Continuous PM2 Research Articles

Association between individual PM2.5 exposure and DNA damage in traffic policemen.

The aim of this study was to explore the association between individual PM2.5 and DNA damage in traffic policemen. The participants included 110 traffic policemen and 101 common populations. The continuous 24-hour individual PM2.5 measurement was performed in participants. BPDE (benzo[a]pyrene 7,8-diol-9,10-epoxide)-DNA adducts and 1-OHP were detected. The average concentration of 24-hour personal PM2.5 for traffic policemen was significantly higher than that in the control group. PM2.5 exposure is associated with a 1.1% increase in 1-OHP and 0.8% increase in BPDE-DNA adducts after adjusted for body mass index, educational time period, and alcohol intake. Exposure group has 2.04 times higher of 1-OHP and 1.25 times higher of BPDE-DNA adducts when compared to the control group. These results demonstrated that traffic policemen have been a high-risk group suffering DNA damage because of the high PM2.5 exposure.

Using Global Positioning Systems (GPS) and temperature data to generate time-activity classifications for estimating personal exposure in air monitoring studies: an automated method.

BackgroundPersonal exposure studies of air pollution generally use self-reported diaries to capture individuals’ time-activity data. Enhancements in the accuracy, size, memory and battery life of personal Global Positioning Systems (GPS) units have allowed for higher resolution tracking of study participants’ locations. Improved time-activity classifications combined with personal continuous air pollution sampling can improve assessments of location-related air pollution exposures for health studies.MethodsData was collected using a GPS and personal temperature from 54 children with asthma living in Montreal, Canada, who participated in a 10-day personal air pollution exposure study. A method was developed that incorporated personal temperature data and then matched a participant’s position against available spatial data (i.e., road networks) to generate time-activity categories. The diary-based and GPS-generated time-activity categories were compared and combined with continuous personal PM2.5 data to assess the impact of exposure misclassification when using diary-based methods.ResultsThere was good agreement between the automated method and the diary method; however, the automated method (means: outdoors = 5.1%, indoors other =9.8%) estimated less time spent in some locations compared to the diary method (outdoors = 6.7%, indoors other = 14.4%). Agreement statistics (AC1 = 0.778) suggest ‘good’ agreement between methods over all location categories. However, location categories (Outdoors and Transit) where less time is spent show greater disagreement: e.g., mean time “Indoors Other” using the time-activity diary was 14.4% compared to 9.8% using the automated method. While mean daily time “In Transit” was relatively consistent between the methods, the mean daily exposure to PM2.5 while “In Transit” was 15.9 μg/m3 using the automated method compared to 6.8 μg/m3 using the daily diary.ConclusionsMean times spent in different locations as categorized by a GPS-based method were comparable to those from a time-activity diary, but there were differences in estimates of exposure to PM2.5 from the two methods. An automated GPS-based time-activity method will reduce participant burden, potentially providing more accurate and unbiased assessments of location. Combined with continuous air measurements, the higher resolution GPS data could present a different and more accurate picture of personal exposures to air pollution.

AN INITIAL ASSESSMENT OF WINTER TRENDS IN INDOOR PARTICULATE POLLUTION (PM2.5) IN THE GER REGION OF ULAANBAATAR, MONGOLIA

Background: Ulaanbaatar (UB) is home to 40% of Mongolia's 2.74 million residents and growing. A population boom combined with long heating seasons (~ 8 mo.), frequent temperature inversions, and a valley topography has led to dangerously high levels of PM2.5. For example, average wintertime PM2.5 concentrations in 2009-2010 were measured at 250 µg/m3. It is expected that such levels likely result in substantial increases in mortality and morbidity. It is also expected that indoor exposures contribute heavily to total exposure of PM2.5, as approximately half of UB's residents live in yurt-like gers and rely on a mix of dirty solid fuels (coal and wood) in poorly-combusting stoves to meet their heating needs. Aims: We undertook a pilot study of indoor and outdoor PM2.5 concentrations at ger homes using one of three stove types: a traditional coal stove, an "improved" coal stove (jointly subsidized by the US Millennium Challenge Corp. and the Mongolian government), and a locally piloted stove fueled by a coal-to-gas fuel called dimethyl ether (DME). In addition to validating PM2.5 monitoring methodologies for harsh winter environments (-40C), we explored the relationships between indoor and outdoor PM2.5 concentrations in the ger region of UB. Methods: Continuous PM2.5 and stove-use data were used to relate indoor and outdoor concentrations with household heating practices. At each of our sample gers, we placed one UC Berkeley Particle and Temperature Sensor (UCB-PATS) outside, one UCB-PATS inside the stove room (used for sleeping, eating, cooking, and general socializing), and fit all appliances that may emit considerable PM2.5 with UC Berkeley Stove Use Monitoring Sensors (SUMS). UCB-PATS were calibrated in field with filter colocations. Results & Conclusions: Filter samples collected during instrument calibration demonstrate 24-hr average PM2.5 concentrations as high as 610 µg/m3 (outdoor) and 275 µg/m3 (indoor), and 12-hr averages as high as 490 µg/m3 (indoor). Results by stove type, temperature, and other parameters will be presented.

