Development of a PM 10/PM 2.5 Cascade Impactor and In-Stack Measurements

Combustion and industrial processes are an important source of particles. Due to the new PM 10 and PM 2.5 standards for ambient air quality, a sampling system for PM 10/PM 2.5 in-stack measurements was designed and calibrated. In this new system, the exhaust gas is isokinetically sucked into a two stage impactor through the inlet of a plane filter device and the aerosol is fractionated in the particle size classes >10 w m, 10-2.5 w m, and <2.5 w m. Due to a relatively high volume flow (ca. 3.2 m 3 /h, depending on exhaust gas conditions), sampling times are kept short, e.g., 30 min for dust concentrations of 10 mg/m 3 . The impactor was calibrated in the laboratory and then operated at various industrial plants. Parallel measurements with identical devices showed average standard deviations of 3.1% (PM 10) and 3.4% (PM 2.5). Measurements of the cascade impactor together with the plane filter device gave plausible results and average PMx/TSP ratios of 0.49 (PM 2.5/TSP) and 0.78 (PM 10/TSP), showing a large variability for different processes. Elemental analysis using total-reflection X-ray fluorescence spectrometry, together with the size-fractionated sampling, proved to give characteristic patterns of the emitted aerosols, which can be used for a subsequent fingerprint modelling for source apportionment of ambient air pollution.     

Mixing and sink effects of air purifiers on indoor PM2.5 concentrations: A pilot study of eight residential homes in Fresno,California

We measured real-time and integrated PM2.5 inside eight occupied single-family homes in Fresno, California to evaluate how turbulent air mixing and pollutant removal caused by a filter-based air purifier influences the levels of fine particles in everyday indoor environments. In each home, we used a real-time monitor to log PM2.5 levels every 5 min over 12 weeks during which air purifiers were operating, except for a designed 3-day shutdown period for baseline measurements. We assessed how the operation of air purifiers changed the patterns of the frequency distributions for short-term (5 min) concentrations, which included spikes produced by sporadic indoor activities or emissions. This allowed us to examine the reduction effectiveness of air purifiers on concentrations of both recently emitted and well-mixed background aerosols. We observed a systematic change in the 5-min PM2.5 distributions in different homes—while air purifiers reduced 96% of the 5-min concentrations, they increased the magnitudes of the top 4%, representing transient concentration peaks. This phenomenon is consistent with what would be theoretically expected based on passive scalar turbulence in fluid physics. We also collected gravimetric filter samples for PM2.5 composition, finding mean reductions of the long-term (2–5 days) concentrations of 29%–37% for indoor PM2.5 and endotoxin. A less significant reduction (19%–26%) was seen for Pb (Lead).

© 2016 American Association for Aerosol Research     

广州市大气细颗粒物及微量元素的分析

在广州市区采集大气细颗粒物PM2．5样品,对PM2．5及其中12种微量元素进行分析。研究结果显示采样期间广州市大气PM25的平均浓度为113．3μg／m3,远远超过了美国EPA制定的PM25日均浓度限值（35μg／m3）。与国内外其它大城市相比,PM2．5中微量元素的浓度处于较高水平,其中重金属元素Cd、Pb、Zn、Cu、As、Ni、M0、Mn、Cr和Co的富集因子EF远远大于1,主要来源于人为污染·     

上海宝山区细颗粒气溶胶PM2.5特征

为了探讨上海宝山区细颗粒气溶胶PM2.5特征,于2008.9.1-2009.8.31连续采集了细颗粒气溶胶PM2.5样品。分别分析了空气中PM2.5的质量浓度水平以及空气中以PM2.5存在的金属元素质量浓度水平,结果显示：PM2.5的年均质量浓度达33.70μg/m3;冬季细颗粒气溶胶质量浓度水平最高达44.35μg/m3,超标情况最为严重,超标率达37.5%;同时,检测出的11种金属元素在四季空气中的总浓度分别为：0.320μg/m3、0.384μg/m3、0.326μg/m3、0.218μg/m3。     

