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In this study, marine medaka (Oryzias melastigma) embryos were exposed to different concentrations of water-accommodated fractions (WAFs) and chemically enhanced water-accommodated fractions (CEWAFs) of Oman crude oil for 14 d by semi-static exposure methods. The effects on growth and development and energy metabolism process were evaluated. Results showed that embryo survival and hatchability were decreased in a dose-dependent manner with an increase in the concentration of petroleum hydrocarbon compounds, whereas the malformation exhibited a dose-dependent increase. Compared to the control, the adenosine triphosphate (ATP) content and Na + -K + -ATPase (NKA) activities of embryos exposed to both WAFs and CEWAFs were reduced, while intracellular reactive oxygen species (ROS) levels and NADH oxidase (NOX) activities were increased. Our study demonstrated that exposure to crude oil dispersed by chemical dispersant affected the growth and development of marine medaka embryos, caused oxidative stress while produced a series of malformations in the body and dysregulation in energy metabolism. In comparison, the toxic effects of chemically dispersed crude oil might be more severe than the oil itself in the equivalent diluted concentration treatment solution. These would provide more valuable and reliable reference data for the use of chemical dispersants in oil spills., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier Ltd. All rights reserved.)

Multiple lines of evidence at whole animal, cellular and molecular levels implicate polycyclic aromatic compounds (PACs) with three rings as drivers of crude oil toxicity to developing fish. Phenanthrene (P0) and its alkylated homologs (C1- through C4-phenanthrenes) comprise the most prominent subfraction of tricyclic PACs in crude oils. Among this family, P0 has been studied intensively, with more limited detail available for the C4-phenanthrene 1-methyl-7-isopropyl-phenanthrene (1-M,7-IP, or retene). While both compounds are cardiotoxic, P0 impacts embryonic cardiac function and development through direct blockade of K + and Ca 2+ currents that regulate cardiomyocyte contractions. In contrast, 1-M,7-IP dysregulates aryl hydrocarbon receptor (AHR) activation in developing ventricular cardiomyocytes. Although no other compounds have been assessed in detail across the larger family of alkylated phenanthrenes, increasing alkylation might be expected to shift phenanthrene family member activity from K + /Ca 2+ ion current blockade to AHR activation. Using embryos of two distantly related fish species, zebrafish and Atlantic haddock, we tested 14 alkyl-phenanthrenes in both acute and latent developmental cardiotoxicity assays. All compounds were cardiotoxic, and effects were resolved into impacts on multiple, highly specific aspects of heart development or function. Craniofacial defects were clearly linked to developmental cardiotoxicity. Based on these findings, we suggest a novel framework to delineate the developmental toxicity of petrogenic PAC mixtures in fish, which incorporates multi-mechanistic pathways that produce interactive synergism at the organ level. In addition, relationships among measured embryo tissue concentrations, cytochrome P4501A mRNA induction, and cardiotoxic responses suggest a two-compartment toxicokinetic model that independently predicts high potency of PAC mixtures through classical metabolic synergism. These two modes of synergism, specific to the sub-fraction of phenanthrenes, are sufficient to explain the high embryotoxic potency of crude oils, independent of as-yet unmeasured compounds in these complex environmental mixtures., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Published by Elsevier B.V.)

Polycyclic aromatic compounds (PACs) present in the water column are considered to be one of the primary contaminant groups contributing to the toxicity of a crude oil spill. Because crude oil is a complex mixture composed of thousands of different compounds, oil spill models rely on quantitative structure-activity relationships like the target lipid model to predict the effects of crude oil exposure on aquatic life. These models rely on input provided by single species toxicity studies, which remain insufficient. Although the toxicity of select PACs has been well studied, there is little data available for many, including transformation products such as oxidized hydrocarbons. In addition, the effect of environmental influencing factors such as temperature on PAC toxicity is a wide data gap. In response to these needs, in the present study, Stage I lobster larvae were exposed to six different understudied PACs (naphthalene, fluorenone, methylnaphthalene, phenanthrene, dibenzothiophene, and fluoranthene) at three different relevant temperatures (10, 15, and 20 °C) all within the biological norms for the species during summer when larval releases occur. Lobster larvae were assessed for immobilization as a sublethal effect and mortality following 3, 6, 12, 24, and 48 h of exposure. Higher temperatures increased the rate at which immobilization and mortality were observed for each of the compounds tested and also altered the predicted critical target lipid body burden, incipient median lethal concentration, and elimination rate. Our results demonstrate that temperature has an important influence on PAC toxicity for this species and provides critical data for oil spill modeling. More studies are needed so oil spill models can be appropriately calibrated and to improve their predictive ability. Environ Toxicol Chem 2023;42:2389-2399. © 2023 SETAC., (© 2023 SETAC.)

Exposure characterization of crude oils, especially in time-sensitive circumstances such as spills and disasters, is a well-known analytical chemistry challenge. Gas chromatography-mass spectrometry is commonly used for "fingerprinting" and origin tracing in oil spills; however, this method is both time-consuming and lacks the resolving power to separate co-eluting compounds. Recent advances in methodologies to analyze petroleum substances using high-resolution analytical techniques have demonstrated both improved resolving power and higher throughput. One such method, ion mobility spectrometry-mass spectrometry (IMS-MS), is especially promising because it is both rapid and high-throughput, with the ability to discern among highly homologous hydrocarbon molecules. Previous applications of IMS-MS to crude oil analyses included a limited number of samples and did not provide detailed characterization of chemical constituents. We analyzed a diverse library of 195 crude oil samples using IMS-MS and applied a computational workflow to assign molecular formulas to individual features. The oils were from 12 groups based on geographical and geological origins: non-US (1 group), US onshore (3), and US Gulf of Mexico offshore (8). We hypothesized that information acquired through IMS-MS data would provide a more confident grouping and yield additional fingerprint information. Chemical composition data from IMS-MS was used for unsupervised hierarchical clustering, as well as machine learning-based supervised analysis to predict geographic and source rock categories for each sample; the latter also yielded several novel prospective biomarkers for fingerprinting of crude oils. We found that IMS-MS data have complementary advantages for fingerprinting and characterization of diverse crude oils and that proposed polycyclic aromatic hydrocarbon biomarkers can be used for rapid exposure characterization. Environ Toxicol Chem 2023;42:2336-2349. © 2023 The Authors. Environmental Toxicology and Chemistry published by Wiley Periodicals LLC on behalf of SETAC., (© 2023 The Authors. Environmental Toxicology and Chemistry published by Wiley Periodicals LLC on behalf of SETAC.)

Photochemical weathering transforms petroleum oil and changes its bulk physical properties, as well as its partitioning into seawater. This transformation process is likely to occur in a cold water marine oil spill, but little is known about the behavior of photochemically weathered oil in cold water. We quantified the effect of photochemical weathering on oil properties and partitioning across temperatures. Compared to weathering in the dark, photochemical weathering increases oil viscosity and water-soluble content, decreases oil-seawater interfacial tension, and slightly increases density. Many of these photochemical changes are much larger than changes caused by evaporative weathering. Further, the viscosity and water-soluble content of photochemically weathered oil are more temperature-sensitive compared to evaporatively weathered oil, which changes the importance of key fate processes in warm versus cold environments. Compared to at 30 °C, photochemically weathered oil at 5 °C would have a 16× higher viscosity and a 7× lower water-soluble content, resulting in lower entrainment and dissolution. Collectively, the physical properties and thus fate of photochemically weathered oil in a cold water spill may be substantially different from those in a warm water spill. These differences could affect the choice of oil spill response options in cold, high-light environments.

Oil dispersion by the application of chemical dispersants is an important tool in oil spill response, but it is difficult to quantify in the field in a timely fashion that is useful for coordinators and decision-makers. One option is the use of rugged portable field fluorometers that can deliver essentially instantaneous results if access is attainable. The United States Coast Guard has suggested, in their Special Monitoring of Applied Response Technologies (SMART) protocols, that successful oil dispersion can be identified by a five-fold increase in oil fluorescence. Here we test three commercial fluorometers with different excitation/emission windows (SeaOWL, Cyclops 7FO, and Cyclops 7F-G) that might prove useful for such applications. Results show that they have significantly different dynamic ranges for detecting oil and that using them (or similar instruments) in combination is probably the best option for successfully assessing the effectiveness of oil dispersion operations. Nevertheless, the rapid dilution of dispersed oil means that measurements must be made within an hour or two of dispersion, suggesting that one feasible scenario would be monitoring ship-applied dispersants by vessels following close behind the dispersant application vessel. Alternatively, autonomous submersibles might be pre-deployed to monitor aerial dispersant application, although the logistical challenges in a real spill would be substantial., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Crown Copyright © 2023. Published by Elsevier Ltd. All rights reserved.)

