Ultrafine Particle Counter Research Articles

Hourly variation in fine particle exposure is associated with transiently increased risk of ST segment depression

Objectives: To evaluate whether hourly changes in fine particle (PM2.5, diameter<2.5 µm) exposure or outdoor particle concentrations are associated with rapid ischaemic responses. Methods: 41 non-smoking elderly people with coronary...

Determinants of ultrafine particle exposures in transportation environments: findings of an 8-month survey conducted in Montréal, Canada

An 8-month sampling campaign was conducted in Montréal, Canada to explore determinants of ultrafine particle (UFP) exposures in transportation environments and to develop models to predict such exposures. Between April and November 2006, UFP (0.02-1 mum) count exposure data were collected for one researcher during 80 morning and evening commutes including a 0.5-km walk, a 3-km bus ride, and a 26-km automobile ride in each direction. Ambient temperature, relative humidity, precipitation, and wind speed/direction data were collected for each transit period and the positions of bus and automobile windows were recorded. Mixing heights were also estimated. Morning UFP exposures were significantly greater than those in the evening, with the highest levels observed in the automobile and the lowest while walking. Wind speed and mixing height were highly correlated, and as a result only wind speed was considered in multivariable models owing to the accessibility of quantitative hourly monitoring data. In these models, each 10 degrees C increase in morning temperature was associated with decreases of 14,560/cm(3) (95% CI=11,111 to 18,020), 8160/cm(3) (95% CI=5060 to 11,260), and 11,310/cm(3) (95% CI=6820 to 15,810) for UFP exposures in walk, bus, and automobile environments, respectively. Likewise, each 10-km/h increase in morning wind speed corresponded to decreases of 8252/cm(3) (95% CI=5130 to 11,360), 6210/cm(3) (95% CI=3420 to 9000), and 6350/cm(3) (95% CI=2440 to 10,260) for UFP exposures in walk, bus, and automobile environments, respectively. Similar trends were observed in the evening hours. In an evaluation of model performance, moderate correlations were observed between measured and predicted UFP exposures on new bus (r=0.65) and automobile (r=0.77) routes. Further research is required to incorporate variables such as traffic density and vehicle ventilation settings into the models presented.

Characterizing and predicting ultrafine particle counts in Canadian classrooms during the winter months: Model development and evaluation

School classrooms are potentially important micro-environments for childhood exposures owing to the large amount of time children spend in these locations. While a number of airborne contaminants may be present in schools, to date few studies have examined ultrafine particle (0.02–1 μm) (UFP) levels in classrooms. In this study, our objective was to characterize UFP counts (cm −3) in classrooms during the winter months and to develop a model to predict such exposures based on ambient weather conditions and outdoor UFPs, as well as classroom characteristics such as size, temperature, relative humidity, and carbon dioxide levels. In total, UFP count data were collected on 60 occasions in 37 occupied classrooms at one elementary school and one secondary school in Pembroke, Ontario. On average, outdoor UFP levels exceeded indoor measures by 8989 cm −3 (95% confidence interval (CI): 6382, 11 596), and classroom UFP counts were similar at both schools with a combined average of 5017 cm −3 (95% CI: 4300, 5734). Of the variables examined only wind speed and outdoor UFPs were important determinants of classrooms UFP levels. Specifically, each 10 km/h increase in wind speed corresponded to an 1873 cm −3 (95% CI: 825, 2920) decrease in classroom UFP counts, and each 10 000 cm −3 increase in outdoor UFPs corresponded to a 1550 cm −3 (95% CI: 930, 2171) increase in classroom UFP levels. However, high correlations between these two predictors meant that the independent effects of wind speed and outdoor UFPs could not be separated in multivariable models, and only outdoor UFP counts were included in the final predictive model. To evaluate model performance, classroom UFP counts were collected for 8 days at two new schools and compared to predicted values based on outdoor UFP measures. A moderate correlation was observed between measured and predicted classroom UFP counts ( r=0.63) for both schools combined, but this relationship was not valid on days in which a strong indoor UFP source (electric kitchen stove) was active in schools. In general, our findings suggest that reasonable estimates of classroom UFP counts may be obtained from outdoor UFP data but that the accuracy of such estimates are limited in the presence of indoor UFP sources.

