Levels Of Airborne Particulate Matter Research Articles

Exhaust and non-exhaust contributions from road transport to PM10 at a Southern European traffic site

It is a well – established fact that road traffic is one of the main contributors to ambient levels of airborne particulate matter (APM). This study was carried out at a traffic site in which the PM10 levels are monitored all year round. A trend analysis of these levels revealed that over a decade there was no discernible trend, with the PM10 concentrations normally hovering around the EU limit values. In 2018, one of these limit values was exceeded. The contribution of traffic at the site was therefore investigated through a chemical speciation of 209 PM10 samples collected throughout this year. The speciation data were used in a source apportionment exercise in which the output of the PMF model was further refined using the lesser–known, constraint weighted non – negative matrix factorization (CW – NMF) model. This technique enabled the isolation of two factors clearly related to traffic, which were labelled as “exhaust contribution” (responsible for 3.4% of the PM10), “tire/brake wear contribution” (contributing 17% of the PM10). Additionally, a factor including both traffic resuspended dust and crustal material was also isolated and labelled “road dust/crustal” factor. The two contributors to the factor jointly contribute 18% to the PM10 and the contribution of the traffic resuspended dust was estimated at 7.3%. The traffic resuspended component of this factor together with the “tire/brake wear contribution” jointly make up the non-exhaust contribution of traffic – derived dust. Consonant with what has been known for quite some time, the exhaust fraction is the minor component of traffic PM10. It is therefore, clear that policies aimed at controlling traffic derived PM10 pollution at the receptor will have a minimal effect unless the non – exhaust emissions are adequately controlled.

Factors influencing indoor air pollution in buildings using PCA-LMBP neural network: A case study of a university campus

This study investigated indoor air quality (IAQ) and its association with building characteristics and environmental factors in eleven different campus buildings in Gainesville, Florida. Integrated indoor and outdoor sensor systems are built and installed to measure the levels of airborne particulate matter (PM2.5 and PM10), nitrogen dioxide (NO2), ozone (O3), relative humidity (RH), and temperature continuously in 10 min intervals for two weeks for each case building. Twenty building-related characteristics were collected through a walkthrough-based survey, HVAC historical data, and construction drawings. Through these data, a PCA-assisted Levenberg-Marquardt Backpropagation (LMBP) neural network model was developed for rapidly and accurately analyzing and predicting the interaction between IAQ and its affecting factors. Factors with significant contributions to indoor exposure were may mostly be determined by outdoor sources. This is evidenced by the strong associations that were found between indoor PM(2.5-10) and O3 values and their corresponding outdoor values and factors, including distance from the major traffic (DFMT), cracks occurring, outdoor temperature, and humidity. Indoor NO2 concentrations were affected by DFMT, indoor O3, indoor RH, number of air grilles, room volume, and window-to-wall ratio. Also, the comparison shows that the PCA-LMBP model outperforms the traditional BP-ANN and multi-linear regression methods. The average values of 1.34, 2.53, and 4.86 were obtained for the root-mean-square error (RMSE) of PCA-LMBP, BP-ANN, and MLR models, respectively. These results can be accordingly referred for the follow-up studies that analyze IAQ in similar building and environmental conditions.

Status of TNF-α and IL-6 as pro-inflammatory cytokines in exhaled breath condensate of late adolescents with asthma and healthy in the dust storm and non-dust storm conditions.

Exposure to airborne particulate matter (PM) can be considered as an important risk factor for human health. Some cytokines have been recognized as the biomarkers of exposure to air pollution. Experimental studies indicate that PM exposure could be associated with inflammation. Thus, the purpose of this study was to evaluate whether the exposure to air PM is associated with biomarkers of inflammation. The specific aim of this study was to determine the correlation between airborne PM levels and IL-6 and TNF-α as airway inflammation biomarkers among two groups of late adolescents in northwest of Iran. This study included 46 subjects, comprising 23 asthmatic subjects and 23 non-asthmatic persons. Environmental PM (PM10, PM2.5 and PM1) levels were measured in dust storm and non-dust storm days during both cold and warm seasons. Following the sampling of PM, Two pro-inflammatory cytokines of IL-6 and TNF-α in exhaled breath condensate (EBC) were also determined in the EBC samples via commercial ELISA kits. Daily mean ambient air PM10, PM2.5 and PM1 concentrations during the dust storm days was 221.79, 93.13 and 25.52 μg m-3 and in non-dusty days 48.37, 18.54 and 6.1 μg m-3, respectively. Biomarkers levels were significantly (p < 0.001) higher in asthmatic students compared to the non-asthmatic subjects. EBC cytokines levels were increased in dust storm days compared to the non-dusty days (p < 0.001) and were positively correlated with different size of ambient PM concentration. Dust storm conditions can increase the pro-inflammatory cytokines and cause adverse effects on pulmonary health and lung tissue damage.

