Inhalable airborne particulate pollution in sites characterized by dissimilar environmental conditions

The aim of the present study is to characterise from a physico-chemical point of view the airborne particulate matter (PM10) sampled in different sites dissimilar with regard to the weather conditions, the residential density and the industrial activities. The particles were collected by an eight-stage cascade impactor, Andersen particle fractionating sampler. The analysis of the particle samples was performed by a scanning electron microscopy (SEM) equipped with a thin-window system for X-ray microanalysis by energy dispersion spectrometry. The hierarchical cluster analysis (HCA) on the analytical data revealed the presence of eight different particulate types (particle clusters) in the sampling sites: C-rich particles (cluster 1); Ca and Mg carbonates (cluster 2); Ca sulphates (cluster 3); silica particles (cluster 4); silicates (cluster 5); Fe-rich particles (cluster 6); metal compounds (cluster 7); carbonaceous particles with heavy metals (cluster 8). Data obtained in this study demonstrate a significant correlation between the PM10 composition and the anthropic activities present the sampling site.     

Fine particles are more strongly associated than coarse particles with acute respiratory health effects in schoolchildren

Numerous studies have reported associations between airborne particles and a range of respiratory outcomes from symptoms to mortality. Current attention has been focused on the characteristics of these particles responsible for the adverse health effects. We have reanalyzed three recent longitudinal diary studies to examine the relative contributions of fine and coarse particles on respiratory symptoms and peak expiratory flow in schoolchildren. In the Harvard Six Cities Diary Study, lower respiratory symptoms in a two-pollutant model were associated with an interquartile range increment in fine particles [(for 15 microg/m3 particulate matter (PM) <2.5 microm in aerodynamic diameter (PM2.5), odds ratio = 1.29, 95% confidence limits (CL) = 1.06, 1.57] but not coarse particles (for 8 microg/m3 PM2.5-10, odds ratio = 1.05, 95% CL = 0.90, 1.23). In Uniontown, PA, we found that peak flow was associated with fine particles (for 15 microg/m3 PM2.1, peak flow = -0.91 liters/minute, 95% CL = -0.14, -1.68), especially fine sulfate particles, but not with coarse particles (for 15 microg/m3 PM2.1-10, +1.04 liters/minute, 95% CL = -1.32, +3.40). We found similar results for an equivalent children's cohort in State College, PA. We conclude that fine particles, especially fine sulfate particles, have much stronger acute respiratory effects than coarse particles.     

Air pollution and daily mortality in the Coachella Valley, California: a study of PM10 dominated by coarse particles

Many epidemiological studies provide evidence of an association between airborne particles, measured as PM10 (particulate matter less than 10 microm in diameter), and daily morbidity and mortality. Most of these studies have been conducted in urban areas where PM10 consists primarily of fine particles (<2.5 microm in diameter). Few studies have investigated impacts associated with coarse mode particles (>2.5 microm in diameter). We investigated associations between PM10 and daily mortality in the Coachella Valley, a desert resort and retirement area east of Los Angeles, where coarse particles of geologic origin typically comprise approximately 50-60% of PM10 and can exceed 90% during wind events. Our analysis utilized daily data on mortality from 1989 through 1992 as well as several pollutant and meteorological variables, including PM10, nitrates, sulfates, ozone, nitrogen dioxide, carbon monoxide, temperature, and relative humidity. Outcome variables included several measures of daily mortality, including all-cause, cardiovascular and respiratory mortality, and counts of deaths for those above age 50. Multivariate Poisson regression models were used to explain these health endpoints, controlling for temperature, humidity, day of the week, season, and time, using locally weighted smoothing techniques. The analysis indicated statistically significant associations between PM10 (2- or 3-day lags) and each measure of mortality. The results were robust to various model specifications, correction for autocorrelation and overdispersion, and analysis of influential observations. A 10 microg/m3 change in daily PM10 was associated with an approximately 1% increase in mortality, which is of similar magnitude to particle-associated impacts identified in urban areas. Thus, our findings provide evidence for a mortality effect of PM10 in an area where the particulate mass is dominated by coarse particles.     

