Chemical characterisation of the coarse and fine particulate matter in the environment of an underground railway system: cytotoxic effects and oxidative stress-a preliminary study

Toxicity of airborne nanoparticles: Facts and challenges

Air pollution is one of the most severe environmental healthhazards, and airborne nanoparticles (diameter <100 nm) are considered particularly hazardous to human health. They are produced by various sources such as internal combustion engines, wood and biomass burning, and fuel and natural gas combustion, and their origin, among other parameters, determines their intrinsic toxicity for reasons that are not yet fully understood. Many constituents of the nanoparticles are considered toxic or at least hazardous, including polycyclic aromatic hydrocarbons (PAHs) and heavy metal compounds, in addition to gaseous pollutants present in the aerosol fraction, such as NOx, SO2, and ozone. All these compounds can cause oxidative stress, mitochondrial damage, inflammation in the lungs and other tissues, and cellular organelles. Epidemiological investigations concluded that airborne pollution may affect the respiratory, cardiovascular, and nervous systems. Moreover, particulate matter has been linked to an increased risk of lung cancer, a carcinogenic effect not related to DNA damage, but to the cellular inflammatory response to the pollutants, in which the release of cytokines promotes the proliferation of pre-existing mutated cancer cells. The mechanisms behind toxicity can be investigated experimentally using cell cultures or animal models. Methods for gathering particulate matter have been explored, but standardized protocols are needed to ensure that the samples accurately represent chemical mixtures in the environment. Toxic constituents of nanoparticles can be studied in animal and cellular models, but designing realistic exposure settings is challenging. The air-liquid interface (ALI) system directly exposes cells, mimicking particle inhalation into the lungs. Continuous research and monitoring of nanoparticles and other airborne pollutants is essential for understanding their effects and developing active strategies to mitigate their risks to human and environmental health.

Metal and oxidative potential exposure through particle inhalation and oxidative stress biomarkers: a 2-week pilot prospective study among Parisian subway workers

OBJECTIVE

In this pilot study on subway workers, we explored the relationships between particle exposure and oxidative stress biomarkers in exhaled breath condensate (EBC) and urine to identify the most relevant biomarkers for a large-scale study in this field.

METHODS

We constructed a comprehensive occupational exposure assessment among subway workers in three distinct jobs over 10 working days, measuring daily concentrations of particulate matter (PM), their metal content and oxidative potential (OP). Individual pre- and post-shift EBC and urine samples were collected daily. Three oxidative stress biomarkers were measured in these matrices: malondialdehyde (MDA), 8-hydroxy-2'deoxyguanosine (8-OHdG) and 8-isoprostane. The association between each effect biomarker and exposure variables was estimated by multivariable multilevel mixed-effect models with and without lag times.

RESULTS

The OP was positively associated with Fe and Mn, but not associated with any effect biomarkers. Concentration changes of effect biomarkers in EBC and urine were associated with transition metals in PM (Cu and Zn) and furthermore with specific metals in EBC (Ba, Co, Cr and Mn) and in urine (Ba, Cu, Co, Mo, Ni, Ti and Zn). The direction of these associations was both metal- and time-dependent. Associations between Cu or Zn and MDAEBC generally reached statistical significance after a delayed time of 12 or 24 h after exposure. Changes in metal concentrations in EBC and urine were associated with MDA and 8-OHdG concentrations the same day.

CONCLUSION

Associations between MDA in both EBC and urine gave opposite response for subway particles containing Zn versus Cu. This diverting Zn and Cu pattern was also observed for 8-OHdG and urinary concentrations of these two metals. Overall, MDA and 8-OHdG responses were sensitive for same-day metal exposures in both matrices. We recommend MDA and 8-OHdG in large field studies to account for oxidative stress originating from metals in inhaled particulate matter.

