Oxy-PAHs: occurrence in the environment and potential genotoxic/mutagenic risk assessment for human health

Source apportionment of particle-bound polycyclic aromatic hydrocarbons (PAHs), oxygenated PAHs (OPAHs), and their associated long-term health risks in a major European city

Many studies have drawn attention to the associations of oxygenated polycyclic aromatic hydrocarbons (OPAHs) with harmful health effects, advocating for their systematic monitoring alongside simple PAHs to better understand the aerosol carcinogenic potential in urban areas. To address this need, this study conducted an extensive PM2.5 sampling campaign in Athens, Greece, at the Thissio Supersite of the National Observatory of Athens, from December 2018 to July 2021, aiming to characterize the levels and variability of polycyclic aromatic compounds (PACs), perform source apportionment, and assess health risk. Cumulative OPAH concentrations (Σ-OPAHs) were in the same range as Σ-PAHs (annual average 4.2 and 5.6 ng m-3, respectively). They exhibited a common seasonal profile with enhanced levels during the heating seasons, primarily attributed to residential wood burning (RWB). The episodic impact of biomass burning was also observed during a peri-urban wildfire event in May 2021, when PAH and OPAH concentrations increased by a factor of three compared to the monthly average. The study period also included the winter 2020-2021 COVID-19 lockdown, during which PAH and OPAH levels decreased by >50 % compared to past winters. Positive matrix factorization (PMF) source apportionment, based on a carbonaceous aerosol speciation dataset, identified PAC sources related to RWB, local traffic (gasoline vehicles) and urban traffic (including diesel emissions), as well as an impact of regional organic aerosol. Despite its seasonal character, RWB accounted for nearly half of Σ-PAH and over two-thirds of Σ-OPAH concentrations. Using the estimated source profiles and contributions, the source-specific carcinogenic potency of the studied PACs was calculated, revealing that almost 50 % was related to RWB. These findings underscore the urgent need to regulate domestic biomass burning at a European level, which can provide concrete benefits for improving urban air quality, towards the new stricter EU standards, and reducing long-term health effects.

Association between Personal Abiotic Airborne Exposures and Body Composition Changes among Healthy Adults (60-69 Years Old): A Combined Exposome-Wide and Lipidome Mediation Approach from the China BAPE Study

BACKGROUND

Evidence suggested that abiotic airborne exposures may be associated with changes in body composition. However, more evidence is needed to identify key pollutants linked to adverse health effects and their underlying biomolecular mechanisms, particularly in sensitive older adults.

OBJECTIVES

Our research aimed to systematically assess the relationship between abiotic airborne exposures and changes in body composition among healthy older adults, as well as the potential mediating mechanisms through the serum lipidome.

METHODS

From September 2018 to January 2019, we conducted a monthly survey among 76 healthy adults (60-69 years old) in the China Biomarkers of Air Pollutant Exposure (BAPE) study, measuring their personal exposures to 632 abiotic airborne pollutions using MicroPEM and the Fresh Air wristband, 18 body composition indicators from the InBody 770 device, and lipidomics from venous blood samples. We used an exposome-wide association study (ExWAS) and deletion/substitution/addition (DSA) model to unravel complex associations between exposure to contaminant mixtures and body composition, a Bayesian kernel machine regression (BKMR) model to assess the overall effect of key exposures on body composition, and mediation analysis to identify lipid intermediators.

RESULTS

The ExWAS and DSA model identified that 2,4,5-T methyl ester (2,4,5-TME), 9,10-Anthracenedione (ATQ), 4b,8-dimethyl-2-isopropylphenanthrene, and 4b,5,6,7,8,8a,9,10-octahydro-(DMIP) were associated with increased body fat mass (BFM), fat mass indicators (FMI), percent body fat (PBF), and visceral fat area (VFA) in healthy older adults [Bonferroni-Hochberg false discovery rate ( FD R BH ) < 0.05 ]. The BKMR model demonstrated a positive correlation between contaminants (anthracene, ATQ, copaene, di-epi-α -cedrene, and DMIP) with VFA. Mediation analysis revealed that phosphatidylcholine [PC, PC(16:1e/18:1), PC(16:2e/18:0)] and sphingolipid [SM, SM(d18:2/24:1)] mediated a significant portion, ranging from 12.27% to 26.03% (p-value < 0.05 ), of the observed increase in VFA.

DISCUSSION

Based on the evidence from multiple model results, ATQ and DMIP were statistically significantly associated with the increased VFA levels of healthy older adults, potentially regulated through lipid intermediators. These findings may have important implications for identifying potentially harmful environmental chemicals and developing targeted strategies for the control and prevention of chronic diseases in the future, particularly as the global population is rapidly aging. https://doi.org/10.1289/EHP13865.

