Researches:

Article title: Impact of COVID-19 lockdown on particulate matter oxidative potential at urban background versus traffic sites
Authors: Lucille Joanna S. Borlaza, Vy Dinh Ngoc Thuy, Stuart Grange,St´ephane Socquet, Emmanuel Moussu, Gladys Mary, Olivier Favez, Christoph Hueglin, Jean-Luc Jaffrezo and Ga¨elle Uzu
Publication title: Environmental Science: Atmospheres 2023

Abstract:
In Europe, COVID-19 lockdown restrictions were first implemented in March 2020 to control the spread of the disease from the SARS-CoV-2 virus. Many studies have focused on the influence of the applied measures on pollution levels during this period, but very limited information on the oxidative potential (OP), an emerging metric of particulate matter (PM) exposure. Furthermore, most previous studies also commonly used comparative methods with historical datasets, which may not be estimating the real pollution levels without the lockdown restrictions in place. In this study, the OP of PM collected at an urban background (Grenoble, France) and traffic (Bern, Switzerland) sites were assessed using dithiothreitol (DTT) and ascorbic acid (AA) assays. These measurements were also compared with PM and black carbon (BC) mass concentrations, including the wood burning and fossil fuel fractions of BC. To obtain a more realistic pollution level, assuming there were no lockdown restrictions in place, a machine learning technique called Random Forest (RF) regression model was applied to predict a business-as-usual (BAU) level for OP, PM, and BC in both sites. This model provided a good estimate of the BAU levels, allowing a more realistic assessment of the pollution changes during the lockdown period. Results indicate a clear decrease in OP found in the traffic site, while a more modest change in OP was found at the urban background site, likely due to sustained contributions from wood burning sources for residential heating. Overall, this study confirms the major roles of both of these combustion sources on the OP levels in ambient air.
Full text available upon request to the author/s

Article title: Prenatal Exposure to PM2.5 Oxidative Potential and Lung Function in Infants and Preschool- Age Children: A Prospective Study
Authors: Anouk Marsal, Rémy Slama, Sarah Lyon-Caen, Lucille Joanna S. Borlaza,Jean-Luc Jaffrezo, Anne Boudier, Sophie Darfeuil,Rhabira Elazzouzi, Yoann Gioria, Johanna Lepeule, Ryan Chartier, Isabelle Pin, Joane Quentin, Sam Bayat, Gaëlle Uzu, Valérie Siroux, and the SEPAGES cohort study group
Publication title: Environmental Health Perspectives 131(1), 2023

Abstract:
Background: Fine particulate matter (PM2.5) has been found to be detrimental to respiratory health of children, but few studies have examined the effects of prenatal PM2.5 oxidative potential (OP) on lung function in infants and preschool children.

Objectives: We estimated the associations of personal exposure to PM2.5 and OP during pregnancy on offspring objective lung function parameters and compared the strengths of associations between both exposure metrics.

Methods: We used data from 356 mother-child pairs from the SEPAGES cohort. PM filters collected twice during a week were analyzed for OP, using the dithiothreitol (DTT) and the ascorbic acid (AA) assays, quantifying the exposure of each pregnant woman. Lung function was assessed with tidal breathing analysis (TBFVL) and nitrogen multiple-breath washout (N2MBW) test, performed at 6 wk, and airwave oscillometry (AOS) performed at 3 y. Associations of prenatal PM2.5 mass and OP with lung function parameters were estimated using multiple linear regressions.

Results: In neonates, an interquartile (IQR) increase in OPvDTT (0.89 nmol/min/m3) was associated with a decrease in functional residual capacity (FRC) measured by N2MBW [β=-2.26mL; 95% confidence interval (CI): -4.68, 0.15]. Associations with PM2.5 showed similar patterns in comparison with OPvDTT but of smaller magnitude. Lung clearance index (LCI) and TBFVL parameters did not show any clear association with the exposures considered. At 3 y, increased frequency-dependent resistance of the lungs (Rrs7-19) from AOS tended to be associated with higher OPvDTT (β=0.09 hPa×s/L; 95% CI: -0.06, 0.24) and OPvAA (IQR=1.14 nmol/min/m3; β=0.12 hPa×s/L; 95% CI: -0.04, 0.27) but not with PM2.5 (IQR=6.9 μg/m3; β=0.02 hPa×s/L; 95% CI: -0.13, 0.16). Results for FRC and Rrs7-19 remained similar in OP models adjusted on PM2.5.

