Genotoxicity of airborne PM2.5 assessed by salmonella and comet assays in five cities of the Emilia-Romagna (Italy) mutagenicity monitoring network

Integrated meta-analyses of genome-wide effects of PM2.5 in human cells identifies widespread dysregulation of genes and pathways associated with cancer progression and patient survival

Epidemiological studies have consistently shown a positive association between exposure to ambient PM2.5, a major component of air pollution, and various types of cancer. Previous biological research has primarily focused on the association between PM2.5 and lung cancer, with limited investigation into other cancer types. In this study, we conducted a meta-analysis on multiple PM2.5-treated normal human cell lines to identify potential molecular targets and pathways of PM2.5. Our analysis revealed 310 common differentially expressed genes (DEGs) that exhibited significant dysregulation upon exposure to PM2.5. These dysregulated genes covered a diverse range of functional categories, including oncogenes, tumor suppressor genes, and immune-related genes, which collectively contribute to PM2.5-induced carcinogenesis. Pathway enrichment analysis revealed the up-regulation of pathways associated with HIF-1, VEGF, and MAPK signalling, all of which have been implicated in various cancers. Induction in the levels of HIF pathway genes (HIF1⍺, HIF2⍺, VEGFA, BNIP3, EPO and PGK1) upon PM2.5 treatment was also confirmed by qRT-PCR. Furthermore, the construction of a protein-protein interaction (PPI) network unveiled hub genes, such as NQO1 and PDGFRB, that are known to be dysregulated and significantly correlated with overall survival in lung and breast cancer patients, suggesting their potential clinical significance. This study provides a deep insight into how PM2.5-mediated dysregulation of oncogenes or tumor suppressor genes across various human tissues may play an important role in PM2.5-induced carcinogenesis. Further exploration of these dysregulated molecular targets may enhance our understanding of the biological effects of PM2.5 and facilitate the development of preventive strategies and targeted therapies for PM2.5-associated cancers.

Direct Impact of the Air on Mutant Cells for Mutagenicity Assessments in Urban Environments

BACKGROUND

Urban air pollution is recognized as a critical problem for public health and is classified as a carcinogen for humans. A great number of studies have focused on the monitoring of urban air mutagenicity. One of the best-known and applied methods for assessing mutagenicity is the Ames test, a bacterial reverse mutation test. The classic protocol for assessing air mutagenicity involves the concentration of particulate matter (PM) on filters and subsequent extraction using organic solvents. This work aimed to develop a method for the evaluation of air mutagenicity directly impacted by air on microbial plates already containing an Ames' microbial sensor.

METHODS

A specific six-month sampling campaign was carried out in Turin in a period with high air pollution. Samples were tested for mutagenicity on Salmonella typhimurium strains TA98, TA100, and YG1024 with the traditional method and with the new direct method.

RESULTS

The new protocol is able to evaluate the mutagenicity of the sampled air and obtain repeatable results. The final sensitivity is similar to the traditional method (≈10 net revertants/m3); however, the mutagenic response is due to the complete air pollution mixture, including volatile and semivolatile pollutants avoiding the concentration of filters and the following laborious extraction procedures.

CONCLUSIONS

Despite some critical issues in contamination control, the method is easier, faster, and less expensive than traditional methods.

Genotoxicity by rapeseed methyl ester and hydrogenated vegetable oil combustion exhaust products in lung epithelial (A549) cells

Biofuel is an attractive substitute for petrodiesel because of its lower environmental footprint. For instance, the polycyclic aromatic hydrocarbons (PAH) emission per fuel energy content is lower for rapeseed methyl ester (RME) than for petrodiesel. This study assesses genotoxicity by extractable organic matter (EOM) of exhaust particles from the combustion of petrodiesel, RME, and hydrogenated vegetable oil (HVO) in lung epithelial (A549) cells. Genotoxicity was assessed as DNA strand breaks by the alkaline comet assay. EOM from the combustion of petrodiesel and RME generated the same level of DNA strand breaks based on the equal concentration of total PAH (i.e. net increases of 0.13 [95% confidence interval (CI): 0.002, 0.25, and 0.12 [95% CI: 0.01, 0.24] lesions per million base pairs, respectively). In comparison, the positive control (etoposide) generated a much higher level of DNA strand breaks (i.e. 0.84, 95% CI: 0.72, 0.97) lesions per million base pairs. Relatively low concentrations of EOM from RME and HVO combustion particles (<116 ng/ml total PAH) did not cause DNA strand breaks in A549 cells, whereas benzo[a]pyrene and PAH-rich EOM from petrodiesel combusted using low oxygen inlet concentration were genotoxic. The genotoxicity was attributed to high molecular weight PAH isomers with 5-6 rings. In summary, the results show that EOM from the combustion of petrodiesel and RME generate the same level of DNA strand breaks on an equal total PAH basis. However, the genotoxic hazard of engine exhaust from on-road vehicles is lower for RME than petrodiesel because of lower PAH emission per fuel energy content.

