The effects of dimethylated and alkylated polycyclic aromatic hydrocarbons on the embryonic development of the Japanese medaka

Predicted no-effect concentration for eight PAHs and their ecological risks in seven major river systems of China

The initial step in the assessment of the ecological risk of pollutants is to determine the predicted no-effect concentration (PNEC). However, ecological risk assessments of eight carcinogenic polycyclic aromatic hydrocarbons (PAHs), including dimethylbenz[a]anthracene (DMBA), methylcholanthrene (MCA), benzo(a)anthracene (BaA), chrysene (CHR), benzo(b)fluoranthene (BbF), benzo(k)fluoranthene (BkF), benzo(a)pyrene (BaP), and dibenzo(a,h)anthracene (DBA), are rarely conducted due to the lack of their PNECs based on test data. In this study, quantitative structure-activity relationship (QSAR) models and interspecies correlation estimation (ICE) models were combined to predict the acute toxicity of these eight target PHAs. A Kolmogorov-Smirnov analysis for species sensitivity distributions (SSDs) of native and all species was conducted. There was no significant difference between the predictions for native Chinese species and the predictions for all species by the QSAR-ICE models. In addition, the feasibility of the QSAR-ICE models was demonstrated by comparing the SSD curves constructed by measured toxicity data of BaP and those predicted by the QSAR-ICE models. The PNECs of the eight PAHs were estimated based on the SSDs and acute to chronic ratio (ACR) method; these data were 0.071 μg/L, 0.033 μg/L, 0.049 μg/L, 0.114 μg/L, 0.019 μg/L, 0.021 μg/L, 0.038 μg/L and 0.054 μg/L for DMBA, DBA, BaP, MCA, BaA, CHR, BbF, BkF, respectively. The higher PNECs of the alkylated PAHs suggested their lower ecological risks. Based on the mixed risk quotient (mRQ) of PAHs through the concentration addition (CA) model, high ecological risk watersheds, such as the Songhua River (mRQ = 1.95), the Liao River (mRQ = 4.59), and the Huai River (mRQ = 1.93), were identified.

Optimized Derivation of Predicted No-Effect Concentrations (PNECs) for Eight Polycyclic Aromatic Hydrocarbons (PAHs) Using HC10 Based on Acute Toxicity Data

For persistent organic pollutants, a concern of environmental supervision, predicted no-effect concentrations (PNECs) are often used in ecological risk assessment, which is commonly derived from the hazardous concentration of 5% (HC₅) of the species sensitivity distribution (SSD). To address the problem of a lack of toxicity data, the objectives of this study are to propose and apply two improvement ideas for SSD application, taking polycyclic aromatic hydrocarbons (PAHs) as an example: whether the chronic PNEC can be derived from the acute SSD curve; whether the PNEC may be calculated by HC₁₀ to avoid solely statistical extrapolation. In this study, the acute SSD curves for eight PAHs and the chronic SSD curves for three PAHs were constructed. The quantity relationship of HC₅s between the acute and chronic SSD curves was explored, and the value of the assessment factor when using HC₁₀ to calculate PNEC was derived. The results showed that, for PAHs, the chronic PNEC can be estimated by multiplying the acute PNEC by 0.1, and the value of the assessment factor corresponding to HC₁₀ is 10. For acenaphthene, anthracene, benzo[a]pyrene, fluoranthene, fluorene, naphthalene, phenanthrene, and pyrene, the chronic PNECs based on the acute HC₁₀s were 0.8120, 0.008925, 0.005202, 0.07602, 2.328, 12.75, 0.5731, and 0.05360 μg/L, respectively.

Biomarker responses in mussels (Mytilus trossulus) from the Baltic Sea exposed to water-accommodated fraction of crude oil and a dispersant at different salinities

Oil spills pose significant environmental risks, particularly in cold seas. In the Baltic Sea, the low salinity (from 0 to 2 up to 18) affects the behaviour of the spilled oil as well as the efficiency and ecological impacts of oil spill response methods such as mechanical collection and the use of dispersants. In the present study, mussels (Mytilus trossulus) were exposed under winter conditions (5 °C) to the water-accommodated fraction (WAF) of Naphthenic North Atlantic crude oil prepared by mechanical dispersion or to the chemically enhanced fraction (CEWAF) obtained using the dispersant Finasol OSR 51 at salinities of 5.6 and 15.0. Especially at the lower salinity, high bioaccumulation of polycyclic aromatic hydrocarbons was recorded in mussels in the CEWAF treatments, accompanied by increased biomarker responses. In the WAF treatments these impacts were less evident. Thus, the use of dispersants in the Baltic Sea still needs to be carefully considered.

Alkyl-phenanthrenes in early life stage fish: differential toxicity in Atlantic haddock (Melanogrammus aeglefinus) embryos

Tricyclic polycyclic aromatic hydrocarbons (PAHs) are believed to be the primary toxic components of crude oil. Such compounds including phenanthrene are known to have direct effects on cardiac tissue, which lead to malformations during organogenesis in early life stage fish. We tested a suite of 13 alkyl-phenanthrenes to compare uptake and developmental toxicity in early life stage haddock (Melanogrammus aeglefinus) embryos during gastrulation/organogenesis beginning at 2 days post fertilization via passive dosing. The alkyl-phenanthrenes were tested at their solubility limits, and three of them also at lower concentrations. Measured body burdens were linearly related to measured water concentrations. All compounds elicited one or more significant morphological defects or functional impairment, such as decreased length, smaller eye area, shorter jaw length, and increased incidence of body axis deformities and eye deformities. The profile of developmental toxicities appeared unrelated to the position of alkyl substitution, and gene expression of cytochrome 1 a (cyp1a) was low regardless of alkylation. Mortality and sublethal effects were observed below the expected range for baseline toxicity, thus indicating excess toxicity. Additionally, PAH concentrations that resulted in toxic effects here were far greater than when measured in whole crude oil exposures that cause toxicity. This work demonstrates that, while these phenanthrenes are toxic to early life stage fish, they cannot individually account for most of the developmental toxicity of crude oil, and that other compounds and/or mixture effects should be given more consideration.

Comparison of PAC and MOAH for understanding the carcinogenic and developmental toxicity potential of mineral oils

The carcinogenicity and developmental toxicity of unrefined mineral oil is related to its 3-7 ring polycyclic aromatic compounds (PAC) content. Therefore, refining operations focus on the targeted removal PAC from mineral oil that may contain aromatics of low toxicological concern. There are thus, two types of aromatic substances in mineral oil: hazardous and non-hazardous. The first type consists of 3-7 ring PAC which may be naked (unsubstituted) or lowly alkylated. The second type or non-hazardous consists of 1-7 ring aromatics with high degree of alkylation or lack of bay or fjord regions. Although these are toxicologically different, they may both elute in the same fraction when using chromatography. To understand how these two aromatic types are related we have assessed the entire mineral oil refinement process by measuring total mineral oil aromatic hydrocarbons (MOAH) content by chromatography next to regulatory hazard tests which focus on 3-7 ring PAC. MOAH content is positively correlated to its molecular weight resulting in aromatic content bias for high viscosity substances. Hazard to 3-7 ring PAC is best controlled by the validated IP346 or modified Ames test. We explain the concept of high vs low alkylation by shortly reviewing new data on alkylated PAC.

The effects of polycyclic aromatic compounds (PACs) on mammalian ovarian function

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Toxicity of polycyclic aromatic compounds (PACs) is limited to a subset of PACs.

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Exposure to these compounds impact major processes necessary for ovarian function.

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PAC exposure causes follicle loss and aberrant steroid production and angiogenesis.

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PAC exposure may increase the risk for impaired fertility and ovarian pathologies.

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The study of PACs as ovarian toxicants should include additional compounds.

Polycyclic aromatic compounds (PACs) are a broad class of contaminants ubiquitously present in the environment due to natural and anthropogenic activities. With increasing industrialization and reliance on petroleum worldwide, PACs are increasingly being detected in different environmental compartments. Previous studies have shown that PACs possess endocrine disruptive properties as these compounds often interfere with hormone signaling and function. In females, the ovary is largely responsible for regulating reproductive and endocrine function and thus, serves as a primary target for PAC-mediated toxicity. Perturbations in the signaling pathways that mediate ovarian folliculogenesis, steroidogenesis and angiogenesis can lead to adverse reproductive outcomes including polycystic ovary syndrome, premature ovarian insufficiency, and infertility. To date, the impact of PACs on ovarian function has focused predominantly on polycyclic aromatic hydrocarbons like benzo(a)pyrene, 3-methylcholanthrene and 7,12-dimethylbenz[a]anthracene. However, investigation into the impact of substituted PACs including halogenated, heterocyclic, and alkylated PACs on mammalian reproduction has been largely overlooked despite the fact that these compounds are found in higher abundance in free-ranging wildlife. This review aims to discuss current literature on the effects of PACs on the ovary in mammals, with a particular focus on folliculogenesis, steroidogenesis and angiogenesis, which are key processes necessary for proper ovarian functions.