Factors influencing the spatial extent of mobile source air pollution impacts: a meta-analysis

BackgroundThere has been growing interest among exposure assessors, epidemiologists, and policymakers in the concept of "hot spots", or more broadly, the "spatial extent" of impacts from traffic-related air pollutants. This review attempts to quantitatively synthesize findings about the spatial extent under various circumstances.MethodsWe include both the peer-reviewed literature and government reports, and focus on four significant air pollutants: carbon monoxide, benzene, nitrogen oxides, and particulate matter (including both ultrafine particle counts and fine particle mass). From the identified studies, we extracted information about significant factors that would be hypothesized to influence the spatial extent within the study, such as the study type (e.g., monitoring, air dispersion modeling, GIS-based epidemiological studies), focus on concentrations or health risks, pollutant under study, background concentration, emission rate, and meteorological factors, as well as the study's implicit or explicit definition of spatial extent. We supplement this meta-analysis with results from some illustrative atmospheric dispersion modeling.ResultsWe found that pollutant characteristics and background concentrations best explained variability in previously published spatial extent estimates, with a modifying influence of local meteorology, once some extreme values based on health risk estimates were removed from the analysis. As hypothesized, inert pollutants with high background concentrations had the largest spatial extent (often demonstrating no significant gradient), and pollutants formed in near-source chemical reactions (e.g., nitrogen dioxide) had a larger spatial extent than pollutants depleted in near-source chemical reactions or removed through coagulation processes (e.g., nitrogen oxide and ultrafine particles). Our illustrative dispersion model illustrated the complex interplay of spatial extent definitions, emission rates, background concentrations, and meteorological conditions on spatial extent estimates even for non-reactive pollutants. Our findings indicate that, provided that a health risk threshold is not imposed, the spatial extent of impact for mobile sources reviewed in this study is on the order of 100–400 m for elemental carbon or particulate matter mass concentration (excluding background concentration), 200–500 m for nitrogen dioxide and 100–300 m for ultrafine particle counts.ConclusionFirst, to allow for meaningful comparisons across studies, it is important to state the definition of spatial extent explicitly, including the comparison method, threshold values, and whether background concentration is included. Second, the observation that the spatial extent is generally within a few hundred meters for highway or city roads demonstrates the need for high resolution modeling near the source. Finally, our findings emphasize that policymakers should be able to develop reasonable estimates of the "zone of influence" of mobile sources, provided that they can clarify the pollutant of concern, the general site characteristics, and the underlying definition of spatial extent that they wish to utilize.

超微小粒子測定装置 (UFPC) を用いた道路近傍および建物屋内外におけるPM2.5ならびに超微小粒子の粒径別数濃度測定

超微小粒子測定装置 (UFPC) を用いた道路近傍および建物屋内外におけるPM2.5ならびに超微小粒子の粒径別数濃度測定

Childrenʼs Exposure to Diesel Exhaust at a Rural Elementary School

SAB5-O-04 Diesel exhaust has been associated with health effects in humans, including respiratory illness and cancer. Children are of particular concern regarding diesel exposure from schools buses because their lungs are still developing and they can be more susceptible to health effects than adults. In this study, a direct exposure assessment was conducted at the elementary school in Potsdam, NY in late October 2005 for 5 days and early February 2006 for 4 days. Sampling was performed for 2 hours in the morning and 2 hours in the afternoon corresponding with the school bus dropoff and pickup times. Matched indoor/outdoor semi-continuous instruments were used to measure ultrafine particle (UFP) counts, particle-bound PAHs, and particle size distribution. One indoor and several outdoor integrated filter samplers collected PM2.5 mass on both quartz and Teflon filters. The filter samples were analyzed for mass and organic and elemental carbon (OC/EC). The highest PM2.5 concentrations were found indoors and the outdoor concentrations in the bus pickup and dropoff area were found to be slightly higher than those from the upwind site. All outdoor PM2.5 concentrations were below 12 μg/m3. The elemental carbon measurements were found to be below the detection limit during the fall field intensive, which is likely due to the fact that the buses shut off immediately upon arrival at the school, reducing the source strength, and the sampling period was short. The sampling period was increased from 4 hours to 8 hours for the winter field intensive. Time-series data from the semi-continuous instruments showed clear increases in UFP number concentration to more than 100,000 particles/cm3 during the times that the buses arrived and departed from the school compared with less than 10,000 particles/cm3 before the buses arrived. A strong correlation between the indoor air and the outdoor particle concentrations was found, and the penetration of the outdoor particles indoors was found to be almost 100%. The results of this study illustrate that the bus pickup and dropoff next to the elementary school results in a short-term, high concentration exposures to UFP both outside and inside the school.