Toxicity and health effects of ultrafine particles: Towards an understanding of the relative impacts of different transport modes

Exposure to particulate matter (PM) has been associated with a wide range of adverse health effects, but it is still unclear how particles from various transport modes differ in terms of toxicity and associations with different human health outcomes. This literature review aims to summarize toxicological and epidemiological studies of the effect of ultrafine particles (UFPs), also called nanoparticles (NPs, <100 nm), from different transport modes with a focus on vehicle exhaust (particularly comparing diesel and biodiesel) and non-exhaust as well as particles from shipping (harbor), aviation (airport) and rail (mainly subway/underground). The review includes both particles collected in laboratory tests and the field (intense traffic environments or collected close to harbor, airport, and in subway). In addition, epidemiological studies on UFPs are reviewed with special attention to studies aimed at distinguishing the effects of different transport modes. Results from toxicological studies indicate that both fossil and biodiesel NPs show toxic effects. Several in vivo studies show that inhalation of NPs collected in traffic environments not only impacts the lung, but also triggers cardiovascular effects as well as negative impacts on the brain, although few studies compared NPs from different sources. Few studies were found on aviation (airport) NPs, but the available results suggest similar toxic effects as traffic-related particles. There is still little data related to the toxic effects linked to several sources (shipping, road and tire wear, subway NPs), but in vitro results highlighted the role of metals in the toxicity of subway and brake wear particles. Finally, the epidemiological studies emphasized the current limited knowledge of the health impacts of source-specific UFPs related to different transport modes. This review discusses the necessity of future research for a better understanding of the relative potencies of NPs from different transport modes and their use in health risk assessment.

Toxicological and Mutagenic Effects of Particulate Matter from Domestic Activities

People spend most of their time indoors, particularly in their houses where daily activities are carried out, enhancing particulate matter (PM) emissions with consequent adverse health impacts. This study intended to appraise the toxicological and mutagenic responses of particulate matter with a diameter less than 10 μm (PM₁₀) released from cooking and ironing activities under different conditions. The cytotoxicity of the PM₁₀ total organic extracts was tested in A549 cells using the WST-8 and the lactate dehydrogenase (LDH) assays, while the interference in cell cycle dynamics and reactive oxygen species (ROS) production was analysed by flow cytometry. The S. typhimurium TA98 and TA100 Ames tester strains with and without metabolic activation were employed to determine the mutagenic potential of the PM₁₀-bound polycyclic aromatic hydrocarbons (PAHs). PM₁₀ organic extracts decreased the metabolic activity of A549 cells; however, no effects in the LDH release were observed. An increase in ROS levels was registered only for cells treated with PM₁₀ at IC₂₀ from steam ironing, in low ventilation conditions, while cell cycle dynamics was only affected by exposure to PM₁₀ at IC₂₀ from frying horse mackerel and grilling boneless pork strips. No mutagenic effects were observed for all the PM₁₀-bound PAHs samples.

Exposure to ambient particulate matter and hyperuricemia: An eight-year prospective cohort study on male traffic officers in China

BACKGROUND AND OBJECTIVES

Studies on the effects of airborne particulates of diameter ≤ 1 µm (PM₁), airborne particulates of diameter ≤ 2.5 µm (PM_2.5) and airborne particulates of diameter ranges from 1 to 2.5 µm (PM_1-2.5) on incidence of hyperuricemia are limited. We aimed to investigate the associations between PM₁, PM_2.5, and PM_1-2.5 and hyperuricemia among male traffic officers.

METHODS

We conducted a prospective cohort study of 1460 traffic officers without hyperuricemia in Guangzhou, China from 2009 to 2016. Exposures of PM₁ and PM_2.5 were estimated with a spatiotemporal model. PM_1-2.5 concentrations were calculated by subtracting PM₁ from PM_2.5 concentrations. Cox's proportional hazards regressions models were used to examine the association between PM₁, PM_2.5, and PM_1-2.5 and hyperuricemia, adjusted for potential confounders. Associations between PM₁, PM_2.5, and PM_1-2.5 and serum uric acid (SUA) levels were evaluated with multiple linear regression models.

