Neeraj Rastogi

Cytotoxic and proinflammatory effects of ambient and source-related particulate matter (PM) in relation to the production of reactive oxygen species (ROS) and cytokine adsorption by particles

The composition of airborne particulate matter (PM) varies widely depending on its source, and recent studies have suggested that particle-associated adverse health effects are related to particle composition. The objective of this study was to compare the biological/toxicological effects of different source-related PM. Specifically, we investigated the biological/toxicological effects of standard reference materials (SRMs): non-ferrous dust (PD-1, industrial), urban PM (UPM, SRM1648a), and diesel PM (DPM, SRM2975), and ambient PM2.5 (PM with an aerodynamic diameter <2.5 µm) collected at an urban site (Toronto, Canada). The dithiothreitol assay was used to measure the redox activity of the particles. Human alveolar epithelial cells (A549) were exposed to a range of concentrations (10–1000 µg/ml) of total PM, and the respective water-soluble and insoluble fractions, for 24u2009h. Biological responses were then evaluated in terms of cytotoxicity and interleukin (IL)-8 release, and compared with the PM composition and redox activity. We demonstrated that transition metal-enriched PD-1 exhibited the greatest cytotoxic effect (LD50 values of 100–400 µg/ml vs. >1000 µg/ml for the SRM1648a, SRM2975, and ambient PM2.5). Similarly, the PM-induced release of IL-8 was greatest for PD-1 (~6–9u2009ng/ml vs. ~1.5–3u2009ng/ml for others). These endpoints were more responsive to metals as compared with compared with secondary inorganic ions and organic compounds. Interestingly, we demonstrated a high degree of adsorption of IL-8 to the various SRMs and ambient PM2.5, and subsequently derived a new correction method to aid in interpretation of these data. These characteristics likely impart differential effects toward the toxic and immune effects of PM.

Chemical characteristics of PM2.5 at a source region of biomass burning emissions: Evidence for secondary aerosol formation

A systematic study on the chemical characteristics of ambient PM2.5, collected during October-2011 to March-2012 from a source region (Patiala: 30.2°N, 76.3°E; 250 m amsl) of biomass burning emissions in the Indo-Gangetic Plain (IGP), exhibit pronounced diurnal variability in mass concentrations of PM2.5, NO3(-), NH4(+), K(+), OC, and EC with ~30-300% higher concentrations in the nighttime samples. The average WSOC/OC and SO4(2-)/PM2.5 ratios for the daytime (~0.65, and 0.18, respectively) and nighttime (0.45, and 0.12, respectively) samples provide evidence for secondary organic and SO4(2-) aerosol formation during the daytime. Formation of secondary NO3(-) is also evident from higher NH4NO3 concentrations associated with lower temperature and higher relative humidity conditions. The scattering species (SO4(2-) + NO3(-) + OC) contribute ~50% to PM2.5 mass during October-March whereas absorbing species (EC) contribute only ~4% in October-February and subsequently increases to ~10% in March, indicating significance of these species in regional radiative forcing.

Characterization of soluble iron in urban aerosols using near‐real time data

[1]xa0We present the first near-real time (12 min) measurements of fine particle (PM2.5) water soluble ferrous iron (WS_Fe(II)) measured in two urban settings: Dearborn Michigan, and Atlanta, Georgia. A new approach was used to measure WS_Fe(II) involving a Particle-into-Liquid Sampler (PILS) coupled to a liquid waveguide capillary cell (LWCC) and UV/VIS spectrometer. We found no clear diurnal trends in WS_Fe(II) at any urban site studied. High temporal variability, however, was observed at all urban sites, where concentrations often changed from the method limit of detection (4.6 ng m−3) to approximately 300 to 400 ng m−3, lasting only a few hours. These transient events predominately occurred during times of low wind speeds and appeared to be from local sources or processes. In Atlanta, several WS_Fe(II) events were associated with sulfate plumes, and highest WS_Fe(II) concentrations were found in plumes of highest apparent aerosol acidity. At all locations studied, WS_Fe(II) was poorly correlated (R2 < 0.34) with light-absorbing aerosol, indicating no direct linkage between mobile source emissions and enhanced WS_Fe(II) concentrations. WS_Fe(II) measured within a prescribed forest-burn was strongly correlated with water soluble potassium (R2 = 0.88; WS_Fe(II)/WS_K = 15 mg/g), pointing to biomass burning as a source of WS_Fe(II); however, peak concentrations within the fire were low compared to transient events observed at the urban sites. Overall, WS_Fe(II) temporal trends for these urban sites consisted of low background concentrations with periodic short duration transient events that appear to be linked to unique industrial emissions or atmospheric processing of industrial emissions that form WS_Fe(II).