Runs of Ventricular and Supraventricular Tachycardia Triggered by Air Pollution in Patients with Coronary Heart Disease

The authors conducted an investigation of the association between air pollution and arrhythmia. A prospective panel study (October 2000-April 2001) was conducted in Erfurt, Germany. Fifty-seven men with coronary heart disease were subjected to six 24-hour electrocardiogram recordings. Runs of supraventricular and ventricular tachycardia were associated with continuous ultrafine particle counts (UFP), accumulation mode particle counts (ACP), PM2.5, and gaseous pollutants. Poisson and linear regression models were applied adjusting for trend, weekday, and meteorologic data. Elevated concentrations of UFP, ACP, PM2.5, and nitrogen dioxide increased the risk for supraventricular runs and the number of ventricular runs at almost all lags. Statistically significant associations were found predominantly in the previous 24 to 71 hours and with the 5-day moving average. Elevated concentrations of fine and ultrafine particle increased the risk of arrhythmia in men with coronary heart disease.

Field Comparison of P-Trak and Condensation Particle Counters

The P-trak ultrafine particle counter is a portable version of a condensation particle counter (CPC). Both instruments detect particle number concentrations in real time but have different detection limits. The P-trak has been widely used for indoor air quality evaluation and aerosol research. However, there is very limited information about the reliability and precision of this instrument and its comparability with other similar instruments. The purpose of this study was to compare a P-trak ultrafine particle counter with a standard CPC and evaluate its applicability to ambient air monitoring. This study was carried out near the Interstate 405 freeway (I-405) in Los Angeles. Measurements were made at increasing distances from the freeway on both sides at night as well as inside and outside of two 2-bedroom apartments located near the freeway. A CPC and a Scanning Mobility Particle Sizer (SMPS) were collocated with two P-traks and measurement results compared. In general, higher correlations were observed...

Exposure visualisation of ultrafine particle counts in a transport microenvironment

An increasing number of studies indicate that short-term peak exposures, such as those seen in the transport microenvironment, pose particular health threats. Short-term exposure can only be sufficiently characterised using portable, fast-response monitoring instrumentation with detailed summaries of individual activity. In this paper, we present an exposure visualisation system that addresses this issue—it allows the simultaneous presentation of mobile video imagery synchronised with measured real-time ultrafine particle count exposure of an individual. The combined data can be examined in detail for the contribution of the surrounding environment and the individual's activities to their peak and overall exposure. The exposure visualisation system is demonstrated and evaluated around the DAPPLE study site in Central London using different modes of transport (walking, cycling, bus, car and taxi). The video images, synchronised with the exposure profile, highlight the extent to which ultrafine particle exposure is associated with traffic density and proximity to pollutant source. The extremely rapid decline in concentration with increasing distance away from the pollutant source, such as from the main street to the backstreets, is clearly evident. The visualisation technique allows these data to be presented to both technical audiences and laypersons thus making it an effective environmental risk communication tool. Some exposure peaks however are not obviously associated with any event recorded on video—in these cases it will be necessary to use advanced dispersion modelling techniques to investigate meteorological conditions and other variables influencing in-street conditions to identify their possible causes.

Associations Between Submicrometer Particles Exposures and Blood Pressure and Heart Rate in Patients With Lung Function Impairments

The objective of this study was to evaluate whether submicrometer particle is associated with elevated blood pressure (BP) and heart rate (HR). We measured ambulatory systolic BP (SBP), diastolic BP (DBP), and HR using a portable BP monitoring system and number concentrations of submicrometer particle with a size range of 0.02 to 1 microm (NC0.02-1) by a P-TRAK Ultrafine Particle Counter for 10 patients with lung function impairments. We found NC0.02-1 exposures at 1- to 3-hour moving averages were associated with the elevation of SBP, DBP, and HR. There were 1.4 to 3.4-mm-Hg increases in SBP, 1.4 to 2.2-mm-Hg increases in DBP, and 0.3 to 3.5-beats/min increases in HR for 10,000 particles/cm increases in NC0.02-1 at 1- to 3-hour moving averages. Exposures to submicrometer particles were associated with short-term increases in BP and HR in patients with lung function impairments.