Factors Influencing Indoor Air Quality in an Urban High-Rise Apartment Building

Background: Eighty percent of North Americans reside in cities and many urban dwellers live in high-rise apartments. However, few studies have examined pollutant concentrations in North American high-rise homes. The Ottawa Apartment Study examined factors influencing pollutant concentrations in an urban high-rise apartment building in downtown Ottawa, Ontario. Methods: We recruited apartments on lower, middle, and upper levels of the building. Neighboring units were included to assess vertical and horizontal infiltration. The study measured particulate matter (PM2.5), metals, and volatile organic compounds (VOCs), as well as air exchange. Continuous and integrated measurements were collected at approximately 30 sites including apartments (indoor and balconies), hallways, stairwells and the rooftop. Perfluorocarbon tracers were deployed to provide air exchange rates between indoor micro-environments as well as the outdoor air exchange rate. Building and occupant information were obtained through baseline and daily questionnaires. Results: Metal concentrations were typically higher on balconies and in hallways, while VOC concentrations were higher in apartments. PM2.5 concentrations did not vary significantly between micro-environments. There was some evidence to suggest that ambient concentrations of some metals and VOCs were higher at street level compared with upper level balconies. Outdoor PM2.5 from the balconies and central ventilation system were the major predictors of continuous PM2.5 concentrations in the apartments, with a smaller contribution explained by neighboring units. These results were consistent with the percent contribution based on air exchange measurements. Other factors influencing indoor concentrations (e.g., occupant activities and indoor sources) were similar to those for single family homes. Conclusions: Although many North Americans live in high-rise buildings, little information is available about their residential exposures. This study provides support for identifying strategies to reduce exposure in high-rise buildings.

Cardiovascular impacts and micro-environmental exposure factors associated with continuous personal PM2.5 monitoring

The US Environmental Protection Agency's (US EPA) Detroit Exposure and Aerosol Research Study (DEARS) has provided extensive data on human exposures to a wide variety of air pollutants and their impact on human health. Previous analyses in the DEARS revealed select cardiovascular (CV) health outcomes such as increase in heart rate (HR) associated with hourly based continuous personal fine particulate matter (PM2.5) exposures in this adult, non-smoking cohort. Examination of time activity diary (TAD), follow-up questionnaire (FQ) and the continuous PM2.5 personal monitoring data provided the means to more fully examine the impact of discreet human activity patterns on personal PM2.5 exposures and changes in CV outcomes. A total of 329 343 min-based PM2.5 personal measurements involving 50 participants indicated that ∼75% of these total events resulted in exposures <35 μg/m(3). Cooking and car-related events accounted for nearly 10% of the hourly activities that were identified with observed peaks in personal PM2.5 exposures. In-residence cooking often resulted in some of the highest incidents of 1 min exposures (33.5-17.6 μg/m(3)), with average peaks for such events in excess of 209 μg/m(3). PM2.5 exposure data from hourly based personal exposure activities (for example,, cooking, cleaning and household products) were compared with daily CV data from the DEARS subject population. A total of 1300 hourly based lag risk estimates associated with changes in brachial artery diameter and flow-mediated dilatation (BAD and FMD, respectively), among others, were defined for this cohort. Findings indicate that environmental tobacco smoke (ETS) exposures resulted in significant HR changes between 3 and 7 h following the event, and exposure to smells resulted in increases in BAD on the order of 0.2-0.7 mm/μg/m(3). Results demonstrate that personal exposures may be associated with several biological responses, sometimes varying in degree and direction in relation to the extent of the exposure.

