Chemical contaminants in water and sediment near fish nesting sites in the Potomac River basin: determining potential exposures to smallmouth bass (Micropterus dolomieu)

Pesticides in small volume plasma samples: Method development and application to smallmouth bass (Micropterus dolomieu) from the Chesapeake Bay watershed, USA

Nontarget organisms are exposed to pesticides following applications in agricultural and urban settings, potentially resulting in deleterious effects. Direct measurements of pesticides in biological tissues may aid in characterizing exposure, accumulation, and potential toxicity versus analyses in environmental media alone (e.g., water, soil, and air). Plasma represents a nonlethal sampling medium that can be used to assess recent exposures to contaminants. Herein, a method was developed to test the extraction of 210 pesticides and their transformation products in small volume plasma samples (100 μL). Plasma samples were protein precipitated with 0.5 % formic acid in acetonitrile added to the sample (ratio of 3.5:1). Pass-through solid phase extraction was used for sample matrix and lipid removal and samples were analyzed by liquid chromatography and gas chromatography with tandem mass spectrometry. Recoveries of 70.0-129.8 % were achieved for 182 pesticides and degradates across the low (25 ng mL-1), medium (100 ng mL-1), and high (250 ng mL-1) spike levels. Method detection levels ranged 0.4-13.0 ng mL-1. Following development, the method was applied to smallmouth bass (Micropterus dolomieu) plasma samples (n = 10) collected from adults in the Chesapeake Bay watershed. Individual plasma samples resulted in four to seven analytes detected with summed concentrations ranging 16.4-95.0 ng mL-1. Biological multiresidue pesticide methods help elucidate recent exposures of bioactive compounds to nontarget organisms.

Multi-omic responses of fish exposed to complex chemical mixtures in the Shenandoah River watershed

To evaluate relationships between different anthropogenic impacts, contaminant occurrence, and fish health, we conducted in situ fish exposures across the Shenandoah River watershed at five sites with different land use. Exposure water was analyzed for over 500 chemical constituents, and organismal, metabolomic, and transcriptomic endpoints were measured in fathead minnows. Adverse reproductive outcomes were observed in fish exposed in the upper watershed at both wastewater treatment plant (WWTP) effluent- and agriculture-impacted sites, including decreased gonadosomatic index and altered secondary sex characteristics. This was accompanied with increased mortality at the site most impacted by agricultural activities. Molecular biomarkers of estrogen exposure were unchanged and consistent with low or non-detectable concentrations of common estrogens, indicating that alternative mechanisms were involved in organismal adverse outcomes. Hepatic metabolomic and transcriptomic profiles were altered in a site-specific manner, consistent with variation in land use and contaminant profiles. Integrated biomarker response data were useful for evaluating mechanistic linkages between contaminants and adverse outcomes, suggesting that reproductive endocrine disruption, altered lipid processes, and immunosuppression may have been involved in these organismal impacts. This study demonstrated linkages between human-impact, contaminant occurrence, and exposure effects in the Shenandoah River watershed and showed increased risk of adverse outcomes in fathead minnows exposed to complex mixtures at sites impacted by municipal wastewater discharges and agricultural practices.

A multi-level assessment of biological effects associated with mercury concentrations in smallmouth bass, Micropterus dolomieu

Total mercury (THg) was measured in muscle (fillet) and liver tissue of adult smallmouth bass Micropterus dolomieu collected at multiple sites in the Potomac and Susquehanna River drainages within the Chesapeake Bay watershed. Smallmouth bass in these drainages have experienced episodic mortality events, a high prevalence of skin lesions and reproductive endocrine disruption (intersex or testicular oocytes and plasma vitellogenin in males). A multi-level assessment of general and reproductive health including indicators at the organismal, organ, cellular and molecular levels was conducted on adult smallmouth bass during the spring (prespawn) season. Concentrations of THg were correlated with increased visible abnormalities, increased macrophage aggregates and tissue parasite burdens. In male bass positive correlations of THg were observed with plasma vitellogenin and hepatic transcript abundance of estrogen receptor β1 and androgen receptor α, while there was a negative association with estrogen receptors α and β2 and androgen receptors β. In female bass there was a negative correlation between THg and plasma vitellogenin as well as hepatic transcript abundance of vitellogenin, choriogenin, estrogen receptor β2 and 17β hydroxysteroid dehydrogenase. Associations of THg concentrations with various biological indicators suggest mercury may be an important environmental stressor contributing to the observed adverse effects in smallmouth bass populations.

Methodology for Effect-Based Identification of Bioconcentratable Endocrine Disrupting Chemicals (EDCs) in Water: Establishment, Validation, and Application

Since the wide occurrence of endocrine disrupting chemicals (EDCs) in water is associated with various adverse effects in aquatic organisms, it is urgent to identify key bioconcentratable EDCs. Currently, bioconcentration is generally ignored during the identification of key EDCs. Thus, a methodology for effect-based identification of bioconcentratable EDCs was established in Microcosm, validated in the field, and applied to typical surface water in Taihu Lake. In Microcosm, an inverted U-shaped relationship between logBCFs and logKows was observed for typical EDCs, with medium hydrophobic EDCs (3 ≤ logKow ≤ 7) exhibiting the greatest bioconcentration potentials. On this basis, enrichment methods for bioconcentratable EDCs were established using POM and LDPE, which better fitted the bioconcentration characteristics and enabled the enrichment of 71 ± 8% and 69 ± 6% bioconcentratable compounds. The enrichment methods were validated in the field, where LDPE exhibited a more significant correlation with the bioconcentration characteristics than POM, with mean correlation coefficients of 0.36 and 0.15, respectively, which was selected for further application. By application of the new methodology in Taihu Lake, 7 EDCs were prioritized from 79 identified EDCs as key bioconcentratable EDCs on consideration of their great abundance, bioconcentration potentials, and anti-androgenic potencies. The established methodology could support the evaluation and identification of bioconcentratable contaminants.

Prioritizing Pesticides of Potential Concern and Identifying Potential Mixture Effects in Great Lakes Tributaries Using Passive Samplers

To help meet the objectives of the Great Lakes Restoration Initiative with regard to increasing knowledge about toxic substances, 223 pesticides and pesticide transformation products were monitored in 15 Great Lakes tributaries using polar organic chemical integrative samplers. A screening-level assessment of their potential for biological effects was conducted by computing toxicity quotients (TQs) for chemicals with available US Environmental Protection Agency (USEPA) Aquatic Life Benchmark values. In addition, exposure activity ratios (EAR) were calculated using information from the USEPA ToxCast database. Between 16 and 81 chemicals were detected per site, with 97 unique compounds detected overall, for which 64 could be assessed using TQs or EARs. Ten chemicals exceeded TQ or EAR levels of concern at two or more sites. Chemicals exceeding thresholds included seven herbicides (2,4-dichlorophenoxyacetic acid, diuron, metolachlor, acetochlor, atrazine, simazine, and sulfentrazone), a transformation product (deisopropylatrazine), and two insecticides (fipronil and imidacloprid). Watersheds draining agricultural and urban areas had more detections and higher concentrations of pesticides compared with other land uses. Chemical mixtures analysis for ToxCast assays associated with common modes of action defined by gene targets and adverse outcome pathways (AOP) indicated potential activity on biological pathways related to a range of cellular processes, including xenobiotic metabolism, extracellular signaling, endocrine function, and protection against oxidative stress. Use of gene ontology databases and the AOP knowledgebase within the R-package ToxMixtures highlighted the utility of ToxCast data for identifying and evaluating potential biological effects and adverse outcomes of chemicals and mixtures. Results have provided a list of high-priority chemicals for future monitoring and potential biological effects warranting further evaluation in laboratory and field environments. Environ Toxicol Chem 2023;42:340-366. Published 2022. This article is a U.S. Government work and is in the public domain in the USA. Environmental Toxicology and Chemistry published by Wiley Periodicals LLC on behalf of SETAC.

Estrogenic activity response to best management practice implementation in agricultural watersheds in the Chesapeake Bay watershed

Best management practices (BMPs) have been predominantly used throughout the Chesapeake Bay watershed (CBW) to reduce nutrients and sediments entering streams, rivers, and the bay. These practices have been successful in reducing loads entering the estuary and have shown the potential to reduce other contaminants (pesticides, hormonally active compounds, pathogens) in localized studies and modeled load estimates. However, further understanding of relationships between BMPs and non-nutrient contaminant reductions at regional scales using sampled data would be beneficial. Total estrogenic activity was measured in surface water samples collected over a decade (2008-2018) in 211 undeveloped NHDPlus V2.1 watersheds within the CBW. Bayesian hierarchical modeling between total estrogenic activity and landscape predictors including landcover, runoff, BMP intensity, and a BMP*agriculture intensity interaction term indicates a 96% posterior probability that BMP intensity on agricultural land is reducing total estrogenic activity. Additionally, watersheds with high agriculture and low BMPs had a 49% posterior probability of exceeding an effects-based threshold in aquatic organisms of 1 ng/L but only a 1% posterior probability of exceeding this threshold in high-agriculture, high-BMP watersheds.