Exposure to retene, fluoranthene, and their binary mixture causes distinct transcriptomic and apical outcomes in rainbow trout (Oncorhynchus mykiss) yolk sac alevins

Polycyclic aromatic hydrocarbons (PAHs) are widely spread environmental contaminants which affect developing organisms. It is known that improper activation of the aryl hydrocarbon receptor (AhR) by some PAHs contributes to toxicity, while other PAHs can disrupt cellular membrane function. The exact downstream mechanisms of AhR activation remain unresolved, especially with regard to cardiotoxicity. By exposing newly hatched rainbow trout alevins (Oncorhynchus mykiss) semi-statically to retene (32 µg l^-1; AhR agonist), fluoranthene (50 µg l^-1; weak AhR agonist and CYP1a inhibitor) and their binary mixture for 1, 3, 7 and 14 days, we aimed to uncover novel mechanisms of cardiotoxicity using a targeted microarray approach. At the end of the exposure, standard length, yolk area, blue sac disease (BSD) index and PAH body burden were measured, while the hearts were prepared for microarray analysis. Each exposure produced a unique toxicity profile. We observed that retene and the mixture, but not fluoranthene, significantly reduced growth by Day 14 compared to the control, while exposure to the mixture increased the BSD-index significantly from Day 3 onward. Body burden profiles were PAH-specific and correlated well with the exposure-specific upregulations of genes encoding for phase I and II enzymes. Exposure to the mixture over-represented pathways related to growth, amino acid and xenobiotic metabolism and oxidative stress responses. Alevins exposed to the individual PAHs displayed over-represented pathways involved in receptor signaling: retene downregulated genes with a role in G-protein signaling, while fluoranthene upregulated those involved in GABA signaling. Furthermore, exposure to retene and fluoranthene altered the expression of genes encoding for proteins involved in calcium- and potassium ion channels, which suggests affected heart structure and function. This study provides deeper understanding of the complexity of PAH toxicity and the necessity of investigating PAHs as mixtures and not as individual components.

Developmental toxicity testing of unsubstituted and methylated 4- and 5-ring polycyclic aromatic hydrocarbons using the zebrafish embryotoxicity test

The present study evaluates the in vitro developmental toxicity of 4- and 5-ring PAHs including benz[a]anthracene and benzo[a]pyrene and six of their monomethylated congeners, and dibenz[a,h]anthracene using the zebrafish embryotoxicity test (ZET). In general, the tested PAHs induced various developmental effects in the zebrafish embryos including unhatched embryos, no movement and circulation, yolk sac and pericardial edemas, deformed body shape, and cumulative mortality at 96 h post fertilization (hpf). The alkyl substituent on different positions of the aromatic ring of the PAHs appeared to change their in vitro developmental toxicity. Comparison to a previously reported molecular docking study showed that the methyl substituents may affect the interaction of the PAHs with the aryl hydrocarbon receptor (AhR) which is known to play a role in the developmental toxicity of some PAHs. Taken together, our results show that methylation can either increase or decrease the developmental toxicity of PAHs and suggest this may relate to effects on the molecular dimensions and resulting consequences for interactions with the AhR.

Substituted Two- to Five-Ring Polycyclic Aromatic Compounds Are Potent Agonists of Atlantic Cod (Gadus morhua) Aryl Hydrocarbon Receptors Ahr1a and Ahr2a

Polycyclic aromatic hydrocarbons (PAHs) are among the most toxic and bioavailable components found in petroleum and represent a high risk to aquatic organisms. The aryl hydrocarbon receptor (Ahr) is a ligand-activated transcription factor that mediates the toxicity of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) and other planar aromatic hydrocarbons, including certain PAHs. Ahr acts as a xenosensor and modulates the transcription of biotransformation genes in vertebrates, such as cytochrome P450 1A (cyp1a). Atlantic cod (Gadus morhua) possesses two Ahr proteins, Ahr1a and Ahr2a, which diverge in their primary structure, tissue-specific expression, ligand affinities, and transactivation profiles. Here, a luciferase reporter gene assay was used to assess the sensitivity of the Atlantic cod Ahrs to 31 polycyclic aromatic compounds (PACs), including two- to five-ring native PAHs, a sulfur-containing heterocyclic PAC, as well as several methylated, methoxylated, and hydroxylated congeners. Notably, most parent compounds, including naphthalene, phenanthrene, and partly, chrysene, did not act as agonists for the Ahrs, while hydroxylated and/or alkylated versions of these PAHs were potent agonists. Importantly, the greater potencies of substituted PAH derivatives and their ubiquitous occurrence in nature emphasize that more knowledge on the toxicity of these environmentally and toxicologically relevant compounds is imperative.

Occurrence, fates, and carcinogenic risks of substituted polycyclic aromatic hydrocarbons in two coking wastewater treatment systems

This paper reports for the first time the occurrence, fates, and carcinogenic risks of 20 substituted polycyclic aromatic hydrocarbons (SPAHs) and 16 priority PAH species in two coking wastewater treatment plants (WWTPs) (plant E and central WWTP). The measured total concentrations of PAHs and SPAHs in raw wastewater of coking plant E were 3700 and 1200 μg·L^-1, respectively, with naphthalene (1400 μg·L^-1), and fluoranthene (353 μg·L^-1) as dominant PAH species and 2-methylnaphthalene (167 μg·L^-1), anthraquinone (133 μg·L^-1), and 1-methylnaphthalene (132 μg·L^-1) as dominant SPAHs. For the 11 methyl-PAHs (MPAHs), 4 oxygenated-PAHs (OPAHs), and 5 nitrated-PAHs (NPAHs) investigated, the biological wastewater treatment process removed 98.6% MPAHs, 83.9% OPAHs, and 89.1% NPAHs. Mass balance analysis result revealed that transformation was the major mechanism to remove low-molecular-weight (LMW) MPAHs (59.9-77.3%), a large part of OPAHs, including anthraquinone, methylanthraquinone, and 9-fluorenone (46.7-49.6%), and some NPAHs, including 2-nitrofluorene and 9-nitroanthrancene (52.9-59.1%). Adsorption by activated sludge mainly accounted for removing high-molecular-weight (HMW) SPAHs (59.6-71.01%). The relatively high concentrations of SPAHs in excess sludge (15,000 μg·g^-1) and treated effluent (104 μg·L^-1) are of great concern for their potential adverse ecological impacts. SPAHS exhibited similar behaviors in central WWTP, though the influent concentrations were much lower. The concentration levels of SPAHs in the ambient air of coking plant E and central WWTP may also pose potential lung cancer risks (LCR) to the workers through inhalation, where all studied SPAHs except 3-nitrofluoranthene and 7-nitrobenz[a]anthracene exceeded the acceptable cancer risk standards (>10^-6) recommended by U.S EPA. This study could help identify the ecological and healthy risks during coking wastewater treatment and provide useful information for policy-making.

Coastal ecosystem inventory with characterization and identification of plastic contamination and additives from aquaculture materials

In the early 1970s, studies of marine litter first appeared in the scientific literature. Fifty years later, knowledge of several coastal areas of the Atlantic, the driving forces of oyster farmers and aquaculture, is lacking. This work documents a pilot study on an Atlantic coastal area (France). This study aims to (i) characterize the abundance of macroplastics related to aquaculture tools; (ii) microplastics present in beach sediments and (iii) characterization of pollutants present on aquaculture plastics collected. First, it was observed that 70% of the plastics collected on the beach were characteristic of aquaculture materials. In sediments, MPs most found were Polyamide between 10 and 20 μm, with a total MP concentration of 397-457 MPs.kg^-1. Pipes collectors (PVC), frequently used in aquaculture, have been shown to have concentrations of dimethylphthalates and naphthalene. Waste management and support policies can then base their actions on such studies, in order to improve their knowledge.

Isotopic Analyses Fingerprint Sources of Polycyclic Aromatic Compound-Bearing Dust in Athabasca Oil Sands Region Snowpack

Fugitive dust associated with surface mining activities is one of the principal vectors for transport of airborne contaminants in Canada's Athabasca oil sands region (AOSR). Effective environmental management requires quantitative identification of the sources of this dust. Using natural abundance radiocarbon (Δ¹⁴C) and dual (δ¹³C, δ²H) compound-specific isotope analysis (CSIA), this study investigated the sources of dust and particulate-bound polycyclic aromatic compounds (PACs) deposited in AOSR lake snowpack. Lower Δ¹⁴C values, higher particulate and PAC loadings, and lower δ¹³C values for phenanthrene and C1-alkylated phenanthrenes/anthracenes (C1-Phen) at sites closer to the mining operations indicated unprocessed oil sand and/or petroleum coke (petcoke-a byproduct of bitumen upgrading) as major sources of anthropogenic fugitive dust. However, a Bayesian isotopic mixing model that incorporated both δ¹³C and δ²H could discriminate petcoke from oil sand, and determined that petcoke comprised between 44 and 95% (95% credibility intervals) of a C1-Phen isomer at lakes <25 km from the heart of the mining operations, making it by far the most abundant source. This study is the first to demonstrate the potential of CSIA to provide accurate PAC source apportionment in snowpack and reveals that petcoke rather than oil sand is the main source of mining-related particulate PACs deposited directly to AOSR lakes.

