In vitro and in vivo genotoxicity of oxygenated polycyclic aromatic hydrocarbons

Structure-based modeling to assess binding and endocrine disrupting potential of polycyclic aromatic hydrocarbons in Danio rerio

Environmental contaminants, such as polycyclic aromatic hydrocarbons (PAHs), have raised concerns regarding their potential endocrine-disrupting effects on aquatic organisms, including fish. In this study, molecular docking and molecular dynamics techniques were employed to evaluate the endocrine-disrupting potential of PAHs in zebrafish, as a model organism. A virtual screening with 72 PAHs revealed a correlation between the number of PAH aromatic rings and their binding affinity to proteins involved in endocrine regulation. Furthermore, PAHs with the highest binding affinities for each protein were identified: cyclopenta[cd]pyrene for AR (-9.7 kcal/mol), benzo(g)chrysene for ERα (-11.5 kcal/mol), dibenzo(a,e)pyrene for SHBG (-8.7 kcal/mol), dibenz(a,h)anthracene for StAR (-11.2 kcal/mol), and 2,3-benzofluorene for TRα (-9.8 kcal/mol). Molecular dynamics simulations confirmed the stability of the protein-ligand complexes formed by the PAHs with the highest binding affinities throughout the simulations. Additionally, the effectiveness of the protocol used in this study was demonstrated by the receiver operating characteristic curve (ROC) analysis, which effectively distinguished decoys from true ligands. Therefore, this research provides valuable insights into the endocrine-disrupting potential of PAHs in fish, highlighting the importance of assessing their impact on aquatic ecosystems.

Antagonistic effects of a COX1/2 inhibitor drug in human HepG2 cells exposed to an environmental carcinogen

Understanding interactions between legacy and emerging environmental contaminants has important implications for risk assessment, especially when mutagens and carcinogens are involved, whose critical effects are chronic and therefore difficult to predict. The current work aimed to investigate potential interactions between benzo[a]pyrene (B[a]P), a carcinogenic polycyclic aromatic hydrocarbon and legacy pollutant, and diclofenac (DFC), a non-steroidal anti-inflammatory drug and pollutant of emerging concern, and how DFC affects B[a]P toxicity. Exposure to binary mixtures of these chemicals resulted in substantially reduced cytotoxicity in human HepG2 cells compared to single-chemical exposures. Significant antagonistic effects were observed in response to high concentrations of B[a]P in combination with DFC at IC50 and ⅕ IC50. While additive effects were found for levels of intracellular reactive oxygen species, antagonistic mixture effects were observed for genotoxicity. B[a]P induced DNA strand breaks, γH2AX activation, and micronuclei formation at ½ IC50 concentrations or lower, whereas DFC induced only low levels of DNA strand breaks. Their mixture caused significantly lower levels of genotoxicity by all three endpoints compared to those expected based on concentration additivity. In addition, antagonistic mixture effects on CYP1 enzyme activity suggested that the observed reduced genotoxicity of B[a]P was due to its reduced metabolic activation as a result of enzymatic inhibition by DFC. Overall, the findings further support the growing concern that co-exposure to environmental toxicants and their non-additive interactions may be a confounding factor that should not be neglected in environmental and human health risk assessment.

Toxicity of particles derived from combustion of Ethiopian traditional biomass fuels in human bronchial and macrophage-like cells

The combustion of traditional fuels in low-income countries, including those in sub-Saharan Africa, leads to extensive indoor particle exposure. Yet, the related health consequences in this context are understudied. This study aimed to evaluate the in vitro toxicity of combustion-derived particles relevant for Sub-Saharan household environments. Particles (< 2.5 µm) were collected using a high-volume sampler during combustion of traditional Ethiopian biomass fuels: cow dung, eucalyptus wood and eucalyptus charcoal. Diesel exhaust particles (DEP, NIST 2975) served as reference particles. The highest levels of particle-bound polycyclic aromatic hydrocarbons (PAHs) were found in wood (3219 ng/mg), followed by dung (618 ng/mg), charcoal (136 ng/mg) and DEP (118 ng/mg) (GC-MS). BEAS-2B bronchial epithelial cells and THP-1 derived macrophages were exposed to particle suspensions (1-150 µg/mL) for 24 h. All particles induced concentration-dependent genotoxicity (comet assay) but no pro-inflammatory cytokine release in epithelial cells, whereas dung and wood particles also induced concentration-dependent cytotoxicity (Alamar Blue). Only wood particles induced concentration-dependent cytotoxicity and genotoxicity in macrophage-like cells, while dung particles were unique at increasing secretion of pro-inflammatory cytokines (IL-6, IL-8, TNF-α). In summary, particles derived from combustion of less energy dense fuels like dung and wood had a higher PAH content and were more cytotoxic in epithelial cells. In addition, the least energy dense and cheapest fuel, dung, also induced pro-inflammatory effects in macrophage-like cells. These findings highlight the influence of fuel type on the toxic profile of the emitted particles and warrant further research to understand and mitigate health effects of indoor air pollution.

Evaluation on purine metabolism in human skin fibroblast cells exposed to oxygenated polycyclic aromatic hydrocarbons

A rapid and sensitive assessment of the toxicity of oxygenated polycyclic aromatic hydrocarbons (OPAHs), widely distributed persistent organic pollutants in the environment, is crucial for human health. In this study, using high-performance liquid chromatography, the separation and detection of four purines, xanthine (X), guanine (G), adenine (A), and hypoxanthine (HX) in cells were performed. The aim was to evaluate the cytotoxicity of three OPAHs, namely 1,4-benzoquinone (1,4-BQ), 1,2-naphthoquinone (1,2-NQ) and 9,10-phenanthrenequinone (9,10-PQ), with higher environmental concentrations, from the perspective of purine nucleotide metabolism in human skin fibroblast cells (HFF-1). The results revealed that the levels of G and A were low in HFF-1 cells, while the levels of HX and X showed a dose-response relationship with persistent organic pollutants concentration. With increased concentration of the three persistent organic pollutants, the purine metabolism in HFF-1 cells weakened, and the impact of the three persistent organic pollutants on purine metabolism in cells was in the order of 9,10-PQ > 1,4-BQ > 1,2-NQ. This study provided valuable insights into the toxic mechanisms of 1,4-BQ, 1,2-NQ and 9,10-PQ, contributing to the formulation of relevant protective measures and the safeguarding of human health.

Prioritization of the ecotoxicological hazard of PAHs towards aquatic species spanning three trophic levels using 2D-QSTR, read-across and machine learning-driven modelling approaches

Polycyclic aromatic hydrocarbons (PAHs) represent a common group of environmental pollutants that endanger various aquatic organisms via various pathways. To better prioritize the ecotoxicological hazard of PAHs to aquatic environment, we used 2D descriptors-based quantitative structure-toxicity relationship (QSTR) to assess the toxicity of PAHs toward six aquatic model organisms spanning three trophic levels. According to strict OECD guideline, six easily interpretable, transferable and reproducible 2D-QSTR models were constructed with high robustness and reliability. A mechanistic interpretation unveiled the key structural factors primarily responsible for controlling the aquatic ecotoxicity of PAHs. Furthermore, quantitative read-across and different machine learning approaches were employed to validate and optimize the modelling approach. Importantly, the optimum QSTR models were further applied for predicting the ecotoxicity of hundreds of untested/unknown PAHs gathered from Pesticide Properties Database (PPDB). Especially, we provided a priority list in terms of the toxicity of unknown PAHs to six aquatic species, along with the corresponding mechanistic interpretation. In summary, the models can serve as valuable tools for aquatic risk assessment and prioritization of untested or completely new PAHs chemicals, providing essential guidance for formulating regulatory policies.

Firefighters' personal exposure to gaseous PAHs during controlled forest fires: A case study with estimation of respiratory health risks and in vitro toxicity

Firefighters are daily exposed to adverse health-hazardous pollutants. Polycyclic aromatic hydrocarbons (PAHs), well known endocrine disruptors with carcinogenic, mutagenic, and teratogenic properties, are among the most relevant pollutants. The characterization of firefighters' occupational exposure to airborne PAHs remains limited; information is scarce for European firefighters. Also, the in vitro assessment of firefighters' respiratory health risks is inexistent. To reply to these scientific gaps, this work characterizes the levels of gaseous PAH in firefighters' personal air during regular working activities at controlled forest fires and at fire stations (control group). Breathable levels were 2.2-26.7 times higher during fire events than in the control group (2.63-32.63 μg/m3versus 1.22 μg/m3, p < 0.001); the available occupational guidelines (100 and 200 μg/m3 defined by the US National Institute for Occupational Safety and Health and the North American Occupational Safety and Health Administration, respectively) were not exceeded. Concentrations of (possible/probable) carcinogenic PAHs were 1.9-15.3 times superior during firefighting (p < 0.001). Increased values of total benzo(a)pyrene equivalents (p = 0.101), dose rates (p < 0.001), and carcinogenic risks (p = 0.063) were estimated in firefighters during controlled fires comparatively with the control group. Firefighters' breathable gaseous phase collected during fire events contributed to induce a significant viability decrease (<70 %; p < 0.05) in A549 and Calu-3 cell lines. The principal component analysis (PCA) allowed the differentiation between firefighters participating in controlled fire events from the control group. PCA analysis demonstrated the potential of PAHs to distinguish different sources of firefighters´ occupational exposure and of combining estimated health risk parameters with in vitro toxicities determined with human-breathable air collected during real-life scenarios. Overall, the participation in controlled fire events contributes to the respiratory health burden of firefighting forces. However, more studies are needed to corroborate these preliminary findings, explore the respiratory toxicological mechanisms, and support the implementation of preventive actions and mitigation strategies to pursue firefighters' health.