Discussion: Prenatal exposure to OPvDTT was associated with several offspring lung function parameters over time, all related to lung volumes. https://doi.org/10.1289/EHP11155.
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Article title: Source apportionment study on particulate air pollution in two high- altitude Bolivian cities: La Paz and El Alto
Authors: Valeria Mardoñez, Marco Pandolfi, Lucille Joanna S. Borlaza, Jean-Luc Jaffrezo, Andrés Alastuey, Jean-Luc Besombes, Isabel Moreno R., Noemi Perez, Griša Močnik, Patrick Ginot, Radovan Krejci, Vladislav Chrastny, Alfred Wiedensohler, Paolo Laj, Marcos Andrade, and Gaëlle Uzu
Publication title: Atmospheric Chemistry and Physics 2022

Abstract:
La Paz and El Alto are two fast-growing high-altitude Bolivian cities forming the second largest metropolitan area in the country, located between 3200 and 4050 m a.s.l. Together they host a growing population of around 1.8 million people. The air quality in this conurbation is strongly influenced by urbanization. However, there are no comprehensive studies that have assessed the sources of air pollution and their impacts on health. Despite being neighboring cities, the drastic change in altitude and topography between La Paz and El Alto together with different socio-economic activities lead to different sources, dynamics and transport of particulate matter (PM). In this investigation, PM10 samples were collected at two urban background stations located in La Paz and El Alto between April 2016 and June 2017. The samples were later analyzed for a wide range of chemical species including numerous source tracers (OC, EC, water-soluble ions, sugar anhydrides, sugar alcohols, trace metals, and molecular organic species). The US-EPA Positive Matrix Factorization (PMF v.5.0) receptor model was then applied for source apportionment of PM10. This is the first source apportionment study in South America that incorporates a large set of organic markers (such as levoglucosan, polycyclic aromatic hydrocarbons – PAH, hopanes and alkanes) together with inorganic species. The multisite PMF resolved 11 main sources of PM. The largest annual contribution to PM10 came from two major sources: the ensemble of the four vehicular emissions sources (exhaust and non-exhaust), together responsible for 35 % and 25 % of the measured PM in La Paz and El Alto, respectively, and dust contributing 20 % and 32 % to the total. Secondary aerosols contributed 22 % (24 %) in La Paz (El Alto). Agriculture-related smoke from biomass burning originated in the Bolivian lowlands and neighboring countries contributed to 8 % (7 %) of the total PM10 mass annually. This contribution increased to 17 % (13 %) between August–October. Primary biogenic emissions were responsible for 13 % (7 %) of the measured PM10 mass. Finally, it was possible to identify a profile related to open waste burning occurring between the months of May and August. Despite the fact that this source contributed only to 2 % (5 %) of the total PM10 mass, it constitutes the second largest source of PAHs, compounds potentially hazardous to health. Our analysis resulted in the identification of two specific traffic-related sources. In addition, we also identified a lubricant source (not frequently identified) and a non-exhaust emissions source. This study shows that PM10 concentrations in La Paz and El Alto region are mostly impacted by a limited number of local sources. In conclusion, dust, traffic emissions, open waste burning and biomass burning are the main sources to target in order to improve air quality in both cities.
Full text available upon request to the author/s

Article title: Personal exposure to PM2.5 oxidative potential and its association to birth outcomes
Authors: Lucille Joanna S. Borlaza, Gaëlle Uzu, Marion Ouidir, Sarah Lyon-Caen, Anouk Marsal, Samuël Weber, Valérie Siroux, Johanna Lepeule, Anne Boudier, Jean-Luc Jaffrezo, Rémy Slama and the SEPAGES cohort study group
Publication title: Journal of Exposure Science & Environmental Epidemiology 2022

Abstract:
Background: Prenatal exposure to fine particulate matter (PM2.5) assessed through its mass concentration has been associated with foetal growth restriction in studies based on outdoor levels. Oxidative potential of PM2.5 (OP) is an emerging metric a priori relevant to mechanisms of action of PM on health, with very limited evidence to indicate its role on birth outcomes.

Objectives: We investigated the association of OP with birth outcomes and compared it with that of PM2.5 mass concentration.