Polycyclic aromatic compounds (PACs) in the Canadian environment: The challenges of ecological risk assessments

Ecological risk assessments (ERAs) of polycyclic aromatic compounds (PACs), as single congeners or in mixtures, present technical challenges that raise concerns about their accuracy and validity for Canadian environments. Of more than 100,000 possible PAC structures, the toxicity of fewer than 1% have been tested as individual compounds, limiting the assessment of complex mixtures. Because of the diversity in modes of PAC action, the additivity of mixtures cannot be assumed, and mixture compositions change rapidly with weathering. In vertebrates, PACs are rapidly oxygenated by cytochrome P450 enzymes, often to metabolites that are more toxic than the parent compound. The ability to predict the ecological fate, distribution and effects of PACs is limited by toxicity data derived from tests of a few responses with a limited array of test species, under optimal laboratory conditions. Although several models are available to predict PAC toxicity and rank species sensitivity, they were developed with data biased by test methods, and the reported toxicities of many PACs exceed their solubility limits. As a result, Canadian Environmental Quality Guidelines for a few individual PACs provide little support for ERAs of complex mixtures in emissions and at contaminated sites. These issues are illustrated by reviews of three case studies of PAC-contaminated sites relevant to Canadian ecosystems. Interactions among ecosystem characteristics, the behaviour, fate and distribution of PACs, and non-chemical stresses on PAC-exposed species prevented clear associations between cause and effect. The uncertainties of ERAs can only be reduced by estimating the toxicity of a wider array of PACs to species typical of Canada's diverse geography and environmental conditions. Improvements are needed to models that predict toxicity, and more field studies of contaminated sites in Canada are needed to understand the ecological effects of PAC mixtures.

Polycyclic aromatic compounds (PACs) in the Canadian environment: A review of sampling techniques, strategies and instrumentation

A wide variety of sampling techniques and strategies are needed to analyze polycyclic aromatic compounds (PACs) and interpret their distributions in various environmental media (i.e., air, water, snow, soils, sediments, peat and biological material). In this review, we provide a summary of commonly employed sampling methods and strategies, as well as a discussion of routine and innovative approaches used to quantify and characterize PACs in frequently targeted environmental samples, with specific examples and applications in Canadian investigations. The pros and cons of different analytical techniques, including gas chromatography - flame ionization detection (GC-FID), GC low-resolution mass spectrometry (GC-LRMS), high performance liquid chromatography (HPLC) with ultraviolet, fluorescence or MS detection, GC high-resolution MS (GC-HRMS) and compound-specific stable (δ¹³C, δ²H) and radiocarbon (Δ¹⁴C) isotope analysis are considered. Using as an example research carried out in Canada's Athabasca oil sands region (AOSR), where alkylated polycyclic aromatic hydrocarbons and sulfur-containing dibenzothiophenes are frequently targeted, the need to move beyond the standard list of sixteen EPA priority PAHs and for adoption of an AOSR bitumen PAC reference standard are highlighted.

Quantum chemical calculation to elucidate the biodegradation pathway of methylphenanthrene by green microalgae

Alkylated polycyclic aromatic hydrocarbons (APAHs) are the main components of polycyclic aromatic hydrocarbons (PAHs) in petroleum-contaminated waters. In our study, three kinds of green microalgae (Pseudokirchneriella subcapitata, Chlorella vulgaris and Scenedesmus obliquus) were shown to degrade six kinds of methylphenanthrenes (1-methylphenanthren, 2-methylphenanthrenem, 3-nmmethylphenanthrene, 4-methylphenanthren, 9-methylphenanthrene and 3,6-dimethylphenanthrene) with different degrading abilities. Among the six methylphenanthrenes, 99.8% of 1-methylphenanthrene (1-MP) was removed and 75.6% of 3,6-dimethylphenanthrene (3,6-DMP) was removed by P. subcapitata after 7 days of incubation. The metabolites of 1-MP and 3,6-DMP were identified by gas chromatograph-mass spectrometer (GC-MS). Six metabolites of 1-MP and one metabolite of 3,6-DMP were found, they were all monohydroxylated methylphenanthrenes. The -OH group was added to either methyl-group or benzene ring through the monooxygenase system, and the methyl-group attack was the main pathway. This research increases our knowledge of the degrading ability of APAHs by green microalgae and offers information for the bioremediation of APAHs. Quantum chemical calculation was conducted to elucidate the biodegradation metabolites of methylphenanthrene by green microalgae, which is a helpful tool in the bioremediation of environmental pollution.

Changes in Reef Fish Community Structure Following the Deepwater Horizon Oil Spill

Large-scale anthropogenic disturbances can have direct and indirect effects on marine communities, with direct effects often taking the form of widespread injury or mortality and indirect effects manifesting as changes in food web structure. Here, we report a time series that captures both direct and indirect effects of the Deepwater Horizon Oil Spill (DWH) on northern Gulf of Mexico (nGoM) reef fish communities. We observed significant changes in community structure immediately following the DWH, with a 38% decline in species richness and 26% decline in Shannon-Weiner diversity. Initial shifts were driven by widespread declines across a range of trophic guilds, with subsequent recovery unevenly distributed among guilds and taxa. For example, densities of small demersal invertivores, small demersal browsers, generalist carnivores, and piscivores remained persistently low with little indication of recovery seven years after the DWH. Initial declines among these guilds occurred prior to the arrival of the now-widespread, invasive lionfish (Pterois spp.), but their lack of recovery suggests lionfish predation may be affecting recovery. Factors affecting persistently low densities of generalist carnivores and piscivores are not well understood but warrant further study given the myriad ecosystem services provided by nGoM reef fishes.

Insights about the toxicity of tannery effluent on chicken (Gallus gallus domesticus) embryos

Although tannery effluent (TE) toxicity has already been demonstrated in different vertebrate models, our knowledge about their effects on birds remains significantly incipient. Thus, the aim of the current study was to evaluate the impact of ephemeral exposure of Gallus gallus domesticus eggs to environmental predictive TE dilutions (1.4% and 6.5%). Eggs at E6 developmental stage were opened in order to assess embryos' external morphology and genotoxic biomarkers. Based on our data, embryos exposed in ovo to TE recorded higher mortality rate, lower biomass and different morphological abnormalities such as optic vesicle depigmentation, pericardial and encephalic edemas, as well as body rotation error. Embryos exposed to TE showed lower crown-rump length head and anterior-posterior length, as well as reduced beak size. Embryos exposed to the highest TE dilution (6.5%) also showed greater lower/upper limb development, larger optic vesicle area and smaller crystalline lens area than the other groups. On the other hand, differences in mitotic index were not observed between groups; however, total erythrocyte chromosomal abnormalities, mainly in metaphase and anaphase, were higher in embryos exposed to TE. These phases presented chromosome fragments formed from typical chromosome breakage, laggard chromosome and chromosome bridge. Higher Cr, Mn and Zn concentrations in embryos exposed to TE strongly suggest that the observed abnormalities were directly associated with the absorption of chemical constituents. The present study is pioneer in investigating the morphotoxic and genotoxic potential of TE (a complex mixture of various xenobiotics) in bird embryos in order to better understand the eco (toxicological) magnitude of this pollutant in aquatic ecosystems.

Physiological disturbances in juvenile sockeye salmon (Oncorhynchus nerka) exposed to the water-soluble fraction of diluted bitumen

Current and proposed transcontinental pipelines for the transport of diluted bitumen (dilbit) from the Canadian oil sands traverse the coastal watersheds of British Columbia, habitat essential to Pacific salmonids. To determine the potential risks posed to these keystone species, juvenile sockeye (Oncorhynchus nerka; 1+ parr) were acutely (24-96 h) or subchronically (21-42 d) exposed to 4 concentrations of the water-soluble fraction (WSF) of unweathered Cold Lake Blend dilbit (initial total PAC concentrations: 0, 13.7, 34.7 and 124.5 μg/L) in a flow-through system. Dilbit effects on iono-osmoregulation, the physiological stress response, and the immune system were assessed by both biochemical and functional assays. Hydrocarbon bioavailability was evidenced by a significant induction of liver ethoxyresorufin-O-deethylase (EROD) activity in exposed fish. Acute and subchronic exposure significantly reduced gill Na⁺-K⁺-ATPase activity and resulted in lower plasma osmolality, Cl^-, and Na⁺ concentrations. Acute exposure to dilbit resulted in a classic physiological stress response, however at 21 d of exposure, plasma cortisol remained elevated while other measured parameters had returned to baseline values. A compromised immune system was demonstrated by a 29.5 % higher mortality in fish challenged with Vibrio (Listonella) anguillarum following dilbit exposure compared to unexposed controls. Exposure of juvenile salmonids to the WSF of dilbit (at TPAC concentrations at the ppb level) resulted in sublethal effects that included a classic physiological stress response, and alterations in iono-osmoregulatory homeostasis and immunological performance.