RESULTS

Hazard ratios (HRs) and 95% confidence intervals (CIs) of hyperuricemia associated with 10 μg/m³ increment in PM₁, PM_2.5, and PM_1-2.5 were 1.67 (95% CI:1.30-2.36), 1.49 (95% CI: 1.27-1.75), and 2.18 (95% CI: 1.58-3.02), respectively. The SUA concentrations increased by 12.23 μmol/L (95% CI: 5.91-18.56), 6.93 μmol/L (95% CI: 3.02-10.84), and 8.72 μmol/L (95% CI: 0.76-16.68) per 10 μg/m³ increase in PM₁, PM_2.5, and PM_1-2.5, respectively. Stratified analyses indicated the positive associations of PM_2.5 and PM_1-2.5 with SUA levels were stronger in non-smokers, and PM₁, PM_2.5, and PM_1-2.5 with SUA levels were stronger in non-drinkers.

CONCLUSION

Long-term PM₁, PM_2.5, and PM_1-2.5 exposures may increase the risk of hyperuricemia and elevate SUA levels among male traffic officers, especially in non-smokers and non-drinkers.

Heavy metal analysis in of indoor and outdoor dust extracts and cytotoxicity evaluation and inflammation factors on lung, gastric and skin cell lines

Dust particles (DPs) are one of the most important public health concerns in the urban environment. The presence of heavy metals (HMs) on the surface of DPs might increase the health risk of exposure to the DPs. Accordingly, The purpose of this study was to examine the content of HMs in the outdoor and indoor DPs in Neyshabur city and assess the cytotoxic effects of DPs exposure on lung, gastric, and skin cell lines. To this end, the city was divided into three areas, high-traffic, medium-traffic, and low-traffic (rural). The average concentration of the HMs in the indoor DPs were as follows, 655.5 μg g-1 for Zn, 114.6 μg g-1 for Cu, 77.7 μg g-1 for Cr, 108.6 μg g-1 for Ni, 52 μg g-1 for Pb, 12 μg g-1 for Co, and 3.3 μg g-1 for Cd, while the average concentration of Zn, Cu, Cr, Ni, Pb, Co, Cd in the outdoor DPs were 293.7 μg g-1, 200.6 μg g-1, 100.7 μg g-1, 68.4 μg g-1, 44.7 μg g-1, 18.6 μg g-1, 0.25 μg g-1, respectively. A higher concentration of HMs, as well as cytotoxicity, were revealed in the indoor samples compared to outdoor ones. The degree of cytotoxicity of DPs collected from high-traffic areas was higher than that of low and medium-traffic ones. In addition, treatment of AGS and L929 cells with indoor dust samples induced the expression level of inflammatory agents such as TNFα, IL6, and, CYP1A1 genes more than in outdoor dust samples (P < 0.05). Briefly, a higher level of HMs concentration and cytotoxicity effect on the given cell lines was observed in the samples taken from indoor environments and high-traffic areas.

Cytotoxicity of Particulate Matter PM10 Samples from Ouagadougou, Burkina Faso

Particulate matter (PM) is one of the main air pollutants with 257,000 deaths per year in Africa. Studying their toxic mechanisms of action could provide a better understanding of their effects on the population health. The objective of this study was to describe the PM₁₀ toxic mechanism of action collected in 3 districts of Ouagadougou. Once per month and per site between November 2015 and February 2016, PM₁₀ was sampled for 24 hours using the MiniVol TAS (AirMetrics, Eugene, USA). The collected filters were then stored in Petri dishes at room temperature for in vitro toxicological studies using human pulmonary artery endothelial cells (HPAEC) at the Bordeaux INSERM-U1045 Cardio-thoracic Research Center. The three study districts were classified based on PM₁₀ level (high, intermediate, and low, respectively, for districts 2, 3, and 4). PM₁₀ induced a concentration-dependent decrease in cell viability. A significant decrease in cell viability was observed at 1 µg/cm², 10 µg/cm², and 25 µg/cm² for, respectively, districts 2, 3, and 4. A significant increase in the production of reactive oxygen species (ROS) was observed at 10 µg/cm² for district 2 versus 5 µg/cm² and 1 µg/cm² for districts 3 and 4, respectively. Finally, a significant production of IL-6 was recorded from 5 µg/cm² for district 4 versus 10 µg/cm² for districts 2 and 3. Consequently, Ouagadougou is subjected to PM₁₀ pollution, which can induce a significant production of ROS and IL-6 to cause adverse effects on the health of the population.

