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Heart disease is a major killer in western societies; coronary artery disease and atherosclerosis are important contributors to this mortality. Atherosclerosis in mice with a deleted apoE gene (apoE −/−) is accelerated by exposure to ambient ultrafine particles (UFP) which are particles smaller than 180 nm in diameter. UFP contain organic components that are pro-oxidant and may cause or aggravate heart disease. Could removal of these organic constituents mitigate adverse cardiovascular effects? ApoE −/− mice were exposed to concentrated UFP (CAP), CAP from which organic constituents were removed by thermal denuding (deCAP) or purified air (controls) for 5 hr/day, 4 days/week for 8 weeks. Heart rate (HR), heart rate variability (HRV), biomarkers of oxidative stress and the sizes of arterial plaques were measured. Adverse effects were seen in CAP-exposed mice (increased size of arterial plaque, increased oxidative stress and decreased HRV, compared to controls). Adverse effects were not observed in deCAP-exposed mice. Removal of organic constituents from ambient particles resulted in significant reduction of toxic cardiovascular effects of air pollution exposure. [ABSTRACT FROM AUTHOR]

The aim was to investigate respiratory symptoms, lung function and nasal airflow development among a cohort of children who were exposed to particulate air pollution. We used questionnaires, spirometry and rhinomanometry, while central-monitored PM10concentrations were used for exposure assessment. We initially examined 1046 children (10–12 year old) in the heavily polluted town of Ptolemaida, Greece, and 379 children in the cleaner town of Grevena (control group). We re-evaluated 312 of the former and 119 of the latter after 19 years. PM10concentrations were above permissible levels in Ptolemaida during all study period. At both visits, nasal flow was significantly lower in the study sample. At the follow-up visit, 34.3 % had severe nasal obstruction (< 500 ml/s) and 38.5 % reported chronic nasal symptoms. Spirometric parameters did not differ compared to the control group. Particulate air pollution had significant and negative effects on nasal but not on lung function development. [ABSTRACT FROM PUBLISHER]

In this paper, we report results on commuter's exposure to particulate matter (PM). Particle number concentrations (PNC) were recorded simultaneously inside and outside the cabin of a vehicle during 45 field trips in and around Paris (France) between 2016 and 2017. For a fixed ventilation setting, the impacts of external parameters were investigated to assess commuter's exposure for a wide range of traffic conditions, including the presence of tunnels and ring road, various times during the day, the specific driving routes, different road types and vehicle speeds. Overall, our results indicate that roadway tunnels represent the worse situation for commuters resulting in the highest concentrations outside and inside the car cabin, followed by the ring road around Paris. Comparisons with a previous study undertaken in Paris and its inner and outer suburbs in 2007 reveal drastic reduction of Particle Number Concentrations (PNC) in the car cabin over this period of 10 years. More stringent emission regulations, changes in the vehicle fleet and development of low emission zones explain these promising results. Similar trends found in the recent literature for different countries corroborate the present findings. • Commuter's exposure in terms of PNC in Paris and its suburbs are reported. • Roles of road infrastructures, vehicle speeds and driving routes on PNC are discussed. • Tunnels and ring road strongly affect exposure of commuters. • Particles inside the car cabin were mostly in the fine and ultrafine ranges. • Commuter's exposure decreased by ~40% between 2007 and 2017. [ABSTRACT FROM AUTHOR]

Abstract: In this study, two drugs, terbutaline sulphate (TS) and ipratropium bromide (IB), were micronized by means of a CO2-based aerosol solvent extraction system (ASES). TS and IB particles with albumin as additive were also precipitated in order to improve the powder flow behavior in an accelerating air flow. Albumin is considered an inactive ingredient for FDA-approved drugs and is endogenous to the lung. The addition of albumin affected the particle morphology resulting in improved aerosolization properties. In the present study, ASES experiments were conducted using a mixed solvent of ethanol/dimethylformamide (EtOH/DMF) for the micronization of TS and pure DMF was used as solvent for IB. For the respirable TS, optimum processing conditions were at about 100 bar and 50 °C. For the IB particles, the conditions were at 200 bar and 40 °C. The aerosol characteristics of all precipitated drug particles in this work were analyzed by comparing the particle size distribution (PSD) and the associated mass median aerodynamic diameter (MMAD) measured by scanning electron microscopy (SEM) to those obtained from Aerodynamic Particle Sizer (APS) and from the Micro-orifice Uniform Deposit Impactor (MOUDI). The results indicate that the TS and IB particles with albumin are less cohesive and less agglomerated in air flow, thus leading to more effective and consistent lung deposition. [Copyright &y& Elsevier]

Secondary aerosols comprise a major fraction of fine particulate matter (PM2.5) in all parts of the country, during all seasons, and times of day. The most abundant secondary species include sulfate, nitrate, ammonium, and secondary organic aerosols (SOAs). The relative abundance of each species varies in space and time as a function of meteorology, source emissions strength and type, thermodynamics, and atmospheric processing. Transport of secondary aerosols from upwind locations can contribute significantly at downwind receptor sites, especially regionally in the eastern United States, and across a given urbanized area, such as in Los Angeles. Processes governing the formation of the inorganic secondary species (sulfate, nitrate, and ammonium) are fairly well understood, although the occurrence of nucleation bursts initiated with the formation of ultrafine sulfuric acid particles observed regionally on clean days in the eastern United States was unexpected. Because of the complex nature of organic material in air, much is still to be learned about the sources, formation, and even spatial and temporal distributions of SOAs. For example, a considerable fraction of ambient organic PM is oxidized organic species, many of which still need to be identified, quantified, and their sources and formation mechanisms determined. Furthermore, significant uncertainty (approaching 50% or more) is associated with estimating the SOA fraction of organic material in air with current methods. This review summarizes the findings of the Supersites Program and related studies addressing secondary particulate matter (PM), including spatial and temporal variations of secondary PM and its precursor species, data and methods for determining the primary and secondary fractions of PM mass, and findings on the anthropogenic and natural fractions of secondary PM. [ABSTRACT FROM AUTHOR]

The U.S. Environmental Protection Agency (EPA) established the Particulate Matter (PM) Supersites Program to provide key stakeholders (government and private sector) with significantly improved information needed to develop effective and efficient strategies for reducing PM on urban and regional scales. All Supersites projects developed and evaluated methods and instruments, and significant advances have been made and applied within these programs to yield new insights to our understanding of PM accumulation in air as well as improved source-receptor relationships. The tested methods include a variety of continuous and semicontinuous instruments typically with a time resolution of an hour or less. These methods often overcome many of the limitations associated with measuring atmospheric PM mass concentrations by daily filter-based methods (e.g., potential positive or negative sampling artifacts). Semicontinuous coarse and ultrafine mass measurement methods also were developed and evaluated. Other semicontinuous monitors tested measured the major components of PM such as nitrate, sulfate, ammonium, organic and elemental carbon, trace elements, and water content of the aerosol as well as methods for other physical properties of PM, such as number concentration, size distribution, and particle density. Particle mass spectrometers, although unlikely to be used in national routine monitoring networks in the foreseeable future because of their complex technical requirements and cost, are mentioned here because of the wealth of new information they provide on the size-resolved chemical composition of atmospheric particles on a near continuous basis. Particle mass spectrometers likely represent the greatest advancement in PM measurement technology during the last decade. The improvements in time resolution achieved by the reported semicontinuous methods have proven to be especially useful in characterizing ambient PM, and are becoming essential in allowing scientists to investigate sources of particulate pollution and to probe into the dynamics and mechanisms of aerosol formation in the atmosphere. [ABSTRACT FROM AUTHOR]

Motor vehicle exhaust emissions are known to exacerbate asthma and other respiratory diseases. Several studies have demonstrated significant associations between living near highly trafficked roadways and increased incidence of asthma and increased severity of asthma-related symptoms, medication usage, and physician visits. This study tested the hypotheses that (1) exposure to particulate matter (PM) near a heavily trafficked Los Angeles freeway would enhance inflammatory and allergic responses in ovalbumin (OVA)-sensitized BALB/c mice compared to sensitized, clean air controls, and (2) there would be differences in response at two distances downwind of heavily traveled freeways because of greater toxicity of PM closest to the freeway. An ambient particle concentrator was used to expose ovalbumin (OVA)-treated BALB/c mice to purified air, to concentrated fine ambient particles, and to concentrated ultrafine airborne particles (CAPs) at 2 distances, 50 m and 150 m, downwind of a roadway that is impacted by emissions from both heavy-duty diesel and light duty gasoline vehicles. Tissues and biological fluids from the mice were analyzed after exposures for 5 days/wk in 2 consecutive weeks. The biomarkers of allergic or inflammatory responses that were assessed included cytokines released by Type 2 T-helper cells (interleukin [IL]-5 and IL-13), OVA-specific immunoglobulin E (IgE), OVA-specific immunoglobulin G1 (IgG1), and pulmonary infiltration of polymorphonuclear leukocytes and eosinophils. IL-5 and IgG1 were significantly increased in mice exposed to CAPs 50 m downwind of the road, compared to responses in mice exposed to purified air, providing evidence of allergic response. No significant increases in allergy-related responses were observed in mice exposed to CAPs 150 m downwind of the road. The biological responses at the 50-m site were significantly associated with organic and elemental carbon components of fine and ultrafine particles (p ≤ .05). The primary source of these contaminants at the roadway sites was motor vehicle emissions, suggesting that particulate matter from motor vehicle fuel combustion could exert adjuvant effects and promote the development of allergic airway diseases. [ABSTRACT FROM AUTHOR]