Characterizing Crude Oil Toxicity to Early-Life Stage Fish Based On a Complex Mixture: Are We Making Unsupported Assumptions?

Numerous studies of the water-soluble fraction (WSF) from crude oil have concluded that polycyclic aromatic hydrocarbons (PAHs) are the primary causative agents for early life stage (ELS) fish toxicity. Noteworthy is the lack of studies demonstrating that the sum of PAHs are capable of causing toxic effects in ELS fish at the low levels claimed (0.1-5 μg/L) without being part of a complex crude oil mixture. Crude oil and the WSF are composed of thousands of other compounds that co-occur and likely contribute to crude oil toxicity. Based on the available data, it appears that the syndrome of effects (lower heart rate, edemas, and morphological abnormalities) for ELS fish exposed to the aqueous fraction of a crude oil mixture is commonly observed in studies exposing fish embryos to high concentrations of a variety of compounds and may be a nonspecific response. We conclude that the available data support the hypothesis that this syndrome of effects is likely the result of baseline toxicity (not receptor based) due to membrane disruption and resulting alteration in ion (e.g., calcium and potassium) homeostasis. We acknowledge the possibility of some compounds in the WSF capable of causing a specific receptor based toxicity response to ELS fish; however, such compounds have not been identified nor their receptor characterized. Concluding that PAHs are the main toxic compounds for crude oil exposure is misleading and does not result in guideline values that can be useful for environmental protection. Water quality guidelines for any single chemical or suite of chemicals must be based on a complete understanding of exposure concentrations, mechanism of action, potency, and resulting response. This review focuses on the toxic effects reported for fish embryos and the purported toxic concentrations observed in the aqueous phase of an oil/water mixture, the known levels of toxicity for individual PAHs, a toxic unit approach for characterizing mixtures, and the potential molecular initiating event for ELS toxicity in fish. This review also has implications for a large number of studies exposing ELS fish to a variety of compounds at high concentrations that result in a common baseline toxic response.

Long-term effects of an early-life exposure of fathead minnows to sediments containing bitumen. Part I: Survival, deformities, and growth

The aim of this study was to investigate the long-term effects of a short exposure to natural sediments within the Athabasca oil sand formation to critical stages of embryo-larval development in fathead minnows (Pimephales promelas). Three different sediments were used: Ref sediment from the upper Steepbank River tested at 3 g/L (containing 12.2 ng/g ∑PAHs), and two bitumen-rich sediments tested at 1 and 3 g/L; one from the Ells River (Ells downstream, 6480 ng/g ∑PAHs) and one from the Steepbank River (Stp downstream, 4660 ng/g ∑PAHs). Eggs and larvae were exposed to sediments for 21 days, then transferred to clean water for a 5-month grow-out and recovery period. Larval fish had significantly decreased survival after exposure to 3 g/L sediment from Stp downstream, and decreased growth (length and weight at 16 days post hatch) in Ells and Stp downstream sediments at both 1 and 3 g/L. Decreased tail length was a sensitive endpoint in larval fish exposed to Ells and Stp downstream sediments for 21 days compared to Ref sediment. After the grow-out in clean water, all growth effects from the bitumen-containing sediments recovered, but adult fish from Stp downstream 3 g/L sediment had significant increases in jaw deformities. The study shows the potential for fish to recover from the decreased growth effects caused by sediments containing oil sands-related compounds, but that some effects of the early-life sediment exposure occur later on in adult fish.

Changes in ecotoxicity of naphthalene and alkylated naphthalenes during photodegradation in water

Crude oil released into the environment contains many polycyclic aromatic hydrocarbons (PAHs). Alkylated PAHs are more abundant than unsubstituted PAHs and their toxicity is also of serious concern. Among the various physical, chemical, and biological weathering processes of crude oils, photodegradation is one of the most important for determining the environmental fate of oil residues. In this study, the photodegradation rate constants of naphthalene and alkylated naphthalenes were determined under simulated laboratory conditions at different temperature. Changes in the luminescence inhibition of Aliivibrio fischeri, as an indicator of the baseline toxicity, were observed in photodegradation mixtures. The major transformation products were also identified by gas chromatography-mass spectrometry. The photodegradation of naphthalene and the eight alkylated naphthalenes was described well by pseudo-first-order kinetics regardless of experimental temperature. The measured toxicity of the reaction mixtures obtained by photodegradative weathering slightly increased initially and then decreased with further weathering. In all cases, the observed toxicity was greater than accounted for by the parent compounds, indicating that the photodegradation products also contributed significantly to the overall toxicity of the mixtures. The identified photodegradation products were mostly oxygenated compounds such as alcohols, aldehydes, ketones, and quinones, which warrant further investigation.

Deposition Mapping of Polycyclic Aromatic Compounds in the Oil Sands Region of Alberta, Canada and Linkages to Ecosystem Impacts

This study produced gridded deposition estimates of polycyclic aromatic compounds (PACs), including 17 polycyclic aromatic hydrocarbons (PAHs), 21 alkylated PAHs (alk-PAHs), and 5 dibenzothiophenes (DBTs), over the oil sands region of Alberta, Canada and surrounding communities. Gridded annual total deposition of PACs in 2011 ranged from 55 to 175 000 μg m^-2 yr^-1 and the mean and median fluxes were 1700 and 760 μg m^-2 yr^-1, respectively. The domain-wide mean dry and wet deposition were 600 and 1100 μg m^-2 yr^-1. PAHs, alk-PAHs and DBTs contributed 19%, 74%, and 7% to the total dry deposition, and 42%, 49%, and 9% to the total wet deposition. Dominant chemical species contributing to total deposition were naphthalene, retene and phenanthrene for PAHs and C2-benz[a]anthracene/triphenylene/chrysene, C2-fluoranthene/pyrene and C2-fluorene for alk-PAHs. The highest PAC deposition was found over the surface mineable area, which received 9 times the deposition flux of outlying areas. Additional deposition hotspots were also observed south of the surface mineable area notably over in situ bitumen production sites. The deposition of alk-PAHs impacted a more extensive area than that of PAHs or DBTs. This result suggests that atmospheric deposition is a key process in wildlife exposure to PACs across the region.

Combined effects of elevated temperature and Deepwater Horizon oil exposure on the cardiac performance of larval mahi-mahi, Coryphaena hippurus

The 2010 Deepwater Horizon oil spill coincided with the spawning season of many pelagic fish species in the Gulf of Mexico. Yet, few studies have investigated physiological responses of larval fish to interactions between anthropogenic crude oil exposure and natural factors (e.g. temperature, oxygen levels). Consequently, mahi mahi (Coryphaena hippurus) embryos were exposed for 24 hours to combinations of two temperatures (26 and 30°C) and six concentrations of oiled fractions of weathered oil (from 0 to 44.1 μg ∑50PAHs·L^-1). In 56 hours post-fertilization larvae, heart rate, stroke volume and cardiac output were measured as indicators of functional cardiac phenotypes. Fluid accumulation and incidence of edema and hematomas were quantified as indicators of morphological impairments. At both 26 and 30°C, oil-exposed larvae suffered dose-dependent morphological impairments and functional heart failure. Elevation of temperature to 30°C appeared to induce greater physiological responses (bradycardia) at PAH concentrations in the range of 3.0–14.9 μg·L^-1. Conversely, elevated temperature in oil-exposed larvae reduced edema severity and hematoma incidence. However, the apparent protective role of warmer temperature does not appear to protect against enhanced mortality. Collectively, our findings show that elevated temperature may slightly decrease larval resilience to concurrent oil exposure.

The aquatic hazard of hydrocarbon liquids and gases and the modulating role of pressure on dissolved gas and oil toxicity

Hydrostatic pressure enhances gas solubility and potentially alters toxicity and risks of oil and gas releases to deep-sea organisms. This study has two primary objectives. First, the aquatic hazard of dissolved hydrocarbon gases is characterized using results of previously published laboratory and field studies and modeling. The target lipid model (TLM) is used to predict effects at ambient pressure, and results are compared to effect concentrations derived from extrapolation of liquid alkane hazard data. Second, existing literature data are used to quantify and predict pressure effects on toxicity using an extension of the TLM framework. Results indicate elevated pressure mitigates narcosis, particularly for sensitive species. A simple adjustment is proposed to allow TLM-based estimates of acute effect and TLM-derived HC5 values (concentrations intended to provide 95% species protection) for oil or gas constituents to be calculated at depth. Future applications, and opportunities and challenges for providing validation, are discussed.