The relationship between polycyclic aromatic hydrocarbons exposure and serum klotho among adult population

Background

Klotho is an important factor involving aging process. Recently, polycyclic aromatic hydrocarbons (PAHs) exposure was reported to have adverse impact on DNA methylation associated with aging. The aim of the current study was to determine the relationship between serum klotho and PAHs exposure in an adult population.

Methods

A total of 2597 participants obtained from NHANES 2015–2016 were included in this cross-sectional study. Serum klotho levels were analyzed by enzyme-linked immunosorbent assay (ELISA). PAHs exposure was estimated by urinary sample using liquid chromatography-tandem mass spectrometry. The relationship between serum klotho and exposure to PAHS was analyzed by a multivariable linear regression model.

Results

2-napthol and 3-fluorene were significantly associated with decreased klotho. After fully adjusting pertinent variables, PAH exposure was significantly associated with decreased klotho, particularly in men.

Conclusion

In the present study we highlighted the significant association between PAHs exposure and serum klotho levels. The importance of environmental effect on aging process and age-related disorders should be paid more attention and clinical intervention is necessary.

The Parallel Transformations of Polycyclic Aromatic Hydrocarbons in the Body and in the Atmosphere

BACKGROUND

Polycyclic aromatic hydrocarbons (PAHs) emitted from combustion sources are known to be mutagenic, with more potent species also being carcinogenic. Previous studies show that PAHs can undergo complex transformations both in the body and in the atmosphere, yet these transformation processes are generally investigated separately.

OBJECTIVES

Drawing from the literature in atmospheric chemistry and toxicology, we highlight the parallel transformations of PAHs that occur in the atmosphere and the body and discuss implications for public health. We also examine key uncertainties related to the toxicity of atmospheric oxidation products of PAHs and explore critical areas for future research.

DISCUSSION

We focus on a key mode of toxicity for PAHs, in which metabolic processes (driven by cytochrome P450 enzymes), leads to the formation of oxidized PAHs that can damage DNA. Such species can also be formed abiotically in the atmosphere from natural oxidation processes, potentially augmenting PAH toxicity by skipping the necessary metabolic steps that activate their mutagenicity. Despite the large body of literature related to these two general pathways, the extent to which atmospheric oxidation affects a PAH's overall toxicity remains highly uncertain. Combining knowledge and promoting collaboration across both fields can help identify key oxidation pathways and the resulting products that impact public health.

CONCLUSIONS

Cross-disciplinary research, in which toxicology studies evaluate atmospheric oxidation products and their mixtures, and atmospheric measurements examine the formation of compounds that are known to be most toxic. Close collaboration between research communities can help narrow down which PAHs, and which PAH degradation products, should be targeted when assessing public health risks. https://doi.org/10.1289/EHP9984.

The North-western Italy air quality monitoring network: Improving experience of PM2.5 assessment with mutagenicity assay

The finest fraction of Particulate Matter (PM2.5) carries a large number of pollutants, some of which are assessed as genotoxic, such as some Polycyclic Aromatic Hydrocarbons (PAHs). In many countries, PM2.5 in combination with some PAHs are monitored to assess the concentrations of pollutants, while the air quality is rarely assessed by means of biological assays. Epidemiological studies have demonstrated a significant correlation between these two pollutants and human adverse effects, in particular on the respiratory system. Nevertheless, other air pollutants can induce a biological effect and the cumulative effect of the PM2.5 complex mixture may not be easily deduced by PM2.5 and PAH levels. This study aimed to combine the legislative monitoring of PM2.5 with the study of its mutagenicity. During a full year, daily air samples were collected in nine sites of the North-western Italy air quality monitoring network (Piedmont Region) and PM2.5 and PAH concentrations were assessed. Monthly pooled organic extracts were tested with the Salmonella assay using TA98 and TA100 strains, with and without metabolic activation (±S9), and using TA98NR and YG1021 strains. In all sites, a positive response was observed for TA98 and TA100 especially without S9. A significant mutagenic seasonal variation was detected, with higher mutagenicity in winter and lower responses in summer (average total mutagenicity ratio 27:1). The response of TA98NR and YG1021 compared with TA98 suggested a significant contribution of nitro-compounds to the mutagenicity. No significant differences were found between urban background and rural sites denoting the spread of pollution. A mutagenicity increase, 1.28 Total Mutagenicity Factor/20 m³, was observed for each PM2.5 μg increment. PAH levels and corresponding Toxic Equivalent Factors were highly correlated to mutagenicity results. This work confirms that complex environmental mixtures can be appropriately assessed through the implementation of physical-chemical analyzes with bioassays able to evaluate synergistic and antagonistic effects, especially for highest and lowest pollution settings.

