scholarly journals Characterization and comparison of PM<sub>2.5</sub> oxidative potential assessed by two acellular assays

2019 ◽  
Author(s):  
Dong Gao ◽  
Krystal J. Pollitt ◽  
James A. Mulholland ◽  
Armistead G. Russell ◽  
Rodney J. Weber
Keyword(s):  
Metal Ions ◽  
Water Soluble ◽  
Metal Species ◽  
Urban Site ◽  
Chemical Components ◽  
Linear Regression Models ◽  
Oxidative Potential ◽  
Metal Interactions ◽  
Metal Metal

Abstract. The capability of ambient particles to generate in vivo reactive oxygen species (ROS), called the oxidative potential (OP), is a potential metric for relating particulate matter (PM) to health effects and is supported by several recent epidemiological investigations. However, studies using various types of OP assays differ in their sensitivities to varying PM chemical components. In this study, we systematically compared two health-relevant acellular OP assays that track the depletion of antioxidants or reductant surrogates: the synthetic respiratory tract lining fluid (RTLF) assay that tracks the depletion of ascorbic acid (AA) and glutathione (GSH), and the dithiothreitol (DTT) assay that tracks the depletion of DTT. Year-long daily samples were collected at an urban site (Jefferson Street) in Atlanta during 2017 and both DTT and RTLF assays were applied to measure the OP of water-soluble PM2.5 components. PM2.5 mass and major chemical components, including metals, ions, and organic and elemental carbon were also analyzed. Correlation analysis found that OP as measured by the DTT and AA depletion (OPDTT and OPAA, respectively) were correlated with both organics and some water-soluble metal species, whereas that from the GSH depletion (OPGSH) was exclusively sensitive to water-soluble Cu. These OP assays were moderately correlated with each other due to the common contribution from metal ions. OPDTT and OPAA were moderately correlated with PM2.5 mass, with Pearson’s r = 0.55 and 0.56, respectively, whereas OPGSH had a significantly lower correlation (r = 0.24). There was little seasonal variation in the OP levels for all assays due to the weak seasonality of OP-associated species. Multivariate linear regression models were developed to predict OP measures from the particle composition data. The models indicated that the variabilities in OPDTT and OPAA were attributed to not only the concentrations of metal ions (mainly Fe and Cu) and organic compounds, but also antagonistic metal–organic and metal–metal interactions. OPGSH was sensitive to the change in water-soluble Cu and brown carbon (BrC), a proxy for ambient humic-like substances.

scholarly journals Characterization and comparison of PM<sub>2.5</sub> oxidative potential assessed by two acellular assays

2020 ◽  
Vol 20 (9) ◽  
pp. 5197-5210 ◽  
Author(s):  
Dong Gao ◽  
Krystal J. Godri Pollitt ◽  
James A. Mulholland ◽  
Armistead G. Russell ◽  
Rodney J. Weber
Keyword(s):  
Metal Ions ◽  
Water Soluble ◽  
Metal Species ◽  
Urban Site ◽  
Chemical Components ◽  
Linear Regression Models ◽  
Oxidative Potential ◽  
Metal Interactions ◽  
Metal Metal

Abstract. The capability of ambient particles to generate in vivo reactive oxygen species (ROS), called oxidative potential (OP), is a potential metric for evaluating the health effects of particulate matter (PM) and is supported by several recent epidemiological investigations. Studies using various types of OP assays differ in their sensitivities to varying PM chemical components. In this study, we systematically compared two health-relevant acellular OP assays that track the depletion of antioxidants or reductant surrogates: (i) the synthetic respiratory-tract lining fluid (RTLF) assay that tracks the depletion of ascorbic acid (AA) and glutathione (GSH) and (ii) the dithiothreitol (DTT) assay that tracks the depletion of DTT. Yearlong daily samples were collected at an urban site in Atlanta, GA (Jefferson Street), during 2017, and both DTT and RTLF assays were performed to measure the OP of water-soluble PM2.5 components. PM2.5 mass and major chemical components, including metals, ions, and organic and elemental carbon were also analyzed. Correlation analysis found that OP as measured by the DTT and AA depletion (OPDTT and OPAA, respectively) were correlated with both organics and some water-soluble metal species, whereas that from the GSH depletion (OPGSH) was exclusively sensitive to water-soluble Cu. These OP assays were moderately correlated with each other due to the common contribution from metal ions. OPDTT and OPAA were moderately correlated with PM2.5 mass with Pearson's r=0.55 and 0.56, respectively, whereas OPGSH exhibited a lower correlation (r=0.24). There was little seasonal variation in the OP levels for all assays due to the weak seasonality of OP-associated species. Multivariate linear regression models were developed to predict OP measures from the particle composition data. Variability in OPDTT and OPAA were not only attributed to the concentrations of metal ions (mainly Fe and Cu) and organic compounds but also to antagonistic metal–organic and metal–metal interactions. OPGSH was sensitive to the change in water-soluble Cu and brown carbon (BrC), a proxy for ambient humic-like substances.