Declines in Reproductive Condition of Male Largemouth Bass (Micropterus salmoides) Following Seasonal Exposure to Estrogenic Endocrine-Disrupting Compounds

Reproductive abnormalities, that could lead to possible effects at the population level, have been observed in wild fish throughout the United States, with high prevalence in largemouth bass (LMB; Micropterus salmoides) and smallmouth bass (Micropterus dolomieu). Estrone (E1) and atrazine (ATR) are common environmental contaminants often associated with agricultural land use. 17alpha-ethinylestradiol (EE2) is a contaminant associated with wastewater treatment effluent, and a representative, well-studied estrogen commonly used for fish toxicity testing. Our objective was to assess whether early gonad recrudescence in adult fish was a period of sensitivity for alterations in reproductive condition and function. Adult male LMB were exposed from post-spawning to early gonad recrudescence to either a mixture of E1 (47.9 ng/L) + ATR (5.4 µg/L), or EE2 (2.4 ng/L) in outdoor experimental ponds. Gonad samples were collected from fish just prior to the start of exposure (July), at the end of the exposure period (December), the following spring just prior to spawning (April), and post spawning (May). Gonadosomatic index (GSI) was significantly reduced in E1 + ATR-exposed and EE2-exposed males compared to control at every post-exposure time point. Reduced sperm count and sperm motility were observed in the mixture treatment (E1 + ATR) compared to the control. Sperm motility was also reduced in the EE2 treatment. These data together indicate that estrogenic endocrine-disrupting compounds can lessen the reproductive condition of adult male LMB, and that effects of exposure during early gonad recrudescence can persist at least through the subsequent spawning cycle.

A case study: temporal trends of environmental stressors and reproductive health of smallmouth bass (Micropterus dolomieu) from a site in the Potomac River Watershed, Maryland, USA

Decades of poor reproductive success and young-of-the-year survival, combined with adult mortality events, have led to a decline in the smallmouth bass (SMB; Micropterus dolomieu) population in sections of the Potomac River. Previous studies have identified numerous biologic and environmental stressors associated with negative effects on SMB health. To better understand the impact of these stressors, this study was conducted at the confluence of Antietam Creek and the Potomac River from 2013 to 2019 to identify temporal changes associated with SMB reproductive health. Surface water samples were collected and analyzed for over 300 organic contaminants, including pesticides, phytoestrogens, pharmaceuticals, hormones and total estrogenicity (E2Eq). Adult SMB were collected and sampled for multiple endpoints, including gene transcripts associated with reproduction (molecular), histopathology (cellular), and organosomatic indices (tissue). In males, biomarkers of estrogenic endocrine disruption, including testicular oocytes (TO) and plasma vitellogenin (Vtg) were assessed. Numerous agriculture-related contaminants or land use patterns were associated with gene transcript abundance in both male and female SMB. Positive associations between pesticides in the immediate catchment with TO severity and E2Eq with plasma Vtg in males were identified. In males, the prevalence of TO and detectable levels of plasma Vtg, liver vitellogenin transcripts (vtg) and testis vtg were high throughout the study. Peaks of complex mixtures of numerous contaminants occurred during the spring/early summer when spawning and early development occurs and to a lesser extent in fall/winter during recrudescence. Management practices to reduce exposure during these critical and sensitive periods may enhance reproductive health of these economically important sportfishes.

Surface Water Processes Influencing Alterations in Pharmaceutical Chemical Composition following Wastewater Discharge into a Freshwater Estuary

The tidal freshwater Potomac River (TFPR) in the metropolitan Washington, DC region receives wastewater discharge from eight major wastewater treatment plants with the potential to impact water quality. A total of 85 pharmaceutical chemicals and personal care products (PPCPs) were analyzed in surface water and sediments using solid-phase extraction and QuEChERS, respectively, in conjunction with liquid-chromatography tandem mass spectrometry-multiple reaction monitoring quantitation (LC-MS/MS-MRM). A total of 52 PPCPs were quantified in both surface water and sediment. The most frequently quantified PPCPs in water included caffeine, fexofenadine, nicotine, sulfamethoxazole, hydrochlorothiazide, MDA, desvenlafaxine, and metoprolol ranging from 10 to 360 ng/L, and in sediment included diphenhydramine, escitalopram, desvenlafaxine, fexofenadine, sertraline and triclocarban ranging from 20 to 120 ng/g (dry weight). Comparisons of PPCP constituents in WTP discharge and adjacent surface water showed altered compositions reflecting dispersal and transformation processes acted quickly following contact of effluent with surface water. Although the PPCPs were present at their greatest concentrations in surface water near the WTP discharge zones, PPCP concentrations rapidly attenuated yielding mainstem TFPR concentrations relatively consistent along the freshwater reach of the tidal range in the estuary. The PPCP concentrations in sediment maximized in the tributary shoals, but also decreased in the mainstem TFPR similarly to surface water. Compositional analysis showed sorption to geosolids was the most important factor in the loss of PPCPs following WTP discharge in the tributary embayments.

Exposure to 17α-Ethinylestradiol Results in Differential Susceptibility of Largemouth Bass (Micropterus salmoides) to Bacterial Infection

Disease outbreaks, skin lesions, mortality events, and reproductive abnormalities have been observed in wild populations of centrarchids. The presence of estrogenic endocrine disrupting compounds (EEDCs) has been implicated as a potential causal factor for these effects. The effects of prior EEDC exposure on immune response were examined in juvenile largemouth bass (Micropterus salmoides) exposed to a potent synthetic estrogen (17α-ethinylestradiol, EE2) at a low (EE2_Low, 0.87 ng/L) or high (EE2_High, 9.08 ng/L) dose for 4 weeks, followed by transfer to clean water and injection with an LD₄₀ dose of the Gram-negative bacteria Edwardsiella piscicida. Unexpectedly, this prior exposure to EE2_High significantly increased survivorship at 10 d post-infection compared to solvent control or EE2_Low-exposed, infected fish. Both prior exposure and infection with E. piscicida led to significantly reduced hepatic glycogen levels, indicating a stress response resulting in depletion of energy stores. Additionally, pathway analysis for liver and spleen indicated differentially expressed genes associated with immunometabolic processes in the mock-injected EE2_High treatment that could underlie the observed protective effect and metabolic shift in EE2_High-infected fish. Our results demonstrate that exposure to a model EEDC alters metabolism and immune function in a fish species that is ecologically and economically important in North America.

Targeted and non-targeted analysis of young-of-year smallmouth bass using comprehensive two-dimensional gas chromatography coupled with time-of-flight mass spectrometry

Smallmouth bass in the Susquehanna River Basin, Chesapeake Bay Watershed, USA, have been exhibiting clinical signs of disease and reproductive endocrine disruption (e.g., intersex, male plasma vitellogenin) for over fifteen years. Previous histological and targeted chemical analyses have identified infectious agents and pollutants in fish tissues including organic contaminants, mercury, and perfluorinated compounds, but a common causative link for the observed signs of disease across this widespread area has not been determined. This study examines 146 young-of-year smallmouth bass collected from 14 sampling sites in the Susquehanna River Basin, Pennsylvania, USA with varying levels of disease prevalence. Whole fish were extracted by a recently developed modification to the quick, easy, cheap, effective, rugged, and safe extraction method and analyzed by comprehensive two-dimensional gas chromatography coupled with time-of-flight mass spectrometry. A targeted analysis was conducted to identify the presence and quantity of 127 known contaminants, including polychlorinated biphenyls, brominated diphenyl ethers, organochlorinated pesticides, and pharmaceutical and personal care products. A non-targeted analysis was conducted on the same data set to identify analytes of interest not included on routine target compound lists. Chromatographic alignment through Statistical Compare (ChromaTOF GC) was followed by Fisher ratio and principal component analysis to reduce the data set from thousands of peaks per sample to a final data set of 65 analytes of interest. Comparisons of these 65 compounds between Normal (no observed health anomalies) and Lesioned (observed health anomaly at time of collection) fish revealed increased levels of three chemical families in Lesioned fish including esters, ketones, and nitrogen containing compounds.

Watershed-Scale Risk to Aquatic Organisms from Complex Chemical Mixtures in the Shenandoah River

River waters contain complex chemical mixtures derived from natural and anthropogenic sources. Aquatic organisms are exposed to the entire chemical composition of the water, resulting in potential effects at the organismal through ecosystem level. This study applied a holistic approach to assess landscape, hydrological, chemical, and biological variables. On-site mobile laboratory experiments were conducted to evaluate biological effects of exposure to chemical mixtures in the Shenandoah River Watershed. A suite of 534 inorganic and organic constituents were analyzed, of which 273 were detected. A watershed-scale accumulated wastewater model was developed to predict environmental concentrations of chemicals derived from wastewater treatment plants (WWTPs) to assess potential aquatic organism exposure for all stream reaches in the watershed. Measured and modeled concentrations generally were within a factor of 2. Ecotoxicological effects from exposure to individual components of the chemical mixture were evaluated using risk quotients (RQs) based on measured or predicted environmental concentrations and no effect concentrations or chronic toxicity threshold values. Seventy-two percent of the compounds had RQ values <0.1, indicating limited risk from individual chemicals. However, when individual RQs were aggregated into a risk index, most stream reaches receiving WWTP effluent posed potential risk to aquatic organisms from exposure to complex chemical mixtures.

Occurrence and spatial-temporal distribution of atrazine and its metabolites in the aquatic environment of the Volturno River estuary, southern Italy

The present study assesses the spatial distribution and temporal trends of the water dissolved phase (WDP), suspended particulate matter (SPM) and sediment partitioning of atrazine (ATR) and its metabolites in the Volturno River estuary. The load contribution of ATR and its metabolites in this river to the Central Mediterranean Sea was estimated. Samples were collected in 10 sampling sites during the four seasons. The total concentrations of ATR and DPs detected ranged from 18.1 to 105.5 ng L^-1 in WDP, from 4.5 to 63.2 ng L^-1 in SPM, and from 4.6 to 18.6 ng g^-1 in sediment samples, indicating high levels of these pollutants. Structural equation model and the ratio study indicated that the relationship between sediment and WDP pollutants occurred through the SPM. The pollutants load at the Volturno River in its mouth was evaluated in about 30.4 kg year^-1, showing that this river is an important source of these analytes through discharge into Central Mediterranean Sea. Principal component analysis indicated that ATR and its metabolites pollution moves from Volturno River mouth southward and increased in the rainy season. The desethylatrazine-to-atrazine ratio was higher than 0.5 for all samples analyzed, indicating an historical discharge and a long residence time of ATR in sediment about two decades after its ban, and classifying ATR as a nonpoint source contaminant. This study makes up the first record of ATR and its metabolites in superficial water of Southern Italy and provides helpful data as starting point for future studies.