Understanding the pathogenesis of occupational coal and silica dust-associated lung disease.

Workers in the mining and construction industries are at increased risk of respiratory and other diseases as a result of being exposed to harmful levels of airborne particulate matter (PM) for extended periods of time. While clear links have been established between PM exposure and the development of occupational lung disease, the mechanisms are still poorly understood. A greater understanding of how exposures to different levels and types of PM encountered in mining and construction workplaces affect pathophysiological processes in the airways and lungs and result in different forms of occupational lung disease is urgently required. Such information is needed to inform safe exposure limits and monitoring guidelines for different types of PM and development of biomarkers for earlier disease diagnosis. Suspended particles with a 50% cut-off aerodynamic diameter of 10 µm and 2.5 µm are considered biologically active owing to their ability to bypass the upper respiratory tract's defences and penetrate deep into the lung parenchyma, where they induce potentially irreversible damage, impair lung function and reduce the quality of life. Here we review the current understanding of occupational respiratory diseases, including coal worker pneumoconiosis and silicosis, and how PM exposure may affect pathophysiological responses in the airways and lungs. We also highlight the use of experimental models for better understanding these mechanisms of pathogenesis. We outline the urgency for revised dust control strategies, and the need for evidence-based identification of safe level exposures using clinical and experimental studies to better protect workers' health.

Occupational safety and health hazards in artisanal gold mines in western and Nyanza region, Kenya

Artisanal and small-scale gold mining (ASSGM) has experienced rapid growth due to mineral value and increasing poverty level in western and Nyanza regions in Kenya. The sub-sector has hazardous tasks occasioned by chemical exposures to such substances as mercury, physical strain and repetitive movements associated with extractive tasks challenge which vary from region to region and site to site. This paper reports findings of a study conducted on ASSGM in Kakamega (Roster mine and Ikolomani) and Migori (Masara-Suna West and Francis - Suna East) counties to assess workplace safety, health risk and good health practice among a population of one thousand four hundred (1400) miners and non-miners to identify and determine levels of health hazard in the sector. Descriptive cross-sectional design that involved stratified sampling technique with three broad stages was used: dividing mining and non-mining population in sub-groups (miners, foremen/supervisors, and head of households) at sites in administering to them research instrument using a simple random technique. Levels of airborne particulate matter (PM2.5 and PM10) were determined both at mining sites and away from mining sites using low cost monitor sensor (PA-11-SD Purple air sensor). The low-cost monitor sensor data was corrected using collocational data obtained using a continuous particulate monitor (BAM 1020) reference monitor in a similar location. SPSS version 25.0 was used to analyse qualitative data. The study found that common sources of hazards included handling elemental mercury with bare hands during amalgamation and exposure to fumes during refining raw sponge-like gold. Aaverage 24-hour variation cycle for (PM2.5 and PM10) was 117.11±14.47 and 195.18±15.35 μg/m3 in ambient air respectively at all mining sites. Histograms were used to present frequency distribution of variations for (PM2.5 and PM10) from mining activity. The average humidity and temperature variations of artisanal gold mining were in the range of (45-35) percentage (% RH) and (26-28)0C respectively. The study concluded that there were high risk cycle exposures to airborne particulate matter contaminants at artisanal gold mining sites as compared to non- mining sites. The study recommends that the county government should give priority to developing safe guidelines to ASSGM. The central government should also come up with guidelines on Occupational Safety and Health in artisanal gold mining to facilitate compliance with OSH requirements in the sector and offer effective participative training.

Studying the effect of particulate matter as SARS-CoV-2 transmitters.