Development and Evaluation of a PM 10 Impactor-Inlet for a Continuous Coarse Particle Monitor

Conventional PM 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 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 w m. Further evaluation of PM 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 10 inlet was performed in Riverside and Rubidoux, CA. A 2.5 w m cutpoint round nozzle virtual impactor was attached downstream of the developed PM 10 inlet. The Dichotomous PM 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 10 inlet operating at 16.7 l/min to remove particles larger than 10 w m in aerodynamic diameter. Commercially available 4.7 cm Teflon filters were used in both the Partisol and the PM 10 inlet to collect particulate matter (PM). Results showed good agreement between coarse PM (2.5-10 w m) mass concentrations measured by means of the PM 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 concentrations of the PM 10 inlet and Partisol persisted for wind speeds up to 19 km/h.     

A New Method for Retrieving Particle Refractive Index and Effective Density from Aerosol Size Distribution Data

As part of the Big Bend Regional Aerosol Visibility and Observation study (BRAVO) in July-October 1999, dry aerosol size distributions were measured over the size range of 0.05 < Dp < 20 w m using a TSI differential mobility analyzer (DMA), a PMS LASAIR 1003 optical particle counter (OPC), and a TSI aerodynamic particle sizer 3320 (APS). Extensive calibrations were performed to characterize the response of the OPC and APS to particles of different size and composition. This paper describes a new method that was developed to align size distributions in the instrument overlap regions, allowing for the retrieval of aerosol real refractive index and effective density. To validate the method, retrieved particle real refractive index was compared with volumeweighted model estimates based on measured PM 2.5 chemical composition. The study average retrieved real refractive index was m r = 1.566 - 0.012, and the average computed PM 2.5 refractive index was m r = 1.56 - 0.02; the agreement is well within experimental uncertainties. The average value of computed PM 2.5 bulk density was 1.85 - 0.14 g cm -3 . The average value of retrieved effective density, a function of particle dynamic shape factor, was 1.56 - 0.12 g cm -3 . The comparisons of effective density to computed bulk density suggested an average particle dynamic shape factor of h = 1.2. Sensitivity studies showed that real refractive index could be retrieved with uncertainties on the order of 2-3%, and effective density was retrieved with uncertainties on the order of 20-30%.     

Contributions of Foot Traffic and Outdoor Concentrations to Indoor Airborne Aspergillus

Aspergillus is a mold genus that can cause allergies, asthma, and pulmonary infections in sensitive people; its particles are common in indoor air. Two potential contributors to indoor Aspergillus particles were examined in this field study: human activity (walking over carpet), and outdoor Aspergillus concentrations. Filtered air samples were collected outdoors and inside two carpeted hallways in public buildings, while measuring indoor foot traffic. Aspergillus concentrations were analyzed using quantitative Polymerase Chain Reaction (qPCR). A bivariate model was used to predict indoor Aspergillus concentrations based on foot traffic and outdoor Aspergillus concentrations. For 3 of 4 scenarios, most of the variation in indoor Aspergillus could be explained by the combined effect of outdoor Aspergillus concentrations and foot traffic, with particularly strong correlations during peak traffic times. In addition, indoor Aspergillus was significantly associated with outdoor Aspergillus in 2 of 4 scenarios, and with foot traffic in 2 of 4 scenarios. For 2 of 3 sampling campaigns, Aspergillus did not have a significant association either with gravimetric particulate matter ≤5 μm (PM₅), or with optically measured PM of 0.75–1 μm, 1–2 μm, 2–3.5 μm, or 3.5–5 μm. Controlled experiments, examining whether the foot traffic contribution was due to resuspension from carpeting or to shedding from clothing and/or human bodies, saw a significant increase in Aspergillus levels from resuspension. Although an increase was also seen for clothing over Tyvek suits, it was not statistically significant.     

