Genome-wide DNA methylation changes in Oryzias melastigma embryos exposed to the water accommodated fraction of crude oil.

The water accommodated fraction (WAF) of crude oil exerts considerable impacts on marine fish during embryonic stage. Clarifying changes in epigenetic modifications is helpful for understanding the molecular mechanism underlying the toxicity of embryonic WAF exposure. The aim of this study was to explore genome-wide DNA methylation changes in Oryzias melastigma embryos after exposure to the nominal total petroleum hydrocarbon concentration of 500 µg/L in WAF for 7 days. Whole-genome bisulfite sequencing revealed that 8.47 % and 8.46 % of all the genomic C sites were methylated in the control and WAF-exposed groups, respectively. Among the three sequence contexts, methylated CG site had the largest number in both the two groups. The sequence preferences of nearby methylated cytosines were consistent between the two groups. A total of 4798 differentially methylated regions (DMRs) were identified in the promoter region. Furthermore, Gene Ontology analysis revealed that DMR-related genes were enriched mainly for functions related to development and nervous system. Additionally, the Kyoto Encyclopedia of Genes and Genomes pathways enriched in DMR-related genes were related to nervous system and endocrine system. These novel findings provide comprehensive insights into the genome-wide DNA methylation landscape of O. melastigma following embryonic WAF exposure, shedding light on the epigenetic regulatory mechanisms underlying WAF-induced toxicity.

The toxic effects of petroleum pollutants to microalgae in marine environment.

Marine oil pollution is one of the major global environmental pollution problems. Marine microalgae are the foundation of the marine food chain, providing the main primary productivity of the ocean. They not only maintain the energy flow and material cycle of the entire marine ecosystem, but also play an important role in regulating global climate change. Exploring the impact of petroleum pollutants on marine microalgae is extremely important for studying marine environmental pollution. This review first introduced the sources, compositions, and forms of petroleum pollutants and their migration and transformation processes in the ocean. Then, the toxic effects of petroleum pollutants on marine microalgae were summarized. The growth of marine microalgae showed low-concentration promotion and high-concentration inhibition. The population growth and interspecific relationships of marine microalga was changed and the photosynthesis of marine microalgae was influenced. Finally, potential research directions and suggestions for marine microalgae in the future were proposed.

Surface active dicationic ionic liquids as green oil spill dispersants.

The utilization of chemical dispersants as a way of mitigating of oil spills in marine eco-system has been extensively documented worldwide. Hence, in this research we have successfully synthesized two amphiphilic asymmetric Dicaionic Ionic Liquids (DILs). The efficacy of these synthesized DILs as dispersants was assessed using the baffled flask test (BFT). The results indicated a dispersant effectiveness ranging from 47.98 % to 79.76 % for the dispersion of heavy crude oil across various temperature ranges (10-30 °C). These dispersant-to-oil ratios (DOR) were maintained at 3: 100 (V%), showcasing promising dispersant capabilities for mitigating heavy crude oil spills. Additionally, acute toxicity tests conducted on Nile tilapia and Oreochromis niloticus have demonstrated the relatively low toxicity of the IL-dispersants, with Lethal Concentration 50 (LC50) values exceeding 100 ppm after 96 h. This suggests a practically slight toxic effect on the tested fish. In summary, the newly developed IL-dispersants are considered to be conducive to environmentally benign oil spill remediation.

Parsing the toxicity paradox: Composition and duration of exposure alter predicted oil spill effects by orders of magnitude.

Oil spilled into an aquatic environment produces oil droplet and dissolved component concentrations and compositions that are highly variable in space and time. Toxic effects on aquatic biota vary with sensitivity of the organism, concentration, composition, environmental conditions, and frequency and duration of exposure to the mixture of oil-derived dissolved compounds. For a range of spill (surface, subsea, blowout) and oil types under different environmental conditions, modeling of oil transport, fate, and organism behavior was used to quantify expected exposures over time for planktonic, motile, and stationary organisms. Different toxicity models were applied to these exposure time histories to characterize the influential roles of composition, concentration, and duration of exposure on aquatic toxicity. Misrepresenting these roles and exposures can affect results by orders of magnitude. Well-characterized laboratory studies for <24-hour exposures are needed to improve toxicity predictions of the typically short-term exposures that characterize spills.

Different responses of marine microalgae Phaeodactylum tricornutum upon exposures to WAF and CEWAF of crude oil: A case study coupled with stable isotopic signatures.