Abstract: Epidemiologic studies have shown associations between ambient particulate matter (PM) and adverse health outcomes including increased mortality, emergency room visits, and time lost from school and work. The mechanisms of PM-related health effects are still incompletely understood, but a hypothesis under investigation is that many of the adverse health effects may derive from oxidative stress, initiated by the formation of reactive oxygen species (ROS) within affected cells. While the adverse effects from PM have historically been associated with the airborne concentration of PM and more recently fine-particle PM, we considered it relevant to develop an assay to quantitatively measure the ability of PM to catalyze ROS generation as the initial step in the induction of oxidative stress. This ability of PM could then be related to different sources, chemical composition, and physical and spatial/temporal characteristics in the ambient environment. The measurement of ROS-forming ability in relation to sources and other factors will have potential relevance to control of redox-active PM. If oxidative stress represents a relevant mechanism of toxicity from PM, the measurement of redox activity represents a first step in the elucidation of the subsequent downstream processes. We have developed an assay for PM redox activity, utilizing the reduction of oxygen by dithiothreitol which serves as an electron source. We have found that PM will catalyze the reduction of oxygen and have examined the distribution and chemical characteristics of the redox activity of PM fractions collected in different sites in the Los Angeles Basin. Samples of concentrated coarse, fine, and ultrafine PM, obtained with aerosol concentrators, were studied with regard to their chemical properties and redox activity. Redox activity was highest in the ultrafine fraction, in agreement with results indicating ultrafines were the most potent toward inducing that heme oxygenase expression and depleting intracellular glutathione, which has relevance to induction of oxidative stress. Comparison of the redox activity with chemical composition showed a reasonable correlation of redox activity with elemental carbon (), organic carbon (), and with benzo[ghi]perylene (), consistent with species typically found in mobile emission sources. [Copyright &y& Elsevier]

Epidemiologic research has shown increases in adverse cardiovascular and respiratory outcomes in relation to mass concentrations of particulate matter (PM) ≤ 2.5 or ≤ 10 μm in diameter (PM2.5, PM10, respectively). In a companion article [Delfino RJ, Sioutas C, Malik S. 2005. Environ Health Perspect 113(8):934–946]), we discuss epidemiologic evidence pointing to underlying components linked to fossil fuel combustion. The causal components driving the PM associations remain to be identified, but emerging evidence on particle size and chemistry has led to some clues. There is sufficient reason to believe that ultrafine particles < 0.1 μm (UFPs) are important because when compared with larger particles, they have order of magnitudes higher particle number concentration and surface area, and larger concentrations of adsorbed or condensed toxic air pollutants (oxidant gases, organic compounds, transition metals) per unit mass. This is supported by evidence of significantly higher in vitro redox activity by UFPs than by larger PM. Although epidemiologic research is needed, exposure assessment issues for UFPs are complex and need to be considered before undertaking investigations of UFP health effects. These issues include high spatial variability, indoor sources, variable infiltration of UFPs from a variety of outside sources, and meteorologic factors leading to high seasonal variability in concentration and composition, including volatility. To address these issues, investigators need to develop as well as validate the analytic technologies required to characterize the physical/chemical nature of UFPs in various environments. In the present review, we provide a detailed discussion of key characteristics of UFPs, their sources and formation mechanisms, and methodologic approaches to assessing population exposures. [ABSTRACT FROM AUTHOR]

Numerous epidemiologic time-series studies have shown generally consistent associations of cardiovascular hospital admissions and mortality with outdoor air pollution, particularly mass concentrations of particulate matter (PM) ≤ 2.5 or ≤ 10 μm in diameter (PM2.5, PM10). Panel studies with repeated measures have supported the time-series results showing associations between PM and risk of cardiac ischemia and arrhythmias, increased blood pressure, decreased heart rate variability, and increased circulating markers of inflammation and thrombosis. The causal components driving the PM associations remain to be identified. Epidemiologic data using pollutant gases and particle characteristics such as particle number concentration and elemental carbon have provided indirect evidence that products of fossil fuel combustion are important. Ultrafine particles < 0.1 μm (UFPs) dominate particle number concentrations and surface area and are therefore capable of carrying large concentrations of adsorbed or condensed toxic air pollutants. It is likely that redox-active components in UFPs from fossil fuel combustion reach cardiovascular target sites. High UFP exposures may lead to systemic inflammation through oxidative stress responses to reactive oxygen species and thereby promote the progression of atherosclerosis and precipitate acute cardiovascular responses ranging from increased blood pressure to myocardial infarction. The next steps in epidemiologic research are to identify more clearly the putative PM casual components and size fractions linked to their sources. To advance this, we discuss in a companion article (Sioutas C, Delfino RJ, Singh M. 2005. Environ Health Perspect 113:947–955) the need for and methods of UFP exposure assessment. [ABSTRACT FROM AUTHOR]

The objectives of this study were to determine whether differences in the size and composition of coarse (2.5-10 µm), fine (< 2.5 µm), and ultrafine (< 0.1 µm) particulate matter (PM) are related to their uptake in macrophages and epithelial cells and their ability to induce oxidative stress. The premise for this study is the increasing awareness that various PM components induce pulmonary inflammation through the generation of oxidative stress. Coarse, fine, and ultrafine particles (UFPs) were collected by ambient particle concentrators in the Los Angeles basin in California and used to study their chemical composition in parallel with assays for generation of reactive oxygen species (ROS) and ability to induce oxidative stress in macrophages and epithelial cells. UFPs were most potent toward inducing cellular heme oxygenase-1 (HO-1) expression and depleting intracellular glutathione. HO-1 expression, a sensitive marker for oxidative stress, is directly correlated with the high organic carbon and polycyclic aromatic hydrocarbon (PAH) content of UFPs. The dithiothreitol (DTT) assay, a quantitative measure of in vitro ROS formation, was correlated with PAH content and HO-1 expression. UFPs also had the highest ROS activity in the DTT assay. Because the small size of UFPs allows better tissue penetration, we used electron microscopy to study subcellular localization. UFPs and, to a lesser extent, fine particles, localize in mitochondria, where they induce major structural damage. This may contribute to oxidative stress. Our studies demonstrate that the increased biological potency of UFPs is related to the content of redox cycling organic chemicals and their ability to damage mitochondria. [ABSTRACT FROM AUTHOR]

This article describes a systematic evaluation of factors affecting the stability of the performance of Harvard ambient fine-particle concentrators, an essential requirement for controlled animal and human exposure studies that utilize these technologies. Phenomenological problems during the operation of the concentrator, including pressure drop increase and decrease in concentration enrichment, were statistically correlated with ambient air parameters such as temperature, relative humidity, PM[sub 2.5] mass concentration, and mass median diameter. The normalized hourly pressure drop across the concentrator was strongly associated (R[sup 2] = .81) with the product of ambient PM[sub 2.5] mass concentration and the difference between the vapor pressure downstream of the impactor nozzle and the saturation vapor pressure at the adiabatic expansion temperature (i.e., the temperature of the aerosol immediately downstream of the virtual impactors). From multiple regression analysis, the average enrichment factor was predicted reasonably well (R[sup 2] = .67) by aerosol mass median diameter and the normalized hourly pressure drop. Based on these results, we can anticipate in any given day whether an exposure study can be conducted without a considerable increase in the concentrator pressure drop, which might lead to an abrupt or premature termination of the exposure. As particle mass concentration and ambient dewpoint are the two main parameters responsible for raising the pressure drop across the concentrator, efforts should be made to either desiccate the ambient aerosol at days of high dewpoints, or to dilute the ambient PM at days of high concentrations, prior to drawing the aerosol through the virtual impactors. The latter approach is recommended on days of severe ambient pollution conditions because it is simpler and also makes it possible to maintain the appropriate concentration level delivered to the exposure chamber. [ABSTRACT FROM AUTHOR]

