Intersex and liver alterations induced by long-term sublethal exposure to 17α-ethinylestradiol in adult male Cnesterodon decemmaculatus (Pisces: Poeciliidae)

The aim of the present study was to assess the responses of the gonopodium morphology and the gonadal and liver histology of adult male Cnesterodon decemmaculatus to sublethal long-term exposure concentrations of 17α-ethinylestradiol (EE2). Two experiments were conducted exposing the fish to waterborne concentrations of EE2 ranging from 20 ng/L to 200 ng/L for 8 wk, 12 wk, and 16 wk. Intersex gonads were observed after 8 wk and 16 wk in fish exposed to 200 ng EE2/L and 100 ng EE2/L, respectively. Oocytes' development from testis germ cells and replacement of the efferent duct periodic acid-Schiff-positive secretion surrounding spermatozeugmata by parenchymal tissue and duct structure alterations were the major observed changes in the gonads. In contrast, no response was observed in the gonopodium morphology. Liver histology was also altered, showing increasing steatosis, single-cell necrosis to generalized necrosis, and disruption of acinar organization from 100 ng EE2/L to 200 ng EE2/L. In summary, the present results showed that although EE2 was not able to alter the morphology of a developed gonopodium, it was capable of inducing development of testicular oocytes in adult male C. decemmaculatus at environmentally relevant concentrations. Thus, externally normal but intersex C. decemmaculatus males would be expected in the wastewater-receiving streams that the species inhabits. According to the literature, the present study would be the first indicating estrogen-induced intersex in adult male poeciliid. Environ Toxicol Chem 2017;36:1738-1745. © 2016 SETAC.

Sub-lethal increases in salinity affect reproduction in fathead minnows

Salinization poses a threat to many inland aquatic ecosystems, especially in areas where natural processes are compounded by anthropogenic salinization. Though physiological survival can be a challenge for stenohaline freshwater fishes facing increasing salinity, it is important to note that essential and complex activities such as reproduction may be affected well below physiological tolerance limits. Here, we exposed fathead minnows (Pimephales promelas) to four levels of salinity in order to assess any impacts on several egg production and behavioral endpoints. We found significant reductions in total eggs produced, percent fertilization, number of spawning days, clutch size, total time males spent in the nest, and duration of nest care events. Our data demonstrate that salinization can have negative effects on critical reproductive endpoints.

Human pharmaceuticals in the aquatic environment: a review of recent toxicological studies and considerations for toxicity testing

Although an increasingly large amount of data exists on the acute and chronic aquatic toxicity of pharmaceuticals, numerous questions still remain. There remains a dearth of information pertaining to the chronic toxicity of bivalves, benthic invertebrates, fish, and endangered species, as well as study designs that examine mechanism-of-action (MOA)-based toxicity, in vitro and computational toxicity, and pharmaceutical mixtures. Studies examining acute toxicity are prolific in the published literature; therefore, we address many of the shortcomings in the literature by proposing "intelligent" well-designed aquatic toxicology studies that consider comparative pharmacokinetics and pharmacodynamics. For example, few studies on the chronic responses of aquatic species to residues of pharmaceuticals have been performed, and very few on variables that are plausibly linked to any therapeutic MOA. Unfortunately, even less is understood about the metabolism of pharmaceuticals in aquatic organisms. Therefore, it is clear that toxicity testing at each tier of an ecological risk assessment scheme would be strengthened for some pharmaceuticals by selecting model organisms and endpoints to address ecologically problematic MOAs. We specifically recommend that future studies employ AOP approaches (Ankley et al. 2010) that leverage mammalian pharmacology information, including data on side effects and contraindications. Use of conceptual AOP models for pharmaceuticals can enhance future studies in ways that assist in the development of more definitive ecological risk assessments, identify chemical classes of concern, and help protect ecosystems that are affected by WWTP effluent discharge.

