Self-reported exposure to dust and diesel exhaust, respiratory symptoms, and use of respiratory protective equipment among Arctic miners.

Arctic miners face significant risks from diesel exhaust and dust exposure, potentially leading to adverse respiratory health. Employers must limit harmful exposures, using personal protective equipment (PPE) as a last line of defense. This study explored the association between reported respiratory exposure and symptoms, and PPE training and usage. Data from the MineHealth study (2012-2014) included a total of 453 Arctic open pit miners in Norway, Sweden, and Finland. Participants answered questions on exposure to dust and diesel exhaust, respiratory symptoms, and PPE use, in addition to age, gender, BMI, smoking, and self-rated health. Estimated exposure to dust was common, reported by 91%, 80%, and 82% and that of diesel exhaust by 84%, 43%, and 47% of workers in Sweden, Finland, and Norway, respectively. Reported dust exposure was significantly related to respiratory symptoms (OR 2.2, 95% CI 1.3-3.7), diesel exposure increased the occurrence of wheezing (OR 2.6, 95% CI 1.3-5.4). PPE use varied between the studied mines. Non-use was common and related to reduced visibility, wetness, skin irritation and fogging of the respiratory PPE. Future research should employ more precise exposure assessment, respiratory function as well as explore the reasons behind the non-compliance of PPE use.

Assessment of genotoxicity biomarkers in gasoline station attendants due to occupational exposure.

Gasoline station attendants are exposed to numerous chemicals that might have genotoxic and carcinogenic potential, such as benzene in fuel vapor and particulate matter and polycyclic aromatic hydrocarbons in vehicle exhaust emission. According to IARC, benzene and diesel particulates are Group 1 human carcinogens, and gasoline has been classified as Group 2A "possibly carcinogenic to humans." At gas stations, self-service is not implemented in Turkey; fuel-filling service is provided entirely by employees, and therefore they are exposed to those chemicals in the workplace during all working hours. Genetic monitoring of workers with occupational exposure to possible genotoxic agents allows early detection of cancer. We aimed to investigate the genotoxic damage due to exposures in gasoline station attendants in Turkey. Genotoxicity was evaluated by the Comet, chromosomal aberration, and cytokinesis-block micronucleus assays in peripheral blood lymphocytes. Gasoline station attendants (n = 53) had higher tail length, tail intensity, and tail moment values than controls (n = 61). In gasoline station attendants (n = 46), the frequencies of chromatid gaps, chromosome gaps, and total aberrations were higher compared with controls (n = 59). Increased frequencies of micronuclei and nucleoplasmic bridges were determined in gasoline station attendants (n = 47) compared with controls (n = 40). Factors such as age, duration of working, and smoking did not have any significant impact on genotoxic endpoints. Only exposure increased genotoxic damage in gasoline station attendants independently from demographic and clinical characteristics. Occupational exposure-related genotoxicity risk may increase in gasoline station attendants who are chronically exposed to gasoline and various chemicals in vehicle exhaust emissions.

Characteristics, source analysis, and health risk of PM2.5 in the urban tunnel environment associated with E10 petrol usage.

The increase in the number of motor vehicles has intensified the impact of traffic sources on air quality. Our aim was to illustrate the characteristics of PM2.5 emissions from vehicles fueled with E10 (a blend of 10% ethanol and 90% gasoline). A 21-day PM2.5 sampling in a fully enclosed urban tunnel and the component analysis were completed, and the characteristics, sources, and health risks of tunnel PM2.5 were studied. Moreover, the PM2.5 pH and its sensitivity were investigated by the thermodynamic model (ISORROPIA-II). In addition, exposure models were used to assess the health risks of different heavy metals in PM2.5 to humans through respiratory pathways. The two-point Cu/Sb ratio (entrance: 4.0 ± 1.4; exit: 4.4 ± 1.7) was close to the diagnostic criteria indicating a significant impact from brake wear. NO3-, NH4+, and SO42- constituted the main components of water-soluble ions in PM2.5 of the tunnel, accounting for 83.0-84.6% of the total concentration of inorganic ions. The organic carbon/elemental carbon ratio of the tunnel was greater than 2, indicating that the contribution of gasoline vehicle exhaust was significant. The average emission factors of PM2.5 in the fleet was 31.4 ± 16.6 mg/(veh·km). The pH value of PM2.5 in a tunnel environment (4.6 ± 0.3) was more acidic than that in an urban environment (4.9 ± 0.6). The main sensitive factors of PM2.5 pH in the urban atmosphere and tunnel environment were total ammonia (sum of gas and aerosol, NH3) and temperature, respectively. The results of the health risk assessment showed that Pb posed a potential carcinogenic risk, while As and Cd presented unacceptable risks for tunnel workers. The non-carcinogenic risk index of heavy metals of PM2.5 in the tunnel environment exceeded the safety threshold.