Metagenomic insights into the microbial cooperative networks of a benz(a)anthracene-7,12-dione degrading community from a creosote-contaminated soil

Genotoxicity of PAH-contaminated soils can eventually increase after bioremediation due to the formation and accumulation of polar transformation products, mainly oxygenated PAHs (oxy-PAHs). Biodegradation of oxy-PAHs has been described in soils, but information on the microorganisms and mechanisms involved is still scarce. Benz(a)anthracene-7,12-dione (BaAQ), a transformation product from benz(a)anthracene frequently detected in soils, presents higher genotoxic potential than its parent PAH. Here, using sand-in-liquid microcosms we identified a specialized BaAQ-degrading subpopulation in a PAH-contaminated soil. A BaAQ-degrading microbial consortium was obtained by enrichment in sand-in-liquid cultures with BaAQ as sole carbon source, and its metagenomic analysis identified members of Sphingobium, Stenotrophomonas, Pusillimonas, Olivibacter, Pseudomonas, Achromobacter, and Hyphomicrobiales as major components. The integration of data from metabolomic and metagenomic functional gene analyses of the consortium revealed that the BaAQ metabolic pathway was initiated by Baeyer-Villiger monooxygenases (BVMOs). The presence of plasmid pANTQ-1 in the metagenomic sequences, identified in a previous multi-omic characterization of a 9,10-anthraquinone-degrading isolate recovered from the same soil, suggested the occurrence of a horizontal gene transfer event. Further metagenomic analysis of the BaAQ-degrading consortium also provided insights into the potential roles and interactions within the consortium members. Several potential auxotrophies were detected, indicating that relevant nutritional interdependencies and syntrophic associations were taking place within the community members, not only to provide suitable carbon and energy sources, but also to supply essential nutrients and cofactors. Our work confirms the essential role that BVMO may play as a detoxification mechanism to mitigate the risk posed by oxy-PAH formation during bioremediation of contaminated soils.

Characterizing Benzo[a]pyrene Adducts in Transfer RNAs Using Liquid Chromatography Coupled with Tandem Mass Spectrometry (LC-MS/MS)

The activated forms of the environmental pollutant benzo[a]pyrene (B[a]P), such as benzo[a]pyrene diol epoxide (BPDE), are known to cause damage to genomic DNA and proteins. However, the impact of BPDE on ribonucleic acid (RNA) remains unclear. To understand the full spectrum of potential BPDE-RNA adducts formed, we reacted ribonucleoside standards with BPDE and characterized the reaction products using liquid chromatography coupled with tandem mass spectrometry (LC-MS/MS). To understand the potential types of adducts that could form with biological RNAs, eukaryotic transfer RNAs (tRNAs) were also reacted with BPDE. The isolation and analysis of the modified and adducted ribonucleosides using LC-MS/MS revealed several BPDE derivatives of post-transcriptional modifications. The approach outlined in this work enables the identification of RNA adducts from BPDE, which can pave the way for understanding the potential impacts of such adducts on the higher-order structure and function of modified RNAs.

Oxidation 1-methyl naphthalene based on the synergy of environmentally persistent free radicals (EPFRs) and PAHs in particulate matter (PM) surface

Studies of the environmental fate through the interactions of particle-associated polycyclic aromatic hydrocarbons (PAHs) with environmentally persistent free radicals (EPFRs) are presented. The formation of PAHs and EPFRs typically occurs side by side during combustion-processes. The laboratory simulation studies of the model PAH molecule 1-Methylnaphthalene (1-MN) interaction with model EPFRs indicate a transformational synergy between these two pollutants due to mutual and matrix interactions. EPFRs, thorough its redox cycle result in the oxidation of PAHs into oxy-/hydroxy-PAHs. EPFRs have been shown before to produce OH radical during its redox cycle in aqueous media and this study has shown that produced OH radical can transform other PM constituents resulting in alteration of PM chemistry. In model PM, EPFRs driven oxidation process of 1-MN produced 1,4-naphthoquinone, 1-naphthaldehyde, 4-hydroxy-4-methylnaphthalen-1-one, and various isomers of (hydroxymethyl) naphthalene. Differences were observed in oxidation product yields, depending on whether EPFRs and PAHs were cohabiting the same PM or present on separate PM. This effect is attributed to the OH radical concentration gradient as a factor in the oxidation process, further strengthening the hypothesis of EPFRs' role in the PAH oxidation process. This finding is revealing new environmental role of EPFRs in a natural degradation process of PAHs. Additionally, it points to implications of such PM surface chemistry in the changing mobility of PAHs into an aqueous medium, thus increasing their bioavailability.

Lung cancer associated with combustion particles and fine particulate matter (PM2.5) - The roles of polycyclic aromatic hydrocarbons (PAHs) and the aryl hydrocarbon receptor (AhR)

Air pollution is the leading cause of lung cancer after tobacco smoking, contributing to 20% of all lung cancer deaths. Increased risk associated with living near trafficked roads, occupational exposure to diesel exhaust, indoor coal combustion and cigarette smoking, suggest that combustion components in ambient fine particulate matter (PM2.5), such as polycyclic aromatic hydrocarbons (PAHs), may be central drivers of lung cancer. Activation of the aryl hydrocarbon receptor (AhR) induces expression of xenobiotic-metabolizing enzymes (XMEs) and increase PAH metabolism, formation of reactive metabolites, oxidative stress, DNA damage and mutagenesis. Lung cancer tissues from smokers and workers exposed to high combustion PM levels contain mutagenic signatures derived from PAHs. However, recent findings suggest that ambient air PM2.5 exposure primarily induces lung cancer development through tumor promotion of cells harboring naturally acquired oncogenic mutations, thus lacking typical PAH-induced mutations. On this background, we discuss the role of AhR and PAHs in lung cancer development caused by air pollution focusing on the tumor promoting properties including metabolism, immune system, cell proliferation and survival, tumor microenvironment, cell-to-cell communication, tumor growth and metastasis. We suggest that the dichotomy in lung cancer patterns observed between smoking and outdoor air PM2.5 represent the two ends of a dose-response continuum of combustion PM exposure, where tumor promotion in the peripheral lung appears to be the driving factor at the relatively low-dose exposures from ambient air PM2.5, whereas genotoxicity in the central airways becomes increasingly more important at the higher combustion PM levels encountered through smoking and occupational exposure.

Humic-like Substances (HULIS) in Ship Engine Emissions: Molecular Composition Effected by Fuel Type, Engine Mode, and Wet Scrubber Usage

Humic-like substances (HULIS), known for their substantial impact on the atmosphere, are identified in marine diesel engine emissions obtained from five different fuels at two engine loads simulating real world scenarios as well as the application of wet sulfur scrubbers. The HULIS chemical composition is characterized by electrospray ionization (ESI) ultrahigh resolution mass spectrometry and shown to contain partially oxidized alkylated polycyclic aromatic compounds as well as partially oxidized aliphatic compounds, both including abundant nitrogen- and sulfur-containing species, and clearly different to HULIS emitted from biomass burning. Fuel properties such as sulfur content and aromaticity as well as the fuel combustion efficiency and engine mode are reflected in the observed HULIS composition. When the marine diesel engine is operated below the optimum engine settings, e.g., during maneuvering in harbors, HULIS-C emission factors are increased (262-893 mg kg-1), and a higher number of HULIS with a shift toward lower degree of oxidation and higher aromaticity is detected. Additionally, more aromatic and aliphatic CHOS compounds in HULIS were detected, especially for high-sulfur fuel combustion. The application of wet sulfur scrubbers decreased the HULIS-C emission factors by 4-49% but also led to the formation of new HULIS compounds. Overall, our results suggest the consideration of marine diesel engines as a relevant regional source of HULIS emissions.

Complex polycyclic aromatic compound mixtures in PM2.5 in a Chinese megacity: Spatio-temporal variations, toxicity, and source apportionment

Polycyclic aromatic compounds (PACs) are important toxic organic components in fine particulate matter (PM2.5), whereas the links between PM2.5 toxicity and associated PACs in ambient air are poorly understood. This study investigated the spatial-temporal variations of PACs in PM2.5 collected from 11 sampling sites across a Chinese megacity and characterized the reactive oxygen species (ROS) generation and cytotoxicity induced by organic extracts of PM2.5 based on cellular assays. The extra trees regression model based on machine learning and ridge regression were used to identify the key toxicants among complex PAC mixtures. The total concentrations of these PACs varied from 2.12 to 71.7 ng/m3 across the study city, and polycyclic aromatic hydrocarbons (PAHs) are the main PACs. The spatial variations of the toxicological indicators generally resembled those of the PAC concentrations, and the PM2.5 related to waste treatment facilities exhibited the strongest toxic potencies. The ROS generation was highly correlated with high molecular weight PAHs (MW302 PAHs), followed by PAHs with MW<302 amu and oxygenated PAHs, but not with nitrated PAHs and the plastics additives. The cell mortality showed weak correlations with these organic constituents. The associations between the biological endpoints and these PM2.5-bound contaminants were further confirmed by exposure to authentic chemicals. Four primary sources of PACs were identified, among which coal and biomass combustion sources (30.2% of the total PACs) and industrial sources (31.0%) were predominant. PACs emitted from industrial sources were highly associated with ROS generation in this city. Our findings highlight the potent ROS-generating potential of MW302 PAHs and the importance of industrial sources contributing to PM2.5 toxicity in this megacity, raising public concerns and further administration.

Benzo [a] pyrene-loaded aged polystyrene microplastics promote colonic barrier injury via oxidative stress-mediated notch signalling

The adsorption of toxic substances on polystyrene microplastics (PSMPs) can modify their biological toxicity and exacerbate the threat to human health. The effects of benzo [a] pyrene (B (a) P)-loaded aged PSMPs on colonic barrier integrity remains unclear. Here, we showed that binding environmentally relevant concentrations of B (a) P alteredl̥ the physicochemical features and markedly enhanced the toxicity of PSMPs. Compared to pristine PSMP, PSMP@B (a) P promoted colonic barrier degradation, body weight loss, colon length shortening, oxidative stress (OS), autophagy, inflammation, and bacterial translocation. Microplastic (MP) exposure induced injury to the colon barrier, including tight junction (TJ) and mucosal barriers, via overactivation of the Notch signalling pathway under increased OS in mice and intestinal organoids. Notably, PSMP@B (a) P exposure exacerbated damage to TJ and the mucosal barrier via the overproduction of reactive oxygen species (ROS), which could be related to the release of B (a) P from PSMP@B (a) P induced by the acidic environment of autophagosomes, which in turn exert synergistic toxic effects with PSMPs. Our study elucidates some of the potential molecular mechanisms by which B (a) P enhances PSMP-related intestinal toxicity, which provides a potential therapeutic approach for diseases caused by PSMP@B (a)P and PSMP pollution.

