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Eicosanoids are potent regulators of homeostasis and inflammation. Co-exposure to allergen and diesel exhaust (DE) have been shown to lead to eosinophilic inflammation, impaired airflow, and increased airway responsiveness. It is not clear whether eicosanoids mediate the mechanism by which these exposures impair lung function. We conducted a randomized, double-blinded, and four-arm crossover study. Fourteen allergen-sensitized participants were exposed to four conditions: negative control; allergen-alone exposure; DE and allergen coexposure; coexposure with particle-reducing technology applied. Quantitative metabolic profiling of urinary eicosanoids was performed using LC-MS/MS. As expected, allergen inhalation increased eicosanoids. The prostacyclin metabolite 2,3-dinor-6-keto-PGF 1α (PGF 1α , prostaglandin F 1α ) increased with coexposure, but particle depletion suppressed this pathway. Individuals with a high genetic risk score demonstrated a greater increase in isoprostane metabolites following coexposure. Causal mediation analyses showed that allergen induced airflow impairment was mediated via leukotriene E 4 and tetranor-prostaglandin D metabolite. Overall, DE exposure did not augment the allergen's effect on urinary eicosanoids, except insofar as variant genotypes conferred susceptibility to the addition of DE in terms of isoprostane metabolites. These findings will add to the body of previous controlled human exposure studies and provide greater insight into how complex environmental exposures in urban air may influence individuals with sensitivity to aeroallergens.

22 alkylated polycyclic aromatic hydrocarbons (alk-PAHs) were characterized in ambient air individually for the first time in urban and semi-urban locations in Toronto, Canada. Five unsubstituted PAHs were included for comparison. Results from the measurements were used to estimate benzo[ a ]pyrene equivalent toxicity (BaPeq) of individual compounds in order to investigate the significance of a single compound in contributing to the overall toxic equivalency (TEQ) of air mixtures. To determine which compounds merit further investigation, BaPeq values of individual compounds were compared to the measured BaP toxicity. Our results showed that both unsubstituted and alkylated PAHs were more abundant in the urban area (38 and 30%, respectively). Benzo[ a ]pyrene levels at the urban location exceeded Ontario's 24 h guideline (40% of the events), and on average, it was 5 times higher than that at the semi-urban area. Gas-phase two- and three-ring compounds contributed up to 39% (urban) and 76% (semi-urban) of the TEQ of all compounds analyzed. Some alk-PAHs such as 7,12-dimethylbenzo[ a ]anthracene had a huge impact on the toxicity of urban air, and its BaPeq was on average 8 times higher than that of BaP. We emphasize that the toxic impact of alkylated and gaseous PAHs, which is not routinely included in many air monitoring programs, is significant and should not be neglected.

Annual global satellite-based estimates of fine particulate matter (PM 2.5 ) are widely relied upon for air-quality assessment. Here, we develop and apply a methodology for monthly estimates and uncertainties during the period 1998-2019, which combines satellite retrievals of aerosol optical depth, chemical transport modeling, and ground-based measurements to allow for the characterization of seasonal and episodic exposure, as well as aid air-quality management. Many densely populated regions have their highest PM 2.5 concentrations in winter, exceeding summertime concentrations by factors of 1.5-3.0 over Eastern Europe, Western Europe, South Asia, and East Asia. In South Asia, in January, regional population-weighted monthly mean PM 2.5 concentrations exceed 90 μg/m 3 , with local concentrations of approximately 200 μg/m 3 for parts of the Indo-Gangetic Plain. In East Asia, monthly mean PM 2.5 concentrations have decreased over the period 2010-2019 by 1.6-2.6 μg/m 3 /year, with decreases beginning 2-3 years earlier in summer than in winter. We find evidence that global-monitored locations tend to be in cleaner regions than global mean PM 2.5 exposure, with large measurement gaps in the Global South. Uncertainty estimates exhibit regional consistency with observed differences between ground-based and satellite-derived PM 2.5 . The evaluation of uncertainty for agglomerated values indicates that hybrid PM 2.5 estimates provide precise regional-scale representation, with residual uncertainty inversely proportional to the sample size.