Residential exposure to traffic pollution and mammographic density in premenopausal women.

BACKGROUND: Mammographic density (MD) is the most important breast cancer biomarker. Ambient pollution is a carcinogen, and its relationship with MD is unclear. This study aims to explore the association between exposure to traffic pollution and MD in premenopausal women. METHODOLOGY: This Spanish cross-sectional study involved 769 women attending gynecological examinations in Madrid. Annual Average Daily Traffic (AADT), extracted from 1944 measurement road points provided by the City Council of Madrid, was weighted by distances (d) between road points and women's addresses to develop a Weighted Traffic Exposure Index (WTEI). Three methods were employed: method-1 (1dAADT), method-2 (1dAADT), and method-3 (e1dAADT). Multiple linear regression models, considering both log-transformed percentage of MD and untransformed MD, were used to estimate MD differences by WTEI quartiles, through two strategies: "exposed (exposure buffers between 50 and 200 m) vs. not exposed (>200 m)"; and "degree of traffic exposure". RESULTS: Results showed no association between MD and traffic pollution according to buffers of exposure to the WTEI (first strategy) for the three methods. The highest reductions in MD, although not statistically significant, were detected in the quartile with the highest traffic exposure. For instance, method-3 revealed a suggestive inverse trend (eßQ1 = 1.23, eßQ2 = 0.96, eßQ3 = 0.85, eßQ4 = 0.85, p-trend = 0.099) in the case of 75 m buffer. Similar non-statistically significant trends were observed with Methods-1 and -2. When we examined the effect of traffic exposure considering all the 1944 measurement road points in every participant (second strategy), results showed no association for any of the three methods. A slightly decreased MD, although not significant, was observed only in the quartile with the highest traffic exposure: eßQ4 = 0.98 (method-1), and eßQ4 = 0.95 (methods-2 and -3). CONCLUSIONS: Our results showed no association between exposure to traffic pollution and MD in premenopausal women. Further research is needed to validate these findings.

Assessing emission-driven changes in health risk of source-specific PM2.5-bound heavy metals by adjusting meteorological covariates.

Heavy metals (HMs) in PM2.5 gain much attention for their toxicity and carcinogenic risk. This study evaluates the health risks of PM2.5-bound HMs, focusing on how meteorological conditions affect these risks against the backdrop of PM2.5 reduction trends in China. By applying a receptor model with a meteorological normalization technique, followed by health risk assessment, this work reveals emission-driven changes in health risk of source-specific HMs in the outskirt of Tianjin during the implementation of China' second Clean Air Action (2018-2020). Sources of PM2.5-bound HMs were identified, with significant contributions from vehicular emissions (on average, 33.4 %), coal combustion (26.3 %), biomass burning (14.1 %), dust (11.7 %), industrial boilers (9.7 %), and shipping emission and sea salt (4.7 %). The source-specific emission-driven health risk can be enlarged or dwarfed by the changing meteorological conditions over time, demonstrating that the actual risks from these source emissions for a given time period may be higher or smaller than those estimated by traditional assessments. Meteorology contributed on average 56.1 % to the interannual changes in source-specific carcinogenic risk of HMs from 2018 to 2019, and 5.6 % from 2019 to 2020. For the source-specific noncarcinogenic risk changes, the contributions were 38.3 % and 46.4 % for the respective periods. Meteorology exerts a more profound impact on daily risk (short-term trends) than on annual risk (long-term trends). Such meteorological impacts differ among emission sources in both sign and magnitude. Reduced health risks of HMs were largely from targeted regulatory measures on sources. Therefore, the meteorological covariates should be considered to better evaluate the health benefits attributable to pollution control measures in health risk assessment frameworks.