This study investigated the effect of using a stainless steel fibrous filter as the ground electrode of a point-to-plate electrostatic precipitator on particle penetration. The effect of the electrical field on particle penetration was investigated at 4 different filter face velocities (25, 50, 100, and 125 cm/s) for monodisperse PSL and silica particles (size range 0.05-1 m) as well as polydis perse ammonium sulfate, ammonium nitrate, and ultrafine indoor air particles. Particle penetration was greatly reduced by the application of the electrical field. By comparison, the performance of electrically active fibrous filters has been shown to rapidly degrade as particle loading exceeds 2-3 g/m[sup 2]. The effect of particle loading on particle penetration was also investigated at a filter face velocity of 50 cm/s. Particle penetration seemed to slightly decrease with particle loading and was independent of particle size. These results indicated that the accumulation of nonconductive particles up to 15 cm[sup 3]/ m[sup 2] does not create ''back corona,'' which would substantially decrease the collection efficiency of the grounded filter. In conclusion, our experiments suggest that using metal filters as the collector electrodes may be an attractive alternative design for electrostatic precipitators. [ABSTRACT FROM AUTHOR]

We installed a Harvard particle concentrator with PM2.5 size-selective inlet and two virtual impactor stages, in a movable human exposure laboratory located in metropolitan Los Angeles, where ambient PM2.5 is unusually high. The exposure chamber, a modified body plethysmograph of ∼ 2000 L volume, operated at flow near 200 L/min and pressure near 25 cm H[SUB2]O below atmospheric. The concentrator usually delivered seven to nine times the ambient concentration of PM2.5. When necessary, part of its output was diverted through a HEPA filter to control the exposure concentration. Occasionally the concentration factor decreased due to rapid fouling of impactor slits under humid and/or highly polluted ambient conditions. Initial tests with an investigator (healthy male, age 53 yr) at rest in the chamber showed no untoward effects except rare transient mild substernal irritation, brief mild middle ear discomfort from pressure changes upon starting or stopping the concentrator, and occasional ectopic heartbeats (which also occurred apart from the exposures). Maximum in-chamber concentrations exceeded 300 μg/m[SUP3], 30-min average. Subsequently, healthy adult volunteers (2 female, 2 male, age 19-41 yr) completed 2-h resting exposures to ambient PM2.5 at 2-h average concentrations of 148 to 246 μg/m[SUB3], and similar studies with HEPA-filtered air (control condition). No medically significant changes in lung function, symptoms, arterial O[SUB2] saturation, or Holter electrocardiograms (recorded during and for 22 h after exposure in 3 subjects) were observed. We conclude that exposures to concentrated ambient particles are operationally and ethically feasible in metropolitan Los Angeles. Larger scale studies of healthy volunteers, and then of volunteers with respiratory or cardiovascular disease, are planned. [ABSTRACT FROM AUTHOR]

The main goal of this study was to characterize fine particles (e.g., smaller than about 3 mu m) in an automotive machining environment. The Toledo Machining Plant of Chrysler Corporation was selected for this purpose. The effect of local mechanical processes as aerosol sources was a major part of this investigation. To determine the size-dependent mass concentration of particles in the plant, the Micro-Orifice Uniform Deposit Impactor (MOUDI Model 100, MSP Corp., Minneapolis, Minnesota) was used. The MOUDI was placed at central locations in departments with sources inside the plant, so that the obtained information on the size distribution realistically represents the aerosol to which plant workers are exposed. Sampling was conducted over a 4-day period, and during three periods per day, each matching the work shifts. A special effort was made to place the MOUDI at a central location of a department with relatively homogeneous particle sources. The selected sampling sites included welding, grinding, steel machining, and heat treating processes. The average 24-hour mass concentrations of particles smaller than 3.2 mu m in aerodynamic diameter were 167.8, 103.9, 201.7, and 112.7 mu g/m3 for welding, grinding, mild steel, and heat treating processes, respectively. Finally, the mass median diameters of welding, heat treatment, machining, and grinding operations were approximately 0.5, 0.5, 0.6, and 0.8 mu m, respectively. [ABSTRACT FROM AUTHOR]

This paper presents an experimental investigation of the increase in pressure drop with particle loading in Nuclepore filters. The average increase in pressure drop per unit time and particle mass concentration was measured as a function of particle size, density, and hygroscopicity. Two different Nuclepore filter pore diameters were tested (2 and 5 mu m, respectively) at filter face velocities ranging from 4 to 52 cm/s. Our results showed that the increase in the pressure drop with particle loading inversely proportional to the square root of particle specific gravity and depends weakly on particle diameter (to the power of- 0.2). Furthermore, the increase in the pressure drop with particle loading is proportional to the filter face velocity and inversely proportional to the cube of the pore diameter. Particle interception and impaction on the pore edges are the main deposition mechanisms that are responsible for raising the pressure drop over time across the filter, especially for particles having Stokes numbers below 5. Particle deposition due to diffusion inside the pores is important for particles smaller than 0.2 mu m. These observations agree well with previously published studies on particle deposition on the pore edges in Nuclepore filters. Our tests also showed a dramatic decrease in the pressure drop with loading for hygroscopic particles as the relative humidity increases from 10% to 50%. The pressure drop with loading decreases almost inversely proportional to the relative humidity for ammonium sulfate particles. [ABSTRACT FROM AUTHOR]

The performance of the Scanning Mobility Particle Sizer (SMPS, TSI Model 3934) and the Aerodynamic Particle Sizer (APS, TSI Model 3310A) were evaluated to assess their ability to obtain mass concentrations from near real-time particle number concentration measurements made as a function of particle size. Tests were performed by generating monodisperse (polystyrene latex microspheres, 0.05-9.20 mu m) and polydisperse aerosols (potassium sulfate and ammonium nitrate, mass median aerodynamic diameter (MMAD) U 0.16-0.30 mu m) and comparing mass concentrations determined by the SMPS and APS, with concentrations measured gravimetrically on Teflon filters. Previous performance evaluation tests of these instruments has focused primarily on their ability to measure particle number concentrations (Kinney et al. 1991; Wang and Flagan 1990) or mass concentrations of polydisperse aerosols with mass median aerodynamic diameters (MMAD) of about 0.7-2.5 mu m (Peters et al. 1993). Findings from the monodisperse aerosol tests indicate that the mass concentrations obtained by the APS compared similarly to those obtained using the gravimetric method for particle sizes between 0.5-9.2 mu m. Similarly, SMPS measurements were in good agreement with the gravimetric analysis for particle sizes between 0.3-0.5 mu m. However, for particles less than 0.30 mu m, the SMPS overestimated their mass concentrations by a factor of 1.5-1.6. Tests using polydisperse aerosols showed that at particle size ranges from 0.09-0.18 mu m and from 0.18-0.29 mu m, the SMPS also overestimated mass concentrations. [ABSTRACT FROM AUTHOR]

Compares the performance of the tapered element oscillating microbalance (TEOM) method in measuring ambient particulate mass in urban areas with the performance of collocated time-integrated samplers. Relationship between TEOM and federal reference methods; Factors affecting performance; Possibility of large fluctuations. INSET: Implications..

This study investigates the long-term trends of ambient ultrafine particles (UFPs) and associated airborne pollutants in the Los Angeles Basin from 2007 to 2022, focusing on the indirect effects of regulations on UFP levels. The particle number concentration (PNC) of UFPs was compiled from previous studies in the area, and associated co-pollutant data, including nitrogen oxides (NO x), carbon monoxide (CO), elemental carbon (EC), organic carbon (OC), and ozone (O 3), were obtained from the chemical speciation network (CSN) database. Over the study period, a general decrease was noted in the PNC of UFPs, NO x , EC, and OC, except for CO, the concentration trends of which did not exhibit a consistent pattern. UFPs, NO x , EC, and OC were positively correlated, while O 3 had a negative correlation, especially with NO x. Our analysis discerned two distinct sub-periods in pollutant trends: 2007–2015 and 2016–2022. For example, there was an overall decrease in the PNC of UFPs at an annual rate of −850.09 particles/cm3/year. This rate was more pronounced during the first sub-period (2007–2015) at −1814.9 particles/cm3/year and then slowed to −227.21 particles/cm3/year in the second sub-period (2016–2023). The first sub-period (2007–2015) significantly influenced pollutant level changes, exhibiting more pronounced and statistically significant changes than the second sub-period (2016–2022). Since 2016, almost all primary pollutants have stabilized, indicating a reduced impact of current regulations, and emphasizing the need for stricter standards. In addition, the study included an analysis of Vehicle Miles Traveled (VMT) trends from 2007 to 2022 within the Los Angeles Basin. Despite the general increase in VMT, current regulations and cleaner technologies seem to have successfully mitigated the potential increase in increase in PNC. Overall, while a decline in UFPs and co-pollutant levels was observed, the apparent stabilization of these levels underscores the need for more stringent regulatory measures and advanced emission standards. [Display omitted] • UFPs and co-pollutants in LA Basin analyzed (2007–2022). • An overall decrease in the PNC of UFPs due to regulations was observed. • UFPs, NO x , EC, and OC showed a strong positive correlation. • Pollutant levels stabilized post-2016, showing regulatory limitations. • Pollutant levels were controlled despite the overall increase in VMT. [ABSTRACT FROM AUTHOR]