Increasing use of chemical dispersants for oil spills highlights the need to understand their adverse effects on marine microalgae and nutrient assimilation because the toxic components of crude oil can be more bioavailable. We employed the crude oil water-accommodated fraction (WAF) and chemically enhanced WAF (CEWAF) to compare different responses in marine microalgae (Phaeodactylum tricornutum) coupled with stable isotopic signatures. The concentration and proportion of high-molecular-weight polycyclic aromatic hydrocarbons (HMW PAHs), which are key toxic components in crude oil, increased after dispersant addition. CEWAF exposure caused higher percent growth inhibition and a lower chlorophyll-a level of microalgae than those after WAF exposure. Compared with WAF exposure, CEWAF led to an enhancement in the self-defense mechanism of P. tricornutum, accompanied by an increased content of extracellular polymeric substances. 13C-depletion and carbon assimilation were altered in P. tricornutum, suggesting more HMW PAHs could be utilized as carbon sources by microalgae under CEWAF. CEWAF had no significant effects on the isotopic fractionation or assimilation of nitrogen in P. tricornutum. Our study unveiled the impact on the growth, physiological response, and nutrient assimilation of microalgae upon WAF and CEWAF exposures. Our data provide new insights into the ecological effects of dispersant applications for coastal oil spills.

Oil droplet fouling on lesser sandeel (Ammodytes marinus) eggshells does not enhance the crude oil induced developmental toxicity.

The oil industry's expansion and increased operational activity at older installations, along with their demolition, contribute to rising cumulative pollution and a heightened risk of accidental oil spills. The lesser sandeel (Ammodytes marinus) is a keystone prey species in the North Sea and coastal systems. Their eggs adhere to the seabed substrate making them particularly vulnerable to oil exposure during embryonic development. We evaluated the sensitivity of sandeel embryos to crude oil in a laboratory by exposing them to dispersed oil at concentrations of 0, 15, 50, and 150 µg/L oil between 2 and 16 days post-fertilization. We assessed water and tissue concentrations of THC and tPAH, cyp1a expression, lipid distribution in the eyes, head and trunk, and morphological and functional deformities. Oil droplets accumulated on the eggshell in all oil treatment groups, to which the embryo responded by a dose-dependent rise in cyp1a expression. The oil exposure led to only minor sublethal deformities in the upper jaw and otic vesicle. The findings suggest that lesser sandeel embryos are resilient to crude oil exposure. The lowest observed effect level documented in this study was 36 µg THC/L and 3 µg tPAH/L. The inclusion of these species-specific data in risk assessment models will enhance the precision of risk evaluations for the North Atlantic ecosystems.

A simple protocol for estimating the acute toxicity of unresolved polar compounds from field-weathered oils.

Crude oil spilled at sea is chemically altered through environmental processes such as dissolution, biodegradation, and photodegradation. Transformation of hydrocarbons to oxygenated species increases water-solubility. Metabolites and oxidation products largely remain uncharacterized by common analytical methods but may be more bioavailable to aquatic organisms. Studies have shown that unresolved (i.e. unidentified) polar compounds ('UPCs') may constitute > 90% of the water-accommodated fraction (WAF) of heavily weathered crude oils, but still there is a paucity of information characterizing their toxicological significance in relation to other oil-derived toxicants. In this study, low-energy WAFs (no droplets) were generated from two field-weathered oils (collected during the 2010 Deepwater Horizon incident) and their polar fractions were isolated through fractionation. To allow establishment of thresholds for acute toxicity (LC50) of the dissolved and polar fraction of field collected oils, we concentrated both WAFs and polar fractions to beyond field-documented concentrations, and the acute toxicity of both to the marine copepod Acartia tonsa was measured and compared to the toxicity of the native WAF (non-concentrated). The difference in toxic units (TUs) between the total of the mixture and of identified compounds of known toxicity (polycyclic aromatic hydrocarbons [PAHs] and alkyl phenols) in both WAF and polar fractions was used to estimate the contribution of the UPC to overall toxicity. This approach identified that UPC had a similar contribution to toxicity as identified compounds within the WAFs of the field-weathered oils. This signifies the relative importance of polar compounds when assessing environmental impacts of spilled and weathered oil.

Biochemical, molecular, and physiological assessments of crude oil dietary exposure in sub-adult red drum (Sciaenops ocellatus).