High spatial-resolved source-specific exposure and risk in the city scale: Influence of spatial interrelationship between PM2.5 sources and population on exposure.

Research on High Spatial-Resolved Source-Specific Exposure and Risk (HSRSSER) was conducted based on multiple-year, multiple-site synchronous measurement of PM2.5-bound (particulate matter with aerodynamic diameter<2.5 µm) toxic components in a Chinese megacity. The developed HSRSSER model combined the Positive Matrix Factorization (PMF) and Land Use Regression (LUR) to predict high spatial-resolved source contributions, and estimated the source-specific exposure and risk by personal activity time- and population-weighting. A total of 287 PM2.5 samples were collected at ten sites in 2018-2020, and toxic species including heavy metals (HMs), polycyclic aromatic hydrocarbons (PAHs) and organophosphate esters (OPEs) were analyzed. The percentage non-cancer risk were in the order of traffic emission (48 %) > industrial emission (22 %) > coal combustion (12 %) > waste incineration (11 %) > resuspend dust (7 %) > OPE-related products (0 %) ≈ secondary particles (0 %). Similar orders were observed in cancer risk. For traffic emission, due to its higher source contributions and large population in central area, non-cancer and cancer risk fraction increased from 23 % to 48 % and 20 % to 46 % after exposure estimation; while for industrial emission, higher source contributions but small population in suburb area decreased the percentage non-cancer and cancer risk from 38 % to 22 % and 39 % to 24 %, respectively.

Long-term trends of black carbon and particle number concentrations and their vehicle emission factors in Stockholm.

Black carbon (BC) and particle number (PN) concentrations are usually high in cities due to traffic emissions. European mitigation policies, including Euro emission standards, have been implemented to curb these emissions. We analyzed BC and PN (particle diameter Dp > 4 nm) concentrations in Stockholm spanning the years 2013-2019 (BC) and 2009-2019 (PN) measured at street canyon and rooftop sites to assess the effectiveness of the implemented policies. Combining these data with inverse dispersion modeling, we estimated BC and PN emission factors (EFBC and EFPN) for the mixed fleet, reflecting real-world driving conditions. The pollutants showed decreasing trends at both sites, but PN concentrations remained high at the canyon site considering the World Health Organization (WHO) recommendations. BC concentrations declined more rapidly than PN concentrations, showing a -9.4% and -4.9% annual decrease at the canyon and -7.2% and -0.5% at the rooftop site in the years 2013-2019. The EFBC and EFPN trends showed that the mitigation strategies for reducing particulate emissions for on-road vehicles were successful over the study period. However, the introduction of biofuels in the vehicle fleet -ethanol and later rapeseed methyl ester (RME)- increased the concentrations of particles with Dp < 10 nm before the adoption of particulate filters in the exhausts. Stricter Euro emission regulations, especially with diesel particulate filters (DPF) in Euro 5, 6, and VI vehicles, led to 66% decrease in EFBC and 55% in EFPN. Real-world EFBC surpassed HBEFA (Handbook Emission Factors for Road Transport) database values by 2.4-4.8 times; however, direct comparisons between real-world and HBEFA EFPN are difficult due to differences in lower cut-off sizes and measurement techniques. Our results underscore the necessity for revising the HBEFA database, updating laboratory testing methods and portable emission measuring systems (PEMS) measurements to account for liquid condensate contributions to PN measurements.

Lichen biomonitoring to assess spatial variability, potential sources and human health risks of polycyclic aromatic hydrocarbons (PAHs) and airborne metal concentrations in Manchester (UK).