Despite their potential vulnerability to oil spills, little is known about the physiological effects of petroleum exposure and spill responses in cold-water marine animal larvae. We investigated the effects of physically dispersed (water-accommodated fraction, WAF) and chemically dispersed (chemically enhanced WAF, CEWAF; using Slickgone EW) conventional heavy crude oil on the routine metabolic rate and heart rate of stage I larval American lobster (Homarus americanus). We found no effects of 24-h exposure to sublethal concentrations of crude oil WAF or CEWAF at 12 °C. We then investigated the effect of sublethal concentrations of WAFs at three environmentally relevant temperatures (9, 12, 15 °C). The highest WAF concentration increased metabolic rate at 9 °C, whereas it decreased heart rate and increased mortality at 15 °C. Overall, metabolic and cardiac function of American lobster larvae is relatively resilient to conventional heavy crude oil and Slickgone EW exposure, but responses to WAF may be temperature-dependent., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 Elsevier Ltd. All rights reserved.)

Oil spills interact with mineral particles to form oil-particle aggregates (OPAs), which promotes the oil's natural diffusion and biodegradation. We investigated the effect of bacteria on the formation and vertical migration of OPAs under different concentrations and types of particles and proposed and elucidated an oil-particle-bacteria coupling mechanism. The depth of particle penetration into oil droplets (13-17 μm) was more than twice that of the nonbacterial group. Oil that remained in the water column and deposited to the bottom decreased from 87% to 49% and increased from 14% to 15% at high/low concentration, respectively. Interestingly, the median droplet diameter showed a negative correlation ( R 2 = 0.83) and positive correlation ( R 2 = 0.60) at high/low concentration, respectively, with the relative penetration depth first proposed. We further demonstrated that bacteria increased the penetrating depth by a combination of reducing/increasing the interfacial tension, reducing the oil amount (C 17 -C 38 ) in the OPAs, and increasing the particle width. These effects reduced the droplet size and ultimately changed the vertical migration of OPAs. Finally, we provided a simple assessment of the vertical distribution of OPAs in nearshore environments based on experimental data and suggested that the role of bacteria in increasing the depth of particles penetrating into the oil droplets should not be ignored. These findings will broaden the research perspective of marine oil spill migration.

Oil spill risk and impact assessments rely on time-dependent toxicity models to predict the hazard of the constituents that comprise crude oils and petroleum substances. Dissolved aromatic compounds (ACs) are recognized as a primary driver of aquatic toxicity in surface spill exposure scenarios. However, limited time-dependent toxicity data are available for different classes of ACs to calibrate such models. This study examined the acute toxicity of 14 ACs and 3 binary AC mixtures on Artemia franciscana nauplii at 25 °C. Toxicity tests for 3 ACs were also conducted at 15 °C to evaluate the role of temperature on toxicity. The ACs investigated represented parent and alkylated homocyclic and nitrogen-, sulfur- and oxygen-containing heterocyclic structures with octanol-water partition coefficients (log K ow ) ranging from 3.2 to 6.6. Passive dosing was used to expose and maintain concentrations in toxicity tests which were confirmed using fluorometry, and independently validated for 6 ACs using GC-MS analysis. Mortality was assessed at 6, 24, and 48 h to characterize the time course of toxicity. No mortality was observed for the most hydrophobic AC tested, 7,12-dimethylbenz[a]anthracene, due to apparent water solubility constraints. Empirical log LC 50 s for the remaining ACs were fit to a linear regression with log K ow to derive a critical target lipid body burden (CTLBB) based on the target lipid model. The calculated 48 h CTLBB of 47.1 ± 8.1 μmol/g octanol indicates that Artemia nauplii exhibited comparable sensitivity to other crustaceans. A steep concentration-response was found across all compounds as evidenced by a narrow range (1.0-3.1) in the observed LC 50 /LC 10 ratio. Differences in toxicokinetics were noted, and no impacts of temperature-dependence of AC toxicity were found. Toxicity data obtained for individual ACs yielded acceptable predictions of observed binary AC mixture toxicity. Results from this study advance toxicity models used in oil spill assessments., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2022. Published by Elsevier B.V.)

Bivalve mollusks including oysters have low metabolic potential and are therefore susceptible to accumulating high levels of lipophilic organic contaminants such as polycyclic aromatic hydrocarbons (PAHs). Human exposure to PAHs via consumption of this important commercial shellfish can be a serious public health concern in areas where high PAH contamination exists. Previous PAH immunohistochemical studies have been limited to laboratory-based exposures focusing on one or a few individual PAH compounds. To date, such studies have yet to explore PAH accumulation in oysters, known to have some of the highest levels of PAHs across different food products. Using a monoclonal antibody selective for a range of three- to five-ring PAHs, we present a method to detect and localize complex mixtures of PAHs in oyster tissues via fluorescent immunohistochemistry. Observed immunofluorescence intensity followed a similar trend as measured levels of PAHs in oyster interstitial fluid from PAH-contaminated sites and oysters exposed to the water accommodated fraction of crude oil. This method will be valuable in understanding internal partitioning mechanisms of PAH-exposed oysters and will have important applications in studies on PAH distribution in the tissues of additional organisms for environmental, medical, or veterinary purposes. Environ Toxicol Chem 2023;42:475-480. © 2022 The Authors. Environmental Toxicology and Chemistry published by Wiley Periodicals LLC on behalf of SETAC., (© 2022 The Authors. Environmental Toxicology and Chemistry published by Wiley Periodicals LLC on behalf of SETAC.)

Analytical techniques for chemical analysis of oil, oil photochemical and biological transformation products, and dispersants and their biodegradation products benefited significantly from research following the 2010 Deepwater Horizon (DWH) disaster. Crude oil and weathered-oil matrix reference materials were developed based on the Macondo well oil and characterized for polycyclic aromatic hydrocarbons, hopanes, and steranes for use to assure and improve the quality of analytical measurements in oil spill research. Advanced gas chromatography (GC) techniques such as comprehensive two-dimensional GC (GC × GC), pyrolysis GC with mass spectrometry (MS), and GC with tandem MS (GC-MS/MS) provide a greater understanding at the molecular level of composition and complexity of oil and weathering changes. The capabilities of high-resolution MS (HRMS) were utilized to extend the analytical characterization window beyond conventional GC-based methods to include polar and high molecular mass components (>400 Da) and to provide new opportunities for discovery, characterization, and investigation of photooxidation and biotransformation products. Novel separation approaches to reduce the complexity of the oil and weathered oil prior to high-resolution MS and advanced fluorescence spectrometry have increased the information available on spilled oil and transformation products. HRMS methods were developed to achieve the required precision and sensitivity for detection of dispersants and to provide molecular-level characterization of the complex surfactants. Overall, research funding following the DWH oil spill significantly advanced and expanded the use of analytical techniques for chemical analysis to support petroleum and dispersant characterization and investigations of fate and effects of not only the DWH oil spill but future spills.

Pipelines carrying diluted bitumen (dilbit) traverse North America and may result in dilbit release into sensitive freshwater ecosystems. To better understand the potential effects of a freshwater oil release, the Boreal-lake Oil Release Experiment by Additions to Limnocorrals project at the International Institute for Sustainable Development-Experimental Lakes Area (Ontario, Canada) modeled seven dilbit spills contained within a 10-m diameter of littoral limnocorrals in a boreal lake. Wild finescale dace (Phoxinus neogaeus) were released in the limnocorrals 21 days after oil addition and remained there for 70 days. Dilbit volumes covered a large range representing a regression of real spill sizes and total polycyclic aromatic compounds (TPAC) between 167 ng L -1  day -1 and 1989 ng L -1  day -1 . We report the effects of chronic exposure on reproductive potential as well as physiological responses in the gallbladder and liver. In exposures >1000 ng L -1  day -1 , there was a significant decrease in fish retrieval, culminating in zero recapture from the three highest treatments. Among the fish from the limnocorrals with lower levels of TPAC (<500 ng L -1  day -1 ), effects were inconsistent. Gallbladder bile fluorescence for a naphthalene metabolite was significantly different in fish from the oil-exposed limnocorrals when compared to the lake and reference corral, indicating that fish in these lower exposures were interacting with dilbit-derived polycyclic aromatic compounds. There were no significant differences in condition factor, somatic indices, or hepatocyte volume indices. There were also no significant changes in the development of testes or ovaries of exposed dace. The results from the present study may serve to orient policymakers and emergency responders to the range of TPAC exposures that may not significantly affect wild fish. Environ Toxicol Chem 2022;41:2745-2757. © 2022 SETAC., (© 2022 SETAC.)