Meltwater from snow contaminated by oil sands emissions is toxic to larval fish, but not spring river water

To assess the toxicity of winter-time atmospheric deposition in the oil sands mining area of Northern Alberta, embryo-larval fathead minnow (Pimephales promelas) were exposed to snowmelt samples. Snow was collected in 2011-2014 near (<7km) oil sands open pit mining operations in the Athabasca River watershed and at sites far from (>25km) oil sands mining. Snow was shipped frozen back to the laboratory, melted, and amended with essential ions prior to testing. Fertilized fathead minnow eggs were exposed (<24h post-fertilization to 7-16days post-hatch) to a range of 25%-100% snowmelt. Snow samples far from (25-277km away) surface mining operations and upgrading facilities did not affect larval fathead minnow survival at 100%. Snow samples from sites near surface mining and refining activities (<7km) showed reduced larval minnow survival. There was some variability in the potencies of snow year-to-year from 2011 to 2014, and there were increases in deformities in minnows exposed to snow from 1 site on the Steepbank River. Although exposure to snowmelt from sites near oil sands surface mining operations caused effects in larval fish, spring melt water from these same sites in late March-May of 2010, 2013 and 2014 showed no effects on larval survival when tested at 100%. Snow was analyzed for metals, total naphthenic acid concentrations, parent PAHs and alkylated PAHs. Naphthenic acid concentrations in snow were below those known to affect fish larvae. Concentrations of metals in ion-amended snow were below published water quality guideline concentrations. Compared to other sites, the snowmelt samples collected close to mining and upgrading activities had higher concentrations of PAHs and alkylated PAHs associated with airborne deposition of fugitive dusts from mining and coke piles, and in aerosols and particles from stack emissions.

CAPSULE

Snow collected close to oil sands surface mining sites is toxic to larval fathead minnows in the lab; however spring melt water samples from the same sites do not reduce larval fish survival.

Oil sands tailings pond sediment toxicity to early life stages of northern pike (Esox lucius)

The Athabasca River in Alberta flows through natural sources of eroding oil sands bitumen and oil sands mining operations that may result in low level contamination of surface waters. Northern pike (Esox lucius) are apex predators and important food and game fish species native to the Athabasca River system. This species has the potential to be exposed to both natural and anthropogenic sources of contamination from oil sands related materials throughout its life cycle. Pike are difficult to rear in the laboratory and little information exists on the toxicity of oil sands related materials to this key indigenous fish species. In this study, the potential effects of two sediment samples collected from different areas of one tailings pond in the Athabasca oil sands area are assessed in a daily renewal bioassay on early life stages of northern pike. Gametes were collected from spawning wild pike captured from a reference site outside of the oil sands area. Fertilized eggs were exposed to control water or increasing concentrations of tailings pond sediments for 21days, coinciding with initiation of exogenous feeding and completion of yolk absorption. Developing fish were examined for survival and changes in body weight, length, and development. Embryos exhibited increased developmental abnormalities and decreased growth and survival with increasing sediment concentration. Both sediment samples had similar levels of naphthenic acids and similar types of PAHs, with alkylated PAHs dominating. However, concentrations of total and alkylated PAHs differed between sediment samples and were related to increasing developmental abnormalities and decreased growth and survival. This is consistent with developmental changes observed with exposure to PAHs in other fish species. These results provide information on the effects of tailings pond sediments comprising mixtures of PAHs and alkylated PAHs on the development and survival of a key species in the northern aquatic ecosystem.

Repeatability of n-octanol/water partition coefficient values between liquid chromatography measurement methods

The n-octanol/water partition coefficient (K_OW) is a physical/chemical property that is extensively used for regulatory and environmental risk and exposure assessments. The K_OW value can estimate various chemical properties such as water solubility, bioavailability, and toxicity using quantitative structure-activity relationships which demands an accurate knowledge of this property. The present investigation aims to compare outcomes of three commonly cited methods of K_OW measurement in the literature for six hydrophobic chemicals with insecticidal functions as well as highly volatile petroleum constituents. This measurement has been difficult to obtain for the selected pyrethroid insecticides, cypermethrin, and bifenthrin and is a novel measurement for the latter: polycyclic aromatic sulfur heterocycles, dibenzothiophene (DBT), and three of its alkyl derivatives except for DBT. The K_OW values were obtained using two liquid chromatographic methods with isocratic and gradient programming, and the slow-stirring method following OECD 117 and 123 guidelines, respectively. The mean log K_OW values of bifenthrin, cypermethrin, DBT, methyl-DBT, dimethyl-DBT, and diethyl-DBT were 8.4 ± 0.1, 6.0 ± 0.3, 4.8 ± 0.0, 5.4 ± 0.1, 6.0 ± 0.1, and 6.8 ± 0.0 using the HPLC method with gradient programing. The K_OW values were significantly reproducible within a method, however, not between the methods. Results suggest assessing a chemical's property and environmental risk and exposure solely based on the K_OW value should be practiced with caution.

An Embryonic Field of Study: The Aquatic Fate and Toxicity of Diluted Bitumen

Canada has experienced a significant increase in the transport of diluted bitumen (dilbit), a predominant oil sands product that combines bitumen with diluents derived from oil-gas condensates and other proprietary compounds. The proportion of diluent and the chemical composition of dilbit vary to meet seasonal transport requirements. While the toxic effects of a variety of crude and refined oils are well-studied, the toxicity of dilbit to aquatic species is less well known. This focused review summarizes dilbit production, chemistry, and the few data on toxicity to aquatic species. These data suggest that un-weathered dilbit would cause effects on fish equivalent to those of conventional oils, but its toxicity may be lower, depending on interactions among test conditions, the behavior of dilbit added to water and the species tested.

Comparative study of oxidative stress caused by anthracene and alkyl-anthracenes in Caenorhabditis elegans

Oxidative stress was evaluated for anthracene (Ant) and alkyl-Ants (9-methylanthracene [9-MA] and 9,10-dimethylanthracene [9,10-DMA]) in Caenorhabditis elegans to compare changes in toxicity due to the degree of alkylation. Worms were exposed at 1) the same external exposure concentration and 2) the maximum water-soluble concentration. Formation of reactive oxygen species, superoxide dismutase activity, total glutathione concentration, and lipid peroxidation were determined under constant exposure conditions using passive dosing. The expression of oxidative stress-related genes (daf-2, sir-2.1, daf-16, sod-1, sod-2, sod-3 and cytochrome 35A/C family genes) was also investigated to identify and compare changes in the genetic responses of C. elegans exposed to Ant and alkyl-Ant. At the same external concentration, 9,10-DMA induced the greatest oxidative stress, as evidenced by all indicators, except for lipid peroxidation, followed by 9-MA and Ant. Interestingly, 9,10-DMA led to greater oxidative stress than 9-MA and Ant when worms were exposed to the maximum water-soluble concentration, although the maximum water-soluble concentration of 9,10-DMA is the lowest. Increased oxidative stress by alkyl-Ants would be attributed to higher lipid-water partition coefficient and the π electron density in aromatic rings by alkyl substitution, although this supposition requires further confirmation.

Toxic evaluations of sediments in Tokyo Bay, Japan, using Japanese medaka embryos

Toxic risks of sediments collected from seven sites in Tokyo Bay were evaluated using Japanese medaka embryos. Those sediments with slight pore water were placed in grass petri dishes without overlying water. The most remarkable effect in the field sediment was to cause hatching delay in embryos, and the longest time until hatching took was 12.5 ± 1.6 days post-fertilization (dpf), although that in control group was 10.1 ± 0.7 dpf. A significant delay in hatching was observed at four sites. Because total carbon concentrations were relatively high in sediments at three of these four sites, several chemicals were expected to be residues in these sites and could cause their delay. Although extreme mortality was not observed at all sites, sediments collected from the site close to Kawasaki city induced 10 % mortality. Polycyclic aromatic hydrocarbon (PAH) concentrations were remarkably high at this site compared with other sites, and thus PAH toxicities could be causing the mortality. Concentration of heavy metals such as cadmium, copper, lead, and zinc in sediments were also determined, but no clear relationship was found between toxicities to embryos and the distribution of their concentrations.

