Peter A. Jaques

Versatile aerosol concentration enrichment system (VACES) for simultaneous in vivo and in vitro evaluation of toxic effects of ultrafine, fine and coarse ambient particles. Part I: Development and laboratory characterization

Abstract This study presents the development and bench-testing of a versatile aerosol concentration enrichment system (VACES) capable of simultaneously concentrating ambient particles of the coarse, fine and ultrafine size fractions for conducting in vivo and in vitro studies. The VACES consists of three parallel sampling lines (concentrators), each operating at an intake flow rate of 110 l min −1 . Coarse particles are concentrated using a single round nozzle virtual impactor. Concentration enrichment of PM2.5 and ultrafine particles is accomplished by first drawing air samples through two parallel lines, having 2.5 and 0. 18 μm cutpoint pre-impactors, respectively, to remove particles larger than these sizes from the air sample. Both of the smaller PM fractions are drawn through a saturation–condensation system that grows particles to 2– 3 μm droplets, which are subsequently concentrated by virtual impaction. A diffusion dryer is used in the fine and ultrafine concentrators to remove excess vapor and return the concentrated particles to their original size, prior to supplying them for in vivo exposures. The VACES can also provide highly concentrated liquid suspensions of particles of these three modes for in vitro toxicity studies. This is accomplished by connecting the concentrated output (minor) flows of each of the VACES parallel concentrators to a liquid impinger (BioSampler), used in a modified configuration, to collect particles under near-ambient pressure. Detailed laboratory characterization of the individual components of the VACES are presented in this paper, including evaluation of its ability to preserve particle mass, number, and chemical species during the concentration enrichment process. Our experimental results showed that concentration enrichment is accomplished with very high efficiency, minimal particle losses and without any significant dependence on particle size or chemical composition.

Versatile aerosol concentration enrichment system (VACES) for simultaneous in vivo and in vitro evaluation of toxic effects of ultrafine, fine and coarse ambient particles Part II: Field evaluation

Abstract This study presents results from a field evaluation of a mobile versatile aerosol concentration enrichment system (VACES), designed to enhance the ambient concentrations of ultrafine (less than 0.18 μm ), fine (0– 2.5 μm ), and coarse particles (2.5– 10 μm ) for in vivo and in vitro toxicity studies. The VACES may be coupled to an exposure chamber system to assess exposure-dose effects of any one, or all, of ambient aerosol on either human subjects and/or animals. Alternatively, concentrated ultrafine, fine and coarse particles can be directly collected by impaction onto a medium suitable for application to cell cultures for in vitro evaluation of their toxic effects. The enrichment and preservation of ambient ultrafine, fine and coarse particles by size and chemical composition was determined by comparisons made between the VACES and a co-located multistage MOUDI impactor, used as a reference sampler. Furthermore, preservation of the ultrafine fraction is measured by the enrichment based on ultrafine particle numbers, morphological characteristics as well as their elemental carbon (EC) content. The results suggest that the concentration enrichment process of the VACES does not differentially affect the particle size or chemical composition of ambient PM. The following fractions: (1) mass (coarse and fine PM); (2) number (ultrafine PM); (3) sulfate (fine PM); (4) nitrate (fine PM, after correcting for nitrate losses within the MOUDI); (5) EC (ultrafine PM); and (6) selected trace elements and metals (coarse and fine PM), are concentrated very close to the “ideal” enrichment value of 22—thereby indicating a near 100% concentration efficiency for the VACES. Furthermore, ultrafine particles are concentrated without substantial changes in their compactness or denseness, as measured by the fractal dimension analysis.

Resuspension of indoor aeroallergens and relationship to lung inflammation in asthmatic children.