A yearlong monitoring campaign of polycyclic aromatic compounds and other air pollutants at three sites in Sweden: Source identification, in vitro toxicity and human health risk assessment

Air pollution is a complex mixture of gases and particulate matter (PM) with local and non-local emission sources, resulting in spatiotemporal variability in concentrations and composition, and thus associated health risks. To study this in the greater Stockholm area, a yearlong monitoring campaign with in situ measurements of PM₁₀, PM₁, black carbon, NO_x, O₃, and PM₁₀-sampling was performed. The locations included an Urban and a Rural background site and a Highway site. Chemical analysis of PM₁₀ was performed to quantify monthly levels of polycyclic aromatic compounds (PACs), which together with other air pollution data were used for source apportionment and health risk assessment. Organic extracts from PM₁₀ were tested for oxidative potential in human bronchial epithelial cells. Strong seasonal patterns were found for most air pollutants including PACs, with higher levels during the winter months than summer e.g., highest levels of PM₁₀ were detected in March at the Highway site (33.2 μg/m³) and lowest in May at the Rural site (3.6 μg/m³). In general, air pollutant levels at the sites were in the order Highway > Urban > Rural. Multivariate analysis identified several polar PACs, including 6H-Benzo[cd]pyren-6-one, as possible discriminatory markers for these sites. The main sources of particulate pollution for all sites were vehicle exhaust and biomass burning emissions, although diesel exhaust was an important source at the Highway site. In vitro results agreed with air pollutant levels, with higher oxidative potential from the winter samples. Estimated lung cancer cases were in the order PM₁₀ > NO₂ > PACs for all sites, and with less evident seasonal differences than in vitro results. In conclusion, our study presents novel seasonal data for many PACs together with air pollutants more traditionally included in air quality monitoring. Moreover, seasonal differences in air pollutant levels correlated with differences in toxicity in vitro.

Occurrence and spatiotemporal distribution of PAHs and OPAHs in urban agricultural soils from Guangzhou City, China

The occurrence of polycyclic aromatic hydrocarbon (PAH) derivatives in the environment is of growing concern because they exhibit higher toxicity than their parent PAHs. This study evaluated the large-scale occurrence and spatiotemporal distribution of 16 PAHs and 14 oxygenated PAHs (OPAHs) in urban agricultural soils from seven districts of Guangzhou City, China. Linear correlation analysis was conducted to explore the relationship between PAH and OPAH occurrence and a series of parameters. The compositional analysis, principal component analysis, diagnostic ratios, and principal component analysis coupled with a multiple linear regression model were used to identify the sources of PAHs and OPAHs in the soils. The average concentrations of ΣPAHs and ΣOPAHs (59.6 ± 31.1-213 ± 115.5 μg/kg) during the flood season were significantly higher than those during the dry season (42.1 ± 13.3-157.2 ± 98.2 μg/kg), which were due to relatively strong wet deposition during the flood season and weak secondary reactions during the dry season. Linear correlation analysis showed that soil properties, industrial activities, and agricultural activities (r = 0.27-0.96, p < 0.05) were responsible for the spatial distribution of PAHs during the dry season. The PAH distribution was mainly affected by precipitation during the flood season. The concentrations of ΣOPAHs were only related to the soil properties during the dry season because their occurrence was sensitive to secondary reactions, climate and meteorological conditions, and their water solubility. Our results further showed that coal combustion and traffic emissions were the dominant origins of PAHs and OPAHs during both the seasons. Wet deposition and runoff-induced transport also contributed to PAH and OPAH occurrence during the flood season. The results of this study can improve our understanding of the environmental risks posed by PAHs and OPAHs.

Co-occurrence of polycyclic aromatic hydrocarbons and their oxygenated derivatives in indoor dust from various microenvironments in Guangzhou, China: levels, sources, and potential human health risk

For decades, the presence and potential health risk of polycyclic aromatic hydrocarbons (PAHs) in indoor dust have been extensively investigated while with limited attention to oxygenated PAHs (OPAHs). In this study, we collected 45 indoor dust from four microenvironments in Guangzhou City, China, and then focused on the co-occurrence of 16 PAHs and 8 OPAHs and their potential carcinogenic risk to humans. The ΣPAHs concentrations, dominated by 4-6 ring PAHs, ranged from 1761 to 14,290 ng/g (mean of 6058 ng/g) without significant difference in the different microenvironments (Tukey, p > 0.05). The OPAHs were observed with concentrations from 250 to 5160 ng/g (mean of 1646 ng/g), and anthraquinone (AQ) was identified as the main OPAHs with significantly high levels in the residential environment than in instrumental rooms. Notably, AQ dominated over the other target analytes in dust in this study. Our results indicated that PAHs and OPAHs in indoor dust were from outdoor environments, which mainly originated from vehicular exhaust and biomass/coal combustion. A potential cancer risk of PAHs and OPAHs to local adults and children was observed via inhalation, ingestion, and dermal absorption, with the main contribution from benzo[a]pyrene and dibenz[a,h]anthracene.

In vitro genotoxicity potential investigation of 7 oxy-PAHs

Air pollutants include many compounds among them oxygenated polycyclic aromatic hydrocarbons (oxy-PAHs). As they are suspected to generate DNA damage and mutagenicity, an understanding of their mode of action could highlight a carcinogenic potential risk in exposed population. In this article, a prospective study on seven oxy-PAHs selected in terms of occurrence in the environment was conducted on mutagenicity, genotoxicity, and cytotoxicity potentials using in vitro assays including Ames test on five strains, kinetic analysis of cytotoxicity and apoptosis, phosphorylation of histone H2AX, and p53 induction assays on human lung cell line BEAS-2B. Ames test demonstrated that mutagenicity pattern depended on the oxy-PAH tested. Except for BAQ, all oxy-PAHs tested gave mutagenic effect, in the absence and/or in the presence of metabolic activation (S9 fraction). At 24 h of exposure, the majority of oxy-PAHs induced γ-H2AX in BEAS-2B cells and/or phosphorylation of p53 at serine 15 and cell death at highest tested concentrations. Although 9,10-AQ and B[b]FO were mutagenic in bacteria, they failed to induce any of the other genotoxicity biomarkers. In comparison with the benzo[a]pyrene, all oxy-PAHs were less potent in terms of genotoxic potential at the same concentration. These results highlighted the genotoxic and mutagenic potential of these oxy-PAHs and provide preliminary information concerning their possible mechanism of action for toxicity, contributing to a better evaluation of the real associated health risks for human and environment.

Oxygenated and Nitrated Polycyclic Aromatic Hydrocarbons: Sources, Quantification, Incidence, Toxicity, and Fate in Soil—A Review Study

The genotoxicity, mutagenesis, and carcinogenic effects of polycyclic aromatic hydrocarbon (PAH) derivatives may exceed the parent PAHs. However, their influence on the soil environment has not been explored to a large extent. Oxygenated polycyclic aromatic hydrocarbons (OPAHs) and nitrated polycyclic aromatic hydrocarbons (NPAHs) are typical polar substituted compounds. We offer a review of the literature on the sources, quantification, incidence, toxicity, and transport of these compounds in soil. Although their environmental concentrations are lower than those of their parent compounds, they exert higher toxicity. Both types of substances are basically related to carcinogenesis. OPAHs are not enzymatically activated and can generate reactive oxygen species in biological cells, while NPAHs have been shown to be mutagenic, genotoxic, and cytotoxic. These compounds are largely derived from the transformation of PAHs, but they behave differently in soil because of their higher molecular weight and dissimilar adsorption mechanisms. Therefore, specialized knowledge of model derivatives is required. We also made recommendations for future directions based on existing research. It is expected that the review will trigger scientific discussions and provide a research basis for further study on PAH derivatives in the soil environment.

Oxygenated polycyclic aromatic hydrocarbons in food: toxicity, occurrence and potential sources

Oxygenated polycyclic aromatic hydrocarbons (OPAHs) are polycyclic aromatic hydrocarbons (PAHs) functionalized with at least one carbonyl group and are generally thought to be more toxic than PAHs. In this review, the physical-chemical properties, toxicity, occurrence, and potential sources of OPAHs in food were comprehensively discussed. The toxicities of 1,2-naphthoquinone, 1,4-naphthoquinone, 6H-benzo[cd]pyren-6-one, benzo[a]anthracene-7,12-quinone and 9,10-phenanthrenequinone were prominent among the OPAHs. Both 1,4-naphthoquinone and 1,2-naphthoquinone exhibited strong genotoxicity, cytotoxicity, and developmental toxicity. 6H-benzo[cd]pyren-6-one and benzo[a]anthracene-7,12-quinone showed high genotoxicity and cardiovascular toxicity. Although 9,10-phenanthrenequinone showed no genotoxicity, it exhibited almost the strongest cytotoxicity. For the majority of foods, the concentrations of OPAHs and PAHs were on the same order of magnitude. OPAHs tend to be positively correlated with the corresponding PAH concentrations in oil and fried food, while for barbequed food and seafood, no obvious correlation was found. In addition, 9-fluorenone, 9,10-anthraquinone, benzanthrone and 1,2-acenaphthenequinone had high abundance in food. Environmental pollution, food composition, storage conditions, heating methods, and other treatments influence the accumulation of OPAHs in food. Furthermore, oxygen and water played an important role in the transformation from PAHs to OPAHs. In short, this review guides the evaluation and further reduction of OPAH-related health risks in food.