Characterization and Source Apportionment of PM2.5 in an Urban Environment in Beijing

Daily 24-hour PM2.5 samples were collected continuously from January 1 to December 31, 2010. Elemental concentrations from Al to Pb were obtained using particle induced X-ray emission (PIXE) method. This was the first full year continuous daily PM2.5 elemental composition dataset in Beijing. Source apportionment analysis was conducted on this dataset using the positive matrix factorization method. Seven sources and their contributions to the total PM2.5 mass were identified and quantified. These include secondary sulphur– 13.8 μg/m 3 , 26.5%; vehicle exhaust– 8.9 μg/m 3 , 17.1%; fossil fuel combustion– 8.3 μg/m 3 , 16%; road dust– 6.6 μg/m 3 , 12.7%; biomass burning– 5.8 μg/m 3 , 11.2%; soil dust– 5.4 μg/m 3 , 10.4%; and metal processing– 3.1 μg/m 3 , 6.0%. Fugitive dusts (including soil dust and road dust) showed the highest contribution of 20.7 μg/m 3 in the spring, doubling those in other seasons. On the contrary, contributions of the combustion source types (including biomass burning and fossil fuel combustion) were significantly higher in the fall (14.2 μg/m 3 ) and in the winter (24.5 μg/m 3 ) compared to those in the spring and summer (9.6 and 8.0 μg/m 3 , respectively). Secondary sulphur contributed the most in the summer while vehicle exhaust and metal processing sources did not show any clear seasonal pattern. The different seasonal highs and lows from different sources compensated each other. This explains the very small seasonal variations (< 20%) in the total PM2.5.

Empirical relationship between particulate matter and aerosol optical depth over Northern Tien-Shan, Central Asia

Measurements were obtained at two sites in northern Tien-Shan in Central Asia during a 1-year period beginning July 2008 to examine the statistical relationship between aerosol optical depth (AOD) and of fine [PM2.5, particles less than 2.5 μm aerodynamic diameter (AD)] and coarse (PMCoarse, particles between 2.5 and 10 μm AD) mass concentrations and composition. The measurements represent the first extended particulate matter measurements in the northern Tien-Shan region of Central Asia. A sun photometer (Microtops II) was used to measure AOD from the surface, which is a widely used aerosol monitoring technique that is used in the AERONET network. In parallel, less routine measurements of continuous hourly PM2.5 data were obtained with the TEOM/FDMS whereas daily average PM2.5 and PM10 were obtained using URG-3000ABC samplers. Daily samples were collected on an every-other-day basis throughout the year. Since clouds interfere with the AOD measurement, a cloud screening procedure based on LIDAR measurements was applied to the AOD data and cloud impacted days were removed from the AOD data set. Depending on the season, the correlation coefficient (r) varied from 0.56 up to 0.87. Higher correlation coefficients between PM2.5 mass and AOD were observed during the spring and autumn periods and appeared to result from the transport of Asian dust (desert crustal material) particles from outside the area. One of the main source areas was the Taklimakan desert located in northwestern China. Linear regression results between AOD and PM2.5 are presented that allow for an estimate of PM2.5 mass concentrations at the surface based on the AOD data, which can be used to help interpret AOD measurements made in Central Asia and potentially other regions of the world.

Measurement and modeling of indoor air pollution in rural households with multiple stove interventions in Yunnan, China