Studies have shown links between the concentration of allergens found in homes and asthma. Inhalation of allergens present in settled residential dust can occur when the dust is resuspended via human activity or air currents. Although previous studies have measured allergen concentrations in homes, the focus has been on the presence of the allergens in settled dust samples. However, the actual inhalation exposure is to airborne allergens. The relationship between the settled dust composition and suspended allergens and endotoxin and the effect of exposure of these aeroallergens to asthmatics are not well understood for species typically present indoors. In this study, settled dust and airborne particulate matter samples were collected in the homes and school classrooms of asthmatic children of ages 9 to 16 and analyzed for endotoxin and allergens including dust mite and cockroach allergen, and dog and cat dander (Der p1, Der f1, Bla g1, Can f1, and Fel d1, respectively). Concentrations of cockroach allergen were below detection limit for all samples. Measurements of the settled dust samples show higher dust mite allergen in bedroom samples than in living room samples. Concentrations of airborne endotoxin and indoor allergens were generally higher in the homes than those measured at school. Within the homes, higher concentrations of airborne allergens and endotoxin were observed in the living rooms compared to the bedrooms. Resuspension rates for endotoxin, dust mite allergen, and, cat and dog dander were estimated in this study. Calculated resuspension rates for cat dander (8.1x10(-7)+/-3.5x10(-7)min(-1)) and dust mite allergen (2.1x10(-6)+/-7.6x10(-7)min(-1)and 1.4x10(-5)+/-4.6x10(-6)min(-1) for Der p 1 and Der f 1, respectively) were found to be higher than those for dog dander (3.1x10(-7)+/-1.3x10(-7)min(-1)) and endotoxin (3.6x10(-7)+/-1.6x10(-7)min(-1)). Markers of asthma inflammation including nitrate in exhaled breath condensate (EBC) and exhaled nitric oxide (eNO), were correlated with the concentrations of dust mite allergen (Der p 1) (Spearman r=0.598; p-value=0.068 for EBC and Spearman r=0.819; p-value=0.007 for eNO) and cat dander (Fel d 1) (Spearman r=0.917; p-value=0.0002 for EBC and Spearman r=0.697; p-value=0.054 for eNO) present in PM(10) samples.

Field Evaluation of the Differential TEOM Monitor for Continuous PM2.5 Mass Concentrations Special Issue of Aerosol Science and Technology on Findings from the Fine Particulate Matter Supersites Program

The performance of a prototype differential TEOM monitor (Rupprecht and Patashnick Co., NY) and its ability to measure the “actual” ambient near-continuous PM-2.5 mass in an area often high in semivolatile particulate matter has been evaluated. Measurements were made within a mobile particle instrumentation trailer (PIU) located in Claremont, CA—a “receptor” site in the Los Angeles Basin. The Differential TEOM monitor has been developed to directly measure ambient PM mass concentrations while accounting for collection artifacts, including loss of semivolatile aerosols and temperature changes. The Differential TEOM monitors used in this study were self-referencing, providing mass concentration measurements at 5 min intervals. To reference the semicontinuous mass measured by the Differential TEOM monitor, its 24 h time-integrated mass concentrations were compared to those determined by collocated filter-based samplers, i.e., MOUDI (Model 110) and Partisol (Model 2025). A HEADS was used to evaluate ammonium nitrate losses from the time-integrated samplers. The results show that PM-2.5 mass measurements using the Differential TEOM monitor are consistent with those of the MOUDI and Partisol, while differences can be generally explained by loss of ammonium nitrate from the reference samplers. The field results also demonstrate the ability of the Differential TEOM monitor to track adsorption and desorption processes from its sample filter. Although adsorption and evaporation can be dynamic processes, and difficult to estimate, the results of this study also suggest that the Differential TEOM monitor provides a very good estimate of the “actual” ambient particulate mass present on a near-continuous basis.

Effects of select PM-associated metals on alveolar macrophage phosphorylated ERK1 and -2 and iNOS expression during ongoing alteration in iron homeostasis.