Pedestrian exposure to air pollution along a major road in Central London, UK

Pedestrian exposure to PM 2.5, the loss of reflectance (‘blackness’) of the PM 2.5 filters, ultrafine particle counts (particle range: 0.02–1 μm) and carbon monoxide (CO) was investigated along a major road running through the DAPPLE study site in Central London, UK. During an intensive 12-day exposure measurement campaign, groups of four volunteers sampled twice in the morning and twice in the afternoon along Marylebone Road. They were randomly designated a walking direction, walking position (kerbside or buildingside) and a side of the major road to walk along. PM 2.5 was sampled using high-flow gravimetric personal samplers, ultrafine particle counts were measured using TSI P-TRAKs and Langans were used to measure CO exposure. PM 2.5 samples were analysed gravimetrically and reflectance was measured using a smoke stain reflectometer to obtain a measure of ‘black smoke’. In total 603 acceptable samples were obtained—155 PM 2.5 and reflectance, 120 ultrafine particle count and 173 CO. The average pedestrian exposure along the road was 37.7 μg/m 3, 12.1 m −1×10 −5, 80 009 pt/cm 3 and 1.3 ppm for PM 2.5, loss of reflectance, ultrafine particle counts and CO, respectively. PM 2.5 exposure in the morning was significantly higher than in the afternoon, and there was a significant difference in exposure on the different sides of the road. For both reflectance and ultrafine particle counts, the exposure was significantly different both between the two walking positions on the pavement and the two sides of the street canyon. However there was no significant difference in CO exposure based on walking position, walking direction, canyon side or timing. Filter reflectance was significantly but weakly correlated with PM 2.5 exposure ( r = 0.3 , N = 155 ), CO exposure ( r = 0.2 , N = 154 ) and ultrafine particle count exposure ( r = 0.7 , N = 108 ). PM 2.5 and CO personal exposure measurements were much higher than those recorded at both the local background fixed monitoring station (FMS) and a kerbside FMS, but PM 2.5 personal exposure was significantly correlated with the PM 2.5 concentrations at the background FMS ( r = 0.6 , N = 155 ).

A Sampling Approach for Evaluating Particle Loss During Continuous Field Measurement of Particulate Matter

AbstractA method for evaluating sample bias in field measurements is presented. Experiments were performed in the field and laboratory to quantify the bias as a function of particle size for the scanning mobility particle sizer and the aerodynamic particle sizer. Sources of bias and sample loss considered in this work were sampling line loss, instrumental differences and inlet efficiencies. Measurement of the bias and sample loss allow for correction of the data acquired in the field, so as to obtain more representative samples of atmospheric concentrations. Substantial losses of fine and ultrafine particle count were observed, with sampling line losses ranging from 10–50 %, dependent on particle size. Only minor line losses were observed for coarse particles (approximately 5 %) because the sampling line was oriented vertically.Please note: corrected DOI, in print wrong DOI (10.1002/ppsc.200400939)

Personal exposure of street canyon intersection users to PM2.5, ultrafine particle counts and carbon monoxide in Central London, UK

Abstract Short-term human exposure to PM 2.5, ultrafine particle counts (particle range: 0.02–1 μm) and carbon monoxide (CO) was investigated at and around a street canyon intersection in Central London, UK. During a four-week field campaign, groups of four volunteers collected samples at three timings (morning, lunch and afternoon), along two different routes (a heavily trafficked route and a backstreet route) via five modes of transport (walking, cycling, bus, car and taxi). PM 2.5 was sampled using high-flow gravimetric personal samplers, ultrafine particle counts were measured using TSI P-TRAKs and Langans were used to measure CO exposure. Three hundred and ninety-four samples were collected—197 PM 2.5 , 86 ultrafine particle count and 111 CO. Arithmetic means of PM 2.5 personal exposure were 27.5, 33.5, 34.5, 38.0 and 41.5 μg m −3 , ultrafine particle counts were 67 773, 93 968, 101 364, 99 736 and 87 545 pt cm −3 and CO levels were 0.9, 1.1, 0.8, 1.3 and 1.1 ppm for walking, cycling, bus, car and taxi respectively. On the heavily trafficked route, personal exposure was 35.3 μg m −3 , 101142 pt cm −3 and 1.3 ppm, and on the backstreet route it was 31.8 μg m −3 , 71628 pt cm −3 and 0.6 ppm for PM 2.5 , ultrafine particle counts and CO, respectively. Personal exposure levels were high during the morning measurements for all three pollutants (34.6 μg m −3 , 106 270 pt cm −3 and 1.5 ppm for PM 2.5 , ultrafine particle counts and CO, respectively).There was a moderately strong correlation between personal exposure of ultrafine particle counts and CO ( r = 0.7 , N = 67 ) but a weaker correlation between PM 2.5 and ultrafine particle counts ( r = 0.5 , N = 83 ) and a low correlation between PM 2.5 and CO exposure ( r = 0.2 , N = 105 ). The exposure assessment also revealed that the background and kerbside monitoring stations were not representative of the personal exposure of individuals to PM 2.5 and CO at and around a street canyon intersection.