Methods: 405 pregnant women from SEPAGES cohort (Grenoble area) carried PM2.5 personal dosimeters for one or two one-week periods. OP was measured using dithiothreitol (DTT) and ascorbic acid (AA) assays from the collected filters. Associations of each exposure metric with offspring weight, height, and head circumference at birth were estimated adjusting for potential confounders.

Results: The correlation between PM2.5 mass concentration and [Formula: see text] was 0.7. An interquartile range increase in .. was associated with reduced weight (adjusted change, -64 g, -166 to -11, p = 0.02) and height (-4 mm, -6 to -1, p = 0.01) at birth. PM2.5 mass concentration showed similar associations with weight (-53 g, -99 to -8, p = 0.02) and height (-2 mm, -5 to 0, p = 0.05). In birth height models mutually adjusted for the two exposure metrics, the association with [Formula: see text] was less attenuated than that with mass concentration, while for weight both effect sizes attenuated similarly. There was no clear evidence of associations with head circumference for any metric, nor for [Formula: see text] with any growth parameter. Impact: PM2.5 pregnancy exposure assessed from personal dosimeters was associated with altered foetal growth. Personal OP exposure was associated with foetal growth restrictions, specifically decreased weight and height at birth, possibly to a larger extent than PM2.5 mass concentration alone. These results support OP assessed from DTT as being a health-relevant metric. Larger scale cohort studies are recommended to support our findings.
Full text available upon request to the author/s

Article title: Nine-year trends of PM 10 sources and oxidative potential in a rural background site in France
Authors: Lucille Joanna Borlaza, Samuël Weber, Anouk Marsal, Gaëlle Uzu, VéroniqueJacob, Jean-Luc Besombes, Mélodie Chatain, Sébastien Conil, Jean-LucJarezo
Publication title: Atmospheric Chemistry and Physics 22(13):8701-8723, 2022

Abstract:
Long-term monitoring at sites with relatively low particulate pollution could provide an opportunity to identify changes in pollutant concentration and potential effects of current air quality policies. In this study, 9-year sampling of PM10 (particles with an aerodynamic diameter below 10 µm) was performed in a rural background site in France (Observatoire Pérenne de l'Environnement or OPE) from 28 February 2012 to 22 December 2020. The positive matrix factorization (PMF) method was used to apportion sources of PM10 based on quantified chemical constituents and specific chemical tracers analysed on collected filters. Oxidative potential (OP), an emerging health metric that measures PM capability to potentially cause anti-oxidant imbalance in the lung, was also measured using two acellular assays: dithiothreitol (DTT) and ascorbic acid (AA). The sources of OP were also estimated using multiple linear regression (MLR) analysis. In terms of mass contribution, the dominant sources are secondary aerosols (nitrate- and sulfate-rich) associated with long-range transport (LRT). However, in terms of OP contributions, the main drivers are traffic, mineral dust, and biomass burning factors. There is also some OP contribution apportioned to the sulfate- and nitrate-rich sources influenced by processes and ageing during LRT that could have encouraged mixing with other anthropogenic sources. The study indicates much lower OP values than in urban areas. A substantial decrease (58 % reduction from the year 2012 to 2020) in the mass contributions from the traffic factor was found, even though this is not clearly reflected in its OP contribution. Nevertheless, the findings in this long-term study at the OPE site could indicate effectiveness of implemented emission control policies, as also seen in other long-term studies conducted in Europe, mainly for urban areas.
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Article title: Cellulose in atmospheric particulate matter at rural and urban sites across France and Switzerland
Authors: Adam Brighty, Véronique Jacob, Gaëlle Uzu, Lucille Borlaza, Sébastien Conil,Christoph Hueglin, Stuart K. Grange, Olivier Favez, Cécile Trébuchon, and Jean-Luc Jaffrezo
Publication title: Atmospheric Chemistry and Physics 22(9):6021-6043, 2022

