Combustion-generated Aerosols Research Articles

Black carbon toxicity dependence on particle coating: Measurements with a novel cell exposure method

Black carbon (BC) is a component of ambient particulate matter which originates from incomplete combustion emissions. BC is regarded as an important short-lived climate forcer, and a significant public health hazard. These two concerns have made BC a focus in aerosol science. Even though, the toxicity of BC particles is well recognized, the mechanism of toxicity for BC as a part of the total gas and particle emission mixture from combustion is still largely unknown and studies concerning it are scarce. In the present study, using a novel thermophoresis-based air-liquid interface (ALI) in vitro exposure system, we studied the toxicity of combustion-generated aerosols containing high levels of BC, diluted to atmospheric levels (1 to 10 μg/m3). Applying multiple different aerosol treatments, we simulated different sources and atmospheric aging processes, and utilizing several toxicological endpoints, we thoroughly examined emission toxicity. Our results revealed that an organic coating on the BC particles increased the toxicity, which was seen as larger genotoxicity and immunosuppression. Furthermore, aging of the aerosol also increased its toxicity. A deeper statistical analysis of the results supported our initial conclusions and additionally revealed that toxicity increased with decreasing particle size. These findings regarding BC toxicity can be applied to support policies and technologies to reduce the most hazardous compositions of BC emissions. Additionally, our study showed that the thermophoretic ALI system is both a suitable and useful tool for toxicological studies of emission aerosols.

Insights into sources and atmospheric processing at two polluted urban locations in the Indo-Gangetic plains from stable carbon and nitrogen isotope ratios and polycyclic aromatic hydrocarbons in ambient PM2.5

Ambient PM2.5 samples collected from two heavily polluted locations (Kanpur and Prayagraj) in Indo-Gangetic plains during wintertime were analyzed for stable isotopes (ẟ13C and ẟ15N), polycyclic aromatic hydrocarbons (PAHs), carbonaceous components, and ionic species. These data helped in understanding the aerosol composition, emission sources, and the associated atmospheric chemistry. Major contribution of high molecular weight (HMW) PAHs (4-ring, 5-ring, and 6-ring) to the total PAHs was observed at both the sampling sites. Organic carbon (OC) was a significant component of carbonaceous aerosols at both locations. In addition, OC/EC ratio (>2) revealed a dominant contribution from secondary organic carbon (SOC) during the sampling campaign. The contribution of SOC to total OC was much higher in Kanpur than in Prayagraj. A strong correlation between K+BB and OC observed for the two sites indicates a major influence of biomass burning. ẟ13C values of bulk PM2.5 samples at Prayagraj were slightly lower compared to Kanpur. ẟ13C and PAH isomeric ratios indicate significant contributions from biomass burning and petroleum combustion at both locations. Enhanced SOC formation appeared to control the ẟ13C at the Kanpur location, which may be due to the formation of secondary organic aerosol (SOA; 13C-depleted) from volatile organic compounds (VOCs) derived from combustion-generated aerosols (biomass/fossil fuel). This study also reports the ambient ẟ15N of aerosols at the Prayagraj site. The correlation of ẟ15N with nitrogenous components WSON, NH4+_N, and NO3−_N suggest 15N-depleted sources at the Prayagraj site. Like Kanpur, WSON and NH4+_N also influenced the bulk ẟ15N values of Prayagraj aerosols.

Impact of Nanocomposite Combustion Aerosols on A549 Cells and a 3D Airway Model.