Novel insights into the synergetic degradation of pyrene by microbial communities from mangroves in China

Pyrene is a high molecular weight polycyclic aromatic hydrocarbon (HMW-PAHs). It is a ubiquitous, persistent, and carcinogenic environmental contaminant that has raised concern worldwide. This research explored synergistic bacterial communities for efficient pyrene degradation in seven typical Southern China mangroves. The bacterial communities of seven typical mangroves were enriched by pyrene, and enriched bacterial communities showed an excellent pyrene degradation capacity of > 95% (except for HK mangrove and ZJ mangrove). Devosia, Hyphomicrobium, Flavobacterium, Marinobacter, Algoriphahus, and Youhaiella all have significant positive correlations with pyrene (R>0, p < 0.05) by 16SrRNA gene sequencing and metagenomics analysis, indicated that these genera play a vital role in pyrene metabolism. Meanwhile, the functional genes were involved in pyrene degradation that was enriched in the bacterial communities, including the genes of nagAa, ndoR, pcaG, etc. Furthermore, the analyses of functional genes and binning genomes demonstrated that some bacterial communities as a unique teamwork to cooperatively participate in pyrene degradation. Interestingly, the genes related to biogeochemical cycles were enriched, such as narG , soxA, and cyxJ, suggested that bacterial communities were also helpful in maintaining the stability of the ecological environment. In addition, some novel species with pyrene-degradation potential were identified in the pyrene-degrading bacterial communities, which can enrich the resource pool of pyrene-degrading strains. Overall, this study will help develop further research strategies for pollutant removal.

Nitro-PAHs: Occurrences, ecological consequences, and remediation strategies for environmental restoration

Nitrated polycyclic aromatic hydrocarbons (nitro-PAHs) are persistent pollutants that have been introduced into the environment as a result of human activities. They are produced when PAHs undergo oxidation and are highly resistant to degradation, resulting in prolonged exposure and significant health risks for wildlife and humans. Nitro-PAHs' potential to induce cancer and mutations has raised concerns about their harmful effects. Furthermore, their ability to accumulate in the food chain seriously threatens the ecosystem and human health. Moreover, nitro-PAHs can disrupt the normal functioning of the endocrine system, leading to reproductive and developmental problems in humans and other organisms. Reducing nitro-PAHs in the environment through source management, physical removal, and chemical treatment is essential to mitigate the associated environmental and human health risks. Recent studies have focused on improving nitro-PAHs' phytoremediation by incorporating microorganisms and biostimulants. Microbes can break down nitro-PAHs into less harmful substances, while biostimulants can enhance plant growth and metabolic activity. By combining these elements, the effectiveness of phytoremediation for nitro-PAHs can be increased. This study aimed to investigate the impact of introducing microbial and biostimulant agents on the phytoremediation process for nitro-PAHs and identify potential solutions for addressing the environmental risks associated with these pollutants.

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.

Role of inflammatory lipid and fatty acid metabolic abnormalities induced by plastic additives exposure in childhood asthma

Lipid metabolism play an essential role in occurrence and development of asthma, and it can be disturbed by phthalate esters (PAEs) and organophosphate flame retardants (OPFRs). As a chronic inflammatory respiratory disease, the occurrence risk of childhood asthma is increased by PAEs and OPFRs exposure, but it remains not entirely clear how PAEs and OPFRs contribute the onset and progress of the disease. We have profiled the serum levels of PAEs and OPFRs congeners by liquid chromatography coupled with mass spectrometry, and its relationships with the dysregulation of lipid metabolism in asthmatic, bronchitic (acute inflammation) and healthy (non-inflammation) children. Eight PAEs and nine OPFRs congeners were found in the serum of children (1 - 5 years old) from Shenzhen, and their total median levels were 615.16 ng/mL and 17.06 ng/mL, respectively. Moreover, the serum levels of mono-methyl phthalate (MMP), tri-propyl phosphate (TPP) and tri-n-butyl phosphate (TNBP) were significant higher in asthmatic children than in healthy and bronchitic children as control. Thirty-one characteristic lipids and fatty acids of asthma were screened by machine-learning random forest model based on serum lipidome data, and the alterations of inflammatory characteristic lipids and fatty acids including palmitic acids, 12,13-DiHODE, 14,21-DiHDHA, prostaglandin D2 and LysoPA(18:2) showed significant correlated with high serum levels of MMP, TPP and TNBP. These results imply PAEs and OPFRs promote the occurrence of childhood asthma via disrupting inflammatory lipid and fatty acid metabolism, and provide a novel sight for better understanding the effects of plastic additives on childhood asthma.

Particulate matter from a tropical city in southeast Brazil: Impact of biomass burning on polycyclic aromatic compounds levels, health risks, and in vitro toxicity

In the context of a rising global temperature, biomass burning represents an increasing risk to human health, due to emissions of highly toxic substances such as polycyclic aromatic hydrocarbon (PAHs). Size-segregated particulate matter (PM) was collected in a region within the sugarcane belt of São Paulo state (Brazil), where biomass burning is still frequent, despite the phasing out of manual harvesting preceded by fire. The median of the total concentration of the 15 PAHs determined was 2.3 ± 1.8 ng m-3 (n = 19), where 63% of this content was in PM1.0. Concentrations of OPAHs and NPAHs were about an order of magnitude lower. PM2.5 collected in the dry season, when most of the fires occur, presented PAHs and OPAHs total concentrations three times higher than in the wet season, showing positive correlations with fire foci number and levoglucosan (a biomass burning marker). These results, added to the fact that biomass burning explained 65% of the data variance (PCA analysis), evidenced the importance of this practice as a source of PAHs and OPAHs to the regional atmosphere. Conversely, NPAHs appeared to be mainly derived from diesel-powered vehicles. The B[a]P equivalent concentration was estimated to be 4 times higher in the dry season than in the wet season, and was greatly increased during a local fire event. Cytotoxicity and genotoxicity of PM1.0 organic extracts were assessed using in vitro tests with human liver HepG2 cells. For both types of tests, significant toxicity was only observed for samples collected during the dry season. Persistent DNA damage that may have impaired the DNA repair system was also observed. The results indicated that there was a health risk associated with the air particulate mixture, mainly related to biomass burning, demonstrating the urgent need for better remediation actions to prevent the occurrence of burning events.