Airborne metals and organic pollutants are linked to severe human health impacts, i.e. affecting the nervous system and being associated with cancer. Airborne metals and polycyclic aromatic hydrocarbons (PAHs) in urban environments are derived from diverse sources, including combustion and industrial and vehicular emissions, posing a threat to air quality and subsequently human health. A lichen biomonitoring approach was used to assess spatial variability of airborne metals and PAHs, identify potential pollution sources and assess human health risks across the City of Manchester (UK). Metal concentrations recorded in lichen samples were highest within the city centre area and along the major road network, and lichen PAH profiles were dominated by 4-ring PAHs (189.82 ng g-1 in Xanthoria parietina), with 5- and 6-ring PAHs also contributing to the overall PAH profile. Cluster analysis and pollution index factor (PIF) calculations for lichen-derived metal concentrations suggested deteriorated air quality being primarily linked to vehicular emissions. Comparably, PAH diagnostic ratios identified vehicular sources as a primary cause of PAH pollution across Manchester. However, local more complex sources (e.g. industrial emissions) were further identified. Human health risk assessment found a "moderate" risk for adults and children by airborne potential harmful element (PHEs) concentrations, whereas PAH exposure in Manchester is potentially linked to 1455 (ILCR = 1.45 × 10-3) cancer cases (in 1,000,000). Findings of this study indicate that an easy-to-use lichen biomonitoring approach can aid to identify hotspots of impaired air quality and potential human health impacts by airborne metals and PAHs across an urban environment, particularly at locations that are not continuously covered by (non-)automated air quality measurement programmes.

Evaluation of neural reflex activation as a potential mode of action for respiratory and cardiovascular effects of fine particulate matter.

OBJECTIVES: Mortality from respiratory and cardiovascular health conditions contributes largely to the total mortality that has been associated with exposure to PM2.5 in epidemiology studies. A mode of action (MoA) for these underlying morbidities has not been established, but it has been proposed that some effects of PM2.5 occur through activation of neural reflexes. MATERIALS AND METHODS: We critically reviewed the experimental studies of PM2.5 (including ambient PM2.5, diesel exhaust particles, concentrated ambient particles, diesel exhaust, and cigarette smoke) and neural reflex activation, and applied the principles of the International Programme on Chemical Safety (IPCS) MoA/human relevance framework to assess whether they support a biologically plausible and human-relevant MoA by which PM2.5 could contribute to cardiovascular and respiratory causes of death. We also considered whether the evidence from these studies supports a non-threshold MoA that operates at low, human-relevant PM2.5 exposure concentrations. RESULTS AND DISCUSSION: We found that the proposed MoA of neural reflex activation is biologically plausible for PM2.5-induced respiratory effects at high exposure levels used in experimental studies, but further studies are needed to fill important data gaps regarding the relevance of this MoA to humans at lower PM2.5 exposure levels. A role for the proposed MoA in PM2.5-induced cardiovascular effects is plausible for some effects but not others. CONCLUSIONS: Further studies are needed to determine whether neural reflex activation is the MoA by which PM2.5 could cause either respiratory or cardiovascular morbidities in humans, particularly at the ambient concentrations associated with total mortality in epidemiology studies.

Electrification of Transit Buses in the United States Reduces Greenhouse Gas Emissions.

The transportation sector is the largest emitter of greenhouse gas emissions (GHGs) in the United States. Increased use of public transit and electrification of public transit could help reduce these emissions. The electrification of public transit systems could also reduce air pollutant emissions in densely populated areas, where air pollution disproportionally burdens vulnerable communities with high health impacts and associated social costs. We analyze the life cycle emissions of transit buses powered by electricity, diesel, gasoline, and compressed natural gas and model GHGs and air pollutants mitigated for a transition to a fully electric U.S. public transit bus fleet using transit agency-level data. The electrification of the U.S. bus fleet would reduce several conventional air pollutants and has the potential to reduce transit bus GHGs by 33-65% within the next 14 years depending on how quickly the transition is made and how quickly the electricity grid decarbonizes. A levelized cost of driving analysis shows that with falling capital costs and an increase in annual passenger-kilometers of battery electric buses, the technology could reach levelized cost parity with diesel buses when electric bus capital costs fall below about $670 000 per bus.

Formaldehyde Exposure Racial Disparities in Southeast Texas.