In the developing world, indoor air pollution (IAP) created from solid fuel used in traditional biomass cook stoves is a leading contributor of poor respiratory health, global burden of disease, and greenhouse pollutant emissions. In the present study, we piloted an experimental cross-sectional monitoring and evaluation design with 30 households in rural Lijiang and Deqin counties in northwest Yunnan province, China. This approach offers the ability to examine the effectiveness of improved cook stove (ICS) programs with a much smaller sample size than the typical population based pre- and post-intervention study that requires a large sample representative of the population. Continuous PM2.5 was measured with the UCB (currently known as UCB-PATS) and the TSI DustTrak and continuous CO was measured with the HOBO CO logger. Using the traditional method of cooking and heating, mean 24-h PM2.5 and CO concentrations in the kitchen were measured in the range of 0.15–0.71 mg m−3 for PM2.5 and 3.0–11 ppm for CO. These concentrations were compared to using a combination of improved stoves in the kitchen where PM2.5 and CO concentrations were measured in the range of 0.08–0.18 mg m−3 for PM2.5 and 0.7–5.5 ppm for CO. These concentrations yielded statistically significant reduction in IAP when replacing the traditional fireplace or traditional stove with an improved stove combination. Finally, we show a strong correlation between CO and PM2.5 (R2 = 0.72–0.76). The combination of this experimental design along with the monitoring and evaluation protocol presented here may provide a robust framework to rapidly assess the effectiveness of ICS interventions in progress.

Wintertime particulate pollution episodes in an urban valley of the Western US: a case study

Abstract. This study investigates the causes of elevated PM2.5 episodes and potential exceedences of the US National Ambient Air Quality Standards (NAAQS) in Truckee Meadows, Nevada, an urban valley of the Western US, during winter 2009/2010, an unusually cold and snowy winter. Continuous PM2.5 mass and time-integrated chemical speciation data were acquired from a central valley monitoring site, along with meteorological measurements from nearby sites. All nine days with PM2.5 &gt; 35 μg m−3 showed 24-h average temperature inversion of 1.5–4.5 °C and snow cover of 8–18 cm. Stagnant atmospheric conditions limited wind ventilation while highly reflective snow cover reduced daytime surface heating creating persistent inversion. Elevated ammonium nitrate (NH4NO3) and water associated with it are found to be main reasons for the PM2.5 exceedances. An effective-variance chemical mass balance (EV-CMB) receptor model using locally-derived geological profiles and inorganic/organic markers confirmed secondary NH4NO3 (27–37%), residential wood combustion (RWC; 11–51%), and diesel engine exhaust (7–22%) as the dominant PM2.5 contributors. Paved road dust and de-icing materials were minor, but detectable contributors. RWC is a more important source than diesel for organic carbon (OC), but vice versa for elemental carbon (EC). A majority of secondary NH4NO3 is also attributed to RWC and diesel engines (including snow removal equipment) through oxides of nitrogen (NOx) emissions from these sources. Findings from this study may apply to similar situations experienced by other urban valleys.

無声放電型パティキュレートフィルタによる貴金属ゼロ・室温・大気圧条件下での連続的PM 除去の研究

無声放電型パティキュレートフィルタによる貴金属ゼロ・室温・大気圧条件下での連続的PM 除去の研究

Baltimore PM2.5 Supersite: highly time-resolved organic compounds—sampling duration and phase distribution—implications for health effects studies

As part of the Baltimore PM2.5 Supersite study, intensive three-hourly continuous PM2.5 sampling was conducted for nearly 4 weeks in summer of 2002 and as well in winter of 2002/2003. Close to 120 individual organic compounds have been quantified separately in filter and polyurethane foam (PUF) plug pairs for 17 days for each sampling period. Here, the focus is on (1) describing briefly the new sampling system, (2) discussing filter/PUF plugs breakthrough experiments for semi-volatile compounds, (3) providing insight into phase distribution of semi-volatile organic species, and (4) discussing the impact of air pollution sampling time on human exposure with information on maximum 3- and 24-h averaged ambient concentrations of potentially adverse health effects causing organic pollutants. The newly developed sampling system consisted of five electronically controlled parallel sampling channels that are operated in a sequential mode. Semi-volatile breakthrough experiments were conducted in three separate experiments over 3, 4, and 5 h each using one filter and three PUF plugs. Valuable insight was obtained about the transfer of semi-volatile organic compounds through the sequence of PUF plugs and a cut-off could be defined for complete sampling of semi-volatile compounds on only one filter/PUF plug pair, i.e., the setup finally used during the seasonal PM2.5 sampling campaign. Accordingly, n-nonadecane (C19) with a vapor pressure (vp) of 3.25 × 10(-4) Torr is collected with > 95% on the filter/PUF pair. Applied to phenanthrene, the most abundant the PAH sampled, phenanthrene (vp, 6.2 × 10(-5) Torr) was collected completely in wintertime and correlates very well with three-hourly PM2.5 ambient concentrations. Valuable data on the fractional partitioning for semi-volatile organics as a function of season is provided here and can be used to differentiate the human uptake of an organic pollutant of interest via gas- and particle-phase exposure. Health effects studies often relay on PM2.5 exposure measurements taken over 24 h or longer. We found that maximum 3-h concentrations are frequently two to five times higher than that found for maximum 24-h concentrations, an important aspect when considering that short-term exposure to higher air pollution levels are more likely to overpower defense mechanisms in the human lung with subsequent adverse effects even at lower pollutant levels.