Atmospheric pollutants study of particles and metallic elements during high wind speed (wind speed >6 m/s) near Taiwan Strait around central Taiwan

The purpose of this study was to characterize metallic elements associated with atmospheric particulate matter in total suspended particulate (TSP), fine particles (particle matter with an aerodynamic diameter of <2.5 microm, PM2.5) and coarse particles (particle matter with an aerodynamic diameter of 2.5-10 microm, PM2.5-10), at high wind speed (wind speed >6 m/s) at Taichung Harbor (TH) and Wuci traffic (WT) in central Taiwan from March to December 2004. The correlation coefficient (R2) between TSP, coarse, fine particulate concentrations versus wind speed at the TH and WT sampling site during high wind speed (>6 m/s) are shown in this study. In addition, the correlation coefficients between TSP, coarse and fine particles of metallic species versus high wind speed were also observed. The results indicated that the correlation coefficient order was TSP> coarse>fine for particles at both sampling sites during high wind speed (>6 m/s) near central Taiwan. In addition, the concentrations of Fe, Zn, Mn, Cu, Pb, Cr, Mg for TSP, coarse and fine particulates were also analysed in this study.     

Association between exhaled breath condensate nitrate + nitrite levels with ambient coarse particle exposure in subjects with airways disease

Objectives Studies of individual inflammatory responses to exposure to air pollution are few but are important in defining the most sensitive markers in better understanding pathophysiological pathways in the lung. The goal of this study was to assess whether exposure to airborne particles is associated with oxidative stress in an epidemiological setting. Methods The authors assessed exposure to particulate matter air pollution in four European cities in relation to levels of nitrite plus nitrate (NOx) in exhaled breath condensate (EBC) measurements in 133 subjects with asthma or chronic obstructive pulmonary disease using an EBC capture method developed for field use. In each subject, three measurements were collected. Exposure measurements included particles smaller than 10 μm (PM(10)), smaller than 2.5 μm (PM(2.5)) and particle number counts at a central site, outdoors near the subject's home and indoors. Results There were positive and significant relationships between EBC NOx and coarse particles at the central sampling sites (increase of 20.4% (95% CI 6.1% to 36.6%) per 10 μg/m(3) increase of coarse particles of the previous day) but not between EBC NOx and other particle measures. Associations tended to be stronger in subjects not taking steroid medication. Conclusions An association was found between exposure to ambient coarse particles at central sites and EBC NOx, a marker of oxidative stress. The lack of association between PM measures more indicative of personal exposures (particularly indoor exposure) means interpretation should be cautious. However, EBC NOx may prove to be a marker of PM-induced oxidative stress in epidemiological studies.     

Health effects of particles in ambient air

A summary of a critical review by a working group of the German commission on Air Pollution Prevention of VDI and DIN of the actual data on exposure and health effects (excluding cancer) of fine particulate air pollution is presented. EXPOSURE: Typical ambient particle concentrations for PM10 (PM2.5) in Germany are in the range of 10-45 (10-30) microg/m3 as annual mean and 50-200 (40-150) microg/m3 as maximum daily mean. The ratio of PM2.5/PM10 generally amounts between 0.7 and 0.9. HEALTH EFFECTS: During the past 10 years many new epidemiological and toxicological studies on health effects of particulate matter (PM) have been published. In summary, long-term exposure against PM for years or decades is associated with elevated total, cardiovascular, and infant mortality. With respect to morbidity, respiratory symptoms, lung growth, and function of the immune system are affected. Short-term studies show consistant associations of exposure to daily concentrations of PM with mortality and morbidity on the same day or the subsequent days. Patients with asthma, COPD, pneumonia, and other respiratory diseases as well as patients with cardio-vascular diseases and diabetes are especially affected. The strongest associations are found for PM2.5 followed by PM10, with no indication of a threshold value for the health effects. The data base for ultra fine particles is too small for final conclusions. The available toxicological data support the epidemiological findings and give hints as to the mechanisms of the effects. CONCLUSION: The working group concludes that a further reduction of the limit values proposed for 2005 will substantially reduce health risks due to particulate air pollution. Because of the strong correlation of PM10 with PM2.5 at most German sites there is no specific need for limit values of PM2.5 for Germany in addition to those of PM10.     