Influences of polycyclic aromatic hydrocarbon on the epigenome toxicity and its applicability in human health risk assessment

The existence of polycyclic aromatic hydrocarbons (PAHs) in ambient air is an escalating concern worldwide because of their ability to cause cancer and induce permanent changes in the genetic material. Growing evidence implies that during early life-sensitive stages, the risk of progression of acute and chronic diseases depends on epigenetic changes initiated by the influence of environmental cues. Several reports deciphered the relationship between exposure to environmental chemicals and epigenetics, and have known toxicants that alter the epigenetic states. Amongst PAHs, benzo[a]pyrene (B[a]P) is accepted as a group 1 cancer-causing agent by the International Agency for the Research on Cancer (IARC). B[a]P is a well-studied pro-carcinogen that is metabolically activated by the aryl hydrocarbon receptor (AhR)/cytochrome P450 pathway. Cytochrome P450 plays a pivotal role in the stimulation step, which is essential for DNA adduct formation. Accruing evidence suggests that epigenetic alterations assume a fundamental part in PAH-promoted carcinogenesis. This interaction between PAHs and epigenetic factors results in an altered profile of these marks, globally and locus-specific. Some of the epigenetic changes due to exposure to PAHs lead to increased disease susceptibility and progression. It is well understood that exposure to environmental carcinogens, such as PAH triggers disease pathways through changes in the genome. Several evidence reported due to the epigenome-wide association studies, that early life adverse environmental events may trigger widespread and persistent variations in transcriptional profiling. Moreover, these variations respond to DNA damage and/or a consequence of epigenetic modifications that need further investigation. Growing evidence has associated PAHs with epigenetic variations involving alterations in DNA methylation, histone modification, and micro RNA (miRNA) regulation. Epigenetic alterations to PAH exposure were related to chronic diseases, such as pulmonary disease, cardiovascular disease, endocrine disruptor, nervous system disorder, and cancer. This hormetic response gives a novel perception concerning the toxicity of PAHs and the biological reaction that may be a distinct reliance on exposure. This review sheds light on understanding the latest evidence about how PAHs can alter epigenetic patterns and human health. In conclusion, as several epigenetic change mechanisms remain unclear yet, further analyses derived from PAHs exposure must be performed to find new targets and disease biomarkers. In spite of the current limitations, numerous evidence supports the perception that epigenetics grips substantial potential for advancing our knowledge about the molecular mechanisms of environmental toxicants, also for predicting health-associated risks due to environmental circumstances exposure and individual susceptibility.

Effects of individual and combined polystyrene nanoplastics and phenanthrene on the enzymology, physiology, and transcriptome parameters of rice (Oryza sativa L.)

Owing to their wide distribution, easy production, and resistance to degradation, microplastics (MPs) represent a globally emerging group of pollutants of concern. Furthermore, their decomposition can result in the generation of nanoplastics (NPs), which cause further environmental issues. Currently, the impact of the combination of these plastics with other organic pollutants on crop growth remains poorly investigated. In this study, a hydroponic experiment was conducted for seven days to evaluate the effects of 50 nm, 50 mg/L polystyrene (PS), and 1 mg/L phenanthrene (Phe) on the growth of rice plants. The results revealed that both Phe and PS inhibited growth and improved the antioxidant potential of rice. Relative to Phe alone, exposure to a combination of PS and Phe reduced Phe accumulation in the roots and shoots by 67.73% and 36.84%, respectively, and decreased the pressure on the antioxidant system. Exposure to Phe alone destroyed the photosynthetic system of rice plant leaves, whereas a combination of PS and Phe alleviated this damage. Gene Ontology (GO) analysis of the rice transcriptomes revealed that detoxification genes and phenylalanine metabolism were suppressed under exposure to Phe, which consequently diminished the antioxidant capacity and polysaccharide synthesis in rice plants. Kyoto Encyclopaedia of Genes and Genomes (KEGG) transcriptome analysis revealed that the combined presence of both PS and Phe improved photosynthesis and energy metabolism and alleviated the toxic effects of Phe by altering the carbon fixation pathway and hormone signal transduction in rice plants. The combination of PS and Phe also prevented Phe-associated damage to rice growth. These findings improve our understanding of the effects of MP/NPs and polycyclic aromatic hydrocarbons on crops.

Household cooking oil type and risk of oral micronucleus frequency in Chinese nonsmokers

Household animal fat has been linked to increased incidence of cancers compared with vegetable fat. However, few epidemiological studies have associated these two cooking oil types with precancerous genotoxic effects, such as occurrence of micronuclei (MN). This study aimed to explore the association between oral MN frequency and household cooking oil type and whether the association can be attributed to polycyclic aromatic hydrocarbons (PAHs). We collected information about individual cooking oil use, measured genotoxic effects by MN tests and urinary PAHs metabolites (OHPAHs) in 245 nonsmokers. The associations between household cooking oil type and MN frequency and OHPAHs were analyzed using generalized linear models (GLMs) and logistic regression models, evaluating odds ratios and coefficient (95% confidence intervals) (ORs, 95% Cls; β, 95% Cls). The odds of animal fat consumers, rather than vegetable fat consumers, was positively associated with higher MN frequency (OR = 1.94, P < 0.05). The associations were discovered in participants only using kitchen ventilation (OR = 2.04, P < 0.05). Animal fat consumers had higher total OHPAHs than vegetable fat consumers (1.58 ± 0.22 mg/mol, Cr vs 1.20 ± 0.12 mg/mol, Cr; P = 0.028). Significant correlations were observed between total OHPAHs quartiles and increased MN frequency (β = 0.38, P-trend = 0.026). After stratifying by household cooking oil type, sensitivity analyses showed that the positive association between total OHPAHs quartiles and increased MN frequency was only observed in animal fat consumers (β = 0.61, P-trend = 0.030). In conclusion, usage of household animal fat was associated with an increased odds of oral MN frequency in Chinese nonsmokers and the odds correlated with increased PAHs exposure. This finding supplemented evidence associating cooking oil type with genotoxic effects and explained its association with PAHs exposure.

Assessment of the association of exposure to polycyclic aromatic hydrocarbons, oxidative stress, and inflammation: A cross-sectional study in Augsburg, Germany

BACKGROUND

Exposure to polycyclic aromatic hydrocarbons (PAHs) has been linked to acute and chronic health effects through the suggested pathways of oxidative stress and inflammation. However, evidence is still limited. We aimed to investigate jointly the relationship of PAHs, oxidative stress, and inflammation.

METHODS

We measured 13 biomarkers of PAH exposure (n = 6: hydroxylated polycyclic aromatic hydrocarbons, [OH-PAHs]), oxidative stress (n = 6: malondialdehyde (MDA); 8-hydroxy-2'-deoxyguanosine (8-OHdG); and 4 representatives of the compound class of F_2α-isoprostanes) in urine, and inflammation (n = 1: high-sensitivity C-reactive protein, [hs-CRP]) in serum from 400 participants at the second follow-up (2013/2014) of the German KORA survey S4. Multiple linear regression models were applied to investigate the interplay between biomarkers.

RESULTS

Concentrations of biomarkers varied according to sex, age, smoking status, season, and a history of obesity, diabetes, or chronic kidney disease. All OH-PAHs were significantly and positively associated with oxidative stress biomarkers. An interquartile range (IQR) increase in sum OH-PAHs was associated with a 13.3% (95% CI: 9.9%, 16.9%) increase in MDA, a 6.5% (95% CI: 3.5%, 9.6%) increase in 8-OHdG, and an 8.4% (95% CI: 6.6%, 11.3%) increase in sum F_2α-isoprostanes. Associations were more pronounced between OH-PAHs and F_2α-isoprostanes but also between OH-PAHs and 8-OHdG for participants with potential underlying systemic inflammation (hs-CRP ≥ 3 mg/L). We observed no association between OH-PAHs and hs-CRP levels. While 8-OHdG was significantly positively associated with hs-CRP (13.7% [95% CI: 2.2%, 26.5%] per IQR increase in 8-OHdG), F_2α-isoprostanes and MDA indicated only a positive or null association, respectively.

CONCLUSION

The results of this cross-sectional study suggest, at a population level, that exposure to PAHs is associated with oxidative stress even in a low exposure setting. Oxidative stress markers, but not PAHs, were associated with inflammation. Individual risk factors were important contributors to these processes and should be considered in future studies. Further longitudinal studies are necessary to investigate the causal chain of the associations.

Oxygenated polycyclic aromatic hydrocarbons in the surface water environment: Occurrence, ecotoxicity, and sources

Oxygenated polycyclic aromatic hydrocarbons (OPAHs) have been ubiquitously detected in atmospheric, soil, sediment, and water environments, some of which show higher concentrations and toxicities than the parent polycyclic aromatic hydrocarbons (PAHs). The occurrence, source, fate, risks and methods of analysis for OPAHs in the atmosphere, soil, and the whole environment (comprising the atmosphere, soil, water, and biota) have been reviewed, but reviews focusing on OPAHs in the water environment have been lacking. Due to the higher polarity and water solubility of OPAHs than PAHs, OPAHs exist preferentially in water environments. In this review, the occurrence, ecological toxicity and source of OPAHs in surface water environments are investigated in detail. Most OPAHs show higher concentrations than the corresponding PAHs in surface water environments. OPAHs pose non-ignorable ecological risks to surface water ecosystems. Wastewater treatment plant effluent, atmospheric deposition, surface runoff, photochemical and microbiological transformation, and sediment release are possible sources for OPAHs in surface water. This review will fill important knowledge gaps on the migration and transformation of typical OPAHs in multiple media and their environmental impact on surface water environments. Further studies on OPAHs in the surface environment, including their ecotoxicity with the co-existing PAHs and mass flows of OPAHs from atmospheric deposition, surface runoff, transformation from PAHs, and sediment release, are also encouraged.