The use of nanomaterials incorporated into plastic products is increasing steadily. By using nano-scaled filling materials, thermoplastics, such as polyethylene (PE), take advantage of the unique properties of nanomaterials (NM). The life cycle of these so-called nanocomposites (NC) usually ends with energetic recovery. However, the toxicity of these aerosols, which may consist of released NM as well as combustion-generated volatile compounds, is not fully understood. Within this study, model nanocomposites consisting of a PE matrix and nano-scaled filling material (TiO2, CuO, carbon nano tubes (CNT)) were produced and subsequently incinerated using a lab-scale model burner. The combustion-generated aerosols were characterized with regard to particle release as well as compound composition. Subsequently, A549 cells and a reconstituted 3D lung cell culture model (MucilAir™, Epithelix) were exposed for 4 h to the respective aerosols. This approach enabled the parallel application of a complete aerosol, an aerosol under conditions of enhanced particle deposition using high voltage, and a filtered aerosol resulting in the sole gaseous phase. After 20 h post-incubation, cytotoxicity, inflammatory response (IL-8), transcriptional toxicity profiling, and genotoxicity were determined. Only the exposure toward combustion aerosols originated from PE-based materials induced cytotoxicity, genotoxicity, and transcriptional alterations in both cell models. In contrast, an inflammatory response in A549 cells was more evident after exposure toward aerosols of nano-scaled filler combustion, whereas the thermal decomposition of PE-based materials revealed an impaired IL-8 secretion. MucilAir™ tissue showed a pronounced inflammatory response after exposure to either combustion aerosols, except for nanocomposite combustion. In conclusion, this study supports the present knowledge on the release of nanomaterials after incineration of nano-enabled thermoplastics. Since in the case of PE-based combustion aerosols no major differences were evident between exposure to the complete aerosol and to the gaseous phase, adverse cellular effects could be deduced to the volatile organic compounds that are generated during incomplete combustion of NC.

Importance of the number emission factor of combustion-generated aerosols from nano-enabled products

Accidental or open waste burning and incineration of nano-enabled products (NEPs) might lead to the release of incidental aerosols in the nano size range into the environment resulting in harmful effects on humans.We have investigated combustion-generated aerosol release during accidental burning for several real-life NEPs such as paints with silica (SiO2) and spruce wood panels containing SiO2 and Fe2O3 nanomaterials (NMs), paper with SiO2 and Fe2O3 NMs and polymeric composites with CuPhthtalocyanine NMs in poly lactic acid (PLA), polyamide 6 (PA6) and thermoplastic pol-urethane (TPU) matrices.Chemical compositions, aerosols number emission factors (nefs) and concentrations of the signature elements of the NMs of the combustion-generated aerosols were investigated. In addition, the residual ash was analyzed. The outcomes of this study shed light on how NM and matrix types influenced the properties of the released aerosols. Based on our results it was established that the combustion-generated aerosols were composed of transformed NMs with modified physical–chemical characteristics compared to the pristine NMs. In addition to aerosols with transformed NMs, there were also particles due to incomplete combustion of the matrix.Types of the pristine NMs and matrices affected the characteristics of the released aerosols. Since the effect of the aerosols is related to the inhaled aerosol number concentration, the nef is an important parameter. Our results showed that the nefs in the size range of 5.6 to 560 nm depended strongly on the type of combusted NEP, which indicated that the NEPs could be categorized according to their potential to release aerosols in this size range when they were burnt. The generated release data facilitate the assessment of human and environmental exposure and the associated risk assessment of combustion-generated aerosols from NEPs.

Regional Inhaled Deposited Dose of Indoor Combustion-Generated Aerosols in Jordanian Urban Homes

Indoor combustion processes associated with cooking, heating, and smoking are a major source of aerosols in Jordanian dwellings. To evaluate human exposure to combustion-generated aerosols in Jordanian indoor environments, regional inhaled deposited dose rates of indoor aerosols (10 nm to 25 µm) were determined for different scenarios for adult occupants. The inhaled deposited dose rate provides an estimate of the number or mass of inhaled aerosol that deposits in each region of the respiratory system per unit time. In general, sub-micron particle number (PN1) dose rates ranged from 109 to 1012 particles/h, fine particle mass (PM2.5) dose rates ranged from 3 to 216 µg/h, and coarse particle mass (PM10) dose rates ranged from 30 to 1600 µg/h. Dose rates were found to be dependent on the type and intensity of indoor combustion processes documented in the home. Dose rates were highest during cooking activities using a natural gas stove, heating via natural gas and kerosene, and smoking (shisha/tobacco). The relative fraction of the total dose rate received in the head airways, tracheobronchial, and alveolar regions varied among the documented indoor combustion (and non-combustion) activities. The significant fraction of sub-100 nm particles produced during the indoor combustion processes resulted in high particle number dose rates for the alveolar region. Suggested approaches for reducing indoor aerosol dose rates in Jordanian dwellings include a reduction in the prevalence of indoor combustion sources, use of extraction hoods to remove combustion products, and improved ventilation/filtration in residential buildings.

On the benefits of using multivariate analysis in mass spectrometric studies of combustion-generated aerosols.