A 14-day exposure study in which sub-adult red drum (Sciaenops ocellatus) were fed a petroleum crude oil-treated pellet feed was conducted to assess the potential effects of ingesting an oil-contaminated food source. Though food consumption decreased, significant polycyclic aromatic hydrocarbons accumulated in the body and liver, which did not affect the body and liver's fatty acid composition. In the red drum given the crude oil-treated feed, a significant decrease in the RNA:DNA growth rate index was noted, while only subtle changes in body and liver lipid composition were seen. Differentially expressed gene analysis in the liver demonstrated a significant down-regulation of leptin and up-regulation of the aryl hydrocarbon receptor nuclear translocator-like protein 1. Gene ontology and Kyoto Encyclopedia of Genes and Genomes analyses indicated enrichment of terms and pathways associated with cholesterol biosynthesis and oxidative stress. Ingenuity Pathway Analysis further predicted activation of seven pathways associated with cholesterol biosynthesis. Measured oxidative stress biomarkers in the blood indicated decreased systemic antioxidants with increased lipid peroxidation. The results of this study suggest that dietary oil exposure alters the signaling of biological pathways critical in cholesterol biosynthesis and disruptions in systemic oxidative homeostasis.

Use of TLM derived models to estimate toxicity of weathered MC252 oil based on conventional chemical data and the potential impact of unresolved polar components.

Target lipid model (TLM) and toxic unit (TU) approaches were applied to ecotoxicity and chemistry data from low-energy WAFs (LE-WAFs) of source and weathered crude oils originating from the Deepwater Horizon oil spill. The weathered oils included artificially weathered oils and naturally weathered samples collected in the Gulf of Mexico after the spill. Oil weathering greatly reduced the concentrations of identified LE-WAF components, however, the mass of uncharacterized polar material (UPC) in the LE-WAFs remained largely unchanged during the weathering process. While the TLM-derived calculations displayed a significant decrease in toxicity (TUs) for the heavily weathered oils, copepod toxicity, expressed as LC10-based TUs, were comparable between LE-WAFs of fresh and weathered oils. The discrepancy between observed and predicted toxicity for the LE-WAFs of artificially weathered oils may be related to limitations by the chemical analyses or increased toxicity due to generation of new unknown compounds during the weathering process.

Transcriptome analysis of Sparidentex hasta larvae exposed to water-accommodated fraction of Kuwait crude oil.

Anthropogenic activities have been shown to significantly affect marine life. Water pollution and oil spills are particularly deleterious to the fish population, especially during their larval stage. In this study, Sobaity-sea bream Sparidentex hasta (Valenciennes, 1830) larvae were exposed to serial dilutions of water-accommodated fraction of Kuwait crude oil (KCO-WAF) for varying durations (3, 6, 24, 48, 72 or 96 h) in acute exposure regime. Gene expression was assessed using RNA sequencing and validated through RT-qPCR. The RNA sequencing data were aligned to the sequenced genome, and differentially expressed genes were identified in response to treatment with or without KCO-WAF at various exposure times. The highest number of differentially expressed genes was observed at the early time point of 6 h of post-exposure to KCO-WAF. The lowest number of differentially expressed genes were noticed at 96 h of treatment indicating early response of the larvae to KCO-WAF contaminant. The acquired information on the differentially expressed genes was then used for functional and pathway analysis. More than 90% of the differentially expressed genes had a significant BLAST match, with the two most common matching species being Acanthopagrus latus and Sparus aurata. Approximately 65% of the differentially expressed genes had Gene Ontology annotations, whereas > 35% of the genes had KEGG pathway annotations. The differentially expressed genes were found to be enriched for various signaling pathways (e.g., MAPK, cAMP, PI3K-Akt) and nervous system-related pathways (e.g., neurodegeneration, axon guidance, glutamatergic synapse, GABAergic synapse). Early exposure modulated the signaling pathways, while KCO-WAF exposure of larvae for a longer duration affected the neurodegenerative/nervous system-related pathways. RT-qPCR analysis confirmed the differential expression of genes at each time point. These findings provide insights into the underlying molecular mechanisms of the deleterious effects of acute exposure to oil pollution-on marine fish populations, particularly at the early larval stage of Sparidentex hasta.

Structure-activity relationships for alkyl-phenanthrenes support two independent but interacting synergistic models for PAC mixture potency.