Traditional approaches toward evaluating oil spill mitigation effectiveness in drinking water supplies using analytical chemistry can overlook residual hydrocarbons and treatment byproducts of unknown toxicity. Zebrafish (Danio rerio) were used to address this limitation by evaluating the reduction in toxicity to fish exposed to laboratory solutions of dissolved crude oil constituents treated with 3 mg/L ozone (O 3 ) with or without a peroxone-based advanced oxidation process using 0.5 M H 2 O 2 /M O 3 or 1 M H 2 O 2 /M O 3 . Crude oil water mixtures (OWMs) were generated using three mixing protocols-orbital (OWM-Orb), rapid (OWM-Rap), and impeller (OWM-Imp) and contained dissolved total aromatic concentrations of 106-1019 µg/L. In a first experiment, embryos were exposed at 24 h post fertilization (hpf) to OWM-Orb or OWM-Rap diluted to 25%-50% of full-strength samples and in a second experiment, to untreated or treated OWM-Imp mixtures at 50% dilutions. Toxicity profiles included body length, pericardial area, and swim bladder inflation, and these varied depending on the OWM preparation, with OWM-Rap resulting in the most toxicity, followed by OWM-Imp and then OWM-Orb. Zebrafish exposed to a 50% dilution of OWM-Imp resulted in 6% shorter body length, 83% increased pericardial area, and no swim bladder inflation, but exposure to a 50% dilution of OWM-Imp treated with O 3 alone or with 0.5 M H 2 O 2 /M O 3 resulted in normal zebrafish development and average total aromatic destruction of 54%-57%. Additional aromatic removal occurred with O 3  + 1 M H 2 O 2 /M O 3 but without further attenuation of toxicity to zebrafish. This study demonstrates using zebrafish as an additional evaluation component for modeling the effectiveness of freshwater oil spill treatment methods. Environ Toxicol Chem 2022;41:2822-2834. © 2022 SETAC., (© 2022 SETAC.)

Understanding the fate and behavior of spilled oil on the shoreline is crucial for helping decision-makers make trade-offs between natural attenuation and shoreline treatments. In this study, primary processes of oil attenuation and translocation on the shoreline, including penetration, washout, and biodegradation, have been considered to develop a numerical model, Shoreline Oil Spill Model (SOSM), for predicting the fate of spilled oil in various shoreline geological compartments. A holistic system design is employed to develop a user-friendly graphical interface system for SOSM. Global and local sensitivity analyses are used to examine the importance of the input factors on different outputs in SOSM. The results of the sensitivity analysis indicate that the input of oil spill mass correlates positively with the oil retention and surface and subsurface oil mass, while the oil concentration and penetration depth are sensitive to the grain size of the beach sediment. Subsequently, the SOSM is tested to hindcast the fate of stranded oil from the Exxon Valdez oil spill. Reasonable validation results have been obtained for the study site. It confirms the utility of the SOSM to examine and predict the level of shoreline oil contamination in the field following accidental spill events., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2022 Elsevier B.V. All rights reserved.)

Effect of oil spills on living forms demands for safe, ecofriendly and cost-effective methods to repair the damage. Pseudomonads have exceptional tolerance to xenobiotics and can grow at varied environmental conditions. This study aims at biosurfactant mediated degradation of petroleum crude oil by an indigenous Pseudomonas sp. WD23 in sea water. Pseudomonas sp. WD23 degraded 34% of petroleum crude oil (1.0% v/v) on supplementation of yeast extract (0.05 g/L) with glucose (1.0 g/L) in seawater. The strain produced a biosurfactant which was confirmed as a rhamnolipid (lipid: rhamnose 1:3.35) by FT-IR, LCMS and quantitative analysis. Produced rhamnolipid had low CMC (20.0 mg/L), emulsified petroleum oils (75-80%) and had high tolreance to varied conditions of pH, temperature and ionic strength. OFAT studies were performed to analyse the effect of petroleum crude oil, glucose, inoculum, yeast extract, pH, agitation speed and incubation time on degradation by Pseudomonas sp. WD23. Petroleum crude oil and glucose had significant effect on biodegradation, rhamnolipid production and growth, further optimized by central composite design. At optimum conditions of 3.414% v/v PCO and 6.53 g/L glucose, maximum degradation of 81.8 ± 0.67% was observed at pH 7.5, 100 RPM, 15.0% v/v inoculum in 28 days, with a 3-fold increase in biodegradation. GCMS analysis revealed degradation (86-100%) of all low and high molecular weight hydrocarbons present in petroleum crude oil. Hence, the strain Pseudomonas sp. WD23 can be effectively developed for management of oil spills in seas and oceans due to its excellent degradation abilities., (Copyright © 2022 Elsevier Ltd. All rights reserved.)

The Niger Delta region in South-South Nigeria, on Africa's West Coast, is densely populated. The region, which contains a substantial stock of crude oil and natural gas, has been nicknamed "the engine room" for Nigeria's economic development and progress. It is responsible for up to 90% of the country's economic growth (or gross domestic product/GDP). The region has multiple ecosystems, such as the aquatic environment, that are critical to the survival of the area's various habitats and living species. However, the same region has witnessed unjustifiable environmental pollution arising from oil activities over the years of exploration and production which has orchestrated negative consequences on the Niger Delta ecosystem. This has led to extended negative consequences on natural resources, which also have detrimental repercussions psychologically, ecologically, socially, economically, and physically which, in turn, impacts the overall health of the affected individuals. This write-up provides an overview of the major drivers of the oil leakage in Nigeria's Niger Delta ecosystem as well as the major impacts on the environment. It will also analyze numerous means of remediation in use and extend such for a more inclusive and productive option. Moreover, this review offers key measures that may help to maintain long-term policies for reducing adverse implications and increasing the living standard for the Niger Delta area's affected communities., (© 2022. The Author(s), under exclusive licence to Springer Nature Switzerland AG.)

The use of oil-soaked sorbents in the recovery and cleaning of oil spills presents challenges due to disposal. Recently, magnetic nanoparticle (MNP) based collection has been gaining interest as a new technique to lower the amount of labor required to treat oil spills. In this study, we devised a new method for the preparation of a magnetic nanoparticle (MNP) embedded polycaprolactone (PCL) sorbent with oleophilic and environmentally friendly features, capable of bring easily collected under a magnetic field. Compared with conventional polypropylene sorbents, the MNP embedded PCL sorbent (MNP/PCL) displayed excellent Arabian light (AL) crude oil sorption capacity (45.7 g g -1 ) and decreased the absorption time of the oil-soaked sorbent due to its electrospun structure and efficient distribution of hydrophobic MNPs. Furthermore, the MNP/PCL based sorbent became fully pyrolyzed under certain temperatures and conditions. The MNP embedded PCL-based sorbent demonstrated broad applicability and utility in large scale oil spill projects., (Copyright © 2022. Published by Elsevier Ltd.)

Rationale: The 2010 Deepwater Horizon (DWH) oil spill response and cleanup (OSRC) workers were exposed to airborne total hydrocarbons (THC), benzene, toluene, ethylbenzene, o-, m-, and p-xylenes and n-hexane (BTEX-H) from crude oil and PM 2 .5 from burning/flaring oil and natural gas. Little is known about asthma risk among oil spill cleanup workers., Objectives: We assessed the relationship between asthma and several oil spill-related exposures including job classes, THC, individual BTEX-H chemicals, the BTEX-H mixture, and PM 2.5 using data from the Gulf Long-Term Follow-up (GuLF) Study, a prospective cohort of 24,937 cleanup workers and 7,671 nonworkers following the DWH disaster., Methods: Our analysis largely focused on the 19,018 workers without asthma before the spill who had complete exposure, outcome, and covariate information. We defined incident asthma 1-3 years following exposure using both self-reported wheeze and self-reported physician diagnosis of asthma. THC and BTEX-H were assigned to participants based on measurement data and work histories, while PM 2.5 used modeled estimates. We used modified Poisson regression to estimate risk ratios (RR) and 95% confidence intervals (CIs) for associations between spill-related exposures and asthma and a quantile-based g-computation approach to explore the joint effect of the BTEX-H mixture on asthma risk., Results: OSRC workers had greater asthma risk than nonworkers (RR: 1.60, 95% CI: 1.38, 1.85). Higher estimated THC exposure levels were associated with increased risk in an exposure-dependent manner (linear trend test p < 0.0001). Asthma risk also increased with increasing exposure to individual BTEX-H chemicals and the chemical mixture: A simultaneous quartile increase in the BTEX-H mixture was associated with an increased asthma risk of 1.45 (95% CI: 1.35,1.55). With fewer cases, associations were less apparent for physician-diagnosed asthma alone., Conclusions: THC and BTEX-H were associated with increased asthma risk defined using wheeze symptoms as well as a physician diagnosis., (Published by Elsevier Ltd.)