Reproductive health and endocrine disruption in smallmouth bass (Micropterus dolomieu) from the Lake Erie drainage, Pennsylvania, USA

Smallmouth bass Micropterus dolomieu were sampled from three sites within the Lake Erie drainage (Elk Creek, Twentymile Creek, and Misery Bay, an embayment in Presque Isle Bay). Plasma, tissues for histopathological analyses, and liver and testes preserved in RNALater® were sampled from 30 smallmouth bass (of both sexes) at each site. Liver and testes samples were analyzed for transcript abundance with Nanostring nCounter® technology. Evidence of estrogenic endocrine disruption was assessed by the presence and severity of intersex (testicular oocytes; TO) and concentrations of plasma vitellogenin in male fish. Abundance of 17 liver transcripts associated with reproductive function, endocrine activity, and contaminant detoxification pathways and 40 testes transcripts associated with male and female reproductive function, germ cell development, and steroid biosynthesis were also measured. Males with a high rate of TO (87-100%) and plasma vitellogenin were noted at all sites; however, TO severity was greatest at the site with the highest agricultural land cover. Numerous transcripts were differentially regulated among the sites and patterns of transcript abundance were used to better understand potential risk factors for estrogenic endocrine disruption. The results of this study suggest endocrine disruption is prevalent in this region and further research would benefit to identify the types of contaminants that may be associated with the observed biological effects.

Reproductive toxicity due to herbicide exposure in freshwater organisms

Excessively used pesticides in agricultural areas are spilled into aquatic environments, wherein they are suspended or sedimented. Owing to climate change, herbicides are the fastest growing sector of the pesticide industry and are detected in surface water, groundwater, and sediments near agricultural areas. In freshwater, organisms, including mussels, snails, frogs, and fish, are exposed to various types and concentrations of herbicides. Invertebrates are sensitive to herbicide exposure because their defense systems are incomplete. At the top of the food chain in freshwater ecosystems, fish show high bioaccumulation of herbicides. Herbicide exposure causes reproductive toxicity and population declines in freshwater organisms and further contamination of fish used for consumption poses a risk to human health. In addition, it is important to understand how environmental factors are physiologically processed and assess their impacts on reproductive parameters, such as gonadosomatic index and steroid hormone levels. Zebrafish is a good model for examining the effects of herbicides such as atrazine and glyphosate on embryonic development in freshwater fish. This review describes the occurrence and role of herbicides in freshwater environments and their potential implications for the reproduction and embryonic development of freshwater organisms.

Household Drug Management Practices of Residents in a Second-Tier City in China: Opportunities for Reducing Drug Waste and Environmental Pollution

The total amount of drug waste is expanding significantly as populations age and societies become wealthier. Drug waste is becoming a problem for health and the environment. Thus, how to reduce and effectively dispose of drug waste is increasingly becoming an issue for society. This study focuses on household drug management, which involves five sub-practices: selection, purchasing, using, storing, and disposing of drugs. A questionnaire survey was conducted in a second-tier Chinese city that reveals both problems and opportunities in these five sub-practices. The results show that consumers are aware of significant issues with regard to the safe and effective use of drugs as well as with regard to proper ways of disposing of and recycling drugs. Moreover, our analysis reveals promising opportunities for addressing these issues by developing novel services based on the idea of connecting the five involved sub-practices of household drug management. Connecting and adjusting practices in this manner can be seen as an important factor in reducing drug waste and pharmaceutical pollutants.

Identifying Chemicals and Mixtures of Potential Biological Concern Detected in Passive Samplers from Great Lakes Tributaries Using High-Throughput Data and Biological Pathways

Waterborne contaminants were monitored in 69 tributaries of the Laurentian Great Lakes in 2010 and 2014 using semipermeable membrane devices (SPMDs) and polar organic chemical integrative samplers (POCIS). A risk-based screening approach was used to prioritize chemicals and chemical mixtures, identify sites at greatest risk for biological impacts, and identify potential hazards to monitor at those sites. Analyses included 185 chemicals (143 detected) including polycyclic aromatic hydrocarbons (PAHs), legacy and current-use pesticides, fire retardants, pharmaceuticals, and fragrances. Hazard quotients were calculated by dividing detected concentrations by biological effect concentrations reported in the ECOTOX Knowledgebase (toxicity quotients) or ToxCast database (exposure-activity ratios [EARs]). Mixture effects were estimated by summation of EAR values for chemicals that influence ToxCast assays with common gene targets. Nineteen chemicals-atrazine, N,N-diethyltoluamide, di(2-ethylhexyl)phthalate, dl-menthol, galaxolide, p-tert-octylphenol, 3 organochlorine pesticides, 3 PAHs, 4 pharmaceuticals, and 3 phosphate flame retardants-had toxicity quotients >0.1 or EARs for individual chemicals >10^-3 at 10% or more of the sites monitored. An additional 4 chemicals (tributyl phosphate, triethyl citrate, benz[a]anthracene, and benzo[b]fluoranthene) were present in mixtures with EARs >10^-3 . To evaluate potential apical effects and biological endpoints to monitor in exposed wildlife, in vitro bioactivity data were compared to adverse outcome pathway gene ontology information. Endpoints and effects associated with endocrine disruption, alterations in xenobiotic metabolism, and potentially neuronal development would be relevant to monitor at the priority sites. The EAR threshold exceedance for many chemical classes was correlated with urban land cover and wastewater effluent influence, whereas herbicides and fire retardants were also correlated to agricultural land cover. Environ Toxicol Chem 2021;40:2165-2182. Published 2021. This article is a U.S. Government work and is in the public domain in the USA. Environmental Toxicology and Chemistry published by Wiley Periodicals LLC on behalf of SETAC.

Environmental and anthropogenic drivers of contaminants in agricultural watersheds with implications for land management

If not managed properly, modern agricultural practices can alter surface and groundwater quality and drinking water resources resulting in potential negative effects on aquatic and terrestrial ecosystems. Exposure to agriculturally derived contaminant mixtures has the potential to alter habitat quality and negatively affect fish and other aquatic organisms. Implementation of conservation practices focused on improving water quality continues to increase particularly in agricultural landscapes throughout the United States. The goal of this study was to determine the consequences of land management actions on the primary drivers of contaminant mixtures in five agricultural watersheds in the Chesapeake Bay, the largest watershed of the Atlantic Seaboard in North America where fish health issues have been documented for two decades. Surface water was collected and analyzed for 301 organic contaminants to determine the benefits of implemented best management practices (BMPs) designed to reduce nutrients and sediment to streams in also reducing contaminants in surface waters. Of the contaminants measured, herbicides (atrazine, metolachlor), phytoestrogens (formononetin, genistein, equol), cholesterol and total estrogenicity (indicator of estrogenic response) were detected frequently enough to statistically compare to seasonal flow effects, landscape variables and BMP intensity. Contaminant concentrations were often positively correlated with seasonal stream flow, although the magnitude of this effect varied by contaminant across seasons and sites. Land-use and other less utilized landscape variables including biosolids, manure and pesticide application and percent phytoestrogen producing crops were inversely related with site-average contaminant concentrations. Increased BMP intensity was negatively related to contaminant concentrations indicating potential co-benefits of BMPs for contaminant reduction in the studied watersheds. The information gained from this study will help prioritize ecologically relevant contaminant mixtures for monitoring and contributes to understanding the benefits of BMPs on improving surface water quality to better manage living resources in agricultural landscapes inside and outside the Chesapeake Bay watershed.

Perfluoroalkyl Substances in Plasma of Smallmouth Bass from the Chesapeake Bay Watershed

Smallmouth bass Micropterus dolomieu is an economically important sportfish and within the Chesapeake Bay watershed has experienced a high prevalence of external lesions, infectious disease, mortality events, reproductive endocrine disruption and population declines. To date, no clear or consistent associations with contaminants measured in fish tissue or surface water have been found. Therefore, plasma samples from two sites in the Potomac River and two in the Susquehanna River drainage basins, differing in land-use characteristics, were utilized to determine if perfluoroalkyl substances were present. Four compounds, perfluorooctane sulphonic acid (PFOS), perfluoroundecanoic acid (PFUnA), perfluorodecanoic acid (PFDA) and perfluorododecanoic acid (PFDoA), were detected in every fish. Two additional compounds, perfluorooctane sulphonamide (PFOSA) and perfluorononanoic acid (PFNA), were less commonly detected at lower concentrations, depending on the site. Concentrations of PFOS (up to 574 ng/mL) were the highest detected and varied significantly among sites. No seasonal differences (spring versus fall) in plasma concentrations were observed. Concentrations of PFOS were not significantly different between the sexes. However, PFUnA and PFDoA concentrations were higher in males than females. Both agricultural and developed land-use appeared to be associated with exposure. Further research is needed to determine if these compounds could be affecting the health of smallmouth bass and identify sources.