The intricate chemistry of the carbonaceous particle surface layer (which drives their reactivity, environmental and health impacts) results in complex mass spectra. In this respect, detailed molecular-level analysis of combustion emissions may be challenging even with high-resolution mass spectrometry. Building on a recently proposed comprehensive methodology (encompassing all stages from sampling to data reduction), we propose herein a comparative analysis of soot particles produced by three different sources: a miniCAST standard generator, a laboratory diffusion flame and a single cylinder internal combustion engine. The surface composition is probed by either laser or secondary ion mass spectrometry. Two examples of multivariate analysis, Principal component analysis and hierarchical clustering analysis proved their efficiency in both identifying general trends and evidencing subtle differences that otherwise would remain unnoticed in the plethora of data generated during mass spectrometric analyses. Chemical information extracted from these multivariate statistical procedures contributes to a better understanding of fundamental combustion processes and also opens to practical applications such as the tracing of engine emissions.

Nanominerals, fullerene aggregates, and hazardous elements in coal and coal combustion-generated aerosols: An environmental and toxicological assessment

Studies on coal-derived nanoparticles as well as nano-minerals are important in the context of the human health and the environment. The coal combustion-generated aerosols also affect human health and environmental quality aspects in any coal-fired station. In this study, the feed coals and their combustion-generated aerosols from coal-fired boilers of two tea industry facilities were investigated for the presence of nanoparticles/nano minerals, fullerene aggregates, and potentially hazardous elements (PHEs). The samples were characterized by using X-ray diffraction (XRD), Time-of-flight secondary ion mass spectroscopy (TOF-SIMS), High resolution-transmission electron microscopy/energy dispersive spectroscopy (HR-TEM/EDS) and Ultra Violet-visible spectroscopy (UV–Vis) to know their extent of environmental risks to the human health when present in coals and aerosols. The feed coals contain mainly clay minerals, whilst glass fragments, spinel, quartz, and other minerals occur in lesser quantities. The PM samples contain potentially hazardous elements (PHEs) like As, Pb, Cd and Hg. Enrichment factor of the trace elements in particulate matters (PMs) was calculated to determine their sources. The aerosol samples were also found to contain nanomaterials and ultrafine particles. The fullerene aggregates along with potentially hazardous elements were also detected in the aerosol samples. The cytotoxicity studies on the coal combustion-generated PM samples show their potential risk to the human health. This detailed investigation on the inter-relationship between the feed coals and their aerosol chemistry will be useful for understanding the extent of environmental hazards and related human health risk.

Quantification of Optical and Physical Properties of Combustion-Generated Carbonaceous Aerosols (

A series of experiments were conducted to quantify and characterize the optical and physical properties of combustion-generated aerosols during both flaming and smoldering combustion of three materials common to underground mines-Pittsburgh Seam coal, Styrene Butadiene Rubber (a common mine conveyor belt material), and Douglas-fir wood-using a combination of analytical and gravimetric measurements. Laser photometers were utilized in the experiments for continuous measurement of aerosol mass concentrations and for comparison to measurements made using gravimetric filter samples. The aerosols of interest lie in the size range of tens to a few hundred nanometers, out of range of the standard photometer calibration. To correct for these uncertainties, the photometer mass concentrations were compared to gravimetric samples to determine if consistent correlations existed. The response of a calibrated and modified combination ionization/photoelectric smoke detector was also used. In addition, the responses of this sensor and a similar, prototype ionization/photoelectric sensor, along with discrete angular scattering, total scattering, and total extinction measurements, were used to define in real time the size, morphology, and radiative transfer properties of these differing aerosols that are generally in the form of fractal aggregates. SEM/TEM images were also obtained in order to compare qualitatively the real-time, continuous experimental measurements with the visual microscopic measurements. These data clearly show that significant differences exist between aerosols from flaming and from smoldering combustion and that these differences produce very different scattering and absorption signatures. The data also indicate that ionization/photoelectric sensors can be utilized to measure continuously and in real time aerosol properties over a broad spectrum of applications related to adverse environmental and health effects.