The combined effects of physicochemical properties of size-fractionated ambient particulate matter on in vitro toxicity in human A549 lung epithelial cells

Epidemiological and toxicological studies have suggested that the health effects associated with exposure to particulate matter (PM) are related to the different physicochemical properties of PM. These effects occur through the initiation of differential cellular responses including: the induction of antioxidant defenses, proinflammatory responses, and ultimately cell death. The main objective of this study was to investigate the effects of size-fractionated ambient PM on epithelial cells in relation to their physicochemical properties. Concentrated ambient PM was collected on filters for three size fractions: coarse (aerodynamic diameter [AD] 2.5–10 μm), fine (0.15–2.5 μm), and quasi-ultrafine (<0.2 μm), near a busy street in Toronto, Ontario, Canada. Filters were extracted and analyzed for chemical composition and redox activity. Chemical analyses showed that the coarse, fine, and quasi-ultrafine particles were comprised primarily of metals, water-soluble species, and organic compounds, respectively. The highest redox activity was observed for fine PM. After exposure of A549 cells to PM (10–100 μg/ml) for 4 h, activation of antioxidant, proinflammatory and cytotoxic responses were assessed by determining the expression of heme oxygenase (HMOX-1, mRNA), interleukin-8 (IL-8, mRNA), and metabolic activity of the cells, respectively. All three size fractions induced mass-dependent antioxidant, proinflammatory, and cytotoxic responses to different degrees. Quasi-ultrafine PM caused significant induction of HMOX-1 at the lowest exposure dose. Correlation analyses with chemical components suggested that the biological responses correlated mainly with transition metals and organic compounds for coarse and fine PM and with organic compounds for quasi-ultrafine PM. Overall, the observed biological responses appeared to be related to the combined effects of size and chemical composition and thus both of these physicochemical properties should be considered when explaining PM toxicity.

Comparative cardiopulmonary effects of size-fractionated airborne particulate matter

Context: Strong epidemiological evidence exists linking particulate matter (PM) exposures with hospital admissions of individuals for cardiopulmonary symptoms. The PM size is important in influencing the extent of infiltration into the respiratory tract and systemic circulation and directs the differential physiological impacts. Objective: To investigate the differential effects of the quasi-ultrafine (PM0.2), fine (PM0.15-2.5), and coarse PM (PM2.5-10) size fractions on pulmonary and cardiac function. Methods: Female BALB/c mice were exposed to HEPA-filtered laboratory air or concentrated coarse, fine, or quasi-ultrafine PM using Harvard Ambient Particle Concentrators in conjunction with our nose-only exposure system. These exposures were conducted as part of the “Health Effects of Aerosols in Toronto (HEAT)” campaign. Following a 4u2009h exposure, mice underwent assessment of respiratory function and recording of electrocardiograms using the flexiVent® system. Results: Exposure to coarse and fine PM resulted in a significant reduction in quasistatic compliance of the lung. Baseline total respiratory resistance and maximum responsiveness to methacholine were augmented after coarse PM exposures but were not affected by quasi-ultrafine PM exposures. In contrast, quasi-ultrafine PM alone had a significant effect on heart rate and in reducing heart rate variability. Conclusion: These findings indicate that coarse and fine PM influence lung function and airways responsiveness, while ultrafine PM can perturb cardiac function. This study supports the hypothesis that coarse and fine PM exerts its predominant physiologic effects at the site of deposition in the airways, whereas ultrafine PM likely crosses the alveolar epithelial barrier into the systemic circulation to affect cardiovascular function.