Effect of Semivolatile Material on PM 2.5 Measurement by the PM 2.5 Federal Reference Method Sampler at Bakersfield,California

The chemical composition of fine particulate material was determined for samples collected in Bakersfield, CA, during February-March, 1998 using several diffusion denuder samplers, including the PC-BOSS, which measures both semivolatile fine particulate nitrate and organic material. An average of 56% of the fine particulate carbonaceous material was lost from the filters of the Particle Concentrator-Brigham Young University Organic Sampling System (PC-BOSS). A comparable amount of fine particulate semivolatile organic material was also lost from collected particles with single filter samplers, such as the PM 2.5 Federal Reference Method. The fraction of nitrate lost from collected particles was a function of temperature and humidity, with the biggest effect being due to temperature. The fraction of nitrate lost was comparable for conventional annular denuder samplers and the PM 2.5 FRM, averaging 33%. The nitrate loss from particles for the PC-BOSS was smaller, averaging 11%, possibly due to the concentration of particulate material prior to collection with this sampler. The loss of nitrate and semivolatile organic material during sample collection resulted in the PM 2.5 FRM sampler giving PM 2.5 mass that was an average of 30% (7.3 w g/m 3 ) lower than the true value and different from the true value from negligible to 20 w g/m 3 .     

High-Volume Diffusion Denuder Sampler for the Routine Monitoring of Fine Particulate Matter: II. Field Evaluation of the PC-BOSS

The high-volume Brigham Young University organic sampling system with a particle concentrator (PC-BOSS) has been field evaluated for the determination of airborne fine particulate matter including semivolatile chemical species during 3 intensive sampling programs in 1997: Tennessee Valley Authority (TVA), Lawrence County, TN; Riverside, CA; and Provo, UT. The PC-BOSS precision was tested using 2 collocated PC-BOSS samplers. In addition, the PC-BOSS results were compared with results from a prototype PM 2.5 U.S. EPA federal reference method (FRM sampler), a filter pack sampler (quartz and charcoal sorbent filters), the BIG BOSS, an annular denuder sampler, and the ChemSpec sampler for the determination of major fine particulate species. Fine particulate mass, sulfate, nitrate, and organic carbonaceous material (OC) determined by 2 PC-BOSS samplers agreed within - 10%. Possibly due to absorption of SO 2 by a quartz filter, the sulfate concentrations determined by the filter pack sampler and the BIG BOSS were higher (by 10 - 3%) than concentrations obtained with the other samplers. No absorption of SO 2 (g) by the quartz filters of the PC-BOSS occurred due to the high efficiency (>99%) of its denuder. The PC-BOSS, annular denuder, and ChemSpec samplers agreed with each other (to within - 0.5 w g/m 3 , - 17%, with no bias) for the determination of fine particulate nitrate concentrations, including volatilization losses. The prototype PM 2.5 FRM sampler collected only particle-retained nonvolatile mass. The mass concentrations determined by the PM 2.5 FRM agreed with those collected by the post-denuder Teflon filters of the PC-BOSS (to within - 1.1 w g/m 3 , - 10%, with no bias). The overall loss of material from particles and the resultant underestimation of the particulate mass concentrations by the PM 2.5 FRM depended on the fine particle composition and the ambient temperature.     

Size-Resolved Concentrations of Particulate Matter and Bioaerosols Inside versus Outside of Homes