Oil spills are a significant stressor to coastal and maritime environments worldwide. The growth responses of Batis maritima and Avicennia germinans seedlings to weathered Deepwater Horizon oiling were assessed through a mesocosm study using a factorial arrangement of 4 soil oiling levels (0 L m -2 , 1 L m -2 , 2 L m -2 , 4 L - m -2 ) × 3 tissue oiling levels (0% of stem height, 50% of stem height, 100% of stem height). Overall, growth metrics of B. maritima displayed much greater sensitivity to both tissue and soil oiling than A. germinans, which exhibited a relatively high tolerance to both routes of oiling exposure. Batis maritima in the 4 L m -2 soil oiling treatment demonstrated significant reductions in cumulative stem height and leaf number, whereas no significant effects of soil oiling on A. germinans were detected. This was reflected in the end of the study biomass partitioning, where total aboveground and live aboveground biomass were significantly reduced for B. maritima with 4 L m -2 soil oiling, but no impacts to A. germinans were found. Tissue oiling of 100% did appear to reduce B. maritima stem diameter, but no effect of tissue oiling was discerned on biomass partitioning, suggesting that there were no impacts to integrated growth. These findings suggest that B. maritima would be more severely affected by moderate soil oiling than A. germinans., (© 2022. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.)

The offshore oil industry in Atlantic Canada necessitates a greater understanding of the potential impacts of oil exposure and spill response measures on cold-water marine species. We used a standardized scoring index to characterize sublethal developmental impacts of physically and chemically dispersed crude oil in early life stages of Atlantic cod (Gadus morhua) and assessed intraspecific variation in the response among cod families. Cod (origin: Scotian Shelf, Canada) were laboratory-crossed to produce embryos from five specific families, which were subsequently exposed prehatch to gradient dilutions of a water-accommodated fraction (WAF) and a chemically enhanced WAF (CEWAF; prepared with Corexit 9500A) for 24 h. Postexposure, live embryos were transferred into filtered seawater and monitored to hatch; then, all live fish had sublethal endpoints assessed using the blue-sac disease (BSD) severity index. In both WAF and CEWAF groups, increasing exposure concentrations (measured as total petroleum hydrocarbons) resulted in an increased incidence of BSD symptoms (impaired swimming ability, increased degree of spinal curvature, yolk-sac edemas) in cod across all families. This positive concentration-dependent increase in BSD was similar between physically (WAF) versus chemically (CEWAF) dispersed oil exposures, indicating that dispersant addition does not exacerbate the effect of crude oil on BSD incidence in cod. Sensitivity varied between families, with some families having less BSD than others with increasing exposure concentrations. To our knowledge, our study is the first to demonstrate the occurrence in fishes of intraspecific variation among families in sublethal responses to oil and dispersant exposure. Our results suggest that sublethal effects of crude oil exposure will not be uniformly observed across cod populations and that sensitivity depends on genetic background. Environ Toxicol Chem 2022;41:1967-1976. © 2022 SETAC., (© 2022 SETAC.)

Following spills into water, petroleum oils can spread widely and produce surface slicks. Resulting slicks may impede volatilization and possibly increase chemical persistence in water. While the influence of oil films on chemical air-water exchange has been examined through theoretical and laboratory studies, field studies have not been conducted to assess the relevance of these effects following actual oil spill events. Here we evaluated the effect of diluted bitumen (dilbit) experimentally spilled in limnocorrals installed in a boreal lake on the volatilization of sulfur hexafluoride (SF 6 ), a non-reactive volatile tracer gas. Dilbit spills were monitored over 70 days and SF 6 was introduced twice (after 7 and 48 days) to evaluate the influence of spilled dilbit on the loss of SF 6 from water. Volatilization rate constants of SF 6 (k VOL ) significantly decreased by up to 80% with increasing total dilbit spill cover. Using a theoretical equation, decreases in k VOL were largely explained by a reduction in open water area where chemical exchange across the air-water interface occurs. Apparent effects of the slick on SF 6 mass transfer were estimated to be smaller by comparison (20%).To account for this reduction in volatilization, oil spill fate models should include a correction to consider the impact of spill cover on the air-water exchange of organic chemicals., (Copyright © 2021 Elsevier Ltd. All rights reserved.)

The copepod Calanus finmarchicus is an ecologically important species in the North Atlantic, Norwegian and Barents seas. Accidental or continuous petroleum pollution from oil and gas production in these seas may pose a significant threat to this low trophic level keystone species. Responses related to oxidative stress, protein damage and lipid peroxidation were investigated in C. finmarchicus exposed to a water-accommodated fraction (WAF) of a naphthenic North Atlantic crude oil. The exposure concentration corresponded to 50% of the 96 h LC 50 , and samples were obtained at 0, 24, 48, 72 and 96 h after exposure initiation. Gene expressions (superoxide dismutase, catalase, glutathione S-transferase, glutathione synthetase, heat shock protein 70 and 90, ubiquitin and cytochrome P-450 330A1), enzyme activities (superoxide dismutase, catalase, glutathione S-transferase) and concentrations of total glutathione and malondialdehyde were analyzed. Gene expression analyses showed no differences between controls and the exposed animals, however significantly higher glutathione S-transferase activity and malondialdehyde concentrations were found in the exposed group, suggests lipid peroxidation as main toxic effect., Competing Interests: Declaration of competing interest We hereby declare that none of the authors of manuscript ‘Oil-mediated oxidative-stress responses in a keystone zooplanktonic species, Calanus finmarchicus’ have conflict of interests whatsoever., (Copyright © 2021 Elsevier B.V. All rights reserved.)

Breeding birds that become oiled may contaminate the shells of their eggs, and studies of conventional crude oil suggest that even small quantities can be absorbed through the eggshell and cause embryotoxicity. Unconventional crude oils remain untested, so we evaluated whether a major Canadian oil sands product, diluted bitumen (dilbit), would be absorbed and cause toxicity when applied to eggshells of two species, domestic chicken (Gallus gallus domesticus) and double-crested cormorant (Nannopterum auritum). We artificially incubated eggs and applied lightly weathered dilbit (Cold Lake blend) to the eggshells (0.015-0.15 mg g -1 egg in chicken; 0.1-0.4 mg g -1 egg in cormorant) at various points during incubation before sampling prehatch embryos. Polycyclic aromatic compound (PAC) residue in cormorant embryos was elevated only at the highest dilbit application (0.4 mg g -1 egg) closest (day 16) to sampling on day 22. In contrast, cormorant liver cytochrome P450 1a4 (Cyp1a4) mRNA expression (quantitative polymerase chain reaction assay) was elevated only in embryos treated with the earliest and lowest dilbit application (0.1 mg g -1 egg on day 4). These results confirm that dilbit can cross through the eggshell and be absorbed by embryos, and they imply rapid biotransformation of PACs and a nonmonotonic Cyp1a4 response. Despite evidence of exposure in cormorant, we found no detectable effects on the frequency of survival, deformity, and gross lesions, nor did we find effects on physiological endpoints indicative of growth and cardiovascular function in either chicken or cormorant. In ovo dilbit exposure may be less toxic than well-studied conventional crude oils. The effects of an oil spill scenario involving dilbit to bird embryos might be subtle, and PACs may be rapidly metabolized. Environ Toxicol Chem 2022;41:159-174. © 2021 The Authors. Environmental Toxicology and Chemistry published by Wiley Periodicals LLC on behalf of SETAC., (© 2021 The Authors. Environmental Toxicology and Chemistry published by Wiley Periodicals LLC on behalf of SETAC.)

Accidents involving fuels and oil spills are among the main sources of hydrocarbons to the marine ecosystems and often damage the biota. Diesel and bunker oil are two examples of fuels with broad application that release hydrocarbons to the aquatic environment and little is known about their toxicity on tropical organisms. This study aimed to assess the toxicity of the water-soluble fraction (WSF) of diesel and bunker oils to neotropical marine invertebrates. Commercial fuels were purchased for WSF extraction, analyzed for total petroleum hydrocarbons (TPH), and polycyclic aromatic hydrocarbons (PAHs), and acute and chronic toxicity determined. The WSF analyzed contained varied levels of TPH and PAHs mixtures, especially low molecular weight PAHs; bunker WSF presented higher amounts of TPH and PAHs. Both WSFs tested produced significant mortality of the brine shrimp Artemia salina, affected the reproduction rate of the copepod Nitokra sp, and impaired the embryo-larval development of the mussel Perna perna and of the sea urchin Lytechinus variegatus. In general WSF from diesel was more toxic to the organisms tested, but bunker WSF was more toxic to embryos of L. variegatus. Toxicity started from concentrations of 3% WSF, which can be environmentally relevant after an oil spill, indicating that marine biota may be adversely affected in short term., (© 2021. The Author(s), under exclusive licence to Springer Science+Business Media, LLC, part of Springer Nature.)