The effect of proximity to major roads on indoor air quality in typical Australian dwellings

An Indoor Air Quality Study of residential dwellings was carried out in Melbourne, Australia, and a subset of the data was analysed to investigate the effect of proximity to major roads on indoor air quality (IAQ). Seven-day measurements of PM 10 , NO 2 , benzene, toluene, ethylbenzene and xylenes, along with continuous CO and PM 2.5 measurements were utilised. The measurements were made indoors and outdoors in 27 dwellings; 15 Near Road (<50 m from a major road) and 12 Far Road (>300 m from a major road). Dwellings were sampled for one week each in Winter/Spring 2008 and Summer/Autumn 2009, over an eight month period. Analysis of 7-day measurements showed that NO 2 and toluene were elevated at the 5% significance level both indoors and outdoors at Near Road Dwellings compared to Far Road Dwellings. Indoor/Outdoor (I/O) ratios of NO 2 and toluene were not significantly different between Near and Far Road dwellings giving no evidence of any anomalous dominant indoor source for NO 2 and toluene in Near Road dwellings. Indoor NO 2 was significantly correlated to gas stovetop and oven use in both Near and Far Road dwellings. In the absence of gas cooking, indoor NO 2 was elevated in Near Road dwellings relative to Far Road dwellings by approximately 4 ppb and this can be attributed to infiltration of outdoor air. I/O ratios for NO 2 were <1 for Near and Far Road dwellings, indicating that outdoor NO 2 , and hence roadway emissions can potentially contribute a significant proportion to the indoor NO 2 concentration. Mean toluene I/O ratios were >2 indicating that indoor sources dominate with minor contribution from outdoors. Hence the relative contribution of roadways to indoor NO 2 is potentially greater than the relative contribution of roadways to indoor toluene. Findings elsewhere suggest that a similar outdoor enhancement of traffic related NO 2 (∼5 ppb) increases risk of lung cancer and childhood asthma ( Brauer et al., 2000 , Nyberg et al., 2000 ). A simple conceptual model indicated spatial and temporal variance in the concentrations was the biggest limitation in detecting roadway influence outside Near Road dwellings for PM 10 , PM 2.5 and NO 2 while measurement uncertainty was also important for CO. ► Elevated indoor NO 2 and toluene at Near Road dwellings attributed to road emissions. ► Road emissions contribute a significant proportion to indoor NO 2 concentrations. ► Road emissions contribute a minor proportion to the indoor toluene concentrations. ► Elevated NO 2 in Near Road dwellings likely to result in adverse health effects. ► Conceptual model explores spatial, temporal variance in background concentrations.

Woodsmoke Source Apportionment, Home Infiltration, and High Efficiency Particle Air Filter Intervention Assessment in the Rural Annapolis Valley, Nova Scotia, Canada