Coal combustion-generated aerosols: Formation and properties

Coal combustion for power generation is a major source of particulate air pollution. Understanding of the formation mechanisms and properties of coal combustion aerosols is critical to both the development of particulate control technologies and the assessment of their impacts on human health. This paper presents an overview of the current understanding of the mechanisms of ash particle formation in major coal-based power generation processes such as pulverized coal combustion, fluidized bed combustion and coal gasification, and a summary of the aerosol properties that are important for elucidating particle formation and evaluating their health effects. Principal particle formation mechanisms, including mineral coalescence, particle fragmentation, and vaporization-condensation, are reviewed. The complex nature of the formation mechanisms of submicron aerosols is emphasized. Evidence is provided for some solid-to-particle processes that are suspected to contribute to the formation of the submicron aerosols. Physicochemical properties such as particle size, composition and morphology are discussed. Of particular interest is the trimodality of the ash aerosol size distribution. Size-resolved elemental composition data are used to identify particle modes and to uncover their formation mechanisms. The formation of the additional central particle mode is attributed to heterogeneous condensation of vaporized species on existing fine residual ash particles. Future research topics associated with ash aerosol formation and properties are discussed.

Atmospheric Processes Influencing Aerosols Generated by Combustion and the Inference of Their Impact on Public Exposure: A Review

Combustion-generated aerosols, especially emissions of heavy and light duty vehicles, are the dominant contributors of ambient particulate matter (PM) in urban environments. This paper reviews the atmospheric processes (such as dilution, nucleation, condensation and coagulation) that dominate the dynamics of combustion aerosols following their emission, with a particular emphasis on PM from mobile sources. Atmospheric dilution affects the dynamic behavior of aerosols by shifting the gas-particle partitioning of the semi-volatile component of these aerosols. Our paper discusses the roles of dilution in changing the physico-chemical properties of the ambient aerosols, such as particle size distribution and number concentration, and the degree to which it affects non-labile and semi-volatile PM components. This information is complemented with a discussion of secondary aerosol formation from atmospheric photochemical reactions that involve precursors emitted from traffic sources. Special focus is devoted to the role of gas-phase vapors formed from the evaporation of the semi-volatile fraction of aerosols during dilution. Adding to the common recognition that volatile organic compounds (VOCs) are the major gaseous precursors, these vapors also actively participate in photochemical reactions and contribute to the formation of secondary aerosols. Following this discussion, we review recent findings that link PM semi-volatile components and their redox activity, and we discuss the influence and importance of PM volatility on particle toxicity. Lastly, this paper discusses possible metrics to regulate PM emissions and establish ambient air quality standards that are pertinent to public health, and suggests future investigations aimed to improve our current understanding of the adverse health effects of population exposure to combustion-generated aerosols.

An Experimental and Modelling Study of Particulate Formation in Premixed Flames Burning Methane

In this article we present an experimental and modeling study of Organic Carbon (OC) particles, with a typical size range of 1–10 nm, and soot particles, with sizes in the range 10–100 nm, formed in premixed methane flames at atmospheric pressure. An optical diagnostic method based on the interaction of an ultraviolet source, corresponding to the fifth harmonic of a Nd:YAG laser, with combustion-generated aerosols was used in order to measure the concentration profiles of both OC and soot particles with high spatial resolution. The high energy of the selected harmonic induces fluorescence from aromatic chromophoric groups and also allows soot particles to heat up and emit incandescent radiation. Optical measurements data are compared with numerical modeling simulations. The experimental data, in agreement with the model results, show that methane burned in slightly rich conditions forms prevalently organic particulate with mean size lower than 10 nm, while soot formation is observable only in very rich conditions.

Ambient source-specific particles are associated with prolonged repolarization and increased levels of inflammation in male coronary artery disease patients

Ambient particulate air pollution has been associated with altered cardiac function and systemic inflammation. We reported repolarization changes and variations in markers of inflammation in association with ambient particulate exposure in a panel of male coronary artery disease (CAD) patients. The objective of this analysis was to identify the specific sources associated with these effects. A panel of male CAD patients participated in 12 clinical visits in Erfurt, Germany. We used 56 patients’ 5 min ECG recordings for the analysis of repolarization parameters QT interval and T wave amplitude, and 57 patients’ plasma samples to determine the biomarkers von Willebrand factor (vWF) and C-reactive protein (CRP). Linear and logistic regression models were used to analyze the associations between five particle source factors (airborne soil, local traffic-related ultrafine particles, combustion-generated aerosols, diesel traffic-related particles, and secondary aerosols) and these health parameters adjusting for trend, weekday and meteorological variables. An increase in QT interval and a decrease in T wave amplitude were observed in association with traffic-related particles exposure during 0–23 h before the ECG recordings. The inflammatory marker vWF increased in association with both traffic-related particles and combustion-generated aerosols at different exposure lags. All source particles had positive associations with CRP levels above the 90th percentile (8.5 mg/l). These results suggest that traffic-related and combustion-generated particles show stronger adverse health impact with regard to cardiac effects, and that particles from different sources induce an acute phase response in these patients.