After the Deepwater Horizon oil spill in 2010, toxicity tests were conducted using 4 microalgae (Dunaliella tertiolecta, Skeletonema costatum, Isochrysis galbana, and Thalassiosira pseudonana) and one macroalga (Ectocarpus siliculosus) to study potential impacts on phytoplankton and other primary producers in the Gulf of Mexico and characterize species sensitivity. Tests were performed with Corexit 9500 and fresh source oil and weathered oil samples collected from the field during the Deepwater Horizon oil spill. Because crude oils are mixtures of poorly water-soluble hydrocarbons, dosing was performed using water-accommodated fractions (WAFs) and chemically enhanced (CE) WAFs with the addition of dispersant at a 1:20 dispersant:oil ratio using standard toxicity testing protocols. Exposure media were analyzed for volatile organic compounds, parent and alkylated polycyclic aromatic hydrocarbons, and saturated hydrocarbon compounds. Toxicity was reported as no-observable effect concentration and median effect concentration (EC50) values for average specific growth rate based on nominal percent dilution of stock solution WAFs and sum of dissolved oil toxic units for WAF/CEWAF tests. The macroalga and green alga D. tertiolecta were largely unaffected by any WAF or CEWAFs tested. Isochrysis galbana was found to be the most sensitive species overall with significant growth rate inhibitions for dispersant and all the WAFs/CEWAFs tested. Physically dispersed source oils were generally more toxic than weathered oils. The protectiveness of the chronic toxic units was effective at identifying observed algal growth rate inhibitions across algal species and oil types despite the impact of dispersants.  Environ Toxicol Chem 2021;40:2742-2754. © 2021 SETAC., (© 2021 SETAC.)

Monterey formation crude oil spilled from an onshore pipeline and entered the surf zone near Refugio State Beach, Santa Barbara County, California (USA) on 19 May 2015. During this season, early life stages of many marine fish and invertebrates were present. Surf zone water and beach porewater samples were collected during the 4 mo after the spill and 2 yr later for chemical analyses. Elevated polycyclic aromatic hydrocarbon (PAH) and total petroleum hydrocarbon concentrations were observed in surf zone water and porewater near the release point, declining with distance and time. Early life stage toxicity was investigated by conducting 6- and 7-d static renewal bioassays with sand crab (Emerita analoga) post larvae (megalopae) and inland silverside larvae (Menidia beryllina), respectively, and a 48-h blue mussel (Mytilus sp.) embryo development bioassay. Dilutions of a high-energy water accommodated fraction of the Refugio Beach oil and a seawater control were prepared to simulate surf zone PAH concentrations (nominal PAH 45 ; 0, 0.5, 1, 5, 10, 50, 100, and 500 µg/L). The PAH 45 median lethal concentrations (LC50s), based on measured concentrations, were 381 µg/L for Mytilus sp., 75.6 µg/L for Menidia, and 40.9 µg/L for Emerita. Our results suggest that PAH concentrations in coastal waters of the spill-affected area were potentially lethal to early life stages of fish and invertebrates. Environ Toxicol Chem 2021;40:2578-2586. © 2021 SETAC., (© 2021 SETAC.)

Terrestrial, marine, or aquatic oil spills can directly or indirectly contaminate bird eggs. We hypothesized that chicken embryos exposed to crude oil can physiologically compensate to mitigate the potentially toxic effect of lower doses of oil. Embryos exposed to 0, 1, 3, or 5 µL of oil on embryonic days 4 and 10 were initially analyzed for mortality. All oil doses decreased day 4 embryo survival, but only the 2 highest oil doses lowered survival when applied on day 10. Thus, day 15 embryos treated with 1, 3, and 5 µL of source oil on day 10 had arterialized blood analyzed. The hematological variables hematocrit, red blood cell concentration ([RBC]), and hemoglobin concentration increased in response to 1 µL, were unchanged by 3 µL, and decreased by 5 µL of oil treatment. No changes occurred in arterialized blood gas variables (partial pressure of O 2 [PO 2 ], pH, bicarbonate concentration) for 1 and 3 µL embryos, but 5 µL of oil decreased PO 2 and caused metabolic acidosis. Increased blood lactate in embryos treated with 3 and 5 µL of oil was correlated with decreased hematocrit and [RBC] and increased body mass, the latter likely reflecting edema. We conclude that embryos in middle development physiologically compensated for negative effects of lower doses of crude oil but that higher doses of oil were harmful to the embryos at all developmental stages. Environ Toxicol Chem 2021;40:2347-2358. © 2021 SETAC., (© 2021 SETAC.)

There is a growing awareness that transient, sublethal embryonic exposure to crude oils cause subtle but important forms of delayed toxicity in fish. While the precise mechanisms for this loss of individual fitness are not well understood, they involve the disruption of early cardiogenesis and a subsequent pathological remodeling of the heart much later in juveniles. This developmental cardiotoxicity is attributable, in turn, to the inhibitory actions of crude oil-derived mixtures of polycyclic aromatic compounds (PACs) on specific ion channels and other proteins that collectively drive the rhythmic contractions of heart muscle cells via excitation-contraction coupling. Here we exposed Pacific herring (Clupea pallasi) embryos to oiled gravel effluent yielding ΣPAC concentrations as low as ~ 1 μg/L (64 ng/g in tissues). Upon hatching in clean seawater, and following the depuration of tissue PACs (as evidenced by basal levels of cyp1a gene expression), the ventricles of larval herring hearts showed a concentration-dependent reduction in posterior growth (ballooning). This was followed weeks later in feeding larvae by abnormal trabeculation, or formation of the finger-like projections of interior spongy myocardium, and months later with hypertrophy (overgrowth) of the spongy myocardium in early juveniles. Given that heart muscle cell differentiation and migration are driven by Ca 2+ -dependent intracellular signaling, the observed disruption of ventricular morphogenesis was likely a secondary (downstream) consequence of reduced calcium cycling and contractility in embryonic cardiomyocytes. We propose defective trabeculation as a promising phenotypic anchor for novel morphometric indicators of latent cardiac injury in oil-exposed herring, including an abnormal persistence of cardiac jelly in the ventricle wall and cardiomyocyte hyperproliferation. At a corresponding molecular level, quantitative expression assays in the present study also support biomarker roles for genes known to be involved in muscle contractility (atp2a2, myl7, myh7), cardiomyocyte precursor fate (nkx2.5) and ventricular trabeculation (nrg2, and hbegfa). Overall, our findings reinforce both proximal and indirect roles for dysregulated intracellular calcium cycling in the canonical fish early life stage crude oil toxicity syndrome. More work on Ca 2+ -mediated cellular dynamics and transcription in developing cardiomyocytes is needed. Nevertheless, the highly specific actions of ΣPAC mixtures on the heart at low, parts-per-billion tissue concentrations directly contravene classical assumptions of baseline (i.e., non-specific) crude oil toxicity., (Copyright © 2021. Published by Elsevier B.V.)

Mathematical simulation of oil permeation through the porous media is the crucial topical problem in the framework of localization and liquidation of emergency oil spills. The main objective of this study was to establish the oil contamination level and oil contamination depth for different soil types which is of particular relevance from the standpoint of environmental safety. Four types of soils were taken for investigation as follows Cambisol with sand texture (No. 1), Luvisol (gray forest), with loamy sand texture (No. 2), Black Typical Chernozem with sandy loam texture (No. 3), Kastanozem (pine forest terrace under the pines) with sand texture (No. 4). The task of predicting the temporal-spatial indicators of oil permeation in the soil during accidental spills was solved using ANSYS CFX software allowing to simulate the absorption amount of oil into the ground. Visualization of oil concentration and velocity for studied soil samples was carried out. Determination of petroleum hydrocarbons concentration by the gravimetric method indicated a direct correlation between oil content in the soil and the porosity of the investigated soil samples. In order to determine the rate of hydrocarbon permeation through the dry and wet soil layer comparative experiments were carried out for the following systems: oil - dry soil and oil - wet soil. Permeation coefficients for dry samples from No. 1 to No. 4 were set at the rate 0.0073 m ∙ day -1 , 0.0077 m ∙ day -1 , 0.0083 m ∙ day -1 , 0.0067 m ∙ day -1 respectively, and for wet soils 0.0083 m ∙ day -1 , 0.0093 m ∙ day -1 , 0.0093 m ∙ day -1 , 0.0083 m ∙ day -1 consequently. The obtained hydrocarbon permeation coefficients for different systems allow calculating the depth of oil penetration for a given time after the spill, taking into account soil moisture. The dependence of oil concentration and permeation rate distribution through the soil fully reflects reliability of the experimental data, thereby confirming the verification of the adequacy of the computer model based on the ANSYS CFX software., (Copyright © 2021 Elsevier Ltd. All rights reserved.)

