had developed on all 3 polymers with evidence of grazing periwinkles (Littoraria irrorata ). The accreting biofilm resulted in an increased weight of the polypropylene and polystyrene strips at 32 wk by 33.5% and 167.0%, respectively, with a concomitant decrease in UV transmittance by approximately 99%. Beginning at 8 wk, microplastic fragments and fibers were produced from strips of all 3 polymers, and scanning electron microscopy revealed surface erosion of the strips characterized by extensive cracking and pitting. The results suggest that the degradation of plastic debris proceeds relatively quickly in salt marshes and that surface delamination is the primary mechanism by which microplastic particles are produced in the early stages of degradation. Environ Toxicol Chem 2016;35:1632–1640. © 2016 SETAC
Environmental Toxicology and Chemistry - Tập 35 Số 7 - Trang 1632-1640 - 2016
Zinc oxide nanoparticles toxicity to <i>Daphnia magna</i>: size‐dependent effects and dissolution Abstract As the production of zinc oxide nanoparticles (ZnO‐NPs) and other metal oxides is exponentially increasing, it is important to investigate potential environmental and health impacts of such nanoparticles. Nanoparticles' properties (e.g., size, dissolution rate) may change in different water media, and their characterization is essential to derive conclusions about toxicity results. Therefore, an aquatic model organism, Daphnia magna , was used to investigate the effect of ZnO‐NPs with 2 different particle sizes (30 nm and 80–100 nm) and then compare these effects with ZnO microsized particles (>200 nm) and the ionic counterpart (in the form of ZnCl2 ) on immobilization, feeding inhibition, and reproduction endpoints. The 48‐h median lethal concentration (LC50) for immobilization ranged between 0.76 mg Zn L−1 for the ionic zinc and 1.32 mg Zn L−1 for ZnO‐NPs of 80 nm to 100 nm. For the chronic exposures, the reproduction output was impaired similarly among zinc exposures and possibly driven mainly by the zinc ionic form. The concentrations used showed a total dissolution after 48 h. On the other hand, feeding activity was more affected by the 30 nm ZnO‐NPs than by the ionic zinc, showing that the particulate form was also playing an important role in the feeding inhibition of D. magna . Dissolution and particle size in the daphnia test media were found to be essential to derive conclusions on toxicity. Therefore, they can possibly be considered critical for evaluating nanoparticles' toxicity and fate. Environ Toxicol Chem 2014;33:190–198. © 2013 SETAC
Environmental Toxicology and Chemistry - Tập 33 Số 1 - Trang 190-198 - 2014
Toxicity of sixty‐three metals and metalloids to <i>Hyalella azteca</i> at two levels of water hardness Abstract he toxicityofall atomically s able metals in the periodic table, excluding Na, Mg, K, and Ca, was measured in one‐week exposures using the freshwater amphipod Hyalella azteca in both Lake Ontario, Canada, and soft water (10% Lake Ontario). Metals were added as atomic absorption standards (63 metals), and also as anion salts for 10 metals. Lethal concentrations resulting in 50% mortality (LC50s) were obtained for 48 of the metals tested; the rest were not toxic at 1,000 μg/L. The most toxic metals on a molar basis were Cd, Ag, Pb, Hg, Cr (anion), and Tl, with nominal LC50s ranging from 5 to 58 nmol/L (1 to 58 nmol/L measured). These metals were followed by U, Co, Os, Se (anion), Pt, Lu, Cu, Ce, Zn, Pr, Ni, and Yb with nominal LC50s ranging from 225 to 1,500 nmol/L (88–1,300 nmol/L measured). Most metals were similarly or slightly more toxic in soft water, but Al, Cr, Ge, Pb, and U were > 17‐fold more toxic in soft water; Pd was less toxic in soft water. Atomic absorption (AA) standards of As and Se in acid had similar toxicity as anions, Sb was more toxic as the AA standard, and Cr and Mn were more toxic as anions. One‐week LC50s for H. azteca correlate strongly with three‐week LC50s and three‐week effect concentrations resulting in 50% reduction in reproduction (EC50s) in Daphnia magna .
Environmental Toxicology and Chemistry - Tập 24 Số 3 - Trang 641-652 - 2005
Manganese toxicity to tropical freshwater species in low hardness water Abstract Elevated manganese (Mn) is a common contaminant issue for mine water discharges, and previous studies have reported that its toxicity is ameliorated by H+ , Ca2+ , and Mg2+ ions. In the present study, the toxicity of Mn was assessed in a high risk scenario, that is, the slightly acidic, soft waters of Magela Creek, Kakadu National Park, Northern Territory, Australia. Toxicity estimates were derived for 6 tropical freshwater species (Chlorella sp., Lemna aequinoctialis , Amerianna cumingi , Moinodaphnia macleayi , Hydra viridissima , and Mogurnda mogurnda ). Low effect chronic inhibition concentration (IC10) and acute lethal concentration (LC05) values ranged between 140 μg L–1 and 80 000 μg L–1 , with 3 of the species tested (M. macleayi , A. cumingi , and H. viridissima ) being more sensitive to Mn than all but 1 species in the international literature (Hyalella azteca ). A loss of Mn was observed on the final day for 2 of the H. viridissima toxicity tests, which may be a result of the complex speciation of Mn and biological oxidation. International data from toxicity tests conducted in natural water with a similar physicochemistry to Magela Creek water were combined with the present study's data to increase the sample size to produce a more reliable species sensitivity distribution. A 99% protection guideline value of 73 μg L–1 (33−466 μg L–1 ) was derived; the low value of this guideline value reflects the higher toxicity of Mn in slightly acidic soft waters. Environ Toxicol Chem 2015;34:2856–2863. © 2015 Commonwealth of Australia. Published by Wiley Periodicals, Inc. on behalf of SETAC.