Formaldehyde (HCHO) exposures during a full year were calculated for different race/ethnicity groups living in Southeast Texas using a chemical transport model tagged to track nine emission categories. Petroleum and industrial emissions were the largest anthropogenic sources of HCHO exposure in Southeast Texas, accounting for 44% of the total HCHO population exposure. Approximately 50% of the HCHO exposures associated with petroleum and industrial sources were directly emitted (primary), while the other 50% formed in the atmosphere (secondary) from precursor emissions of reactive compounds such as ethylene and propylene. Biogenic emissions also formed secondary HCHO that accounted for 11% of the total population-weighted exposure across the study domain. Off-road equipment contributed 3.7% to total population-weighted exposure in Houston, while natural gas combustion contributed 5% in Beaumont. Mobile sources accounted for 3.7% of the total HCHO population exposure, with less than 10% secondary contribution. Exposure disparity patterns changed with the location. Hispanic and Latino residents were exposed to HCHO concentrations +1.75% above average in Houston due to petroleum and industrial sources and natural gas sources. Black and African American residents in Beaumont were exposed to HCHO concentrations +7% above average due to petroleum and industrial sources, off-road equipment, and food cooking. Asian residents in Beaumont were exposed to HCHO concentrations that were +2.5% above average due to HCHO associated with petroleum and industrial sources, off-road vehicles, and food cooking. White residents were exposed to below average HCHO concentrations in all domains because their homes were located further from primary HCHO emission sources. Given the unique features of the exposure disparities in each region, tailored solutions should be developed by local stakeholders. Potential options to consider in the development of those solutions include modifying processes to reduce emissions, installing control equipment to capture emissions, or increasing the distance between industrial sources and residential neighborhoods.

Diesel exhaust and respiratory dust exposure in miners and chronic obstructive pulmonary disease (COPD) mortality in DEMS II.

BACKGROUND: Diesel exhaust and respirable dust exposures in the mining industry have not been studied in depth with respect to non-malignant respiratory disease including chronic obstructive pulmonary disease (COPD), with most available evidence coming from other settings. OBJECTIVES: To assess the relationship between occupational diesel exhaust and respirable dust exposures and COPD mortality, while addressing issues of survivor bias in exposed miners. METHODS: The study population consisted of 11,817 male workers from the Diesel Exhaust in Miners Study II, followed from 1947 to 2015, with 279 observed COPD deaths. We fit Cox proportional hazards models for the relationship between respirable elemental carbon (REC) and respirable dust (RD) exposure and COPD mortality. To address healthy worker survivor bias, we leveraged the parametric g-formula to assess effects of hypothetical interventions on both exposures. RESULTS: Cox models yielded elevated estimates for the associations between average intensity of REC and RD and COPD mortality, with hazard ratios (HR) corresponding to an interquartile range width increase in exposure of 1.46 (95 % confidence interval (CI): 1.12, 1.91) and 1.20 (95 % CI: 0.96, 1.49), respectively for each exposure. HRs for cumulative exposures were negative for both REC and RD. Based on results from the parametric g-formula, the risk ratio (RR) for COPD mortality comparing risk under an intervention eliminating REC to the observed risk was 0.85 (95 % CI: 0.55, 1.06), equivalent to an attributable risk of 15 %. The corresponding RR comparing risk under an intervention eliminating RD to the observed risk was 0.93 (95 % CI: 0.56, 1.31). CONCLUSIONS: Our findings, based on data from a cohort of nonmetal miners, are suggestive of an increased risk of COPD mortality associated with REC and RD, as well as evidence of survivor bias in this population leading to negative associations between cumulative exposures and COPD mortality in traditional regression analysis.

Fine particle trace elements at a mountain site in southern China: Source identification, transport, and health risks.