S-01A7-1 Background/Aims: Woodsmoke has recently received increasing attention as an important source of particulate matter, particularly in rural areas. Indoor woodstoves and outdoor wood boilers are widely used in the Annapolis Valley, in rural Nova Scotia, and the area's topography is conducive to trapping emissions especially during thermal inversions. In an effort to quantify the impact of these factors on local air quality, the source contribution of residential wood burning to ambient particulate matter (PM2.5) at 1 fixed site in the Annapolis Valley, was determined during the winters of 2008/2009 and 2009/2010. Methods: PM2.5 filter specimens and associated gases (Volatile organic compound, NOx, O3) were collected over 50 winter days in 2008/2009 and 90 winter days in 2009/2010. PM2.5 chemical species analyzed from these filters included levoglucosan (and other woodsmoke markers), elements, ions, C14, organic and elemental carbon. Running concurrently with the PM2.5 ambient monitoring in 2009/2010 was an investigation of woodsmoke home infiltration into 30 homes, together with an evaluation of the effectiveness of high efficiency particle air cleaners at reducing indoor PM2.5 concentrations. Results: Chemical Mass Balance (US Environmental Protection Agency [USEPA] CMB v8.2) modeling conducted to date has yielded an average woodsmoke source contribution to PM2.5 of 56.2% (range, 32.6%–73%), versus 12.4% NH4NO3 (range, 5.0%–20%), 24.1% SO4 (range, 11.0%–47%), 9.2% (NH4)2SO4 (range, 2%–19.8%), 3.9% unknown mass (range, 0.6%–14%), and no statistically significant input from vehicle emissions. The mean, minimum, and maximum levoglucosan observed to date are 234.2, 154.9, and 274.3 ng/m3, respectively. Conclusion: The PM2.5 CMB from 2009/2010 will be reviewed together with the PM2.5 CMB conducted in 2008/2009 to better understand the ambient woodsmoke source apportionment in this rural environment. Censoring algorithms, multiple linear regression, and recursive mass balance models will be applied to the indoor/outdoor continuous PM2.5 data to determine the effectiveness of the high efficiency particle air filters.

Acute effects of fine particulate air pollution on ST segment height: A longitudinal study

BackgroundThe mechanisms for the relationship between particulate air pollution and cardiac disease are not fully understood. Air pollution-induced myocardial ischemia is one of the potentially important mechanisms.MethodsWe investigate the acute effects and the time course of fine particulate pollution (PM2.5) on myocardium ischemic injury as assessed by ST-segment height in a community-based sample of 106 healthy non-smokers. Twenty-four hour beat-to-beat electrocardiogram (ECG) data were obtained using a high resolution 12-lead Holter ECG system. After visually identifying and removing all the artifacts and arrhythmic beats, we calculated beat-to-beat ST-height from ten leads (inferior leads II, III, and aVF; anterior leads V3 and V4; septal leads V1 and V2; lateral leads I, V5, and V6,). Individual-level 24-hour real-time PM2.5 concentration was obtained by a continuous personal PM2.5 monitor. We then calculated, on a 30-minute basis, the corresponding time-of-the-day specific average exposure to PM2.5 for each participant. Distributed lag models under a linear mixed-effects models framework were used to assess the regression coefficients between 30-minute PM2.5 and ST-height measures from each lead; i.e., one lag indicates a 30-minute separation between the exposure and outcome.ResultsThe mean (SD) age was 56 (7.6) years, with 41% male and 74% white. The mean (SD) PM2.5 exposure was 14 (22) μg/m3. All inferior leads (II, III, and aVF) and two out of three lateral leads (I and V6), showed a significant association between higher PM2.5 levels and higher ST-height. Most of the adverse effects occurred within two hours after PM2.5 exposure. The multivariable adjusted regression coefficients β (95% CI) of the cumulative effect due to a 10 μg/m3 increase in Lag 0-4 PM2.5 on ST-I, II, III, aVF and ST-V6 were 0.29 (0.01-0.56) μV, 0.79 (0.20-1.39) μV, 0.52 (0.01-1.05) μV, 0.65 (0.11-1.19) μV, and 0.58 (0.07-1.09) μV, respectively, with all p < 0.05.ConclusionsIncreased PM2.5 concentration is associated with immediate increase in ST-segment height in inferior and lateral leads, generally within two hours. Such an acute effect of PM2.5 may contribute to increased potential for regional myocardial ischemic injury among healthy individuals.

Using Si depletion in aerosol to identify the sources of crustal dust in two Chinese megacities

Depletion of Si in transported dust has been recognized for many years. It can be used to distinguish between transported and local dust in cities, although it rarely has been. Here we use the variations of the Si/Al ratio in 15 months of continuous PM 2.5 samples at Beijing (northern China) and Chongqing (southwestern China) to reveal the seasonal patterns of their dust sources. For both cities, peaks of concentration for Si and Al in PM 2.5 corresponded with minima of Si/Al, and could often be linked to pulsed air flow from deserts to the northwest. With significant depletion (up to 80%) and homogeneous distribution at urban and rural sites, Si/Al showed a clear seasonal evolution, which decreased from spring to summer, increased from fall to winter, and collapsed during Chinese Spring Festival, indicating the dominance of transported dust, local fugitive dust and firework influence, respectively. The low ratios implied that desert dust is a common source during spring at Chongqing, whereas its presence during cold season at Beijing was also more frequent than expected. Failing to recognize the depletion of Si may lead to an overestimate of desert dust by 15%–65% when using the average abundance of Al in crust (6%–8%), as in previous studies. The difference in Si/Al ratio between local and transported dust implies that >60% of the dust at Beijing came from outside the city during the springs of 2004–2006. This result can help resolve the contradictory findings on this topic that have been presented earlier.