Characterization of thoracic fraction of airborne particular matter (PM10) in a urban area and in adjacent building

The aim of this study was to describe from a physico-chemical point of view the particles constituting the thoracic fraction of the airborne particulate matter (PM10) collected in two sampling stations: one in an urban area and another in an adjacent office building. The different sources contributing to the PM10 were identified and the relationship between the indoor PM10 and the outdoor PM10 assessed. Also the seasonal trend of PM10's physico-chemical characteristics was evaluated. Four particulate samplings were conducted between April 1999 and February 2000. The samples were analyzed by scanning electron microscopy with EDS X-ray attachment. The data sets, consisting of the atomic concentrations of the constituent chemical elements of the particulate, were subjected to Hierarchical Cluster Analysis to determine the principal components of PM10. The statistical analysis method allowed us to identify seven groups (clusters) of similar particles in the particulate matter: C-rich particles, carbonates, silica, silicates, sulphates, Fe-rich particles, metals. The seasonal trend of PM10 showed an increase in the alumino-silicates particles and a minor increment in sulphate particles in the summer. Moreover carbonaceous particles with a surface coating containing S were observed in the fine fraction of both outdoor and indoor particulate. This sulphurous coating turned out to be a strongly season-dependent feature. On the whole, the results suggest that the characteristics of indoor PM10 largely depend on the characteristics of outdoor PM10; the outdoor particulate quality had a major influence on the indoor particulate particularly during the summer season.     

Real-time measurement of indoor particulate matter originating from environmental tobacco smoke: a pilot study

Short-term measurement of suspended particulate matter has been recently made possible since the release of laser-operating portable instruments. Data of a pilot study of field evaluation of environmental tobacco smoke (ETS) with a portable instrument are reported. We analysed the concentrations of total suspended particle (TSP) and of the fine particles PM10, PM7, PM2.5 and PM1 released indoor from a single cigarette, and their levels inside smoking- and non-smoking-areas of a restaurant. The results indicate that ETS creates high level indoor particulate pollution, with concentrations of PM10 exceeding air quality standards. This kind of field evaluation could allow a more careful assessing of short-term exposure to ETS and its relevance to public health.     

Indoor particle counts during Asian dust events under everyday conditions at an apartment in Japan

Objective

Asian dust storms originating from arid regions of Mongolia and China are a well-known springtime phenomenon throughout East Asia. Evidence is increasing for the adverse health effects caused by airborne desert dust inhalation. Given that people spend approximately 90 % of their time indoors, indoor air quality is a significant concern. The present study aimed to examine the influence of outdoor particulate matter (PM) levels on indoor PM levels during Asian dust events under everyday conditions.

Methods

We simultaneously monitored counts of particles larger than 0.3, 0.5, 1, 2, and 5 μm using two direct-reading instruments (KC-01D1 airborne particle counter; Rion), one placed in an apartment room and another on the veranda, under everyday conditions before and during an Asian dust event. We also examined how indoor particle counts were affected by opening a window, crawling, and air purifier use.

Results

An Asian dust event on 24 April 2012 caused 50- and 20-fold increases in PM counts in outdoor and indoor air, respectively. A window open for 10 min resulted in a rapid increase of indoor PM counts up to 70 % of outside levels that did not return to baseline levels after 3 h. An air purifier rapidly reduced PM counts for all particle sizes measured.

Conclusions

It is important to account for occupant behavior, such as window-opening and air purifier use, when estimating residential exposure to particulate matter.     

Hemodynamic,Autonomic, and Vascular Effects of Exposure to Coarse Particulate Matter Air Pollution from a Rural Location

Background: Fine particulate matter (PM) air pollution is associated with numerous adverse health effects, including increased blood pressure (BP) and vascular dysfunction. Coarse PM substantially contributes to global air pollution, yet differs in characteristics from fine particles and is currently not regulated. However, the cardiovascular (CV) impacts of coarse PM exposure remain largely unknown.Objectives: Our goal was to elucidate whether coarse PM, like fine PM, is itself capable of eliciting adverse CV responses.Methods: We performed a randomized double-blind crossover study in which 32 healthy adults (25.9 ± 6.6 years of age) were exposed to concentrated ambient coarse particles (CAP; 76.2 ± 51.5 μg/m³) in a rural location and filtered air (FA) for 2 hr. We measured CV outcomes during, immediately after, and 2 hr postexposures.Results: Both systolic (mean difference = 0.32 mmHg; 95% CI: 0.05, 0.58; p = 0.021) and diastolic BP (0.27 mmHg; 95% CI: 0.003, 0.53; p = 0.05) linearly increased per 10 min of exposure during the inhalation of coarse CAP when compared with changes during FA exposure. Heart rate was on average higher (4.1 bpm; 95% CI: 3.06, 5.12; p < 0.0001) and the ratio of low-to-high frequency heart rate variability increased (0.24; 95% CI: 0.07, 0.41; p = 0.007) during coarse particle versus FA exposure. Other outcomes (brachial flow-mediated dilatation, microvascular reactive hyperemia index, aortic hemodynamics, pulse wave velocity) were not differentially altered by the exposures.Conclusions: Inhalation of coarse PM from a rural location is associated with a rapid elevation in BP and heart rate during exposure, likely due to the triggering of autonomic imbalance. These findings add mechanistic evidence supporting the biological plausibility that coarse particles could contribute to the triggering of acute CV events.Citation: Brook RD, Bard RL, Morishita M, Dvonch JT, Wang L, Yang HY, Spino C, Mukherjee B, Kaplan MJ, Yalavarthi S, Oral EA, Ajluni N, Sun Q, Brook JR, Harkema J, Rajagopalan S. 2014. Hemodynamic, autonomic, and vascular effects of exposure to coarse particulate matter air pollution from a rural location. Environ Health Perspect 122:624–630; http://dx.doi.org/10.1289/ehp.1306595     