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 Ca2+ 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+/Ca2+ 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.

Effects of a liquefied petroleum gas stove intervention on stillbirth, congenital anomalies and neonatal mortality: A multi-country household air pollution intervention network trial.

Household air pollution (HAP) from cooking with solid fuels used during pregnancy has been associated with adverse pregnancy outcomes. The Household Air Pollution Intervention Network (HAPIN) trial was a randomized controlled trial that assessed the impact of a liquefied petroleum gas (LPG) stove and fuel intervention on health in Guatemala, India, Peru, and Rwanda. Here we investigated the effects of the LPG stove and fuel intervention on stillbirth, congenital anomalies and neonatal mortality and characterized exposure-response relationships between personal exposures to fine particulate matter (PM2.5), black carbon (BC) and carbon monoxide (CO) and these outcomes. Pregnant women (18 to <35 years of age; gestation confirmed by ultrasound at 9 to <20 weeks) were randomly assigned to intervention or control arms. We monitored these fetal and neonatal outcomes and personal exposure to PM2.5, BC and CO three times during pregnancy, we conducted intention-to-treat (ITT) and exposure-response (E-R) analyses to determine if the HAPIN intervention and corresponding HAP exposure was associated with the risk of fetal/neonatal outcomes. A total of 3200 women (mean age 25.4 ± 4.4 years, mean gestational age at randomization 15.4 ± 3.1 weeks) were included in this analysis. Relative risks for stillbirth, congenital anomaly and neonatal mortality were 0.99 (0.60, 1.66), 0.92 (95 % CI 0.52, 1.61), and 0.99 (0.54, 1.85), respectively, among women in the intervention arm compared to controls in an ITT analysis. Higher mean personal exposures to PM2.5, CO and BC during pregnancy were associated with a higher, but statistically non-significant, incidence of adverse outcomes. The LPG stove and fuel intervention did not reduce the risk of these outcomes nor did we find evidence supporting an association between personal exposures to HAP and stillbirth, congenital anomalies and neonatal mortality.

PAH residues and toxicity levels two years after an extensive oil spill on the northeast Brazilian coast.

The most extensive oil spill ever recorded in tropical oceans occurred between August 2019 and March 2020, affecting approximately 3000 km of the Brazilian coast. This study assessed the chemical contamination and toxicity of sediments collected from affected reef areas during two sampling surveys conducted 17 and 24 months after the peak of oil slick inputs. Our results indicated that neither PAH levels nor measured toxicity showed a significant contribution from the spilled oil, with concentrations and biological effects indistinguishable from those in unaffected areas. Similarly, no differences were observed between seasons. Furthermore, there was no discernible relationship between sediment toxicity results and the measured PAH concentrations. Therefore, while biological responses indicated toxicity in most assessed areas, these responses are likely related to other local sources. This evidence suggests a natural oil attenuation process contributing to local environmental recovery. Nonetheless, further investigation is needed for other areas affected by oil spills.

Toxicological Effects of Inhaled Crude Oil Vapor.

PURPOSE OF REVIEW: The purpose of this review is to assess the toxicological consequences of crude oil vapor (COV) exposure in the workplace through evaluation of the most current epidemiologic and laboratory-based studies in the literature. RECENT FINDINGS: Crude oil is a naturally occuring mixture of hydrocarbon deposits, inorganic and organic chemical compounds. Workers engaged in upstream processes of oil extraction are exposed to a number of risks and hazards, including getting crude oil on their skin or inhaling crude oil vapor. There have been several reports of workers who died as a result of inhalation of high levels of COV released upon opening thief hatches atop oil storage tanks. Although many investigations into the toxicity of specific hydrocarbons following inhalation during downstream oil processing have been conducted, there is a paucity of information on the potential toxicity of COV exposure itself. This review assesses current knowledge of the toxicological consequences of exposures to COV in the workplace.

Systematic characterization of the influence of petroleum spill on terpene metabolism in Suaeda salsa (L.) Pall from coastal wetland: Implication by compound-specific stable isotope.