The geopolitical conflict between Russia and Ukraine has disrupted Europe's natural gas supplies, driving up gas prices and leading to a shift towards biomass for residential heating during colder months. This study assessed the consequent air quality and toxicological impacts in Milan, Italy, focusing on fine particulate matter (PM2.5, dp < 2.5 μm) emissions. PM2.5 samples were analyzed for their chemical composition and assessed for their oxidative potential using the dithiothreitol (DTT) assay across three periods reflecting residential heating deployment (RHD): pre-RHD, intra-RHD, and post-RHD periods. During the intra-RHD period, PM2.5 levels were significantly higher than those in other periods, with concentrations reaching 57.94 ± 7.57 μg/m3, indicating a deterioration in air quality. Moreover, levoglucosan was 9.2 times higher during the intra-RHD period compared to the pre-RHD period, correlating with elevated levels of elemental carbon (EC) and polycyclic aromatic hydrocarbons (PAHs). These findings were compared with previous local studies before the conflict, underscoring a significant rise in biomass-related emissions. DTT assay levels during the intra-RHD were 2.1 times higher than those observed during the same period in 2022, strongly correlating with biomass burning emissions. Our findings highlight the necessity for policies to mitigate the indirect health effects of increased biomass burning emissions due to the energy crisis triggered by the geopolitical conflict. [ABSTRACT FROM AUTHOR]

In the present study, we identified the sources of four redox-active metals, including Iron (Fe), Chromium (Cr), Cupper (Cu), and Manganese (Mn) and quantified the contribution of these sources to PM 2.5 concentrations in central Los Angeles, California, by employing time-resolved measurements (i.e., a time resolution of 2 h) with a recently developed online metal monitor and Positive Matrix Factorization (PMF). Size distribution of ambient PM (14 nm–10 μm) was measured using the Scanning Mobility Particle Sizer (SMPS) and Optical Particle Sizer (OPS). Auxiliary variables were also collected, including elemental (EC) and organic carbon (OC), gaseous pollutants (NO 2 and O 3 ), meteorological parameters (including relative humidity (RH) and temperature), and traffic data (for heavy- (HDVs) and light-duty vehicles (LDVs)). A 4-factor solution was found to be optimum for the chemically-speciated dataset, whereas a 5-factor solution appeared to be most plausible for the size distribution data. The factors included fresh traffic, soil/road dust, urban background aerosol, secondary aerosol, and nucleation (only resolved for the size distribution data). Fresh traffic was the major contributor to Fe and Cu concentrations, whereas Cr was mostly found in the urban background aerosol (reflecting a mixture of small local sources as well as aged traffic emissions), and Mn mostly came from both soil/road dust and was to a lesser degree found in urban background aerosol. Secondary aerosol did not contribute to the concentrations of any of these metals, but was associated with very high loading of OC, as expected. Even though the urban background aerosol and secondary aerosol appeared to be characterized by “aged” particles and have a rather homogeneous spatial distribution, the reactions and processes involved in their formation are entirely different. Our results provide insights into the sources of redox-active metals in central Los Angeles. They also underscore the benefits of novel measurement techniques for PM-bound metals, which could enhance our understanding of the sources of atmospheric aerosols by providing us with measurements with finer time resolutions that otherwise would not have been possible using traditional filter-based measurement techniques. [ABSTRACT FROM AUTHOR]

Exposure to ambient particulate matter (PM) has been associated with the onset of neurodevelopmental and neurodegenerative disorders, but the mechanism of toxicity remains unclear. To gain insight into this neurotoxicity, this study sought to examine global gene expression changes caused by exposure to ambient ultrafine PM. Microarray analysis was performed on primary human neurons derived from fetal brain tissue after a 24 h exposure to 20 μg/mL of ambient ultrafine particles. We found a majority of the changes in noncoding RNAs, which are involved in epigenetic regulation of gene expression, and thereby could impact the expression of several other protein coding gene targets. Although neurons from biologically different lot numbers were used, we found a significant increase in the expression of metallothionein 1A and 1F in all samples after exposure to particulate matter as confirmed by quantitative PCR. These metallothionein 1 proteins are responsible for neuroprotection after exposure to environmental insult but prolonged induction can be toxic. Epidemiological studies have reported that in utero exposure to ultrafine PM not only leads to neurodevelopmental and behavioral abnormalities, but may also predispose the progeny to neurodegenerative disease later in life by genetic imprinting. Our results pinpoint some of the PM-induced genetic changes that may underlie these findings. [ABSTRACT FROM AUTHOR]

BACKGROUND: Rodent models for urban air pollution show consistent induction of inflammatory responses in major brain regions. However, the initial impact of air pollution particulate material on olfactory gateways has not been reported. OBJECTIVE: We evaluated the olfactory neuroepithelium (OE) and brain regional responses to a nanosized subfraction of urban traffic ultrafine particulate matter (nPM, < 200 nm) in vivo, ex vivo, and in vitro. METHODS: Adult mice were exposed to reaerosolized nPM for 5, 20, and 45 cumulative hours over 3 weeks. The OE, the olfactory bulb (OB), the cerebral cortex, and the cerebellum were analyzed for oxidative stress and inflammatory responses. Acute responses of the OE to liquid nPM suspensions were studied with ex vivo and primary OE cultures. RESULTS: After exposure to nPM, the OE and OB had rapid increases of 4-hydroxy-2-nonenal (4-HNE) and 3-nitrotyrosine (3-NT) protein adducts, whereas the cerebral cortex and cerebellum did not respond at any time. All brain regions showed increased levels of tumor necrosis factor-α (TNFα) protein by 45 hr, with earlier induction of TNFα mRNA in OE and OB. These responses corresponded to in vitro OE and mixed glial responses, with rapid induction of nitrite and inducible nitric oxide synthase (iNOS), followed by induction of TNFα. CONCLUSIONS: These findings show the differential time course of oxidative stress and inflammatory responses to nPM between the OE and the brain. Slow cumulative transport of inhaled nPM into the brain may contribute to delayed responses of proximal and distal brain regions, with potential input from systemic factors. CITATION: Cheng H, Saffari A, Sioutas C, Forman HJ, Morgan TE, Finch CE. 2016. Nanoscale particulate matter from urban traffic rapidly induces oxidative stress and inflammation in olfactory epithelium with concomitant effects on brain. Environ Health Perspect 124:1537-1546; http://dx.doi.org/10.1289/EHP134 [ABSTRACT FROM AUTHOR]

Background: The mechanisms by which genetic and environmental factors interact to promote asthma remain unclear. Both the IL‐4 receptor alpha chain R576 (IL‐4RαR576) variant and Notch4 license asthmatic lung inflammation by allergens and ambient pollutant particles by subverting lung regulatory T (Treg) cells in an IL‐6‐dependent manner. Objective: We examined the interaction between IL‐4RαR576 and Notch4 in promoting asthmatic inflammation. Methods: Peripheral blood mononuclear cells (PBMCs) of asthmatics were analyzed for T helper type 2 cytokine production and Notch4 expression on Treg cells as a function of IL4RR576 allele. The capacity of IL‐4RαR576 to upregulate Notch4 expression on Treg cells to promote severe allergic airway inflammation was further analyzed in genetic mouse models. Results: Asthmatics carrying the IL4RR576 allele had increased Notch4 expression on their circulating Treg cells as a function of disease severity and serum IL‐6. Mice harboring the Il4raR576 allele exhibited increased Notch4‐dependent allergic airway inflammation that was inhibited upon Treg cell‐specific Notch4 deletion or treatment with an anti‐Notch4 antibody. Signaling via IL‐4RαR576 upregulated the expression in lung Treg cells of Notch4 and its downstream mediators Yap1 and beta‐catenin, leading to exacerbated lung inflammation. This upregulation was dependent on growth factor receptor‐bound protein 2 (GRB2) and IL‐6 receptor. Conclusion: These results identify an IL‐4RαR576‐regulated GRB2‐IL‐6‐Notch4 circuit that promotes asthma severity by subverting lung Treg cell function. [ABSTRACT FROM AUTHOR]