Abstract:
The spatiotemporal variations in free-cellulose concentrations in atmospheric particles, as a proxy for plant debris, were investigated using an improved protocol with a high-performance liquid chromatography with pulsed amperometric detection (HPLC-PAD) method. Filter samples were taken from nine sites of varying characteristics across France and Switzerland, with sampling covering all seasons. Concentrations of cellulose, as well as carbonaceous aerosol and other source-specific chemical tracers (e.g. elemental carbon, EC; levoglucosan; polyols; trace metals; and glucose), were quantified. Annual mean free-cellulose concentrations within PM10 (particulate matter) ranged from 29 ± 38 ng m−3 at Basel (urban site) to 284 ± 225 ng m−3 at Payerne (rural site). Concentrations were considerably higher during episodes, with spikes exceeding 1150 and 2200 ng m−3 at Payerne and ANDRA-OPE (Agence nationale pour la gestion des déchets radioactifs Observatoire Pérenne de l'Environnement; rural site), respectively. A clear seasonality, with highest cellulose concentrations during summer and autumn, was observed at all rural and some urban sites. However, some urban locations exhibited a weakened seasonality. Contributions of cellulose carbon to total organic carbon are moderate on average (0.7 %–5.9 %) but much greater during “episodes”, reaching close to 20 % at Payerne. Cellulose concentrations correlated poorly between sites, even at ranges of about 10 km, indicating the localised nature of the sources of atmospheric plant debris. With regards to these sources, correlations between cellulose and typical biogenic chemical tracers (polyols and glucose) were moderate to strong (Rs = 0.28–0.78, p < 0.0001) across the nine sites. Seasonality was strongest at sites with stronger biogenic correlations, suggesting the main source of cellulose arises from biogenic origins. A second input to ambient plant debris concentrations was suggested via resuspension of plant matter at several urban sites, due to moderate cellulose correlations with mineral dust tracers, Ca2+, and Ti metal (Rs = 0.28–0.45, p < 0.007). No correlation was obtained with the biomass burning tracer (levoglucosan), an indication that this is not a source of atmospheric cellulose. Finally, an investigation into the interannual variability in atmospheric cellulose across the Grenoble metropole was completed. It was shown that concentrations and sources of ambient cellulose can vary considerably between years. All together, these results deeply improve our knowledge on the phenomenology of plant debris within ambient air.
Full text available upon request to the author/s

Article title: Source apportionment of atmospheric PM10 oxidative potential: synthesis of 15 year-round urban datasets in France
Authors: Samuël Weber, Gaëlle Uzu, Olivier Favez, Lucille Joanna S. Borlaza, Aude Calas, Dalia Salameh, Florie Chevrier, Julie Allard, Jean-Luc Besombes, Alexandre Albinet, Sabrina Pontet, Boualem Mesbah, Grégory Gille, Shouwen Zhang, Cyril Pallares, Eva Leoz-Garziandia, and Jean-Luc Jaffrezo
Publication title: Atmospheric Chemistry and Physics 21(14):11353-11378, 2021

Abstract:
Reactive oxygen species (ROS) carried or induced by particulate matter (PM) are suspected of inducing oxidative stress in vivo, leading to adverse health impacts such as respiratory or cardiovascular diseases. The oxidative potential (OP) of PM, displaying the ability of PM to oxidize the lung environment, is gaining strong interest in examining health risks associated with PM exposure. In this study, OP was measured by two different acellular assays (dithiothreitol, DTT, and ascorbic acid, AA) on PM10 filter samples from 15 yearly time series of filters collected at 14 different locations in France between 2013 and 2018, including urban, traffic and Alpine valley site typologies. A detailed chemical speciation was also performed on the same samples, allowing the source apportionment of PM using positive matrix factorization (PMF) for each series, for a total number of more than 1700 samples. This study then provides a large-scale synthesis of the source apportionment of OP using coupled PMF and multiple linear regression (MLR) models. The primary road traffic, biomass burning, dust, MSA-rich, and primary biogenic sources had distinct positive redox activity towards the OPDTT assay, whereas biomass burning and road traffic sources only display significant activity for the OPAA assay. The daily median source contribution to the total OPDTT highlighted the dominant influence of the primary road traffic source. Both the biomass burning and the road traffic sources contributed evenly to the observed OPAA. Therefore, it appears clear that residential wood burning and road traffic are the two main target sources to be prioritized in order to decrease significantly the OP in western Europe and, if the OP is a good proxy of human health impact, to lower the health risks from PM exposure.
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Article title: Disparities in particulate matter (PM10) origins and oxidative potential at a city scale (Grenoble, France) – Part 2: Sources of PM10 oxidative potential using multiple linear regression analysis and the predictive applicability of multilayer perceptron neural network analysis
Authors: Lucille Joanna S. Borlaza, Samuël Weber, Jean-Luc Jaffrezo, Stephan Houdier, Rémy Slama, Camille Rieux, Alexandre Albinet, Steve Micallef, Cécile Trébluchon, and Gaëlle Uzu
Publication title: Atmospheric Chemistry and Physics 21(12):9719-9739, 2021

