Solid-liquid distribution of SARS-CoV-2 in primary effluent of a wastewater treatment plant

Distributions of Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) and fecal viral biomarkers between solid and liquid phases of wastewater are largely unknown. Herein, distributions of SARS-CoV-2, Pepper Mild Mottle Virus (PMMoV), and F-RNA bacteriophage group II (FRNAPH-II) were determined by viral RNA RT-qPCR. Comparison of viral recovery using three conventional fractionation methods included membrane filtration, a combination of mid-speed centrifugation and membrane filtration, and high-speed centrifugation. SARS-CoV-2 partitioned to the solids fraction in greater abundance compared to liquid fractions in a combination of mid-speed centrifugation and membrane filtration and high-speed centrifugation, but not in membrane filtration method in a particular assay, while fecal biomarkers (PMMoV and FRNAPH-II) exhibited the reciprocal relationship. The wastewater fractionation method had minimal effects on the solids-liquids distribution for all viral and phage markers tested; however, viral RNA load was significantly greater in solid-liquid fractions viral RNA loads compared with the than whole-wastewater PEG precipitation. A RNeasy PowerWater Kit with PCR inhibitor removal resulted in greater viral RNA loads and lesser PCR inhibition compared to a QIAamp Viral RNA Mini Kit without PCR inhibitor removal. These results support the development of improved methods and interpretation of WBE of SARS-CoV-2. •Distribution of SARS-CoV-2 to liquid and solid portions was addressed.•Addressing PCR inhibition is important in wastewater-based epidemiology.•Fraction methods have minimal effect.

Japanese medaka (Oryzias latipes) exposed via maternal transfer to the brominated flame retardant, 1,2,5,6-tetrabromocyclooctane (TBCO), experience decreased fecundity and impaired oocyte maturation

Early life-stage exposure of fishes to endocrine disrupting chemicals can induce reproductive impairment at sexual maturity. Previously, we demonstrated decreased fecundity of Japanese medaka (Oryzias latipes) exposed via maternal transfer to the novel brominated flame retardant, 1,2,5,6-tetrabromocyclooctane (TBCO). However, that study failed to identify the causative mechanism. In other studies we have shown that decreased fecundity of adult fish exposed to dietary TBCO is likely due to impaired oocyte maturation. The goal of the present study was to determine if impaired oocyte maturation is responsible for decreased fecundity of Japanese medaka exposed as embryos to TBCO, via maternal transfer. Sexually mature fish (F0) were fed either a control diet or a low (74.7 μg/g) or high (663 μg/g) diet containing TBCO for 21 days. Eggs (F1) were collected during the final week of exposure and reared to sexual maturity at which point fecundity was assessed using a 21-day reproduction assay. Upon termination of the assay, an ex vivo oocyte maturation assay was used to determine whether maturation inducing hormone (MIH) stimulated oocyte maturation was impaired. Additionally, concentrations of 17β -estradiol (E2) in blood plasma and expression of genes involved in vitellogenesis and oocyte maturation were quantified. The F1 generation females reared from the low or high F0 treatments experienced a 26.0 % and 56.8 % decrease in cumulative fecundity, respectively. Ex vivo MIH stimulated oocyte maturation from the low and high TBCO treatments were decreased by 23.4 % and 20.0 % respectively. There was no significant effect on concentrations of E2. Transcript abundance of vtgI was significantly decreased in a concentration dependent manner. Transcript abundance of mPRα, pgrmc1, pgrmc2, and igf3 were decreased but effects were not statistically significant. Overall, results suggest that impaired oocyte maturation causes decreased fecundity of Japanese medaka exposed to maternally deposited TBCO.

Assessment of rapid wastewater surveillance for determination of communicable disease spread in municipalities

Wastewater surveillance (WS) helps to improve the understanding of the spread of communicable diseases in communities. WS can assist public health decision-makers in the design and implementation of timely mitigation measures. There is an increased need to use reliable, cost-effective, simple, and rapid WS systems, given traditional analytical (or 'gold-standard') programs are instrument/time-intensive, and dependent on highly skilled personnel. This study investigated the application of the portable GeneXpert platform for WS of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), influenza A virus (IAV), influenza B virus (IBV), and respiratory syncytial virus (RSV). The GeneXpert system with the Xpert Xpress-SARS-CoV-2/Flu/RSV test kit uses reverse transcription-quantitative polymerase chain reaction (RT-qPCR) to analyze wastewater samples. From September 2022 through January 2023, wastewater samples were collected from the influents of municipal wastewater treatment plants (MWTPs) of Saskatoon, Prince Albert, and North Battleford in the province of Saskatchewan, Canada. Both raw and concentrated wastewater samples were subjected to the GeneXpert analysis. Results showed that the Saskatoon wastewater viral loads were significantly correlated to Saskatchewan's influenza and COVID-19 clinical cases, with a lead time of 10 days for IAV and a lag time of 4 days for SARS-CoV-2. Additionally, the GeneXpert analysis of the three cities' wastewater samples showed that the raw WS could capture the dynamics of SARS-CoV-2 and IAV due to their correlation with concentrated WS. Interestingly, IBV loads were not detected in any wastewater samples, while the Saskatoon and Prince Albert wastewater samples collected following the 2023 holiday season (end of December and beginning of January) were positive for RSV. This study indicates that the GeneXpert has excellent potential for use in the development of an early warning system for transmissible disease in municipalities and limited-resource communities while simultaneously providing stakeholders with an efficient WS methodology.

Identification of Mid-Polar and Polar AhR Agonists in Cetaceans from Korean Coastal Waters: Application of Effect-Directed Analysis with Full-Scan Screening

Major aryl hydrocarbon receptor (AhR) agonists were identified in extracts of blubber, liver, and muscle from six long-beaked common dolphins (Delphinus capensis) and one fin whale (Balaenoptera physalus) collected from Korean coastal waters using effect-directed analysis. Results of the H4IIE-luc bioassay indicated that the polar fractions of blubber and liver extracts from the fin whale exhibited relatively high AhR-mediated potencies. Based on full-scan screening with high-resolution mass spectrometry, 37 AhR agonist candidates, spanning four use categories: pharmaceuticals, pesticides, cosmetics, and natural products, were selected. Among these, five polar AhR agonists were newly identified through toxicological confirmation. Concentrations of polar AhR agonists in cetaceans were tissue-specific, with extracts of blubber and liver containing greater concentrations than muscle extracts. Polar AhR agonists with great log KOA values (>5) were found to biomagnify in the marine food chain potentially. Polar AhR agonists contributed 8.9% of the observed AhR-mediated potencies in blubber and 49% in liver. Rutaecarpine and alantolactone contributed significantly to the total AhR-mediated potencies of blubber, whereas hydrocortisone was a major AhR contributor in the liver of the fin whale. This study is the first to identify the tissue-specific accumulation of polar AhR agonists in blubber and liver extracts of cetaceans.

Impairment of oocyte maturation as a mechanism of decreased fecundity in Japanese medaka (Oryzias latipes) exposed to the brominated flame retardant, 1,2,5,6-tetrabromocyclooctane (TBCO)

Inhibition of oocyte maturation is an understudied mechanism by which chemical stressors can impair fecundity of female fishes. The primary objective of the present study was to develop an assay to assess oocyte maturation disruption by chemical stressors in Japanese medaka (Oryzias latipes). First, an in vitro assay to assess maturation inducing hormone (MIH)-stimulated oocyte maturation in zebrafish was validated for use with Japanese medaka. Next, using the brominated flame retardant, 1,2,5,6-tetrabromocyclooctane (TBCO), which previously was shown to decrease fecundity of Japanese medaka and inhibit oocyte maturation in zebrafish, effects on oocyte maturation were quantified using in vitro and in vivo exposure. Adaptation of the protocol for in vitro MIH-stimulated maturation of stage IV oocytes from zebrafish was successful in inducing greater than 80% of stage IX oocytes from female Japanese medaka to mature. To assess effects of in vitro exposure, stage IX oocytes were exposed to 0, 2, 20, and 200 μg/L of TBCO, followed by exposure to MIH. The in vitro exposure caused a significant decrease in maturation of oocytes exposed to 20 and 200 μg/L of TBCO. To assess effects of TBCO on fecundity and oocyte maturation following in vivo exposure, sexually mature fish were fed a control, 100 μg/g, or 1000 μg/g concentration of TBCO-spiked fish food for 21 days, where fecundity was measured daily, and following the exposure, stage IX oocytes were excised to assess MIH-stimulated maturation. Fecundity and oocyte maturation were significantly decreased at either concentration of TBCO. Plasma concentrations of 17β-estradiol (E2) and hepatic abundances of transcripts of vitellogenin (vtgI and vtgII) were quantified, but there were no significant differences between treatments. Results suggest that inhibition of oocyte maturation is a mechanism by which TBCO decreases fecundity, and that in vitro assays of oocyte maturation might be predictive of fecundity in this species.