Background: Air pollution particulate matter (PM) is strongly associated with risks of accelerated cognitive decline, dementia and Alzheimer's disease. Ambient PM batches have variable neurotoxicity by collection site and season, which limits replicability of findings within and between research groups for analysis of mechanisms and interventions. Diesel exhaust particles (DEP) offer a replicable model that we define in further detail.Objective: Define dose- and time course neurotoxic responses of mice to DEP from the National Institute of Science and Technology (NIST) for neurotoxic responses shared by DEP and ambient PM.Methods: For dose-response, adult C57BL/6 male mice were exposed to 0, 25, 50, and 100μg/m3 of re-aerosolized DEP (NIST SRM 2975) for 5 h. Then, mice were exposed to 100μg/m3 DEP for 5, 100, and 200 h and assayed for amyloid-β peptides, inflammation, oxidative damage, and microglial activity and morphology.Results: DEP exposure at 100μg/m3 for 5 h, but not lower doses, caused oxidative damage, complement and microglia activation in cerebral cortex and corpus callosum. Longer DEP exposure for 8 weeks/200 h caused further oxidative damage, increased soluble Aβ, white matter injury, and microglial soma enlargement that differed by cortical layer.Conclusion: Exposure to 100μg/m3 DEP NIST SRM 2975 caused robust neurotoxic responses that are shared with prior studies using DEP or ambient PM0.2. DEP provides a replicable model to study neurotoxic mechanisms of ambient PM and interventions relevant to cognitive decline and dementia. [ABSTRACT FROM AUTHOR]

Cloud condensation nuclei (CCN), i.e., aerosol particles that undergo theoretically unlimited growth when exposed to a certain (low) water vapor supersaturation and grow to large droplets, play an important role in cloud microphysics and are crucial for the second indirect effect of aerosols on global climate. The activation and growth of particles depends not only on their size but also on their chemical composition, which determines whether a particle of a certain size will actually be activated to grow to a cloud droplet. In order to analyze the chemical composition of individual CCN, the CCN must first be separated from non-CCN particles. For this purpose, we coupled a CCN-VACES (Cloud Condensation Nuclei-Versatile Aerosol Concentration Enrichment System, a modification of the original VACES), which activates CCN at defined supersaturations and enriches their concentrations by a factor of 17 to a single particle mass spectrometer (in our case a Laser Ablation Aerosol Particle Time of Flight mass spectrometer; LAAPTOF). Supersaturations in the CCN-VACES are set to 0.035%, 0.054%, 0.1% and 0.6%, respectively. The CCN present in an aerosol flow entering the CCN-VACES are activated and grow to droplets. Droplets > 1.5 µm are enriched in the exit flow and pass directly into the LAAPTOF where the chemical composition of the droplets originating from the individual activated CCN is obtained. In this pilot study, where ambient urban aerosol as well as nebulized sea water samples were used as test aerosols, we show that the LAAPTOF is indeed able to provide ion spectra for aqueous droplets and can therefore be used to determine the chemical composition of actually activated CCN in their droplet state. Single ambient CCN were found to contain sometimes highly complex mixtures of different carbonaceous and non-carbonaceous components. Sea water derived CCN show the expected sea salt constituents, but also the presence of organic material. Copyright © 2022 American Association for Aerosol Research [ABSTRACT FROM AUTHOR]

Exposure to ultrafine particles (UFPs) has been associated with multiple adverse health effects. Inhaled UFPs could reach the gastrointestinal tract and influence the composition of the gut microbiome. We have previously shown that oral ingestion of UFPs alters the gut microbiome and promotes intestinal inflammation in hyperlipidemic Ldlr −/− mice. Particulate matter (PM) 2.5 inhalation studies have also demonstrated microbiome shifts in normolipidemic C57BL/6 mice. However, it is not known whether changes in microbiome precede or follow inflammatory effects in the intestinal mucosa. We hypothesized that inhaled UFPs modulate the gut microbiome prior to the development of intestinal inflammation. We studied the effects of UFP inhalation on the gut microbiome and intestinal mucosa in two hyperlipidemic mouse models (ApoE −/− mice and Ldlr −/− mice) and normolipidemic C57BL/6 mice. Mice were exposed to PM in the ultrafine-size range by inhalation for 6 h a day, 3 times a week for 10 weeks at a concentration of 300–350 μg/m3.16S rRNA gene sequencing was performed to characterize sequential changes in the fecal microbiome during exposures, and changes in the intestinal microbiome at the end. PM exposure led to progressive differentiation of the microbiota over time, associated with increased fecal microbial richness and evenness, altered microbial composition, and differentially abundant microbes by week 10 depending on the mouse model. Cross-sectional analysis of the small intestinal microbiome at week 10 showed significant changes in α-diversity, β-diversity, and abundances of individual microbial taxa in the two hyperlipidemic models. These alterations of the intestinal microbiome were not accompanied, and therefore could not be caused, by increased intestinal inflammation as determined by histological analysis of small and large intestine, cytokine gene expression, and levels of fecal lipocalin. In conclusion, 10-week inhalation exposures to UFPs induced taxonomic changes in the microbiome of various animal models in the absence of intestinal inflammation. • Gut microbiome changes caused by PM inhalation occur in the absence of inflammation. • Inhalation of ultrafine PM induced effects different to inhalation of larger PM. • Fat metabolism is a determinant in microbiome composition changes induced by PM. [ABSTRACT FROM AUTHOR]

Particulate matter emissions from a large sample (N = 88) of in-use line-haul freight locomotives were measured in the Alameda Corridor, located near the ports of Los Angeles and Long Beach. Emission factors for black carbon (BC), particle number (PN), fine particulate mass (PM 2.5 ), and lung-deposited particle surface area (LDSA) were computed based on 1 Hz measurements of the rise and fall of particulate matter and CO 2 concentrations as the locomotives passed the sampling location. We include LDSA emission factors as relevant for near-source human exposures. Mean emission factors ± standard deviations were 0.9 ± 0.5 g kg −1 fuel consumed for BC, (2.1 ± 1.5) × 10 16 # kg −1 for PN, 1.6 ± 1.3 g kg −1 for PM 2.5 , and (2.2 ± 1.7) × 10 13 μm 2 kg −1 for LDSA. Emission factors for individual trains were slightly skewed, with the dirtiest 10% of trains responsible for 20%, 24%, 28%, and 27% of total BC, PN, PM 2.5 , and LDSA emissions, respectively. The relative importance of high-emitters is therefore lower for these locomotives relative to previously reported diesel truck emissions. BC versus PN emissions from individual locomotives were found to be anti-correlated, suggesting that the highest emitters of particle numbers are the lowest emitters of black carbon. Using results presented here along with previous measurements, we compared for freight trains versus diesel trucks the amount of BC emissions associated with pulling an intermodal freight container over a given distance. This assumption-dependent comparison showed that in most cases locomotives emit less BC per container hauled than diesel trucks. However, continual decreases in diesel truck BC means that unless emissions from locomotives are decreased in the near future, emissions associated with hauling a container could become lower for diesel trucks than locomotives. [ABSTRACT FROM AUTHOR]

In this study, we developed two online monitors for total organic carbon (TOC) and water-soluble organic carbon (WSOC) measurements in fine (d p < 2.5 μm) and coarse (2.5 μm < d p < 10 μm) particulate matter (PM), respectively. Their performance has been evaluated in laboratory and field tests to demonstrate the feasibility of using these monitors to measure near real-time concentrations, with consideration of their potential for being employed in long-term measurements. The fine PM collection setup was equipped with a versatile aerosol concentration enrichment system (VACES) connected to an aerosol-into-liquid-sampler (AILS), whereas two virtual impactors (VIs) in tandem with a modified BioSampler were used to collect coarse PM. These particle collection setups were in tandem with a Sievers M9 TOC analyzer to read TOC and WSOC concentrations in aqueous samples hourly. The average hourly TOC concentration measured by our developed monitors in fine and coarse PM were 5.17 ± 2.41 and 0.92 ± 0.29 μg/m³, respectively. In addition, our TOC readings showed good agreement and were comparable with those quantified using Sunset Lab EC/OC analyzer operating in parallel as a reference. Furthermore, we conducted field tests to produce diurnal profiles of fine PM-bound WSOC, which can show the effects of ambient temperature on maximum values in the nighttime chemistry of the winter, as well as on increased photochemical activities in afternoon peaks during the summer. According to our experimental campaign, WSOC mean values during the study period (3.07 μg/m³ for the winter and 2.7 μg/m³ for the summer) were in a comparable range with those of earlier studies in Los Angeles. Overall, our results corroborate the performance of our developed monitors in near real-time measurements of TOC and WSOC, which can be employed for future source apportionment studies in Los Angeles and other areas, aiding in understanding the health impacts of different pollution sources. [Display omitted] • We developed online monitors to measure TOC and WSOC in fine and coarse ambient PM. • A reference Sunset Lab EC/OC analyzer was used to confirm OC measurements. • The results corroborate monitors' performance to measure online TOC and WSOC. • Nighttime chemistry in the winter was associated with high TOC and WSOC levels. • Summer peak hours of WSOC occurred in the afternoon due to photochemical reactions. [ABSTRACT FROM AUTHOR]