Role of the Synergistic Interactions of Environmental Pollutants in the Development of Cancer

There is a growing awareness that the large number of environmental pollutants we are exposed to on a daily basis are causing major health problems. Compared to traditional studies that focus on individual pollutants, there are relatively few studies on how pollutants mixtures interact. Several studies have reported a relationship between environmental pollutants and the development of cancer, even when pollutant levels are below toxicity reference values. The possibility of synergistic interactions between different pollutants could explain how even low concentrations can cause major health problems. These intricate that molecular interactions can occur through a wide variety of mechanisms, and our understanding of the physiological effects of mixtures is still limited. The purpose of this paper is to discuss recent reports that address possible synergistic interactions between different types of environmental pollutants that could promote cancer development. Our literature studies suggest that key biological pathways are frequently implicated in such processes. These include increased production of reactive oxygen species, activation by cytochrome P450, and aryl hydrocarbon receptor signaling, among others. We discuss the need to understand individual pathological vulnerability not only in relation to basic genetics and gene expression, but also in terms of measurable exposure to contaminants. We also mention the need for significant improvements in future studies using a multitude of disciplines, such as the development of high-throughput study models, better tools for quantifying pollutants in cancer patients, innovative pharmacological and toxicological studies, and high-efficiency computer analysis, which allow us to analyze the molecular mechanisms of mixtures.

Screening of the Toxicity of Polystyrene Nano- and Microplastics Alone and in Combination with Benzo(a)pyrene in Brine Shrimp Larvae and Zebrafish Embryos

The occurrence of nanoplastics (NPs) and microplastics (MPs) in aquatic ecosystems and their capacity to sorb hydrophobic pollutants is nowadays an issue of great concern. This study aimed to assess the potential bioavailability and acute toxicity of polystyrene (PS) NPs (50 and 500 nm) and of MPs (4.5 µm), alone and with sorbed benzo(a)pyrene (B(a)P), in the embryo/larval stages of brine shrimps and zebrafish. Exposure to pristine plastics up to 50.1 mg PS/L did not cause significant impact on brine shrimp survival, while some treatments of plastics-B(a)P and all concentrations of B(a)P (0.1–10 mg/L) resulted acutely toxic. In zebrafish, only the highest concentrations of MPs-B(a)P and B(a)P caused a significant increase of malformation prevalence. Ingestion of NPs was observed by 24–48 h of exposure in the two organisms (from 0.069 to 6.87 mg PS/L). In brine shrimps, NPs were observed over the body surface and within the digestive tract, associated with feces. In zebrafish, NPs were localized in the eyes, yolk sac, and tail at 72 h, showing their capacity to translocate and spread into the embryo. MP ingestion was only demonstrated for brine shrimps. In zebrafish embryos exposed to plastics-B(a)P, B(a)P appeared in the yolk sac of the embryos. The presence of B(a)P was also noticeable in brine shrimps exposed to 500 nm NPs-B(a)P. In conclusion, NPs entered and spread into the zebrafish embryo and PS NPs, and MPs were successful vectors of B(a)P to brine shrimp and zebrafish embryos. Particle size played a significant role in explaining the toxicity of plastics–B(a)P. Our study provides support for the idea that plastics may pose a risk to aquatic organisms when combined with persistent organic pollutants such as B(a)P.

How does the brown mussel Perna perna respond to environmental pollution? A review on pollution biomarkers

The brown mussel Perna perna (Linnaeus, 1758) is a valuable resource for aquaculture in tropical and subtropical coastal regions. It presents desirable characteristics for biomonitoring, including being sessile, widely distributed and abundant, and is a filter-feeder able to accumulate several classes of pollutants (e.g., metals, hydrocarbons, among others). Mussels' biological responses to pollution exposure can be measured as biomarkers, which include alterations ranging from molecular to physiological levels, to estimate the degree of environmental contamination and its effects on biota. This full review compiles two decades (2000-2020) of literature concerning biological effects on P. perna mussel caused by environmental pollutants (i.e., metals, hydrocarbons, and emerging pollutants), considering environmental and farm-based biomonitoring. Biochemical markers related to mussels' oxidative status were efficient for the biomonitoring of metals (i.e., antioxidant enzymes associated with oxidative damage in biomolecules). Genotoxicity and cytotoxicity indicators (i.e., comet, micronucleus, and neutral red assays) provided a depiction of hydrocarbon contamination. The neutral red assay gave a time-concentration cytotoxic response to a wide range of pollutants, including emerging pollutants (e.g., pharmaceuticals and biocides) and hydrocarbons. Perna perna hemocyte parameters provided a useful approach for biocide biomonitoring. This paper summarizes useful biomarkers from molecular to physiological levels in this mussel species used to identify and quantify the degree of coastal pollution. An integrated biomarker analysis may provide a way to overcome possible biomarker variations and assess multi-polluted sites. Nevertheless, it is necessary to investigate biomarker variations according to natural factors (e.g., season and gonad maturation stage) to standardize them for trustworthy biomonitoring.

Toxicity screening of air extracts representing different source sectors in the Greater Toronto and Hamilton areas: In vitro oxidative stress, pro-inflammatory response, and toxicogenomic analysis

In the present study, the suitability and sensitivity of different in vitro toxicity endpoints were determined to evaluate and distinguish the specific contributions of polycyclic aromatic carbon (PAC) mixtures from various sites in Toronto (Canada), to pulmonary toxicity. Air samples were collected for two-month periods from April 2014 to March 2015 from one location, and from August 2016 to August 2017 from multiple locations reflecting different geographical areas in Toronto, and the Greater Toronto Area, with varying source emissions including background, traffic, urban, industrial and residential sites. Relative concentrations of PACs and their derivatives in these air samples were characterised. In vitro cytotoxicity, pro-inflammatory, and oxidative stress assays were employed to assess the acute pulmonary effects of urban-air-derived air pollutants. In addition, global transcriptional profiling was utilized to understand how these chemical mixtures exert their harmful effects. Lastly, the transcriptomic data and the chemical profiles for each site and season were used to relate the biological response back to individual constituents. Site-specific responses could not be derived; however, the Spring season was identified as the most responsive through benchmark concentration analysis. A combination of correlational analysis and principal component analysis revealed that nitrated and oxygenated polycyclic aromatic hydrocarbons (PAHs) drive the response at lower concentrations while specific PAHs drive the response at the highest concentration tested. Unsubstituted PAHs are the current targets for analysis as priority pollutants. The present study highlights the importance of by-products of PAH degradation in the assessment of risk. The study also demonstrates the usefulness of in vitro toxicity assays to derive meaningful data in support of risk assessment.

A Classification Model to Identify Direct-Acting Mutagenic Polycyclic Aromatic Hydrocarbon Transformation Products

Polycyclic aromatic hydrocarbons (PAHs) are a complex group of environmental contaminants, many having long environmental half-lives. As these compounds degrade, the changes in their structure can result in a substantial increase in mutagenicity compared to the parent compound. Over time, each individual PAH can potentially degrade into several thousand unique transformation products, creating a complex, constantly evolving set of intermediates. Microbial degradation is the primary mechanism of their transformation and ultimate removal from the environment, and this process can result in mutagenic activation similar to the metabolic activation that can occur in multicellular organisms. The diversity of the potential intermediate structures in PAH-contaminated environments renders hazard assessment difficult for both remediation professionals and regulators. A mixture of structural and energetic descriptors has proven effective in existing studies for classifying which PAH transformation products will be mutagenic. However, most existing studies of environmental PAH mutagens primarily focus on nitrogenated derivatives, which are prevalent in the atmosphere and not as relevant in soil. Additionally, PAH products commonly found in the environment can range from as large as five rings to as small as a single ring, requiring a broadly inclusive methodology to comprehensively evaluate mutagenic potential. We developed a combination of supervised and unsupervised machine learning methods to predict environmentally induced PAH mutagenicity with improved performance over currently available tools. K-means clustering with principal component analysis allows us to identify molecular clusters that we hypothesize to have similar mechanisms of action. Recursive feature elimination identifies the most influential descriptors. The cluster-specific regression outperforms available classifiers in predicting direct-acting mutagens resulting from the microbial biodegradation of PAHs and provides direction for future studies evaluating the environmental hazards resulting from PAH biodegradation.

The joint toxicity of polyethylene microplastic and phenanthrene to wheat seedlings

Due to wide distribution, easy production, and difficult degradation, microplastic pollution has become a new environmental problem that has attracted worldwide attention. However, there is little information about the effects of microplastics in soil and their combined pollution with other organic pollutants on crop growth. In this study, we conducted soil culture experiments to evaluate the effects of polyethylene microplastics (PE-MPs) (0.5%, 1%, 2%, 5%, 8% w/w) individual and combined with phenanthrene (100 mg kg^-1) on wheat growth for 15 days. Under PE-MPs alone and combined with phenanthrene exposure, dose-dependent toxicities in biomass, shoot height and root length were observed. Over 1% PE-MPs stimulate wheat root elongation. Compared with single phenanthrene treatment, the co-contamination of PE-MPs and phenanthrene reduces the accumulation of phenanthrene in wheat roots and leaves. In the range of 0-5%, the activity of wheat root antioxidant enzymes increases with increasing PE-MP concentration; but both phenanthrene and high concentrations (8%) of PE-MPs cause damage to the antioxidant system in wheat roots. In the presence or absence of phenanthrene, the photosynthetic pigment concentration of wheat leaves shows a dual concentration effect of low promotion and high inhibition under PE-MPs stress. The single pollution of PE-MPs destroys the photosynthetic system of wheat leaves, while the co-contamination of PE-MPs and phenanthrene exacerbates this destruction. Therefore, the co-contamination of PE-MPs and phenanthrene causes greater damage to wheat growth. Our findings can help to evaluate the individual and comprehensive toxicity of microplastics and polycyclic aromatic hydrocarbons to crops.