Background: Studies of risk factors are especially valuable at this difficult time in the midst of a pandemic. High levels of particulate matter (PM) represent a serious risk factor on health. While this is a direct impact on health, indirect effects are worth considering too.Design and methods: The aim of this study was to investigate the role of PM in the transmission of viruses, especially SARSCoV- 2. Also, we sought to understand dynamics of PM in still air at high and low altitudes. Historic AQI and physical PM measurements were collected between August and September 2020 using air quality detector. Potential correlations between the number of total confirmed COVID-19 cases and average air quality index (AQI) from varied geographic locations were also assessed.Results: Airborne PM levels were weakly associated with COVID-19 cases after analysing 77 territories. PM remained longer in the air at high altitudes compared to measurements made at sea level. This suggests that the link between PM and COVID- 19 transmission could be aggravated in areas of high altitude.Conclusions: This article highlights that particulate matter can be involved in SARS-CoV-2 transmission. However, confounding factors may have impacted the association between the two variables. These findings can serve as a foundation for future studies on the effect of air pollutants and fine particulate matter on viral transmission. Significance for public health The impact of high levels of particulate matter on health is well documented. However, growing studies on its indirect effect by transmitting viruses warrant further considerations. In this article, we studied particulate matter in high and low altitudes to better predict the dynamics of particulate matter in still air. Then, correlation between air quality index and COVID-19 cases were made. Backed by some investigations, the positive correlation suggests that particulate matter could play a role in viral transmission including SARS-CoV-2. Therefore, studies of the direct and indirect effect of particulate matters are significant and suggest imposing preventive measures such as air quality monitoring.

Wintertime Air Quality in Lumbini, Nepal: Sources of Fine Particle Organic Carbon

The Indo-Gangetic Plains (IGP) experience high levels of airborne particulate matter (PM), especially during the dry season. Contributing to PM are natural and anthropogenic emissions and the atmospheric transformation of gases to form particles. Regional smog events occur frequently during wintertime and provide an atmospheric medium for aerosol processing. Here, we investigate the chemical composition and sources of PM at a representative site in the northern IGP during the second Nepal Ambient Monitoring and Source Testing Experiment (NAMaSTE 2). In Lumbini, Nepal, the 24 h average PM2.5 and PM10 concentrations ranged 48–295 and 60–343 μg m–3, respectively, from December 20, 2017, to January 1, 2018. On average (± standard deviation), PM2.5 was composed of 39 ± 7% organic carbon (OC), 5 ± 2% elemental carbon (EC), and 20 ± 6% secondary inorganic ions (ammonium, nitrate, and sulfate), 2.0% chloride, and 1.3% potassium. Biomass burning was a major PM source, indicated by a median levoglucosan concentration of 3.5 μg m–3. Secondary organic aerosol (SOA) derived from biomass burning was indicated by high concentrations of nitromonoaromatic compounds (e.g., 4-nitrocatechol peaking at 435 ng m–3). During periods of fog, characterized by high relative humidity (RH) and relatively low solar radiation, nitroaromatic concentrations dropped despite levoglucosan remaining high, indicating that their formation was suppressed. Chemical signatures of SOA indicated that volatile organic compound (VOC) precursors were primarily combustion-derived, with small contributions from biogenic VOC. Through molecular markers and chemical mass balance (CMB) modeling, sources of PM2.5 OC were identified as cow dung burning (24 ± 16%), other biomass burning (20 ± 7%), plastic/garbage burning (4.7 ± 3.2%), vehicle emissions (3.1 ± 1.4%), coal combustion (0.3 ± 0.2%), and SOA from monoaromatic VOC (4.1 ± 0.8%), diaromatic VOC (8.9 ± 4.0%), cresol (0.3 ± 0.4%), isoprene (0.4 ± 0.2%), monoterpenes (1.5 ± 0.6%), and sesquiterpenes (3.2 ± 0.7%). Understanding the levels of PM in Lumbini, along with its chemical composition and sources of OC, contributes to a better understanding of regional air quality episodes in the IGP.

INDOOR SHORT-TERM EXPOSURE TO AIRBORNE PARTICULATE MATTER FROM TRADITIONAL COOKSTOVES IN RURAL AREAS OF MALAWI. A CASE OF NSABWE AND BAULENI VILLAGES

This study was carried out to assess the short-term exposure to respirable particulate matter (PM2.5) from biomass combustion. A total of 24 households were sampled from two rural villages in Lilongwe, viz Nsabwe and Bauleni villages. Levels of particulate matter were measured using a portable gas detector. Indoor mean concentrations of PM2.5 ranged from 457 to 698 µg/m3, with no significant difference between the two villages, suggesting exposure to similar levels of airborne particulate matter. The observed levels are far above the recommended WHO limit for indoor air, posing a great health risk, more especially to the women and children who frequently visit the cooking areas. There is therefore need to widen appropriate intervention measures to reduce the current levels of indoor air pollution in the rural areas.