With the increasing industrialization and urbanization, the ecological environment is suffering from severe deterioration in Liaohe coastal wetland, and petroleum spill is one of the pollution sources. Suaeda salsa (L.) Pall (S. salsa), one of the predominant plants in Liaohe coastal wetland, is facing the increasing degradation. Terpenes are a class of inherent compounds in plants, and play key role in maintain the growth of plants. However, the environmental stress on the terpene metabolism remained unclear in the plants. In the present study, the influence of petroleum spill on terpene metabolism in S. salsa was systematically investigated by analysis of concentrations, compositions and stable carbon isotope. Under the stress of petroleum spill, terpene concentrations showed the decreasing trend, indicating the inhibition effect of petroleum spill on terpene synthesis in S. salsa. The proportions of Sabinene and A-humulene showed the obviously increased with the influence of petroleum spill, implying that these congeners were more sensitive to petroleum spills. The significant changes in stable carbon isotope compositions were observed for Borneol, Dl-menthol, A-humulene and (-) -@-bisabolol, with the enrichment in heavier isotopes in residual fractions. This result indicated that the heavier 13C was preferentially fixed on terpene by S. salsa under the petroleum stress. The similar change trends along the incubation time was observed for A-humulene and (-) - trans caryophyllene, which might imply that A-humulene was one of the products of (-) - trans caryophyllene in S. salsa. Overall, the findings of present study verified the influence of petroleum spill on terpene metabolism in S. salsa, and were meaningful for protecting the plants in the petroleum-pollution wetlands.

Discovery of polycyclic aromatic acid metabolites in fish exposed to the petroleum compounds 1-methylphenanthrene and 1,4-dimethylphenanthrene.

Most of the polycyclic aromatic hydrocarbons (PAHs) in petroleum are alkylated (alkyl PAHs), still the metabolism of these alkyl PAHs to the expected acid products (polycyclic aromatic acids; PAAs) has yet to be demonstrated in oil-exposed fish. Should these compounds be discovered in fish as they have in ragworm, rodents, and humans, they could present an indicative biomarker for assessing oil pollution. In this study, the ability to biotransform alkyl PAHs to PAAs was examined on Atlantic haddock (Melanogrammus aeglefinus). Exposure to phenanthrene, 1-methyphenanthrene or 1,4-dimethylphenanthrene was performed via intraperitoneal injection. An Ion Mobility Quadrupole Time-Of-Flight Mass Spectrometer (IMS-Q-TOF MS) was used in exploratory analysis of extracted bile samples. Acquisition of four-dimensional information by coupling liquid chromatography with the IMS-Q-TOF MS and in-silico prediction for feature prioritization in the data processing workflow allowed several tentative identifications with high degree of confidence. This work presents the first detection of PAAs in fish and suggests the importance of investigating alkyl PAHs in ecotoxicological studies of oil-polluted fish environments.

Unraveling the mechanisms behind sodium persulphate-induced changes in petroleum-contaminated aquifers' biogeochemical parameters and microbial communities.

Sodium persulphate (PS) is a highly effective oxidising agent widely used in groundwater remediation and wastewater treatment. Although numerous studies have examined the impact of PS with respect to the removal efficiency of organic pollutants, the residual effects of PS exposure on the biogeochemical parameters and microbial ecosystems of contaminated aquifers are not well understood. This study investigates the effects of exposure to different concentrations of PS on the biogeochemical parameters of petroleum-contaminated aquifers using microcosm batch experiments. The results demonstrate that PS exposure increases the oxidation-reduction potential (ORP) and electrical conductivity (EC), while decreasing total organic carbon (TOC), dehydrogenase (DE), and polyphenol oxidase (PO) in the aquifer. Three-dimensional excitation-emission matrix (3D-EEM) analysis indicates PS is effective at reducing fulvic acid-like and humic acid-like substances and promoting microbial metabolic activity. In addition, PS exposure reduces the abundance of bacterial community species and the diversity index of evolutionary distance, with a more pronounced effect at high PS concentrations (31.25 mmol/L). Long-term (90 d) PS exposure results in an increase in the abundance of microorganisms with environmental resistance, organic matter degradation, and the ability to promote functional genes related to biological processes such as basal metabolism, transmission of genetic information, and cell motility of microorganisms. Structural equation modeling (SEM) further confirms that ORP and TOC are important drivers of change in the abundance of dominant phyla and functional genes. These results suggest exposure to different concentrations of PS has both direct and indirect effects on the dominant phyla and functional genes by influencing the geochemical parameters and enzymatic activity of the aquifer. This study provides a valuable reference for the application of PS in ecological engineering.

Effects of petrogenic pollutants on North Atlantic and Arctic Calanus copepods: From molecular mechanisms to population impacts.