Impact of Polycyclic Aromatic Hydrocarbon Accumulation on Oyster Health

In the past decade, the Deepwater Horizon oil spill triggered a spike in investigatory effort on the effects of crude oil chemicals, most notably polycyclic aromatic hydrocarbons (PAHs), on marine organisms and ecosystems. Oysters, susceptible to both waterborne and sediment-bound contaminants due to their filter-feeding and sessile nature, have become of great interest among scientists as both a bioindicator and model organism for research on environmental stressors. It has been shown in many parts of the world that PAHs readily bioaccumulate in the soft tissues of oysters. Subsequent experiments have highlighted the negative effects associated with exposure to PAHs including the upregulation of antioxidant and detoxifying gene transcripts and enzyme activities such as Superoxide dismutase, Cytochrome P450 enzymes, and Glutathione S-transferase, reduction in DNA integrity, increased infection prevalence, and reduced and abnormal larval growth. Much of these effects could be attributed to either oxidative damage, or a reallocation of energy away from critical biological processes such as reproduction and calcification toward health maintenance. Additional abiotic stressors including increased temperature, reduced salinity, and reduced pH may change how the oyster responds to environmental contaminants and may compound the negative effects of PAH exposure. The negative effects of acidification and longer-term salinity changes appear to add onto that of PAH toxicity, while shorter-term salinity changes may induce mechanisms that reduce PAH exposure. Elevated temperatures, on the other hand, cause such large physiological effects on their own that additional PAH exposure either fails to cause any significant effects or that the effects have little discernable pattern. In this review, the oyster is recognized as a model organism for the study of negative anthropogenic impacts on the environment, and the effects of various environmental stressors on the oyster model are compared, while synergistic effects of these stressors to PAH exposure are considered. Lastly, the understudied effects of PAH photo-toxicity on oysters reveals drastic increases to the toxicity of PAHs via photooxidation and the formation of quinones. The consequences of the interaction between local and global environmental stressors thus provide a glimpse into the differential response to anthropogenic impacts across regions of the world.

Chemical source profiles of particulate matter and gases emitted from solid fuels for residential cooking and heating scenarios in Qinghai-Tibetan Plateau

Incomplete combustion of solid fuels (animal dung and bituminous coal) is a common phenomenon during residential cooking and heating in the Qinghai-Tibetan Plateau (QTP), resulting in large amounts of pollutants emitted into the atmosphere. This study investigated the pollutant emissions from six burning scenarios (heating and cooking with each of the three different fuels: yak dung, sheep dung, and bitumite) in the QTP's pastoral dwellings. Target pollutants such as carbon monoxide (CO), gas-phase polycyclic aromatic hydrocarbons (PAHs), volatile organic compounds (VOCs), fine particles (PM_2.5, particulate matter with an aerodynamic diameter < 2.5 μm), carbonaceous aerosols, water-soluble ions, and particle-phase PAHs were investigated. Emission factors (EFs) (mean ± standard deviation) of PM_2.5 from the six scenarios were in the range of 1.21 ± 0.47-7.03 ± 1.95 g kg^-1, of which over 60% mass fractions were carbonaceous aerosols. The ratio of organic carbon to elemental carbon ranged from 9.6 ± 2.7-33.4 ± 11.5 and 81.7 ± 30.4-91.9 ± 29.0 for dung and bitumite burning, respectively. These values were much larger than those reported in the literature, likely because of the region's high altitudes-where the oxygen level is approximately 65% of that at the sea level-thus providing a deficient air supply to stoves. However, the toxicity and carcinogenicity of PAHs emitted from solid fuel combustion in the QTP are significant, despite a slightly lower benzo(a)pyrene-equivalent carcinogenic potency (Bap_eq) in this study than in the literature. The gas-to-particle partitioning coefficient of PAHs and VOC emission profiles in the QTP differed significantly from those reported for other regions in the literature. More attention should be paid to the emissions of PAH derivatives (oxygenated PAHs and nitro-PAHs), considering their enhanced light-absorbing ability and high BaP_eq from solid fuel combustion in the QTP.

A sensitive GC-HRMS method for the simultaneous determination of parent and oxygenated polycyclic aromatic hydrocarbons in barbecued meat and meat substitutes

A sensitive GC-HRMS method was developed to analyze six polycyclic aromatic hydrocarbons (PAH; anthracene, benzo[a]anthracene, benzo[a]pyrene, benzo[b]fluoranthene, chrysene, and fluorene) and eight oxygenated PAHs (OPAH; anthracene-9,10-dione, benzo[a]anthracene-7,12-dione, 7H-benz[de]anthracene-7-one, 11H-benzo[b]fluorene-11-one, 6H-benzo[cd]pyren-6-one, 9,10-dihydro-8H-benzo[a]pyren-7-one, fluoren-9-one, and naphthacene-5,12-dione) in barbecued meat and meat substitutes. After optimization of the conditions of the sample preparation, consisting of accelerated solvent extraction (ASE) and solid-phase extraction (SPE), high recoveries (PAH 72-109%; OPAH 74-106%) were obtained. The linear regression of the matrix calibration resulted in high correlation coefficients (0.959-0.999). For the first time, reasonably low limits of detection (PAH 0.03-0.17 µg/kg; OPAH 0.04-0.43 µg/kg) were achieved, allowing the analysis of samples barbecued under practical relevant conditions. In charcoal grilled samples, the sum content of the seven detected OPAHs (5.7-62.4 µg/kg) was higher than the sum content of the six PAHs (1.4-36.7 µg/kg). However, 9,10-dihydro-8H-benzo[a]pyren-7-one was not detected in these samples.

Past, present, and future perspectives on the assessment of bioavailability/bioaccessibility of polycyclic aromatic hydrocarbons: A 20-year systemic review based on scientific econometrics

Bioaccessibility/bioavailability (bioac-bioav) is an important criterion in the risk assessment of polycyclic aromatic hydrocarbons (PAHs), especially in the restoration of contaminated sites. Although, the bioac-bioav concept is widely employed in PAH risk assessment for both humans and wildlife, their growth and integration in risk assessment models are seldom discussed. Consequently, the relevant literature listed on Web of Science (WOS)™ was retrieved and analyzed using the bibliometric software Citespace in order to gain a comprehensive understanding of this issue. Due to the limitations of the literature search software, we manually searched the articles about PAHs bioac-bioav that were published before 2000. This stage focuses on research on the distribution coefficient of PAHs between different environmental phases and laid the foundation for the adsorption-desorption of PAHs in subsequent studies of the bioac-bioav of PAHs. The research progress on PAH bioac-bioav from 2000 to the present was evaluated using the Citespace software based on country- and discipline-wise publication volumes and research hotspots. The development stages of PAH bioac-bioav after 2000 were divided into four time segments. The first three segments (2000-2005, 2006-2010, and 2011-2015) focused on the degradation of PAHs and their in vivo (bioavailability)-in vitro (bioaccessibility) evaluation method and risk assessment. Meanwhile, the current (2016-present) research focuses on the establishment of analytical methods for assessing PAH derivatives at environmental concentrations and the optimization of various in vitro digestion methods, including chemical optimization (sorptive sink) and biological optimization (Caco-2 cell). The contents are aimed at supplying researchers with a deeper understanding of the development of PAH bioac-bioav.

Clinical Relevance of Urine Flow Rate and Exposure to Polycyclic Aromatic Hydrocarbons

Background: Polycyclic aromatic hydrocarbon (PAH) metabolites have received increasing attention because several of these organic substances are highly carcinogenic or mutagenic. Exposure to PAHs is associated with many harmful health effects; however, we are not aware of any study that has explored the exposure to PAHs and urinary conditions in the general population. The present work aimed to investigate the correlation among PAH and urine flow rate (UFR). Method: Cross-sectional data from the National Health and Nutrition Examination Survey (NHANES) 2009–2012 were used in our study. A total of 4172 participants and a total of nine PAH metabolites were examined. The UFR was measured as the amount of urine excreted in a period of time (mL/h). Several covariates were adjusted in linear regression models. Result: After adjusting for variables, the PAH metabolites in urine showed a significant correlation with UFR. Dose-dependent associations between PAH metabolites in the urine and UFR were also found. Higher quartiles of PAH metabolites in urine exhibited higher regression coefficients. Conclusion: Our study highlighted that PAH metabolites in urine had a strong association with decreased UFR in the US adult population. These findings support the possibility that PAH exposure is related to bladder dysfunction. Further prospective studies are warranted.

Zebrafish (Danio rerio) using as model for genotoxicity and DNA repair assessments: Historical review, current status and trends

Genotoxic pollutants lead to both DNA damage and changes in cell repair mechanisms. Selecting suitable biomonitors is a fundamental step in genotoxicity studies. Thus, zebrafish have become a popular model used to assess the genotoxicity of different pollutants in recent years. They have orthologous genes with humans and hold almost all genes involved in different repair pathways. Therefore, the aim of the current study is to summarize the existing literature on zebrafish using as model system to assess the genotoxicity of different pollutants. Revised data have shown that comet assay is the main technique adopted in these studies. However, it is necessary standardizing the technique applied to zebrafish in order to enable better result interpretation and comparisons. Overall, pollutants lead to single-strand breaks (SSB), double-strand breaks (DSB), adduct formation, as well as to changes in the expression of genes involved in repair mechanisms. Although analyzing repair mechanisms is essential to better understand the genotoxic effects caused by pollutants, few studies have analyzed repair capacity. The current review reinforces the need of conducting further studies on the role played by repair pathways in zebrafish subjected to DNA damage. Revised data have shown that zebrafish are a suitable model to assess pollutant-induced genotoxicity.