ASSOCIATIONS BETWEEN TRAFFIC-RELATED PM2.5 CONCENTRATIONS AND EXHALED NITRIC OXIDE IN A PANEL OF OLDER ADULTS

ISEE-130 Introduction: Previous studies have shown that collection of nitric oxide (NO) samples from expired air may represent a noninvasive measure of lower airway inflammation. To investigate the potential impacts of traffic-related particles on sub-clinical lung inflammation, we examined the associations between particulate exposures and the fraction of exhaled nitric oxide (FENO) in a panel of senior citizens exposed to elevated levels of traffic-related pollutants during a series of bus trips. Methods: Breath samples of FENO were collected from 44 non-smoking subjects 18-hours after participation in a field trip. Each field trip involved two one-hour trips aboard a diesel bus and approximately three hours for lunch and an activity such as a movie. Subjects participated in approximately four trips, spaced about once every 3-weeks. Room air samples were also collected at each session to correct for possible sample contamination. All FENO samples were analyzed within 24-hours of collection using chemiluminescence. Particulate exposures were assessed using two mobile carts that followed the subjects throughout each field trip. Exposure measurements included continuous readings of fine particle mass (PM2.5), ultra-fine, fine, and coarse particle counts, and black carbon. Carbon monoxide and nitric oxide concentrations were also measured continuously during the bus rides. Ambient concentrations of gases, particle mass and number, and meteorological parameters were available from a local USEPA Supersite. Results: Longitudinal analyses indicated that an inter-quartile increase (8.7 μg/m3) in the average concentration of PM2.5 during the previous day’s field trip was associated with an increased FENO of 1.5 ppb (95% CI: 0.54 - 2.5 ppb) after controlling for subject, time trend, day of week, hour of day, room NO levels, and apparent temperature. An inter-quartile increase (72 pt/cc) in a component of fine particle counts also produced a statistically significant increase in FENO (1.3 ppb, 95% CI: 0.25 - 2.4 ppb). Other particulate measures were generally associated with increases in FENO of the same magnitude, although none met statistical significance. On average, the changes observed in this study represent an approximate 10% change in the mean FENO of the cohort. Discussion: These results suggest that exposures to traffic-related air pollution may lead to airway inflammation as measured by FENO. These sub-clinical inflammatory changes may represent an important mechanistic step in the pathogenesis of cardiopulmonary effects induced by air pollution. These findings may also have important public health significance to commuters as the exposures in this study represent typical highway driving and time spent in indoor metropolitan locations.

AIR POLLUTION AND INFLAMMATORY MARKERS IN BLOOD

ISEE-22 Introduction: The adverse cardiovascular health effects of air pollution may be caused in part by systemic inflammation triggered by oxidative stress to the lungs. Recent studies have suggested that these associations may be strongest for traffic-related particles. In order to examine the associations between traffic-related particles and systemic inflammation, we conducted a study in which a panel of senior citizens was exposed to elevated traffic-related pollutant exposures through a series of bus trips. Methods: Repeated blood samples were collected from forty-four non-smoking participants living at one of four suburban independent senior living facilities. Blood samples were obtained between April and June of 2002, approximately 18-hours after study subjects participated in a field trip that included two hours aboard a diesel bus. Each subject participated in approximately four field trips, about once every 3-weeks. Blood samples were analyzed for red and white cell parameters using a CBC with differential analyses. Samples were also tested for interleukin-6, c-reactive protein, intracellular adhesion molecule–1, fibrinogen, and von willebrand’s factor. Particulate exposures of the participants were assessed using two mobile carts that followed the subjects throughout each field trip. Micro-environmental exposure measurements included continuous readings of fine particle mass (PM2.5), ultra-fine, fine, and coarse particle counts, and black carbon. Carbon monoxide and nitric oxide concentrations were also measured continuously during the bus rides. These exposure measures were supplemented with ambient air concentrations of gases, particle mass and number, and meteorological parameters measured at a local USEPA-funded Supersite. Results: Among the 138 blood samples analyzed, levels of circulating inflammatory markers were found to be comparable to the values reported by previous studies. Evaluation of the air monitoring data indicates that the bus trips successfully elevated hourly exposures above levels observed at the residence facilities and central site. The mean hourly black carbon concentration during the bus trip periods was 3,400 (SD: 1,200) ng/m3 as compared to mean hourly concentrations of 350 (SD: 450) ng/m3 during facility periods and 750 (SD: 370) ng/m3 at the Supersite during times concurrent with the bus trip. Measures of PM2.5 and particle counts were also substantially elevated during periods when subjects were aboard the bus. The impacts of these micro-environmental changes on circulating inflammatory markers will be presented using the results of longitudinal mixed models.