Particulate polycyclic aromatic hydrocarbons in rural households burning solid fuels in Xuanwei County, Southwest China: occurrence, size distribution, and health risks

The study is about the size distribution and health risks of polycyclic aromatic hydrocarbons (PAHs) in indoor environment of Xuanwei, Southwest China particle samples were collected by Anderson 8-stage impactor which was used to gather particle samples to nine size ranges. Size-segregated samples were collected in indoor from a rural village in Xuanwei during the non-heating and heating seasons. The results showed that the total concentrations of the indoor particulate matter (PM) were 757 ± 60 and 990 ± 78 μg/m3 in non-heating and heating seasons, respectively. The total concentration of indoor PAHs reached to 8.42 ± 0.53 μg/m3 in the heating season, which was considerably greater than the concentration in the non-heating season (2.85 ± 1.72 μg/m3). The size distribution of PAHs showed that PAHs were mainly enriched in PMs with the diameter <1.1 μm. The diagnostic ratios (DR) and principal component analysis (PCA) showed that coal and wood for residential heating and cooking were the main sources of indoor PAHs. The results of the health risk showed that the total deposition concentration (DC) in the alveolar region (AR) was 0.25 and 0.68 μg/m3 in the non-heating and heating seasons respectively. Throughout the entire sampling periods, the lifetime cancer risk (R) based on DC of children and adults varied between 3.53 ×10-5 to 1.79 ×10-4. During the heating season, the potential cancer risk of PAHs in adults was significant, exceeding 10-4, with a rate of 96%.

Four Years of Active Sampling and Measurement of Atmospheric Polycyclic Aromatic Hydrocarbons and Oxygenated Polycyclic Aromatic Hydrocarbons in Dronning Maud Land, East Antarctica

Antarctica, protected by its strong polar vortex and sheer distance from anthropogenic activity, was always thought of as pristine. However, as more data on the occurrence of persistent organic pollutants on Antarctica emerge, the question arises of how fast the long-range atmospheric transport takes place. Therefore, polycyclic aromatic hydrocarbons (PAHs) and oxygenated (oxy-)PAHs were sampled from the atmosphere and measured during 4 austral summers from 2017 to 2021 at the Princess Elisabeth station in East Antarctica. The location is suited for this research as it is isolated from other stations and activities, and the local pollution of the station itself is limited. A high-volume sampler was used to collect the gas and particle phase (PM10) separately. Fifteen PAHs and 12 oxy-PAHs were quantified, and concentrations ranging between 6.34 and 131 pg m3 (Σ15PAHs-excluding naphthalene) and between 18.8 and 114 pg m3 (Σ13oxy-PAHs) were found. Phenanthrene, pyrene, and fluoranthene were the most abundant PAHs. The gas-particle partitioning coefficient log(Kp) was determined for 6 compounds and was found to lie between 0.5 and -2.5. Positive matrix factorization modeling was applied to the data set to determine the contribution of different sources to the observed concentrations. A 6-factor model proved a good fit to the data set and showed strong variations in the contribution of different air masses. During the sampling campaign, a number of volcanic eruptions occurred in the southern hemisphere from which the emission plume was detected. The FLEXPART dispersion model was used to confirm that the recorded signal is indeed influenced by volcanic eruptions. The data was used to derive a transport time of between 11 and 33 days from release to arrival at the measurement site on Antarctica.

Metabolic regulation of tumor cells exposed to different oxygenated polycyclic aromatic hydrocarbons

Oxygenated polycyclic aromatic hydrocarbons (OPAHs) are a class of polycyclic aromatic derivatives with oxygen-containing functional groups that induce oxidative stress and mutations. However, studies of the carcinogenic and metabolic effects of OPAHs are limited. In this study, we analyzed the carcinogenic effects of four different OPAHs and found that 9-fluorenone (FLO), 9,10-anthraquinone (AQ), and 7,12-benz(a)anthraquinone (BAQ) promoted cell invasion and metastasis via epithelial-mesenchymal transition (EMT) and induced endothelial cell angiogenesis by affecting the expression of vascular endothelial growth factor (VEGF), angiopoietin (ANG), and platelet-derived growth factor (PDGF), whereas 1,8-naphthalic anhydride (NAD) did not show significant carcinogenic effects. In addition, combined with metabolomic analysis, we found that the tumor-promoting effects of different OPAHs were related to their effects on the metabolome, especially the metabolism of glutathione related to oxidative stress. These results provide an experimental basis for studying the carcinogenic and metabolic effects of OPAHs, and an important reference for comprehensively assessing the ecological and health risks of this compounds.

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.