Fate and Fathead Minnow Embryotoxicity of Weathering Crude Oil in a Pilot-Scale Spill Tank

For several years now, the Natural Resources Canada research facility at CanmetENERGY Devon (AB, Canada) has been performing experiments in a pilot-scale spill tank using 1200 L of river water to examine the physical and chemical behaviors of various crude oil/water mixtures under varying water temperature regimes. Because oil toxicity can be modulated by weathering of the petroleum products, the present study aimed to assess changes in fish embryotoxicity to mixed sweet blend crude oil as it weathered at air and water temperatures of 14 °C and 15 °C, respectively, for 28 d. The physicochemical behavior of the oil was also monitored. Water samples were taken from the spill tank 5 times during the 28-d experiment on days 1, 6, 14, 21, and 28 and were used to perform toxicity exposures using fathead minnow embryos (Pimephales promelas). For each water sampling day, newly fertilized embryos were exposed to a serial dilution of the spill tank water, noncontaminated river water (used in the spill tank), and a reconstituted water laboratory control. Embryos were raised until hatching. Although mortality was not significantly altered by the oil contamination over the time period, malformation occurrence and severity showed concentration-dependent responses to all contaminated water collected. The results suggest that days 14, 21, and 28 were the most toxic time periods for the fish embryos, which corresponded to increasing concentrations of unidentified oxidized organic compounds detected by a quadropole-time-of-flight system. The present study highlights a novel area for oil research, which could help us to better understand the toxicity associated with oil weathering for aquatic species. Environ Toxicol Chem 2021;40:127-138. © 2020 Her Majesty the Queen in Right of Canada. Reproduced with the permission of the Minister of Natural Resources Canada.

Studying the mixture effects of brominated flame retardants and metal ions by comet assay

This study was designed to evaluate the sensitivities of diverse cell lines on DNA damage effects and genotoxic effects of three brominated flame retardants (BFRs) and three metal ions (Cu²⁺, Cd²⁺, Hg²⁺) by comet assay. First, THP-1 was identified as the most sensitive cell line in terms of DNA damage among 11 kinds of cells screened. Accordingly, the THP-1 cell line was used as a model in subsequent single/combined genotoxicity tests. Single exposure tests to BFRs or metal ions revealed that the DNA damage effects increased with increasing exposure concentration. In combined exposure tests, BFRs (at concentrations of 1/2 EC₅₀) were deployed in combination with different concentrations of Cu²⁺, Cd²⁺, or Hg²⁺. The results showed that the % tail DNA values were significantly increased by most mixtures. Our findings on combined toxic effects by comet assay provide valuable information for setting valid environmental safety evaluation standards.

Quantitative biomonitoring of polycyclic aromatic compounds (PACs) using the Sydney rock oyster (Saccostrea glomerata)

Increasing our understanding of the bioavailable fractions of polycyclic aromatic compounds (PACs) in an aquatic environment is important for the assessment of the environmental and human health risks posed by PACs. More importantly, the behaviour of polar polycyclic aromatic hydrocarbons (polar PAHs), which are metabolites of legacy PAHs, are yet to be understood. We, therefore, carried out a study involving Sydney rock oysters (Saccostrea glomerata) sourced from two locations, that had been exposed to PAH contamination, within an Australian south-east estuary. Biomonitoring of these oysters, following relocation from the estuary to a relatively isolated waterway, was done at 24 and 72 h after deployment and subsequently at 7, 14, 28, 52 and 86 days. Control samples from Camden Haven River were sampled for PAC analyses just before deployment, after 28 days and at the end of the study (day 86). Lipid-normalised concentrations in oyster tissues across the 86-day sampling duration, elimination rate constants (k₂), biological half-lives (t_1/2) and time required to reach 95% of steady-state (t₉₅) were reported for parent PAHs and the less-monitored polar PAHs including nitrated/oxygenated/heterocyclic PAHs (NPAHs, oxyPAHs and HPAHs) for the three differently sourced oyster types. Most of the depurating PAHs and NPAHs, as well as 9-FLO (oxyPAH), had k₂ values significantly different from zero (p < 0.05). All other oxyPAHs and HPAHs showed no clear depuration, with their concentrations remaining similar. The non-depuration of polar PAHs from oyster tissues could imply greater human health risk compared to their parent analogues.

Polycyclic aromatic compounds (PACs) in the Canadian environment: Exposure and effects on wildlife

Polycyclic aromatic compounds (PACs) are ubiquitous in the environment. Wildlife (including fish) are chronically exposed to PACs through air, water, sediment, soil, and/or dietary routes. Exposures are highest near industrial or urban sites, such as aluminum smelters and oil sands mines, or near natural sources such as forest fires. This review assesses the exposure and toxicity of PACs to wildlife, with a focus on the Canadian environment. Most published field studies measured PAC concentrations in tissues of invertebrates, fish, and birds, with fewer studies of amphibians and mammals. In general, PAC concentrations measured in Canadian wildlife tissues were under the benzo[a]pyrene (BaP) guideline for human consumption. Health effects of PAC exposure include embryotoxicity, deformities, cardiotoxicity, DNA damage, changes to DNA methylation, oxidative stress, endocrine disruption, and impaired reproduction. Much of the toxicity of PACs can be attributed to their bioavailability, and the extent to which certain PACs are transformed into more toxic metabolites by cytochrome P450 enzymes. As most mechanistic studies are limited to individual polycyclic aromatic hydrocarbons (PAHs), particularly BaP, research on other PACs and PAC-containing complex mixtures is required to understand the environmental significance of PAC exposure and toxicity. Additional work on responses to PACs in amphibians, reptiles, and semi-aquatic mammals, and development of molecular markers for early detection of biological responses to PACs would provide a stronger biological and ecological justification for regulating PAC emissions to protect Canadian wildlife.

Removal of polycyclic aromatic hydrocarbon (PAH)-contaminated sediments by persulfate oxidation and determination of degradation product cytotoxicity based on HepG2 and ZF4 cell lines

This study evaluated the use of magnetite (Fe₃O₄), carbon black (CB), and Fe₃O₄-CB composites activated by persulfate (PS) at circumneutral pH to oxidize polycyclic aromatic hydrocarbons (PAHs) in marine sediments. In addition, the in vitro cytotoxic activity and apoptotic response of the obtained degradation products were investigated. Chemical analyses showed that the total PAH concentration was 26,263 ng/g for sediment samples from an industrial port area. Highly toxic BaP was the main contributor to the TEQ in sediments. Source analyses demonstrated that the PAHs in the sediment were derived from coal combustion. In this study, we found that the PS oxidation processes effectively degrade PAHs at concentration levels of 1.7 × 10^-5 M at pH 6.0. The 3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyltetrazolium bromide (MTT) assay was employed to assess the cytotoxicity of the PAH degradation products before and after Fe₃O₄/PS, CB/PS, and Fe₃O₄-CB/PS oxidation treatment using a human hepatoma carcinoma cell line (HepG2) and a zebrafish (Danio rerio) embryonic cell line (ZF4). Each sample extract showed a marked dose-related response, with the cell viability reduced by 82% in the case of HepG2 and 58% in the case of ZF4 at 100 μg/mL after the Fe₃O₄-CB/PS process. The PAH degradation products had different effects on the cell morphologies of the two cell lines. The results suggested that the ZF4 cell model is more sensitive than HepG2 to the toxicity of the PAH samples.

Mixture effects of oxygenated PAHs and benzo[a]pyrene on cardiovascular development and function in zebrafish embryos

Polycyclic aromatic compounds (PACs), including polycyclic aromatic hydrocarbons (PAHs) and oxygenated PAHs (oxy-PAHs), are common environmental pollutants known to cause health effects in humans and wild-life. In particular, vertebrate cardiovascular development and function are sensitive to PACs. However, the interactive effects of PAHs and oxy-PAHs on cardiovascular endpoints have not been well studied. In this study, we used zebrafish embryos (ZFEs) as a model to examine developmental and cardiovascular toxicities induced by the three environmental oxy-PAHs benzo[a]fluorenone (BFLO), 4H-cyclopenta[def]phenanthren-4-one (4H-CPO) and, 6H-benzo[cd]pyren-6-one (6H-BPO), and the PAH benzo[a]pyrene (BaP) either as single exposures or binary oxy-PAH + PAH mixtures. 6H-BPO induced developmental and cardiovascular toxicity, including reduced heartbeat rate and blood flow, at lower doses compared to the other compounds. Exposure to binary mixtures generally caused enhanced toxicity and induction of aryl hydrocarbon receptor (AhR)-regulated gene expression (ahr2 and cyp1a) compared to single compound exposure. This was associated with differential expression of genes involved in cardiovascular development and function including atp2a2, myh6, tbx5 and zerg. AhR-knock-down significantly reduced the cardiovascular toxicity of 6H-BPO and its binary mixture with BaP indicating a significant AhR-dependence of the effects. Measurements of internal concentrations showed that the toxicokinetics of BaP and 6H-BPO were altered in the binary mixture compared to the single compound exposure, and most likely due to CYP1 inhibition by 6H-BPO. Altogether, these data support that similar to interactions between PAHs, mixtures of PAHs and oxy-PAHs may cause increased developmental and cardiovascular toxicity in ZFEs through an AhR-dependent mechanism.

Transcriptome changes of Takifugu obscurus liver after acute exposure to the oxygenated-PAH 9,10-phenanthrenequione

Contamination with polycyclic aromatic hydrocarbons (PAHs) causes noticeable ecological problems in aquatic ecosystems. 9,10-Phenanthrenequione (9,10-PQ) is an oxidized PAH and is highly toxic to aquatic animals. However, the effects of 9,10-PQ on the molecular metabolism of fish remain largely unknown. In this study, Takifugu obscurus juveniles were acutely exposed to 44.30 µg/L 9,10-PQ for 3 days. The transcriptome profile changes in their livers were compared between the 9,10-PQ treatment group and the control using T. rubripes as the reference genome. The results identified 22,414 genes in our transcriptome. Among them, 767 genes were differentially expressed after exposure to 9,10-PQ, which enriched 16 KEGG pathways. Among them, the glycolysis, phagosome, and FOXO signaling pathways were significantly activated in 9,10-PQ treatment compared with the control. These data indicate that 9,10-PQ increased the glycolysis capacity to produce more energy for resistance and harmed immune function. Moreover, several genes related to tumorigenesis were significantly upregulated in response to 9,10-PQ, displaying the carcinogenic toxicity of 9,10-PQ to T. obscurus. Genes in steroid biosynthesis pathways were downregulated in the 9,10-PQ treatment group, suggesting interference with the endocrine system. Overall, these findings provide information to help evaluate the environmental risks that oxygenated-PAHs present to T. obscurus.