Oil and gas industries in the Northern Atlantic Ocean have gradually moved closer to the Arctic areas, a process expected to be further facilitated by sea ice withdrawal caused by global warming. Copepods of the genus Calanus hold a key position in these cold-water food webs, providing an important energetic link between primary production and higher trophic levels. Due to their ecological importance, there is a concern about how accidental oil spills and produced water discharges may impact cold-water copepods. In this review, we summarize the current knowledge of the toxicity of petroleum on North Atlantic and Arctic Calanus copepods. We also review how recent development of high-quality transcriptomes from RNA-sequencing of copepods have identified genes regulating key biological processes, like molting, diapause and reproduction in Calanus copepods, to suggest linkages between exposure, molecular mechanisms and effects on higher levels of biological organization. We found that the available ecotoxicity threshold data for these copepods provide valuable information about their sensitivity to acute petrogenic exposures; however, there is still insufficient knowledge regarding underlying mechanisms of toxicity and the potential for long-term implications of relevance for copepod ecology and phenology. Copepod transcriptomics has expanded our understanding of how key biological processes are regulated in cold-water copepods. These advances can improve our understanding of how pollutants affect biological processes, and thus provide the basis for new knowledge frameworks spanning the effect continuum from molecular initiating events to adverse effects of regulatory relevance. Such efforts, guided by concepts such as adverse outcome pathways (AOPs), enable standardized and transparent characterization and evaluation of knowledge and identifies research gaps and priorities. This review suggests enhancing mechanistic understanding of exposure-effect relationships to better understand and link biomarker responses to adverse effects to improve risk assessments assessing ecological effects of pollutant mixtures, like crude oil, in Arctic areas.

Assessing the ecological impacts of polycyclic aromatic hydrocarbons petroleum pollutants using a network toxicity model.

Polycyclic aromatic hydrocarbons (PAHs) are significant petroleum pollutants that have long-term impacts on human health and ecosystems. However, assessing their toxicity presents challenges due to factors such as cost, time, and the need for comprehensive multi-component analysis methods. In this study, we utilized network toxicity models, enrichment analysis, and molecular docking to analyze the toxicity mechanisms of PAHs at different levels: compounds, target genes, pathways, and species. Additionally, we used the maximum acceptable concentration (MAC) value and risk quotient (RQ) as an indicator for the potential ecological risk assessment of PAHs. The results showed that higher molecular weight PAHs had increased lipophilicity and higher toxicity. Benzo[a]pyrene and Fluoranthene were identified as core compounds, which increased the risk of cancer by affecting core target genes such as CCND1 in the human body, thereby influencing signal transduction and the immune system. In terms of biological species, PAHs had a greater toxic impact on aquatic organisms compared to terrestrial organisms. High molecular weight PAHs had lower effective concentrations on biological species, and the ecological risk was higher in the Yellow River Delta region. This research highlights the potential application of network toxicity models in understanding the toxicity mechanisms and species toxicity of PAHs and provides valuable insights for monitoring, prevention, and ecological risk assessment of these pollutants.

Evaluating the in vitro developmental toxicity potency of a series of petroleum substance extracts using new approach methodologies (NAMs).

The present study evaluates the in vitro developmental toxicity and the possible underlying mode of action of DMSO extracts of a series of highly complex petroleum substances in the mouse embryonic stem cell test (mEST), the zebrafish embryotoxicity test (ZET) and the aryl hydrocarbon receptor reporter gene assay (AhR CALUX assay). Results show that two out of sixteen samples tested, both being poorly refined products that may contain a substantial amount of 3- to 7-ring polycyclic aromatic compounds (PACs), induced sustained AhR activation in the AhR CALUX assay, and concentration-dependent developmental toxicity in both mEST and ZET. The other samples tested, representing highly refined petroleum substances and petroleum-derived waxes (containing typically a very low amount or no PACs at all), were negative in all assays applied, pointing to their inability to induce developmental toxicity in vitro. The refining processes applied during the production of highly refined petroleum products, such as solvent extraction and hydrotreatment which focus on the removal of undesired constituents, including 3- to 7-ring PACs, abolish the in vitro developmental toxicity. In conclusion, the obtained results support the hypothesis that 3- to 7-ring PACs are the primary inducers of the developmental toxicity induced by some (i.e., poorly refined) petroleum substances and that the observed effect is partially AhR-mediated.