A wastewater-based risk index for SARS-CoV-2 infections among three cities on the Canadian Prairie

Wastewater surveillance (WWS) is useful to better understand the spreading of coronavirus disease 2019 (COVID-19) in communities, which can help design and implement suitable mitigation measures. The main objective of this study was to develop the Wastewater Viral Load Risk Index (WWVLRI) for three Saskatchewan cities to offer a simple metric to interpret WWS. The index was developed by considering relationships between reproduction number, clinical data, daily per capita concentrations of virus particles in wastewater, and weekly viral load change rate. Trends of daily per capita concentrations of SARS-CoV-2 in wastewater for Saskatoon, Prince Albert, and North Battleford were similar during the pandemic, suggesting that per capita viral load can be useful to quantitatively compare wastewater signals among cities and develop an effective and comprehensible WWVLRI. The effective reproduction number (R_t) and the daily per capita efficiency adjusted viral load thresholds of 85 × 10⁶ and 200 × 10⁶ N2 gene counts (gc)/population day (pd) were determined. These values with rates of change were used to categorize the potential for COVID-19 outbreaks and subsequent declines. The weekly average was considered 'low risk' when the per capita viral load was 85 × 10⁶ N2 gc/pd. A 'medium risk' occurs when the per capita copies were between 85 × 10⁶ and 200 × 10⁶ N2 gc/pd. with a rate of change <100 %. The start of an outbreak is indicated by a 'medium-high' risk classification when the week-over-week rate of change was >100 %, and the absolute magnitude of concentrations of viral particles was >85 × 10⁶ N2 gc/pd. Lastly, a 'high risk' occurs when the viral load exceeds 200 × 10⁶ N2 gc/pd. This methodology provides a valuable resource for decision-makers and health authorities, specifically given the limitation of COVID-19 surveillance based on clinical data.

Understanding common population markers for SARS-CoV-2 RNA normalization in wastewater - A review

Wastewater monitoring and epidemiology have seen renewed interest during the recent COVID-19 pandemic. As a result, there is an increasing need to normalize wastewater-derived viral loads in local populations. Chemical tracers, both exogenous and endogenous compounds, have proven to be more stable and reliable for normalization than biological indicators. However, differing instrumentation and extraction methods can make it difficult to compare results. This review examines current extraction and quantification methods for ten common population indicators: creatinine, coprostanol, nicotine, cotinine, sucralose, acesulfame, androstenedione 5-hydroindoleacetic acid (5-HIAA), caffeine, and 1,7-dimethyluric acid. Some wastewater parameters such as ammonia, total nitrogen, total phosphorus, and daily flowrate were also evaluated. The analytical methods included direct injection, dilute and shoot, liquid/liquid, and solid phase extraction (SPE). Creatine, acesulfame, nicotine, 5-HIAA and androstenedione have been analysed by direct injection into LC-MS; however, most authors prefer to include SPE steps to avoid matrix effects. Both LC-MS and GC-MS have been successfully used to quantify coprostanol in wastewater, and the other selected indicators have been quantified successfully with LC-MS. Acidification to stabilize the sample before freezing to maintain the integrity of samples has been reported to be beneficial. However, there are arguments both for and against working at acidic pHs. Wastewater parameters mentioned earlier are quick and easy to quantify, but the data does not always represent the human population effectively. A preference for population indicators originating solely from humans is apparent. This review summarises methods employed for chemical indicators in wastewater, provides a basis for choosing an appropriate extraction and analysis method, and highlights the utility of accurate chemical tracer data for wastewater-based epidemiology.

Sorption behaviour and toxicity of an herbicide safener "cyprosulfamide"

Cyprosulfamide is a herbicide safener that works against the injurious effects of herbicides such as isoxaflutole, dicamba, nicosulfuron, tembotrione, thiencarbazone-methyl. However, its sorption behaviour in soils and toxicity to aquatic organisms are yet to be thoroughly examined. This study determined the octanol-water partition coefficient, sorption properties, acute and chronic toxic effects, and potency of cyprosulfamide to the cladoceran water flea (Daphnia magna). The influence of soil properties such as organic carbon content, cation exchange capacity, pH, and field capacity on adsorption and desorption properties were also examined. The Log K_ow (0.55) of cyprosulfamide was less than that of some other safeners, such as benoxacor or furilazole, found in aquatic environments. The sorption of cyprosulfamide to the soil was driven by pH, so sorption decreased with an increase in pH. Other characteristics, such as cation exchange capacity (CEC), organic carbon content, and field capacity, do not directly correlate with the distribution coefficient. Cyprosulfamide generally has a low affinity for soil and is thus mobile and prone to transport to surrounding surface waters. No lethality was observed at the highest concentration (120 mg/L) tested for acute toxicity to D. magna; hence the LC50 will be >120 mg/L. During chronic exposures, cyprosulfamide caused adverse effects at a concentration of 120 mg/L on the number of neonates and brood size. The death rate for the chronic study was a function of concentration and increased with days of exposure. Cyprosulfamide is unlikely to cause lethality to D. magna at relevant environmental concentrations.

The brominated flame retardant, 1,2,5,6-tetrabromocyclooctane (TBCO), causes multigenerational effects on reproductive capacity of Japanese medaka (Oryzias latipes)

Exposure of fishes to endocrine disrupting chemicals (EDCs) during early development can induce multigenerational and transgenerational effects on reproduction. Both in vivo and in vitro studies have demonstrated that the brominated flame retardant, 1,2,5,6-tetrabromocyclooctane (TBCO), is an EDC. The present study investigated whether TBCO has mutigenerational and/or transgenerational effects on the reproductive performance of Japanese medaka (Oryzias latipes). Sexually mature fish (F0 generation) were fed either a control diet or a low (40.6 μg/g) or high (1034.4 μg/g) diet containing TBCO, and three generations of embryos were reared to determine reproductive performance using a standard 21-day reproduction assay. Concentrations of TBCO in eggs (F1 generation) from F0 fish given the low and high diets were 711.3 and 2535.5 ng/g wet weight, respectively. Cumulative fecundity of the F1 generation in the low and high treatment were reduced by 33.9% and 33.3%, respectively, compared to the control. In the F2 generation, cumulative fecundity of the low treatment returned to the level of the controls, but the high treatment was decreased by 29.8%. There was no decrease in cumulative fecundity in the F3 generation compared to the controls. Mechanistically, mRNA abundances of cholesterol side chain cleavage enzyme (cyp11a), aromatase (cyp19a), and luteinizing hormone receptor (lhr) were differentially expressed in gonads from F1 females, suggesting that TBCO might cause developmental reprogramming that disrupts steroidogenesis leading to decreased fecundity. However, concentrations of E2 in plasma and mRNA abundance of vitellogenin in liver were not significantly different compared to controls suggesting a mechanism other than disruption of steroidogenesis or vitellogenesis. Mechanistically, no effects were observed in the F2 or F3 generation. Overall, results suggest that TBCO has multigenerational effects on the reproductive performance of Japanese medaka. However, no transgenerational effects were observed as the F3 generation fully recovered. The mechanism by which multigenerational effects were induced is not known.

RNA in Municipal Wastewater Reveals Magnitudes of COVID-19 Outbreaks across Four Waves Driven by SARS-CoV-2 Variants of Concern

There are no standardized protocols for quantifying severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) in wastewater to date, especially for population normalization. Here, a pipeline was developed, applied, and assessed to quantify SARS-CoV-2 and key variants of concern (VOCs) RNA in wastewater at Saskatoon, Canada. Normalization approaches using recovery ratio and extraction efficiency, wastewater parameters, or population indicators were assessed by comparing to daily numbers of new cases. Viral load was positively correlated with daily new cases reported in the sewershed. Wastewater surveillance (WS) had a lead time of approximately 7 days, which indicated surges in the number of new cases. WS revealed the variant α and δ driving the third and fourth wave, respectively. The adjustment with the recovery ratio and extraction efficiency improved the correlation between viral load and daily new cases. Normalization of viral concentration to concentrations of the artificial sweetener acesulfame K improved the trend of viral load during the Christmas and New Year holidays when populations were dynamic and variable. Acesulfame K performed better than pepper mild mottle virus, creatinine, and ammonia for population normalization. Hence, quality controls to characterize recovery ratios and extraction efficiencies and population normalization with acesulfame are promising for precise WS programs supporting decision-making in public health.

Rapid transition between SARS-CoV-2 variants of concern Delta and Omicron detected by monitoring municipal wastewater from three Canadian cities

Monitoring the communal incidence of COVID-19 is important for both government and residents of an area to make informed decisions. However, continuous reliance on one means of monitoring might not be accurate because of biases introduced by government policies or behaviours of residents. Wastewater surveillance was employed to monitor concentrations of SARS-CoV-2 RNA in raw influent wastewater from wastewater treatment plants serving three Canadian Prairie cities with different population sizes. Data obtained from wastewater are not directly influenced by government regulations or behaviours of individuals. The means of three weekly samples collected using 24 h composite auto-samplers were determined. Viral loads were determined by RT-qPCR, and whole-genome sequencing was used to charaterize variants of concern (VOC). The dominant VOCs in the three cities were the same but with different proportions of sub-lineages. Sub-lineages of Delta were AY.12, AY.25, AY.27 and AY.93 in 2021, while the major sub-lineage of Omicron was BA.1 in January 2022, and BA.2 subsequently became a trace-level sub-variant then the predominant VOC. When each VOC was first detected varied among cities; However, Saskatoon, with the largest population, was always the first to present new VOCs. Viral loads varied among cities, but there was no direct correlation with population size, possibly because of differences in flow regimes. Population is one of the factors that affects trends in onset and development of local outbreaks during the pandemic. This might be due to demography or the fact that larger populations had greater potential for inter- and intra-country migration. Hence, wastewater surveillance data from larger cities can typically be used to indicate what to expect in smaller communities.