Observations of new particle formation in urban air

Measurements are reported of particle number concentration at two urban sites within Birmingham, UK. The measurements were made with a condensation particle counter (TSI Model 3022A) and an ultrafine particle counter (TSI Model 3025) operated in tandem. Other colocated measurements included particle surface area by epiphaniometer, sulfur dioxide, oxides of nitrogen and ozone, solar radiation or JO1D, and in some campaigns, particle number size distribution by Scanning Mobility Particle Sizer. Events were identified when substantial excursions in particle number count were accompanied by a divergence between the two particle counters indicating a large number of particles in the 3–7 nm diameter range. Criteria have been developed to distinguish between particles within this size range arising from homogeneous nucleation within the atmosphere and from emissions from point sources. Out of a total of 232 days sampling distributed throughout the year, events on only 8 days could be attributed fairly unequivocally to homogeneous nucleation processes, with a further 4 days possibly attributable. Nucleation events occur in winter as well as summer months, but depend, among other things, upon a low particle surface area. Modeling of aerosol dynamical processes for 20 June 1999, indicates that the observations can be explained by a nucleation rate of 6 × 106 cm−3 s−1 at a condensable vapor concentration (as H2SO4) of 6.5 × 107 cm−3. It is inferred that both the nucleation and particle growth processes involve condensable molecules other than, or in addition to, sulfuric acid.

Continuous measurement of fine and ultrafine particulate matter, criteria pollutants and meteorological conditions in urban El Paso, Texas

Continuous measurements of aerosol size distributions were made in El Paso, TX, for a 21 day period in winter 1999. Size distribution measurements were performed at two urban locations in El Paso using two pairs of the scanning mobility particle sizer and the aerodynamic particle sizer. Complementary measurements also were performed for gas phase pollutants (CO, NO, NO 2, O 3) and meteorological conditions. Throughout the study, the mean ultrafine particle (those smaller than 0.1 μm in diameter) number concentration was 14,400 particles cm −3. There was a significant correlation between CO and both ultrafine and accumulation mode (those between 0.1 and 1 μm in diameter) particle count, with the Pearson correlation coefficient ( r) values of 0.81 and 0.87, respectively. The correlation between NO and both ultrafine and accumulation mode particle count is also significant, but not as strong as the correlation of CO and the particle concentrations. Most pollutants were found to vary on diurnal cycles and to follow one of two different trends, either vehicular traffic schedules or sunlight intensity. Wind direction was found to have an influence not only on pollutant concentrations, but also on the correlation between pollutants. With southerly winds, CO, NO and NO 2 concentrations were 25–140% greater than when the wind was coming from the north. Likewise, ultrafine and accumulation mode particle concentrations were approximately 100% greater for southerly than for northerly winds.

Concentration gradient patterns of aerosol particles near interstate highways in the Greater Cincinnati airshed.