It was hypothesized that relative mass relationships among select constituent metals and iron (Fe3+) govern the pulmonary immunotoxic potential of any PM2.5 sample, as these determine the extent to which Fe3+ binding by transferrin is affected (resulting in altered alveolar macrophage [AM] Fe status and subsequent antibacterial function). Iron response protein (IRP) binding activity is a useful indirect measurement of changes in Fe status, as reductions in cell Fe levels lead to increases in IRP binding. However, AM IRP activity can be affected by an increased presence of nitric oxide generated by inducible nitric oxide synthase (iNOS). This study sought to determine if any changes in AM IRP activity induced by PM2.5 constituents V, Mn, or Al were independent from effects of the metals on cell NO formation. NR8383 rat AM were exposed to Fe3+ alone or combined with V, Mn, or Al at metal:Fe ratios representative of those in PM2.5 collected in New York City, Los Angeles, and Seattle during fall 2001. Cells were then assessed for changes in IRP activity and iNOS expression. Phosphorylated extracellular signal-regulated kinase (ERK) 1 and 2 levels were also measured since activated ERKs are involved in signaling pathways that lead to increased iNOS expression. The results indicate that V and Al, and to a lesser extent Mn, altered IRP activity, though the effects were not consistently concentration dependent. Furthermore, while V and Mn treatments did not induce iNOS expression, Al did. These results confirmed our hypothesis that certain metals associated with PM2.5 might alter the pulmonary immunocompetence of exposed hosts by affecting the Fe status of AM, a major class of deep lung defense cells. This study was supported by funds from the USEPA/PM Center Grant R82735101. The authors are also grateful to services/assistance provided, in part, by the Center Program in the NYU Department of Environmental Medicine that is supported by NIEHS (grant ES00260). The authors also acknowledge the support provided from the U.S. EPA/PM Center Grant R82735501 at the Northwest Center for Particulate Matter and Health in Seattle, WA, and by U.S. EPA grants R82735201 and CR8280260-01-0 at the Southern California Particle Center and Supersite in Los Angeles.

Factor Analysis of Submicron Particle Size Distributions near a Major United States–Canada Trade Bridge

Abtracts A factor analytic model has been applied to resolve and apportion particles based on submicron particle size distributions downwind of a United States–Canada bridge in Buffalo, NY. The sites chosen for this study were located at gradually increasing distances downwind of the bridge complex. Seven independent factors were resolved, including four factors that were common to all of the five sites considered. The common factors were generally characterized by the existence of two or more number and surface area modes. The seven factors resolved were identified as follows: fresh tail-pipe diesel exhaust, local/street diesel traffic, aged/evolved diesel particles, spark-ignition gasoline emissions, background urban emissions, heavy-duty diesel agglomerates, and secondary/transported material. Submicron (>0.5 µm) and ultrafine (>0.1 µm) particle emissions downwind of the bridge were dominated by commercial diesel truck emissions. Thus, this study obtained size distinction between fresh versus aged vehicle exhaust and spark-ignition versus diesel emissions based on the measured high time-resolution particle number concentrations. Because this study mainly used particles <300 nm in diameter, some sources that would usually exhibit number modes >100 nm were not resolved. Also, the resolved profiles suggested that the major number mode for fresh tailpipe diesel exhaust might exist below the detection limit of the spectrometer used. The average particle number contributions from the resolved factors were highest closest to the bridge.

Evaluation of Nano- and Submicron Particle Penetration through Ten Nonwoven Fabrics Using a Wind-Driven Approach

Existing face mask and respirator test methods draw particles through materials under vacuum to measure particle penetration. However, these filtration-based methods may not simulate conditions under which protective clothing operates in the workplace, where airborne particles are primarily driven by wind and other factors instead of being limited to a downstream vacuum. This study was focused on the design and characterization of a method simulating typical wind-driven conditions for evaluating the performance of materials used in the construction of protective clothing. Ten nonwoven fabrics were selected, and physical properties including fiber diameter, fabric thickness, air permeability, porosity, pore volume, and pore size were determined. Each fabric was sealed flat across the wide opening of a cone-shaped penetration cell that was then housed in a recirculation aerosol wind tunnel. The flow rate naturally driven by wind through the fabric was measured, and the sampling flow rate of the Scanning Mobility Particle Sizer used to measure the downstream particle size distribution and concentrations was then adjusted to minimize filtration effects. Particle penetration levels were measured under different face velocities by the wind-driven method and compared with a filtration-based method using the TSI 3160 automated filter tester. The experimental results show that particle penetration increased with increasing face velocity, and penetration also increased with increasing particle size up to about 300 to 500 nm. Penetrations measured by the wind-driven method were lower than those obtained with the filtration method for most of the fabrics selected, and the relative penetration performances of the fabrics were very different due to the vastly different pore structures.