Size-resolved airborne particulate matter samples (PM _2.5 , PM ₁₀ , and TSP) collected inside ten northern California homes over four days and one night (9–12 h/sample, spanning a 3.5 week period) were analyzed for protein, endotoxin, and (1 → 3)-β-D-glucan concentrations. Some simultaneous size-resolved outdoor samples were also collected. The associations of residential characteristics and occupant behavior with the indoor airborne levels were investigated. In addition, the relation between these chemical biomarkers and the more traditional culturing approaches was studied. Most of the indoor mass concentration of airborne particles and protein was in the fine fraction (PM _2.5 ), while the mass of airborne endotoxin and (1 → 3)-β-D-glucan was mainly in the coarser fractions (PM _10–2.5 and PM _TSP–10 ). No strong correlations were seen between short-term (3–6 min) culturable bacteria and fungi counts and the corresponding longer-term (9–12 h) biomarker levels. Daytime indoor levels of the biomarkers tended to be higher than outdoors, especially for the PM _10–2.5 fraction, but only in a few cases were the indoor/outdoor relationships statistically significant. Indoor pets were associated with elevated airborne PM and bioaerosols inside homes. Two other factors, wall-to-wall carpet and older houses, also appear to be associated with some elevations in indoor levels.     

Design,Calibration, and Field Test of a Cyclone for PM 1 Ambient Air Sampling

Ambient air sampling at a flow rate of 16.7 Lpm (1 m 3 /h) has been well established with the adoption, within the USA, of the EPA regulations governing PM 2.5 sampling. Subsequent to the adoption of the new regulation, problems were encountered with the impactor technique utilized for establishing a PM 2.5 cut ( D 50 = 2.5 w m aerodynamic equivalent diameter, A.E.D.). In order to avoid the depression in the cut point engendered by a buildup of collected material on the impactor stage and to extend the operating interval between cleanings, a cyclone was developed to replace the impactor. Although not an adopted standard, PM 1 has a practical appeal in that it represents the smallest cut point that can practically be assessed for long periods of time at high flow rates utilizing inertial techniques. Further relevance is attributed to this cut by interest in particulate matter related to diesel engine emissions. A new version of the sharp cut cyclone (SCC) was constructed with the aim of obtaining a cut point at D 50 = 1 w m at a flow rate of 16.7 Lpm. The dimensions of the cyclone were calculated using the SCC design model by Kenny and Gussman. Field studies were conducted to validate the PM 1 cyclone and to compare the results to colocated PM 10 and PM 2.5 concentration measurements.     

Characteristics of secondhand electronic cigarette aerosols from active human use

The electronic cigarette (EC) is a new source of indoor airborne particles. To better understand the impacts of secondhand vaping (SHV) emissions on indoor air quality, real-time measurements of particle size distribution, particle number concentration (PNC), fine particulate matter (PM_2.5), CO₂, CO, and formaldehyde were conducted before, during, and after 10 min EC-use among 13 experienced users in an 80 m³ room. To assess particle transport in the room, multiple sampling locations were set up at 0.8, 1.5, 2.0, and 2.5 m away from the subjects. The arithmetic mean (standard deviation) of background PNC and PM_2.5 concentrations in the room were 6.39 × 10³ (1.58 × 10²) particles/cm³ and 8 (1) μg/m³, respectively. At 0.8 m away from EC users, right after initiation of puffing, the PNC and PM_2.5 concentrations can reach a peak of ～10⁵ particles/cm³ and ～3 × 10³ µg/m³, respectively, and then dropped quickly to background levels within 20 s due to dilution and evaporation. At the 0.8 m sampling location, the mean PNC and PM_2.5 concentrations during puffing were 2.48 × 10⁴ (2.14 × 10⁴) particles/cm³ and 188 (433) µg/m³, respectively. In addition, two modes of SHV particles were observed at about 15 and 85 nm. Moreover, concentrations of SHV particles were negatively correlated with the distances to EC users. At the 1.5 m location, PNC and PM_2.5 levels were 9.91 × 10³ (1.76 × 10³) particles/cm³ and 19 (14) µg/m³, respectively. Large variations of mean PNC levels exhaled per puff were observed both within and between EC users. Data presented in this study can be used for SHV particle exposure assessment.