Tailings ponds in the oil sands (OS) region in Alberta, Canada, have been associated with fugitive emissions of volatile organic compounds (VOCs) and other pollutants to the atmosphere. However, the contribution of tailings ponds to the total fugitive emissions of VOCs from OS operations remains uncertain. To address this knowledge gap, a field study was conducted in the summer of 2017 at Suncor's Pond 2/3 to estimate emissions of a suite of pollutants including 68 VOCs using a combination of micrometeorological methods and measurements from a flux tower. The results indicate that in 2017, Pond 2/3 was an emission source of 3322 ± 727 tons of VOCs including alkanes, aromatics, and oxygenated and sulfur-containing organics. While the total VOC emissions were approximately a factor of 2 higher than those reported by Suncor, the individual VOC species emissions varied by up to a factor of 12. A chemical mass balance (CMB) receptor model was used to estimate the contribution of the tailings pond to VOC pollution events in a nearby First Nations and Metis community in Fort McKay. CMB results indicate that Suncor Pond 2/3 contributed up to 57% to the total mass of VOCs measured at Fort McKay, reinforcing the importance of accurate VOC emission estimation methods for tailings ponds.

Many countries have dedicated to the mitigation of air pollution in the past several decades. However, evidence of beneficial effects of air quality improvement on chronic kidney disease (CKD) remains limited. We thus investigated the effects of dynamic changes (including deterioration and improvement) in air quality on the incidence of CKD in a longitudinal study in Taiwan. During 2001-2016, this study recruited a total of 163,197 Taiwanese residents who received at least two standard physical examinations. The level of fine particle matter (PM 2.5 ) was estimated using a high-resolution (1 km 2 ) satellite-based spatio-temporal model. We defined changes of PM 2.5 concentrations (ΔPM 2.5 ) as the difference between the two-year average measurements during follow-up and during the immediately preceding visit. The time-dependent Cox regression model was adopted to evaluate the relationships between ΔPM 2.5 and the incidence of CKD after adjusting for a series of covariates. The concentrations of PM 2.5 in Taiwan peaked around 2004 and began to decrease since 2005. We observed an approximate linear concentration-response relationship of ΔPM 2.5 with CKD incidence. Every 5 μg/m 3 decrease in the ambient concentration of PM 2.5 was associated with a 25% reduced risk of CKD development [hazard ratio (HR): 0.75; 95% CI: 0.73, 0.78]. In conclusion, this study demonstrated that the improvement of PM 2.5 air quality might be associated with a lower risk of CKD development. Our findings indicate that reducing air pollution may effectively prevent the development of CKD.

An "event-based" approach to characterize complex air pollutant mixtures was applied in the Oil Sands region of northern Alberta, Canada. This approach was developed to better-inform source characterization and attribution of the air pollution in the Indigenous community of Fort McKay, within the context of the lived experience of residents. Principal component analysis was used to identify the characteristics of primary pollutant mixtures, which were related to hydrocarbon emissions, fossil fuel combustion, dust, and oxidized and reduced sulfur compounds. Concentration distributions of indicator compounds were used to isolate sustained air pollution "events". Diesel-powered vehicles operating in the mines were found to be an important source during NO x events. Industry-specific volatile organic compound (VOC) profiles were used in a chemical mass balance model for source apportionment, which revealed that nearby oil sands operations contribute to 86% of the total mass of nine VOC species (2-methylpentane, hexane, heptane, octane, benzene, toluene, m , p -xylene, o -xylene, and ethylbenzene) during VOC events. Analyses of the frequency distribution of air pollution events indicate that Fort McKay is regularly impacted by multiple mixtures simultaneously, underscoring the limitations of an exceedance-based approach relying on a small number of air quality standards as the only tool to assess risk.