Optimized suspect screening approach for a comprehensive assessment of the impact of best management practices in reducing micropollutants transport in the Potomac River watershed

The vast number of chemicals potentially reaching aquatic environment pose a challenge in maintaining the quality of water resources. However, best management practices to improve water quality are typically focused on reducing nutrient transport without assessing how these practices may impact the occurrence of micropollutants. The potential for co-management of nutrients and organic micropollutants exists, but few studies have comprehensively evaluated the suite of contaminants associated with different water quality management practices (riparian zone restoration, stormwater management, etc.). Furthermore, most studies dealing with the determination of micropollutants in environmental samples include only a limited number of target analytes, leaving many contaminants undetected. To address this limitation, there has been a gradual shift in environmental monitoring from using target analysis to either suspect screening analysis (SSA) or non-targeted analysis (NTA), which relies on accurate mass measurements, mass spectral fragmentation patterns, and retention time information obtained using liquid chromatography coupled to high-resolution mass spectrometry. The work presented in this paper focuses on a wide-scope detection of micropollutants in surface water samples from the Potomac River watershed (United States). An in-house database composed of 1039 compounds based on experimental analysis of primary standards was established, and SSA workflow was optimized and applied to determine the presence of micropollutants in surface water. A total of 103 micropollutants were detected in the samples, some of which are contaminants that were not previously monitored and belong to various classes such as pharmaceuticals, personal care products, per-and polyfluoroalkyl substances and other persistent industrial chemicals. The impact of best management practices being implemented for nitrogen and phosphorus reductions were also assessed for their potential to reduce micropollutant transport. This work illustrates the advantages of suspect screening methods to determine a large number of micropollutants in environmental samples and reveals the potential to co-manage a diverse array of micropollutants based on shared transport and transformation mechanisms in watersheds.

Retrospective analysis of estrogenic endocrine disruption and land-use influences in the Chesapeake Bay watershed

The Chesapeake Bay is the largest estuary in the United States and its watershed includes river drainages in six states and the District of Columbia. Sportfishing is of major economic interest, however, the rivers within the watershed provide numerous other ecological, recreational, cultural and economic benefits, as well as serving as a drinking water source for millions of people. Consequently, major fish kills and the subsequent finding of estrogenic endocrine disruption (intersex or testicular oocytes and plasma vitellogenin in male fishes) raised public and management concerns. Studies have occurred at various sites within the Bay watershed to document the extent and severity of endocrine disruption, identify risk factors and document temporal and spatial variability. Data from these focal studies, which began in 2004, were used in CART (classification and regression trees) analyses to better identify land use associations and potential management practices that influence estrogenic endocrine disruption. These analyses emphasized the importance of scale (immediate versus upstream catchment) and the complex mixtures of stressors which can contribute to surface water estrogenicity and the associated adverse effects of exposure. Both agricultural (percent cultivated, pesticide application, phytoestrogen cover crops) and developed (population density, road density, impervious surface) land cover showed positive relationships to estrogenic indicators, while percent forest and shrubs generally had a negative association. The findings can serve as a baseline for assessing ongoing restoration and management practices.

Evidence that watershed nutrient management practices effectively reduce estrogens in environmental waters

We evaluate the impacts of different nutrient management strategies on the potential for co-managing estrogens and nutrients in environmental waters of the Potomac watershed of the Chesapeake Bay. These potential co-management approaches represent agricultural and urban runoff, wastewater treatment plant effluent, and combined sewer overflow replacements. Twelve estrogenic compounds and their metabolites were analysed by gas chromatography-mass spectrometry. Estrogenic activity (E₂Eq) was measured by in vitro bioassay. We detected estrone E₁ (0.05-6.97 ng L^-1) and estriol E₃ (below detection-8.13 ng L^-1) and one conjugated estrogen (estrone-3-sulfate E₁-3S; below detection-8.13 ng L^-1). E₁ was widely distributed and positively correlated with E₂Eq, water temperature, and dissolved organic carbon (DOC). Among nonpoint sources, E₂Eq, and concentrations of E₁, soluble reactive phosphorus (SRP) and total dissolved nitrogen (TDN) decreased by 51-61%, 77-82%, 62-64%, 4-16% in restored urban and agricultural streams with best management practices (BMPs) relative to unrestored streams without BMPs. In a wastewater treatment plant (Blue Plains WWTP), >94% of E₁, E₁-3S, E₃, E₂Eq and TDN were removed while SRP increased by 305% during nitrification/denitrification as a part of advanced wastewater treatment. Consequently, E₁ and TDN concentrations in WWTP effluents were comparable or even lower than those observed in the receiving stream or river waters, and the effects of wastewater discharges on downstream E₁ and TDN concentrations were minor. Highest E₂Eq value and concentrations of E1, E3, and TDN were detected in combined sewer overflow (CSO). This study suggests that WWTP upgrades with biological nutrient removal, CSO management, and certain agricultural and urban BMPs for nutrient controls have the potential to remove estrogens from point and nonpoint sources along with other contaminants in streams and rivers.

Groundwater discharges as a source of phytoestrogens and other agriculturally derived contaminants to streams

Groundwater discharge zones in streams are important habitats for aquatic organisms. The use of discharge zones for thermal refuge and spawning by fish and other biota renders them susceptible to potential focused discharge of groundwater contamination. Currently, there is a paucity of information about discharge zones as a potential exposure pathway of chemicals to stream ecosystems. Using thermal mapping technologies to locate groundwater discharges, shallow groundwater and surface water from three rivers in the Chesapeake Bay Watershed, USA were analyzed for phytoestrogens, pesticides and their degradates, steroid hormones, sterols and bisphenol A. A Bayesian censored regression model was used to compare groundwater and surface water chemical concentrations. The most frequently detected chemicals in both ground and surface water were the phytoestrogens genistein (79%) and formononetin (55%), the herbicides metolachlor (50%) and atrazine (74%), and the sterol cholesterol (88%). There was evidence suggesting groundwater discharge zones could be a unique exposure pathway of chemicals to surface water systems, in our case, metolachlor sulfonic acid (posterior mean concentration = 150 ng/L in groundwater and 4.6 ng/L in surface water). Our study also demonstrated heterogeneity of chemical concentration in groundwater discharge zones within a stream for the phytoestrogen formononetin, the herbicides metolachlor and atrazine, and cholesterol. Results support the hypothesis that discharge zones are an important source of exposure of phytoestrogens and herbicides to aquatic organisms. To manage critical resources within the Chesapeake Bay Watershed, more work is needed to characterize exposure in discharge zones more broadly across time and space.

The association between toxic pesticide environmental exposure and Alzheimer's disease: A scientometric and visualization analysis

Alzheimer's disease (AD) is one of the most common neurodegenerative diseases. The association between environmental factors (e.g., pesticide) and AD has attracted considerable attention. However, no systematic analysis has been performed and make it difficult to provide deeper insights of AD correlated with pesticide exposure. Hence, this study utilized a bibliometric and visual approach that included map collaborations, co-citations, and keywords, to identifying the knowledge structure, hot topics and the research trends based on 372 publications from the Web of Science Core Collection and PubMed databases. The results showed that 116 institutions from 52 countries published articles in this field. The United States and Israel played a leading role with numerous publications in related journals, as well as prolific institutions and authors, respectively. Three hot topics in pesticide-induced AD were recognized based on co-occurrence keywords detection, including acetylcholinesterase (AChE) inhibitor, oxidative stress, and AChE. Moreover, analysis of keywords burst suggests that some potential molecular mechanisms and therapy targets of pesticide-induced AD, especially for mitochondrial dysfunction and monoamine oxidase-B (MAO-B) that catalyzes the oxidative deamination and causes oxidative stress, are emerging trends. In addition, the study of various pesticides and the assessment method of pesticide exposure will step forward as well. To the best of our knowledge, this study is the first to specifically visualize the relationship between AD and pesticide exposure and to predict potential future research directions.

Effects of early life stage exposure of largemouth bass to atrazine or a model estrogen (17α-ethinylestradiol)

Endocrine disrupting contaminants are of continuing concern for potentially contributing to reproductive dysfunction in largemouth and smallmouth bass in the Chesapeake Bay watershed (CBW) and elsewhere. Exposures to atrazine (ATR) have been hypothesized to have estrogenic effects on vertebrate endocrine systems. The incidence of intersex in male smallmouth bass from some regions of CBW has been correlated with ATR concentrations in water. Fish early life stages may be particularly vulnerable to ATR exposure in agricultural areas, as a spring influx of pesticides coincides with spawning and early development. Our objectives were to investigate the effects of early life stage exposure to ATR or the model estrogen 17α-ethinylestradiol (EE2) on sexual differentiation and gene expression in gonad tissue. We exposed newly hatched largemouth bass (LMB, Micropterus salmoides) from 7 to 80 days post-spawn to nominal concentrations of 1, 10, or 100 µg ATR/L or 1 or 10 ng EE2/L and monitored histological development and transcriptomic changes in gonad tissue. We observed a nearly 100% female sex ratio in LMB exposed to EE2 at 10 ng/L, presumably due to sex reversal of males. Many gonad genes were differentially expressed between sexes. Multidimensional scaling revealed clustering by gene expression of the 1 ng EE2/L and 100 µg ATR/L-treated male fish. Some pathways responsive to EE2 exposure were not sex-specific. We observed differential expression in male gonad in LMB exposed to EE2 at 1 ng/L of several genes involved in reproductive development and function, including star, cyp11a2, ddx4 (previously vasa), wnt5b, cyp1a and samhd1. Expression of star, cyp11a2 and cyp1a in males was also responsive to ATR exposure. Overall, our results confirm that early development is a sensitive window for estrogenic endocrine disruption in LMB and are consistent with the hypothesis that ATR exposure induces some estrogenic responses in the developing gonad. However, ATR-specific and EE2-specific responses were also observed.