Copyright © 2017 American Association for Aerosol Research     

Using Regional Data and Building Leakage to Assess Indoor Concentrations of Particles of Outdoor Origin

Time-resolved fine particle concentrations of nitrate, sulfate, and black carbon were examined to assess the appropriateness of using regional data and calculated air exchange rates to model indoor concentrations of particles from outdoor sources. The data set includes simultaneous, sub-hourly aerosol composition measurements at three locations: a regional monitoring site in Fresno, California, inside of an unoccupied residence in Clovis, California, located 6 km northeast of the regional site, and immediately outside of this same residence. Indoor concentrations of PM_2.5 nitrate, sulfate, and black carbon were modeled using varying sets of inputs to determine the influence of three factors on model accuracy: the constraints of the simplified indoor-outdoor model, measured versus modeled air exchange rates, and local versus regional outdoor measurements.

Modeled indoor concentrations captured the lag and attenuation in indoor concentrations as well as the differences among chemical constituents in the indoor-outdoor concentration relationships. During periods when the house was closed and unoccupied, use of air exchange rates calculated from the LBNL infiltration model in place of those directly measured did not contribute significantly to the error in the estimated indoor concentrations. Differences between ambient concentrations at the regional monitoring site and the immediate neighborhood contributed to estimation errors for sulfate and black carbon. Evaporation was the dominant factor affecting indoor nitrate concentrations. Even when limiting the model inputs to concentrations and meteorological parameters measured at the regional monitoring station, the modeled concentrations were more highly correlated with measured indoor concentrations than were the regional measurements themselves.     

PM 2.5 Semivolatile Organic Material at Riverside,California: Implications for the PM 2.5 Federal Reference Method Sampler

Particulate semivolatile organic compounds can be lost from particles on a filter during sample collection and storage, resulting in a negative artifact. Gas-phase organic compounds can adsorb on a quartz filter to cause a positive artifact. A sampler (Particle Concentrator-Brigham Young University Organic Sampling System: PC-BOSS) has been developed that uses a cyclone and virtual impactor (particle concentrator) inlet to provide a concentrated stream of 0.1-2.5 w m particles. The concentrator is followed by a BOSS diffusion denuder to remove interfering gas-phase compounds and filter packs to collect particles, including any semivolatile species lost from the particles during sampling. The sampler can be used for the determination of both fine particulate nitrate and semivolatile organic material without significant "positive" or "negative" sampling artifacts. The sampler has been evaluated at Riverside, CA. The collection efficiency of the particle concentrator was stable, being 65% - 2% and 61% - 1% for particulate sulfate and soot, respectively. Results obtained with the PC-BOSS for the determination of PM 2.5 organic material including semivolatile components agreed with results from a BOSS, but not with filter pack results. The precision of the PC-BOSS results for particulate organic material was - 8%. An average of 50% of the particulate organic material was lost from the particles during sampling for all samplers used. As a result of the loss of semivolatile organic material and nitrate, the PM 2.5 Federal Reference Method sampler underdetermined PM 2.5 by an average of 34% with the under measurement varying from negligible to 27 w g/m 3 , averaging 8.9 w g/m 3 .     

南充市车流量对城市空气质量的影响分析

根据南充市城区SO2、NO2、PM10和PM2.5小时浓度数据,结合四种主要交通方式的车流量,分析车流量与空气质量相关性及其影响。结果表明,南充市城区每日车流量变化趋势呈现"四峰"现象,在08:00-09:00、11:00-12:00和14:00-15:00三个时段分别达到2650、2360和2677辆,第四个峰值可能在19:00或者之后;车流量以私家车和出租车为主,分别占总车流量的45%±4%和26%±3%。SO2、NO2质量浓度值基本稳定,为0.020 mg/m3左右,PM10和PM2.5的日平均浓度随日平均车流量变化比较明显,机动车流量对PM10、NO2的影响比SO2、PM2.5大。     

Light Degrading Properties of Size-Fractionated PM 10 Aerosol Samples Collected from an Industrial Area in Brisbane,Australia