Rapid transition between SARS-CoV-2 variants of concern Delta and Omicron detected by monitoring municipal wastewater from three Canadian cities

Monitoring the communal incidence of COVID-19 is important for both government and residents of an area to make informed decisions. However, continuous reliance on one means of monitoring might not be accurate because of biases introduced by government policies or behaviours of residents. Wastewater surveillance was employed to monitor concentrations of SARS-CoV-2 RNA in raw influent wastewater from wastewater treatment plants serving three Canadian Prairie cities with different population sizes. Data obtained from wastewater are not directly influenced by government regulations or behaviours of individuals. The means of three weekly samples collected using 24 h composite auto-samplers were determined. Viral loads were determined by RT-qPCR, and whole-genome sequencing was used to charaterize variants of concern (VOC). The dominant VOCs in the three cities were the same but with different proportions of sub-lineages. Sub-lineages of Delta were AY.12, AY.25, AY.27 and AY.93 in 2021, while the major sub-lineage of Omicron was BA.1 in January 2022, and BA.2 subsequently became a trace-level sub-variant then the predominant VOC. When each VOC was first detected varied among cities; However, Saskatoon, with the largest population, was always the first to present new VOCs. Viral loads varied among cities, but there was no direct correlation with population size, possibly because of differences in flow regimes. Population is one of the factors that affects trends in onset and development of local outbreaks during the pandemic. This might be due to demography or the fact that larger populations had greater potential for inter- and intra-country migration. Hence, wastewater surveillance data from larger cities can typically be used to indicate what to expect in smaller communities.

Absorption and elimination of per and poly-fluoroalkyl substances substitutes in salmonid species after pre-fertilization exposure

Due to their relatively large production and few restrictions on uses, novel substitutes for historically used per and poly-fluoroalkyl substances (PFAS) are being used and accumulating in the environment. However, due to a lack of information on their toxicological properties their hazards and risks are hard to estimate. Before fertilization, oocytes of two salmonid species, Arctic Char (Salvelinus alpinus) and Rainbow Trout (Oncorhynchus mykiss), were exposed to three PFAS substances used as substitutes for traditional PFAS, PFBA, PFBS or GenX or two archetypical, historically used, longer-chain PFAS, PFOA and PFOS. Exposed oocytes were subsequently fertilized, incubated and were sampled during several developmental stages, until swim-up. All five PFAS were accumulated into egg yolks with similar absorption rates, and their concentrations in egg yolks were less than respective concentrations in/on egg chorions. Rapid elimination of the five PFAS was observed during the first 3 days after fertilization. Thereafter, amounts of PFOS and PFOA were stable until swim-up, while PFBA, PFBS and GenX were further eliminated during development from one month after the fertilization to swim-up. In these two salmonid species, PFBA, PFBS and GenX were eliminated faster than were PFOS or PFOA.

RNA in Municipal Wastewater Reveals Magnitudes of COVID-19 Outbreaks across Four Waves Driven by SARS-CoV-2 Variants of Concern

There are no standardized protocols for quantifying severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) in wastewater to date, especially for population normalization. Here, a pipeline was developed, applied, and assessed to quantify SARS-CoV-2 and key variants of concern (VOCs) RNA in wastewater at Saskatoon, Canada. Normalization approaches using recovery ratio and extraction efficiency, wastewater parameters, or population indicators were assessed by comparing to daily numbers of new cases. Viral load was positively correlated with daily new cases reported in the sewershed. Wastewater surveillance (WS) had a lead time of approximately 7 days, which indicated surges in the number of new cases. WS revealed the variant α and δ driving the third and fourth wave, respectively. The adjustment with the recovery ratio and extraction efficiency improved the correlation between viral load and daily new cases. Normalization of viral concentration to concentrations of the artificial sweetener acesulfame K improved the trend of viral load during the Christmas and New Year holidays when populations were dynamic and variable. Acesulfame K performed better than pepper mild mottle virus, creatinine, and ammonia for population normalization. Hence, quality controls to characterize recovery ratios and extraction efficiencies and population normalization with acesulfame are promising for precise WS programs supporting decision-making in public health.

Wastewater surveillance gave early warnings of four waves of COVID-19. Quality controls and normalization with acesulfame K significantly improved the accuracy of the wastewater-based epidemiology.

16S rRNA metabarcoding unearths responses of rare gut microbiome of fathead minnows exposed to benzo[a]pyrene

Activities of gut microbiomes are often overlooked in assessments of ecotoxicological effects of environmental contaminants. Effects of the polycyclic aromatic hydrocarbon, benzo[a]pyrene (BaP) on active gut microbiomes of juvenile fathead minnows (Pimephales promelas) were investigated. Fish were exposed for two weeks, to concentrations of 0, 1, 10, 100, or 1000 μg BaP g^-1 in the diet. The active gut microbiome was characterized using 16S rRNA metabarcoding to determine its response to dietary exposure of BaP. BaP reduced alpha-diversity at the greatest exposure concentrations. Additionally, exposure to BaP altered community composition of active microbiome and resulted in differential proportion of taxa associated with hydrocarbon degradation and fish health. Neighborhood selection networks of active microbiomes were not reduced with greater concentrations of BaP, which suggests ecological resistance and/or resilience of gut microbiota. The active gut microbiome had a similar overall biodiversity as that of the genomic gut microbiota, but had a distinct composition from that of the 16S rDNA profile. Responses of alpha- and beta-diversities of the active microbiome to BaP exposure were consistent with that of genomic microbiomes. Normalized activity of microbiome via the ratio of rRNA to rDNA abundance revealed rare taxa that became active or dormant due to exposure to BaP. These differences highlight the need to assess both 16S rDNA and rRNA metabarcoding to fully derive bacterial compositional changes resulting from exposure to contaminants.

Inflammation of Gill Epithelia in Fish Causes Increased Permeation of Petrogenic Polar Organic Chemicals via Disruption of Tight Junctions

The epithelial cell layer that lines the gills of fish controls paracellular permeation of chemicals through tight junctions. The integrity of tight junctions can be affected by inflammation, which likely affects the bioavailability of chemicals. Here, the inflammation of the rainbow trout gill cell line RTgill-W1 was induced via exposure to bacterial lipopolysaccharides (LPS). Cells were then coexposed to extracts of oil sands process-affected water (OSPW), which contain complex mixtures of chemicals. After 24 h of exposure, cells exposed to LPS showed a reduction in transepithelial electrical resistance, an indicator of tight junction integrity. Quantitative reverse-transcription polymerase chain reaction (RT-PCR) analysis determined that abundances of transcripts of genes coding for tight junction proteins were significantly less in cells exposed to 20, 50, or 100 mg L^-1 LPS. Chemical analysis revealed increased permeation of constituents of OSPW across epithelia at all studied LPS concentrations. These in vitro findings were confirmed in vivo in rainbow trout exposed to LPS and OSPW for 48 h, which resulted in greater accumulation of chemicals relative to that for fish exposed to OSPW alone. Our results demonstrated that inflammation and disruption of tight junctions could lead to greater uptake of potentially harmful chemicals from the environment, which has implications for mixture risk assessment.

Sensitivity of a Model Reptile, the Common Snapping Turtle (Chelydra serpentina), to In Ovo Exposure to 2,3,7,8-Tetrachlorodibenzo-p-Dioxin and Other Dioxin-Like Chemicals

Reptiles represent the least-studied group of vertebrates with regards to ecotoxicology and no empirical toxicity data existed for dioxin-like chemicals (DLCs). This lack of toxicity data represents a significant uncertainty in ecological risk assessments of this taxon. Therefore, the present study assessed early-life sensitivity to select DLCs and developed relative potencies in the common snapping turtle (Chelydra serpentina) as a model reptile. Specifically, survival to hatch and incidence of pathologies were assessed in common snapping turtle exposed in ovo to serial concentrations of the prototypical reference congener 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD), and three other DLCs of environmental relevance, namely, 2,3,4,7,8-pentachlorodibenzofuran (PeCDF), 2,3,7,8-tetrachlorodibenzofuran (TCDF), and 3,3',4,4',5-pentachlorobiphenyl (PCB 126). In ovo exposure to TCDD, PeCDF, TCDF, and PCB 126 caused a dose-dependent increase in early-life mortality, with median lethal doses (LD50s) of 14.9, 11.8, 29.6, and 185.9 pg/g-egg, respectively. Except for abnormal vasculature development, few pathologies were observed. Based on the measured LD50, common snapping turtle is more sensitive to TCDD in ovo than other species of oviparous vertebrates investigated to date. The potencies of PeCDF, TCDF, and PCB 126 relative to TCDD were 1.3, 0.5, and 0.08, respectively. These relative potencies are within an order of magnitude of World Health Organization (WHO) TCDD-equivalency factors (TEFs) for both mammals and birds supporting these TEFs as relevant for assessing ecological risk to reptiles. The great sensitivity to toxicities of the common snapping turtle, and potentially other species of reptiles, suggests a clear need for further investigation into the ecotoxicology of this taxon. Environ Toxicol Chem 2022;41:175-183. © 2021 SETAC.