Abstract:
The oxidative potential (OP) of particulate matter (PM) measures PM capability to potentially cause anti-oxidant imbalance. Due to the wide range and complex mixture of species in particulates, little is known about the pollution sources most strongly contributing to OP. A 1-year sampling of PM10 (particles with an aerodynamic diameter below 10) was performed over different sites in a medium-sized city (Grenoble, France). An enhanced fine-scale apportionment of PM10 sources, based on the chemical composition, was performed using the positive matrix factorization (PMF) method and reported in a companion paper (Borlaza et al., 2020). OP was assessed as the ability of PM10 to generate reactive oxygen species (ROS) using three different acellular assays: dithiothreitol (DTT), ascorbic acid (AA), and 2,7-dichlorofluorescein (DCFH) assays. Using multiple linear regression (MLR), the OP contributions of the sources identified by PMF were estimated. Conversely, since atmospheric processes are usually non-linear in nature, artificial neural network (ANN) techniques, which employ non-linear models, could further improve estimates. Hence, the multilayer perceptron analysis (MLP), an ANN-based model, was additionally used to model OP based on PMF-resolved sources as well. This study presents the spatiotemporal variabilities of OP activity with influences by season-specific sources, site typology and specific local features, and assay sensitivity. Overall, both MLR and MLP effectively captured the evolution of OP. The primary traffic and biomass burning sources were the strongest drivers of OP in the Grenoble basin. There is also a clear redistribution of source-specific impacts when using OP instead of mass concentration, underlining the importance of PM redox activity for the identification of potential sources of PM toxicity. Finally, the MLP generally offered improvements in OP prediction, especially for sites where synergistic and/or antagonistic effects between sources are prominent, supporting the value of using ANN-based models to account for the non-linear dynamics behind the atmospheric processes affecting OP of PM10.
Full text available upon request to the author/s

Article title: Disparities in particulate matter (PM10) origins and oxidative potential at a city scale (Grenoble, France) – Part 1: Source apportionment at three neighbouring sites
Authors: Lucille Joanna S. Borlaza, Samuël Weber, Gaëlle Uzu, Véronique Jacob, Trishalee Cañete, Steve Micallef, Cécile Trébuchon, Rémy Slama, Olivier Favez, and Jean-Luc Jaffrezo
Publication title: Atmospheric Chemistry and Physics 21(7):5415-5437, 2021

Abstract:
A fine-scale source apportionment of PM10 was conducted in three different urban sites (background, hyper-center, and peri-urban) within 15 km of the city in Grenoble, France using Positive Matrix Factorization (PMF 5.0) on measured chemical species from collected filters (24 h) from February 2017 to March 2018. To improve the PMF solution, several new organic tracers (3-MBTCA, pinic acid, phthalic acid, MSA, and cellulose) were additionally used in order to identify sources that are commonly unresolved by classic PMF methodologies. An 11-factor solution was obtained in all sites, including commonly identified sources from primary traffic (13 %), nitrate-rich (17 %), sulfate-rich (17 %), industrial (1 %), biomass burning (22 %), aged sea salt (4 %), sea/road salt (3 %), and mineral dust (7 %), and the newly found sources from primary biogenic (4 %), secondary biogenic oxidation (10 %), and MSA-rich (3 %). Generally, the chemical species exhibiting similar temporal trends and strong correlations showed uniformly distributed emission sources in the Grenoble basin. The improved PMF model was able to obtain and differentiate chemical profiles of specific sources even at high proximity of receptor locations, confirming its applicability in a fine-scale resolution. In order to test the similarities between the PMF-resolved sources, the Pearson distance and standardized identity distance (PD-SID) of the factors in each site were compared. The PD-SID metric determined whether a given source is homogeneous (i.e., with similar chemical profiles) or heterogeneous over the three sites, thereby allowing better discrimination of localized characteristics of specific sources. Overall, the addition of the new tracers allowed the identification of substantial sources (especially in the SOA fraction) that would not have been identified or possibly mixed with other factors, resulting in an enhanced resolution and sound source profile of urban air quality at a city scale.
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Article title: Comparison of physical and chemical characteristics and oxidative potential of fine particles emitted from rice straw and pine stem burning
Authors: Ilhwa Seo, Kwangyul Lee, Min-Suk Bae, Minhan Park, Shila Maskey, Arom Seo,Lucille Joanna S. Borlaza, Enrique Mikhael R. Cosep, Kihong Park
Publication title: Environmental Pollution 267, 2020