Trace elements in atmospheric particulate matter play a significant role in air quality, human health, and biogeochemical cycles. In this study, the trace elements (Ca, Al, K, Fe, Na, Mg, Zn, Pb, Mn, Ti, Cu, Cr, Sr, Ni) in PM2.5 samples collected at the summit of Mt. Lushan were analyzed to quantify their abundance, source, transport, and health risks. During the whole sampling period, the major trace elements was Ca, Al, and K. While the trace metals with the lowest concentrations were Sr, Ni, Rb, and Cd. The trace elements were influenced by air mass transport routes, exhibiting an increasing trend of crustal elements in the northwesterly airmass and anthropogenic elements (Zn, Mn, Cu, and Ni) in the easterly air masses. Construction dust, coal + biomass burning, vehicle emission, urban nitrate-rich + urban waste incineration emissions, and soil dust + industry emissions were common sources of PM2.5 on Mt. Lushan. Different air mass transport routes had various source contribution patterns. These results indicate that trace elements at Mt. Lushan are influenced by regional anthropogenic emissions and monsoon-dominated trace element transport. The total resulting cancer risk value that these elements posed were below the acceptable risk value of 1 × 10-6, while the non-carcinogenic risk value (1.72) was higher than the safety level, suggesting that non-carcinogenic effects due to these trace elements inhalation were likely to occur. Vehicle emission and coal + biomass burning were the common dominant sources of non-cancer risks posed by trace elements at Mt. Lushan.

Corelease of Genotoxic Polycyclic Aromatic Hydrocarbons and Nanoparticles from a Commercial Aircraft Jet Engine - Dependence on Fuel and Thrust.

Jet engines are important contributors to global CO2 emissions and release enormous numbers of ultrafine particles into different layers of the atmosphere. As a result, aviation emissions are affecting atmospheric chemistry and promote contrail and cloud formation with impacts on earth's radiative balance and climate. Furthermore, the corelease of nanoparticles together with carcinogenic polycyclic aromatic hydrocarbons (PAHs) affects air quality at airports. We studied exhausts of a widely used turbofan engine (CFM56-7B26) operated at five static thrust levels (idle, 7, 30, 65, and 85%) with conventional Jet A-1 fuel and a biofuel blend composed of hydro-processed esters and fatty acids (HEFA). The particles released, the chemical composition of condensable material, and the genotoxic potential of these exhausts were studied. At ground operation, particle number emissions of 3.5 and 0.5 × 1014 particles/kg fuel were observed with highest genotoxic potentials of 41300 and 8800 ng toxicity equivalents (TEQ)/kg fuel at idle and 7% thrust, respectively. Blending jet fuel with HEFA lowered PAH and particle emissions by 7-34% and 65-67% at idle and 7% thrust, respectively, indicating that the use of paraffin-rich biofuels is an effective measure to reduce the exposure of airport personnel to nanoparticles coated with genotoxic PAHs (Trojan horse effect).

Dose-response-relationship between occupational exposure to diesel engine emissions and lung cancer risk: A systematic review and meta-analysis.

BACKGROUND: In 2012, the International Agency for Research on Cancer (IARC) concluded that diesel engine emissions (DEE) emissions cause cancer in humans. However, there is still controversy surrounding this conclusion, due to several studies since the IARC decision citing a lack of evidence of a dose-response relationship. OBJECTIVES: Through a systematic review, we aimed to evaluate all evidence on the association between occupational DEE and lung cancer to investigate whether there is an increased risk of lung cancer for workers exposed to DEE and if so, to describe the dose-response relationship. METHODS: We registered the review protocol with PROSPERO and searched for observational studies in relevant literature databases. Two independent reviewers screened the studies' titles/abstracts and full texts, and extracted and assessed their quality. Studies with no direct DEE measurement but with information on length of exposure for high-risk occupations were assigned exposure values based on the DEE Job-Exposure-Matrix (DEE-JEM). After assessing quality and informativeness, we selected appropriate studies for the dose-response meta-analysis. RESULTS: Sixty-five reports (from thirty-seven studies) were included in the review; one had a low risk of bias (RoB) (RR per 10 µg/m3-years: 1.014 [95%CI 1.007-1.021]). There was an increased, statistically significant risk of lung cancer with increasing DEE exposure for all studies (RR per 10 µg/m3-years = 1.013 [95%CI 1.004-1.021]) as well as for studies with a low RoB in the exposure category (RR per 10 µg/m3-years = 1.008 [95% CI1.001-1.015]). We obtained a doubling dose of 555 µg/m3-years for all studies and 880 µg/m3-years for studies with high quality in the exposure assessment. DISCUSSION: We found a linear positive dose-response relationship for studies with high quality in the exposure domain, even though all studies had an overall high risk of bias. Current threshold levels for DEE exposure at the workplace should be reconsidered.