Recent progress in research on PM2.5 in subways

Nowadays, PM2.5 concentrations greatly influence indoor air quality in subways and threaten passenger and staff health because PM2.5 not only contains heavy metal elements, but can also carry toxic and harmful substances due to its small size and large specific surface area. Exploring the physicochemical and distribution characteristics of PM2.5 in subways is necessary to limit its concentration and remove it. At present, there are numerous studies on PM2.5 in subways around the world, yet, there is no comprehensive and well-organized review available on this topic. This paper reviews the nearly twenty years of research and over 130 published studies on PM2.5 in subway stations, including aspects such as concentration levels and their influencing factors, physicochemical properties, sources, impacts on health, and mitigation measures. Although many determinants of station PM2.5 concentration have been reported in current studies, e.g., the season, outdoor environment, and station depth, their relative influence is uncertain. The sources of subway PM2.5 include those from the exterior (e.g., road traffic and fuel oil) and the interior (e.g., steel wheels and rails and metallic brake pads), but the proportion of these sources is also unknown. Control strategies of PM mainly include adequate ventilation and filtration, but these measures are often inefficient in removing PM2.5. The impacts of PM2.5 from subways on human health are still poorly understood. Further research should focus on long-term data collection, influencing factors, the mechanism of health impacts, and PM2.5 standards or regulations.

Influence of fine particulate matter and its pure particulate fractions on pulmonary immune cells and cytokines in mice

Particulate matter with a diameter ≤2.5 µm (PM^2.5) has a complex composition and has been associated with the incidence of cardiopulmonary disease and premature death in humans. However, whether pure particulate fractions of PM^2.5 (PPP^2.5), which are composed primarily of carbon, are responsible for the toxicity caused by ambient particulate matter (original PM^2.5 particles, OPP^2.5) is currently unclear. The present study assessed the acute toxic effects of OPP^2.5 sampled in Beijing, China and of its PPP^2.5 fraction in male BALB/c mice. The mice were intratracheally instilled with a single dose of aerosolized OPP^2.5 or PPP^2.5. Blood, lungs and bronchoalveolar lavage fluid were collected after 24 h for histopathology, flow cytometry and the measurement of pro-inflammatory cytokines/chemokines and other biochemical factors. Both OPP^2.5 and PPP^2.5 caused acute toxicity, particularly inflammatory responses, including an increase in the levels of pro-inflammatory cytokines and an accumulation of numerous immune cells in the lungs. OPP^2.5 induced a stronger inflammatory response than PPP^2.5. The complex components adsorbed into the solid core granules of OPP^2.5 and the granules themselves contributed to the toxic effects.

Oxidative Stress From Exposure to the Underground Space Environment

There are a growing number of people entering underground spaces. However, underground spaces have unique environmental characteristics, and little is known about their effects on human health. It is crucial to elucidate the effects of the underground space environment on the health of humans and other organisms. This paper reviews the effects of hypoxia, toxic atmospheric particles, and low background radiation in the underground space environment on living organisms from the perspective of oxidative stress. Most studies have revealed that living organisms maintained in underground space environments exhibit obvious oxidative stress, which manifests as changes in oxidants, antioxidant enzyme activity, genetic damage, and even disease status. However, there are few relevant studies, and the pathophysiological mechanisms have not been fully elucidated. There remains an urgent need to focus on the biological effects of other underground environmental factors on humans and other organisms as well as the underlying mechanisms. In addition, based on biological research, exploring means to protect humans and living organisms in underground environments is also essential.