In-transit microenvironments experience elevated levels of vehicle-related pollutants such as ultrafine particles. However, in-vehicle particle number concentrations are frequently lower than on-road concentrations due to particle losses inside vehicles. Particle concentration reduction occurs due to a complicated interplay between a vehicle's air-exchange rate (AER), which determines particle influx rate, and particle losses due to surfaces and the in-cabin air filter. Accurate determination of inside-to-outside particle concentration ratios is best made under realistic aerodynamic and AER conditions because these ratios and AER are determined by vehicle speed and ventilation preference, in addition to vehicle characteristics such as age. In this study, 6 vehicles were tested at 76 combinations of driving speeds, ventilation conditions (i.e., outside air or recirculation), and fan settings. Under recirculation conditions, particle number attenuation (number reduction for 10-1000 nm particles) averaged 0.83 ± 0.13 and was strongly negatively correlated with increasing AER, which in turn depended on speed and the age of the vehicle. Under outside air conditions, attenuation averaged 0.33 ±0.10 and primarily decreased at higher fan settings that increased AER. In general, in-cabin particle number reductions did not vary strongly with particle size, and cabin filters exhibited low removal efficiencies. [ABSTRACT FROM AUTHOR]

The in-vehicle microenvironment is an important route of exposure to traffic-related pollutants particularly ultrafine particles. However, significant particle losses can occur under conditions of low air exchange rate (AER) when windows are closed and air is recirculating. AERs are lower for newer vehicles and at lower speeds. Despite the importance of AER in affecting in-vehicle particle exposures-few studies have characterized-AER and all have tested only a small number of cars. One reason for this is the difficulty in measuring AER with trarer gases such as SF6 the most common method. We developed a simplified yet accurate method for determining AER using the occupants' own production of CO2 a convenient compound to measure. By measuring initial CO2 build-up rates and equilibrium values of CO2 at fixed speeds, AER was calculated for 59 vehides representative of California's fleet AER measurements correlated and agreed well with the largest other study conducted (R² = 0.83). Multivariable models captured 7096 of the variability in observed AER using only age, mileage, manufacturer, and speed. These results will be useful to exposure and epidemiological studies since all model variable values are easily obtainable through questionnaire. [ABSTRACT FROM AUTHOR]

Hourly indoor and outdoor fine particulate matter (PM2.5), organic and elemental carbon (OC and EC, respectively), particle number (PN), ozone (O3), carbon monoxide (CO), and nitrogen oxide (NOx) concentrations were measured at two different retirement communities in the Los Angeles, CA, area as part of the Cardiovascular Health and Air Pollution Study. Site A (group 1 [G1]) was operated from July 6 to August 20, 2005 (phase 1 [P1]) and from October 19 to December 10, 2005 (P2), whereas site B (group 2 [G2]) was operated from August 24 to October 15, 2005 (P1), and from January 4 to February 18, 2006 (P2). Overall, the magnitude of indoor and outdoor measurements was similar, probably because of the major influence of outdoor sources on indoor particle and gas levels. However, G2 showed a substantial increase in indoor OC, PN, and PM2.5 between 6:00 and 9:00 a.m., probably from cooking. The contributions of primary and secondary OC (SOA) to measured outdoor OC were estimated from collected OC and EC concentrations using EC as a tracer of primary combustion-generated OC (i.e., "EC tracer method"). The study average outdoor SOA accounted for 40% of outdoor particulate OC (40-45% in the summer and 32-40% in the winter). Air exchange rates (hr-1) and infiltration factors (Finf; dimensionless) at each site were also determined. Estimated Finf and measured particle concentrations were then used in a single compartment mass balance model to assess the contributions of indoor and/or outdoor sources to measured indoor OC, EC, PM2.5, and PN. The average percentage contributions of indoor SOA of outdoor origin to measured indoor OC were ∼35% (during G1P1 and G1P2) and ∼45% (for G2P1 and G2P2). On average, 36% (G2P1) to 44% (G1P1) of measured indoor OC was composed of outdoor-generated primary OC. [ABSTRACT FROM AUTHOR]

Abstract: This study presents the development and field evaluation of a compact high-volume dichotomous sampler (HVDS) that collects coarse and fine particulate matter. The key features of this device is the utilization of a round nozzle virtual impactor with a 50% cutpoint at aerodynamic diameter, operating at a high inlet flow rate with a calculated Reynolds number of approximately . In its primary configuration as tested, the sampler size-fractionates into coarse and fine fractions with a minor flow ratio of 10% (minor/total flow rate), with major and minor flow rates of 900 and , respectively. Performance evaluation for concentration enrichment was conducted with a 4% minor flow ratio ( minor flow) as well. Tests demonstrated near ideal results at both 10% and 4% minor flow ratios, indicating enrichment to be independent of minor flow rates within the range evaluated. Reasonable agreement was found between the new sampler and collocated Partisol and MOUDI for ambient measurements. A tandem virtual impactor super-concentration system was also tested with the virtual impactor followed by a round nozzle virtual impactor and proved to be an efficient system to achieve higher concentration enrichment of ambient particles up to 180 times ambient levels. Investigation of the effect of different ambient parameters like RH and wind speed on coarse PM concentration corroborates results from earlier studies. The HVDS is an effective system to collect coarse and fine PM simultaneously, allowing for comprehensive standard chemical analyses over short sampling intervals. [Copyright &y& Elsevier]

Effective densities of atmospheric aerosols in various locations of the Los Angeles Basin were determined by a DMA-APM technique. Effective density was calculated by comparing voltage distributions of sampled atmospheric aerosols with PSL particles of known density. The five sites chosen for field experiments were: (1) Interstate-710 Freeway, impacted by heavy-duty diesel vehicles; (2) State Route CA-110, open only to gasoline vehicles; (3) Riverside, a receptor site known for secondary particle formation; (4) University of Southern California, a typical urban and industrial environment; and (5) Coast for marine aerosol. The size range selected for this study was from 50 nm to 414 nm. While 50 nm particles exhibited a single effective density multiple effective densities were measured for each of the other particle sizes as significant fractions of these particles are transported from background sources. Regardless of location, 322-414 nm particle effective densities were considerably lower than unity. The lowest effective densities (~0.1 g cm3) were reported for I-710, confirming that diesel combustion aerosols are rich in chain agglomerates with large void spaces. Riverside exhibited high effective densities (~1.2-1.5 g cm3) for 50-202 nm particles, which we hypothesize is due to transformations that occur during advection from Los Angeles. Measurements of diurnal variation of effective density at Riverside support this hypothesis. Overall, our results suggest that effective density declines as the particle mobility diameter increases irrespective of location. Fractal dimensions calculated from average effective densities were lowest for I-710 (Df = 2.41) and CA-110 (Df = 2.54) aerosols, presumably due to the influence of vehicular combustion emission on these sites. By contrast, average fractal dimensions at USC, Riverside and Coast were found to be 2.79, 2.83, and 2.92, respectively. High fractal dimensions at these sites may be the effects of aging, moisture absorption and/or organic vapor condensation on the particles, which fills void space and makes particles more spherical. [ABSTRACT FROM AUTHOR]

Abstract: During the winter of 2005, physicochemical properties of size-fractionated PM10 particles were analyzed next to State Route 110 (Pasadena freeway in Los Angeles, CA, USA), a light-duty vehicle freeway, closed to heavy-duty traffic. We report volatility of ultrafine particles and chemical characteristics in the coarse, accumulation, and ultrafine modes very close to the freeway and at an urban background site. For measurement of mass and chemical composition, the study employed in each location a Micro-Orifice Uniform Deposit Impactor (MOUDI) and a modified high-volume sampler. Both instruments sampled with the same size cutpoints. A tandem differential mobility analyzer (TDMA) was used at the two sampling sites to analyze the semivolatile fraction of the aerosols. Size distributions of the ambient aerosol were measured using a DMA and total number concentration using a condensation particle counter (CPC). In this study, which was a continuation of a campaign during summer 2004, we compared the seasonal, i.e. winter versus summer, and diurnal, i.e. daytime versus evening, variation in PM characteristics in the vicinity of this freeway. Conditions in winter differed most from those in summer during the evening rush-hour traffic, with much lower temperatures in the winter campaign. Diurnal variations in particle volatility were observed, with higher content of volatile material in aerosols sampled in the evenings. Particle number concentrations were also much higher during the evening hours, increasing from 67,000 to 110,000cm−3. The average total number concentration next to the freeway was 80,000cm−3 during the sampling period, which was higher than in summer, when the average was 46,000cm−3. External mixing was observed with increasing nonvolatile fractions for 40, 80, and 120nm particles (39% of particles). In general the volatility increased in the evenings, while the nonvolatile fraction decreased. [Copyright &y& Elsevier]