Source apportionment of suspended particulate matter (PM1, PM2.5 and PM10) collected in road and tram tunnels in Krakow, Poland.

Here, we present the results of a comprehensive study of air quality in two tunnels located in the city of Krakow, southern Poland. The study comprised three PM fractions of suspended particulate matter (PM1, PM2.5 and PM10) sampled during campaigns lasting from March 14 to April 24, 2016 and from June 28 to July 18, 2016, in the road tunnel and the tram tunnel, respectively. The collected samples had undergone comprehensive chemical, elemental and carbon isotope analyses. The results of these analyses gave the basis for better characterization of urban transport as a source of air pollution in the city. The concentrations of particulate matter varied, depending on the analysed PM fraction and the place of sampling. For the tram tunnel, the average concentrations were 53.2 µg·m-3 (PM1), 73.8 µg·m-3 (PM2.5), 96.5 µg·m-3 (PM10), to be compared with 44.2 µg·m-3, 137.7 µg·m-3, 221.5 µg·m-3, respectively, recorded in the road tunnel. The isotope-mass balance calculations carried out separately for the road and tram tunnel and for each PM fraction, revealed that 60 to 79% of carbon present in the samples collected in the road tunnel was associated with road transport, to be compared with 15-33% obtained in the tram tunnel. The second in importance were biogenic emissions (17-21% and 41-49% in the road and tram tunnel, respectively. Sixteen different polycyclic aromatic hydrocarbons (PAHs) have been identified in the analysed samples. As expected, much higher concentrations of PAHs were detected in the road tunnel when compared to the tram tunnel. Based on the analysed PAHs concentrations, health risk assessment was determined using 3 different types of indicators: carcinogenic equivalent (CEQ), mutagenic equivalent (MEQ) and toxic equivalent (TEQ).

Effect of gas temperature on carbon soot oxidation via non-thermal plasma: two-dimensional numerical study integrating reactive flow and discharge models.

Non-thermal plasma (NTP) efficiently regenerates diesel particulate filters by oxidizing carbon soot (CS) at low temperatures. However, numerical studies on the spatial characteristics of CS oxidation by NTP are scarce. In addition, the influence of background gas heating on the CS-oxidizing performance by NTP remains inadequately understood. This research investigates the impact of gas temperature (323-573 K) on heterogeneous CS oxidation using NTP in a two-dimensional configuration. The results indicate that CS is mainly oxidized by [Formula: see text], [Formula: see text], and [Formula: see text] during NTP treatment. The energy efficiency of CS removal by NTP ranges from 0.1 to 2.6 g kWh-1 for varying gas temperature and applied voltage, consistent with previous research. Higher gas temperatures enhance both CS removal rate and efficiency, whereas higher applied voltages enhance rate at the expense of efficiency. The study also assesses energy conversion efficiency from electrical power input to chemical bonding energy during CS oxidation by NTP, yielding 0.03 to 0.23% efficiency for the considered gas temperature and voltage ranges, with higher temperatures leading to better efficiency.

Concentration-dependent alterations in the human plasma proteome following controlled exposure to diesel exhaust.