Concentrations of nano and related ambient air pollutants at a traffic sampling site

A micro-orifice uniform deposit impactor (MOUDI) and a nano-MOUDI were used to measure the atmospheric coarse (PM2.5 -10), fine (PM2.5), ultrafine (PM0.056-1) and nano (<0.056 microm) particle concentrations and size distributions at a traffic sampling site in winter in central Taiwan, from November 2004 to January 2005. Concentrations of metallic elements (Fe, Mg, Cr, Zn, Pb, Cu) and major ion (SO4(2-), NO3(-), NH4(+)) in particles of various sizes (nano, ultrafine, fine and coarse) were measured. Ambient air particulates generally exhibited a bimodal size distribution in the range 0.056-10 microm. The results show that the concentrations followed the order, Fe>Mg>Cr>Zn>Pb> Cu in PM10, fine, ultrafine and nano-sized particles. Moreover, the data showed that the average metallic elements Fe and Zn have similar concentration distributions: the concentration decreased as the particle size fell in the nano size range.     

The fine fraction of airborne particulate: a pollutant of increasing environmental and health relevance. Methodologies for sampling and characterizing single particles

Among the atmospheric pollutants detectable in the environment, the inhalable airborne particulate (PM10) is regarded with increasing care. Indeed a number of epidemiological studies support the correlation between both acute and chronic adverse health effects and the PM10 pollution in the urban environment. According to recent results the health effects could be related to the physico-chemical characteristics of the particulate itself. With the aim of characterising the individual particles, PM10 samples collected by multi-stage cascade impactor are examined by scanning electron microscopy (SEM) and X-ray microanalysis with energy dispersion spectroscopy (EDS). The obtained data are analysed using multivariate statistical techniques (hierarchical clustering methods, principal factor analysis) to determine the components of the particulate. By these methods a series of studies was carried out by the Istituto Superiore di Sanità to investigate the PM10 pollution in several environmental situations.     

Coarse and fine particles and daily mortality in the Coachella Valley, California: a follow-up study

Many epidemiological studies provide evidence of an association between ambient particles, measured as PM10, and daily mortality. Most of these studies have been conducted in urban areas where PM10 is highly correlated with and dominated by fine particles less than 2.5 microm in diameter (PM2.5). Fewer studies have investigated impacts associated with the fraction of coarse mode particles (between 2.5 and 10 microm in diameter). In a previous study using data from 1989 through 1992 in the Coachella Valley, a desert resort and retirement area east of Los Angeles, we reported associations between PM10 and several different measures of mortality [Ostro B.D., Hurley S., and Lipsett M.J. Air pollution and daily mortality in the Coachella Valley, California: a study of PM10 dominated by coarse particles. Environ. Res. 1999: 81: 231-238]. In this arid environment, coarse particles of geologic origin are highly correlated with and comprise approximately 60% of PM10, increasing to >90% during wind events. This study was intended to repeat the earlier investigation using 10 years (1989-1998) of daily data on mortality and PM10. The last 2.5 years of data also included daily measures of PM2.5, allowing examination of size-specific impacts. To ensure adequate statistical power, we attempted to develop predictive models for both fine and coarse particles to use in analyses of the full 10-year period. An acceptable fit was found only for coarse particles, which were found to be a cubic function of PM10 (R2 = 0.95). Outcome variables included several measures of daily mortality, including all-cause (minus accidents and homicides), cardiovascular and respiratory mortality. Multivariate Poisson regression analyses using generalized additive models were employed to explain the variation in these endpoints, controlling for temperature, humidity, day of the week, season, and time, using locally weighted smoothing techniques. Pollution lags of up to 4 days were examined. Several pollutants were associated with all-cause mortality, including PM2.5, carbon monoxide and nitrogen dioxide. More consistent results were found for cardiovascular-specific mortality, for which associations were found for coarse particles (RR = 1.02; 95% C.I., 1.01-1.04), PM10 (RR = 1.03; 95% C.I., 1.01-1.05). None of the pollutants was associated with respiratory-specific mortality. Ozone was not associated with any of the mortality outcomes. These findings are generally consistent with those we previously reported for the Coachella Valley for the period 1989-1992, demonstrating associations between several measures of particulate matter and daily mortality in an environment in which particulate concentrations are dominated by the coarse fraction.     