Changes in air pollution and attitude to fireworks in Beijing

Abstract Fireworks used in both public and private displays can cause brief, but extraordinarily high levels of airborne particulate matter. New Year festivities in China, have for many years led to sharp spikes in air pollution just after midnight. Potential health impacts and broader environmental concerns have resulted in increasingly stringent regulation of fireworks. While in the past these have been ineffective because of mercantile and stakeholder pressures to retain the celebratory use of fireworks, regulations are now more widely enforced. Measurements of fine particulate matter show considerable year-to-year variation, with the presence of inversions an important determinant of the firework-derived spike in the early morning on New Year's Day. Nevertheless, overall improvements are evident in recent years (2017–2019), although these are more dramatic for the inner parts of Beijing (491–126 μg m−3) compared to areas outside the 5th Ring Road (488–203 μg m−3). There is parallel evidence of lower emissions from fireworks reflected in decreasing sales, 95 to 2.9 myriaboxes from 2011 to 2019 and lower accumulation of firework debris after the celebrations. Posts to SinaWeibo hint at a growing support for reduced firework use among Beijing's netizens, so consumer perceptions have moved to give more support to regulation. There is also positive commentary on social media about the resultant healthier environment. Official posts stress the need for care with fireworks and note enhanced vigilance over illegal sales fireworks. Although top-down, the approach seems to have met with some success in reducing pollution from fireworks in Beijing.

Diurnal trends in redox characteristics of water-soluble and -insoluble PM components

Densely populated cities with a compact urban built environment have concerns over health risks derived from high levels of airborne particulate matter (PM) exposure. Understanding the association between PM and reactive oxygen species (ROS) is an important step towards unravelling the mechanisms behind. This study investigated the role of time-integrated PM sampling on cellular toxicity mechanism on a diurnal scale. The sampling took place in a highly urbanized part of Hong Kong at two contrast roadside and background sites, with simultaneous solid-PM and semi-volatile-PM (SV-PM) collection in both summer and winter seasons. A sampling day consisted three sampling intervals of 6 h each – 04:00–10:00, 12:00–18:00 and 20:00–02:00 h, representing morning rush hours, afternoon and night periods, respectively. Water and organic extracts of PM were prepared, with and without filtration, and exposed to RAW264.7 and A549 cell lines on a dose and time-dependent manner. Solid-PM and SV-PM contribution to total PM2.5 mass concentration was 9:1, with much higher SV-PM fraction at roadside over urban background (p < 0.001, n = 36). Also, the SV-PM mass concentration increased by 10–20% during 20:00–02:00 h compared to morning and afternoon sampling periods. Organic PM extract was observed to cause 23–29% higher cell death compared to water-soluble PM, which is complemented with increased ROS production in both cell lines. The cellular damage caused by oxidative stress, determined from increased HO-1 and TNF-α expression in RAW264.7 was higher compared to the A549, which demonstrated the greater induction of toxicity from organic PM extract over soluble PM. Similarly, the SV-PM induced greater than 2-fold cellular ROS generation on PM mass basis compared to solid-PM. Lack of phagocytic action in A549 compared to RAW264.7 suggested novel toxicity routes for water-soluble and organic PM that can be expected to occur during human PM inhalation-bronchi-alveolar exposure.

Particulate matter mitigation via plants: Understanding complex relationships with leaf traits

Elevated levels of airborne particulate matter (PM) pose health risks to populations living in many cities worldwide. To remediate the impact of air pollution, urban greening has been increasingly explored as a possible way to remove PM from the surroundings. However, existing research focuses mainly on species-specific assessments within temperate climates that may not necessarily grow outside of their local regions. To address sampling limitations associated with the great species diversity in the tropics, our study quantified three key functional traits—leaf hairiness, average leaf area (ALA) and specific leaf area (SLA)—each spanning a wide range of values across 20 tropical species. Wind-tunnel experiments were used to assess surface deposition velocity on leaves; the size fractions PM10 and PM2.5 were measured through multiple rounds of filtration and gravimetric analysis. The effects of upper- and lower-surfaces of leaves on deposition velocity and their interactions with hairiness were also investigated. Results show that greater upper-surface hairiness and a low SLA were consistent predictors of higher deposition velocity for both PM-size fractions. Hairs on leaves serve as obstacles while low SLA tends to be associated with smaller and thicker leaves, together favoring the deposition and retention of PM. The possible mechanisms behind important plant traits and their interactions are discussed. By testing quantifiable effects of specific plant traits, we provide generalizable findings that may be applied to urban greening efforts. Future work to consider other gaseous pollutants and plant-scale effects can help ensure a more comprehensive evaluation of plant suitability for pollutant mitigation.