Relationships of outdoor and indoor ultrafine particles at residences downwind of a major international border crossing in Buffalo, NY

UNLABELLED During winter 2006, indoor and outdoor ultrafine particle (UFP) size distribution measurements for particles with diameters from 5.6 to 165 nm were taken at five homes in a neighborhood directly adjacent to the Peace Bridge Complex (PBC), a major international border crossing connecting Buffalo, New York to Fort Erie, Ontario. Monitoring with 1-s time resolution was conducted for several hours at each home. Participants were instructed to keep all external windows and doors closed and to refrain from cooking, smoking, or other activity that may result in elevating the indoor UFP number concentration. Although the construction and age for the homes were similar, indoor-to-outdoor comparisons indicate that particle infiltration rates varied substantially. Overall, particle concentrations indoors were lower and less variable than particle concentrations outdoors, with average indoor-outdoor ratios ranging from 0.1 to 0.5 (mean 0.34) for particles between 5.6 and 165 nm in diameter. With no indoor sources, the average indoor-outdoor ratios were lowest (0.2) for 20-nm particles, higher (0.3) for particles <10 nm, and highest (0.5) for particles 70-165 nm. PRACTICAL IMPLICATIONS This study provides insight into the penetration of UFP into homes and the resulting change in particle size distributions as particles move indoors near a major diesel traffic source. Although people spend most of their time in their homes, exposure estimates for epidemiological studies are generally determined using ambient concentrations. The findings of this study will contribute to improved size-resolved UFP exposure estimates for near roadway exposure assessments and epidemiological studies.

Performance Evaluation and Use of a Continuous Monitor for Measuring Size-Fractionated PM 2.5 Nitrate

A field evaluation of a new size-fractionating continuous fine particle nitrate monitor from Aerosol Dynamics Inc. (ADI), Berkeley, CA was conducted via comparison to traditional time-integrated filter (HEADS) and impactor (MOUDI) measurements. The new monitor consists of three cascaded integrated collection and vaporization cells (ICVC) and provides 10-min resolution particulate nitrate measurements in three particle diameter size ranges (0.10-0.45, 0.45-1.0, and 1.0-2.5 w m) corresponding to observed submodes in the particle size distribution in Southern California. Side-by-side sampling was conducted for approximately six months at two sites, both at downwind receptor locations east of downtown Los Angeles. Both size-resolved and total PM 2.5 nitrate concentrations were compared among the different sampling techniques. The ADI monitor and HEADS PM 2.5 nitrate measurements, for which nitrate sampling artifacts are expected to be low, are well correlated (r 2 = 0.79) with a geometric mean ADI:HEADS ratio of 0.90. The ADI size-fractionated nitrate data measured consistently more nitrate than the corresponding MOUDI stages due to volatilization of labile ammonium nitrate from the MOUDI impaction substrates. Less disagreement was observed in the 1.0-2.5 w m size range in which nitrate is more likely to exist as nonlabile sodium nitrate. The observed MOUDI nitrate losses are attributable to existing theories of nitrate sampling efficiencies and losses. The continuous nature of the data generated by the ADI monitor will provide valuable information on the spatial and temporal distribution of particulate nitrate in the atmosphere, and the new dimension of size-fractionation can help to determine the sources and formation mechanisms of atmospheric particulate nitrate as well. Examples of the atmospheric data generated in this study are presented and the potential utility of such data provided by the new monitor are discussed.

A Recirculation Aerosol Wind Tunnel for Evaluating Aerosol Samplers and Measuring Particle Penetration through Protective Clothing Materials

A recirculation aerosol wind tunnel was designed to maintain a uniform airflow and stable aerosol size distribution for evaluating aerosol sampler performance and determining particle penetration through protective clothing materials. The oval-shaped wind tunnel was designed to be small enough to fit onto a lab bench, have optimized dimensions for uniformity in wind speed and particle size distributions, sufficient mixing for even distribution of particles, and minimum particle losses. Performance evaluation demonstrates a relatively high level of spatial uniformity, with a coefficient of variation of 1.5-6.2% for wind velocities between 0.4 and 2.8 m s(-1) and, in this range, 0.8-8.5% for particles between 50 and 450 nm. Aerosol concentration stabilized within the first 5-20 min with, approximately, a count median diameter of 135 nm and geometric standard deviation of 2.20. Negligible agglomerate growth and particle loss are suggested. The recirculation design appears to result in unique features as needed for our research.