Abstract:
Agricultural burning and forest fires are common in Northeast Asia and contribute to the elevation of fine particulate pollution, which greatly affects air quality. In this study, chemical and physical attributes, as well as the oxidative potential of fine particles produced from rice straw and pine stem burning in a laboratory-scale chamber were determined. The burning of rice straw generated notably lower emissions of fine particles and elemental carbon (EC) than did the burning of pine stems. The longer retention of ultrafine particles was observed for rice straw burning likely caused by this material’s longer period of initial flaming combustion. Organic carbon (OC), OC/EC, K+/OC, K+/EC, Zn, and alkanoic acid were higher in the fine particles of rice straw burning, while EC, K+/Cl−, Fe, Cr, Al, Cu, and levoglucosan were higher for pine stem burning particles. Chemical data were consistent with a higher hygroscopic growth factor and cloud formation potential and lower amount of agglomerated soot for rice straw burning particles. Rice straw burning particles displayed an oxidative potential seven times higher than that of pine stems.
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Article title: Simultaneous Measurements of Chemical Compositions of Fine Particles during Winter Haze Period in Urban Sites in China and Korea
Authors: Minhan Park, Yujue Wang, Jihyo Chong, Haebum Lee, Jiho Jang, Hangyul Song, Nohhyeon Kwak, Lucille Joanna S. Borlaza, Hyunok Maeng, Enrique Mikhael R.Cosep, Ma. Cristine Faye J. Denna, Shiyi Chen, Ilhwa Seo, Min‐SukBae, Kyoung‐Soon Jang, Mira Choi, Young Hwan Kim, Moonhee Park, Jong‐Sik Ryu, Sanghee Park, Min Hu, and Kihong Park
Publication title: Atmosphere 11(3):292, 2020

Abstract:
We performed simultaneous measurements of chemical compositions of fine particles in Beijing, China and Gwangju, Korea to better understand their sources during winter haze period. We identified PM2.5 events in Beijing, possibly caused by a combination of multiple primary combustion sources (biomass burning, coal burning, and vehicle emissions) and secondary aerosol formation under stagnant conditions and/or dust sources under high wind speeds. During the PM2.5 events in Gwangju, the contribution of biomass burning and secondary formation of nitrate and organics to the fine particles content significantly increased under stagnant conditions. We commonly observed the increases of nitrogen-containing organic compounds and biomass burning inorganic (K+) and organic (levoglucosan) markers, suggesting the importance of biomass burning sources during the winter haze events (except dust event cases) at both sites. Pb isotope ratios indicated that the fraction of Pb originated from possibly industry and coal combustion sources increased during the PM2.5 events in Gwangju, relative to nonevent days.
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Article title: Differential toxicities of fine particulate matters from various sources
Springer Nature
Authors: Minhan Park, Hung Soo Joo, Kwangyul Lee, Myoseon Jang, Sang Don Kim, Injeong Kim, Lucille Joanna S. Borlaza, Heungbin Lim, Hanjae Shin, Kyu Hyuck Chung, Yoon-Hyeong Choi, Sun Gu Park, Min-Suk Bae, Jiyi Lee, Hangyul Song & Kihong Park
Publication title: Scientific Reports 8(1), 2018