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.

Study on Pollution Characterization and Source Apportionment of Daytime and Nighttime PM2.5 Samples in an Urban Residential Community in Different Weather Conditions

Daytime and nighttime PM_2.5 samples were collected from an urban community in Tianjin. The major chemical components in PM_2.5, including metal elements, polycyclic aromatic hydrocarbons and inorganic water-soluble ions, were monitored. A positive matrix factorization (PMF) model was used to apportion the potential sources of PM_2.5 under different weather conditions. When the Air Quality Index (AQI) was below 200, the concentrations of BaA, BbF, BkF, Na and NO₃^- during the nighttime were higher than those during the daytime. PMF analysis indicated that secondary aerosols (37.3%), biomass burning (26.7%) and coal combustion (26.0%) were important sources of PM_2.5 in the urban residential community when the AQI was greater than 200. When the AQI was less than 200 in the urban residential community, the main sources of PM_2.5 in the urban residential community were secondary aerosols (50.7%) and fossil fuel combustion (47.2%). The pollution status of PM_2.5 in the residential community of the urban area was serious, and the source apportionments of the PM_2.5 samples in the urban area were different under different weather conditions.

Study of in vitro and in vivo genotoxic effects of air pollution fine (PM2.5-0.18) and quasi-ultrafine (PM0.18) particles on lung models

Air pollution and particulate matter (PM) are classified as carcinogenic to humans. Pollutants evidence for public health concern include coarse (PM₁₀) and fine (PM_2.5) particles. However, ultrafine particles (PM_0.1) are assumed to be more toxic than larger particles, but data are still needed to better understand their mechanism of action. In this context, the aim of our work was to investigate the in vitro and in vivo genotoxic potential of fine (PM_2.5-018) and quasi ultra-fine (PM_0.18) particles from an urban-industrial area (Dunkirk, France) by using comet, micronucleus and/or gene mutation assays. In vitro assessment was performed with 2 lung immortalized cell lines (BEAS-2B and NCI-H292) and primary normal human bronchial epithelial cells (NHBE) grown at the air-liquid interface or in submerged conditions (5 µg PM/cm²). For in vivo assessment, tests were performed after acute (24 h, 100 µg PM/animal), subacute (1 month, 10 µg PM/animal) and subchronic (3 months, 10 µg PM/animal) intranasal exposure of BALB/c mice. In vitro, our results show that PM_2.5-018 and PM_0.18 induced primary DNA damage but no chromosomal aberrations in immortalized cells. Negative results were noted in primary cells for both endpoints. In vivo assays revealed that PM_2.5-018 and PM_0.18 induced no significant increases in DNA primary damage, chromosomal aberrations or gene mutations, whatever the duration of exposure. This investigation provides initial answers regarding the in vitro and in vivo genotoxic mode of action of PM_2.5-018 and PM_0.18 at moderate doses and highlights the need to develop standardized specific methodologies for assessing the genotoxicity of PM. Moreover, other mechanisms possibly implicated in pulmonary carcinogenesis, e.g. epigenetics, should be investigated.

Firefighters exposure to fire emissions: Impact on levels of biomarkers of exposure to polycyclic aromatic hydrocarbons and genotoxic/oxidative-effects