PM-induced oxidative potential: Two years measurements and source apportionment, on a seasonal basis, in Athens, Greece

2021 ◽  
Author(s):  
Despina Paraskevopoulou ◽  
George Grivas ◽  
Aikaterini Bougiatioti ◽  
Iasonas Stavroulas ◽  
Maria Tsagkaraki ◽  
...  
Keyword(s):  
Eastern Mediterranean ◽  
Water Soluble ◽  
Automated System ◽  
Chemical Components ◽  
Oxidative Potential ◽  
Wood Burning ◽  
Fine Aerosol ◽  
Short Period ◽  
Seasonal Basis

&lt;p&gt;PM-induced oxidative stress has been proposed as a primary mechanism in cardiovascular and respiratory diseases, as well as premature death. Consequently, a variety of in vitro and in vivo assays have been developed in order to estimate the oxidative potential of ambient PM (Particulate matter), including the acellular assay of DTT (dithiothreitol), which is used in the present study. Athens, Greece is representative of air masses arriving over Eastern Mediterranean, highlighting the effect of long-range aerosol transportation and intense local emissions, such as wood burning for domestic heating purposes during the coldest period of the year.&amp;#160;&lt;/p&gt;&lt;p&gt;Most studies of aerosol oxidative potential (OP) cover a short period of time, while in this study the OP was measured during two years (2016-2018), in parallel with other PM chemical components, in order to identify the sources of aerosol OP. Fine aerosol fraction (PM&lt;sub&gt;2.5&lt;/sub&gt;, diameter &lt; 2.5 &amp;#956;m) was collected, using quartz fibre filters and low-volume samplers, in the centre of Athens city.&lt;/p&gt;&lt;p&gt;An innovative semi-automated system was used for the determination of PM water soluble oxidative potential, following the approach of Fang et al. (2015). Concurrent estimation of inorganic and organic aerosol components&amp;#8217; concentrations was accomplished through Ion chromatography, Aerosol Chemical Speciation Monitor, Aethalometer and OC/EC analyser. Additionally, the samples were further analyzed by Inductively coupled plasma mass spectrometry for major and trace water-soluble metal concentrations. Principal component analysis and Positive Matrix Factorization are applied to identify the sources of fine aerosol at the studied site in Athens, and determine the contribution of each source to aerosol OP, on a seasonal basis&lt;/p&gt;&lt;p&gt;As expected, OP presented higher values during wintertime, when wood burning appeared to be the dominant source of aerosol. These results agree with previous studies, indicating that the combustion is the major source of water-soluble OP, both as primary and secondary emission (Paraskevopulou et al. 2019). Whereas during summer, the current study reveals, for the first time, the significant impact of water-soluble metals in aerosol toxicity during the warmest period of the year, over the studied area. The aforementioned combination of various PM chemical parameters leads to a scarce identification of various aerosol OP sources on a temporal basis, in the area of Eastern Mediterranean.&lt;/p&gt;

scholarly journals A semi-automated system for quantifying the oxidative potential of ambient particles in aqueous extracts using the dithiothreitol (DTT) assay: results from the Southeastern Center for Air Pollution and Epidemiology (SCAPE)