Sediment record of polycyclic aromatic compounds and black carbon over the last ~400 years in Sanjiaolongwan Maar Lake, northeast China

Fuel usage is an important catalyst for socio-economic development and human well-being. Human activities have resulted in significant increases in emissions from biomass burning (BB) and fossil fuel (FF) combustion which have significantly adversely affected human, ecosystem, and planetary health in this era of the Anthropocene. Sanjiaolongwan Maar Lake (SJLW), as a typical crater lake, uniquely receives atmospheric deposition from long-distance transport, and thus, its sediments reflect environmental change and human impacts on a broad scale. In this study, the concentrations and compositions of combustion products, including polycyclic aromatic compounds (PACs, i.e., polycyclic aromatic hydrocarbons (PAHs) and their oxygenated (OPAHs) and nitrogen heterocyclic derivatives (AZAs)) and black carbon (BC and its constituents char and soot), in SJLW over the past 400 years were investigated. The results showed that the PACs and soot concentrations and fluxes in SJLW have rapidly increased since 1950. The concentrations of the total PACs increased ~4 times after the 1950s. Such a fast increase is consistent with the rapid industrialization after the establishment of the People's Republic of China (PRC), which has further accelerated beginning with the implementation of the reform and opening up policy of the PRC in 1978. Moreover, the variations in the compositions of PACs, as well as the decrease in the char/soot ratio, demonstrate a transition in energy usage from BB to FF combustion. The decrease in the benzo[e]pyrene/benzo[a]pyrene ratio indicated an increase in local emissions (because of increasing industrialization in northeast China). The temporal profile of perylene concentrations, fluxes, and perylene/5-ring PAHs ratios strongly suggest that perylene mainly originated from non-pyrogenic sources. The records of PACs and BC in SJLW offer valuable perspectives on human impacts and provide important references for the start of the Anthropocene.

Combined Surface-Enhanced Raman and Infrared Absorption Spectroscopies for Streamlined Chemical Detection of Polycyclic Aromatic Hydrocarbon-Derived Compounds

Polycyclic aromatic hydrocarbons (PAHs) constitute a class of universally prevalent carcinogenic environmental contaminants. It is increasingly recognized, however, that PAHs derivatized with oxygen, sulfur, or nitrogen functional groups are frequently more dangerous than their unfunctionalized counterparts. This much larger family of chemicals─polycyclic aromatic compounds─PACs─is far less well characterized than PAHs. Using surface-enhanced Raman and IR Absorption spectroscopies (SERS + SEIRA) combined on a single substrate, along with density functional theoretical (DFT) calculations, we show that direct chemical detection and identification of PACs at sub-parts-per-billion concentration can be achieved. Focusing our studies on 9,10-anthraquinone, 5,12-tetracenequinone, 9-nitroanthracene, and 1-nitropyrene as model PAC contaminants, detection is made possible by incorporating a hydroxy-functionalized self-assembled monolayer that facilitates hydrogen bonding between analytes and the SERS + SEIRA substrate. 5,12-Tetracenequinone was detected at 0.3 ppb, and the limit of detection was determined to be 0.1 ppb using SEIRA alone. This approach is straightforwardly extendable to other families of analytes and will ultimately facilitate fieldable chemical detection of these dangerous yet largely overlooked environmental contaminants.

Disease burden and health risk to rural communities of northeastern India from indoor cooking-related exposure to parent, oxygenated and alkylated PAHs

Exposure to a total of 51 targeted and non-targeted polycyclic aromatic hydrocarbons (PAHs) and their oxygenated and alkylated derivatives associated with size-segregated aerosol was investigated in rural kitchens using liquefied petroleum gas (LPG), mixed biomass (MB) and firewood (FW) fuels in northeastern India. The averaged PM10-associated parent-, alkylated-, and oxygenated-PAHs concentrations increased notably from LPG (257, 54, and 116 ng m-3) to MB (838, 119, and 272 ng m-3) to FW-using kitchens (2762, 225, and 554 ng m-3), respectively. PAHs were preferentially associated with the PM1 fraction with contributions increasing from 80 % in LPG to 86 % in MB and 90 % in FW-using kitchens, which in turn was dominated by <0.25 μm particles (54-75 % of the total). A clear profile of enrichment of low-molecular weight PAHs in cleaner fuels (LPG) and a contrasting enrichment of high-molecular weight PAHs in biomass-based fuels was noted. The averaged internal dose of Benzo[a]pyrene equivalent was the lowest in the case of LPG (19 ng m-3), followed by MB (161 ng m-3) and the highest in FW users (782 ng m-3). Estimation of incremental lifetime cancer risk (ILCR) from PAH exposure revealed extremely high cancer risk in biomass users (factors of 8-40) compared to LPG. The potential years of life lost (PYLL) and PYLL rate averaged across kitchen categories was higher for lung cancer (PYLL: 10.55 ± 1.04 years; PYLL rate: 204 ± 426) compared to upper respiratory tract cancer (PYLL: 10.02 ± 0.05 years; PYLL rate: 4 ± 7), and the PYLL rates for biomass users were higher by factors of 9-56 as compared to LPG users. These findings stress the need for accelerated governmental intervention to ensure a quick transition from traditional biomass-based fuels to cleaner alternatives for the rural population of northeastern India.