Traffic-related air pollution (TRAP) exposure is associated with systemic health effects, which can be studied using blood-based markers. Although we have previously shown that high TRAP concentrations alter the plasma proteome, the concentration-response relationship between blood proteins and TRAP is unexplored in controlled human exposure studies. We aimed to identify concentration-dependent plasma markers of diesel exhaust (DE), a model of TRAP. Fifteen healthy non-smokers were enrolled into a double-blinded, crossover study where they were exposed to filtered air (FA) and DE at 20, 50 and 150 µg/m3 PM2.5 for 4h, separated by ≥ 4-week washouts. We collected blood at 24h post-exposure and used label-free mass spectrometry to quantify proteins in plasma. Proteins exhibiting a concentration-response, as determined by linear mixed effects models (LMEMs), were assessed for pathway enrichment using WebGestalt. Top candidates, identified by sparse partial least squares discriminant analysis and LMEMs, were confirmed using enzyme-linked immunoassays. Thereafter, we assessed correlations between proteins that showed a DE concentration-response and acute inflammatory endpoints, forced expiratory volume in 1 s (FEV1) and methacholine provocation concentration causing a 20% drop in FEV1 (PC20). DE exposure was associated with concentration-dependent alterations in 45 proteins, which were enriched in complement pathways. Of the 9 proteins selected for confirmatory immunoassays, based on complementary bioinformatic approaches to narrow targets and availability of high-quality assays, complement factor I (CFI) exhibited a significant concentration-dependent decrease (-0.02 µg/mL per µg/m3 of PM2.5, p = 0.04). Comparing to FA at discrete concentrations, CFI trended downward at 50 (-2.14 ± 1.18, p = 0.08) and significantly decreased at 150 µg/m3 PM2.5 (-2.93 ± 1.18, p = 0.02). CFI levels were correlated with FEV1, PC20 and nasal interleukin (IL)-6 and IL-1ß. This study details concentration-dependent alterations in the plasma proteome following DE exposure at concentrations relevant to occupational and community settings. CFI shows a robust concentration-response and association with established measures of airway function and inflammation.

Critical review on the formations and exposure of polycyclic aromatic hydrocarbons (PAHs) in the conventional hydrocarbon-based fuels: Prevention and control strategies.

Polycyclic aromatic hydrocarbons (PAHs) are widely present in the atmosphere and primarily originate from the incomplete burning of fossil fuels and biofuels. Exposure to PAHs leads to harmful effects on human health and the environment. Diesel engines are a major source of PAH production in the transportation sector. Various approaches have been employed to reduce PAH emissions from diesel engines, including the use of biodiesel, green gaseous fuels, exhaust gas recirculation, exhaust after-treatment, and genetically modifying biodiesel with nanoparticles. This review focuses on PAH emissions from different generations of fuels and examines the remedial control actions taken to mitigate PAH formation. The study underscores the necessity for effective regulation of emissions from diesel engines, especially in developing countries where the reliance on fossil fuels is significant. Biodiesel has shown promise in reducing PAHs and carcinogenic pollutants, with higher biodiesel concentrations resulting in lower PAH formation. Replacing diesel with biodiesel and optimizing engine operating conditions are feasible methods to reduce PAH levels in the atmosphere. The use of nanoparticles in fuel blends and higher oxygen content in combustion chambers are also considered potential strategies for pollutant reduction. Additionally, the utilization of hydrogen and ammonia as secondary fuels has been explored as promising alternatives to fossil fuels. The study highlights the importance of further research on the presence of residual PAHs in the atmosphere and the implementation of strategies to curtail vehicular emissions.

A comprehensive exploration of characteristics and source attribution of carbonaceous aerosols in PM2.5 in an East China megacity.

A total of 84 PM2.5 (fine particulate matter) aerosol samples were collected between October 2020 and August 2021 within an urban site in Hangzhou, an East China megacity. Chemical species, such as organic carbon (OC), elemental carbon (EC), as well as char, soot, and n-alkanes, were analyzed to determine their pollution characteristics and source contributions. The mean yearly concentrations of OC, EC, char, soot, and total n-alkanes (∑n-alkane) were 8.76 ± 3.61 µg/m3, 1.44 ± 0.76 µg/m3, 1.21 ± 0.69 µg/m3, 0.3 ± 0.1 µg/m3, and 24.2 ± 10.6 ng/m3. The OC, EC, and ∑n-alkanes were found in the highest levels during winter and lowest during summer. There were strong correlations between OC and EC in both winter and spring, suggesting similar potential sources for these carbonaceous components in both seasons. There were poor correlations among the target pollutants due to summertime secondary organic carbon formation. Potential source contribution functions analysis showed that local pollution levels in winter and autumn were likely influenced by long-range transportation from the Plain of North China. Source index and positive matrix factorization models provided insights into the complex sources of n-alkanes in Hangzhou. Their major contributors were identified as terrestrial plant releases (32.7%), traffic emissions (28.8%), coal combustion (27.3%), and microbial activity (11.2%). Thus, controlling vehicular emissions and coal burning could be key measures to alleviate n-alkane concentrations in the atmosphere of Hangzhou, as well as other Chinese urban centers.