Legacy and Contaminants of Emerging Concern in Tree Swallows Along an Agricultural to Industrial Gradient: Maumee River, Ohio

Exposure to multiple classes of contaminants, both legacy and contaminants of emerging concern (CECs), were assessed in tree swallow (Tachycineta bicolor) tissue and diet samples from 6 sites along the Maumee River, Ohio, USA, to understand both exposure and possible effects of exposure to those CECs for which there are little avian data. The 6 sites represented a gradient from intensive agriculture upstream to highly urbanized and industrial landscapes downstream; 1 or 2 remote Wisconsin lakes were assessed for comparative purposes. Cytochrome P450 induction, DNA damage, and thyroid function were also assessed relative to contaminant exposure. Bioaccumulative CECs, such as polybrominated diphenyl ethers (PBDEs) and perfluorinated substances, did not follow any upstream to downstream gradient; but both had significantly greater concentrations along the Maumee River than at the remote lake sites. Greater exposure to PBDEs was apparent in swallows at or near wastewater-treatment facilities than at other sites. Total polychlorinated biphenyl and total polycyclic aromatic hydrocarbon concentrations were greater in swallows at downstream locations compared to upstream sites and were associated with higher ethoxyresorufin-O-dealkylase activity. Few herbicides or nonorganochlorine insecticides were detected in swallow tissues or their food, except for atrazine and its metabolite desethylatrazine. Few pharmaceuticals and personal care products were detected except for DEET and iopamidol. Both were detected in most liver samples but not in eggs, as well as detected at the remote lake sites. This is one of the most comprehensive assessments to date of exposure and effects of a wide variety of CECs in birds. Environ Toxicol Chem 2020;39:1936-1952. © 2020 SETAC. This article has been contributed to by US Government employees and their work is in the public domain in the USA.

Modified QuEChERS extraction for the analysis of young-of-year smallmouth bass using GC × GC-TOFMS

Signs of disease, such as external lesions, have been prevalent in smallmouth bass throughout the Susquehanna River Basin, USA. Previous targeted chemical studies in this system have identified known persistent organic pollutants, but a common explanatory link across multiple affected sites remains undetermined. A fast and robust extraction method that can be applied to young-of-year fish is needed to effectively screen for target and non-target compounds that may be impacting organism health. The quick, easy, cheap, effective, rugged, and safe (QuEChERS) extraction methodology was optimized to perform both targeted and non-targeted chemical analyses from a single extraction of whole young-of-year fish. Comprehensive two-dimensional gas chromatography coupled with time-of-flight mass spectrometry (GC × GC-TOFMS) was used for extract analysis. Sample extraction was performed using the solvent ethyl acetate, followed by a two-step cleanup in which samples were frozen for lipid removal and subjected to dispersive solid phase extraction using Florisil. A sample of 21 young-of-year smallmouth bass collected from areas with disease and exhibiting different types of external lesions were evaluated for 233 target compounds. A total of 34 organic contaminants, including polychlorinated biphenyls, brominated diphenyl ethers, organochlorinated pesticides, and personal care products, were detected. Data from this sample set was then analyzed for non-targets. Using the Fisher ratio method and multivariate analysis, an additional 10 significant features were identified specific to either fish with visible lesions or with no visible disease characteristics.

Making 'Chemical Cocktails' - Evolution of Urban Geochemical Processes across the Periodic Table of Elements

Urbanization contributes to the formation of novel elemental combinations and signatures in terrestrial and aquatic watersheds, also known as 'chemical cocktails.' The composition of chemical cocktails evolves across space and time due to: (1) elevated concentrations from anthropogenic sources, (2) accelerated weathering and corrosion of the built environment, (3) increased drainage density and intensification of urban water conveyance systems, and (4) enhanced rates of geochemical transformations due to changes in temperature, ionic strength, pH, and redox potentials. Characterizing chemical cocktails and underlying geochemical processes is necessary for: (1) tracking pollution sources using complex chemical mixtures instead of individual elements or compounds; (2) developing new strategies for co-managing groups of contaminants; (3) identifying proxies for predicting transport of chemical mixtures using continuous sensor data; and (4) determining whether interactive effects of chemical cocktails produce ecosystem-scale impacts greater than the sum of individual chemical stressors. First, we discuss some unique urban geochemical processes which form chemical cocktails, such as urban soil formation, human-accelerated weathering, urban acidification-alkalinization, and freshwater salinization syndrome. Second, we review and synthesize global patterns in concentrations of major ions, carbon and nutrients, and trace elements in urban streams across different world regions and make comparisons with reference conditions. In addition to our global analysis, we highlight examples from some watersheds in the Baltimore-Washington DC region, which show increased transport of major ions, trace metals, and nutrients across streams draining a well-defined land-use gradient. Urbanization increased the concentrations of multiple major and trace elements in streams draining human-dominated watersheds compared to reference conditions. Chemical cocktails of major and trace elements were formed over diurnal cycles coinciding with changes in streamflow, dissolved oxygen, pH, and other variables measured by high-frequency sensors. Some chemical cocktails of major and trace elements were also significantly related to specific conductance (p<0.05), which can be measured by sensors. Concentrations of major and trace elements increased, peaked, or decreased longitudinally along streams as watershed urbanization increased, which is consistent with distinct shifts in chemical mixtures upstream and downstream of other major cities in the world. Our global analysis of urban streams shows that concentrations of multiple elements along the Periodic Table significantly increase when compared with reference conditions. Furthermore, similar biogeochemical patterns and processes can be grouped among distinct mixtures of elements of major ions, dissolved organic matter, nutrients, and trace elements as chemical cocktails. Chemical cocktails form in urban waters over diurnal cycles, decades, and throughout drainage basins. We conclude our global review and synthesis by proposing strategies for monitoring and managing chemical cocktails using source control, ecosystem restoration, and green infrastructure. We discuss future research directions applying the watershed chemical cocktail approach to diagnose and manage environmental problems. Ultimately, a chemical cocktail approach targeting sources, transport, and transformations of different and distinct elemental combinations is necessary to more holistically monitor and manage the emerging impacts of chemical mixtures in the world's fresh waters.

Spatiotemporal variation in occurrence and co-occurrence of pesticides, hormones, and other organic contaminants in rivers in the Chesapeake Bay Watershed, United States

Investigating the spatiotemporal dynamics of contaminants in surface water is crucial to better understand how introduced chemicals are interacting with and potentially influencing aquatic organisms and environments. Within the Chesapeake Bay Watershed, United States, there are concerns about the potential role of contaminant exposure on fish health. Evidence suggests that exposure to contaminants in surface water is causing immunosuppression and intersex in freshwater fish species. Despite these concerns, there is a paucity of information regarding the complex dynamics of contaminant occurrence and co-occurrence in surface water across both space and time. To address these concerns, we applied a Bayesian hierarchical joint-contaminant model to describe the occurrence and co-occurrence patterns of 28 contaminants and total estrogenicity across six river sites and over three years. We found that seasonal occurrence patterns varied by contaminant, with the highest occurrence probabilities during the spring and summer months. Additionally, we found that the proportion of agricultural landcover in the immediate catchment, as well as stream discharge, did not have a significant effect on the occurrence probabilities of most compounds. Four pesticides (atrazine, metolachlor, fipronil and simazine) co-occurred across sites after accounting for environmental covariates. These results provide baseline information on the contaminant occurrence patterns of several classes of compounds within the Chesapeake Bay Watershed. Understanding the spatiotemporal dynamics of contaminants in surface water is the first step in investigating the effects of contaminant exposure on fisheries and aquatic environments.

Paradigm shifts and current challenges in wastewater management

Wastewater is a significant environmental and public health concern which management is a constant challenge since antiquity. Wastewater research has increased exponentially over the last decades. This paper provides a global overview of the exponentially increasing wastewater research in order to identify current challenges and paradigm shifts. Besides households, hospitals and typical industries, other sources of wastewater appear due to emerging activities like hydraulic fracturing. While the composition of wastewater needs constant reassessment to identify contaminants of interest, the comprehensive chemical and toxicological analysis remains one of the main challenges in wastewater research. Moreover, recent changes in the public perception of wastewater has led to several paradigm shifts: i) water reuse considering wastewater as a water resource rather than a hazardous waste, ii) wastewater-based epidemiology considering wastewater as a source of information regarding the overall health of a population through the analysis of specific biomarkers, iii) circular economy through the implementation of treatment processes aiming at harvesting valuable components such as precious metals or producing valuable goods such as biofuel. However, wastewater research should also address social challenges such as the public acceptance of water reuse or the access to basic sanitation that is not available for nearly a third of the world population.

Embryo/larval toxicity and transcriptional effects in zebrafish (Danio rerio) exposed to endocrine active riverbed sediments

Sediment toxicity plays a fundamental role in the health of inland fish communities; however, the assessment of the hazard potential of contaminated sediments is not a common objective in environmental diagnostics or remediation. This study examined the potential of transcriptional endpoints investigated in zebrafish (Danio rerio) exposed to riverbed sediments in ecotoxicity testing. Embryo-larval 10-day tests were conducted on sediment samples collected from five sites (one upstream and four downstream of the city of Milan) along a polluted tributary of the Po River, the Lambro River. Sediment chemistry showed a progressive downstream deterioration in river quality, so that the final sampling site showed up to eight times higher concentrations of, for example, triclosan, galaxolide, PAH, PCB, BPA, Ni, and Pb, compared with the uppermost site. The embryo/larval tests showed widespread toxicity although the middle river sections evidenced worse effects, as evidenced by delayed embryo development, hatching rate, larval survival, and growth. At the mRNA transcript level, the genes encoding biotransformation enzymes (cyp1a, gst, ugt) showed increasing upregulations after exposure to sediment from further downstream sites. The genes involved in antioxidant responses (sod, gpx) suggested that more critical conditions may be present at downstream sites, but even upstream of Milan there seemed to be some level of oxidative stress. Indirect evidences of potential apoptotic activity (bcl2/bax < 1) in turn suggested the possibility of genotoxic effects. The genes encoding for estrogen receptors (erα, erβ1, erβ2) showed exposure to (xeno)estrogens with a progressive increase after exposure to sediments from downstream sites, paralleled by a corresponding downregulation of the ar gene, likely related to antiandrogenic compounds. Multiple levels of thyroid disruption were also evident particularly in downstream zebrafish, as for thyroid growth (nkx2.1), hormone synthesis and transport (tg, ttr, d2), and signal transduction (trα, trβ). The inhibition of the igf2 gene reasonably reflected larval growth inhibitions. Although none of the sediment chemicals could singly explain fish responses, principal component analysis suggested a good correlation between gene transcripts and the overall trend of contamination. Thus, the combined impacts from known and unknown covarying chemicals were proposed as the most probable explanation of fish responses. In summary, transcriptional endpoints applied to zebrafish embryo/larval test can provide sensitive, comprehensive, and timeliness information which may greatly enable the assessment of the hazard potential of sediments to fish, complementing morphological endpoints and being potentially predictive of longer studies.