Air quality intervention during the Nanjing youth olympic games altered PM sources, chemical composition, and toxicological responses

Ambient particulate matter (PM) is a leading global environmental health risk. Current air quality regulations are based on airborne mass concentration. However, PM from different sources have distinct chemical compositions and varied toxicity. Connections between emission control measures, air quality, PM composition, and toxicity remain insufficiently elucidated. The current study assessed the composition and toxicity of PM collected in Nanjing, China before, during, and after an air quality intervention for the 2014 Youth Olympic Games. A co-culture model that mimics the alveolar epithelium with the associated macrophages was created using A549 and THP-1 cells. These cells were exposed to size-segregated inhalable PM samples. The composition and toxicity of the PM samples were influenced by several factors including seasonal variation, emission sources, and the air quality intervention. For example, we observed a size-dependent shift in particle mass concentrations during the air quality intervention with an emphasized proportion of smaller particles (PM_2.5) present in the air. The roles of industrial and fuel combustion and traffic emissions were magnified during the emission control period. Our analyses revealed that the PM samples demonstrated differential cytotoxic potencies at equal mass concentrations between sampling periods, locations, and time of day, influenced by variations in the predominant emission sources. Coal combustion and industrial emissions were the most important sources affecting the toxicological responses and displayed the least variation in emission contributions between the sampling periods. In conclusion, emission control mitigated cytotoxicity and oxidative stress for particles larger than 0.2 μm, but there was inadequate evidence to determine if it was the key factor reducing the harmful effects of PM_0.2.

Environmental and Health Effects of Ventilation in Subway Stations: A Literature Review

Environmental health in subway stations, a typical type of urban underground space, is becoming increasingly important. Ventilation is the principal measure for optimizing the complex physical environment in a subway station. This paper narratively reviews the environmental and health effects of subway ventilation and discusses the relevant engineering, environmental, and medical aspects in combination. Ventilation exerts a notable dual effect on environmental health in a subway station. On the one hand, ventilation controls temperature, humidity, and indoor air quality to ensure human comfort and health. On the other hand, ventilation also carries the potential risks of spreading air pollutants or fire smoke through the complex wind environment as well as produces continuous noise. Assessment and management of health risks associated with subway ventilation is essential to attain a healthy subway environment. This, however, requires exposure, threshold data, and thereby necessitates more research into long-term effects, and toxicity as well as epidemiological studies. Additionally, more research is needed to further examine the design and maintenance of ventilation systems. An understanding of the pathogenic mechanisms and aerodynamic characteristics of various pollutants can help formulate ventilation strategies to reduce pollutant concentrations. Moreover, current comprehensive underground space development affords a possibility for creating flexible spaces that optimize ventilation efficiency, acoustic comfort, and space perception.

Evaluating deciduous tree leaves as biomonitors for ambient particulate matter pollution in Pittsburgh, PA, USA

Fine particulate matter (PM_2.5) air pollution varies spatially and temporally in concentration and composition and has been shown to cause or exacerbate adverse effects on human and ecological health. Biomonitoring using airborne tree leaf deposition as a proxy for particulate matter (PM) pollution has been explored using a variety of study designs, tree species, sampling strategies, and analytical methods. In the USA, relatively few have applied these methods using co-located fine particulate measurements for comparison and relying on one tree species with extensive spatial coverage, to capture spatial variation in ambient air pollution across an urban area. Here, we evaluate the utility of this approach, using a spatial saturation design and pairing tree leaf samples with filter-based PM_2.5 across Pittsburgh, Pennsylvania, with the goal of distinguishing mobile and stationary sources using PM_2.5 composition. Co-located filter and leaf-based measurements revealed some significant associations with traffic and roadway proximity indicators. We compared filter and leaf samples with differing protection from the elements (e.g., meteorology) and PM collection time, which may account for some variance in PM source and/or particle size capture between samples. To our knowledge, this study is among the first to use deciduous tree leaves from a single tree species as biomonitors for urban PM_2.5 pollution in the northeastern USA.