Atmospheric 210Pb and 7Be in ambient aerosols over low‐ and high‐altitude sites in semiarid region: Temporal variability and transport processes

[1]xa0Time series measurements of 210Pb and 7Be made on ambient aerosols, collected from a low-altitude urban site (Ahmedabad, 23.0°N, 72.6°E, 49 m asl) and a high-altitude station (Mt. Abu, 24.6°N, 72.7°E, 1680 m asl) located in a high-dust semiarid region of western India, reveal characteristic pattern of temporal variability consistent over three years (2000–2002). The relatively high concentrations of 210Pb (>1 mBq m−3) during wintertime (November–February) are dominated by continental air masses from the northeast; whereas lower values during the summer months (April–May) and southwest monsoon season (June–August) are associated with (southwesterly) maritime air. The concentration of 210Pb in individual rain events at Ahmedabad, collected during the southwest monsoon for the same three-year period, also exhibits large variability (range of 3–367 mBq L−1; volume-weighted mean of 74 mBq L−1). This first set of data on the simultaneous measurements in rain and aerosols from a semiarid region is useful in deriving scavenging ratio (SR = 290) of 210Pb. On the basis of data for the three consecutive years (2000–2002), we find that both dry and wet deposition fluxes of 210Pb center around 2–4 mBq cm−2 a−1, suggesting relative dominance of dry deposition in a semiarid region. When used in conjunction with 210Pb, 7Be provides information on the vertical mixing of air masses. During the dry season (January–May and September–December), abundances of 7Be and 210Pb (mBq m−3) in ambient aerosols over Ahmedabad (7Be, 1.9 ± 0.1 to 6.0 ± 0.3; 210Pb, 0.32 ± 0.03 to 1.9 ± 0.2) and Mt. Abu (7Be, 3.8 ± 0.2 to 7.6 ± 0.3; 210Pb, 0.39 ± 0.05 to 1.8 ± 0.2) do not show any covariance, suggesting their usefulness as independent tracers of air masses and pollutants transport. Assuming literature-based constant 222Rn flux and measured abundance of 210Pb in aerosols, a model-based approach has provided a simple way to ascertain residence time of tropospheric aerosols, varying from ∼5 days during the dry season and ∼2 days in the wet season. These results attempt to fill a major existing gap for the south Asian region under Global Atmospheric Watch program.

Physical Characterization of the University of Toronto Coarse, Fine, and Ultrafine High-Volume Particle Concentrator Systems

Particle concentrators allow exposure to controlled levels of concentrated ambient particulate matter (PM) over a broad range of concentrations. The performance of these systems can be influenced by the physicochemical characteristics of PM and so it is vital to characterize the concentrators at a given site. The quasi-ultrafine PM (<0.2 μm), fine PM (0.15–2.5 μm), and coarse PM (2.5–10 μm) concentrators at the Southern Ontario Center for Atmospheric Aerosol Research (SOCAAR), University of Toronto, were characterized as a part of the “Health Effects of Aerosols in Toronto (HEAT)” campaign held during February–March, 2010. The full size distributions of ambient and concentrated particles were simultaneously measured in terms of number, surface area, and volume using high time-resolution instruments. Examination of the complete size distribution, including the unconcentrated particles beyond the cutpoints of the concentrator systems, revealed that particles in the unconcentrated size ranges made significant contributions to the particle number and surface area present in the concentrated airstreams of fine and coarse concentrators. Further transients in the ambient ultrafine particle concentrations were evident as dampened signals in these concentrated airstreams. The ultrafine concentrator exhibited a significant size shift when the ambient particle size distribution had a mode ≤30 nm. Overall the fine and coarse concentrators provided a reasonable concentrated reproduction of the ambient PM mass while questions remain regarding the representativeness of the ultrafine concentrator. Copyright 2012 American Association for Aerosol Research

Characterization and radiative impact of dust aerosols over northwestern part of India: a case study during a severe dust storm

The present study focused on examining the impact of a severe dust storm (DS) on aerosol properties over Patiala (30.33°N, 76.4°E), a site located in the northwestern part of India during 20th–23rd March, 2012. On 20th March, average PM10 mass concentration increased abruptly from 182 to 817xa0µgxa0m−3 along with significant increase in the number density of coarser particles (diameter >0.45xa0µm). During DS, spectral aerosol optical depth (AOD) increases significantly with more increase at longer wavelengths resulting in weak wavelength dependence (AOD at 380xa0nm increases by ~210xa0% and at 870xa0nm by ~270xa0% on 20th March). Significant decrease in Ångström exponent (AE; α380–870) from 0.56 to 0.11 and fine-mode fraction (FMF; PM2.5/PM10) from 0.49 to 0.25 indicates dominance of coarser particles over the station. Net short wave (SW) radiation flux has been decreased by ~20xa0% and single scattering albedo (SSA675) has been increased from 0.86 (19th March) to 0.90 (20th March). This observation is attributed to additional loading of scattering type aerosols on arrival of DS. Wavelength dependence of SSA reverses during DS and it increases with wavelength due to dominance of coarse-mode particles. Atmospheric aerosol radiative forcing (ATM ARF) during DS ranged from +45 to +77xa0Wxa0m−2, consequently heating the lower atmosphere up to 2.2xa0Kxa0day−1. Significant atmospheric heating rate due to severe dust storm may affect the regional atmospheric dynamics and hence the climate system.

