The Ultrasonic Personal Aerosol Sampler (UPAS) is a small, lightweight, and quiet sampler that collects airborne particulate matter on a filter for gravimetric or compositional analysis. The objective of this work was to develop UPAS inlets with collection efficiencies that match criteria for respirable or thoracic mass sampling. The two-stage inlet for respirable mass described here utilizes an impaction stage and a cyclone, whereas the one-stage inlet for thoracic mass sampling utilizes a circular slot impactor. Inlet designs are based on particle collection theory used in conjunction with an optimization algorithm to predict initial inlet dimensions; these predictions were the starting points for experiments that finalized dimensions and operating conditions. Both the respirable mass inlet and the thoracic mass inlet described here are interchangeable with the UPAS, and both have efficiencies that match well with their respective standards. With either inlet, the collected sample should be within ±5% of what the standard specifies for aerosols with reasonably broad size distributions.

Traditional methods for measuring personal exposure to fine particulate matter (PM2.5) are cumbersome and lack spatiotemporal resolution; methods that are time-resolved are limited to a single species/component of PM. To address these limitations, we developed an automated microenvironmental aerosol sampler (AMAS), capable of resolving personal exposure by microenvironment. The AMAS is a wearable device that uses a GPS sensor algorithm in conjunction with a custom valve manifold to sample PM2.5 onto distinct filter channels to evaluate home, school, and other (e.g., outdoors, in transit, etc.) exposures. Pilot testing was conducted in Fresno, CA where 25 high-school participants ( n = 37 sampling events) wore an AMAS for 48-h periods in November 2016. Data from 20 (54%) of the 48-h samples collected by participants were deemed valid and the filters were analyzed for PM2.5 black carbon (BC) using light transmissometry and aerosol oxidative potential (OP) using the dithiothreitol (DTT) assay. The amount of inhaled PM2.5 was calculated for each microenvironment to evaluate the health risks associated with exposure. On average, the estimated amount of inhaled PM2.5 BC (μg day-1) and OP [(μM min-1) day-1] was greatest at home, owing to the proportion of time spent within that microenvironment. Validation of the AMAS demonstrated good relative precision (8.7% among collocated instruments) and a mean absolute error of 22% for BC and 33% for OP when compared to a traditional personal sampling instrument. This work demonstrates the feasibility of new technology designed to quantify personal exposure to PM2.5 species within distinct microenvironments.

Assessing personal exposure to air pollution has long proven challenging due to technological limitations posed by the samplers themselves. Historically, wearable aerosol monitors have proven to be expensive, noisy, and burdensome. The objective of this work was to develop a new type of wearable monitor, an ultrasonic personal aerosol sampler (UPAS), to overcome many of the technological limitations in personal exposure assessment. The UPAS is a time-integrated monitor that features a novel micropump that is virtually silent during operation. A suite of onboard environmental sensors integrated with this pump measure and record mass airflow (0.5-3.0 L/min, accurate within 5%), temperature, pressure, relative humidity, light intensity, and acceleration. Rapid development of the UPAS was made possible through recent advances in low-cost electronics, open-source programming platforms, and additive manufacturing for rapid prototyping. Interchangeable cyclone inlets provided a close match to the EPA PM2.5 mass criterion (within 5%) for device flows at either 1.0 or 2.0 L/min. Battery life varied from 23 to 45 hours depending on sample flow rate and selected filter media. Laboratory tests of the UPAS prototype demonstrate excellent agreement with equivalent federal reference method samplers for gravimetric analysis of PM2.5 across a broad range of concentrations.

Introduction: Assessing personal exposure to air pollution has proven challenging, especially at scales relevant for epidemiologic research. The exposure monitors themselves pose technological limitations (cost, noise, weight) that restrict research to relatively modest sample sizes. Further complicating this problem are issues of reliability and user compliance, both of which are exacerbated when conducting research in resource-limited environments. Methods: We developed a new monitor, an ultrasonic personal aerosol sampler (UPAS) through advances in low-cost electronics, open-source programming, and additive manufacturing. The UPAS is a time-integrated aerosol monitor that features a novel, virtually silent micro-pump. The UPAS was tested for pump and battery performance, flow accuracy, sampling efficiency, and through chamber tests against an EPA-certified reference method for PM2.5. Results: The UPAS prototype weighs 190g, emits under 40 dB of noise, and can operate continuously for 48 or 24 hr on a single battery charge at either 1 or 2 L/min of flow, respectively. The UPAS cyclone inlet performed within 5% of the EPA federal reference method (FRM) for PM2.5. Chamber tests relative to the FRM sampler showed low bias (accuracy of 5.5 +/- 4.8% at one standard deviation), good precision (6.1% relative standard deviation among co-located devices), and high linearity across a broad range of PM2.5 concentrations (20-1000 ug/m3) that are relevant to household air pollution. Conclusions: The UPAS shows promise for increasing our ability assess personal PM exposures by reducing the size, weight, and cost of personal samplers. As a result, sampling can be conducted at scales that are more relevant to epidemiologic and community-based research.