An Integrated Workflow Assisted by In Silico Predictions To Expand the List of Priority Polycyclic Aromatic Compounds

The limited information in existing mass spectral libraries hinders an accurate understanding of the composition, behavior, and toxicity of organic pollutants. In this study, a total of 350 polycyclic aromatic compounds (PACs) in 9 categories were successfully identified in fine particulate matter by gas chromatography high resolution mass spectrometry. Using mass spectra and retention indexes predicted by in silico tools as complementary information, the scope of chemical identification was efficiently expanded by 27%. In addition, quantitative structure-activity relationship models provided toxicity data for over 70% of PACs, facilitating a comprehensive health risk assessment. On the basis of extensive identification, the cumulative noncarcinogenic risk of PACs warranted attention. Meanwhile, the carcinogenic risk of 53 individual analogues was noteworthy. These findings suggest that there is a pressing need for an updated list of priority PACs for routine monitoring and toxicological research since legacy polycyclic aromatic hydrocarbons (PAHs) contributed modestly to the overall abundance (18%) and carcinogenic risk (8%). A toxicological priority index approach was applied for relative chemical ranking considering the environmental occurrence, fate, toxicity, and analytical availability. A list of 39 priority analogues was compiled, which predominantly consisted of high-molecular-weight PAHs and alkyl derivatives. These priority PACs further enhanced source interpretation, and the highest carcinogenic risk was attributed to coal combustion.

Effect of polycyclic aromatic hydrocarbons on cancer risk causally mediated via vitamin D levels

Polycyclic aromatic hydrocarbons (PAHs) widely exist in environmental substrates and are closely related to individual circulating vitamin D levels and tumorigenesis. Therefore, we proposed to evaluate the relationship between PAH exposure, vitamin D, and the risks for 14 cancer types via a causal inference framework underlying the mediation analysis. We evaluated seven urine monohydroxylated PAH (OH-PAH) and serum vitamin D concentrations of 3306 participants from the National Health and Nutrition Examination Survey between the 2013 and 2016 survey cycles and measured PAH concentrations in 150 subjects from the Nanjing cohort. We observed a significant negative dose-response relationship between increased OH-PAH levels and vitamin D deficiency. Each unit increase in ∑OH-PAHs could lead to a decrease in vitamin D levels (βadj  = -0.98, Padj  = 2.05 × 10-4 ). Body mass index could have interaction effects with ∑OH-PAHs and affect vitamin D levels. Coexposure to naphthalene and fluorene metabolites mutually affected vitamin D levels. Notably, vitamin D could causally mediate the relationship between OH-PAHs and nine types of cancer (e.g., colorectal cancer, liver cancers, etc.). This study first emphasizes the causal cascade of individual OH-PAHs, vitamin D, and cancer risk, providing insights into prevention via the environment.

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.

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.

Multi-Omic Profiling of a Newly Isolated Oxy-PAH Degrading Specialist from PAH-Contaminated Soil Reveals Bacterial Mechanisms to Mitigate the Risk Posed by Polar Transformation Products

Polar biotransformation products have been identified as causative agents for the eventual increase in genotoxicity observed after the bioremediation of PAH-contaminated soils. Their further biodegradation has been described under certain biostimulation conditions; however, the underlying microorganisms and mechanisms remain to be elucidated. 9,10-Anthraquinone (ANTQ), a transformation product from anthracene (ANT), is the most commonly detected oxygenated PAH (oxy-PAH) in contaminated soils. Sand-in-liquid microcosms inoculated with creosote-contaminated soil revealed the existence of a specialized ANTQ degrading community, and Sphingobium sp. AntQ-1 was isolated for its ability to grow on this oxy-PAH. Combining the metabolomic, genomic, and transcriptomic analyses of strain AntQ-1, we comprehensively reconstructed the ANTQ biodegradation pathway. Novel mechanisms for polyaromatic compound degradation were revealed, involving the cleavage of the central ring catalyzed by Baeyer-Villiger monooxygenases (BVMO). Abundance of strain AntQ-1 16S rRNA and its BVMO genes in the sand-in-liquid microcosms correlated with maximum ANTQ biodegradation rates, supporting the environmental relevance of this mechanism. Our results demonstrate the existence of highly specialized microbial communities in contaminated soils responsible for processing oxy-PAHs accumulated by primary degraders. Also, they underscore the key role that BVMO may play as a detoxification mechanism to mitigate the risk posed by oxy-PAH formation during bioremediation of PAH-contaminated soils.

Associations between repeated measurements of urinary polycyclic aromatic hydrocarbon metabolites and thyroid hormones among reproductive-aged men

BACKGROUND

Polycyclic aromatic hydrocarbons (PAHs) have been shown to disrupt thyroid function in toxicological studies, but epidemiological evidence is inconsistent. Furthermore, little is known on potential effects of mixtures of PAHs.

OBJECTIVE

This study aimed to examine the associations of exposure to PAHs as individual chemicals and mixtures with thyroid hormones.

METHODS

We included 378 men from a Reproductive Medicine Center in Wuhan, China. Ten monohydroxylated PAH (OH-PAH) metabolites in repeated urine specimens collected at two-time points and three thyroid hormones [thyroid-stimulating hormone (TSH), free thyroxine (FT4), and free triiodothyronine (FT3)] in one serum sample were measured. Multivariable linear regression models were applied to assess the associations between individual OH-PAH metabolites and thyroid hormones, and the associations with mixtures of OH-PAH metabolites were assessed by Bayesian kernel machine regression (BKMR) models.