Histopathologic Prevalence and Severity of Testicular Oocytes in Smallmouth Bass from Two Archival Collections

During recent decades, survey studies have documented the widespread presence of oocytes in the testes of male Smallmouth Bass Micropterus dolomieu collected from surface waters throughout the United States. There are few published reports of testicular oocytes (TO) in Smallmouth Bass before the 1990s, so it is difficult to know how long this has been occurring. Consequently, this study was conducted to evaluate the prevalence and severity of TO occurrence in whole fish specimens from two archival collections-the Smithsonian Institution's National Museum of Natural History in Suitland, Maryland, and Cornell University's Museum of Vertebrates in Ithaca, New York. Gonads were excised from 167 preserved male Smallmouth Bass that were originally collected between 1875 and 2004, and routine histologic sections were prepared and examined. The severity of TO was determined using a semiquantitative scoring system. Overall, 52.1% of male Smallmouth Bass were found to have TO. Affected fish had been collected in 11 of the 18 represented states, and TO were found in specimens harvested during decades as early as the 1880s and 1900s. Unfortunately, the small number of samples acquired at the earliest time periods precluded analyses of prevalence and severity trends over time. The results of this study demonstrated that the phenomenon of TO in male Smallmouth Bass is at least a century old and confirmed the widespread nature of this finding throughout the species' historic range. Further research efforts should focus on determining the baseline prevalence of TO in laboratory-reared male Smallmouth Bass that have not been exposed to endocrine active substances or the effects of experimental estrogen exposure on such fish.

Quality screening of the Lagos lagoon sediment by assessing the cytotoxicity and toxicological responses of rat hepatoma H4IIE and fish PLHC-1 cell-lines using different extraction approaches

In this study, sediment samples from Makoko and Ikorodu sites of the Lagos lagoon (Nigeria) were screened for toxicological responses on mammalian and fish cell lines using different extraction methods. Rat hepatoma H4IIE and fish PLHC-1 cell-lines were exposed to serial dilutions of the elutriate, polar and non-polar extracts. We evaluated exposed cells for cytotoxicity and aryl hydrocarbon receptor (AhR)-mediated toxicity. Cells exposed to polar and water extracts from Makoko and Ikorodu showed viability percentage of >80% at 48 h. On the other hand, exposure to the non-polar extracts exhibited cell viability of 50-60% at all tested dilutions. For both cell lines, a significant concentration-dependent induction of cyp1a mRNA was observed after exposure to the different extracts from both sites. Interestingly, the extracts affected functional enzymes differently for both cell lines. For H4IIE cells, while EROD activity paralleled cyp1a mRNA expression patterns, MROD showed significant concentration-specific reduction in cells exposed to polar and water extracts. On the contrary, while the MROD activity paralleled cyp1a mRNA, EROD activity was significantly inhibited in PLHC-1 cells exposed to water-, polar and non-polar extracts from both sites. These observations paralleled sediments PAH contamination burden from the study sites as revealed by co-relation analysis. In conclusion, although the different extracts did not exert high cytotoxic effects (except the non-polar) at the tested concentrations, they significantly modulated phase I biotransformation responses, showing that the studied sediments contain complex chemical mixture in the different extracts, with potential for overt physiological and general health consequences.

Expired Medication: Societal, Regulatory and Ethical Aspects of a Wasted Opportunity

A massive volume of expired medications amasses annually around the world because of pharmaceutical overprescription, combined with overproduction. The accumulation of pharmaceutical waste imposes ecological, economic and social/ethical burdens. Managing this presumed “waste” has developed into a global challenge due to the absence of specific regulations, unreasonable behavior of the patients, and an improper understanding of the concept of “expired medications” in general. This paper summaries, first, the recent literature reporting practices related to the disposal of unused medications. In this context, 48 papers from 34 countries with a total of 33,832 participants point towards a significant lack of public awareness regarding the appropriate disposal of such biologically potent chemicals. These findings are corroborated by a local survey on the disposal practices of unused medicines among pharmacy students at Saarland University. The regulatory aspects surrounding this topic, often based on the official guidelines for the disposal of expired medications and local waste management strategies, are then discussed in light of these findings. Finally, a closer inspection of the epistemic values of expired medications and different strategies for managing expired medications have been reviewed.

In vitro immune function in laboratory-reared age-0 smallmouth bass (Micropterus dolomieu) relative to diet

Smallmouth bass (Micropterus dolomieu) are used as an indicator species in environmental monitoring and assessment studies. However, laboratory-based studies for methods development and effector assessment are limited for this species. Nutrition, a known modulator of teleost physiological responses including immune function, is a critical knowledge-gap sometimes overlooked in the design of laboratory studies. We report the results from a study evaluating a commercially available artificial pelleted diet for bass and live feed (fathead minnows). Following a six-month diet-acclimation period, age-0 smallmouth bass were assessed using morphometric measures, histologic and immune-function end points using conventional methods, miniaturized cell isolation and assay methods as well as imaging flow cytometry. Fish on the two diets did not significantly differ in length, weight, or condition factor, indicating that growth was similar in the two groups. Histologic examination revealed relatively higher levels of macrophage aggregates and accumulation of ceroid/lipofuscin in the spleen as well as hepatocyte changes in the pellet-fed group. Leukocytes from the pellet-fed group exhibited significantly elevated bactericidal activity and significantly depressed mitogen response compared to fish fed live feed. Following exposure to a known inducer of inflammatory responses, bacterial lipopolysaccharide, responses including the transition of leukocytes to an apoptotic/necrotic condition differed significantly based on diet. Histologic findings were consistent with the occurrence of diet-related oxidative stress in the pellet-fed fish. Oxidative stress can be induced by multiple factors including environmental pollutants. For a diet to be useful in laboratory-based studies, it cannot elicit response that could also be induced by experimental treatments. To do so greatly complicates the detection of experimental effects. Until an artificial diet is developed for smallmouth bass that does not produce potentially confounding conditions for laboratory-based studies, use of a live feed appears to be the best option.

Integrated Assessment of Wastewater Reuse, Exposure Risk, and Fish Endocrine Disruption in the Shenandoah River Watershed

Reuse of municipal and industrial wastewater treatment plant (WWTP) effluent is used to augment freshwater supplies globally. The Shenandoah River Watershed (U.S.A.) was selected to conduct on-site exposure experiments to assess endocrine disrupting characteristics of different source waters. This investigation integrates WWTP wastewater reuse modeling, hydrological and chemical characterization, and in vivo endocrine disruption bioassessment to assess contaminant sources, exposure pathways, and biological effects. The percentage of accumulated WWTP effluent in each river reach (ACCWW%) was used to predict environmental concentrations for consumer product chemicals (boron), pharmaceutical compounds (carbamazepine), and steroidal estrogens (estrone, 17-β-estradiol, estriol, and 17-α-ethinylestradiol). Fish endocrine disruption was evaluated using vitellogenin induction in adult male or larval fathead minnows. Water samples were analyzed for >500 inorganic and organic constituents to characterize the complex contaminant mixtures. Municipal ACCWW% at drinking water treatment plant surface water intakes ranged from <0.01 to 2.0% under mean-annual streamflow and up to 4.5% under mean-August streamflow. Measured and predicted environmental concentrations resulted in 17-β-estradiol equivalency quotients ranging from 0.002 to 5.0 ng L^-1 indicating low-to-moderate risk of fish endocrine disruption. Results from the fish exposure experiments showed low (0.5- to 3.2-fold) vitellogenin induction in adult males.

Assessing the effects of Awba dam sediment (Nigeria) on the steroidogenesis of H295R cells using different extraction methods

In the present study, H295R human cells were used to investigate the endocrine disruptor potential of three different sediments extracts taken from a Nigerian tropical freshwater dam (Awba Dam), using three extraction methods that allowed a selective consideration of contaminants based on their binding affinity, which is mainly driven by polarity, to sediment particles. After exposure to different concentration of each extract, H295R cells were evaluated for the expression profiles of 10 steroidogenic enzyme genes and estradiol (E2) and testosterone (T) levels. Our results showed a comparable concentrated-related increase in the expression of 17β-hsd1, 3β-hsd2 and cyp21 in cells treated with the polar and non-polar extracts. The star, hmgr, cyp11b2 and 17β-hsd4 were slightly decreased, in an apparent concentration-specific manner, after treatment with the polar extract and decreased in the non-polar treatment. The cyp11a and cyp17 showed an opposite trend in the polar and non-polar treatments. E2 was significantly higher in cell treated with the non-polar extract. Elutriate exposure produced less pronounced variation in mRNA and hormones levels. Overall the extract with non-polar compounds produced the most severe effects in H295R cells. Thus, direct ingestion of detritus and mud from fishes and other benthonic organisms represent possible transfer of contaminants in the trophic web, and mainly account for alteration of the endocrine system previously observed in fish from the same study site.