2014 ◽  
Vol 7 (7) ◽  
pp. 7245-7279 ◽  
Author(s):  
T. Fang ◽  
V. Verma ◽  
H. Guo ◽  
L. E. King ◽  
E. S. Edgerton ◽  
...  
Keyword(s):  
Air Pollution ◽  
Large Scale ◽  
Limit Of Detection ◽  
Water Soluble ◽  
Automated System ◽  
Oxidative Potential ◽  
Data Set ◽  
Ambient Particles ◽  
Southeastern Us

Abstract. A variety of methods are used to measure the capability of particulate matter (PM) to catalytically generate reactive oxygen species (ROS) in vivo, also defined as the aerosol oxidative potential. A widely used measure of aerosol oxidative potential is the dithiothreitol (DTT) assay, which monitors the depletion of DTT (a surrogate for cellular antioxidants) as catalyzed by the redox-active species in PM. However, a major constraint in the routine use of the DTT assay for integrating it with the large-scale health studies is its labor-intensive and time-consuming protocol. To specifically address this concern, we have developed a semi-automated system for quantifying the oxidative potential of aerosol liquid extracts using the DTT assay. The system, capable of unattended analysis at one sample per hour, has a high analytical precision (Coefficient of Variation of 12% for standards, 4% for ambient samples), and reasonably low limit of detection (0.31 nmol min−1). Comparison of the automated approach with the manual method conducted on ambient samples yielded good agreement (slope = 1.08 ± 0.12, r2 = 0.92, N = 9). The system was utilized for the Southeastern Center for Air Pollution and Epidemiology (SCAPE) to generate an extensive data set on DTT activity of ambient particles collected from contrasting environments (urban, road-side, and rural) in the southeastern US. We find that water-soluble PM2.5 DTT activity on a per air volume basis was spatially uniform and often well correlated with PM2.5 mass (r = 0.49 to 0.88), suggesting regional sources contributing to the PM oxidative potential in southeast US. However, the greater heterogeneity in the intrinsic DTT activity (per PM mass basis) across seasons indicates variability in the DTT activity associated with aerosols from sources that vary with season. Although developed for the DTT assay, the instrument can also be used to determine oxidative potential with other acellular assays.

scholarly journals Redox activity and chemical speciation of size fractioned PM in the communities of the Los Angeles – Long Beach Harbor

2008 ◽  
Vol 8 (3) ◽  
pp. 11643-11672 ◽  
Author(s):  
S. Hu ◽  
A. Polidori ◽  
M. Arhami ◽  
M. M. Shafer ◽  
J. J. Schauer ◽  
...  
Keyword(s):  
Los Angeles ◽  
Regression Models ◽  
Inorganic Ions ◽  
Water Soluble ◽  
Redox Activity ◽  
Urban Site ◽  
Long Beach ◽  
Linear Regression Models ◽  
Free System

Abstract. In this study, two different types of assays were used to quantitatively measure the redox activity of PM and to examine its intrinsic toxicity: 1) in vitro exposure to rat alveolar macrophage (AM) cells using dichlorofluorescin diacetate (DCFH-DA) as the fluorescent probe (macrophage ROS assay), and: 2) consumption of dithiothreitol (DTT) in a cell-free system (DTT assay). Coarse (PM10–2.5), accumulation (PM2.5–0.25), and quasi-ultrafine (quasi-UF, PM0.25) mode particles were collected weekly at five sampling sites in the Los Angeles-Long Beach Harbor and at one site near the University of Southern California campus (urban site). All PM samples were analyzed for organic (total and water-soluble) and elemental carbon, organic species, inorganic ions, and total and water-soluble elements. Quasi-UF mode particles showed the highest redox activity at all Long Beach sites (on both a per-mass and per-air volume basis). A significant association (R2=0.61) was observed between the two assays, indicating that macrophage ROS and DTT levels are affected at least partially by similar PM species. Relatively small variation was observed for the DTT measurements across all size fractions and sites, whereas macrophage ROS levels showed more significant ranges across the three different particle size modes and throughout the sites (coefficients of variation, or CVs, were 0.35, 0.24 and 0.53 for quasi-UF, accumulation, and coarse mode particles, respectively). Association between the PM constituents and the redox activity was further investigated using multiple linear regression models. The results showed that OC was the most important component influencing the DTT activity of PM samples. The variability of macrophage ROS was explained by changes in OC concentrations and water-soluble vanadium (probably originating from ship emissions – bunker oil combustion). The multiple regression models were used to predict the average diurnal macrophage ROS and DTT levels as a function of the OC concentration at one of the sampling sites.