Measurement of real time black carbon for investigating spot loading effects of Aethalometer data

Measurements of real-time continuous PM 2.5 black carbon (BC) concentrations were made using a single-wavelength Aethalometer (@880 nm) in three different environments, i.e., an indoor office, a residential indoor living room and an urban site, to evaluate the difference in temporal behaviors of BC particles and investigate the optical shadowing effect in the Aethalometer BC data. An empirical method was used for correcting the optical saturation effect on the original BC data obtained from the measurements at the three sites. Also, the elemental carbon (EC) concentrations from 24-h filter-based measurements of PM 2.5 particles were determined using a thermal optical transmittance (TOT) method at the same urban site for comparison with the Aethalometer BC results. Transient events of BC were often observed for period of a few hours at all sites, reaching a maximum level of 27.3 μg m −3 at the urban site. The diurnal cycles of the BC concentrations observed at the two indoor environments were found to be considerably affected by the air exchange rate, occupants' behavior patterns and nearby traffic emissions. The time-series plots of the Aethalometer data showed obvious discontinuities at the filter spot change, and a rise in the apparent BC concentrations after filter tape advances. Also, the relationship between the attenuation and BC concentration was found to be non-linear at all sites. The empirical approach presented here demonstrated a definite improvement in the continuity of the BC data across the time gaps of each tape advance. The compensated BC concentration was 1.10–1.23 times greater than the raw BC data, depending on the observation sites, with the highest difference observed between the raw and compensated BC data at an indoor office near a small traffic road. The 24-h integrated EC concentration was approximately 12% higher than the original 24-h average BC concentration and 6% lower than the loading compensated BC concentration, showing that the loading compensation process accounted for the saturation effect of the filter tape.

Effect of Gas and Kerosene Space Heaters on Indoor Air Quality: A Study in Homes of Santiago, Chile

The impact of outdoor and indoor pollution sources on indoor air quality in Santiago, Chile was investigated. Toward this end, 16 homes were sampled in four sessions. Each session included an outdoor site and four homes using different unvented space heaters (electric or central heating, compressed natural gas, liquefied petroleum gas, and kerosene). Average outdoor fine particulate matter (PM2.5) concentrations were very high (55.9 μg·m-3), and a large fraction of these particles penetrated indoors. PM2.5 and several PM2.5 components (including sulfate, elemental carbon, organic carbon, metals, and polycyclic aromatic hydrocarbons) were elevated in homes using kerosene heaters. Nitrogen dioxide (NO2) and ultrafine particles (UFPs) were higher in homes with combustion heaters as compared with those with electric heaters or central heating. A regression model was used to assess the effect of heater use on continuous indoor PM2.5 concentrations when windows were closed. The model found an impact only for kerosene heaters (45.8 μg m-3).

Predicting airborne particle levels aboard Washington State school buses

School buses contribute substantially to childhood air pollution exposures yet they are rarely quantified in epidemiology studies. This paper characterizes fine particulate matter (PM 2.5) aboard school buses as part of a larger study examining the respiratory health impacts of emission reducing retrofits. To assess onboard concentrations, continuous PM 2.5 data were collected during 85 trips aboard 43 school buses during normal driving routines, and aboard hybrid lead vehicles traveling in front of the monitored buses during 46 trips. Ordinary and partial least squares regression models for PM 2.5 onboard buses were created with and without control for roadway concentrations, which were also modeled. Predictors examined included ambient PM 2.5 levels, ambient weather, and bus and route characteristics. Average concentrations aboard school buses (21 μg m −3) were four and two-times higher than ambient and roadway levels, respectively. Differences in PM 2.5 levels between the buses and lead vehicles indicated an average of 7 μg m −3 originating from the bus's own emission sources. While roadway concentrations were dominated by ambient PM 2.5, bus concentrations were influenced by bus age, diesel oxidative catalysts, and roadway concentrations. Cross-validation confirmed the roadway models but the bus models were less robust. These results confirm that children are exposed to air pollution from the bus and other roadway traffic while riding school buses. In-cabin air pollution is higher than roadway concentrations and is likely influenced by bus characteristics.