Review of PM Oxidative Potential Measured with Acellular Assays in Urban and Rural Sites across Italy

This work is an overview of the oxidative potential (OP) values up to date measured in Italy, with the aim to provide a picture of the spatial and seasonal variability of OP in the various geographical areas across Italy. The summarized works used the common acellular assays-based dithiothreitol (OPDTT), ascorbic acid (OPAA), glutathione (OPGSH), and 2',7'-dichlorodfluorescein (OPDCFH) assays. The paper describes the association of OP responses with PM chemical composition, the sensitivity of various acellular OP assays to PM components and emission sources, and PM size distribution of the measured OP values. Our synthesis indicates that crustal and transition metals (e.g., Fe, Ni, Cu, Cr, Mn, Zn, and V), secondary ions and carbonaceous components (elemental carbon, EC, organic carbon, OC and water soluble carbon, WSOC) show significant correlations with OP across different urban and rural areas and size ranges. These chemical species are mainly associated with various PM sources, including residual/fuel oil combustion, traffic emissions, and secondary organic aerosol formation. Although the OP assays are sensitive to the same redox-active species, they differ in the association with PM chemical components. The DDT assay is mainly sensitive to the organic compounds that are mostly accumulated in the fine PM fraction, i.e., tracers of burning sources, and redox active organics associated with other markers of photochemical aging. In contrast, OPAA and OPGSH were mostly responsive to metals, mainly those related to non-exhaust traffic emissions (Cu, Zn, Cr, Fe, Ni, Mn, Sn, Cd, Pb), that are mainly accumulated in the coarse PM. Among the investigated sites, our synthesis shows larger OP values in Trentino region and the Po Valley, that may be explained by the high density of anthropogenic sources, and the orographic and meteorological characteristics, that favor the pollutants accumulation and aerosol photo-oxidative aging.

Health effects of particulate matter air pollution in underground railway systems - a critical review of the evidence

BACKGROUND

Exposure to ambient airborne particulate matter is a major risk factor for mortality and morbidity, associated with asthma, lung cancer, heart disease, myocardial infarction, and stroke, and more recently type 2 diabetes, dementia and loss of cognitive function. Less is understood about differential effects of particulate matter from different sources. Underground railways are used by millions of people on a daily basis in many cities. Poor air exchange with the outside environment means that underground railways often have an unusually high concentration of airborne particulate matter, while a high degree of railway-associated mechanical activity produces particulate matter which is physicochemically highly distinct from ambient particulate matter. The implications of this for the health of exposed commuters and employees is unclear.

MAIN BODY

A literature search found 27 publications directly assessing the potential health effects of underground particulate matter, including in vivo exposure studies, in vitro toxicology studies, and studies of particulate matter which might be similar to that found in underground railways. The methodology, findings, and conclusions of these studies were reviewed in depth, along with further publications directly relevant to the initial search results. In vitro studies suggest that underground particulate matter may be more toxic than exposure to ambient/urban particulate matter, especially in terms of endpoints related to reactive oxygen species generation and oxidative stress. This appears to be predominantly a result of the metal-rich nature of underground particulate matter, which is suggestive of increased health risks. However, while there are measureable effects on a variety of endpoints following exposure in vivo, there is a lack of evidence for these effects being clinically significant as may be implied by the in vitro evidence.

CONCLUSION

There is little direct evidence that underground railway particulate matter exposure is more harmful than ambient particulate matter exposure. This may be due to disparities between in vivo exposures and in vitro models, and differences in exposure doses, as well as statistical under powering of in vivo studies of chronic exposure. Future research should focus on outcomes of chronic in vivo exposure, as well as further work to understand mechanisms and potential biomarkers of exposure.