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

Atmosphere ◽  
2019 ◽  
Vol 10 (10) ◽  
pp. 626 ◽  
Author(s):  
Pietrogrande ◽  
Russo ◽  
Zagatti
Keyword(s):  
Rural Areas ◽  
Active Species ◽  
Water Soluble ◽  
Traffic Emissions ◽  
Fuel Oil ◽  
Anthropogenic Sources ◽  
Chemical Components ◽  
Aerosol Formation ◽  
Oxidative Potential ◽  
Redox Active

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.

scholarly journals Comparison between five acellular oxidative potential measurement assays performed with detailed chemistry on PM<sub>10</sub> samples from the city of Chamonix (France)

2017 ◽  
Author(s):  
Aude Calas ◽  
Gaëlle Uzu ◽  
Frank J. Kelly ◽  
Stephan Houdier ◽  
Jean M. F. Martins ◽  
...  
Keyword(s):  
Ascorbic Acid ◽  
Chemical Species ◽  
Chemical Characterization ◽  
Sampling Period ◽  
Linear Regression Models ◽  
Oxidative Potential ◽  
Potential Measurement ◽  
Detailed Chemistry ◽  
Adverse Health Outcomes

Abstract. Many studies have demonstrated associations between exposure to ambient particulate matter (PM) and adverse health outcomes in humans that can be explained by PM capacity to induce oxidative stress in vivo. Thus, assays have been developed to quantify the oxidative potential (OP) of PM as a more refined exposure metric than PM mass alone. Only a small number of studies have compared different acellular OP measurements for a given set of ambient PM samples. Yet, fewer studies have compared different assays over a year long period and with detailed chemical characterization of ambient PM. In this study, we report on seasonal variations of the dithiothreitol (DTT), ascorbic acid (AA), electron spin resonance (ESR) and the respiratory tract lining fluid (RTLF, composed of the reduced glutathione (GSH) and ascorbic acid (ASC)) assays over a one year period in which 100 samples were analysed. A detailed PM10 characterization allowed univariate and multivariate regression analyses in order to obtain further insight into groups of chemical species that drive OP measurements. Our results show that most of the OP assays were strongly inter-correlated over the sampling year but also these correlations differed when considering specific sampling periods (cold vs war). All acellular assays are correlated with a significant number of chemical species when considering univariate correlations, especially for the DTT assay. Evidence is also presented of a seasonal contrast over the sampling period with significantly higher OP values during winter for the DTT, AA, GSH and ASC assays, which were assigned to biomass burning species by the multiple linear regression models. The ESR assay clearly differs from the other tests as it did not show seasonal dynamics and presented weaker correlations with other assays and chemical species.

scholarly journals A semi-automated system for quantifying the oxidative potential of ambient particles in aqueous extracts using the dithiothreitol (DTT) assay: results from the Southeastern Center for Air Pollution and Epidemiology (SCAPE)

2015 ◽  
Vol 8 (1) ◽  
pp. 471-482 ◽  
Author(s):  
T. Fang ◽  
V. Verma ◽  
H. Guo ◽  
L. E. King ◽  
E. S. Edgerton ◽  
...  
Keyword(s):  
Air Pollution ◽  
Large Scale ◽  
Limit Of Detection ◽  
Water Soluble ◽  
Automated System ◽  
Oxidative Potential ◽  
Data Set ◽  
Ambient Particles ◽  
Southeastern Us