Prefertilization Exposure of Rainbow Trout Eggs to Per- and Polyfluoroalkyl Substances to Simulate Accumulation During Oogenesis

Aqueous film-forming foams (AFFFs) are used in firefighting and are sources of per- and polyfluoroalkyl substances (PFAS) to the environment through surface runoff and groundwater contamination at defense and transportation sites. Little is known regarding the toxicity and bioaccumulation of newer AFFF formulations containing novel PFAS. To mimic maternal transfer of PFAS, prefertilization rainbow trout eggs were exposed to three PFAS using novel methodologies. Batches of unfertilized oocytes were exposed for 3 h to 0, 0.01, 0.1, 1, or 10 µg/ml separately to perfluorooctanoic acid, perfluorohexanoic acid, or perfluorooctanesulfonic acid in either coelomic fluid or Cortland's solution. After exposure, the gametes were fertilized and rinsed with dechlorinated water. Egg yolk was aspirated from a subset of fertilized eggs for PFAS quantification. Each PFAS was detected in yolks of eggs exposed to the respective PFAS, and yolk concentrations were directly proportional to concentrations in aqueous media to which they were exposed. Exposure in coelomic fluid or Cortland's solution resulted in similar concentrations of PFAS in egg yolks. Ratios of PFAS concentrations in oocytes to concentrations in exposure media (oocyte fluid ratios) were <0.99 when exposed from 0.01 to 10 µg/ml and <0.45 when exposed from 0.1 to 10 µg/ml for both media and all three PFAS, demonstrating that the water solubility of the chemicals was relatively great. Prefertilization exposure of eggs effectively introduced PFAS into unfertilized egg yolk. This method provided a means of mimicking maternal transfer to evaluate toxicity to developing embryos from an early stage. This method is more rapid and efficient than injection of individual fertilized eggs and avoids trauma from inserting needles into eggs. Environ Toxicol Chem 2021;40:3159-3165. © 2021 SETAC.

Toxicokinetic Models for Bioconcentration of Organic Contaminants in Two Life Stages of White Sturgeon (Acipenser transmontanus)

The white sturgeon (Acipenser transmontanus) is an endangered ancient fish species that is known to be particularly sensitive to certain environmental contaminants, partly because of the uptake and subsequent toxicity of lipophilic pollutants prone to bioconcentration as a result of their high lipid content. To better understand the bioconcentration of organic contaminants in this species, toxicokinetic (TK) models were developed for the embryo-larval and subadult life stages. The embryo-larval model was designed as a one-compartment model and validated using whole-body measurements of benzo[a]pyrene (B[a]P) metabolites from a waterborne exposure to B[a]P. A physiologically based TK (PBTK) model was used for the subadult model. The predictive power of the subadult model was validated with an experimental data set of four chemicals. Results showed that the TK models could accurately predict the bioconcentration of organic contaminants for both life stages of white sturgeon within 1 order of magnitude of measured values. These models provide a tool to better understand the impact of environmental contaminants on the health and the survival of endangered white sturgeon populations.

The brominated flame retardant, TBCO, impairs oocyte maturation in zebrafish (Danio rerio)

The brominated flame retardant, 1,2,5,6-tetrabromocyclooctane (TBCO), has been shown to decrease fecundity in Japanese medaka (Oryzias latipes) and there is indirect evidence from analysis of the transcriptome and proteome that this effect might be due to impaired oogenesis. An assay for disruption of oocyte maturation by chemical stressors has not been developed in Japanese medaka. Thus, using zebrafish (Danio rerio) as a model, objectives of the present study were to determine whether exposure to TBCO has effects on maturation of oocytes and to investigate potential mechanisms. Sexually mature female zebrafish were given a diet of 35.3 or 628.8 μg TBCO / g food for 14 days after which, stage IV oocytes were isolated to assess maturation in response to maturation inducing hormone. To explore potential molecular mechanisms, abundances of mRNAs of a suite of genes that regulate oocyte maturation were quantified by use of quantitative real-time PCR, and abundances of microRNAs were determined by use of miRNAseq. Ex vivo maturation of oocytes from fish exposed to TBCO was significantly less than maturation of oocytes from control fish. The percentage of oocytes which matured from control fish and those exposed to low and high TBCO were 89, 71, and 67%, respectively. Among the suite of genes known to regulate oocyte maturation, mRNA abundance of insulin like growth factor-3 was decreased by 1.64- and 3.44-fold in stage IV oocytes from females given the low and high concentrations of TBCO, respectively, compared to the control group. Abundances of microRNAs regulating the expression of proteins that regulate oocyte maturation, including processes related to insulin-like growth factor, were significantly different in stage IV oocytes from fish exposed to TBCO. Overall, results of this study indicated that impaired oocyte maturation might be a mechanism of reduced reproductive performance in TBCO-exposed fish. Results also suggested that effects of TBCO on oocyte maturation might be due to molecular perturbations on insulin-like growth factor signaling and expression of microRNAs.

Health status of fathead minnow (Pimephales promelas) populations in a municipal wastewater effluent-dominated stream in the Canadian prairies, Wascana Creek, Saskatchewan

Their unique hydrological and climatic conditions render surface water systems in the southern Canadian Prairies at an elevated risk from exposure to contaminants released from municipal wastewater effluents (MWWEs). The aim of this study was to characterize the potential health effects and their underlying molecular mechanisms in populations of fathead minnow (Pimephales promelas; FHM) in Wascana Creek, an effluent dominated stream in Southern Saskatchewan, Canada. Studies were conducted during the spawning season in 2014 and 2015 to assess responses in terms of overall health, reproductive functions, plasma sex steroid hormone levels, and expression of selected genes along the hypothalamus-pituitary-gonadal axis. FHM downstream of the effluent fallout had lower gonadosomatic indices and significantly greater hepatosomatic indices compared to upstream populations. In both male and female FHMs, significantly greater occurrence and severity of gonadal degradation and delayed maturation were observed in downstream fish compared to upstream fish. Downstream males also displayed lower scores of secondary sexual characteristics and a decreasing trend in plasma 11-ketotestosterone levels. Interestingly, no indications of exposure to estrogenic compounds, such as occurrence of testicular oocytes were observed, which was in accordance with the lack of presence of key biomarkers of estrogenic exposure, such as induction of vitellogenin. In general, expression of the majority of transcripts measured in FHMs downstream of the effluent fallout was significantly downregulated, which supports observations of the general deterioration of the health and reproductive status of these fish. Chemical analysis indicated that 10 pharmaceuticals and personal care products (PPCPs) were present at the downstream site, some at sufficiently great concentrations that may present a risk to aquatic organisms. With continuous exposure to a diverse number of stressors including high nutrient and ammonia levels, the presence of a variety of PPCPs and other contaminants, Wascana Creek should be considered as an ecosystem at risk.

Remodeling of Arctic char (Salvelinus alpinus) lipidome under a stimulated scenario of Arctic warming

Arctic warming associated with global climate change poses a significant threat to populations of wildlife in the Arctic. Since lipids play a vital role in adaptation of organisms to variations in temperature, high-resolution mass-spectrometry-based lipidomics can provide insights into adaptive responses of organisms to a warmer environment in the Arctic and help to illustrate potential novel roles of lipids in the process of thermal adaption. In this study, we studied an ecologically and economically important species-Arctic char (Salvelinus alpinus)-with a detailed multi-tissue analysis of the lipidome in response to chronic shifts in temperature using a validated lipidomics workflow. In addition, dynamic alterations in the hepatic lipidome during the time course of shifts in temperature were also characterized. Our results showed that early life stages of Arctic char were more susceptible to variations in temperature. One-year-old Arctic char responded to chronic increases in temperature with coordinated regulation of lipids, including headgroup-specific remodeling of acyl chains in glycerophospholipids (GP) and extensive alterations in composition of lipids in membranes, such as less lyso-GPs, and more ether-GPs and sphingomyelin. Glycerolipids (e.g., triacylglycerol, TG) also participated in adaptive responses of the lipidome of Arctic char. Eight-week-old Arctic char exhibited rapid adaptive alterations of the hepatic lipidome to stepwise decreases in temperature while showing blunted responses to gradual increases in temperature, implying an inability to adapt rapidly to warmer environments. Three common phosphatidylethanolamines (PEs) (PE 36:6|PE 16:1_20:5, PE 38:7|PE 16:1_22:6, and PE 40:7|PE 18:1_22:6) were finally identified as candidate lipid biomarkers for temperature shifts via machine learning approach. Overall, this work provides additional information to a better understanding of underlying regulatory mechanisms of the lipidome of Arctic organisms in the face of near-future warming.