Physical impacts of diluted bitumen (dilbit) and the application of surface washing agents (SWAs) in freshwater have not been characterized for aquatic invertebrates. These compounds are known to reduce surface tension in feather and fur microstructures of birds and mammals, and are thus likely to affect the buoyancy of surface-dwelling aquatic insects. We evaluated impacts of fresh dilbit and a SWA on water striders (Metrobates sp.), which are surface-dwelling organisms that rely on fine-hair microstructures to remain buoyant. We report nominal sheen thickness values that cause 50% immobility in 48 h as determined from exposure studies in outdoor tanks. A comparison of our data with those from historic oil spill volumes in Canada and the United States in the past 12 yr indicates that our reported nominal sheen thicknesses could have been reached or exceeded in 99% of historic spills when scaled to a small reference lake. The addition of Corexit EC9580A, a SWA approved for marine use in Canada, led to 100% immobility in striders within minutes, both in combination with oil and alone. Our study reveals an acute sensitivity to Corexit EC9580A and dilbit by surface-dwelling insects and may be driven by disruption of mechanisms of buoyancy. We highlight a need to evaluate physical impacts, typically excluded from standard toxicity testing, within the context of spill impact mitigation assessments. Environ Toxicol Chem 2021;40:1298-1307. © 2020 SETAC., (© 2020 SETAC.)

Droplet size substantially affects the fate of oil released from deep subsea leaks. A baseline dataset of volume-median droplet diameters (d 50 ), culled from ~250 laboratory observations, is used to validate seven droplet-size models. Four models compare reasonably well, having 95% confidence limits in d 50 of ~±50%. Simulations with a near-field fate model (TAMOC) reveals that the four best-performing models, with d 50 of 1.3-2.2 mm, agree similarly with observed fractionation of petroleum compounds in the water column during June 4-July 15, 2010. Model results suggest that, had a higher dose of dispersant been applied at the wellhead during Deepwater Horizon oil spill (DWH), the d 50 would have dropped by an order of magnitude, reducing surfacing C 1 -C 9 volatiles by 3.5×. Model uncertainty is found to be substantial for DWH-like blowouts treated with chemical dispersants, suggesting the need for further droplet-size model improvement., (Copyright © 2020 Elsevier Ltd. All rights reserved.)

When birds are exposed to oil, their ability to thermoregulate is impaired as a result of damage to the insulative properties of their feathers. If an oiled bird is unable to maintain thermal homeostasis, hypothermia and death can follow rapidly. Physiological responses to oiling depend on several variables including environmental conditions (e.g., ambient air and water temperatures), life history of bird species (e.g., body size and habitat selection), and foraging strategies (e.g., divers, surface feeders, shorebirds). The most widely used approach to assess the effect of spilled oil on birds is the US Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA) Type A Natural Resource Damage Assessment (NRDA) Model for Coastal and Marine Environments. This approach addresses body size and time spent in a hypothetical slick but lacks the flexibility to assess other variables related to physiological response. We developed a dynamic physiologically based oiling model (PBOM) for birds to address this need. The PBOM has been validated against empirical data from a dose-response study in which common eiders were exposed to Statfjord A crude oil. The PBOM can be used to predict time to hypothermia for birds of differing body size and habitat preferences, in environments ranging from Arctic to subtropical. The model presently includes 5 representative bird species: common eider, spotted sandpiper, great blue heron, dovekie, and American white pelican, but could be adapted to represent almost any bird. Environ Toxicol Chem 2021;40:251-260. © 2020 SETAC., (© 2020 SETAC.)

Antarctic marine environments are at risk from petroleum fuel spills as shipping activities in the Southern Ocean increase. Knowledge of the sensitivity of Antarctic species to fuels under environmentally realistic exposure conditions is lacking. We determined the toxicity of 3 fuels, Special Antarctic Blend diesel (SAB), marine gas oil (MGO), and intermediate fuel oil (IFO 180) to a common Antarctic sea urchin, Sterechinus neumayeri. Sensitivity was estimated for early developmental stages from fertilization to the early 4-arm pluteus in toxicity tests of up to 24 d duration. The effects of the water accommodated fractions (WAFs) of fuels were investigated under different exposure scenarios to determine the relative sensitivity of stages and of different exposure regimes. Sensitivity to fuel WAFs increased through development. Both MGO and IFO 180 were more toxic than SAB, with median effect concentration values for the most sensitive pluteus stage of 3.5, 6.5, and 252 µg/L total hydrocarbon content, respectively. Exposure to a single pulse during fertilization and early embryonic development showed toxicity patterns similar to those observed from continuous exposure. The results show that exposure to fuel WAFs during critical early life stages affects the subsequent viability of larvae, with consequent implications for reproductive success. The sensitivity estimates for S. neumayeri that we generated can be utilized in risk assessments for the management of Antarctic marine ecosystems. Environ Toxicol Chem 2020;39:2527-2539. © 2020 SETAC., (© 2020 SETAC.)

Three hydrocarbon degrading microorganisms were isolated from the soil samples collected from the storage sites of low viscosity spindle oil containers and identified on the basis of morphological and biochemical characteristics as Aeromonas hydrophila, Bacillus subtilis and Staphylococcus aureus. The study has revealed high ability of these microorganisms for oil biodegradation. The results have indicated that all isolates had the potential to breakdown the hydrocarbon. The most efficient bacteria among these examined was Aeromonas hydrophila which biodegraded almost all tested hydrocarbon giving a treatment percentage of 98% within 30 days which was considered as the perfect period for degradation. Also, a small scale was designed to treat the spindle oil with the using of oxidation process and all the tested organic materials were biodegraded in a treatment percentage of 100% within retention time of 20 days.

Crude oil production (COP) is a high-pollution industry but the vast Amazon rainforest has been an active COP zone for South America. Although COP has been associated with a variety of health effects among workers around the world, such effects have not been adequately investigated in the Amazon region, especially at the community level. Therefore, this review was conducted to provide a report about COP in the Amazon of Ecuador and about its association with health status of indigenous human populations. Some epidemiological surveys in the Amazonian Territories indicate that COP has been associated with health problems in the surrounding populations, e.g. cancers in the stomach, rectum, skin, soft tissue, kidney and cervix in adults, and leukemia in children. In addition, some biomarkers and mechanistic studies show exposure effects. However, due to limitations from these studies, contradictory associations have been reported. Our review indicates that COP in the Amazonian territories of northern Ecuador was characterised by contamination which could have affected the indigenous and non-indigenous populations. However, there have not been dedicated investigations to provide relationships between the contamination and the subsequent exposure-health effects. Since indigenous populations have different lifestyle and cultures from regular city dwellers, systematic studies on their potential health hazards need to be conducted. Due to the remote locations and sparse populations, these new studies may involve the use of novel and genomic-based biomarkers as well as using high technology in the remote regions., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2019 The Author(s). Published by Elsevier B.V. All rights reserved.)

Cardiac remodeling results from both physiological and pathological stimuli. Compared with mammalian hearts, fish hearts show a broader array of remodeling changes in response to environmental influences, providing exceptional models for dissecting the molecular and cellular bases of cardiac remodeling. We recently characterized a form of pathological remodeling in juvenile pink salmon ( Oncorhynchus gorbuscha ) in response to crude oil exposure during embryonic cardiogenesis. In the absence of overt pathology (cardiomyocyte death or inflammatory infiltrate), cardiac ventricles in exposed fish showed altered shape, reduced thickness of compact myocardium and hypertrophic changes in spongy, trabeculated myocardium. Here, we used RNA sequencing to characterize molecular pathways underlying these defects. In juvenile ventricular cardiomyocytes, antecedent embryonic oil exposure led to dose-dependent upregulation of genes involved in innate immunity and two NKX homeobox transcription factors not previously associated with cardiomyocytes, nkx2.3 and nkx3.3 Absent from mammalian genomes, the latter is largely uncharacterized. In zebrafish embryos, nkx3.3 demonstrated a potent effect on cardiac morphogenesis, equivalent to that of nkx2.5 , the primary transcription factor associated with ventricular cardiomyocyte identity. The role of nkx3.3 in heart growth is potentially linked to the unique regenerative capacity of fish and amphibians. Moreover, these findings support a cardiomyocyte-intrinsic role for innate immune response genes in pathological hypertrophy. This study demonstrates how an expanding mechanistic understanding of environmental pollution impacts - i.e. the chemical perturbation of biological systems - can ultimately yield new insights into fundamental biological processes., Competing Interests: Competing interestsThe authors declare no competing or financial interests., (© 2019. Published by The Company of Biologists Ltd.)