Temporal evaluation of estrogenic endocrine disruption markers in smallmouth bass (Micropterus dolomieu) reveals seasonal variability in intersex

A reconnaissance project completed in 2009 identified intersex and elevated plasma vitellogenin in male smallmouth bass inhabiting the Missisquoi River, VT. In an attempt to identify the presence and seasonality of putative endocrine disrupting chemicals or other factors associated with these observations, a comprehensive reevaluation was conducted between September 2012 and June 2014. Here, we collected smallmouth bass from three physically partitioned reaches along the river to measure biomarkers of estrogenic endocrine disruption in smallmouth bass. In addition, polar organic chemical integrative samples (POCIS) were deployed to identify specific chemicals associated with biological observations. We did not observe biological differences across reaches indicating the absence of clear point source contributions to the observation of intersex. Interestingly, intersex prevalence and severity decreased in a stepwise manner over the timespan of the project. Intersex decreased from 92.8% to 28.1%. The only significant predictor of intersex prevalence was year of capture, based on logistic regression analysis. The mixed model of fish length and year-of-capture best predicted intersex severity. Intersex severity was also significantly different across late summer and early spring collections indicating seasonal changes in this metric. Plasma vitellogenin and liver vitellogenin Aa transcript abundance in males did not indicate exposure to estrogenic endocrine disrupting chemicals at any of the four sample collections. Analysis of chemicals captured by the POCIS as well as results of screening discrete water samples or POCIS extracts did not indicate the contribution of appreciable estrogenic chemicals. It is possible that unreported changes in land-use activity have ameliorated the problem, and our observations indicate recovery. Regardless, this work clearly emphasizes that single, snap shot sampling for intersex may not yield representative data given that the manifestation of this condition within a population can change dramatically over time.

Comparison of steroidogenic gene expression in mummichog (Fundulus heteroclitus) testis tissue following exposure to aromatizable or non-aromatizable androgens

Androgens are a recognized class of endocrine disrupting compounds with the ability to impact reproductive status in aquatic organisms. The current study utilized in vitro exposure of mummichog (Fundulus heteroclitus) testis tissue to either the aromatizable androgen 17α-methyltestosterone (MT) or the non-aromatizable androgen 5α-dihydrotestosterone (DHT) over the course of 24 h to determine if there were differential effects on steroidogenic gene expression. Testis tissue was exposed to androgen concentrations of 10^-12 M, 10^-9 M and 10^-6 M for 6, 12, 18 or 24 h, after which a suite of steroidogenic genes, including steroidogenic acute regulatory protein, 3β-hydroxysteroid dehydrogenase (3βhsd) and cytochrome P450 17A1 (cyp17a1), were quantified using real-time polymerase chain reaction. Both androgens affected steroidogenic gene expression, with most alterations occurring at the 24-hour time point. The gene with the highest fold-change, and shortest interval to expression alteration, was 3βhsd for both androgens. Potential differences between the two model androgens were observed in increased expression of cyp17a1 and 11β-hydroxysteroid dehydrogenase (11βhsd), which were only altered after exposure to DHT and in expression levels of cytochrome P450 11A1 (cyp11a1), which was upregulated by MT but not altered by DHT. Results from this study show both androgens interact at the gonadal level of the hypothalamus-pituitary-gonadal axis and may possess some distinct gene expression impacts. These data strengthen the current research initiatives of establishing in vitro test systems that allow toxic potential of untested chemicals to be predicted from molecular perturbations.

Towards the Response Threshold for p-Hydroxyacetophenone in the Denitrifying Bacterium "Aromatoleum aromaticum" EbN1

The denitrifying betaproteobacterium "Aromatoleum aromaticum" EbN1 regulates the capacity to anaerobically degrade p-ethylphenol (via p-hydroxyacetophenone) with high substrate specificity. This process is mediated by the σ⁵⁴-dependent transcriptional regulator EtpR, which apparently recognizes both aromatic compounds, yielding congruent expression profiles. The responsiveness of this regulatory system was studied with p-hydroxyacetophenone, which is more easily administered to cultures and traced analytically. Cultures of A. aromaticum EbN1 were initially cultivated under nitrate-reducing conditions with a growth-limiting supply of benzoate, upon the complete depletion of which p-hydroxyacetophenone was added at various concentrations (from 500 μM down to 0.1 nM). Depletion profiles of this aromatic substrate and presumptive effector were determined by highly sensitive micro-high-performance liquid chromatography (microHPLC). Irrespective of the added concentration of p-hydroxyacetophenone, depletion commenced after less than 5 min and suggested a response threshold of below 10 nM. This approximation was corroborated by time-resolved transcript profiles (quantitative reverse transcription-PCR) of selected degradation and efflux relevant genes (e.g., pchF, encoding a subunit of predicted p-ethylphenol methylenehydroxylase) and narrowed down to a range of 10 to 1 nM. The most pronounced transcriptional response was observed, as expected, for genes located at the beginning of the two operon-like structures, related to catabolism (i.e., acsA) and potential efflux (i.e., ebA335).IMPORTANCE Aromatic compounds are widespread microbial growth substrates with natural as well as anthropogenic sources, albeit with their in situ concentrations and their bioavailabilities varying over several orders of magnitude. Even though degradation pathways and underlying regulatory systems have long been studied with aerobic and, to a lesser extent, with anaerobic bacteria, comparatively little is known about the effector concentration-dependent responsiveness. A. aromaticum EbN1 is a model organism for the anaerobic degradation of aromatic compounds with the architecture of the catabolic network and its substrate-specific regulation having been intensively studied by means of differential proteogenomics. The present study aims at unraveling the minimal concentration of an aromatic growth substrate (p-hydroxyacetophenone here) required to initiate gene expression for its degradation pathway and to learn in principle about the lower limit of catabolic responsiveness of an anaerobic degradation specialist.

Contaminants of emerging concern presence and adverse effects in fish: A case study in the Laurentian Great Lakes

The Laurentian Great Lakes are a valuable natural resource that is affected by contaminants of emerging concern (CECs), including sex steroid hormones, personal care products, pharmaceuticals, industrial chemicals, and new generation pesticides. However, little is known about the fate and biological effects of CECs in tributaries to the Great Lakes. In the current study, 16 sites on three rivers in the Great Lakes basin (Fox, Cuyahoga, and Raquette Rivers) were assessed for CEC presence using polar organic chemical integrative samplers (POCIS) and grab water samplers. Biological activity was assessed through a combination of in vitro bioassays (focused on estrogenic activity) and in vivo assays with larval fathead minnows. In addition, resident sunfish, largemouth bass, and white suckers were assessed for changes in biological endpoints associated with CEC exposure. CECs were present in all water samples and POCIS extracts. A total of 111 and 97 chemicals were detected in at least one water sample and POCIS extract, respectively. Known estrogenic chemicals were detected in water samples at all 16 sites and in POCIS extracts at 13 sites. Most sites elicited estrogenic activity in bioassays. Ranking sites and rivers based on water chemistry, POCIS chemistry, or total in vitro estrogenicity produced comparable patterns with the Cuyahoga River ranking as most and the Raquette River as least affected by CECs. Changes in biological responses grouped according to physiological processes, and differed between species but not sex. The Fox and Cuyahoga Rivers often had significantly different patterns in biological response Our study supports the need for multiple lines of evidence and provides a framework to assess CEC presence and effects in fish in the Laurentian Great Lakes basin.

Monitoring tylosin and sulfamethazine in a tile-drained agricultural watershed using polar organic chemical integrative sampler (POCIS)

This study evaluated the influence of temporal variation on the occurrence, fate, and transport of tylosin (TYL) and sulfamethazine (SMZ); antibiotics commonly used in swine production. Atrazine (ATZ) was used as a reference analyte to indicate the agricultural origin of the antibiotics. We also assessed the impact of season and hydrology on antibiotic concentrations. A reconnaissance study of the South Fork watershed of the Iowa River (SFIR), was conducted from 2013 to 2015. Tile drain effluent and surface water were monitored using polar organic integrative sampler (POCIS) technology. Approximately 169 animal feeding operations (AFOs) exist in SFIR, with 153 of them being swine facilities. All analytes were detected, and detection frequencies ranged from 69 to 100% showing the persistence in the watershed. Antibiotics were detected at a higher frequency using POCIS compared to grab samples. We observed statistically significant seasonal trends for SMZ and ATZ concentrations during growing and harvest seasons. Time weighted average (TWA) concentrations quantified from the POCIS were 1.87ngL^-1 (SMZ), 0.30ngL^-1 (TYL), and 754.2ngL^-1 (ATZ) in the watershed. SMZ and TYL concentrations were lower than the minimum inhibitory concentrations (MIC) for E. coli. All analytes were detected in tile drain effluent, confirming tile drainage as a pathway for antibiotic transport. Our results identify the episodic occurrence of antibiotics, and highlights the importance identifying seasonal fate and occurrence of these analytes.

Testicular oocytes in smallmouth bass in northeastern Minnesota in relation to varying levels of human activity

Testicular oocytes (TOs) have been found in black bass (Micropterus spp.) from many locations in North America. The presence of TOs is often assumed to imply exposure to estrogenic endocrine disrupting compounds (EDCs); however, a definitive causal relationship has yet to be established, and TO prevalence is not consistently low in fish from areas lacking evident EDC sources. This might indicate any of a number of situations: 1) unknown or unidentified EDCs or EDC sources, 2) induction of TOs by other stressors, or 3) testicular oocytes occurring spontaneously during normal development. In the present study, we analyzed TO occurrence in smallmouth bass (Micropterus dolomieu) from 8 populations in northeastern Minnesota watersheds with differing degrees of human development and, hence, presumed likelihood of exposure to anthropogenic chemicals. Three watersheds were categorized as moderately developed, based on the presence of municipal wastewater discharges and higher human population density (4-81 per km² ), and 5 watersheds were minimally developed, with very low human population density (0-1 per km² ) and minimal built environment. Testicular tissues from mature fish were evaluated using a semiquantitative method that estimated TO density, normalized by cross-sectional area. Testicular oocyte prevalence and density among populations from moderately developed watersheds was higher than in populations from minimally developed watersheds. However, TO prevalence was unexpectedly high and variable (7-43%) in some populations from minimally developed watersheds, and only weak evidence was found for a relationship between TO density and watershed development, suggesting alternative or more complex explanations for TO presence in smallmouth bass from this region. Environ Toxicol Chem 2017;36:3424-3435. © 2017 SETAC.