Responses of juvenile fathead minnow (Pimephales promelas) gut microbiome to a chronic dietary exposure of benzo[a]pyrene

The microbiome has been described as an additional host "organ" with well-established beneficial roles. However, the effects of exposures to chemicals on both structure and function of the gut microbiome of fishes are understudied. To determine effects of benzo[a]pyrene (BaP), a model persistent organic pollutant, on structural shifts of gut microbiome in juvenile fathead minnows (Pimephales promelas), fish were exposed ad libitum in the diet to concentrations of 1, 10, 100, or 1000 μg BaP g^-1 food, in addition to a vehicle control, for two weeks. To determine the link between exposure to BaP and changes in the microbial community, concentrations of metabolites of BaP were measured in fish bile and 16S rRNA amplicon sequencing was used to evaluate the microbiome. Exposure to BaP only reduced alpha-diversity at the greatest exposure concentrations. However, it did alter community composition assessed as differential abundance of taxa and reduced network complexity of the microbial community in all exposure groups. Results presented here illustrate that environmentally-relevant concentrations of BaP can alter the diversity of the gut microbiome and community network connectivity.

Effects of the brominated flame retardant, TBCO, on development of zebrafish (Danio rerio) embryos

Brominated flame retardants (BFRs) can enter aquatic environments where they can have adverse effects on organisms. The BFR, 1,2,5,6-Tetrabromocyclooctane (TBCO), has been introduced as a potential replacement for the major use BRF, Hexabromocyclododecane (HBCD). However, little is known about effects of TBCO on aquatic organisms. Using zebrafish (Danio rerio) as a model species, objectives of this study were to determine whether TBCO has adverse effects on early life-stages and to investigate the molecular and biochemical mechanisms of any effects on development. Exposure to TBCO caused a concentration dependant increase in mortality, decrease in heart rate, and increase in incidences of spinal curvature and uninflated swim bladders. Neither peroxidation of lipids or mRNA abundances of genes important for the response to oxidative stress were greater in embryos exposed to TBCO suggesting effects were not caused by oxidative stress. The mRNA abundance of cytochrome p4501a was not greater in embryos exposed to TBCO suggesting that effects were not caused by activation of the aryl hydrocarbon receptor. Finally, mRNA abundances of genes important for development and inflation of the swim bladder were not affected by TBCO. Overall, TBCO causes adverse effects on early life-stages of zebrafish, but mechanisms of effects require further investigation.

Ractopamine and Other Growth-Promoting Compounds in Beef Cattle Operations: Fate and Transport in Feedlot Pens and Adjacent Environments

The current study represents a comprehensive investigation of the occurrence and fates of trenbolone acetate (TBA) and metabolites 17α-trenbolone (17α-TBOH), 17β-TBOH, and trendione (TBO); melengesterol acetate (MGA); and the less commonly studied β-andrenergic agonist ractopamine (RAC) in two 8 month cattle feeding trials and simulated rainfall runoff experiments. Cattle were administered TBA, MGA, or RAC, and their residues were measured in fresh feces, pen floor material, and simulated rainfall runoff from pen floor surfaces and manure-amended pasture. Concentrations of RAC ranged from 3600 ng g^-1, dry weight (dw), in pen floor to 58 000 ng g^-1 in fresh feces and were, on average, observed at 3-4 orders of magnitude greater than those of TBA and MGA. RAC persisted in pen floors (manure t_1/2 = 18-49 days), and contamination of adjacent sites was observed, likely via transport of windblown particulates. Concentrations in runoff water from pen floors extrapolated to larger-scale commercial feedlots revealed that a single rainfall event could result in mobilization of gram quantities of RAC. This is the first report of RAC occurrence and fate in cattle feedlot environments, and will help understand the risks posed by this chemical and inform appropriate manure-management practices.

Dissipation, Fate, and Toxicity of Crop Protection Chemical Safeners in Aquatic Environments

Safeners are a group of chemicals applied with herbicides to protect crop plants from potential adverse effects of agricultural products used to kill weeds in monocotyledonous crops. Various routes of dissipation of safeners from their point of applications were evaluated. Despite the large numbers of safeners (over 18) commercially available and the relatively large quantities (~2 × 10⁶ kg/year) used, there is little information on their mobility and fate in the environment and occurrence in various environmental matrices. The only class of safeners for which a significant amount of information is available is dichloroacetamide safeners, which have been observed in some rivers in the USA at concentrations ranging from 42 to 190 ng/L. Given this gap in the literature, there is a clear need to determine the occurrence, fate, and bioavailability of other classes of safeners. Furthermore, since safeners are typically used in commercial formulations, it is useful to study them in relation to their corresponding herbicides. Common routes of dissipation for herbicides and applied safeners are surface run off (erosion), hydrolysis, photolysis, sorption, leaching, volatilization, and microbial degradation. Toxic potencies of safeners vary among organisms and safener compounds, ranging from as low as the LC₅₀ for fish (Oncorhynchus mykiss) for isoxadifen-ethyl, which was 0.34 mg/L, to as high as the LC₅₀ for Daphnia magna from dichlormid, which was 161 mg/L. Solubilities and octanol-water partition coefficients seem to be the principal driving force in understanding safener mobilities. This paper provides an up-to-date literature review regarding the occurrence, behaviour, and toxic potency of herbicide safeners and identifies important knowledge gaps in our understanding of these compounds and the potential risks posed to potentially impacted ecosystems.

Effects of the husky oil spill on gut microbiota of native fishes in the North Saskatchewan River, Canada

In July 2016, a Husky Energy pipeline spilled 225,000 L of diluted heavy crude oil, with a portion of the oil entering the North Saskatchewan River near Maidstone, SK, Canada. This event provided a unique opportunity to assess potential effects of a crude oil constituent (namely polycyclic aromatic hydrocarbons, PAHs) on a possible sensitive indicator of freshwater ecosystem health, the gut microbiota of native fishes. In summer 2017, goldeye (Hiodon alosoides), walleye (Sander vitreus), northern pike (Esox lucius), and shorthead redhorse (Moxostoma macrolepidotum) were collected at six locations upstream and downstream of the spill. Muscle and bile were collected from individual fish for quantification of PAHs and intestinal contents were collected for characterization of the microbial community of the gut. Results suggested that host species is a significant determinant of gut microbiota, with significant differences among the species across sites. Concentrations of PAHs in dorsal muscle were significantly correlated with gut community compositions of walleye, but not of the other fishes. Concentrations of PAHs in muscle were also correlated with abundances of several families of bacteria among fishes. This study represents one of the first to investigate the response of the gut microbiome of wild fishes to chemical stressors.

In vitro-in vivo and cross-life stage extrapolation of uptake and biotransformation of benzo[a]pyrene in the fathead minnow (Pimephales promelas)

Understanding internal dose metrics is integral to adequately assess effects environmental contaminants might have on aquatic wildlife, including fish. In silico toxicokinetic (TK) models are a leading approach for quantifying internal exposure metrics for fishes; however, they often do not adequately consider chemicals that are actively biotransformed and have not been validated against early-life stages (ELS) that are often considered the most sensitive to the exposure to contaminants. To address these uncertainties, TK models were parameterized for the rapidly biotransformed chemical benzo[a]pyrene (B[a]P) in embryo-larval and adult life stages of fathead minnows. Biotransformation of B[a]P was determined through measurements of in vitro clearance. Using in vitro-in vivo extrapolation, in vitro clearance was integrated into a multi-compartment TK model for adult fish and a one-compartment model for ELS. Model predictions were validated using measurements of B[a]P metabolites from in vivo flow-through exposures to graded concentrations of water-borne B[a]P. Significantly greater amounts of B[a]P metabolites were observed with exposure to greater concentrations of parent compound in both life stages. However, when assessing biotransformation capacity, no differences in phase I or phase II biotransformation were observed with greater exposures to B[a]P. Results of modelling suggested that biotransformation of B[a]P can be successfully implemented into in silico models to accurately predict life stage-specific abundances of B[a]P metabolites in either whole-body larvae or the bile of adult fish. Models developed increase the scope of applications in which TK models can be used to support environmental risk assessments.

Concentrations of Metals in Fishes from the Athabasca and Slave Rivers of Northern Canada

There is growing concern about possible effects of exploitation of the Alberta Oil Sands on the ambient environment, including possible effects on populations of fishes in the Athabasca River and farther downstream in Lake Athabasca and the Slave River. In the present study, concentrations of metals in dorsal muscle tissue of 5 fish species-goldeye, northern pike, walleye, whitefish, and burbot-from the Slave, Peace, and Athabasca Rivers were quantified. A suite of 25 metals including As, Hg, Se, Tl, and V was analyzed. Most metals exhibited no significant variations in concentration among locations. Concentrations of 5 metals, As, Hg, Se, Tl, and V, revealed significant variations among locations and were of sufficient magnitude to be of interest. Concentrations of Hg did not vary significantly among locations; however, because it was detected at concentrations of concern and the use of the selected fishes was a local source of food for humans and pets, it was of interest. Concentrations of As, Se, Tl, and V in dorsal muscle of certain fishes in the farthest downstream sites on the Slave River were greater than those in the same tissues and species in the farther upstream sites on the Peace and Athabasca Rivers. This phenomenon was most prevalent with Tl and to a lesser extent with As and Se. Nevertheless, concentrations were not of concern for the health of human consumers. Although metals did not appear to be increased in fish in the Alberta Oil Sands region in the present study, further research is needed to understand the potential impacts. Environ Toxicol Chem 2020;39:2180-2195. © 2020 SETAC.