Environmental Electronic Vape Exposure from Four Different Generations of Electronic Cigarettes: Airborne Particulate Matter Levels

Electronic cigarettes (e-cigs) were introduced into the market in 2006 and their technological features have evolved substantially over time. Currently, there are four different generations of e-cigs that are broadly considered less harmful than the use of combusted tobacco products although passive exposure to aerosols often occurs in public spaces and indoor environments. The study aim was to evaluate the levels of airborne particulate matter (PM) emitted during the use of all the four generations of e-cigs, testing different use modalities. PM10, PM4, PM2.5 and PM1 were measured through a Dusttrak ™ II Aerosol Monitor, for a total of 20 independent experiments. All tested e-cigs devices produced PM during their use, and PM10 was almost made of PM1 size fraction. In addition, we observed a progressive increase in PM emission from the first to the fourth generation, and an upward trend of PM1 emitted by the fourth generation e-cig with an increase in the operating power. The results showed that, whatever the model adopted, passive vaping does occur. This finding supports the need for legislative interventions to regulate the e-cigs use in public places and other enclosed environments, in order to protect the health of any subject who is potentially exposed.

The Association between Particulate Air Pollution and Respiratory Admissions amongst Young Children in Hanoi, Vietnam

Background/Aim: In recent decades, Hanoi has faced several serious air pollution issues, especially high levels of airborne particulate matter including PM10, PM2.5, and PM1. However, there has bee...

The association between particulate air pollution and respiratory admissions among young children in Hanoi, Vietnam

While the effects of ambient air pollution on health have been studied extensively in many developed countries, few studies have been conducted in Vietnam, where the population is exposed to high levels of airborne particulate matter. The aim of our study was to examine the short-term effects of PM10, PM2.5, and PM1 on respiratory admissions among young children in Hanoi. Data on daily admissions from the Vietnam National Hospital of Paediatrics and daily records of PM10, PM2.5, PM1 and other confounding factors as NO2, SO2, CO, O3 and temperature were collected from September 2010 to September 2011. A time-stratified case-crossover design with individual lag model was applied to evaluate the associations between particulate air pollution and respiratory admissions. Significant effects on daily hospital admissions for respiratory disease were found for PM10, PM2.5 and PM1. An increase in 10μg/m3 of PM10, PM2.5 or PM1 was associated with an increase in risk of admission of 1.4%, 2.2% or 2.5% on the same day of exposure, respectively. No significant difference between the effects on males and females was found in the study. The study demonstrated that infants and young children in Hanoi are at increased risk of respiratory admissions due to the high level of airborne particles in the city's ambient air.

Transcriptomic Analyses of the Biological Effects of Airborne PM2.5 Exposure on Human Bronchial Epithelial Cells.

Epidemiological studies have associated high levels of airborne particulate matter (PM) with increased respiratory diseases. In order to investigate the mechanisms of air pollution-induced lung toxicity in humans, human bronchial epithelial cells (16HBE) were exposed to various concentrations of particles smaller than 2.5 μm (PM2.5) collected from Beijing, China. After observing that PM2.5 decreased cell viability in a dose-dependent manner, we first used Illumina RNA-seq to identify genes and pathways that may contribute to PM2.5-induced toxicity to 16HBE cells. A total of 539 genes, 283 up-regulated and 256 down-regulated, were identified to be significantly differentially expressed after exposure to 25 μg/cm2 PM2.5. PM2.5 induced a large number of genes involved in responses to xenobtiotic stimuli, metabolic response, and inflammatory and immune response pathways such as MAPK signaling and cytokine-cytokine receptor interaction, which might contribute to PM2.5-related pulmonary diseases. We then confirmed our RNA-seq results by qPCR and by analysis of IL-6, CYP1A1, and IL-8 protein expression. Finally, ELISA assay demonstrated a significant association between exposure to PM2.5 and secretion of IL-6. This research provides a new insight into the mechanisms underlying PM2.5-induced respiratory diseases in Beijing.