Ambient air particulate dry deposition, concentrations and ionic species study at Taichung Harbor near Taiwan Strait

The characterization for watersoluble species of dry deposition flux, total suspended particulate (TSP), fine particle (particle matter with aerodynamical diameter 2.5 microm, PM2.5), coarse particle (particle matter with aerodynamical diameter 2.5-10 microm, PM(2.5-10)), and dry deposition velocity were studied at Taichung Harbor sampling sites of central Taiwan during February-August 2004. The average downward dry deposition flux, TSP, PM10 concentrations obtained in Taichung Harbor were about 0.51, 0.3, and 3.4 times more than those values obtained by traffic sampling site in central Taiwan. Average dry deposition velocity for mass, Cl-, NO3-, SO4(2-), Na+, NH4+, Mg2+, and Ca2+ were 9, 3.8, 0.3, 0.25, 0.46, 0.18, 0.51 and 2.28 cm respectively at the harbor sampling site. In general, average particle mass dry deposition velocity was about 1.8 times more than those values obtained at the traffic sampling site. Chemical analysis, also indicated that three major soluble inorganic species concentrations (sulfate+nitrate+ammonium) accounted for 59.8% and 80.6% of the PM2.5 and PM(2.5-10) mass concentrations, respectively at the Taichung Harbor sampling site.     

Airborne particulate matter and premature deaths in urban Europe: the new WHO guidelines and the challenge ahead as illustrated by Spain

Twenty first century epidemiological publications on urban air pollution are confirming that inhalation of fine, airborne particulate matter (PM) has serious chronic human health effects and is a major cause of premature death worldwide. Recently updated recommendations by WHO identify three “Interim Targets” for the stepped reduction in PM levels within world cities in the quest to achieve an annual mean Air Quality Guideline (AQG) concentration of 20 μg/m³ for particles less than 10 microns in size (PM₁₀). In this paper we offer a perspective from Spain, a country with the longest record of reporting pollution data from large numbers of urban traffic sites to a central European database (AIRBASE). We can demonstrate that average annual PM concentrations at urban traffic monitoring stations in many European cities continue to be 50–100% above the WHO AQG, a situation exacerbated by high urban PM_2.5/10 ratios which indicate a dominance of finer, more deeply inhalable particles potentially more detrimental to health. Given that WHO has estimated in 2000 there were well over 250,000 premature deaths in Europe attributable to PM inhalation, such continuing high urban pollution levels are placing a huge burden on European medical resources.     

Focused exposures to airborne traffic particles and heart rate variability in the elderly

BACKGROUND:: Exposure to airborne particles may increase cardiac risk by altering autonomic balance. Because these risks may be particularly great for traffic-related particles, we examined associations between particles and heart rate variability as 44 subjects participated in 4 repeated trips aboard a diesel bus. METHODS:: Twenty-four hour electrocardiograms were correlated with continuous particle concentrations using generalized additive models controlling for subject, weekday, time, apparent temperature, trip type, activity, medications, and autoregressive terms. Associations were assessed for short- and medium-term moving averages of measured concentrations. RESULTS:: Heart rate variability was negatively associated with fine particulate matter. Positive associations were demonstrated with heart rate and the low-to-high frequency power ratio. Associations were strongest with 24-hour mean concentrations, although strong short-term associations also were found during bus periods, independent of daily exposures. Overall, associations were greatest for high-frequency power with the following effects per interquartile change in the 24-hour mean concentrations: -15% (95% confidence interval = -17% to -14%) for PM2.5 (4.6 mug/m); -19% (-21% to -17%) for black carbon (459 ng/m); and -14% (-15% to -12%) for fine particle counts (39 pt/cm). For each interquartile change in the 5-minute PM2.5 concentration (10 mug/m) aboard the bus, an 11% (95% confidence interval = -14% to -8%) decrease in high-frequency power was observed. CONCLUSIONS:: This investigation indicates that fine particles are negatively associated with heart rate variability, with an overall trend towards reduced parasympathetic tone. Although daily associations were evident for all particles, short-term associations were predominantly limited to traffic-related particles.     