RESULTS

Multivariable linear regression models showed inverse associations between urinary 1-OHNa and TSH, between urinary 1-OHPh and 9-OHPh and FT3, as well as between urinary 2-OHPh, 3-OHPh, 9-OHPh and ∑OHPh and FT4, regardless of these individual OH-PAH metabolites modeled as continuous or tertile variables (e.g., -21.57 % in TSH; 95 % CI: -35.33 %, -4.88 % for the third vs first tertiles of 1-OHNa; p for trend = 0.014). BKMR models showed negative overall effects of all urinary OH-PAH metabolite mixtures on TSH, FT3, and FT4, and 1-OHNa, 9-OHPh, and 2-OHPh as the most important contributors, respectively, with linear inverse exposure-response associations when holding other OH-PAH metabolites at their median concentrations.

CONCLUSION

Urinary OH-PAH metabolites as individual chemicals and mixtures were adversely associated with thyroid hormones among reproductive-aged men.

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.

Particle size-resolved emission characteristics of complex polycyclic aromatic hydrocarbon (PAH) mixtures from various combustion sources

Combustion of domestic solid fuels is a significant source of polycyclic aromatic hydrocarbons (PAHs). Some oxygenated PAHs (o-PAHs) and PAHs with molecular weight of 302 (MW302 PAHs) are more toxic than the traditional 16 priority PAHs, whereas their emissions were much less elucidated. This study characterized the size-dependent emissions of parent PAHs (p-PAHs), o-PAHs, and MW302 PAHs from various combustion sources. The estimated emission factors (eEFs) from biomass burning sources were highest for most of the PAHs (391-8928 μg/kg), much higher than that of anthracite coal combustion (43.0-145 μg/kg), both which were operated in an indoor stove. Cigarette smoking had a high eEF of o-PAHs (240 ng/g). MW302 PAHs were not found in the emissions of smoking, cooking, and vehicular exhausts. Particle-size distributions of PAHs were compound- and source-dependent, and the tendency to associate with smaller particles was observed especially in biomass burning and cigarette smoking sources. Furthermore, the inter-source differences in PAH eEFs were associated with their dominance in fine particles. PAH composition profiles also varied with the particle size, showing increasing contributions of large-molecule PAHs with decreasing sizes in most cases. The size distributions of p-PAHs are much more significantly dependent on their n-octanol/air partition coefficients and vapor pressures than those of o-PAHs, suggesting differences in mechanisms governing their distributions. Several molecular diagnostic ratios (MDRs), including two based on MW302 PAHs, specific to these combustion scenarios were identified. However, the MDRs within some sources are also strongly size-dependent, providing a new explanation for the uncertainty in their application for source identification of PAHs. This work also highlights the necessity for understanding the size-resolved atmospheric behaviors and fate of PAHs after their emission.

Genotoxicity assessment of textile waste contaminated soil and characterization of textile dye degradation by a novel indigenous bacterium Ochrobactrum intermedium BS39

The harmful effects of textile wastewater irrigation practices on the crop productivity and soil nutrient levels are primarily related with the accumulation of recalcitrant azo dyes in the soil. Therefore, toxicity assessment of the textile waste contaminated soil along with the development of a powerful soil bioremediation strategy is a challenging task for the researchers. Present study aimed to evaluate potential toxicity of the textile wastewater irrigated soil collected from Panki industrial site 5, Kanpur, India employing Ames Salmonella/mammalian microsome test, Escherichia coli DNA repair defective mutation assay and Allium cepa chromosomal aberration assay. The results of the Ames test and DNA repair defective mutation test showed that all the organic extracts of the contaminated soil samples induced different degrees of DNA damage, indicating the existence of mutagenicity and genotoxicity. Additionally, in A. cepa root cells, the contaminated soil altered mitotic index and caused chromosomal abnormalities. Results of the study demonstrated potential health risks related with the irrigation of textile wastewater. Keeping in view of the above scenario, the study led to the isolation and characterization of a novel indigenous bacterium capable of tolerating very high concentration of reactive black 5 dye (500 μg-mL^-1) and salt (20 gL^-1) with concurrently high efficiency of the dye degradation i.e., 93% decolorization at temperature of 37 °C and in pH range of 5-9. Based on the 16S rRNA gene sequencing, the bacterium was identified as Ochrobactrum intermedium. Further, dye degradation products were identified as sodium-2-hydrosulfonylethyl sulphate and sodium-3-aminonaphthalene-2-sulfonate by Gas Chromatography-Mass spectrometry; and this isolate can be exploited for bioremediation of textile waste contaminated soils.

Barbecue conditions affect contents of oxygenated and non-oxygenated polycyclic aromatic hydrocarbons in meat and non-meat patties

The contents of eight oxygenated polycyclic aromatic hydrocarbons (OPAHs; anthracene-9,10-dione, benzo[a]anthracene-7,12-dione, 11H-benzo[b]fluorene-11-one, 6H-benzo[cd]pyren-6-one, 7H-benzo[de]anthracene-7-one, 9,10-dihydro-8H-benzo[a]pyren-7-one, fluoren-9-one, and naphthacene-5,12-dione) and six PAHs (anthracene, fluorene, and PAH4) were investigated in barbecued meat and non-meat patties. The patties were prepared with ten setups (six replicates, each) of barbecue conditions defined by grill type, grate height, heating medium, and barbecue time. The highest median contents were observed with a disposable grill (OPAHs: 46.3 µg/kg; PAHs: 40.7 µg/kg) and a charcoal grill (OPAHs: 29.6 µg/kg; PAHs: 23.3 µg/kg). Fluoren-9-one and anthracene-9,10-dione were the dominant compounds within OPAHs, but also the four toxicologically most relevant OPAHs were detected with a total up to 11.8 µg/kg. Pairs of OPAHs and corresponding PAHs did not show strong correlations, as individual OPAHs and PAHs were affected differently by the barbecue conditions. No suitable markers for OPAH prediction could be found. We recommend to include OPAHs in future PAH investigations.