Mechanisms of pH-Dependent Uptake of Ionizable Organic Chemicals by Fish from Oil Sands Process-Affected Water (OSPW)

Uptake and effects of ionizable organic chemicals (IOCs) that are weak acids in aqueous solution by fish can differ as a function of pH. While the pH-dependent behavior of select IOCs is well-understood, complex mixtures of IOCs, e.g., from oil sands process-affected water (OSPW), have not yet been studied systematically. Here, we established an in vitro screening method using the rainbow trout gill cell line, RTgill-W1, to investigate pH-dependent cytotoxicity and permeation of IOCs across cultured epithelia using ultra-high-performance liquid chromatography with high-resolution mass spectrometry (UPLC-HRMS). The assay was benchmarked using model chemicals and technical mixtures, and then used to characterize fractions and reconstituted extracts of field-collected OSPW. Significant pH-dependent cytotoxicity of individual IOCs, acidic fractions, and reconstituted extracts of OSPW was observed. In vitro data were in good agreement with data from a 96 h in vivo exposure experiment with juvenile rainbow trout. Permeation of some IOCs from OSPW was mediated by active transport, as revealed by studies in which inhibitors of these active transport mechanisms were applied. We conclude that the RTgill-W1 in vitro assay is useful for the screening of pH-dependent uptake of IOCs in fish, and has applications for in vitro-in vivo extrapolation, and prioritization of chemicals in nontarget screenings.

Metals and PFAS in stormwater and surface runoff in a semi-arid Canadian city subject to large variations in temperature among seasons

Because compounds accumulate through dry periods and enter aquatic systems in just a few seasonal events such as snowmelt and summer storms, surface waters in semi-arid, cold regions, such as the Canadian Prairies, are particularly vulnerable to loading of contaminant from runoff events from surfaces. This study assessed concentrations of metals and selected trace organics entering a river via surface runoff from an urban region and how these semi-arid regions with large seasonal variations in temperature might differ from more temperate regions. Selected potentially harmful elements (PHEs) including, Mn with Cr, Cu, Zn, Ba and U all exceeded guideline discharge values set by the Canadian Council of the Ministers of the Environment (CCME) by as much as 16-fold. Variation among discharges during spring, summer and winter was observed. For example, across the whole city, an estimated 6 kg of zinc was discharged in a spring storm, 36 kg in a summer storm and 17 tonnes in snowmelt. The mass of Zn discharged is similar to the annual loading estimated for Stockholm, Sweden, but in Saskatoon, Saskatchewan, Canada, the bulk of runoff was during snowmelt. The mean sum of poly- and per-fluoroalkyl substances (PFAS) in stormwater was 9.0 ng L^-1, which is consistent with concentrations observed in other Canadian cities (6.5-16 ng L^-1). These concentrations of PFAS are likely due to dispersed sources and orders of magnitude less than thresholds for toxicity to fish and aquatic invertebrates.

Toxicokinetics of Brominated Azo Dyes in the Early Life Stages of Zebrafish (Danio rerio) Is Prone to Aromatic Substituent Changes

Brominated azo dyes (BADs) have been identified as predominant indoor brominated pollutants in daycare dust; thus, their potential health risk to children is of concern. However, the toxicities of BADs remain elusive. In this study, the toxicokinetics of two predominant BADs, Disperse Blue 373 (DB373) and Disperse Violet 93 (DV93), and their suspect metabolite 2-bromo-4,6-dinitroaniline (BDNA) was investigated in embryos of zebrafish (Danio rerio). The bioconcentration factor of DV93 at 120 hpf is 6.2-fold lower than that of DB373. The nontarget analysis revealed distinct metabolism routes between DB373 and DV93 by reducing nitro groups to nitroso (DB373) or amine (DV93), despite their similar structures. NAD(P)H quinone oxidoreductase 1 (NQO1) and pyruvate dehydrogenase were predicted as the enzymes responsible for the reduction of DB373 and DV93 by correlating time courses of the metabolites and enzyme development. Further in vitro recombinant enzyme and in vivo inhibition results validated NQO1 as the enzyme specifically reducing DB373, but not DV93. Global proteome profiling revealed that the expression levels of proteins from the "apoptosis-induced DNA fragmentation" pathway were significantly upregulated by all three BADs, supporting the bioactivation of BADs to mutagenic aromatic amines. This study discovered the bioactivation of BADs via distinct eukaryotic enzymes, implying their potential health risks.

Extraction of Lipid-Soluble Marine Biotoxins

A recent extensive outbreak of toxic shellfish poisoning (TSP) in New Zealand, with at least 4 types of toxicities present, required the development of a new method for detecting lipid-soluble marine biotoxins. The complexity of studying this outbreak, requiring large sample numbers, dictated the development of a robust and safe method for extracting lipid-soluble toxins. The new method is based on extraction of lipophilic compounds with acetone followed by partitioning into dichloromethane. The dichloromethane extract is evaporated to constant weight and suspended in a detergent–saline solution for use in a mouse bioassay. The new method produces an extract of superior quality, is quicker and more sensitive compared with extraction methods currently used.

Vanadium and thallium exhibit biodilution in a northern river food web

Trophic transfer of contaminants dictates concentrations and potential toxic effects in top predators, yet biomagnification behaviour of many trace elements is poorly understood. We examined concentrations of vanadium and thallium, two globally-distributed and anthropogenically-enriched elements, in a food web of the Slave River, Northwest Territories, Canada. We found that tissue concentrations of both elements declined with increasing trophic position as measured by δ¹⁵N. Slopes of log [element] versus δ¹⁵N regressions were both negative, with a steeper slope for V (-0.369) compared with Tl (-0.099). These slopes correspond to declines of 94% with each step in the food chain for V and 54% with each step in the food chain for Tl. This biodilution behaviour for both elements meant that concentrations in fish were well below values considered to be of concern for the health of fish-eating consumers. Further study of these elements in food webs is needed to allow a fuller understanding of biomagnification patterns across a range of species and systems.

Abundances and concentrations of brominated azo dyes detected in indoor dust

Dust samples were collected from four indoor environments, including childcare facilities, houses, hair salons, and a research facility from the USA and were analyzed for brominated compounds using full scan liquid chromatography high-resolution mass spectrometry. A total of 240 brominated compounds were detected in these dust samples, and elemental formulas were predicted for 120 more abundant ions. In addition to commonly detected brominated flame retardants (BFRs), nitrogen-containing brominated azo dyes (BADs) were among the most frequently detected and abundant. Specifically, greater abundances of BADs were detected in indoor dusts from daycares and salons compared to houses and the research facility. Using authentic standards, a quantitative method was established for two BADs (DB373: Disperse Blue 373 and DV93: Disperse Violet 93) and 2-bromo-4,6-dinitroaniline, a commonly used precursor in azo dye production, in indoor dust. Generally, greater concentrations of DB373 (≤3850 ng/g) and DV93 (≤1190 ng/g) were observed in indoor dust from daycares highlighting children as a susceptible population to potential health risk from exposure to BADs. These data are important because, to date, targeted analysis of brominated compounds in indoor environments has focused mainly on BFRs and appears to underestimate the total amount of brominated compounds.

Combining High-Throughput Sequencing of sedaDNA and Traditional Paleolimnological Techniques To Infer Historical Trends in Cyanobacterial Communities

Freshwaters worldwide are under increasing pressure from anthropogenic activities and changing climate. Unfortunately, many inland waters lack sufficient long-term monitoring to assess environmental trends. Analysis of sedimentary ancient DNA ( sedaDNA) is emerging as a means to reconstruct the past occurrence of microbial communities of inland waters. The purpose of this study was to assess a combination of high-throughput sequencing (16S rRNA) of sedaDNA and traditional paleolimnological analyses to explore multidecadal relationships among cyanobacterial community composition, the potential for cyanotoxin production, and paleoenvironmental proxies. DNA was extracted from two sediment cores collected from a northern Canadian Great Plains reservoir. Diversity indices illustrated significant community-level changes since reservoir formation. Furthermore, higher relative abundances in more recent years were observed for potentially toxic cyanobacterial genera including Dolichospermum. Correlation-based network analysis revealed this trend significantly and positively correlated to abundances of the microcystin synthetase gene ( mcyA) and other paleoproxies (nutrients, pigments, stanols, sterols, and certain diatom species), demonstrating synchrony between molecular and more standard proxies. These findings demonstrate a novel approach to infer long-term dynamics of cyanobacterial diversity in inland waters and highlight the power of high-throughput sequencing to reconstruct trends in environmental quality and inform lake and reservoir management and monitoring program design.