Large inhalable particles are present in the workplace, yet few instruments exist to count and size such particles in situ. Inhalable-aerosol exposure can be evaluated using mass-based samplers such as the IOM or Button sampler, but these devices do not provide information on particle size distributions. Size-resolved samplers such as cascade impactors or the Aerodynamic Particle Sizer are limited to particle sizes <20m due to difficulties with particle aspiration and transmission losses. This work describes the development of two samplers capable of measuring the concentration and size distribution of airborne particles from 20 to 100m in aerodynamic diameter. One device is based on the principles of an upflow elutriator, whereas the other eliminates the potentially adverse effects of an upward-facing jet to separate particles from a quiescent airstream. Analytical models and computational fluid dynamics simulations were used to predict the performance of the two samplers. Sampling efficiencies of these devices were tested in a calm-air chamber with polydisperse, fluorescent microspheres (10-100m). Epifluorescent microscopy of settled dust was used to determine reference particle counts and sizes. Both devices are capable of size-selective sampling; however, the second sampler produced higher sampling efficiencies and sharper cut points compared to the simpler elutriator design. Experimental sampling efficiencies for both samplers showed good agreement with computational and analytical solutions. This work suggests that these devices can size-segregate inhalable aerosols in quiescent environments.Copyright (c) 2015 American Association for Aerosol Research

Many cookstove studies conducted in the field fail to measure meaningful differences between different stove technologies. Although meaningful differences do not always exist, significant differences are often missed because of low statistical power. A numerical model has been developed to determine the minimum sample size necessary to ensure that cookstove field studies are well-designed, efficient, and have adequate statistical power to characterize the concentrations of pollutants inside homes. The numerical model uses a Monte Carlo prediction method to generate probabilistic distributions of indoor pollutant concentrations. The model is based on a series of user inputs, including emissions rate, home size, air-exchange rate, fuel-moisture content, and measurement error. Application of this model to an example situation showed that, even under optimistic measurement conditions, a substantially high number of test replicates would be required. This approach should allow organizations to select appropriate sample sizes to test cookstoves in the field and to identify factors that contribute to variability among tests.

Air quality was measured inside 628 United Arab Emirates (UAE) personal residences.Weekly average concentrations of carbon monoxide (CO), formaldehyde (HCHO), hydrogen sulfide (H 2 S), nitrogen dioxide (NO 2 ), sulfur dioxide (SO 2 ), and three size fractions of particulate matter (PM 2.5 , PM c , and PM 10 ) were determined in each home.In a subset of the homes, measurements of outdoor air quality, ultrafine PM concentrations, and elemental PM concentrations were also made.Questionnaires were administered to obtain information on housing demographics and lifestyle habits.Air measurements were performed using simple and cost effective passive samplers.The 90 th percentiles of indoor CO, HCHO, H 2 S, NO 2 , and SO 2 were 1.55 ppm, 0.05 ppm, 0.12 ppm, 0.01 ppm, and 0.05 ppm, respectively.Median indoor PM 2.5 , PM c , and PM 10 , concentrations were 5.73 µg/m 3 , 29.4 µg/m 3 , and 35.2 µg/m 3 , respectively.The median indoor concentration of ultrafine PM was 3.62 × 10 10 particles/m 3 .Indoor/outdoor ratios for PM were 0.44, 0.41, and 0.38 for ultrafine PM, PM 2.5 , and PM 10 , respectively.These values fall within the range of other indoor air studies findings conducted in developing countries.Air conditioning, smoking, and attached kitchens were significantly correlated with indoor levels of carbon monoxide.In addition, indoor concentrations of PM 2.5 and PM 10 were significantly correlated with vehicles parked within five meters of the home, central air conditioning, and having attached kitchens.This is the first robust indoor air * Corresponding author.quality data set developed for the UAE.This study demonstrates that screening level tools are a good initial step for assessing air quality when logistical issues (distance, language, cultural, training) and intrusion into personal lives need to be minimized.