Effects of oxygenated polycyclic aromatic hydrocarbons on the early life stages of Japanese medaka

Oxygenated polycyclic aromatic hydrocarbons (oxyPAHs) are directly discharged into the atmosphere with exhaust gas from diesel engine automobiles and industry and are also generated by photo-oxidation and/or microbial metabolism of parent polycyclic aromatic hydrocarbons (PAHs). They are widely distributed in environment, especially around urban areas. We evaluated the effects of exposure to oxyPAHs as acenaphthenequinone (ANQ), 7,12-benz(a)anthracenequinone (BAQ), 1,4-naphthoquinone (NAQ), and 9,10-phenanethrenequinone (PHQ) in Japanese medaka (Oryzias latipes) embryos. ANQ (>2720 μg/L) caused caving in the yolk sac, and BAQ (>22.4 μg/L) caused tanning of the oil droplet. Additionally, NAQ (>314 μg/L) and PHQ (>734 μg/L) stopped development of medaka embryos beginning 2 days after the start of exposure. The hatched larvae from embryos exposed to ANQ, BAQ, NAQ, or PHQ at 518, 9.86, 36.5, or 80.7 μg/L, respectively, exhibited incomplete development of the cephalic region, incomplete palate, unabsorbed and hypertrophied yolk sac, tubular heart, altered axial curvature, and poor swimming ability. These symptoms were similar to those observed in blue sac disease, which is caused by exposure to PAHs.

Oil spill off the coast of Guimaras Island, Philippines: Distributions and changes of polycyclic aromatic hydrocarbons in shellfish

The sinking of the Solar 1 tanker caused serious heavy oil pollution around Guimaras Island, Philippines. In the present study, variations of parent polycyclic aromatic hydrocarbons (PAHs) and alkylated PAHs (alkPAHs) in some shellfish were investigated around Guimaras Island and other small islands from 3months to 5years after the spill. The total PAHs and alkPAHs in shellfish were detected in high concentrations at 448 and 33,666ng/g dry weight, respectively, in November 2006. The concentrations of alkPAHs gradually decreased, while the parent PAHs in shellfish degraded more slowly than the alkPAHs, which was likely due to the persistent characteristics of PAHs. The risks based on European Union regulations were insignificant in 2008, but total PAHs in shellfish were still over 8 times higher at the investigated sites in November 2011 than that before the oil spill.

Assessing the toxicity of triphenyltin to different life stages of the marine medaka Oryzias melastigma through a series of life-cycle based experiments

Toxic effects of triphenyltin (TPT) to different life stages of the marine medaka Oryzias melastigma were investigated through a series of life-cycle based exposure experiments. In embryo stage, TPT exposure could elevate the heartbeat rate at Day 6-8 post-fertilization and increase the expression levels of five heart development related genes (i.e., ATPase, COX2, BMP4, GATA4 and NKX2.5). In larval stage, TPT shortened the body length at ≥10μg/L and suppressed the swimming activity of the fish larvae at Day 1 post-hatching at 50μg/L. In reproductive stage, TPT exposure resulted in a male-biased sex ratio (2μg/L) and reduced the gonadosomatic index (GSI) in females (≥ 0.1μg/L), which might in turn lead to a decline in their population fitness. The reproductive stage of O. melastigma was more sensitive to TPT than other stages, while the GSI of female medaka was the most sensitive endpoint.

The effect of oil sands tailings pond sediments on embryo-larval walleye (Sander vitreus)

Walleye (Sander vitreus) are a commercially important North American fish species that inhabit the Athabasca River. This river flows through the Athabasca oil sands where natural sources of bitumen erode from the McMurray formation. Little information is available on responses of walleye embryos to oil sands tailings pond sediments in a laboratory setting. The current study describes the design and implementation of a daily-renewal bioassay to assess the potential effects of tailings pond sediments from the Athabasca oil sands area on walleye development. Developing walleye embryos were exposed to increasing concentrations of two tailings pond sediments (collected in the Athabasca oil sands area) until the completion of yolk absorption in control fish. Sediments from the tailings pond represent a mixture of polycyclic aromatic hydrocarbons (PAHs) and alkylated PAHs. During the 31 day exposure, the walleye were examined for mortalities, weight, length and developmental abnormalities to provide an initial evaluation of the effects of the oil sands tailings pond sediments. Walleye embryo survival differed between the tailings pond sediments, and survival decreased with increasing sediment concentration. Alkylated PAH content differed between the two tailings pond sediments and lower embryo survival corresponded to higher total and alkylated PAH content. Tailings pond sediment-exposed walleye exhibited a delay in development, as well as increased percentages of larvae with heart and yolk sac edema, and cranial and spinal malformations. These abnormalities in development are often associated with PAH and alkylated PAH exposure. This study provides an exposure design that can be used to assess sediment toxicity to early developmental stages of a fish species not commonly tested in the lab, and lays the groundwork for future studies with this and other difficult-to-culture species. These results offer information on the potential effects of tailings pond sediments containing PAH/alkylated PAH mixtures on walleye development and survival.

A comprehensive study of the toxicity of natural multi-contaminated sediments: New insights brought by the use of a combined approach using the medaka embryo-larval assay and physico-chemical analyses

Sediment compartment is a long term sink for pollutants and a secondary source of contamination for aquatic species. The abiotic factors controlling the bioavailability and thus the toxicity of complex mixtures of pollutants accumulated in sediments are poorly documented. To highlight the different factors influencing sediment toxicity, we identified and analyzed the physico-chemical properties, micro-pollutant contents, and toxicity level of six contrasted sediments in the Lot-Garonne continuum. Sediment toxicity was evaluated using the recently described Japanese medaka (Oryzias latipes) embryo-larval assay with direct exposure to whole sediment (MELAc). Multiple toxicity endpoints including embryotoxicity, developmental defects and DNA damage were analyzed in exposed embryos. Chemical analyses revealed significant variations in the nature and contamination profile of sediments, mainly impacted by metallic trace elements and, unexpectedly, polycyclic aromatic hydrocarbons. Exposure to sediments induced different toxic impacts on medaka early life stages when compared with the reference site. Principal component analysis showed that the toxic responses following exposure to sediments from the Lot River and its tributary were associated with micro-pollutant contamination: biometric measurements, hatching success, genotoxicity, craniofacial deformities and yolk sac malabsorption were specifically correlated to metallic and organic contaminants. Conversely, the main biological responses following exposure to the Garonne River sediments were more likely related to their physico-chemical properties than to their contamination level. Time to hatch, cardiovascular injuries and spinal deformities were correlated to organic matter content, fine particles and dissolved oxygen levels. These results emphasize the necessity of combining physico-chemical analysis of sediment with toxicity assessment to accurately evaluate the environmental risks associated with sediment contamination.

The Toxicity to Fish Embryos of PAH in Crude and Refined Oils

Oil spills are a potential threat to the recruitment and production of fish. Polycyclic aromatic hydrocarbons (PAH), particularly 3-5-ringed alkyl PAH, are components of oil that cause chronic embryotoxicity. Toxicity is related to molecular size and octanol-water partition coefficients (Kow), indicating that water-lipid partitioning controls exposure and tissue dose. Nevertheless, more than 25% of the variation in toxicity among congeners is unexplained. Congeners with the same number of rings, alkyl carbon atoms, and Kow, but different molecular shapes, have markedly different toxicities, likely due to differences in interactions with cellular receptors. The potentiation and antagonism of metabolism and toxicity in PAH mixtures suggest that measured effect concentrations for individual PAH are conservative. Because mixture interactions are not well understood, total PAH concentrations >0.1 µg/L following oil spills should be considered hazardous.

Comparative developmental toxicity of eight typical organic pollutants to red sea bream (Pagrosomus major) embryos and larvae

The red sea bream (Pagrosomus major) 48-h embryo-larval bioassay was used to assess and compare the developmental toxicities of eight typical organic pollutants, including polycyclic aromatic hydrocarbons (PAHs), organophosphorus pesticides, polychlorinated biphenyls (PCBs) and alkylphenol. Toxicological endpoints such as survival rates of P. major embryos or larvae and the rates of hatching and of malformation (oedema, condensed blood, spinal curvatures or eye abnormalities) were noted and described within 48 h of exposure. The LC₅₀, EC₅₀, no-observed-effect concentration (NOEC) and lowest-observed-effect concentration (LOEC) were calculated, based on the dose-response relationship. The results showed that exposures to all of the selected organic pollutants except for methyl parathion produced acute toxic effects on P. major embryos and larvae, at different levels of exposure. The levels of acute toxicity of the eight typical organic pollutants for P. major embryos and larvae showed the following trend: benzo(a)pyrene > malathion > PCB 126 > pyrene > nonylphenol > phenanthrene > monocrotophos > methyl parathion. However, the larvae were more sensitive to these pollutants than embryos, according to the calculated LC₅₀, EC₅₀, NOEC and LOEC. This increased sensitivity of larvae could have resulted from losing the natural barrier function of the egg shell membrane. Benzo(a)pyrene, malathion, nonylphenol and monocrotophos delayed the development of P. major for both embryos and larvae, and decreased the hatching rate of the embryos. These results implied that the development of fish embryos and larvae could serve as potential biomarkers for evaluating organic contamination in the aquatic environment. The marine economic fish P. major was more sensitive to PAHs than the model fish, marine medaka (Oryzias melastigma). The estimated safe concentrations (SCs) for marine economic fish, as determined in our research, could provide a reference for the formulation of water quality criteria.