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.

Prenatal exposure to polycyclic aromatic hydrocarbons could increase the risk of low birth weight by affecting the DNA methylation states in a Chinese cohort

Polycyclic aromatic hydrocarbons (PAHs), as a kind of endocrine disruptors, can enter the fetus body cross the placental barrier from prenatal PAHs exposure to cause adverse birth outcomes. However, it is controversial association between prenatal PAHs exposure and low birth weight (LBW) of their infants. So the present study aimed to estimate the effects of prenatal PAHs exposure during the pregnancy on the risk of LBW in a Chinese cohort through modifying the DNA methylation states. A longitudinal prospective study with 407 pregnant women was established from May to October 2019. The prenatal PAHs exposure during the pregnancy was assessed using the internal dose such as the PAHs metabolites and PAH-DNA adducts in the umbilical cord blood. The methylation levels of genomic DNA and growth-related genes (IGF1 and IGF2) were assessed, while the expressions of these genes were both determined by RT-PCR and Elisa methods. The growth outcomes and relevant Z-scores were recorded at birth. The correlations between the DNA methylation status and concentrations of PAHs, expression levels of growth-related genes and body weight/WAZ were investigated as the measures. According to the PAH-DNA adducts, the subjects were divided into two groups: PAHs-exposed group (PAH-DNA adducts>0, n = 55) and non-exposed group (PAH-DNA adducts = 0, n = 352). Compared with the non-exposed group, it displayed marked decreased birth weight, and increased concentrations of PAHs and DNA methylation levels of the global genomic, IGF1 and IGF2 with their lower expressions in the PAHs-exposed group. These hypermethylation (global genomic, CpG14 and CpG15 of IGF1, and CpG14 of IGF2) were positively correlated with the contents of PAHs in the umbilical cord blood, and negatively correlated with the growth outcomes and their expressions. Totally, prenatal PAHs exposures may contribute to an increased risk of LBW of their infants by modulating the DNA methylation states of genomic DNA and growth-related genes (IGF1 and IGF2) in the umbilical cord blood, which could provide the prenatal prevention of PAHs exposure from possible environmental media except from the occupation and tobacco usage to ensure the health of their infants.

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 chemical composition and toxicological effects of fine particulate matter (PM2.5) emitted from different cooking styles

The mass, chemical composition and toxicological properties of fine particulates (PM_2.5) emitted from cooking activities in three Hong Kong based restaurants and two simulated cooking experiments were characterized. Extracts from the PM_2.5 samples elicited significant biological activities [cell viability, generation of reactive oxygen species (ROS), DNA damage and inflammation effect (TNF-α)] in a dose-dependent manner. The composition of PAHs, oxygenated PAHs (OPAHs) and azaarenes (AZAs) mixtures differed between samples. The concentration ranges of the Σ30PAHs, Σ17OPAHs and Σ4AZAs and Σ7Carbonyls in the samples were 9627-23,452 pg m^-3, 503-3700 pg m^-3, 33-263 pg m^-3 and 158 - 5328 ng m^-3, respectively. Cell viability caused by extracts from the samples was positively correlated to the concentration of benzo[a]anthracene, indeno[1,2,3-cd]pyrene and 1,4-naphthoquinone in the PM_2.5 extracts. Cellular ROS production (upon exposure to extracts) was positively correlated with the concentrations of PM_2.5, decaldehyde, acridine, Σ17OPAHs and 7 individual OPAHs. TNF-α showed significant positive correlations with the concentrations of most chemical species (elemental carbon, 16 individual PAHs including benzo[a]pyrene, Σ30PAHs, SO₄^2-, Ca²⁺, Ca, Na, K, Ti, Cr, Mn, Fe, Cu and Zn). The concentrations of Al, Ti, Mn, Σ30PAHs and 8 individual PAHs including benzo[a]pyrene in the samples were positively correlated with DNA damage caused by extracts from the samples. This study demonstrates that inhalation of PM_2.5 emitted from cooking could result in adverse human health effects.

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.

Toxicity of Water- and Organic-Soluble Wood Tar Fractions from Biomass Burning in Lung Epithelial Cells