Effective assessment of nanoparticle exposures requires accurate characterization of the aerosol. Of increasing concern is personal exposure to engineered nanoparticles that are specifically designed for use in the nanotechnology sector. This manuscript describes the operation and use of a personal sampler that utilizes thermophoretic force to collect nanoparticles onto a standard TEM (transmission electron microscope) grid. After collection, nanoparticles on the TEM grid are analyzed with an electron microscope, and the resultant data used to determine the characteristics of the nanoparticle aerosol sampled. Laboratory experiments were conducted to determine the inlet losses and collection efficiency of the thermophoretic sampler for particles between 20 and 600nm in diameter. These results are used together with theory for thermophoretic velocity to form a transfer function that relates the properties of the collected particles to the properties of the sampled aerosol. The transfer function utilizes a normalization factor, F(d), which is larger than unity for very small particles but approaches unity for particles larger than about 70nm. Copyright 2014 American Association for Aerosol Research

Copyright 2012 American Association for Aerosol Research

The UNC passive aerosol sampler measures concentrations and size distributions of indoor, outdoor, and occupational particulate matter. This study assessed the precision of passive sampler measurements using data from duplicate pairs of samplers that were deployed in a large field study. Particle count and size data were used to calculate PM2.5 and PM10-2.5 concentrations. To determine precision, the concentrations measured by duplicate samplers were compared to one another. Results showed that this sampler provides mass concentrations of PM2.5 and PM10-2.5 in the field with relative standard deviations that approach about 15%, with greater precision associated with higher concentrations (PM2.5>5μg/m3 and PM10-2.5>20μg/m3). Variability between measurements was associated with counting statistics and possibly with differences in the open area of the passive sampler mesh screen.

Performance data for fabric filters using either woven or felt bags can be better understood when fault processes such as pinhole bypass and seepage are considered. Penetration straight through the dust cake and fabric may not be important by comparison. Observed trends of increased penetration with increased filtration velocity, constant or slightly increased penetration with increasing particle diameter, and constant penetration with additional dust loading can be explained by fault processes. The pulse-jet experimental work described here, done over many filtration and cleaning cycles, shows that penetration increases substantially with increasing filtration velocity and that this increase is due entirely to seepage.

BACKGROUND:The Arabian Gulf nations are undergoing rapid economic development, leading to major shifts in both the traditional lifestyle and the environment. Although the pace of change is brisk, there is a dearth of environmental health research in this region. OBJECTIVE:We describe challenges and successes of conducting an environmental epidemiologic study in the United Arab Emirates (UAE), a Gulf nation in the Middle East, with an inter-disciplinary team that includes in-country academic and government collaborators as well as U.S. academic collaborators. DISCUSSION:We present several issues, including study and data collection design, exposure assessment, scheduling and time coordination, quality assurance and quality control, and institutional review board protocols. These topics are considered in a cultural context. Benefits of this research included building linkages among multinational, interdisciplinary team members, generating data for local environmental decision making, and developing local epidemiologic research capacity. The Middle Eastern culture of hospitality greatly benefited the project team. CONCLUSION:Cultural differences impact multiple aspects of epidemiologic research and should be respectfully addressed. Conducting international population-based environmental research poses many challenges; these challenges can be met successfully with careful planning, cultural knowledge, and flexibility. Lessons learned are applicable to interdisciplinary research all over the world. The research conducted will benefit the environmental and public health agencies of the UAE and provide the nation's leadership with country-specific environmental health data that can be used to protect the public's health in a rapidly changing environment.