Spatial and temporal trends in poly- and per-fluorinated compounds in the Laurentian Great Lakes Erie, Ontario and St. Clair

The temporal and spatial trends in sediment of 22 poly- and perfluorinated (PFAS) compounds were investigated in the southern Great Lakes Erie and Ontario as well as Lake St. Clair. Surface concentrations measured by Ponar grab samples indicated a trend for greater concentrations near to urban sites. Mean concentrations ∑₂₂PFAS were 15.6, 18.2 and 19 ng g^-1 dm for Lakes St. Clair, Erie and Ontario, respectively. Perfluoro-n-butanoic acid (PFBA) and Perfluoro-n-hexanoic acid (PFHxA) were frequently determined in surface sediment and upper core samples indicating a shift in use patterns. Where PFBA was identified it was at relatively great concentrations typically >10 ng g^-1 dm. However as PFBA and PFHxA are less likely to bind to sediment they may be indicative of pore water concentrations Sedimentation rates between Lake Erie and Lake Ontario differ greatly with greater rates observed in Lake Erie. In Lake Ontario, in general concentrations of PFAS observed in core samples closely follow the increase in use along with an observable change due to regulation implementation in the 1970s for water protection. However some of the more water soluble PFAS were observed in deeper core layers than the time of production could account for, indicating potential diffusion within the sediment. Given the greater sedimentation rates in Lake Erie, it was hoped to observe in greater resolution changes since the mid-1990s. However, though some decrease was observed at some locations the results are not clear. Many cores in Lake Erie had clearly observable gas voids, indicative of gas ebullition activity due to biogenic production, there were also observable mussel beds that could indicate mixing by bioturbation of core layers.

Open-water and under-ice seasonal variations in trace element content and physicochemical associations in fluvial bed sediment

Across the circumpolar world, intensive anthropogenic activities in the southern reaches of many large, northward-flowing rivers can cause sediment contamination in the downstream depositional environment. The influence of ice cover on concentrations of inorganic contaminants in bed sediment (i.e., sediment quality) is unknown in these rivers, where winter is the dominant season. A geomorphic response unit approach was used to select hydraulically diverse sampling sites across a northern test-case system, the Slave River and delta (Northwest Territories, Canada). Surface sediment samples (top 1 cm) were collected from 6 predefined geomorphic response units (12 sites) to assess the relationships between bed sediment physicochemistry (particle size distribution and total organic carbon content) and trace element content (mercury and 18 other trace elements) during open-water conditions. A subset of sites was resampled under-ice to assess the influence of season on these relationships and on total trace element content. Concentrations of the majority of trace elements were strongly correlated with percent fines and proxies for grain size (aluminum and iron), with similar trace element grain size/grain size proxy relationships between seasons. However, finer materials were deposited under ice with associated increases in sediment total organic carbon content and the concentrations of most trace elements investigated. The geomorphic response unit approach was effective at identifying diverse hydrological environments for sampling prior to field operations. Our data demonstrate the need for under-ice sampling to confirm year-round consistency in trace element-geochemical relationships in fluvial systems and to define the upper extremes of these relationships. Whether contaminated or not, under-ice bed sediment can represent a "worst-case" scenario in terms of trace element concentrations and exposure for sediment-associated organisms in northern fluvial systems. Environ Toxicol Chem 2017;36:2916-2924. © 2017 SETAC.

Hydroxylated 2-Ethylhexyl tetrabromobenzoate isomers in house dust and their agonistic potencies with several nuclear receptors

In the current study, by combining ultra-high resolution (UHR) MS¹ spectra, MS² spectra, and derivatization, three hydroxylated isomers of 2-ethylhexyl tetrabromobenzoate (OH-TBB) were identified in Firemaster^® 550 and BZ-54 technical products. Also, a new LC-UHRMS method, using atmospheric pressure chemical ionization (APCI), was developed for simultaneous analysis of OH-TBB, TBB, hydroxylated bis(2-ethylhexyl)-tetrabromophthalate (OH-TBPH) and TBPH in 23 samples of dust collected from houses in Saskatoon, SK, Canada. OH-TBBs were detected in 91% of samples, with a geometric mean concentration of 0.21 ng/g, which was slightly less than those of OH-TBPH (0.35 ng/g). TBB was detected in 100% of samples of dust with a geometric mean concentration of 992 ng/g. Significant (p < 0.001) log-linear relationships between concentrations of OH-TBBs, TBB, or OH-TBPHs and TBPH in dust support the hypothesis of a common source of these compounds. OH-TBBs were found to be strong agonists of peroxisome proliferator-activated receptor gamma (PPARγ) and weaker agonists of the estrogen receptor (ER), but no agonistic potencies was observed with the androgen receptor (AR). Occurrence of OH-TBBs in technical products and house dust, together with their relatively strong PPARγ potencies, indicated their potential risk to health of humans.

Identification of Chemicals that Cause Oxidative Stress in Oil Sands Process-Affected Water

Oil sands process-affected water (OSPW) has been reported to cause oxidative stress in organisms, yet the causative agents remain unknown. In this study, a high-throughput in vitro Nrf2 reporter system was used, to determine chemicals in OSPW that cause oxidative stress. Five fractions, with increasing polarity, of the dissolved organic phase of OSPW were generated by use of solid phase extraction cartridges. The greatest response of Nrf2 was elicited by F2 (2.7 ± 0.1-fold), consistent with greater hydroperoxidation of lipids in embryos of Japanese medaka (Oryzias latipes) exposed to F2. Classic naphthenic acids were mainly eluted in F1, and should not be causative chemicals. When F2 was fractionated into 60 subfractions by use of HPLC, significant activation of Nrf2 was observed in three grouped fractions: F2.8 (1.30 ± 0.01-fold), F2.16 (1.34 ± 0.05-fold), and F2.25 (1.28 ± 0.15-fold). 54 compounds were predicted to be potential chemicals causing Nrf2 response, predominated by SO₃⁺ and O₃⁺ species. By use of high-resolution MS² spectra, these SO₃⁺ and O₃⁺ species were identified as hydroxylated aldehydes. This study demonstrated that polyoxygenated chemicals, rather than classic NAs, were the major chemicals responsible for oxidative stress in the aqueous phase of OSPW.

Stable sulfur isotopes identify habitat-specific foraging and mercury exposure in a highly mobile fish community

Tracking the uptake and transfer of toxic chemicals, such as mercury (Hg), in aquatic systems is challenging when many top predators are highly mobile and may therefore be exposed to chemicals in areas other than their location of capture, confounding interpretation of bioaccumulation trends. Here we show how the application of a less commonly used ecological tracer, stable sulfur isotope ratios (³⁴S/³²S, or δ³⁴S), in a large river-delta-lake complex in northern Canada allows differentiation of resident from migrant fishes, beyond what was possible with more conventional ¹³C/¹²C and ¹⁵N/¹⁴N measurements. Though all large fishes (n=105) were captured in the river, the majority (76%) had δ³⁴S values that were indicative of the fish having been reared in the lake. These migrant fishes were connected to a food chain with greater Hg trophic magnification relative to the resident fish of the river and delta. Yet, despite a shallower overall trophic magnification slope, large river-resident fish had higher Hg concentrations owing to a greater biomagnification of Hg between small and large fishes. These findings reveal how S isotopes can trace fish feeding habitats in large freshwater systems and better account for fish movement in complex landscapes with differential exposure pathways and conditions.

Bridging science and traditional knowledge to assess cumulative impacts of stressors on ecosystem health

Cumulative environmental impacts driven by anthropogenic stressors lead to disproportionate effects on indigenous communities that are reliant on land and water resources. Understanding and counteracting these effects requires knowledge from multiple sources. Yet the combined use of Traditional Knowledge (TK) and Scientific Knowledge (SK) has both technical and philosophical hurdles to overcome, and suffers from inherently imbalanced power dynamics that can disfavour the very communities it intends to benefit. In this article, we present a 'two-eyed seeing' approach for co-producing and blending knowledge about ecosystem health by using an adapted Bayesian Belief Network for the Slave River and Delta region in Canada's Northwest Territories. We highlight how bridging TK and SK with a combination of field data, interview transcripts, existing models, and expert judgement can address key questions about ecosystem health when considerable uncertainty exists. SK indicators (e.g., bird counts, mercury in fish, water depth) were graded as moderate, whereas TK indicators (e.g., bird usage, fish aesthetics, changes to water flow) were graded as being poor in comparison to the past. SK indicators were predominantly spatial (i.e., comparing to other locations) while the TK indicators were predominantly temporal (i.e., comparing across time). After being populated by 16 experts (local harvesters, Elders, governmental representatives, and scientists) using both TK and SK, the model output reported low probabilities that the social-ecological system is healthy as it used to be. We argue that it is novel and important to bridge TK and SK to address the challenges of environmental change such as the cumulative impacts of multiple stressors on ecosystems and the services they provide. This study presents a critical social-ecological tool for widening the evidence-base to a more holistic understanding of the system dynamics of multiple environmental stressors in ecosystems and for developing more effective knowledge-inclusive partnerships between indigenous communities, researchers and policy decision-makers. This represents new transformational empirical insights into how wider knowledge discourses can contribute to more effective adaptive co-management governance practices and solutions for the resilience and sustainability of ecosystems in Northern Canada and other parts of the world with strong indigenous land tenure.