Abstract. A variety of methods are used to measure the capability of particulate matter (PM) to catalytically generate reactive oxygen species (ROS) in vivo, also defined as the aerosol oxidative potential. A widely used measure of aerosol oxidative potential is the dithiothreitol (DTT) assay, which monitors the depletion of DTT (a surrogate for cellular antioxidants) as catalyzed by the redox-active species in PM. However, a major constraint in the routine use of the DTT assay for integrating it with large-scale health studies is its labor-intensive and time-consuming protocol. To specifically address this concern, we have developed a semi-automated system for quantifying the oxidative potential of aerosol liquid extracts using the DTT assay. The system, capable of unattended analysis at one sample per hour, has a high analytical precision (coefficient of variation of 15% for positive control, 4% for ambient samples) and reasonably low limit of detection (0.31 nmol min−1). Comparison of the automated approach with the manual method conducted on ambient samples yielded good agreement (slope = 1.08 ± 0.12, r2 = 0.92, N = 9). The system was utilized for the Southeastern Center for Air Pollution &amp; Epidemiology (SCAPE) to generate an extensive data set on DTT activity of ambient particles collected from contrasting environments (urban, roadside, and rural) in the southeastern US. We find that water-soluble PM2.5 DTT activity on a per-air-volume basis was spatially uniform and often well correlated with PM2.5 mass (r = 0.49 to 0.88), suggesting regional sources contributing to the PM oxidative potential in the southeastern US. The correlation may also suggest a mechanistic explanation (oxidative stress) for observed PM2.5 mass-health associations. The heterogeneity in the intrinsic DTT activity (per-PM-mass basis) across seasons indicates variability in the DTT activity associated with aerosols from sources that vary with season. Although developed for the DTT assay, the instrument can also be used to determine oxidative potential with other acellular assays.

scholarly journals A method for measuring total aerosol oxidative potential (OP) with the dithiothreitol (DTT) assay and comparisons between an urban and roadside site of water-soluble and total OP

2017 ◽  
Vol 10 (8) ◽  
pp. 2821-2835 ◽  
Author(s):  
Dong Gao ◽  
Ting Fang ◽  
Vishal Verma ◽  
Linghan Zeng ◽  
Rodney J. Weber
Keyword(s):  
Pure Water ◽  
High Volume ◽  
Water Soluble ◽  
Urban Site ◽  
Georgia Tech ◽  
Oxidative Potential ◽  
The Third ◽  
Analytical System ◽  
Solid Aerosol

Abstract. An automated analytical system was developed for measuring the oxidative potential (OP) with the dithiothreitol (DTT) assay of filter extracts that include both water-soluble and water-insoluble (solid) aerosol species. Three approaches for measuring total oxidative potential were compared. These include using methanol as the solvent with (1) and without (2) filtering the extract, followed by removing the solvent and reconstituting with water, and (3) extraction in pure water and performing the OP analysis in the extraction vial with the filter. The water extraction method (the third approach, with filter remaining in the vial) generally yielded the highest DTT responses with better precision (coefficient of variation of 1–5 %) and was correlated with a greater number of other aerosol components. Because no organic solvents were used, which must be mostly eliminated prior to DTT analysis, it was easiest to automate by modifying an automated analytical system for measuring water-soluble OP developed by Fang et al. (2015). Therefore, the third method was applied to the field study for the determination of total OP. Daily 23 h filter samples were collected simultaneously at a roadside (RS) and a representative urban (Georgia Tech, GT) site for two 1-month study periods, and both water-soluble (OPWS-DTT) and total (OPTotal-DTT) OP were measured. Using PM2. 5 (aerodynamic diameter  <  2.5 µm) high-volume samplers with quartz filters, the OPWS-DTT-to-OPTotal-DTT ratio at the urban site was 65 % with a correlation coefficient (r) of 0.71 (N  =  35; p value  <  0.01), compared to a ratio of 62 % and r = 0. 56 (N  =  31; p value  <  0.01) at the roadside site. The same DTT analyses were performed, and similar results were found using particle composition monitors (flow rate of 16.7 L min−1) with Teflon filters. Comparison of measurements between sites showed only slightly higher levels of both OPWS-DTT and OPTotal-DTT at the RS site, indicating both OPWS-DTT and OPTotal-DTT were largely spatially homogeneous. These results are consistent with roadway emissions as sources of DTT-quantified PM2. 5 OP and indicate that both soluble and insoluble aerosol components contributing to OP are largely secondary.

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