Dispersants are used to reduce the impact of oil spills in marine environment. Experiments were conducted with natural materials which were contaminated by direct application of fresh Louisiana crude oil. The natural materials evaluated included sea sand (South Beach in Miami, Florida), red mangrove leaves (Rhizophora mangle), and sea shells (Donax variabili). Salt water at two different salinities (17 and 34 ppt) was used with two types of Corexit dispersant solutions (9500A and 9527A) in concentrations ranging from 100 to 3500 mg/L. Washing of the contaminated samples was conducted by a three-step mixing procedure (salt water only, then with the addition of the dispersant solution to the salt water, and salt water) to simulate oil-saltwater-dispersant interactions. In general, increasing dispersant concentration increased the percentage of oil dispersed into the aqueous phase up to dispersant solutions containing 400 mg/L for Corexit 9500A and 300 mg/L Corexit 9527A. Increasing the dispersant concentration above these levels also decreased the dispersion of oil from the surfaces. At very high concentrations of dispersant solutions (above 1500 mg/L), the percentage of oil dispersed into the solution from the contaminated surfaces was about one half what was observed at 400 mg/L with Corexit 9500A and 300 mg/L Corexit 9527A. Although dispersants were most effective for removing the fresh Louisiana crude oil from sand particles and dispersing into the solution due to large surface area of the particles per unit weight; the residual oil remaining on the sand particles was relatively high in comparison to mangrove leaves and sea shells due to clustering of sand particle with oil. There was some oil penetration into the porous structure of the sea shells (at the microscopic level) which could not be removed., (Copyright © 2019 Elsevier Ltd. All rights reserved.)

As the main fluorescent substances in oils, polycyclic aromatic hydrocarbons (PAHs) are the basis of ultraviolet (UV)-induced fluorescence spectroscopy methods to detect oil films on the sea surface. The relative contents of PAHs in six crude oil samples and their effects on ultraviolet fluorescence spectra were studied. The PAHs were divided into four categories according to their fluorescence characteristics. Naphthalene series dominated the fluorescence spectra, which led to a main peak at 320-350 nm, but this showed no relationship with PAH content. The six oil samples could not be distinguished by differences in the fluorescence spectra in this range, but could be distinguished by the fluorescence spectra in the 350-380 nm band. The relative contents of dibenzothiophene and phenanthrene series showed significant positive correlations (R 2  = 0.96) with fluorescence intensity. Fluorescence spectroscopy combined with GC-MS can be used to distinguish and identify crude oils., (Copyright © 2019 Elsevier Ltd. All rights reserved.)

The present study examined impacts of crude oil exposure on dyad competition in juvenile red drum. Following the 2010 Deepwater Horizon oil spill, it has become well established that oil exposure can constrain maximum metabolic rate, reduce aerobic scope and exercise performance in marine fish. Aerobic scope is one of the physiological characteristics that is a known determinant of dominance in fish social hierarchy formation. As such, oil exposure may predispose individuals to subordinate social status, complete with the concomitant ecological costs. We tested this hypothesis on the gregarious Gulf of Mexico species, the red drum (Sciaenops ocellatus). Using a standard dyad, one-on-one, test design, we first assessed the parameters - including size and aerobic scope- that predict social dominance. Of the tested parameters, only aerobic scope was predictive of social dominance, with dominant individuals consistently having higher aerobic scopes than subordinates. Hierarchy formation between individuals exposed to one of two oil concentrations (5.7 ± 0.5 and 9.0 ± 0.2 μg l -1 ΣPAH 50 ) and unexposed conspecifics were then investigated. As hypothesized, fish exposed to both oil concentrations were more likely to be subordinate than what would occur by random chance. These results demonstrate that the physiological constraints imposed by oil exposure can affect social status and behavior in fishes, which can have downstream consequences for ecological fitness., (Copyright © 2018 Elsevier B.V. All rights reserved.)

Given their particle feeding behavior, sessile nature, and abundance in coastal zones, bivalves are at significant risk for exposure to oil and oil dispersant following environmental disasters like the Deepwater Horizon oil spill. However, the effects of oil combined with oil dispersants on the health of oysters are not well studied. Therefore, eastern oysters (Crassostrea virginica) were exposed in vivo to Corexit ® 9500, crude oil (high-energy water accommodated fraction; HEWAF), and a Corexit ® /oil mixture (chemically-enhanced water accommodated fraction; CEWAF) to evaluate potential toxic effects on immunological (phagocytosis and respiratory burst), physiological (feeding rate), and histological endpoints. Phagocytosis was significantly increased following CEWAF exposure only. Respiratory burst was significantly decreased following Corexit ® exposure, but significantly increased following exposure to the highest concentration of CEWAF. Oyster feeding rates were significantly decreased following exposure to Corexit ® , HEWAF, and CEWAF, and were most sensitive to CEWAF exposure. These modulations of important immunological and physiological functions could result in serious health outcomes for oysters, such as increased parasitism and decreased growth. Our experiments showed that subtle, sub-lethal effects occurred following acute in vivo exposure to Corexit ® , HEWAF, and CEWAF, though oysters were not equally sensitive to the three components. Data from this study can be used for more accurate risk assessment concerning the impact of oil and Corexit ® on the health of oysters., (Copyright © 2018 Elsevier B.V. All rights reserved.)

Two fuel oils and two crude oils were subjected to a 60-day weathering simulation experiment, and the effects of weathering on some common parameters for aromatics and aromatic δ 13 C values were studied. The results show that weathering of all oil samples affected little the DBT/P (dibenzothiophene/phenanthrene) ratio and methylphenanthrene distribution fraction. Four oil samples could be distinguished only by the DBT/P ratio. The effect of weathering on isotopes in polycyclic aromatic hydrocarbons was small. The results show that the types of four oil samples can be distinguished, while Kuwait and Russia crude oils cannot be discriminated from each other totally by double-coordinate two-dimensional maps for aromatic δ 13 C; all of the oil samples can be distinguished by principal component analysis of δ 13 C for aromatics, the relationship of DBT/P and PAHs δ 13 C values. Therefore, the δ 13 C value of aromatics can be used as an alternative index for the analysis of oil spills., (Copyright © 2018 Elsevier Ltd. All rights reserved.)

Some polycyclic aromatic hydrocarbons (PAHs), components of crude oil, are known to cause increased toxicity when organisms are co-exposed with ultraviolet radiation, resulting in photo-induced toxicity. The photodynamic characteristics of some PAHs are of particular concern to places like Australia with high ultraviolet radiation levels. The objective of the present study was to characterize the photo-induced toxicity of an Australian North West Shelf oil to early life stage yellowtail kingfish (Seriola lalandi) and black bream (Acanthopagrus butcheri). The fish were exposed to high-energy water accommodated fractions for 24 to 36 h. During the exposure, the fish were either co-exposed to full-intensity or filtered natural sunlight and then transferred to clean water. At 48 h, survival, cardiac effects, and spinal deformities were assessed. Yellowtail kingfish embryos co-exposed to oil and full-spectrum sunlight exhibited decreased hatching success and a higher incidence of cardiac arrhythmias, compared with filtered sunlight. A significant increase in the incidence of pericardial edema occurred in black bream embryos co-exposed to full-spectrum sunlight. These results highlight the need for more studies investigating the effects of PAHs and photo-induced toxicity under environmental conditions relevant to Australia. Environ Toxicol Chem 2018;37:1359-1366. © 2018 SETAC., (© 2018 SETAC.)

Competing Interests: Competing interests: None declared.