Characterizing air pollution in two low-income neighborhoods in Accra, Ghana

Sub-Saharan Africa has the highest rate of urban population growth in the world, with a large number of urban residents living in low-income “slum” neighborhoods. We conducted a study for an initial assessment of the levels and spatial and/or temporal patterns of multiple pollutants in the ambient air in two low-income neighborhoods in Accra, Ghana. Over a 3-week period we measured (i) 24-hour integrated PM 10 and PM 2.5 mass at four roof-top fixed sites, also used for particle speciation; (ii) continuous PM 10 and PM 2.5 at one fixed site; and (iii) 96-hour integrated concentration of sulfur dioxide (SO 2) and nitrogen dioxide (NO 2) at 30 fixed sites. We also conducted seven consecutive days of mobile monitoring of PM 10 and PM 2.5 mass and submicron particle count. PM 10 ranged from 57.9 to 93.6 μg/m 3 at the four sites, with a weighted average of 71.8 μg/m 3 and PM 2.5 from 22.3 to 40.2 μg/m 3, with an average of 27.4 μg/m 3. PM 2.5/PM 10 ratio at the four fixed sites ranged from 0.33 to 0.43. Elemental carbon (EC) was 10–11% of PM 2.5 mass at all four measurement sites; organic matter (OM) formed slightly less than 50% of PM 2.5 mass. Cl, K, and S had the largest elemental contributions to PM 2.5 mass, and Cl, Si, Ca, Fe, and Al to coarse particles. SO 2 and NO 2 concentrations were almost universally lower than the US-EPA National Ambient Air Quality Standards (NAAQS), with virtually no variation across sites. There is evidence for the contributions from biomass and traffic sources, and from geological and marine non-combustion sources to particle pollution. The implications of the results for future urban air pollution monitoring and measurement in developing countries are discussed.

Nonlinear Regression Adjustments of Multiple Continuous Monitoring Methods Produce Effective Characterization of Short-Term Fine Particulate Matter

This study comprehensively characterizes hourly fine particulate matter (PM2.5) concentrations measured via a tapered element oscillating microbalance (TEOM), β-gauge, and nephelometer from four different monitoring sites in U.S. Environment Protection Agency (EPA) Region 5 (in U.S. states Illinois, Michigan, and Wisconsin) and compares them to the Federal Reference Method (FRM). Hourly characterization uses time series and autocorrelation. Hourly data are compared with FRM by averaging across 24-hr sampling periods and modeling against respective daily FRM concentrations. Modeling uses traditional two-variable linear least-squares regression as well as innovative nonlinear regression involving additional meteorological variables such as temperature and humidity. The TEOM shows a relationship with season and temperature, linear correlation as low as 0.7924 and nonlinear model correlation as high as 0.9370 when modeled with temperature. The β-gauge shows no relationship with season or meteorological variables. It exhibits a linear correlation as low as 0.8505 with the FRM and a nonlinear model correlation as high as 0.9339 when modeled with humidity. The nephelometer shows no relationship with season or temperature but a strong relationship with humidity is observed. A linear correlation as low as 0.3050 and a nonlinear model correlation as high as 0.9508 is observed when modeled with humidity. Nonlinear models have higher correlation than linear models applied to the same dataset. This correlation difference is not always substantial, which may introduce a tradeoff between simplicity of model and degree of statistical association. This project shows that continuous monitor technology produces valid PM2.5 characterization, with at least partial accounting for variations in concentration from gravimetric reference monitors once appropriate nonlinear adjustments are applied. Although only one regression technically meets new EPA National Ambient Air Quality Standards (NAAQS) Federal Equivalent Method (FEM) correlation coefficient criteria, several others are extremely close, showing optimistic potential for use of this nonlinear adjustment model in garnering EPA NAAQS FEM approval for continuous PM2.5 sampling methods.