Aerosol sources in subway environments

Millions of people use rail subway public transport around the world, despite the relatively high particulate matter (PM) concentrations in these underground environments, requiring the identification and quantification of the aerosol source contributions to improve the air quality. An extensive aerosol monitoring campaign was carried out in eleven subway stations in the Barcelona metro system, belonging to seven subway lines. PM_2.5 samples were collected during the metro operating hours and chemically analysed to determine major and trace elements, inorganic ions, and total carbon. The chemical compositions of subway components such as brake pads, rail tracks and pantographs were also determined. The mean PM_2.5 concentrations varied widely among stations, ranging from 26 µg m^-3 to 86 µg m^-3. Subway PM_2.5 was mainly constituted by Fe₂O₃ (30-66%), followed by carbonaceous matter (18-37%) for the old stations, while for new stations equipped with Platform Screen Doors (PSD) these percentages go down to 21-44% and 15-30%, respectively. Both the absolute concentrations and the relative abundance of key species differed for each subway station, although with common patterns within a given subway line. This is a result of the different emission chemical profiles in different subway lines (using diverse types of brakes and/or pantographs). The co-emission of different sources poses a problem for their separation by receptor models. Nevertheless, receptor modelling (Positive Matrix Factorization) was applied resulting in ten sources, five of them subway-specific: RailWheel, RailWheel+Brake, Brake_A, Brake_B, Pb. The sum of their contributions accounted for 43-91% of bulk PM_2.5 for the old stations and 21-52% for the stations with PSD. The decrease of the activity during the weekends resulted in a decrease (up to 56%) in the subway-specific sources contribution to the -already lower- bulk PM_2.5 concentrations compared to weekdays. The health-related elements are mainly apportioned (> 60%) by subway sources.

Factors affecting the exposure of passengers, service staff and train drivers inside trains to airborne particles

This study investigated train air conditioning filters, interior ventilation systems, tunnel environments and platform air quality as factors affecting the concentrations of airborne particles inside trains and provides information on the exposure of passengers, train drivers and service staff to particles. Particle sampling was done inside the passenger cabin, the driver cabin and the service staff cabin during on-board measurement campaigns in 2016 and 2017. The results show that interior ventilation plays a key role in maintaining cleaner in-train air. Noticeable increases in PM₁₀ and PM_2.5 levels were observed for all of the measured cabins when the train was running in the newly opened tunnel. The increases occurred when the doors of the passenger cabin and the service staff cabin were open at underground stations. The door to the driver cabin, which remained closed for the entire measurement period, acted as a filter for coarse particles (PM_2.5-10). The highest particle exposure occurred in the passenger cabin, followed by the service staff cabin, while the driver had the lowest exposure. The highest deposition dose occurs for the service staff and the lowest for commuters.

Exposure to Concentrated Ambient PM2.5 Shortens Lifespan and Induces Inflammation-Associated Signaling and Oxidative Stress in Drosophila

Exposure to ambient PM 2.5 is associated with human premature mortality. However, it has not yet been toxicologically replicated, likely due to the lack of suitable animal models. Drosophila is frequently used in longevity research due to many incomparable merits. The present study aims to validate Drosophila models for PM 2.5 toxicity study through characterizing their biological responses to exposure to concentrated ambient PM 2.5 (CAP). The survivorship curve demonstrated that exposure to CAP markedly reduced lifespan of Drosophila. This antilongevity effect of CAP exposure was observed in both male and female Drosophila, and by comparison, the male was more sensitive [50% survivals: 20 and 48 days, CAP- and filtered air (FA)-exposed males, respectively; 21 and 40 days, CAP- and FA-exposed females, respectively]. Similar to its putative pathogenesis in humans, CAP exposure-induced premature mortality in Drosophila was also coincided with activation of pro-inflammatory signaling pathways including Jak, Jnk, and Nf-κb and increased systemic oxidative stress. Furthermore, like in humans and mammals, exposure to CAP significantly increased whole-body and circulating glucose levels and increased mRNA expression of Ilp2 and Ilp5 , indicating that CAP exposure induces dysregulated insulin signaling in Drosophila. Similar to effects on humans exposure to CAP leads to premature mortality likely through induction of inflammation-associated signaling, oxidative stress, and metabolic abnormality in Drosophila, strongly supporting that it can be a useful model organism for PM 2.5 toxicity study.