Exposure to ambient fine particulate matter (PM 2.5 ) is a leading risk factor for the global burden of disease. However, uncertainty remains about PM 2.5 sources. We use a global chemical transport model (GEOS-Chem) simulation for 2014, constrained by satellite-based estimates of PM 2.5 to interpret globally dispersed PM 2.5 mass and composition measurements from the ground-based surface particulate matter network (SPARTAN). Measured site mean PM 2.5 composition varies substantially for secondary inorganic aerosols (2.4-19.7 μg/m 3 ), mineral dust (1.9-14.7 μg/m 3 ), residual/organic matter (2.1-40.2 μg/m 3 ), and black carbon (1.0-7.3 μg/m 3 ). Interpretation of these measurements with the GEOS-Chem model yields insight into sources affecting each site. Globally, combustion sectors such as residential energy use (7.9 μg/m 3 ), industry (6.5 μg/m 3 ), and power generation (5.6 μg/m 3 ) are leading sources of outdoor global population-weighted PM 2.5 concentrations. Global population-weighted organic mass is driven by the residential energy sector (64%) whereas population-weighted secondary inorganic concentrations arise primarily from industry (33%) and power generation (32%). Simulation-measurement biases for ammonium nitrate and dust identify uncertainty in agricultural and crustal sources. Interpretation of initial PM 2.5 mass and composition measurements from SPARTAN with the GEOS-Chem model constrained by satellite-based PM 2.5 provides insight into sources and processes that influence the global spatial variation in PM 2.5 composition.

Gas-phase acids in light duty diesel (LDD) vehicle exhaust were measured using chemical ionization mass spectrometry (CIMS). Fuel based emission factors (EF) and NOx ratios for these species were determined under differing steady state engine operating conditions. The derived HONO and HNO3 EFs agree well with literature values, with HONO being the single most important acidic emission. Of particular importance is the quantification of the EF for the toxic species, isocyanic acid (HNCO). The emission factors for HNCO ranged from 0.69 to 3.96 mg kgfuel(-1), and were significantly higher than previous biomass burning emission estimates. Further ambient urban measurements of HNCO demonstrated a clear relationship with the known traffic markers of benzene and toluene, demonstrating for the first time that urban commuter traffic is a source of HNCO. Estimates based upon the HNCO-benzene relationship indicate that upward of 23 tonnes of HNCO are released annually from commuter traffic in the Greater Toronto Area, far exceeding the amount possible from LDD alone. Nationally, 250 to 770 tonnes of HNCO may be emitted annually from on-road vehicles, likely representing the dominant source of exposure in urban areas, and with emissions comparable to that of biomass burning.

Measurements of black carbon (BC) with a high-sensitivity laser-induced incandescence (HS-LII) instrument and a single particle soot photometer (SP2) were conducted upwind, downwind, and while driving on a highway dominated by gasoline vehicles. The results are used with concurrent CO(2) measurements to derive fuel-based BC emission factors for real-world average fleet and heavy-duty diesel vehicles separately. The derived emission factors from both instruments are compared, and a low SP2 bias (relative to the HS-LII) is found to be caused by a BC mass mode diameter less than 75 nm, that is most prominent with the gasoline fleet but is not present in the heavy-duty diesel vehicle exhaust on the highway. Results from both the LII and the SP2 demonstrate that the BC emission factors from gasoline vehicles are at least a factor of 2 higher than previous North American measurements, and a factor of 9 higher than currently used emission inventories in Canada, derived with the MOBILE 6.2C model. Conversely, the measured BC emission factor for heavy-duty diesel vehicles is in reasonable agreement with previous measurements. The results suggest that greater attention must be paid to black carbon from gasoline engines to obtain a full understanding of the impact of black carbon on air quality and climate and to devise appropriate mitigation strategies., (© 2012 American Chemical Society)