Increasing anthropogenic activities in the Arctic pose the risk for accidental oil spills but our knowledge of ecotoxicological effects is still limited for Arctic organisms. This study aimed to provide insights in baseline levels of antioxidants in polar cod (Boreogadus saida) from different Arctic locations and investigate the susceptibility of this species to oxidative stress during a 32 day dietary crude oil exposure. Baseline levels of individual antioxidants and total oxyradical scavenging capacity (TOSC) varied among different Arctic fjords. Upon crude oil exposure, dose- and time-dependent polycyclic aromatic hydrocarbons (PAHs) biotransformation was evident through hepatic ethoxyresorufine-O-deethylase activity, glutathione S-transferase mRNA expression and biliary PAH metabolites. Changes in the activity of individual antioxidants and TOSC was, however, slight and transient upon exposure. In conclusion, biotransformation was clearly induced by the sub-lethal levels of crude oil in polar cod, while the antioxidant defense responded with high variability., (Copyright © 2017 Elsevier Ltd. All rights reserved.)

Windows of exposure to a weathered Deepwater Horizon oil sample (slick A) were examined for early life stage mahi-mahi (Coryphaena hippurus) to determine whether there are developmental periods of enhanced sensitivity during the course of a standard 96-h bioassay. Survival was assessed at 96 h following oil exposures ranging from 2 h to 96 h and targeting 3 general periods of development, namely the prehatch phase, the period surrounding hatch, and the posthatch phase. In addition, 3 different oil preparations were used: high- and low-energy water accommodated fractions of oil and very thin surface slicks of oil (∼1 μm). The latter 2 were used to distinguish between effects due to direct contact with the slick itself and the water underlying the slick. Considering the data from all 3 exposure regimes, it was determined that the period near or including hatch was likely the most sensitive. Furthermore, toxicity was not enhanced by direct contact with slick oil. These findings are environmentally relevant given that the concentrations of polycyclic aromatic hydrocarbons eliciting mortality from exposures during the sensitive periods of development were below or near concentrations measured during the active spill phase. Environ Toxicol Chem 2017;36:1887-1895. © 2016 SETAC., (© 2016 SETAC.)

The Deepwater Horizon oil spill in 2010 overlapped with the spawning of many pelagic fish species in the Gulf of Mexico, including mahi-mahi (Coryphaena hippurus). Polycyclic aromatic hydrocarbons (PAHs) released during the spill have been shown to cause photo-induced toxicity under ultraviolet (UV) radiation. In the present study, mahi-mahi embryos were exposed to high-energy water accommodated fractions of source and naturally weathered oils for up to 48 h. The timing of co-exposure with UV radiation varied between an early development exposure for 8 h or a late development exposure for 8 h. The UV co-exposure had a photo-induced toxic effect on hatching success for all oil types and exposure scenarios. A more sensitive developmental window to photo-induced toxicity was observed when UV exposure occurred late in development. Source Oil B was over 6-fold more toxic, and Massachusetts source oil was 1.6-fold more toxic when the embryos were co-exposed to UV light late in development. Furthermore, weathered oil from the surface co-exposure with UV late in development resulted in bradycardia in the mahi-mahi. The present study provides evidence that the developmental window when UV co-exposure occurs has a significant effect on the degree of photo-induced toxicity of oil and that UV co-exposure may exacerbate long-term cardiac effects in developing fish. Environ Toxicol Chem 2017;36:1592-1598. © 2016 SETAC., (© 2016 SETAC.)

The Deepwater Horizon blowout resulted in the release of millions of barrels of crude oil. As part of the Trustees' Natural Resource Damage Assessment, a testing program was implemented to evaluate the toxicity of Deepwater Horizon oil and oil/dispersant mixtures to aquatic organisms from the Gulf of Mexico. Because of the variety of exposures that likely occurred, the program included 4 Deepwater Horizon oils, which encompassed a range of weathering states, and 3 different oil-in-water mixing methods, for a total of 12 unique water accommodated fractions (WAFs). The present study reports on the chemical characteristics of these 4 Deepwater Horizon oils and 12 WAFs. In addition, to better understand exposure chemistry, an examination was conducted of the effects of WAF preparation parameters-including mixing energy, starting oil composition, and oil-to-water mixing ratios-on the chemical profiles and final concentrations of these 12 WAFs. The results showed that the more weathered the starting oil, the lower the concentrations of the oil constituents in the WAF, with a shift in composition to the less soluble compounds. In addition, higher mixing energies increased the presence of insoluble oil constituents. Finally, at low to mid oil-to-water mixing ratios, the concentration and composition of the WAFs changed with changing mixing ratios; this change was not observed at higher mixing ratios (i.e., >1 g oil/L). Ultimately, the present study provides a basic characterization of the oils and WAFs used in the testing program, which helps to support interpretation of the more than 500 Deepwater Horizon Natural Resource Damage Assessment toxicity testing results and to enable a comparison of these results with different tests and with the field. Environ Toxicol Chem 2017;36:1450-1459. © 2016 SETAC., (© 2016 SETAC.)

In response to the Deepwater Horizon oil spill, the Natural Resource Trustees implemented a toxicity testing program that included 4 different Deepwater Horizon oils that ranged from fresh to weathered, and 3 different oil-in-water preparation methods (including one that used the chemical dispersant Corexit 9500) to prepare a total of 12 chemically unique water accommodated fractions (WAFs). We determined how the different WAF preparation methods, WAF concentrations, and oil types influenced the chemical composition and concentration of polycyclic aromatic hydrocarbons (PAHs) in the dissolved and particulate phases over time periods used in standard toxicity tests. In WAFs prepared with the same starting oil and oil-to-water ratio, the composition and concentration of the dissolved fractions were similar across all preparation methods. However, these similarities diverged when dilutions of the 3 WAF methods were compared. In WAFs containing oil droplets, we found that the dissolved phase was a small fraction of the total PAH concentration for the high-concentration stock WAFs; however, the dissolved phase became the dominant fraction when it was diluted to lower concentrations. Furthermore, decreases in concentration over time were mainly related to surfacing of the larger oil droplets. The initial mean diameters of the droplets were approximately 5 to 10 μm, with a few droplets larger than 30 μm. After 96 h, the mean droplet size decreased to 3 to 5 μm, with generally all droplets larger than 10 μm resurfacing. These data provide a detailed assessment of the concentration and form (dissolved vs particulate) of the PAHs in our WAF exposures, measurements that are important for determining the effects of oil on aquatic species. Environ Toxicol Chem 2017;36:1460-1472. © 2017 SETAC., (© 2017 SETAC.)

The Deepwater Horizon oil spill released millions of barrels of crude oil into the northern Gulf of Mexico, much of which remains associated with sediments and can have continuing impacts on biota. Juvenile southern flounder (Paralichthys lethostigma) were exposed for 28 d in the laboratory under controlled conditions to reference and Deepwater Horizon oil-contaminated sediments collected from coastal Louisiana to assess the impacts on an ecologically and commercially important benthic fish. The measured polycyclic aromatic hydrocarbon (PAH) concentrations in the sediments ranged from 0.25 mg/kg to 3940 mg/kg suite of 50 PAH analytes (tPAH50). Mortality increased with both concentration and duration of exposure. Exposed flounder length and weight was lower compared to controls after 28 d of exposure to the sediments with the highest PAH concentration, but condition factor was significantly higher in these fish compared with all other treatments. Histopathological analyses showed increased occurrence of gill abnormalities, including telangiectasis, epithelial proliferation, and fused lamellae in flounder exposed to sediments with the highest tPAH50 concentrations. In addition, hepatic vascular congestion and macrovesicular vacuolation were observed in flounder exposed to the more contaminated sediments. These data suggest that chronic exposure to field collected oil-contaminated sediments results in a variety of sublethal impacts to a benthic fish, with implications for long-term recovery from oil spills. Environ Toxicol Chem 2017;36:1067-1076. © 2016 SETAC., (© 2016 SETAC.)

Raindrops falling on the sea surface produce turbulence. The present study examined the influence of rain-induced turbulence on oil droplet size and dispersion of oil spills in Douglas Channel in British Columbia, Canada using hourly atmospheric data in 2011-2013. We examined three types of oils: a light oil (Cold Lake Diluent - CLD), and two heavy oils (Cold Lake Blend - CLB and Access Western Blend - AWB). We found that the turbulent energy dissipation rate produced by rainfalls is comparable to what is produced by wind-induced wave breaking in our study area. With the use of chemical dispersants, our results indicate that a heavy rainfall (rain rate>20mmh -1 ) can produce the maximum droplet size of 300μm for light oil and 1000μm for heavy oils, and it can disperse the light oil with fraction of 22-45% and the heavy oils of 8-13%, respectively. Heavy rainfalls could be a factor for the fate of oil spills in Douglas Channel, especially for a spill of light oil and the use of chemical dispersants., (Crown Copyright © 2016. Published by Elsevier Ltd. All rights reserved.)