SOOT AND NANOPARTICLE FORMATION IN LAMINAR AND TURBULENT FLAMES

A new optical diagnostic method has been developed based on the interaction of a pulsed UV laser source with combustion-generated aerosols. This method allows characterization of nanoparticles of organic carbon (NOC) and soot by point measurements. Fluorescence and incandescence measurements induced by the fifth harmonic of a Nd-YAG laser at 213 nm are used for the determination of the volume fractions of particulates in a laminar premixed flame and in a turbulent non-premixed flame of ethylene/air. The selected light source enhances the fluorescence of NOC, which exhibit a large absorption band between 200 and 250 nm and also heats up soot particles to give incandescent emission. Ultraviolet emission signals are correlated with NOC extinction coefficients, while LII signals are correlated with extinction coefficients in the visible region. Laser light scattering measurements are used to estimate the mean sizes of both classes of particles.

The health effects of combustion-generated aerosols

The link between exposure to fine particles in the atmosphere and adverse health effects has been well-established by epidemiological studies. Most of the fine and ultrafine material of concern derives from combustion sources and is largely a mixture of elemental and organic carbon, metals, and inorganic compounds such as sulfates. When inhaled by people, the particles can be taken-up by cells in the lung. The particles can also penetrate into the circulatory system and lodge in organs such as the liver and heart. The mechanism for their impact on health is not entirely understood although the generation of reactive oxygen species such as the OH radical is a major focus. The inflammation that can be caused by these reactive species can exacerbate pre-existing ailments. Combustion conditions in mobile and stationary sources can affect the reactivity of aerosols and their ability to generate reactive oxygen species. Combustion conditions can also affect the speciation of transition metals, the morphology of particles and their composition, and their size, all parameters that may lead to adverse health effects.

The Effect of Chemical Composition on the Fractal-Like Structure of Combustion-Generated Inorganic Aerosols

The morphology of submicron flame-generated inorganic aerosols is known to be fractal-like with reported fractal exponents ranging from 1.1-2.5 for different materials. This wide range represents a correspondingly broad variation in structure and suggests that chemical composition might affect the final structure of flame-generated materials, a prospect of considerable importance in studies of submicron particulate penetration through electrostatic precipitators. To investigate this, the morphology of flame-generated submicron aerosols was studied by characterizing both fly ash generated in a pilot scale coal combustor and controlled composition inorganic aerosols generated in a bench scale flat flame burner. Fly ash generated during combustion of 2 bituminous coals at 2 different flame temperatures was found to be fractal-like with fractal exponents of 1.9-2 and fractal prefactors of 1.1-1.5. In addition, fly ash samples collected at the inlet and outlet of an attached pilot scale electrostatic precipita...

Multicomponent coagulation and condensation of toxic metals in combustors

The temporal evolution of the size-segregated composition of multiple, heavy metal, combustion-generated aerosols was investigated. The purpose was to gain insight into the competition between metal condensation and aerosol coagulation processes that affect the partitioning of toxic, heavy metals during combustion and their impact on the environment. Experiments were conducted on a2-to 16-kW downflow combustor, which supported a natural gas flame through which aqueous solutions of metal salts were sprayed. The behavior of both single metals and binary mixtures of lead and cadmium (which are both considered semivolatile) and of cadmium and nickel (the latter of which is refractory) was investigated. Particulate samples were withdrawn isokinetically through a rapid-dilution sampling probe from which they were quickly size segregated in a Berner low pressure impactor, allowing physical and chemical resolution in the submicron particle size range. Experimental data agreed with theoretical predictions using an existing literature model. This model solved the general dynamic equation numerically but was modified here to include the effects of film condensation in a simple manner. For samples withdrawn above the semivolatile metal dew points, theory showed that nucleation of the semivolatile metal in the probe, followed by coagulation, could explain completely, the measured size-segregated composition. With similar dew points and number concentrations, cadmium and lead particles interacted primarily through coagulation. However, cadmium and nickel particles did not interact by coagulation in the probe because of disparties in particle size and number concentrations. Further down the furnace, both model and data showed that compositions of particles were determined by condensation on existing nickel particles, rather than by nucleation of the semivolatile component (cadmium), followed by coagulation. These results are consistent with a literature hypothesis, on the effect of temperature quench rate on pertinent aerosol mechanisms.