Gonadal intersex in smallmouth bass Micropterus dolomieu from northern Indiana with correlations to molecular biomarkers and anthropogenic chemicals

Over the past decade, studies have shown that exposure to endocrine disrupting chemicals (EDCs) can cause gonadal intersex in fish. Smallmouth bass (Micropterus dolomieu) males appear to be highly susceptible to developing testicular oocytes (TO), the most prevalent form of gonadal intersex, as observed in various areas across the U.S. In this study, prevalence and severity of TO was quantified for smallmouth bass sampled from the St. Joseph River in northern Indiana, intersex biomarkers were developed, and association between TO prevalence and organic contaminants were explored. At some sites, TO prevalence reached maximum levels before decreasing significantly after the spawning season. We examined the relationship between TO presence and expression of gonadal and liver genes involved in sex differentiation and reproductive functions (esr1, esr2, foxl2, fshr, star, lhr and vtg). We found that vitellogenin (vtg) transcript levels were significantly higher in the liver of males with TO, but only when sampled during the spawning season. Further, we identified a positive correlation between plasma VTG levels and vtg transcript levels, suggesting its use as a non-destructive biomarker of TO in this species. Finally, we evaluated 43 contaminants in surface water at representative sites using passive sampling to look for contaminants with possible links to the observed TO prevalence. No quantifiable levels of estrogens or other commonly agreed upon EDCs such as the bisphenols were observed in our contaminant assessment; however, we did find high levels of herbicides as well as consistent quantifiable levels of PFOS, PFOA, and triclosan in the watershed where high TO prevalence was exhibited. Our findings suggest that the observed TO prevalence may be the result of exposures to mixtures of nonsteroidal EDCs.

Nonlethal laparoscopic detection of intersex (testicular oocytes) in largemouth bass (Micropterus salmoides) and smallmouth bass (Micropterus dolomieu)

Intersex in wild fish populations has received considerable attention in the scientific literature and public media. Conventional detection of testicular oocytes, the presence of immature oocytes within testis of male fish, commonly employs transverse sectioning of excised testis and is lethal. The present study used a nonlethal laparoscopic technique to collect biopsies of testis from black bass, entering the body cavity via the genital pore. Detection of testicular oocytes was compared between biopsy and conventional methods using 79 smallmouth bass (Micropterus dolomieu) from 8 sites and 68 largemouth bass (Micropterus salmoides) from 4 sites. The 2 methods performed similarly at sites where testicular oocyte severity was moderate or high (6 of 8 smallmouth bass sites), whereas transverse sectioning resulted in superior testicular oocyte detection at sites where severity was low (2 of 8 smallmouth bass sites and all 4 largemouth bass sites). In smallmouth bass, testicular oocyte prevalence by transverse and biopsy methods was strongly correlated across sites (r²  = 0.81) and severity reported by enumeration of testicular oocytes was moderately correlated across sites (r² = 0.59). Survival of a subset of largemouth bass (n = 20) to 28 d after laparoscopic surgery was 90%. The present research indicates that laparoscopy may be useful for monitoring the prevalence and severity of testicular oocytes in Micropterus species, particularly when lethal sampling is precluded. Environ Toxicol Chem 2017;36:1924-1933. © 2016 SETAC.

Endocrine active contaminants in aquatic systems and intersex in common sport fishes

Male fish are susceptible to developing intersex, a condition characterized by the presence of testicular oocytes. In the present study, the relationship between intersex and exposure to estrogenic endocrine active contaminants (EACs) was assessed for 2 genera of sport fish, Micropterus and Lepomis, at 20 riverine sites. Seasonal trends and relationships between EACs and intersex (prevalence and severity) were examined at varying putative sources of EACs throughout North Carolina, identified as point sources, nonpoint sources, and reference sites. Intersex was identified in both genera, which was documented for the first time in wild-caught Lepomis. Intersex was more prevalent (59.8%) and more severe (1.6 mean rank) in Micropterus, which was highly correlation to EACs in sediment. In contrast, intersex was less common (9.9%) and less severe (0.2 mean rank) in Lepomis and was highly correlated to EACs in the water column. The authors found that concentrations of polycyclic aromatic hydrocarbons, polychlorinated biphenyls, industrial EACs, and estrogens were highest at point source sites; however, no source type variation was identified in the prevalence or severity of intersex, nor were there seasonal trends in intersex or EAC concentrations. The authors' results associate genus-specific prevalence of intersex with specific EAC classes in common sport fishes having biological, ecological, and conservation implications. Environ Toxicol Chem 2017;36:959-968. © 2016 SETAC.

Complex mixtures of Pesticides in Midwest U.S. streams indicated by POCIS time-integrating samplers

The Midwest United States is an intensely agricultural region where pesticides in streams pose risks to aquatic biota, but temporal variability in pesticide concentrations makes characterization of their exposure to organisms challenging. To compensate for the effects of temporal variability, we deployed polar organic chemical integrative samplers (POCIS) in 100 small streams across the Midwest for about 5 weeks during summer 2013 and analyzed the extracts for 227 pesticide compounds. Analysis of water samples collected weekly for pesticides during POCIS deployment allowed for comparison of POCIS results with periodic water-sampling results. The median number of pesticides detected in POCIS extracts was 62, and 141 compounds were detected at least once, indicating a high level of pesticide contamination of streams in the region. Sixty-five of the 141 compounds detected were pesticide degradates. Mean water concentrations estimated using published POCIS sampling rates strongly correlated with means of weekly water samples collected concurrently, however, the POCIS-estimated concentrations generally were lower than the measured water concentrations. Summed herbicide concentrations (units of ng/POCIS) were greater at agricultural sites than at urban sites but summed concentrations of insecticides and fungicides were greater at urban sites. Consistent with these differences, summed concentrations of herbicides correlate to percent cultivated crops in the watersheds and summed concentrations of insecticides and fungicides correlate to percent urban land use. With the exception of malathion concentrations at nine sites, POCIS-estimated water concentrations of pesticides were lower than aquatic-life benchmarks. The POCIS provide an alternative approach to traditional water sampling for characterizing chronic exposure to pesticides in streams across the Midwest region.

Critical assessment of the ubiquitous occurrence and fate of the insect repellent N,N-diethyl-m-toluamide in water

The insect repellent diethyltoluamide (DEET) is among the most frequently detected organic chemical contaminants in water across a wide range of geographies from around the world. These observations are raising critical questions and increasing concerns regarding potential environmental relevance, particularly when the emergence of severe neurological conditions attributed to the Zika virus has increased the use of insect repellents. After dermal application, DEET is washed from the skin when bathing and enters the municipal sewer system before discharge into the environment. Mainly measured by gas chromatography or liquid chromatography coupled to mass spectrometry (GC-MS or LC-MS), more than 200 peer-reviewed publications have already reported concentrations of DEET ranging ng/L to mg/L in several water matrices from North America, Europe, Asia, Oceania, and more recently Africa and South America. While conventional wastewater treatment technology has limited capacity of removal, advanced technologies are capable of better attenuation and could lower the environmental discharge of organic contaminants, including DEET. For instance, adsorption on activated carbon, desalinating membrane processes (nanofiltration and reverse osmosis), ozonation, and advanced oxidation processes can achieve 50% to essentially 100% DEET attenuation. Despite the abundant literature on the topic, the ubiquity of DEET in the environment still raises questions due to the apparent lack of obvious spatio-temporal trends in concentrations measured in surface water, which does not fit the expected usage pattern of insect repellents. Moreover, two recent studies showed discrepancies between the concentrations obtained by GC-MS and LC-MS analyses. While the occurrence of DEET in the environment is well established, the concentrations reported should be interpreted cautiously, considering the disparities in methodologies applied and occurrence patterns observed. Therefore, this manuscript provides a critical overview of the origin of DEET in the environment, the relevant analytical methods, the occurrence reported in peer-reviewed literature, and the attenuation efficacy of water treatment processes.

Evaluation of potential mechanisms of atrazine-induced reproductive impairment in fathead minnow (Pimephales promelas) and Japanese medaka (Oryzias latipes)

Atrazine has been implicated in reproductive dysfunction of exposed organisms, and previous studies documented decreased egg production in Japanese medaka (Oryzias latipes) and fathead minnows (Pimephales promelas) during 30-d to 38-d exposures to 0.5 µg/L, 5 µg/L, and 50 µg/L atrazine. The authors evaluated possible mechanisms underlying the reduction in egg production. Gene expression in steroidogenesis pathways and the hypothalamus-pituitary-gonad axis of male and female fish was measured. Atrazine did not significantly induce gonad aromatase (cyp19a1a) expression. An atrazine-induced shift in the number of females in an active reproductive state was observed. Expression of the egg maturation genes vitellogenin 1 (vtg1) and zona pellucida glycoprotein 3.1 (zp3.1) in medaka females was correlated and had a bimodal distribution. In both species, females with low vtg1 or zp3.1 expression also had low expression of steroidogenesis genes in the gonad, estrogen receptor in the liver, and gonadotropins in the brain. In the medaka, the number of females per tank that had high expression of zp3.1 was significantly correlated with egg production per tank. The number of medaka females with low expression of zp3.1 increased significantly with atrazine exposure. Thus, the decline in egg production observed in response to atrazine exposure may be the result of a coordinated downregulation of genes required for reproduction in a subset of females. Environ Toxicol Chem 2016;35:2230-2238. Published 2016 Wiley Periodicals Inc. on behalf of SETAC. This article is a US Government work and, as such, is in the public domain in the United States of America.