Effects Of Wildfire Smoke On Community Population Health In The Western Us

Introduction: Wildfires may be a hazard to human health due to the high levels of airborne particulate matter (PM) released from wildfire smoke. However, the health effects of wildfire-emitted fine particles are not well understood and most of the current studies on wildfire and health are based on single wildfire episode. Further, wildfires are anticipated to increase under climate change. This study uses large-scale wildfire smoke data over six years to estimate the health effect of PM specifically from wildfire smoke in the Western US. Methods: We estimated daily PM2.5 concentrations from wildfires (2004-2009) for every county in the Western US (561 counties) using outputs from the state-of-science GEOS-Chem (v9-01-03) global chemical transport model that utilized daily emissions from the Global Fire Emissions Database (GFED3). We demonstrated spatial exposure patterns in an interactive map. The wildfire-specific PM2.5 data were linked to the Medicare data (=65y) in 122 most populated Western US counties. We used a generalized linear mixed model to estimate the relative risk of hospital admissions on days with high wildfire-specific PM compared to matched comparison days for respiratory and cardiovascular admissions. Results: We estimate that about 57 million people were exposed to wildfire smoke between 2004 and 2009 in the Western US, among which 12% are =64 years. Among the Medicare population, respiratory hospital admissions increased 5.0% on days with wildfire smoke (95% CI: 0.91%-9.26%) compared to non-fire days. Cardiovascular hospital admissions did not show significant association with wildfire smoke. Conclusion: This multi-year, multi-county study is the most comprehensive study to date on wildfire smoke and public health in North America. Results indicate health impacts of PM2.5 from wildfires in elderly population in the Western US. The results provide policy reference on establishing or modifying public health programs in susceptible regions.

In situ acidity and pH of size-fractionated aerosols during a recent smoke-haze episode in Southeast Asia.

The characterization of aerosol acidity has received increased attention in recent years due to its influence on atmospheric visibility, climate change and human health. Distribution of water soluble inorganic (WSI) ions in 12 different size fractions of aerosols was investigated under two different atmospheric conditions (smoke-haze and non-haze periods) in 2012 using the Micro-Orifice Uniform Deposit Impactor (MOUDI) and nano-MOUDI for the first time in Singapore. To estimate the in situ acidity ([H(+)]Ins) and in situ aerosol pH (pHIS), the Aerosol Inorganic Model version-IV under deliquescent mode of airborne particles was used at prevailing ambient temperature and relative humidity. The study revealed an increase in the levels of airborne particulate matter (PM) mass and concentrations of WSI ions for all size fractions during the smoke-haze period, which was caused by the trans-boundary transport of biomass burning-impacted air masses from Indonesia. A bimodal distribution was observed for concentrations of SO4(2-), NO3(-), Cl(-), K(+) and Na(+), whereas concentrations of NH4(+), Ca(2+) and Mg(2+) showed a single mode distribution. The concentration of WSI ions in PM1.8 during the smoke-haze period increased by 3.8 (for SO4(2-)) to 10.5 (for K(+)) times more than those observed during the non-haze period. The pHIS were observed to be lower during the smoke-haze period than that during the non-haze period for all size fractions of PM, indicating that atmospheric aerosols were more acidic due to the influence of biomass burning emissions. The particles in the accumulation mode were more acidic than those in the coarse mode.

Assessing the regional impact of indonesian biomass burning emissions based on organic molecular tracers and chemical mass balance modeling

Abstract. Biomass burning activities commonly occur in Southeast Asia (SEA), and are particularly intense in Indonesia during the dry seasons. The effect of biomass smoke emissions on air quality in the city state of Singapore was investigated during a haze episode in October 2006. Substantially increased levels of airborne particulate matter (PM) and associated chemical species were observed during the haze period. Specifically, the enhancement in the concentration of molecular tracers for biomass combustion such as levoglucosan by as much as two orders of magnitude and the diagnostic ratios of individual organic compounds indicated that biomass burning emissions caused a regional smoke haze episode due to their long-range transport by prevailing winds. With the aid of air mass backward trajectories and chemical mass balance modeling, large-scale forest and peat fires in Sumatra and Kalimantan were identified as the sources of the smoke aerosol, exerting a significant impact on air quality in downwind areas, such as Singapore.

Study of active duty military for pulmonary disease related to environmental deployment exposures (STAMPEDE).