The objective of this study was to determine if there is an exposure gradient in particulate matter concentrations for people living near interstate highways, and to determine how far from the highway the gradient extends. Air samples were collected in a residential area of Greater Cincinnati in the vicinity of two major highways. The measurements were conducted at different distances from the highways by using ultrafine particle counters (measurement range: 0.02-1 microm), optical particle counters (0.3-20 microm), and PM2.5 Harvard Impactors (0.02-2.5 microm). The collected PM2.5 samples were analyzed for mass concentration, for elemental and organic carbon, and for elemental concentrations. The results show that the aerosol concentration gradient was most clearly seen in the particle number concentration measured by the ultrafine particle counters. The concentration of ultrafine particles decreased to half between the sampling points located at 50 m and 150 m downwind from the highway. Additionally, elemental analysis revealed a gradient in sulfur concentrations up to 400 m from the highway in a residential area that does not have major nearby industrial sources. This gradient was qualitatively attributed to the sulfate particle emissions from diesel engine exhausts, and was supported by the concentration data on several key elements indicative of traffic sources (road dust and diesel exhaust). As different particulate components gave different profiles of the diesel exposure gradient, these results indicate that no single element or component of diesel exhaust can be used as a surrogate for diesel exposure, but more comprehensive signature analysis is needed. This characterization is crucial especially when the exposure data are to be used in epidemiological studies.

Ultrafine Particle Deposition in Humans During Rest and Exercise

Ultrafine particles (diameter < 100 nm) may be important in the health effects of air pollution, in part because of their predicted high respiratory deposition. However, there are few measurements of ultrafine particle deposition during spontaneous breathing. The fractional deposition for the total respiratory tract of ultrafine carbon particles (count median diameter = 26 nm, geometric standard deviation = 1.6) was measured in 12 healthy subjects (6 female, 6 male) at rest (minute ventilation 9.0 ± 1.3 L/min) using a mouthpiece exposure system. The mean ± SD fractional deposition was 0.66 ± 0.11 by particle number and 0.58 ± 0.13 by particle mass concentration, similar to model predictions. The number deposition fraction increased as particle size decreased, reaching 0.80 ± 0.09 for the smallest particles (midpoint count median diameter = 8.7 nm). No gender differences were observed. In an additional 7 subjects (2 female, 5 male) alternating rest with moderate exercise (minute ventilation 38.1 ± 9.5 L/min), the deposition fraction during exercise increased to 0.83 ± 0.04 and 0.76 ± 0.06 by particle number and mass concentration, respectively, and reached 0.94 ± 0.02 for the smallest particles. Experimental deposition data exceeded model predictions during exercise. The total number of deposited particles was more than 4.5-fold higher during exercise than at rest because of the combined increase in deposition fraction and minute ventilation. Fractional deposition of ultrafine particles during mouth breathing is high in healthy subjects, and increases further with exercise.

Endotoxin Priming Affects the Lung Response to Ultrafine Particles and Ozone in Young and Old Rats

Epidemiological studies have demonstrated a correlation between low levels of ambient particles and morbidity, particularly in the elderly with existing cardiopulmonary disease. Such correlations have been challenged due to doubts as to whether particles act alone to cause these detrimental effects. We hypothesized that ambient carbonaceous ultrafine particles (part of the urban fine particle mode) and ozone (O3) together would induce greater oxidative stress in the lung than when administered alone and that their effects would be amplified in the compromised, aging lung. We therefore exposed male F344 rats (10 wk, 20 mo) to ultrafine carbon particles (count median diameter 25 nm, 100 μg/m3, equivalent to 50 μg/m3 inhaled by humans) and to O3 (1 ppm) alone and in combination for 6 h. Low-dose endotoxin (lipopolysaccharide, LPS) priming by inhalation (70 endotoxin units estimated alveolar deposited dose) was used as a model of respiratory tract infection. Inflammatory parameters in bronchoalveolar lavage (BAL) fluid and oxidant release from BAL cells were assessed 24 h after exposure. A significant main effect of carbon, O3 and LPS on lung inflammation and a significant interaction between LPS and O3 that resulted in lower inflammation were observed in young rats. In old rats, only LPS and O3 had significant effects, but carbon and O3 interacted and increased lung inflammation above the effect level for either component alone. Oxidant release by BAL cells generally corresponded with the PMN response; however, in young rats, the combination of LPS priming with carbon and O3 exposure decreased oxidant release. In old rats, this combination increased oxidant release. These results are consistent with our hypothesis that urban ultrafine carbonaceous particles are involved in increased morbidity in sensitive populations. In addition, age and coexposure with a high level of O3 can significantly affect both lung inflammation and inflammatory cell activation such that the aged organism will experience increased oxidative stress in the lung. In both age groups, LPS enhanced the effects of particles and O3, thus allowing the observation of effects that would otherwise be masked.