The chemical composition of Toronto PM2.5 was measured daily from Feb 2000 to Feb 2001, and source apportionment was undertaken using positive matrix factorization (PMF). In Toronto, PM2.5 levels were influenced both by local urban activities and also by regional-scale transport. Although several PMF solutions were possible, an eight-source model for explaining the observed Toronto PM2.5 was found to provide realistic results and interesting insights into sources. The four main sources were coal combustion related to regional transport and secondary sulfate (26%), secondary nitrate related to both local and upwind sources of NOx and NH3 (36%), secondary organic aerosols (SOA) formed from a variety of precursor organic emissions (15%), and motor vehicle traffic (10%). The other detectable sources were road salt (winter) and three types of primary PM2.5 hypothesized to be associated with smelters, coal and oil combustion, industry, and local construction. Overall, motor vehicle-related emissions (including road salt and nitrate) were estimated to be responsible for about 40% of the PM2.5. In the summer, the SOA mass was estimated to contribute approximately 20% to the PM2.5. Inclusion of water-soluble, low-molecular-weight organic acids led to identification of this component, thus providing a significant improvement in PMF's ability to resolve sources. Without organic acid measurements the SOA portion of the observed PM2.5 was assigned to the secondary coal component, increasing its contribution and resulting in a source profile with an unrealistic amount of organic mass. This suggests that in the northeastern part of North America, there are physical and/or chemical processes that lead to close interaction between secondary organic and inorganic aerosols.

Measurement of particle-bound organic carbon (OC) may be complicated by sampling artifacts such as adsorption of gas-phase species onto particles or filters or evaporation of semivolatile compounds off the particles. A denuder-based integrated organic gas and particle sampler (IOGAPS), specifically designed to minimize sampling artifacts, has been developed to sample atmospheric carbonaceous aerosols. IOGAPS is designed to first remove gas-phase chemicals via sorption to the XAD-coated denuder, and subsequently particles are trapped on a quartz filter. A backup sorbent system consisting of sorbent- (XAD-4 resin) impregnated filters (SIFs) was used to capture the semivolatile OC that evaporates from the particles accumulated on the upstream quartz filter. A traditional filter pack (FP) air sampler, which uses a single quartz filter to collect the particles, was employed for comparison in this study. Elemental and organic carbon were determined from filter punches by a thermal optical transmittance aerosol carbon analyzer. Field measurements show that there was no significant difference between the elemental carbon concentrations determined by the FP and IOGAPS, indicating that particle loss during the transit through the denuder tube was negligible. Compared with the OC determined by FP (3.9-12.6 microg of C/m3), the lower OC observed on the quartz filter in the IOGAPS (2.2-6.0 microg of C/m3) was expected because of the removal of gas-phase organics by the denuder. Higher semivolatile organic carbon (SVOC) on the backup SIFs during the night (1.24-8.43 microg of C/m3) suggests that more SVOC, emitted from primary sources or formed as secondary organic compounds, partitions onto the particles during the night because of the decreased ambient temperature. These data illustrate the utility of an IOGAPS system to more accurately determine the particle-bound OC in comparison to FP-based systems.

A 10-day winter sampling campaign was conducted in downtown Toronto for particulate matter (PM) air pollution in the fine (<2.5 microm) size range. An aerosol laser ablation mass spectrometer (LAMS), a tapered-element oscillating microbalance (TEOM), and an aerodynamic particle sizer (APS) were operated in parallel to characterize the PM on-line. In this study, the LAMS observed differences in the chemical composition between three separate episodes with higher PM2.5 mass and APS counts. LAMS results showed that in one instance of elevated PM, organic amines were present in the particulates. Temporal analyses of this episode revealed chemical transformations as the amines, characterized by m/z peaks 58(C3HeN)+, 86(C5H2N)+, and nitrates, increased in number concentration while Ca and hydrocarbon particle classes concurrently decreased. On another day, sulfates were found to have increased significantly. The third event was only 4 h in duration and exhibited an increase in the number of submicron-sized K/hydrocarbons and sulfate-containing particles. In this last event, the hydrocarbons and a K to Fe ratio enrichment indicated there was likely a contribution from a combustion source. This work offers some of the first insights into single particle size and chemistry in a cold winter climate.