The risks associated with wastewater reuse and xenobiotics in the agroecological environment

Treated wastewater reuse for irrigation, landscape and surface or groundwater replenishment purposes is being widely implemented. Although the reuse practice is accompanied by a number of benefits relating to the enhancement of water balances and soil nutrition by the nutrients existing in the treated effluents, a number of unanswered questions are still related to this practice. Besides the lack of knowledge in respect to possible elemental interactions that may influence the accumulation of heavy metals and other elements in the soil and the subsequent uptake by plants and crops, during the last several years, the technological progress in respect to analytical chromatographic methods has enabled the identification and quantitation of a number of organic xenobiotic compounds in treated wastewater. Therefore it is now known that the effluents' remaining organic matter most usually expressed as Chemical Oxygen Demand consists of a number of biorecalcitrant organic xenobiotic compounds including potential endocrine disrupting compounds (EDCs), pharmaceuticals, etc. It is also widely accepted that the currently applied treatment processes for urban wastewater abatement fail to completely remove such contaminants and this lead to their subsequent release in the terrestrial and aquatic environment through disposal and reuse applications. The number of studies focusing on the analysis and the toxicological assessment of such compounds in the environment is constantly increasing the aim being to bridge the various knowledge gaps associated with these issues. The existing knowledge in respect to the relevant existing legislation framework, the types of elements and chemicals of concern, the uptake of xenobiotic pollutants and also that of other neglected chemical elements along with their potential environmental interactions constitute the focus of the present review paper. The review addresses the problems that might be related to the repeated treated wastewater release in the environment for reuse applications in respect to the wastewater residual load in heavy metals, accumulating in soil and plants and especially in their edible parts, in xenobiotic compounds, including EDCs, pharmaceuticals and personal care products, drugs' metabolites, illicit drugs, transformation products, and also genes resistant to antibiotics.

Highly active human pharmaceuticals in aquatic systems: A concept for their identification based on their mode of action

Widespread occurrence of traces of pharmaceuticals (ng/L to microg/L) has been reported in aquatic systems. However, their effects on the environment and their environmental risks remain elusive. Generally, the acute toxicity towards non-target organisms has been assessed in laboratory experiments, but chronic toxicity studies have been performed only rarely. The guideline issued by the European Medicines Agency in 2006 is aimed at estimating the potential environmental risks of human pharmaceuticals by a tiered approach. The predicted environmental concentration (PEC) of a compound is estimated in phase I, and pharmaceuticals having a PEC above or equal 10ng/L undergo phase II testing. Otherwise they are not expected to pose a risk to the environment. Because some highly active compounds (HC) such as 17-alpha-ethinylestradiol, equine estrogens, trenbolone and the progestin levonorgestrel display adverse effects at concentrations below 10ng/L the question arises, whether additional HC compounds exist, and how they can be identified for undergoing environmental risk assessment. We addressed this question by searching for HC in the literature, and by developing a concept for identification of HC. The suggested mode of action concept is based on (i) the mode of action of the pharmaceutical taking the available toxicological information into account, (ii) the degree of sequence homology between the human drug target and the potential target in aquatic organisms and (iii) the importance of pathways affected by the pharmaceutical. We evaluated the mode of action concept by comparison to existing approaches, the fish plasma model (Huggett et al., 2003) and a QSAR model, called VirtualTox Lab (www.biograf.ch). All concepts result in similar classifications of the selected pharmaceuticals. However, there are some differences not only in the model assumptions, but also in its results. Our study leads to the conclusion that the mode of action concept is most suitable for the identification of HC. A refinement can be achieved by complementing this concept by the QSAR model (VirtualTox Lab), whereas the fish plasma model seemed to be less suitable due to the necessity of environmental concentration above 10ng/L for the identification of a risk.