Because of increased levels of airborne particulate matter in Southwest Asia, deployed military personnel are at risk for developing acute and chronic lung diseases. Increased respiratory symptoms are reported, but limited data exist on reported lung diseases. To evaluate new respiratory complaints in military personnel returning from Southwest Asia to determine potential etiologies for symptoms. Returning military personnel underwent a prospective standardized evaluation for deployment-related respiratory symptoms within 6 months of returning to their duty station. Prospective standardized evaluation included full pulmonary function testing, high-resolution chest tomography, methacholine challenge testing, and fiberoptic bronchoscopy with bronchoalveolar lavage. Other procedures including lung biopsy were performed if clinically indicated. Fifty patients completed the study procedures. A large percentage (42%) remained undiagnosed, including 12% with normal testing and an isolated increase in lavage neutrophils or lymphocytes. Twenty (40%) patients demonstrated some evidence of airway hyperreactivity to include eight who met asthma criteria and two with findings secondary to gastroesophageal reflux. Four (8%) additional patients had isolated reduced diffusing capacity and the remaining six had other miscellaneous airway disorders. No patients were identified with diffuse parenchymal disease on the basis of computed tomography imaging. A significant number (66%) of this cohort had underlying mental health and sleep disorders. Evaluation of new respiratory symptoms in military personnel after service in Southwest Asia should focus on airway hyperreactivity from exposures to higher levels of ambient particulate matter. These patients may be difficult to diagnose and require close follow-up.

Concentrations and Size Distributions of Airborne Particulate Matter and Bacteria in an Experimental Aviary Laying-Hen Chamber

<abstract> <bold><sc>Abstract.</sc></bold> High levels of airborne particulate matter (PM) and bacteria may exist in animal housing, which can be detrimental to the health of animals and workers. The sizes of these bioaerosols determine their aerial transport behaviors and depositions in the respiratory tracts of animals and humans. However, little is known regarding the size distribution of airborne PM and bacteria in livestock houses, especially in alternative animal housing systems that aim to enhance animal welfare, such as aviary hen-housing systems. The study reported here was therefore conducted to characterize the concentrations and size distributions of airborne bacteria (in count) and PM (both in count and in mass) in a pilot-scale aviary laying-hen chamber. Thirty-four laying hens were kept in the environmentally controlled aviary chamber (L × W × H = 2.2 × 2.3 × 2.4 m) for three months. The hens were given a 16L:8D photoperiod (lights on at 6:00 h and off at 22:00 h) and access to the litter floor from 12:00 h to 22:00 h daily. Airborne bacteria and PM were simultaneously sampled for 15 min at 1.5 m above the litter floor every fourth day at 5:45 h, 9:45 h, 13:45 h, 17:45 h, and 21:45 h. Concentrations of airborne bacteria at six size ranges (0.65 to 1.1 μm, 1.1 to 2.1 μm, 2.1 to 3.3 μm, 3.3 to 4.7 μm, 4.7 to 7.1 μm, and >7.1 μm) and PM concentrations (0.523 to 20.535 μm) were determined. The daily mean (±SD) concentrations of PM count, PM mass, and airborne bacteria were 1.70 (±0.66) × 10⁷ particles m^-3, 1.12 (±0.47) mg m^-3, and 3.39 (±2.38) × 10⁵ cfu m^-3, respectively. Concentrations of airborne PM and bacteria during the litter-access period (12:00 to 22:00 h) were significantly higher than those during the rest of the day when the hens were off the floor (p < 0.05). Median diameter and geometric standard deviation (GSD) for the PM count (0.523 to 20.535 μm) were 2.11 and 2.34 μm, respectively. Median diameter and GSD for the PM mass (0.523 to 20.535 μm) were 7.45 and 4.58 μm, respectively. PM <10 μm accounted for more than 95% of the total PM count, whereas PM >2.5 μm accounted for more than 90% of the total PM mass, in the size range of 0.523 to 20.535 μm. The majority (>95%) of the airborne bacteria were carried by particles >3.3 μm. Airborne bacteria count concentration was positively related to PM mass concentration (p < 0.05) with a slope of 3.84 (±2.70) × 10⁵ cfu mg^-1 PM. Results of the study are useful for improving understanding of transport behaviors of aerosols in aviary hen systems, assessing potential respiratory risks to humans and animals, and exploring mitigation techniques.