Firefighters represent one of the riskiest occupations, yet due to the logistic reasons, the respective exposure assessment is one of the most challenging. Thus, this work assessed the impact of firefighting activities on levels of urinary monohydroxyl-polycyclic aromatic hydrocarbons (OHPAHs; 1-hydroxynaphthalene, 1-hydroxyacenaphthene, 2-hydroxyfluorene, 1-hydroxyphenanthrene, 1-hydroxypyrene, 3-hydroxybenzo(a)pyrene) and genotoxic/oxidative-effect biomarkers (basal DNA and oxidative DNA damage) of firefighters from eight firehouses. Cardiac frequency, blood pressure and arterial oxygen saturation were also monitored. OHPAHs were determined by liquid-chromatography with fluorescence detection, while genotoxic/oxidative-effect biomarkers were assessed by the comet assay. Concentrations of total OHPAHs were up to 340% higher (p ≤ 0.05) in (non-smoking and smoking) exposed workers than in control subjects (non-smoking and non-exposed to combat activities); the highest increments were observed for 1-hydroxynaphthalene and 1-hydroxyacenaphthene (82-88% of ∑OHPAHs), and for 2-hydroxyfluorene (5-15%). Levels of biomarker for oxidative stress were increased in non-smoking exposed workers than in control group (316%; p ≤ 0.001); inconclusive results were found for DNA damage. Positive correlations were found between the cardiac frequency, ∑OHPAHs and the oxidative DNA damage of non-smoking (non-exposed and exposed) firefighters. Evidences were raised regarding the simultaneous use of these biomarkers for the surveillance of firefighters' health and to better estimate the potential short-term health risks.

Oxidative stress, mutagenic effects, and cell death induced by retene

Retene (RET) is the most abundant polycyclic aromatic hydrocarbon (PAH) released upon burning of cellulose, although it is not considered as one of the priority PAHs and is not included for risk assessments by the US Environmental Protection Agency (US-EPA). There are only a few studies concerning the toxic effects of RET. To the best of our knowledge, this study is the first one to examine whether RET, in an environmental concentration, plays a crucial role in the induction of oxidative stress in A549 lung cell line, and its consequence as such as mutagenicity and cell death. Our results revealed that RET was able to significantly decrease cell viability only at 72 h of exposure, increase oxidative stress, mitochondrial membrane potential and mitochondrial contents, leading an increased reactive oxygen species (ROS) production. Mutagenic activity was not detected in Salmonella strains, suggesting that RET does not induce base-pair substitution (TA100), frameshift (TA98 and TA97a) and transition/transversion (TA102) mutations. However, exposure to RET led to a significant increase in micronuclei (MN), nucleoplasmic bridges (NPBs), and nuclear buds (NBUDs) frequency, as well as cell death, mainly due to necrosis. Taken together, the results of our study provide new evidence suggesting that RET promotes oxidative stress, contributes to the processes of genomic instability, and favors necrosis. Thus, we highlight the importance of including RET in routine environmental analyses in the future as a potential risk factor involved in complex diseases and carcinogenesis.

Characterization of urban aerosol: Seasonal variation of genotoxicity of the water-soluble portion of PM2.5 and PM1

Urban particulate matter (PM) is a complex mixture of several classes of chemicals: elemental carbon, ammonium, sulfates, nitrates, organic compounds and metals. For a long time, numerous studies had shown that PM causes health problems and, in 2013, it has been classified by the International Agency for Research on Cancer as carcinogenic to humans (group 1). Furthermore, it's known that the fine fraction of PM is the most genotoxic, and that smaller particles are retained by the lower respiratory system, making fine particles a public health concern. In this study we characterize the water-soluble portion of urban aerosol from Bologna, a county town of Emilia-Romagna in the north of Italy, by collecting the finest fractions of airborne particles, PM_2.5 and PM₁, in three different seasons (winter, summer and autumn) over a three-year period. The genotoxicity of the water-soluble extracts was evaluated, both by a standard and a enzyme-modified Comet assay and also by the Micronucleus test, with lung adenocarcinoma epithelial cells (A549). In the same extracts, water-soluble metals (V, Ni, Cu, Cr, Fe) were detected and associations between the physicochemical parameters of PM and genotoxicity were evaluated. DNA strand breaks were found in summer and winter samples in the Comet experiments, whereas oxidative damage was induced by autumn extracts; winter samples induced chromosome breakage or loss in A549 cells. Iron and copper were the most abundant transition metals in both fractions and both were associated with micronuclei induction, whereas chromium is linked with oxidative damage. This study also shows that the water-soluble fraction of PM contributes to global genotoxicity and that transition metals play a role, therefore both organic and water-soluble fractions should be considered in an air-quality monitoring program.