Abstract:
Fine particulate matters less than 2.5 µm (PM2.5) in the ambient atmosphere are strongly associated with adverse health effects. However, it is unlikely that all fine particles are equally toxic in view of their different sizes and chemical components. Toxicity of fine particles produced from various combustion sources (diesel engine, gasoline engine, biomass burning (rice straw and pine stem burning), and coal combustion) and non-combustion sources (road dust including sea spray aerosols, ammonium sulfate, ammonium nitrate, and secondary organic aerosols (SOA)), which are known major sources of PM2.5, was determined. Multiple biological and chemical endpoints were integrated for various source-specific aerosols to derive toxicity scores for particles originating from different sources. The highest toxicity score was obtained for diesel engine exhaust particles, followed by gasoline engine exhaust particles, biomass burning particles, coal combustion particles, and road dust, suggesting that traffic plays the most critical role in enhancing the toxic effects of fine particles. The toxicity ranking of fine particles produced from various sources can be used to better understand the adverse health effects caused by different fine particle types in the ambient atmosphere, and to provide practical management of fine particles beyond what can be achieved only using PM mass which is the current regulation standard.
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Article title: Oxidative potential of fine ambient particles in various environments
Authors: Lucille Joanna S. Borlaza, Enrique Mikhael R. Cosep, Seojong Kim, Kwangyul Lee, Hungsoo Joo, Minhan Park, Daphne Bate, Mylene G. Cayetano, Kihong Park
Publication title: Environmental Pollution 243(B):1679-1688, 2018

Abstract:
The oxidative potential (OP) and chemical characteristics of fine particles collected from urban, roadside, rural, and industrial sites in Korea during spring, summer, fall, and winter seasons and an urban site in the Philippines during dry and wet seasons were examined. Significant differences in the OP of fine particles among sites and seasons were found. The industrial site yielded the highest OP activity (both mass and volume-normalized OP) among the sites, suggesting the strongest reactive oxygen species (ROS)-generating capability of industry source-dominant PM2.5. Seasonal data show that OP activities increased during the spring and summer possibly due to increased heavy metals caused by dust events and secondary organic aerosols formed by strong photochemical activity, respectively. The strength of the OP association with the chemical components highlights the influence of organic carbon and transition metals on the OP of ambient fine particles. The two OP assays (dithiothreitol (DTT) and electron spin resonance (ESR)) having different ROS-generating mechanisms were found to have different sensitivities to the chemical components facilitating a complementary analysis of the OP of ambient fine particles. Multiple linear regression model equations (OP as a function of chemical components) which were dependent on the sites were derived. A comparison of the daily OP and hazard index (HI) (the ratio of the measured mass concentration to the reference mass concentration of fine particles) suggests that the HI may not be sufficient to accurately estimate the health effects of fine particles, and a direct or indirect measurement of toxicity such as OP should be required in addition to the concentration level.
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Article title: Physicochemical properties and oxidative potential of fine particles produced from coal combustion
Authors: Hung Soo Joo, Tsatsa Batmunkh, Lucille Joanna S. Borlaza, Minhan Park, Kwang Yul Lee, Ji Yi Lee, Yu Won Chang, Kihong Park
Publication title: Aerosol Science and Technology 52(11):1-11, 2018

Abstract:
The physical and chemical properties as well as the oxidative potential (OP) of water soluble components of coal combustion fine particles were examined. A laboratory-scale pulverized-coal burning system was used to produce coal combustion particles at different burning temperatures of 550 °C, 700 °C, 900 °C, and 1,100 °C. Few studies have reported the effects of burning temperature on both the chemistry and toxicity of coal combustion particles. The highest mass emission factor of particulate matter less than 2.5 µm (PM2.5) was found to be produced at 700 °C (3.51 g/kg), owing to strong elemental carbon (EC) emission and ash formation (ions and elements) resulting from the incomplete combustion of tar and char, and mineral fragmentation. The highest organic carbon in PM2.5 was found at 550 °C. At a temperature higher than 700 °C, the fraction of carbonaceous species decreased while the fractions of ions and elements increased owing to ash formation. Sulfate was found to be the dominant ionic species, followed by sodium, calcium, and magnesium. The highest emission of elements (Al, As, Ba, Cd, Co, Cu, Fe, Mn, Ni, Pb, Sr, Ti, V, and Zn) and the highest fractions of Fe and Al were observed at 700 °C. Intrinsic OP activities obtained from dithiothreitol (DTT) and electron spin resonance (ESR) assays showed the highest values at 550 °C, suggesting that fine particles from low-temperature coal combustion had the highest reactive oxygen species generation capability (potentially toxic) among various tested burning temperatures. The results of principal component analysis suggested a correlation between OP-DTT activity and OC, EC, Cd, Co, V, and Zn, while OP-ESR activity was associated with chloride, nitrate, Ba, Pb, Sr, and Ti.
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