Changes in reproductive biomarkers in an endangered fish species (bonytail chub, Gila elegans) exposed to low levels of organic wastewater compounds in a controlled experiment

In arid regions of the southwestern United States, municipal wastewater treatment plants commonly discharge treated effluent directly into streams that would otherwise be dry most of the year. A better understanding is needed of how effluent-dependent waters (EDWs) differ from more natural aquatic ecosystems and the ecological effect of low levels of environmentally persistent organic wastewater compounds (OWCs) with distance from the pollutant source. In a controlled experiment, we found 26 compounds common to municipal effluent in treatment raceways all at concentrations <1.0 microg/L. Male bonytail chub (Gila elegans) in tanks containing municipal effluent had significantly lower levels of 11-ketotestosterone (p=0.021) yet higher levels of 17beta-estradiol (p=0.002) and vitellogenin (p=0.036) compared to control male fish. Female bonytail chub in treatment tanks had significantly lower concentrations of 17beta-estradiol than control females (p=0.001). The normally inverse relationship between primary male and female sex hormones, expected in un-impaired fish, was greatly decreased in treatment (r=0.00) versus control (r=-0.66) female fish. We found a similar, but not as significant, trend between treatment (r=-0.45) and control (r=-0.82) male fish. Measures of fish condition showed no significant differences between male or female fish housed in effluent or clean water. Inter-sex condition did not occur and testicular and ovarian cells appeared normal for the respective developmental stage and we observed no morphological alteration in fish. The population-level impacts of these findings are uncertain. Studies examining the long-term, generational and behavioral effects to aquatic organisms chronically exposed to low levels of OWC mixtures are needed.

The physiology and toxicology of salmonid eggs and larvae in relation to water quality criteria

The purpose of this review is to collate physiological knowledge on salmonid eggs and larvae in relation to water quality criteria. Salmonid genera reviewed include Coregonus, Thymallus, Salvelinus, Salmo, and Oncorhynchus spp. When physiological data for salmonids are lacking, the zebrafish and medaka models are included. The primary focus is on the underlying mechanisms involved in the hydro-mineral, thermal, and respiratory biology with an extended section on the xenobiotic toxicology of the early stages. Past and present data reveal that the eggs of salmonids are among the largest shed by any broadcast spawning teleost. Once ovulated, the physicochemical properties of the ovarian fluid provide temporary protection from external perturbations and maintain the eggs in good physiological condition until spawning. Following fertilisation and during early development the major structures protecting the embryo from poor water quality are the vitelline membrane, the enveloping layer and the chorion. The vitelline membrane is one of the least permeable membranes known, while the semi-permeable chorion provides both physical and chemical defense against metals, pathogens, and xenobiotic chemicals. In part these structures explain the lower sensitivity of the eggs to chemical imbalance compared to the larvae, however the lower metabolic rate and the chronology of gene expression and translational control suggest that developmental competence also plays a decisive role. In addition, maternal effect genes provide a defense potential until the mid-blastula transition. The transition between maternal effect genes and zygotic genes is a critical period for the embryo. The perivitelline fluids are an important trap for cations, but are also the major barrier to diffusion of gases and solutes. Acidic environmental pH interferes with acid-base and hydromineral balance but also increases the risk of aluminium and heavy metal intoxication. These risks are ameliorated somewhat by the presence of ambient humic acid. High temperatures during development may be teratogenic, cause sexual bias, or long-term effects on muscle cellularity. Xenobiotics cause inhibition of neural acetylcholine esterase and carboxylases and disrupt the normal signalling pathways of hormones by binding to relevant receptors and mimicking their actions. A complex suite of genes is activated in response to environmental or parentally transmitted xenobiotics. The primary defense mechanism in embryos involves resistance to uptake but later biotransformation via the aryl hydrocarbon receptor (AHR)-mediated activation of members of the cytochrome mixed-function mono-oxygenase superfamily (CYP1A, CYP2B, and CYP3A) and subsequent glucuronidation or glutathionation. Due to the number of duplicate or triplicate genes coding for intermediates in the signalling pathways, and cross-talk between nuclear orphan receptors and steroid hormone receptors, a large number of complications arise in response to xenobiotic intoxicaton. One such syndrome, known as blue-sac disease causes an anaphylactoid response in hatched larvae due to increased permeability in the vascular endothelium that coincides with AHR-mediated CYP induction. Early embryos also respond to such xenobiotic insults, but apparently have an immature translational control for expression of CYP proteins, which coincides with a lack of excretory organs necessary for the end-point of biotransformation. Other syndromes (M74 and Cayuga) are now associated with thiamine deficiency. Where possible guidelines for water quality criteria are suggested.