Widespread smoke from wildfires and biomass burning contributes to air pollution and the deterioration of air quality and human health. A common and major emission of biomass burning, often found in collected smoke particles, is spherical wood tar particles, also known as "tar balls". However, the toxicity of wood tar particles and the mechanisms that govern their health impacts and the impact of their complicated chemical matrix are not fully elucidated. To address these questions, we generated wood tar material from wood pyrolysis and isolated two main subfractions: water-soluble and organic-soluble fractions. The chemical characteristics as well as the cytotoxicity, oxidative damage, and DNA damage mechanisms were investigated after exposure of A549 and BEAS-2B lung epithelial cells to wood tar. Our results suggest that both wood tar subfractions reduce cell viability in exposed lung cells; however, these fractions have different modes of action that are related to their physicochemical properties. Exposure to the water-soluble wood tar fraction increased total reactive oxygen species production in the cells, decreased mitochondrial membrane potential (MMP), and induced oxidative damage and cell death, probably through apoptosis. Exposure to the organic-soluble fraction increased superoxide anion production, with a sharp decrease in MMP. DNA damage is a significant process that may explain the course of toxicity of the organic-soluble fraction. For both subfractions, exposure caused cell cycle alterations in the G2/M phase that were induced by upregulation of p21 and p16. Collectively, both subfractions of wood tar are toxic. The water-soluble fraction contains chemicals (such as phenolic compounds) that induce a strong oxidative stress response and penetrate living cells more easily. The organic-soluble fraction contained more polycyclic aromatic hydrocarbons (PAHs) and oxygenated PAHs and induced genotoxic processes, such as DNA damage.

Polycyclic aromatic compounds in particulate matter and indoor dust at preschools in Stockholm, Sweden: Occurrence, sources and genotoxic potential in vitro

Children spend a significant amount of their day in preschool; thus, environmental quality at preschools may have an impact on children's health. In the present study, we analyzed polycyclic aromatic compounds (PACs), including PAHs, alkylated PAHs and oxygenated PAHs (OPAHs), in indoor and outdoor air particulate matter (PM₁₀) and indoor dust at preschools in Stockholm, Sweden. There were significant correlations between PAC levels in outdoor and indoor PM₁₀, with in general higher PAC levels outdoors. Fluoranthene and pyrene were detected at highest levels in all sample types, although phenanthrene and methylated phenanthrene derivatives also were found at high levels in indoor dust. In addition, the highly carcinogenic PAHs 7H-benzo[c]fluorene, 7,12-dimethylbenz[a]anthracene, benz[j]aceanthrylene, and dibenzo[a,l]pyrene were detected in some samples. Benzanthrone was the most prevalent OPAH in PM₁₀ samples and 9,10-anthraquinone in indoor dust. Based on diagnostic ratios and Positive Matrix Factorization we identified vehicle emission and biomass burning as important PAC sources for all samples analyzed. However, poor correlation between PAC levels in indoor PM₁₀ and indoor dust suggested additional sources for the latter. Measuring activation of DNA damage signaling in human cells exposed to organic extracts of the samples indicated substantial genotoxic potential of outdoor PM₁₀ and indoor dust. Determination of benzo[a]pyrene equivalents demonstrated that the highly potent PAHs benz[j]aceanthrylene and dibenz[a,h]anthracene contributed more than 20% to the total carcinogenic potency of the samples. We conclude that PAC levels at Stockholm preschools are relatively low but that outdoor air quality may impact on the indoor environment.

What is necessary for next-generation atmospheric environmental standards? Recent research trends for PM2.5 -bound polycyclic aromatic hydrocarbons and their derivatives

The air pollution associated with PM_2.5 kills 7 million people every year in the world, especially threatening the health of children in developing countries. However, the current air quality standards depend mainly on particle size. PM_2.5 contains many carcinogenic/mutagenic polycyclic aromatic hydrocarbons (PAHs) and their derivatives such as nitropolycyclic aromatic hydrocarbons and oxygenated PAHs. Among them, environmental standards and guidelines have been set for benzo[a]pyrene by few countries and international organizations. Recent research reports showed that these pollutants are linked to diseases other than lungs, and new methods have been developed for determining trace levels of not only PAHs but also their derivatives. It is time to think about the next-generation environmental standards. This article aims to (a) describe recent studies on the health effects of PAHs and their derivatives other than cancer, (b) describe new analytical methods for PAH derivatives, and (c) discuss the targets for the next-generation standards.

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.

Inflammation, oxidative stress and genotoxicity responses to biodiesel emissions in cultured mammalian cells and animals

Biodiesel fuels are alternatives to petrodiesel, especially in the transport sector where they have lower carbon footprint. Notwithstanding the environmental benefit, biodiesel fuels may have other toxicological properties than petrodiesel. Particulate matter (PM) from petrodiesel causes cancer in the lung as a consequence of delivery of genotoxic polycyclic aromatic hydrocarbons, oxidative stress and inflammation. We have reviewed articles from 2002 to 2019 (50% of the articles since 2015) that have described toxicological effects in terms of genotoxicity, oxidative stress and inflammation of biodiesel exhaust exposure in humans, animals and cell cultures. The studies have assessed first generation biodiesel from different feedstock (e.g. rapeseed and soy), certain second generation fuels (e.g. waste oil), and hydrogenated vegetable oil. It is not possible to rank the potency of toxicological effects of specific biodiesel fuels. However, exposure to biodiesel exhaust causes oxidative stress, inflammation and genotoxicity in cell cultures. Three studies in animals have not indicated genotoxicity in lung tissue. The database on oxidative stress and inflammation in animal studies is larger (13 studies); ten studies have reported increased levels of oxidative stress biomarkers or inflammation, although the effects have been modest in most studies. The cell culture and animal studies have not consistently shown a different potency in effect between biodiesel and petrodiesel exhausts. Both increased and decreased potency have been reported, which might be due to differences in feedstock or combustion conditions. In conclusion, combustion products from biodiesel and petrodiesel fuel may evoke similar toxicological effects on genotoxicity, oxidative stress and inflammation.