Similar polycyclic aromatic hydrocarbon and genotoxicity profiles of atmospheric particulate matter from cities on three different continents

The extractable organic material (EOM) from atmospheric total suspended particles (TSP) contains several organic compounds including non-substituted polycyclic aromatic hydrocarbons (PAHs), alkyl-PAHs, and nitro-PAHs. These chemicals seem to be among the key drivers of TSP genotoxicity. We have shown previously that the mutagenic potencies of the EOM from Limeira, Stockholm, and Kyoto, cities with markedly different meteorological conditions and pollution sources are similar. Here we compare the profiles of non-substituted PAHs (27 congeners), alkyl-PAHs (15 congeners), and nitro-PAHs (7 congeners) from the same EOM samples from these cities. We also compared the genotoxicity profiles using comet and micronucleus assays in human bronchial epithelial cells. The profiles of PAHs, as well as the cytotoxic and genotoxic potencies when expressed in EOM, were quite similar among the studied cities. It seems that despite the differences in meteorological conditions and pollution sources of the cities, removal, mixing, and different atmospheric transformation processes may be contributing to the similarity of the PAHs composition and genotoxicity profiles. More studies are required to verify if this would be a general rule applicable to other cities. Although these profiles were similar for all three cities, the EOM concentration in the atmospheres is markedly different. Thus, the population of Limeira (∼10-fold more EOM/m³ than Stockholm and ∼6-fold more than Kyoto) is exposed to higher concentrations of genotoxic pollutants, and Kyoto's population is 1.5-fold more exposed than Stockholm's. Therefore, to reduce the risk of human exposure to TSP genotoxins, the volume of emissions needs to be reduced.

Speciation and source apportionment of polycyclic aromatic compounds (PACs) in sediments of the largest salt water lake of Australia

Great ecological and human health risks may arise from the presence of polycyclic aromatic hydrocarbons (PAHs) in aquatic environments and particularly in sediments, where they often partition. In spite of the apparent risk, knowledge about PAHs and their polar derivatives in sediments is limited. We, therefore, carried out an assessment of the concentrations of parent PAHs and their derivatives (polar PAHs) in sediments of Lake Macquarie: the largest saltwater lake in the southern hemisphere. A total of 31 sediment samples along the pollution prone western shoreline of the estuary were analysed. Multiple source apportionment methods were used to investigate PAH sources contributing to parent and polar PAH concentrations in the estuarine sediments. Concentration levels were highest for high molecular weight (HMW) PAHs compared to low molecular weight (LMW) PAHs. The highest PAH concentrations were recorded for oxygenated PAHs (oxy-PAHs) compared to parent and other polar PAHs. Polycyclic aromatic hydrocarbon diagnostic ratios and compositional analysis showed that PAHs in Lake Macquarie were predominantly pyrogenic exhibiting strong positive correlation (R² = 0.972) with total PAH concentrations. Principal Component Analysis (PCA) identified three groupings of PAHs with oxy-PAHs and NPAHs dominating (40.2%). Carbazole, a heterocyclic PAH, was also a prominent contributor to sediment PAH concentrations. Atmospheric deposition, coal combustion and vehicular emissions were implicated as the major contributors to sediment pollution.

Polycyclic aromatic compounds in urban soils of Stockholm City: Occurrence, sources and human health risk assessment

Polycyclic aromatic compounds (PACs) are ubiquitous pollutants that are found everywhere in our environment, including air, soil and water. The aim of this study was to determine concentrations, distribution, sources and potential health risk of 43 PACs in soils collected from 25 urban parks in Stockholm City, Sweden. These PACs included 21 PAHs, 11 oxygenated PAHs, 7 methylated PAHs, and 4 azaarenes whose concentrations ranged between 190 and 54 500, 30.5-5 300, 14.9-680, and 4.17-590 ng/g soil, respectively. Fluoranthene was found at the highest levels ranging between 17.7 and 9800 ng/g, benzo[a]pyrene between 9.64 and 4600 ng/g, and the highly potent carcinogen dibenzo[a,l]pyrene up to 740 ng/g. The most abundant oxy-PAH was 6H-benzo[cd]pyren-6-one (2.09-2300 ng/g). Primary sources of PAHs were identified by use of diagnostic ratios and Positive Matrix Factorization modelling and found to be pyrogenic including vehicle emissions and combustion of biomass. Estimating the incremental lifetime cancer risks (ILCRS) associated with exposure to PAHs in these soils indicated that the PAH levels in some parks constitute a considerable increased risk level for adults and children (total ILCR > 1 × 10^-4). Compared to worldwide urban parks contamination, we conclude that the PAC soil levels in parks of Stockholm City in general are low, but that some parks are more heavily contaminated and should be considered for clean-up actions to limit human health risks.

Transformation and degradation of polycyclic aromatic hydrocarbons (PAHs) in urban road surfaces: Influential factors, implications and recommendations

Polycyclic aromatic hydrocarbons (PAHs) are prone to post-emission transformation and degradation to yield transformed PAH products (TPPs) that are potentially more hazardous than parent PAHs. This review provides a comprehensive evaluation of the potential environmental processes of PAHs such as sorption, volatilisation, photo- and bio-transformation and degradation on road surfaces, a significant accumulation point of PAHs. The review primarily evaluates key influential factors, toxicity implications, PAHs and TPPs fate and viable options for mitigating environmental and human health impacts. Photolysis was identified as the most significant transformation and degradation process due to the light absorption capacity of most PAHs. Climate conditions, physicochemical properties of road dust (sorbent), PAHs and TPPs and the existence of heavy metals such as Fe (III) are notable underlying factors for photolysis. Available data points to the predominance of carbonyl TPPs than other products such as nitro and hydroxyl TPPs with decreasing concentration trend of 9-fluorenone > 9,10-anthraquinone > benzo[a]fluorenone on road surfaces. The review recommends conducting future investigations targeting the influential factors pertaining to the fate of road deposited PAHs and TPPs. Furthermore, development of cost and time effective modern analytical methods is needed to quantify PAHs and TPPs present in minute quantities of samples. The review also identified that the unavailability of toxicity equivalency factors (TEF) for the most critical TPPs can be addressed using quantitative structure-activity relationship (QSAR) models and bioassays simultaneously. The content of this review is significant to the future work of researchers across various fields including analytical and environmental chemistry, stormwater pollution and toxicology.

Analysis of polycyclic aromatic hydrocarbons (PAHs) and their polar derivatives in soils of an industrial heritage city of Australia

Knowledge about polar derivatives of polycyclic aromatic hydrocarbons (PAHs) in soils is limited despite the extensive study of the environmental presence and persistence of non-polar parent PAHs. Polar PAHs have greater potential to be more toxic at low environmental concentrations compared to their homocyclic analogues. For both polar and non-polar PAHs, combustion of fossil fuels is often the main source especially in industrialised environments. This study investigated the concentration profiles of PAHs and its associated polar PAHs such as nitrated PAHs (NPAHs), oxygenated PAHs (oxy-PAHs) and nitrogen, sulphur and oxygen heterocyclic PAHs (N/S/O-heterocyclic PAHs) in a well-known industrial heritage city of Australia. The most abundant polar PAHs were 9-fluorenone (oxy-PAHs), 2-nitrofluorene (NPAHs) and carbazole (heterocyclic-PAHs). A positive correlation (r = 0.5, p < 0.01) between ∑13PAHs and ∑19 polar PAHs was observed, implying a possible spatial association between parent and polar PAHs. The concentrations of polar PAHs in soil samples, across various landuse patterns, were used to calculate the excess lifetime cancer risk (ELCR) from incidental ingestion of soils. The computed ELCR values ranged from 8.2*10^-7 (industrial soils) to 2.3*10^-6 (residential soils), indicating negligible cancer risks. This is the first known study on the occurrence and concentrations of polar and non-polar PAHs in any Australian city, and the results may serve a baseline purpose for improved risk assessment of contaminated sites.

Genotoxicity and DNA damage signaling in response to complex mixtures of PAHs in biomass burning particulate matter from cashew nut roasting

Approximately 3 billion people world-wide are exposed to air pollution from biomass burning. Herein, particulate matter (PM) emitted from artisanal cashew nut roasting, an important economic activity worldwide, was investigated. This study focused on: i) chemical characterization of polycyclic aromatic hydrocarbons (PAHs) and oxygenated (oxy-) PAHs; ii) intracellular levels of reactive oxygen species (ROS); iii) genotoxic effects and time- and dose-dependent activation of DNA damage signaling, and iv) differential expression of genes involved in xenobiotic metabolism, inflammation, cell cycle arrest and DNA repair, using A549 lung cells. Among the PAHs, chrysene, benzo[a]pyrene (B[a]P), benzo[b]fluoranthene, and benz[a]anthracene showed the highest concentrations (7.8-10 ng/m³), while benzanthrone and 9,10-anthraquinone were the most abundant oxy-PAHs. Testing of PM extracts was based on B[a]P equivalent doses (B[a]P_eq). IC₅₀ values for viability were 5.7 and 3.0 nM B[a]P_eq at 24 h and 48 h, respectively. At these low doses, we observed a time- and dose-dependent increase in intracellular levels of ROS, genotoxicity (DNA strand breaks) and DNA damage signaling (phosphorylation of the protein checkpoint kinase 1 - Chk1). In comparison, effects of B[a]P alone was observed at micromolar range. To our knowledge, no previous study has demonstrated an activation of pChk1, a biomarker used to estimate the carcinogenic potency of PAHs in vitro, in lung cells exposed to cashew nut roasting extracts. Sustained induction of expression of several important stress response mediators of xenobiotic metabolism (CYP1A1, CYP1B1), ROS and pro-inflammatory response (IL-8, TNF-α, IL-2, COX2), and DNA damage response (CDKN1A and DDB2) was also identified. In conclusion, our data show high potency of cashew nut roasting PM to induce cellular stress including genotoxicity, and more potently when compared to B[a]P alone. Our study provides new data that will help elucidate the toxic effects of low-levels of PAH mixtures from air PM generated by cashew nut roasting.