Toxicity of oil sands acid-extractable organic fractions to freshwater fish: Pimephales promelas (fathead minnow) and Oryzias latipes (Japanese medaka)

The Alberta oil sands are one of the largest global petroleum deposits and, due to non-release practices for oil sands process-affected waters, produced tailings are stored in large ponds. The acid extractable organic (AEO) compounds in oil sands process-affected water are of greatest concern due to their persistence and toxicity to a variety of aquatic biota. The present study evaluated the toxicity of the five AEO fractions to two fish species: Oryzias latipes (Japanese medaka) and Pimephales promelas (fathead minnow). The fractions (F1-F5) were comprised of AEO with increasing mean molecular weight and subsequent increases in cyclicity, aromaticity, degree of oxygenation, and heteroatom content. The lowest molecular weight fraction, F1, displayed the lowest acute toxicity to both fish species. For fathead minnow, F5 displayed the greatest toxic potency, while F2 to F4 displayed intermediate toxicities. For Japanese medaka, F2 and F3 displayed the greatest acute toxicities and F1, F4 and F5 were significantly less potent. Overall, fathead minnow were more acutely sensitive to AEO than Japanese medaka. The present study indicates that AEO toxicity may not be solely driven by a narcotic mode of action, but chemical composition such as aromaticity and heteroatom content and their relation to toxicity suggest other drivers indicative of additional modes of toxic action.

The notochord curvature in medaka (Oryzias latipes) embryos as a response to ultraviolet A irradiation

In the present work, the destructive effects of ultraviolet A (UVA; 366nm) irradiation on the developmental stages of Japanese medaka (Oryzias latipes) are revealed in terms of hatching success, mortality rate, and morphological malformations (yolk sac edema, body curvature, fin blistering, and dwarfism). Fertilized eggs in stage 4 were exposed to 15, 30, and 60min/day UVA for 3days in replicates. Fish were staged and aged following the stages established by Iwamatsu [1]. We observed and recorded the hatching time and deformed and dead embryos continuously. The hatching time was prolonged and the deformed and dead embryos numbers were increased by UVA dose increase. At stage 40, samples from each group were fixed to investigate their morphology and histopathology. Some morphological malformations were recorded after UVA exposure in both strains. Histopathological changes were represented as different shapes of curvature in notochord with collapse. The degree of collapsation was depended on the dose and time of UVA exposure. Our findings show that exposure to UVA irradiation caused less vertebral column curvature in medaka fry. Moreover, p53-deficient embryos were more tolerant than those of wild-type (Hd-rR) Japanese medaka. This study indicated the dangerous effects of the UVA on medaka.

Toxicity assessment of water-accommodated fractions from two different oils using a zebrafish (Danio rerio) embryo-larval bioassay with a multilevel approach

Petroleum compounds from chronic discharges and oil spills represent an important source of environmental pollution. To better understand the deleterious effects of these compounds, the toxicity of water-accommodated fractions (WAF) from two different oils (brut Arabian Light and Erika heavy fuel oils) were used in this study. Zebrafish embryos (Danio rerio) were exposed during 96h at three WAF concentrations (1, 10 and 100% for Arabian Light and 10, 50 and 100% for Erika) in order to cover a wide range of polycyclic aromatic hydrocarbon (PAH) concentrations, representative of the levels found after environmental oil spills. Several endpoints were recorded at different levels of biological organization, including lethal endpoints, morphological abnormalities, photomotor behavioral responses, cardiac activity, DNA damage and exposure level measurements (EROD activity, cyp1a and PAH metabolites). Neither morphological nor behavioral or physiological alterations were observed after exposure to Arabian Light fractions. In contrast, the Erika fractions led a high degree of toxicity in early life stages of zebrafish. Despite of defense mechanisms induced by oil, acute toxic effects have been recorded including mortality, delayed hatching, high rates of developmental abnormalities, disrupted locomotor activity and cardiac failures at the highest PAH concentrations (∑TPAHs=257,029±47,231ng·L(-1)). Such differences in toxicity are likely related to the oil composition. The use of developing zebrafish is a good tool to identify wide range of detrimental effects and elucidate their underlying foundations. Our work highlights once more, the cardiotoxic action (and potentially neurotoxic) of petroleum-related PAHs.

Assessing Aromatic-Hydrocarbon Toxicity to Fish Early Life Stages Using Passive-Dosing Methods and Target-Lipid and Chemical-Activity Models

Aromatic hydrocarbons (AH) are known to impair fish early life stages (ELS). However, poorly defined exposures often confound ELS-test interpretation. Passive dosing (PD) overcomes these challenges by delivering consistent, controlled exposures. The objectives of this study were to apply PD to obtain 5 d acute embryo lethality and developmental data and 30 d chronic embryo-larval survival and growth-effects data using zebrafish with different AHs; to analyze study and literature toxicity data using target-lipid (TLM) and chemical-activity (CA) models; and to extend PD to a mixture and test the assumption of AH additivity. PD maintained targeted exposures over a concentration range of 6 orders of magnitude. AH toxicity increased with log Kow up to pyrene (5.2). Pericardial edema was the most sensitive sublethal effect that often preceded embryo mortality, although some AHs did not produce developmental effects at concentrations causing mortality. Cumulative embryo-larval mortality was more sensitive than larval growth, with acute-to-chronic ratios of <10. More-hydrophobic AHs did not exhibit toxicity at aqueous saturation. The relationship and utility of the TLM-CA models for characterizing fish ELS toxicity is discussed. Application of these models indicated that concentration addition provided a conservative basis for predicting ELS effects for the mixture investigated.

Physico-chemical properties and toxicity of alkylated polycyclic aromatic hydrocarbons

Crude oil and refined petroleum products contain many polycyclic and heterocyclic aromatic hydrocarbons, in particular, alkylated PAHs. Although alkylated PAHs are found in significantly higher quantities than their corresponding unsubstituted PAHs, the most studies on the physico-chemical properties and toxicities of these compounds have been conducted on unsubstituted PAHs. In this study, we measured crucial physico-chemical properties (i.e., water solubility, partition coefficients between polydimethylsiloxane and water (KPDMSw), and partition coefficient between liposomes and water (Klipw)) of selected alkylated PAHs, and evaluated their toxicity using the luminescence inhibition of Aliivibrio fischeri and growth inhibition of Raphidocelis subcapitata. In general, the logarithms of these properties for alkylated PAHs showed good linear correlations with log Kow, as did those for unsubstituted PAHs. Changes in molecular symmetry on the introduction of alkyl groups on aromatic ring structure significantly altered water solubility. The inhibition of bacterial luminescence and algal growth by alkylated PAHs can be explained well by the baseline toxicity hypothesis, and good linear relationships between log Kow or log Klipw and log (1/EC50) were found.

Measured and predicted affinities of binding and relative potencies to activate the AhR of PAHs and their alkylated analogues

Polycyclic aromatic hydrocarbons (PAHs) and their alkylated forms are important components of crude oil. Both groups of PAHs have been reported to cause dioxin-like responses, mediated by aryl hydrocarbon receptor (AhR). Thus, characterization of binding affinity to the AhR of unsubstituted or alkylated PAHs is important to understand the toxicological consequences of oil contamination on ecosystems. We investigated the potencies of major PAHs of crude oil, e.g., chrysene, phenanthrene and dibenzothiophene, and their alkylated forms (n=17) to upregulate expression of AhR-mediated processes by use of the H4IIE-luc transactivation bioassay. In addition, molecular descriptors of different AhR activation potencies among PAHs were investigated by use of computational molecular docking models. Based on responses of the H4IIE-luc in vitro assay, it was shown that potencies of PAHs were determined by alkylation in addition to the number and conformation of rings. Potencies of AhR-mediated processes were generally greater when a chrysene group was substituted, especially in 1-methyl-chrysene. Significant negative correlations were observed between the in vitro dioxin-like potency measured in H4IIE-luc cells and the binding distance estimated from the in silico modeling. The difference in relative potency for AhR activation observed among PAHs and their alkylated forms could be explained by differences among binding distances in the ligand binding domain of the AhR caused by alkylation. The docking model developed in the present study may have utility in predicting risks of environmental contaminants of which toxicities are mediated by AhR binding.