Fresh and ozonized black carbon promoted DNA damage and repair responses in A549 cells

Nano-sized ambient black carbon (BC) is hypothesized to pose a serious threat to human health. After emission into the air, the atmospheric oxidation process can modify its physiochemical properties and change its biological responses. In this study, we aimed to compare different DNA damage and repair responses promoted by fresh BC (FBC) and ozone oxidized-BC (OBC). The cell apoptosis, cell arrest, DNA damage and repair were investigated in A549 cells after treatment with FBC and OBC. Associated gene expressions were measured with the reverse transcription quantitative polymerase chain reaction (RT-qPCR) method. Both FBC and OBC could induce cell apoptosis in A549 cells with up-regulated gene of promyelocytic leukemia protein (pml) and down-regulated gene of anti-apoptotic B-cell lymphoma-2 (bcl-2). FBC caused cell cycle arrest at S and G2/M phases, which was associated with up-regulated ataxia telangiectasia mutated (atm), checkpoint kinase 2 (chk2), structural maintenance of chromosomes 1 (smc1) and cell division cycle 25 homolog A (cdc25a) genes. OBC promoted cell cycle arrest at the S phase with up-regulated genes of atm, chk2 and smc1. Both FBC and OBC induced oxidative DNA damage and time-dependent DNA repair responses with increased gene expressions of breast cancer susceptibility protein 1 (brca1), recombination protein A paralog B (rad51b), methyl methanesulfonate-sensitivity protein 22-like and tonsoku-like (mms22l). Compared to FBC, OBC could cause more sufficient DNA damage repair responses through cell cycle arrest at the S phase, resulting in relatively weaker DNA damages.

Beyond the obvious: Environmental health implications of polar polycyclic aromatic hydrocarbons

The genotoxic, mutagenic and carcinogenic effects of polar polycyclic aromatic hydrocarbons (polar PAHs) are believed to surpass those of their parent PAHs; however, their environmental and human health implications have been largely unexplored. Oxygenated PAHs (oxy-PAHs) is a critical class of polar PAHs associated with carcinogenic effects without enzymatic activation. They also cause an upsurge in reactive oxygen species (ROS) in living cells. This results in oxidative stress and other consequences, such as abnormal gene expressions, altered protein activities, mutagenesis, and carcinogenesis. Similarly, some nitrated PAHs (N-PAHs) are probable human carcinogens as classified by the International Agency for Research on Cancer (IARC). Heterocyclic PAHs (polar PAHs containing nitrogen, sulphur and oxygen atoms within the aromatic rings) have been shown to be potent endocrine disruptors, primarily through their estrogenic activities. Despite the high toxicity and enhanced environmental mobility of many polar PAHs, they have attracted only a little attention in risk assessment of contaminated sites. This may lead to underestimation of potential risks, and remediation end points. In this review, the toxicity of polar PAHs and their associated mechanisms of action, including their role in mutagenic, carcinogenic, developmental and teratogenic effects are critically discussed. This review suggests that polar PAHs could have serious toxicological effects on human health and should be considered during risk assessment of PAH-contaminated sites. The implications of not doing so were argued and critical knowledge gaps and future research requirements discussed.

Genotoxic and cytotoxic properties of PM2.5 collected over the year in Wrocław (Poland)

In the ambient is >2000 chemical substances, some of them are absorbed on the surface of the particulate matter and may causes many health problems. Air pollution is responsible for >3.2 million premature deaths which classifies it as a second place environmental risk factor. Especially dangerous for health are polycyclic aromatic hydrocarbons and their derivatives which shows mutagenic and carcinogenic properties. Air pollutions were also classified by International Agency for Research on Cancer to group which carcinogenic properties on human were proved by available knowledge. Air pollutions, are one of the biggest problem in Polish cities. The article presents results of mutagenicity, genotoxicity and cytotoxicity researches conducted on a particulate matter fraction 2.5 μm collected during all year long in Wroclaw agglomeration (Poland). The material was collected on filters using high-flow air aspirator and extracted using dichloromethane. Additionally it was fractionated into 4 parts containing: all pollutants, only polycyclic aromatic hydrocarbons, nitro derivatives of PAHs and dinitro derivatives of PAHS. Dry residue of this fraction was dissolving in DMSO and tested using biological methods. Biological methods include mutagenicity properties which are investigated by Salmonella assay (Ames assay). Other biological method was comet assay and 4 parameter cytotoxicity test PAN-I assay. Results of the conducted experiments show differences in mutagenic, genotoxic and cytotoxic properties between seasons of collection and between volumes of dust pollutions fractions. The worst properties shows particles collected in autumn and winter season Results showed also some correlations in results obtained during different methods and properties. Due to the limited possibilities of testing all chemical compounds present in the PM2.5 fraction, it is recommended to carry out tests based on a set of genotoxic and cytotoxic tests, which is confirmed by the conducted research.