BACKGROUND: Comprehensive global data on the health effects of indoor air pollutants are lacking. There are few large population-based multi-air pollutant health assessments. Further, little is known about indoor air health risks in the Middle East, especially in countries undergoing rapid economic development.OBJECTIVES: To provide multifactorial indoor air exposure and health data, we conducted a population-based study of indoor air pollution and health in the United Arab Emirates (UAE).METHODS: We conducted a cross-sectional study in a population-based sample of 628 households in the UAE. Indoor air pollutants [sulfur dioxide (SO2), nitrogen dioxide (NO2), hydrogen sulfide (H2S), formaldehyde (HCHO), carbon monoxide (CO), and particulate matter] were measured using passive samplers over a 7-day period. Health information was collected from 1,590 household members via in-person interviews.RESULTS: Participants in households with quantified SO2, NO2, and H2S (i.e., with measured concentrations above the limit of quantification) were twice as likely to report doctor-diagnosed asthma. Participants in homes with quantified SO2 were more likely to report wheezing symptoms {ever wheezing, prevalence odds ratio [POR] 1.79 [95% confidence interval (CI) 1.05, 3.05]; speech-limiting wheeze, POR 3.53 (95% CI: 1.06, 11.74)}. NO2 and H2S were similarly associated with wheezing symptoms. Quantified HCHO was associated with neurologic symptoms (difficulty concentrating POR 1.47; 95% CI: 1.02, 2.13). Burning incense daily was associated with increased headaches (POR 1.87; 95% CI: 1.09, 3.21), difficulty concentrating (POR 3.08; 95% CI: 1.70, 5.58), and forgetfulness (POR 2.68: 95% CI: 1.47, 4.89).CONCLUSIONS: This study provides new information regarding potential health risks from pollutants commonly found in indoor environments in the UAE and other countries. Multipollutant exposure and health assessments in cohort studies are needed to better characterize health effects of indoor air pollutants.

Background and Aims:In the last forty years, the UAE has undergone rapid transition to become an industrialized nation. Little is known about theindoor air pollutant exposures and potential health effects in the Arab Gulf region. Methods: We conducted a cross-sectional study in a stratified sample of 628 households in urban and rural areas and all seven emirates in the UAE from October 2009 to May 2010.Indoor air pollutants (nitrogen dioxide NO2, sulfur dioxide SO2, hydrogen sulfide H2S) were measured using passive diffusion samplers over a seven-day period in a common living area.Information on environmental exposures, respiratory symptomswas collected from selected household members in each family via in-person interviews using validated questionnaires. Results: A total of 1590 adults (n=1009), adolescents (n=330), and children (n=253) from 628 households were surveyed. Thirty percent (n=548) of our study sample lived in households with detectable sulfur dioxide (range 0.010-0.507ppm), and 9% lived in households with detectable indoor NO2 (range 0.006-048ppm). Indoor SO2 was associated with ever wheezing, Prevalence odds ratio (POR) 1.79 [95% confidence interval (CI) 1.05, 3.05];wheezing in the last 4 weeks POR 4.63 [95% CI 1.33-16.19]; speech limiting wheeze in the last 12 months 3.53 [95% CI 1.06-11.74]; and diagnosed asthma POR 1.95 [95% CI 1.13-1.36]. Indoor NO2 was associated with diagnosed asthma(POR) 2.34 [95% Confidence Interval (CI) 1.11, 4.93];dry cough not from cold, POR 1.90 [95%CI 1.0-3.60];and sinus infections in the last 12 months POR 1.77 [95% CI 1.07-2.94]. Conclusions: Our research found in this Gulf nation population, those living inhouseholds with measurable SO2 and NO2 experienced increased frequency of respiratory related symptoms and diagnosed asthma.Further research is needed to better characterize both the sources of exposure and the health effects of indoor air pollutants in the home.

This chapter contains sections titled: Introduction Principles of Filter Sampling Aerosol Measurement Filters Filtration Theory Filter Artifacts Filter Selection List of Symbols References

Monitoring gas-phase pollutants is essential to understand exposure patterns and to establish a link between exposure and health. Measurement of the low concentrations found outdoors or in indoor living space normally requires large, expensive instruments that use electrical power. In this study, colorimetric passive diffusion tubes, normally used to monitor high concentrations of airborne contaminants in the workplace for sampling periods of a few hours, were evaluated to measure much lower concentrations of the same pollutants for periods of up to 1 wk. These tubes are small, inexpensive, and require no electrical power. Responses of diffusion tubes for carbon monoxide (CO), hydrogen sulfide (H(2)S), nitrogen dioxide (NO(2)), sulfur dioxide (SO(2)), and benzene were studied. Low pollutant concentrations measured with passive diffusion tubes matched reasonably well with true concentrations for all pollutants except NO(2). These results suggest that passive diffusion tubes can provide an inexpensive, unobtrusive, and effective method to monitor low pollutant concentrations. Passive diffusion tubes may be particularly useful in surveys where the spatial variability in concentrations is high and where the cost of traditional monitoring instruments is a concern.