Seasonality in size-segregated ionic composition of ambient particulate pollutants over the Indo-Gangetic Plain: Source apportionment using PMF

Size-segregated particulate pollutants (PM<0.95, PM0.95-1.5, PM1.5-3.0, PM3.0-7.2 and PM>7.2) were collected over Patiala (30.33°N, 76.40°E; 250xa0m amsl), a semi-urban city located in northwestern Indo-Gangetic Plain (IGP), during October, 2012 to September, 2013. Mass concentration of total suspended particulates (TSP), derived by summation of particulate (aerosol) mass in different size range, varied from 88 to 387xa0μgxa0m-3 with highest mass concentration (∼55% of total mass) in submicron size (PM<0.95) during the entire study period, which broadly reflects relative higher contribution of various anthropogenic sources (emissions from biomass and bio-fuel burning, vehicles, thermal power plants, etc) to ambient particles. Concentration of SO42-, NO3-, NH4+, K+ and Ca2+ exhibited large variability ranging from 0.52 to 40, 0.20 to 19, 0.14 to 12, 0.06 to 5.3 and 0.08 to 5.6xa0μgxa0m-3, respectively, in different size ranges with varying size distribution for most of the species, except NH4+. A strong linear correlation (rxa0=xa00.97) between (SO42-xa0+xa0NO3-) and (K+xa0+xa0NH4+) concentrations has been observed in submicron particles collected in different seasons, suggesting the formation of secondary inorganic salts. However, relatively poor correlation is observed in higher size ranges where significant correlation between (SO42-xa0+xa0NO3-) and (Ca2+xa0+xa0Mg2+) has been observed. These observations indicate the acid neutralization by dust in coarser modes of particles. Chemical composition of submicron particulates (PM<0.95) in different seasons as well as for whole year was used to identify PM sources through the application of Positive Matrix Factorization (PMF, version 5.0) model. Based on annual data, PMF analyses suggests that six source factors namely biomass burning emission (24%), vehicular emission (22%), secondary organic aerosols (20%), power plant emission (13%), secondary inorganic aerosols (12%) and mineral dust (9%) contribute to PM<0.95 loading over the study region. Such studies are important in dispersion modeling, health impact assessment, and planning of pollution mitigation strategies.

Characterization of the University of Toronto Concentrated Aerosol Particle Exposure Facility (CAPEF)—Effects on Fine and Ultrafine Nonrefractory Aerosol Composition

Virtual impactor-based particle concentrators have been developed to enable the study of biological mechanisms and dose-response relationships of particulate matter (PM) inhalation. The Concentrated Aerosol Particle Exposure Facility (CAPEF) at the University of Toronto houses the Harvard School of Public Health designed coarse, fine, and quasi-ultrafine particle concentrators for such studies. Characterization of the concentration of the nonrefractory components of ambient particles was carried out in the winter of 2010. The fine concentrator shows higher mass concentration factors for ambient sulfate than for semi-volatile components, as measured using an Aerodyne aerosol mass spectrometer (AMS). The change in composition is based on the relative size distributions of particulate sulfate, which, compared to particulate organic and nitrate, is more dominant in larger particles more efficiently concentrated due to the physical characteristics of the virtual impactors. The ultrafine concentrator, which requires aqueous condensational growth of particles prior to concentration, shows a large enhancement in organic mass both for ambient particles and for laboratory-generated ammonium sulfate and ammonium nitrate particles added to filtered outdoor air. As suggested previously, changes in the organic mass spectrum and size distributions are consistent with addition of organic mass through reactions of water-soluble volatile organic compounds. Coagulation of particles or droplet coalescence may also account for some of the observed increase in organic mass and nitrate may be lost due to volatilization. While such effects are unlikely to affect refractory species, increased attention should be given to the effect of condensational growth on the composition of concentrated ultrafine particles. Copyright 2012 American Association for Aerosol Research