Potential health risks posed by polycyclic aromatic hydrocarbons in muscle tissues of fishes from the Athabasca and Slave Rivers, Canada

Polycyclic aromatic hydrocarbons (PAHs) are released to the environment from oil sands operations and from natural sources in Alberta, Canada. Concentrations of 16 USEPA priority PAHs were measured in tissues of fishes collected from three locations on the Athabasca River in Alberta and two downstream locations on the Slave River in the Northwest Territories, Canada. A total of 425 individual fish were collected including 89 goldeye (Hiodon alosoides), 93 whitefish (Coregonus clupeaformis), 104 northern pike/jackfish (Esox lucius), 96 walleye (Sander vitreus) and 43 burbot/loche mariah/mariah (Lota lota). Fish were sampled during the summer and fall of 2011 and spring of 2012. Dorsal muscle of fishes from upstream reaches of the Athabasca River, close to oil sands extraction and upgrading activities, contained greater concentrations of individual PAHs than concentrations in muscle of fishes from further downstream in the Slave River. Concentrations of the sum of USEPA indicator PAHs (∑PAHs) in fishes collected in the vicinity of Fort McKay, closest to oil sands activities, varied among seasons with average concentrations ranging from 11 (burbot, summer) to 1.2 × 10² ng/g, wm (burbot, spring) with a mean of 48 ng/g, wm. Concentrations of ∑PAHs in fishes collected in the vicinity of Fort Resolution, the location most distant from oil sands activities, also varied among species and seasons, with average concentrations ranging from 4.3 (whitefish, summer) to 33 ng/g, wm (goldeye, summer) with a mean of 13 ng/g, wm. Significant differences in concentrations of ∑PAHs in muscle were observed within goldeye, jackfish, walleye and whitefish among sites. Health risks posed by PAHs to humans were assessed probabilistically using a B[a]P equivalents approach (B[a]P_eq). The average lifetime risk of additional cancers for humans who consumed fish was deemed to be within an 'acceptable' range of risk (i.e., less than 10^-6).

Mutagenic Azo Dyes, Rather Than Flame Retardants, Are the Predominant Brominated Compounds in House Dust

Characterization of toxicological profiles by use of traditional targeted strategies might underestimate the risk of environmental mixtures. Unbiased identification of prioritized compounds provides a promising strategy for meeting regulatory needs. In this study, untargeted screening of brominated compounds in house dust was conducted using a data-independent precursor isolation and characteristic fragment (DIPIC-Frag) approach, which used data-independent acquisition (DIA) and a chemometric strategy to detect peaks and align precursor ions. A total of 1008 brominated compound peaks were identified in 23 house dust samples. Precursor ions and formulas were identified for 738 (73%) of the brominated compounds. A correlation matrix was used to cluster brominated compounds; three large groups were found for the 140 high-abundance brominated compounds, and only 24 (17%) of these compounds were previously known flame retardants. The predominant class of unknown brominated compounds was predicted to consist of nitrogen-containing compounds. Following further validation by authentic standards, these compounds (56%) were determined to be novel brominated azo dyes. The mutagenicity of one major component was investigated, and mutagenicity was observed at environmentally relevant concentrations. Results of this study demonstrated the existence of numerous unknown brominated compounds in house dust, with mutagenic azo dyes unexpectedly being identified as the predominant compounds.

Effect of pyrolysis temperature on potential toxicity of biochar if applied to the environment

Biochars have increasingly been used as adsorbents for organic and inorganic contaminants in soils. However, during the carbonization process of pyrolysis, contaminants, including polycyclic aromatic hydrocarbons (PAHs) and polychlorinated dioxins and furans (PCDD/DF) can be generated. In this study, biochars made from sawdust, were prepared at various temperatures ranging from 250 to 700 °C. The Microtox^® and rat hepatoma cell line H4IIE-luc assays were used to characterize the general toxic and effects, mediated through the aryl hydrocarbon receptor (AhR), or dioxin-like potencies of organic extracts of biochars. The greatest total concentrations of PAHs (8.6 × 10² μg kg^-1) and PCDD/DF (6.1 × 10² pg g^-1) were found in biochar generated at 400 °C and 300 °C, respectively. Results of the H4IIE-luc assay, which gives total concentrations of 2,3,7,8-TCDD equivalents (TEQ_H4IIE-luc), indicated that total potencies of aryl hydrocarbon receptor (AhR) agonists were in decreasing order: 300 °C > 250 °C > 400 °C > 500 °C > 700 °C. The 2,3,7,8-tetrachlorodibenzo-p-dioxin equivalents (TEQ_chem) calculated as the sum of products of 16 PAHs and 17 PCDD/DF congers multiplied by their respective relative potencies (RePs) was less than that of TEQ_H4IIE-luc determined by use of the bioanalytical method, with the H4IIE-luc assay, which measures the total dioxin-like potency of a mixtures. The ratio of TEQ_chem/TEQ_H4IIE-luc was in the range of 0.7%-3.8%. Thus, a rather small proportion of the AhR-mediated potencies extracted from biochars were identified by instrumental analyses. Results of the Microtox test showed similar tendencies as those of the H4IIE-luc test, and a linear correlation between EC50 of Microtox test and EC20 of H4IIE-luc test was found. The results demonstrated that biochars produced at higher pyrolysis temperatures (>400 °C) were less toxic and had lower potencies of AhR-mediated effects, which may be more suitable for soil application.

Untargeted Screening and Distribution of Organo-Iodine Compounds in Sediments from Lake Michigan and the Arctic Ocean

The majority of halogenated organic compounds present in the environment remain unidentified. To address this data gap, we recently developed an untargeted method (data-independent precursor isolation and characteristic fragment; DIPIC-Frag) for identification of unknown organo-bromine compounds. In this study, the method was adapted to enable untargeted screening of natural and synthetic organo-iodine compounds (NSOICs) in sediments. A total of 4,238 NSOIC peaks were detected in sediments from Lake Michigan. Precursor ions and formulas were determined for 2,991 (71%) of the NSOIC peaks. These compounds exhibited variations in abundances (<10(3) to ∼10(7)), m/z values (206.9304-996.9474), retention times (1.0-29.7 min), and number of iodine atoms (1-4). Hierarchical cluster analysis showed that sediments in closer proximity exhibited similar profiles of NSOICs. NSOICs were screened in 10 samples of sediment from the Arctic Ocean to compare the profiles of NSOICs between freshwater and marine sediments. A total of 3,168 NSOIC peaks were detected, and profiles of NSOICs in marine sediments were clearly distinct from Lake Michigan. The coexistence of brominated and iodinated analogues indicated that some NSOICs are of natural origin. Different ratios of abundances of iodinated compounds to brominated analogues were observed and proposed as a marker to distinguish sources of NSOICs.

Combined Transcriptomic and Proteomic Approach to Identify Toxicity Pathways in Early Life Stages of Japanese Medaka (Oryzias latipes) Exposed to 1,2,5,6-Tetrabromocyclooctane (TBCO)

Currently, the novel brominated flame retardant 1,2,5,6-tetrabromocyclooctane (TBCO) is considered a potential replacement for hexabromocyclododecane (HBCD). Therefore, use of TBCO could increase in the near future. To assess potential toxicological risks to aquatic organisms, embryos of Japanese medaka (Oryzias latipes) were exposed to 10, 100, or 1000 μg/L TBCO from 2 h postfertilization until 1 day post-hatch. TBCO accumulated in embryos in the order of 0.43-1.3 × 10(4)-fold, and the rate constant of accumulation was 1.7-1.8 per day. The number of days to hatch and the hatching success of embryos exposed to the medium and the greatest concentrations of TBCO were impaired. Responses of the transcriptome (RNA-seq) and proteome were characterized in embryos exposed to 100 μg/L TBCO because this was the least concentration of TBCO that caused an effect on hatching. Consistent with effects on hatching, proteins whose abundances were reduced by exposure to TBCO were enriched in embryo development and hatching pathways. Also, on the basis of the responses of transcriptome and proteome, it was predicted that TBCO might impair vision and contraction of cardiac muscle, respectively, and these effects were confirmed by targeted bioassays. This study provided a comprehensive understanding of effects of TBCO on medaka at early life stages and illustrated the power of "omics" to explain and predict phenotypic responses to chemicals.

Peroxisome Proliferator-Activated Receptor γ is a Sensitive Target for Oil Sands Process-Affected Water: Effects on Adipogenesis and Identification of Ligands

Identification of toxic components of complex mixtures is a challenge. Here, oil sands process-affected water (OSPW) was used as a case study to identify those toxic components with a known protein target. Organic chemicals in OSPW exhibited dose-dependent activation of peroxisome proliferator-activated receptor γ (PPARγ) at concentrations less than those currently in the environment (0.025× equivalent of full-strength OSPW), by use of a luciferase reporter gene assay. Activation of PPARγ-mediated adipogenesis by OSPW was confirmed in 3T3L1 preadipocytes, as evidenced by accumulation of lipids and up-regulation of AP2, LPL, and PPARγ gene expression after exposure to polar fractions of OSPW. Unexpectedly, the nonpolar fractions of OSPW inhibited differentiation of preadipocytes via activation of the Wnt signaling pathway. Organic chemicals in OSPW that were ligands of PPARγ were identified by use of a pull-down system combined with untargeted chemical analysis (PUCA), with a recombinant PPARγ protein. Thirty ligands of PPARγ were identified by use of the PUCA assay. High resolution MS(1) and MS(2) spectra were combined to predict the formulas or structures of a subset of ligands, and polyoxygenated or heteroatomic chemicals, especially hydroxylated carboxylic/sulfonic acids, were the major ligands of PPARγ.