Particle size distribution measurements of twelve USEPA priority pollutant polycyclic aromatic hydrocarbons (PAHs)—collected in Riverside, California, down to 10 nm aerodynamic diameter (Dp)—observed on integrated nocturnal samples (7:00 p.m.-6:30 a.m.) revealed that between 46 and 100% of the mass of particles in the Aitken size range was found in the 10-18 nm size bin. Particles in this size range have high alveolar deposition efficiency. [ABSTRACT FROM AUTHOR]

In this study, we report a comparison of the results from the differential tapered element oscillating microbalance (TEOM) and a semi-continuous nitrate monitor in an attempt to obtain insights into the dynamics of volatilization from the heated TEOM filter. Measurements were conducted in Claremont, California, a city downwind of Los Angeles and a region of high nitrate concentrations. Field results are compared with that obtained in the laboratory for sampling of pure ammonium nitrate aerosol, and with the vaporization losses predicted by theory. The primary hypothesis that we are testing is that the nitric acid and ammonia gas volatilization from particle-bound ammonium nitrate loaded on the TEOM''s fiber filter occurs over time scales that are longer than the 5-min cycle time for the system. This is important to the use of the Differential TEOM, which utilizes the vaporization measured during alternate 5-min periods as a reference baseline value for its particle mass measurements.Our experiments showed that under ambient conditions, the mass lost from the Differential TEOM tracks well the ambient particulate nitrate concentration. The saturation ratio for nitrate vapor immediately downstream of the filter, calculated at the filter temperature assuming all volatilized mass is ammonium nitrate, ranged from 0.05 to 0.2. By comparison, for laboratory collection of ammonium nitrate aerosol the vaporization reached a maximum value corresponding to a saturation of nitrate vapor downstream of the heated filter. This difference is due to the relatively higher particle concentrations used for the laboratory experiments. For the ambient measurements, the particulate nitrate concentrations were consistently lower than the equilibrium vapor concentration at the TEOM filter temperature. In both cases, the nitrate vaporization is driven by the temperature of the TEOM filter and independent of the pressure drop across the filter. [Copyright &y& Elsevier]

A periodic review of the National Ambient Air Quality Standards for Particulate Matter by the U.S. Environmental Protection Agency (EPA) will assess the standards with respect to levels, particle size,and averaging times. Some members of the scientific community in the United States and Europe have suggested the use of PM1 instead of PM2.5 as the fine particle measurement standard. This proposed standard is intended to reduce the influence of coarse particle sources on PM2.5, because some evidence suggests that PM1-2.5 is dominated by coarse particulate matter (PM) sources. In this study, coarse (PM2.5-10), intermodal (PM1-2.5), and fine (PM2.5) mass concentrations at four different sites are measured with continuous and time-integrated sampling devices. The main objective is to compare variations in these three size ranges while considering the effects of location, sources, weather, wind speed, and wind direction. Results show strong correlations between PM1 and intermodal PM in receptor sites. The contribution of PM1-2.5 to PM2.5 is highest in the summer months, most likely due to enhanced long-range transport. Coarse PM is poorly correlated with intermodal PM. Continuous data suggest that PM1 is growing into PM1-2.5 via complex processes involving stagnation of the aerosol during high relative humidity conditions, followed by advection during daytime hours. [ABSTRACT FROM AUTHOR]

Recent studies that have found increased health effects of atmospheric ultrafine particulate matter (PM) have refocused attention on particle number rather than particle mass concentrations as a relevant measurement of PM pollution. As part of the Southern California Supersite program, ambient particle characteristics were measured over 13 months at three different sites in the eastern portion of the Los Angeles Basin: Riverside, Rubidoux, and Claremont, CA. The sites represent receptor locations that are influenced by local particle sources as well as advection from the more intense particle sources upwind closer to Downtown Los Angeles. An SMPS/APS tandem system was employed to collect continuous particle size distributions, from which particle number and mass concentrations were calculated. An aethalometer provided continuous particulate elemental carbon (EC) concentrations. Results show no meaningful correlation between particle number and mass, indicating that fine particle standards may not be effective in controlling ultrafine concentrations. Diurnal patterns show a morning traffic peak indicated by increases in particle mass, number, and EC. Afternoon periods in the warmer months are characterized by high number counts while mass and EC remain low, suggesting the formation of new particles by photochemistry. Particle mode diameters range from 30 nm up to above 100 nm, a result not seen in most other studies of particle size distributions in other urban or rural areas where mode diameters are generally less than 50 nm. Evidence is presented that the observed ultrafine particle concentrations and size distributions are influenced by long-range advection and photochemical processes as well as vehicular emissions, which have been previously assumed to dominate day-to-day ultrafine particle levels. [ABSTRACT FROM AUTHOR]

Population exposures to ambient particulate matter (PM) have recently received considerable attention due to the association between ambient particle concentrations and mortality. Recent toxicological studies suggest that ultrafine PM (diameter <100 nm) may be responsible for the observed health effects. However, even though ultrafine mass concentrations vary drastically over short time scales in the atmosphere, no monitor currently measures ultrafine PM mass continuously. The need for monitors that can perform ultrafine particle concentration measurement in shorter time intervals is of paramount importance to environmental health, as such a monitor can lead to substantial improvements in population exposure assessment to ambient ultrafine PM. In this study, a modified BAM (Beta Attenuation Monitor) is employed to measure near-ultrafine (i.e., <0.15 μm or PM 0.15 ) particulate mass concentration. The BAM is preceded by a 0.15 μm cutpoint impactor, which is designed to have very low pressure drop. The BAM is operated in a 2 h cycle at a downwind receptor site in the Los Angeles Basin in Claremont. Among the other instruments colocated with the BAM are scanning mobility particle sizer (SMPS), an aerodynamic particle sizer (APS), and a Micro-Orifice Uniform Deposit Impactor (MOUDI). Our results indicate that the PM 0.15 mass concentrations obtained by means of the modified BAM and MOUDI are in excellent agreement. The PM 0.15 SMPS-to-BAM concentration ratio is generally smaller than 1 and follows a rather distinct diurnal profile, with a maximum towards the middle of the day and minima during the early morning and nighttime periods, presumably due to the classification of fractal-structured ultrafine particles in the accumulation mode by the SMPS. The lack of correlation between PM 2.5 and PM 0.15 mass concentrations further corroborates the need for developing monitors such as the modified BAM for the documentation of the short-term variation of ultrafine mass measurements. [ABSTRACT FROM AUTHOR]

BACKGROUND: Exposure to ambient air pollution particulate matter (PM) is associated with increased risk of dementia and accelerated cognitive loss. Vascular contributions to cognitive impairment are well recognized. Chronic cerebral hypoperfusion (CCH) promotes neuroinflammation and blood– brain barrier weakening, which may augment neurotoxic effects of PM. OBJECTIVES: This study examined interactions of nanoscale particulate matter (nPM; fine particulate matter with aerodynamic diameter =200 nm) and CCH secondary to bilateral carotid artery stenosis (BCAS) in a murine model to produce white matter injury. Based on other air pollution interactions, we predicted synergies of nPM with BCAS. METHODS: nPM was collected using a particle sampler near a Los Angeles, California, freeway. Mice were exposed to 10 wk of reaerosolized nPM or filtered air (FA) for 150 h. CCH was induced by BCAS surgery. Mice (C57BL/6J males) were randomized to four exposure paradigms: a) FA, b) nPM, c) FA+BCAS, and d) nPM+BCAS. Behavioral outcomes, white matter injury, glial cell activation, inflammation, and oxidative stress were assessed. RESULTS: The joint nPM+BCAS group exhibited synergistic effects on white matter injury (2.3× the additive nPM and FA+BCAS scores) with greater loss of corpus callosum volume on T2 magnetic resonance imaging (MRI) (30% smaller than FA group). Histochemical analyses suggested potential microglial-specific inflammatory responses with synergistic effects on corpus callosum C5 immunofluorescent density and whole brain nitrate concentrations (2.1× and 3.9× the additive nPM and FA+BCAS effects, respectively) in the joint exposure group. Transcriptomic responses (RNA-Seq) showed greater impact of nPM+BCAS than individual additive effects, consistent with changes in proinflammatory pathways. Although nPM exposure alone did not alter working memory, the nPM+BCAS cohort demonstrated impaired working memory when compared to the FA+BCAS group. DISCUSSION: Our data suggest that nPM and CCH contribute to white matter injury in a synergistic manner in a mouse model. Adverse neurological effects may be aggravated in a susceptible population exposed to air pollution. [ABSTRACT FROM AUTHOR]