Thirty-seven days of PM 10 aerosol samples (particles with aerodynamic diameter <10 w m) were collected in an industrial area in Brisbane during April to June 1999 to study the light extinction efficiencies of urban aerosols in different size ranges. The light scattering coefficient of the air was measured by nephelometry. The light absorption coefficient of the aerosol samples was measured by the integrating plate laser absorption method. Multiple linear regression techniques were used to investigate the relationships between the visibility degrading properties and the chemical composition of the aerosol samples. The results are comparable with those from other visual air quality studies. The absorption of light by fine (PM 2.5 ) aerosols is mainly due to elemental carbon (EC) particles smaller than 0.5 w m. The b 0 ap values of EC particles in different size ranges are 9.08 (< 2.7 w m) and 0.32 (2.7-10 w m)m 2 g -1 , respectively. The absorption of light by coarse (PM 2.5-10 ) aerosols is mainly due to soil ( b 0 ap = 0.17) and organic ( b 0 ap = 1.11) particles. The scattering of light is highly related to the concentration of fine particles in the air (mass scattering efficiency b 0 sp = 1.65) and is mainly due to the fine sulphate ( b 0 sp = 10.9), soil ( b 0 sp = 2.73), and EC ( b 0 sp = 3.89) particles. On average, fine EC (44%), sulphate (20%) and soil (7%) particles, NO 2 (9%), and Rayleigh scattering (19%) were the largest contributors of visibility degradation for the sampling days in this study.     

Determining Size-Specific Emission Factors for Environmental Tobacco Smoke Particles

Because size is a major controlling factor for indoor airborne particle behavior, human particle exposure assessments will benefit from improved knowledge of size-specific particle emissions. We report a method of inferring size-specific mass emission factors for indoor sources that makes use of an indoor aerosol dynamics model, measured particle concentration time series data, and an optimization routine. This approach provides--in addition to estimates of the emissions size distribution and integrated emission factors--estimates of deposition rate, an enhanced understanding of particle dynamics, and information about model performance. We applied the method to size-specific environmental tobacco smoke (ETS) particle concentrations measured every minute with an 8-channel optical particle counter (PMS-LASAIR; 0.1 m 2+ w m diameters) and every 10 or 30 min with a 34-channel differential mobility particle sizer (TSI-DMPS; 0.01 m 1+ w m diameters) after a single cigarette or cigar was machine-smoked inside a low air-exchange-rate 20 m 3 chamber. The aerosol dynamics model provided good fits to observed concentrations when using optimized values of mass emission rate and deposition rate for each particle size range as input. Small discrepancies observed in the first 1-2 h after smoking are likely due to the effect of particle evaporation, a process neglected by the model. Size-specific ETS particle emission factors were fit with log-normal distributions, yielding an average mass median diameter of 0.2 w m and an average geometric standard deviation of 2.3 with no systematic differences between cigars and cigarettes. The equivalent total particle emission rate, obtained by integrating each size distribution, was 0.2-0.7 mg/min for cigars and 0.7-0.9 mg/min for cigarettes.     

Automated Measurement of the Size and Concentration of Airborne Particulate Nitrate

A three-stage, cascaded integrated collection and vaporization system has been developed to provide automated, 10 min resolution monitoring of the size and concentration of fine particulate nitrate in the atmosphere. Particles are collected (7 min) by a humidified impaction process, and analyzed in place (3 min) by flash vaporization and chemiluminescent detection of the evolved nitrogen oxides. The three size fractions, < 0.45 w m, 0.45-1.0 w m, and 1.0-2.5 w m, are chosen to distinguish the condensation, droplet, and coarse components of PM 2.5 . The size precut at 2.5 w m is done at ambient conditions, while the size fractionation at 1.0 w m and 0.45 w m is done at a constant relative humidity of 65%. The system is calibrated with laboratory aerosols, including comparison of sizing for hygroscopic salt and hydrophobic organic aerosols. The complete system is tested with monodisperse ammonium nitrate aerosol generated with a high-flow differential mobility analyzer coupled with an impactor precut and yields results consistent with the calibration of the individual stages.     

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).