Effects of Oxidants, Acids and other Agents on Particle Clearance in the Rat

e> An11. ocrup. Hyy .• Vol. 38. Suppleme nt I, pp. 927- 931 , 1994 Elsevier Scienoe Ltd Copyright <D 1994 British Occupational Hygiene Society Prinred in G real Brirain. All rish1s reserved Pergamon Inhaled Parlldts VII EFFECTS OF OXIDANTS, ACIDS AND OTHER AGENTS ON PARTICLE CLEARANCE IN THE RAT* R. F. PHALEN, R. C. MANNlX and M. T. KLEINMAN Community and Environmental Medicine, University of California, Irvine, CA 92717, U.S.A. Abstract- A series of inhalation experiments examining the effects of pollutants on the clearance of monodisperse tracer particles from the rat respiratory tract was performed. Exposures were as brief as 3 hand as long as 4 h per day for 21 days. Pollutant concentrations ranged from community air levels to several times the workplace standards. Short-term clearance was measured by analysing serially- collected faeces. Long-term clearance was measured by repeated, external gamma ray counting of the upper body. Ozone consistently delayed short-term clearance and accelerated long-term clearance. Particulate material usually had effects opposite to those of ozone. Some mixtures had greater effects than expected from the components; others had lesser effects. These studies identified several air pollutants that alter respiratory tract clearance rates. The studies also demonstrated the usefulness of the rat model. I NTRODUCTION THE MEASUREMENT of inhaled particle clearance efficiency is an important assessment in toxicological evaluations. Failure of this self-cleaning process leads to a build-up of foreign matter in the respiratory tract, perhaps increasing the likelihood of infections and other diseases. This paper deals with the effects we have observed in particle clearance studies using rats during the past 15 years. Acute and repeated pollutant exposures, which represented air pollution episodes were performed. The pollutant concentrations ranged from ambient air levels, up to several times concentrations found in the workplace. MATERIALS AND METHODS Animals Male barrier-reared Sprague-Dawley rats (Hilltop Laboratory Animals, Scottdale, Pennsylvania) weighing about 200 g were delivered in filter-equipped cartons and housed in particle and gas filtering laminar-flow caging systems for about 1 week prior to study. Quality control examinations were performed to establish that the rats were free of lung disease. Exposures Among the pollutants studied were ozone, sulphur dioxide, formaldehyde vapour, nitrogen dioxide, nitric acid vapour, acidic aerosols (sulphuric acid and ammonium bisulphate), combustion-generated aerosols (diesel-exhaust soot and propane-flame soot), ferric oxide and sulphate aerosols containing catalytic metals. Pollutants were *This paper was included in Poster Session 5 and the discussion included in the summary presented in Section 12.

Calibration, Intersampler Comparison, and Field Application of a New PM-10 Personal Air-Sampling Impactor

The MS&T personal impactor is designed to provide a particle size cut (d 50%) of 10 μm in aerodynamic diameter (PM-10) at a flow rate of 4 L/min. Data are presented that verify the designed particulate mass cut specifications of this impactor for personal sampling. These data are derived from three different analyses', laboratory calibration, intersampler comparison, and field application. Laboratory calibration using monodispersed liquid aerosol shows a sharp 10-μm particle cut size. The performance of the personal impactor was tested using ambient and combustion-generated aerosols. Established PM-10 samplers (the Sierra/Andersen dichotomous and the MS&T indoor air sampler impactor) were run side by side with the personal impactor. The intra- and intersampler vari-abilities in PM-10 measurements were evaluated. Results showed good precision among personal impactors (CV = 3.2%). The PM-10 sampled by the personal impactor was found to be highly correlated with measurements made with the indoor air sampler impactor (r 2 = 0.99) and the dichotomous sampler (r1 = 0.97). The impactor was subsequently employed for personal air sampling in the Total Human Environmental Exposure Study (THEES). The THEES sampling protocol entailed 24-hour sampling during a 14-day study interval. THEES field measurements included indoor, outdoor, and personal PM-10 samples. The personal impactor measurements for 13 participants were predicted by a time-weighted exposure model using indoor and outdoor PM-10 and specific activity variables (p < 0.01).