Environmental Toxicology and Chemistry - Tập 34 Số 12 - Trang 2856-2863 - 2015
A database of fish biotransformation rates for organic chemicals Abstract Biotransformation is a key process that can mitigate the bioaccumulation potential of organic substances and is an important parameter for exposure assessments. A recently published method for estimating whole‐body in vivo metabolic biotransformation rate constants (k M ) is applied to a database of measured laboratory bioconcentration factors and total elimination rate constants for fish. The method uses a kinetic mass balance model to estimate rates of chemical uptake and elimination when measured values are not reported. More than 5,400 measurements for more than 1,000 organic chemicals were critically reviewed to compile a database of 1,535 k M estimates for 702 organic chemicals. Biotransformation rates range over six orders of magnitude across a diverse domain of chemical classes and structures. Screening‐level uncertainty analyses provide guidance for the selection and interpretation of k M values. In general, variation in k M estimates from different routes of exposure (water vs diet) and between fish species is approximately equal to the calculation uncertainty in k M values. Examples are presented of structure–biotransformation relationships. Biotransformation rate estimates in the database are compared with estimates of biodegradation rates from existing quantitative structure–activity relationship models. Modest correlations are found, suggesting some consistency in biotransformation capabilities between fish and microorganisms. Additional analyses to further explore possible quantitative structure–biotransformation relationships for estimating k M from chemical structure are encouraged, and recommendations for improving the database are provided.
Environmental Toxicology and Chemistry - Tập 27 Số 11 - Trang 2263-2270 - 2008
A quantitative structure‐activity relationship for predicting metabolic biotransformation rates for organic chemicals in fish Abstract An evaluated database of whole body in vivo biotransformation rate estimates in fish was used to develop a model for predicting the primary biotransformation half‐lives of organic chemicals. The estimated biotransformation rates were converted to half‐lives and divided into a model development set (n = 421) and an external validation set (n = 211) to test the model. The model uses molecular substructures similar to those of other biodegradation models. The biotransformation half‐life predictions were calculated based on multiple linear regressions of development set data against counts of 57 molecular substructures, the octanol‐water partition coefficient, and molar mass. The coefficient of determination (r 2 ) for the development set was 0.82, the cross‐validation (leave‐one‐out coefficient of determination, q 2 ) was 0.75, and the mean absolute error (MAE) was 0.38 log units (factor of 2.4). Results for the external validation of the model using an independent test set were r 2 = 0.73 and MAE = 0.45 log units (factor of 2.8). For the development set, 68 and 95% of the predicted values were within a factor of 3 and a factor of 10 of the expected values, respectively. For the test (or validation) set, 63 and 90% of the predicted values were within a factor of 3 and a factor of 10 of the expected values, respectively. Reasons for discrepancies between model predictions and expected values are discussed and recommendations are made for improving the model. This model can predict biotransformation rate constants from chemical structure for screening level bioaccumulation hazard assessments, exposure and risk assessments, comparisons with other in vivo and in vitro estimates, and as a contribution to testing strategies that reduce animal usage.
Environmental Toxicology and Chemistry - Tập 28 Số 6 - Trang 1168-1177 - 2009
Estimating metabolic biotransformation rates in fish from laboratory data Abstract A method is proposed for estimating metabolic biotransformation rate constants for nonionic organic chemicals from measured laboratory bioconcentration and dietary bioaccumulation data in fish. Data have been selected based on a quality review to reduce uncertainty in the measured values. A kinetic mass balance model is used to estimate rates of chemical uptake and elimination. Biotransformation rate constants are essentially calculated as the difference between two quantities, a measured bio‐concentration factor or elimination rate constant, and a model‐derived bioconcentration factor or elimination rate constant estimated assuming no biotransformation. Model parameterization exploits key empirical data when they are available and assumes default values when study specific data are unavailable. Uncertainty analyses provide screening level assessments for confidence in the biotransformation rate constant estimates. The uncertainty analyses include the range for 95% of the predicted values and 95% confidence intervals for the calculated biotransformation values. Case studies are provided to illustrate the calculation and uncertainty methods. Biotransformation rate constants calculated by the proposed method are compared with other published estimates for 31 chemicals that range in octanol–water partition coefficients from approximately 101 to 108 and represent over four orders of magnitude in biotransformation potential. The comparison of previously published values with those calculated by the proposed method shows general agreement with 82% of the estimated values falling within a factor of three.
Environmental Toxicology and Chemistry - Tập 27 Số 2 - Trang 341-351 - 2008
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