A novel solid-state fractionation of naphthenic acid fraction components from oil sands process-affected water

Various sorbent materials were evaluated for the fractionation of naphthenic acid fraction components (NAFCs) from oil sand process-affected water (OSPW). The solid phase materials include activated carbon (AC), cellulose, iron oxides (magnetite and goethite), polyaniline (PANI) and three types of biochar derived from biomass (BC-1; rice husks, BC-2; acacia low temperature and BC-3; acacia high temperature). NAFCs were semi-quantified using electrospray ionization high resolution Orbitrap mass spectrometry (ESI-MS) and the metals were assessed by inductively coupled plasma optical emission spectrometry (ICP-OES). The average removal efficacy of NAFCs by AC was 95%. The removal efficacy decreased in the following order: AC, BC-1>BC-2, BC-3, goethite>PANI>cellulose, magnetite. The removal of metals did not follow a clear trend; however, there was notable leaching of potassium by AC and biochar samples. The bound NAFCs by AC were desorbed efficiently with methanol. Methanol regeneration and recycling of AC revealed 88% removal on the fourth cycle; a 4.4% decrease from the first cycle. This fractionation method represents a rapid, cost-effective, efficient, and green strategy for NAFCs from OSPW, as compared with conventional solvent extraction.

Spilled Oils: Static Mixtures or Dynamic Weathering and Bioavailability?

Polynuclear aromatic hydrocarbons (PAHs) from sequestered MV Selendang Ayu oil were biologically available in 2008, 3.6 y after it was spilled along Unalaska Island, Alaska. Thermodynamically driven weathering was the most probable mechanism of organism exposure to PAHs. Alkane and PAH composition in oil changed over time as smaller constituents were preferentially lost, indicative of weathering. In contrast, composition of the largest compounds (biomarkers) including triterpanes, hopanes, and steranes remained unchanged. Smaller molecules (the PAHs) lost from stranded oil were observed in indigenous mussels and passive samplers deployed in July 2008. Concentration and composition of PAHs were significantly different than in a non-oiled reference area and patterns observed in mussels were repeated in passive samplers deployed in three zones (intertidal, subtidal, and water). Thus, hydrocarbons lost from one compartment (sequestered whole oil) were detectable in another (mussels and passive samplers) implying aqueous transfer. Quantities of mobile oil constituents were small, yielding uptake concentrations that are likely inconsequential for mussels, but the sensitivity provided by bioaccumulation and passive sampler uptake ensured that dissolved hydrocarbons were detectable.

Transcriptional responses and embryotoxic effects induced by pyrene and methylpyrene in Japanese medaka (Oryzias latipes) early life stages exposed to spiked sediments

Japanese medaka (Oryzias latipes) embryos were exposed to sediments spiked with environmental concentrations (300 and 3,000 ng/g dry weight) of pyrene (Pyr) and methylpyrene (MePyr) throughout their development. Embryotoxicity, teratogenicity, and transcriptional responses (qRT-PCR) were analyzed in embryos and newly hatched larvae. The genotoxicity of the two polycyclic aromatic hydrocarbons (PAHs) was also tested in prolarvae using the comet assay. Exposure to each compound had a clear impact on embryonic development and resulted in several teratogenic effects, including cardiovascular injuries, reduced absorption of yolk sac reserves, and jaw and spinal deformities. Interestingly, the overall toxic effects of Pyr and MePyr considerably overlapped those induced following dioxin exposure. qRT-PCR analysis revealed the transcriptional induction of genes involved in mitochondrial energetic metabolism (coxI), xenobiotic biotransformation (cyp1a), and cell cycle regulation (wnt1) by the two PAHs. MePyr also activated cell cycle arrest (p53), oxidative DNA damage repair (ogg1), and retinoid-mediated (raldh2 and rarα1) gene transcription. DNA damage was not found to be significantly increased following Pyr and MePyr exposure. The lack of significant genotoxic effect in comparison to the control might be the consequence of the efficient onset of DNA damage repair mechanisms as suggested by ogg1 gene transcription upregulation. Results reported in the present study have brought new insights into the modes of action of Pyr, and the effects of MePyr exposure have been investigated in fish ELS for the first time.

Developmental toxicity of PAH mixtures in fish early life stages. Part II: adverse effects in Japanese medaka

In aquatic environments, polycyclic aromatic hydrocarbons (PAHs) mostly occur as complex mixtures, for which risk assessment remains problematic. To better understand the effects of PAH mixture toxicity on fish early life stages, this study compared the developmental toxicity of three PAH complex mixtures. These mixtures were extracted from a PAH-contaminated sediment (Seine estuary, France) and two oils (Arabian Light and Erika). For each fraction, artificial sediment was spiked at three different environmental concentrations roughly equivalent to 0.5, 4, and 10 μg total PAH g(-1) dw. Japanese medaka embryos were incubated on these PAH-spiked sediments throughout their development, right up until hatching. Several endpoints were recorded at different developmental stages, including acute endpoints, morphological abnormalities, larvae locomotion, and genotoxicity (comet and micronucleus assays). The three PAH fractions delayed hatching, induced developmental abnormalities, disrupted larvae swimming activity, and damaged DNA at environmental concentrations. Differences in toxicity levels, likely related to differences in PAH proportions, were highlighted between fractions. The Arabian Light and Erika petrogenic fractions, containing a high proportion of alkylated PAHs and low molecular weight PAHs, were more toxic to Japanese medaka early life stages than the pyrolytic fraction. This was not supported by the toxic equivalency approach, which appeared unsuitable for assessing the toxicity of the three PAH fractions to fish early life stages. This study highlights the potential risks posed by environmental mixtures of alkylated and low molecular weight PAHs to early stages of fish development.

Methylated and unsubstituted polycyclic aromatic hydrocarbons in street dust from Vietnam and India: occurrence, distribution and in vitro toxicity evaluation

Methylated polycyclic aromatic hydrocarbons (MePAHs), unsubstituted PAHs and AhR-mediated activities were determined in street dust collected from Vietnam and India using a combined approach of chemical analysis and in vitro reporter gene assay. MePAHs and PAHs diagnostic ratios indicated that the main sources of MePAHs in Vietnam were pyrogenic emissions, whereas in India there were mixed sources of pyrogenic and petrogenic emissions. AhR-mediated activities determined by using DR-CALUX assay were observed in urban street dust at mean 40, 29 and 20 ng CALUX-TEQ/g dw for Hanoi, Bangalore and New Delhi, respectively. MePAHs and PAHs contributed only 5% or less to AhR-mediated activity in street dust, indicating the occurrence of unknown AhR agonists. The principal contributors to Theoretical-TEQs among target compounds were methyl benz[a]anthracene, benzo[b]- and benzo[k]fluoranthene. The present study indicates importance of MePAHs in evaluation of toxic risk related to AhR-mediated activity in urban polluted areas.

Distributions of polycyclic aromatic hydrocarbons and alkylated polycyclic aromatic hydrocarbons in Osaka Bay, Japan

Contaminations in sediments by polycyclic aromatic hydrocarbons (PAHs) and alkylated PAHs were investigated at 44 sites in Osaka Bay, Japan. Concentrations of total PAHs and alkylated PAHs were in the range 6.40-7800 ng/g dry weights and 13.7-1700 ng/g dry weights, respectively. The PAH concentrations tended to be higher along the shoreline in the vicinities of big ports, industrialized areas, and densely populated regions such as the cities of Osaka and Kobe. The major sources appeared to be pyrogenic or both pyrogenic and petrogenic at most of the sites. PAH concentrations were remarkably high at a site near Kobe, where the concentrations of dibenzo(a,h)anthracene and benzo(g,h,i)perylene exceeded the effects-range-medium concentration and eight PAHs were above the corresponding effects-range-low concentrations. Those PAHs may have been derived from the great fire associated with the large earthquake in 1995.

Exposure to low dose benzo[a]pyrene during early life stages causes symptoms similar to cardiac hypertrophy in adult zebrafish

Growing evidence indicates that polycyclic aromatic hydrocarbons (PAHs) can lead to cardiac hypertrophy and recent research indicates that exposure to low dose crude oil during early embryonic development may lead to impacts on heart health at later life stages. The aim of this study was to evaluate whether exposure during early life stages to low dose benzo[a]pyrene (BaP), as a high-ring PAH, would lead to cardiac hypertrophy at later life stages. Zebrafish were exposed to low dose BaP until 96 hpf, then transferred to clean water and maintained for a year before histological and molecular biological analysis. Our results showed that exposure to low level BaP during early life stages increased heart weight to body weight ratios and deposited collagen in the heart of adult zebrafish. ANP, BNP and c-Myc were also induced in the heart of adult zebrafish by BaP. These results proved that low level BaP exposure during early life stages caused symptoms similar to cardiac hypertrophy in adult zebrafish. Our results displayed an elevated expression of CdC42, RhoA, p-ERK1, 2 and Rac1. Therefore, the mechanism of the cardiac hypertrophy caused by BaP exposure during early life stages may be through inducing the expression of CdC42, RhoA and Rac1, together with activating ERK1, 2.