This paper presents the field evaluation of a personal cascade impactor sampler (PCIS). PCIS is a miniaturized cascade impactor, consisting of four impaction stages, followed by an after-filter. Particles are separated in the following aerodynamic particle diameter ranges: <0.25, 0.25–0.5, 0.5–1.0, 1.0–2.5 and 2.5–10 μm. The PCIS operates at a flow rate of 9 liters per minute (l/min) using a very high efficiency, battery-operated light pump at a pressure drop of 11 in H2O (2.7 kPa). For field evaluation, the PCIS was collocated with other samplers including the micro-orifice uniform deposit impactor (MOUDI), scanning mobility particle sizer (SMPS) and aerodynamic particle sizer (APS) in Los Angeles and Claremont, CA. PCIS and MOUDI agree very well for coarse particulate matter (PM) (PM2.5−10) mass concentrations. The fine PM (PM2.5) mass as measured by PCIS is in excellent agreement with SMPS–APS measurement (∼1.02 times) and slightly higher (∼1.1 times) than the MOUDI measurements. Time-integrated (size fractionated) PM2.5 mass, inorganic ions (nitrate and sulfate), elemental carbon (EC) and organic carbon (OC) concentrations obtained with PCIS and MOUDI were found to be in very good agreement with few differences in the <0.25 μm size fraction, especially for OC and nitrate measurements. Near-continuous and size fractionated PM2.5 nitrate and total carbon measurements by PCIS and MOUDI using the ADI and Sunset labs monitors are in close agreement for all size fractions, indicating that any differences between MOUDI and PCIS measurements for time-integrated data might be due to artifacts associated with long-term sampling and not to differences in individual cut-points. The performance of the PCIS was also evaluated in wind tunnel tests at wind speeds up to 8 km/h. These tests showed that particle sampling efficiency and separation characteristics of the PCIS are unaffected by the wind speeds for particles up to 10 μm in aerodynamic diameter. [Copyright &y& Elsevier]

Information about health effects from controlled exposure to particulate matter (PM) air pollution is relatively limited but potentially critical in urban locations such as Los Angeles, where abundant mobile sources generate combustion-related particles. Nonsmoking healthy (n = 12) and asthmatic (n = 12) volunteers, age 18-45 yr, were exposed to concentrated ambient particulates (CAP) in the fine (PM 2.5 ) size range at an average concentration of 174 µg/m 3 (range 99-224), and to filtered air (FA). Exposures used a two-stage Harvard virtual-impactor concentrator and whole-body chamber and lasted 2 h with alternating rest-exercise periods. Neither group showed significant (p < .05) changes in spirometry or routine hematologic measurements attributable to CAP exposure, relative to FA. Both groups showed CAP-related decreases of columnar cells in postexposure induced sputum, slight changes in certain mediators of blood coagulability and systemic inflammation, and modest increases in parasympathetic stimulation of heart rate variability. Systolic blood pressure decreased in asthmatics and increased in healthy subjects during CAP exposure relative to FA. Cardiovascular (but not respiratory) symptoms increased slightly with CAP in both groups. In summary, the urban fine PM exposures elicited different biologic endpoints with statistically significant differences between CAP and FA. The observed changes in blood inflammation and heart-rate variability were consistent with systemic (rather than respiratory) effects reported from other laboratory and epidemiologic studies. Further studies involving other biologic endpoints, PM size modes, and risk factors will be needed to clarify these results. [ABSTRACT FROM AUTHOR]

Conventional PM[sub 10] inlets available operate at a flow rate of 16.7 l/min. The purpose of this study was to develop and test a PM[sub 10] inlet designed to operate at 50 l/min to be used with a recently developed continuous coarse particle monitor (Misra et al.). Laboratory tests using polystyrene latex particles established the inlet's 50% cutpoint at 9.5 µm. Further evaluation of PM[sub 10] inlet was performed in a wind tunnel at wind speeds of 3, 8, and 24 km/h. Tests showed that the 50% efficiency cutpoint as well as the very sharp particle separation characteristics of the inlet were maintained at these wind speeds. Field evaluation of the PM[sub 10] inlet was performed in Riverside and Rubidoux, CA. A 2.5 µm cutpoint round nozzle virtual impactor was attached downstream of the developed PM[sub 10] inlet. The Dichotomous PM[sub 10] Partisol Sampler, operating at a flow rate of 16.7 l/min was used as a reference sampler. The Dichotomous Partisol uses an FRM PM[sub 10] inlet operating at 16.7 l/min to remove particles larger than 10 µm in aerodynamic diameter. Commercially available 4.7 cm Teflon filters were used in both the Partisol and the PM[sub 10] inlet to collect particulate matter (PM). Results showed good agreement between coarse PM (2.510 µm) mass concentrations measured by means of the PM[sub 10] inlet and Partisol. Chemical analyses showed excellent agreement between coarse PM concentrations of Al, K, Si, Ca, and Fe obtained by the two samplers. The agreement also persisted for nitrate and sulfate. Finally, the excellent agreement between coarse concentra- tions of the PM[sub 10] inlet and Partisol persisted for wind speeds up to 19 km/h. [ABSTRACT FROM AUTHOR]

In the lower airways, macrophages are important regulators of inflammation and indispensable in their antimicrobial activities. Thus, air pollution particles, which modulate airway macrophage host defenses may, in susceptible individuals, increase severity of inflammatory and infectious disease. In the present study, size fractionated, ultrafine (UF), fine (PM[SUB0.1-2.5]), and coarse (PM[SUB2.5-10) particulate matter (PM) were collected from 2 urban sites in the Netherlands, and were compared for effects on human alveolar macrophages (AM). Inflammatory cytokine production, phagocytosis, and expression of phagocyte receptor CD11b were assessed in particle-exposed AM. Interleukin (IL)-6 levels induced by PM[SUB2.5-10] (20411 pg/mL) were > 10-fold higher than induced by PM[SUB0.1-2.5] (1781 pg/mL). Levels induced by PM[SUB0.1-2.5] were 2- to 3-fold higher than induced by UF (770 pg/mL) when cells were exposed to the same particle mass. Cytokine induction by the PM was inhibited by antibody to CD14 and required the presence of serum for optimal stimulation, implying that bacterial products or endotoxin were stimulatory moieties in both coarse and fine particulate matter. Phagocytosis of opsonized yeast was inhibited by coarse more than by fine PM, as was yeast-induced oxidative burst. Coarse particles dereased CD11b expression more than fine PM. The UF did not affect these functions. Taken together, these results suggest that PM recognition by human AM involves receptors evolved to recognize microbial cell structures, and that microbial products preferentially found in the coarse particle fraction of PM may be involved in inflammatory events and decreased pulmonary defenses associated with exposure to pollution particles. [ABSTRACT FROM AUTHOR]

A high-efficiency coarse-mode particle concentrator (CPC) has been developed and evaluated in the laboratory as well as validated in the field experiments at the University of Southern California, in Los Angeles, CA, and in Bilthoven, the Netherlands. The CPC operates with a total intake flow of 1000 LPM. The minor flow rate, containing the concentrated coarse-mode particles (2.5-10 μm), can be adjusted from 33 to 120 LPM in order to enrich ambient coarse PM concentrations by a factor of 8-30, depending on the desirable exposure level and flow rate needed. The laboratory evaluation of the virtual impactors at 3 minor flow rates (3.3, 7, and 10 LPM, respectively) indicated that extremely efficient concentration enrichment was obtained for 2.5-10 μm particles. In the field tests, the CPC operated at a minor flow rate of 33 LPM and the mass obtained was compared to the mass collected by a reference sampler, a (rotating) micro-orifice uniform deposit impactor (MOUDI), which sampled at 30 LPM. Concentration enrichment factors in the range of 26 to 30 were achieved based on particle mass, sulfate, and nitrate as well as selected trace element and metal concentrations (Al, Si, Ca, Fe, K, Mn, Cu, Zn, Ti). CPC and MOUDI concentrations were highly correlated for all species, with R[sup 2] in the range of 0.74 to 0.89. The use of round (compared to rectangular geometry) nozzle virtual impactors in the CPC results in a high concentration efficiency, which reduces the CPC size as well as the power requirement that is required for its operation. The compact size of the CPC makes it readily transportable to desired locations for exposure to coarse-mode particles derived from different sources and thus of a varying chemical composition. [ABSTRACT FROM AUTHOR]