Acute effects of ambient temperature and particulate air pollution on fractional exhaled nitric oxide: A panel study among diabetic patients in Shanghai,China

Background

Epidemiological studies have shown the associations of ambient temperature and particulate matter (PM) air pollution with respiratory morbidity and mortality. However, the underlying mechanisms have not been well characterized. The aim of this study is to investigate the associations of temperature and fine and coarse PM with fractional exhaled nitric oxide (FeNO), a well-established biomarker of respiratory inflammation.

细颗粒物免疫毒性研究进展

大气中细颗粒物的暴露是多种健康问题的危险因素 ,而免疫系统是细颗粒物毒性作用的靶器官之一 ,细颗粒物对非特异性免疫系统和特异性免疫系统均有一定影响。免疫系统作用有两面性 ,既对颗粒物具有一定的清除能力 ,同时也是机体受损的重要原因。免疫毒性与颗粒物产生的其他生物效应有密切关系。免疫毒性的作用机制可能通过氧化、炎症刺激和神经性炎症反应等有关 ,但具体致病机制仍不清楚 ,有必要从整体上研究颗粒物的毒性及其作用机制。本文从不同角度和不同水平对细颗粒物的免疫毒性进行综述。     

A method for dry extracting large volumes of fine particulate matter from bulk soil samples

A significant part of ambient dust consists of fine particles derived from natural soils. Because many toxic constituents are concentrated in the smallest particle fractions, and because these small particulates are the most easily inhaled, the fine-particle fraction of soil (PM10 and smaller) is what presents the greatest health concern. Assessing the potential risk of a soil requires examining its chemical content, its biological and mineralogical composition, its sedimentological characteristics, detailed data on grain size distribution, and other information. This analysis requires a relatively large mass of appropriate size fraction(s), obtained by dry extraction. Most methods for extracting fine particulates from soil collect only small amounts of sediment, or use wet extraction. This paper describes the Soil Fine Particle Extractor, a setup for dry extracting large volumes (dozens of grams and more) of fine particulate matter (PM10 and smaller) from bulk soil samples. Separation takes place in two steps. Primary separation in a cylindrical separator 70?cm high and 40?cm in diameter removes all coarse particles from the sample. The remaining sediment then flows through a 200?cm long and 7?cm diameter inclined elutriator connected to a three-engine vacuum cleaner. The setup allows extraction of different size fractions depending on the adjustment of the control parameters (suction rate, length, diameter and inclination of the elutriator, thickness of the sediment layer drawn in by the system). The article presents examples of extractions from soil collected in loess and desert environments, ranging from PM2.5 to PM10. It also evaluates the efficiency of the technique by investigating the extraction efficiency for a large number of particle sizes, varying from 0.1 to 70???m. Extraction occurs most efficiently for particles between 1 and 10???m, with an optimum around 5???m.     

Comparison of fine particle measurements from a direct-reading instrument and a gravimetric sampling method

Particulate air pollution, specifically the fine particle fraction (PM2.5), has been associated with increased cardiopulmonary morbidity and mortality in general population studies. Occupational exposure to fine particulate matter can exceed ambient levels by a large factor. Due to increased interest in the health effects of particulate matter, many particle sampling methods have been developed In this study, two such measurement methods were used simultaneously and compared. PM2.5 was sampled using a filter-based gravimetric sampling method and a direct-reading instrument, the TSI Inc. model 8520 DUSTTRAK aerosol monitor. Both sampling methods were used to determine the PM2.5 exposure in a group of boilermakers exposed to welding fumes and residual fuel oil ash. The geometric mean PM2.5 concentration was 0.30 mg/m3 (GSD 3.25) and 0.31 mg/m3 (GSD 2.90)from the DUSTTRAK and gravimetric method, respectively. The Spearman rank correlation coefficient for the gravimetric and DUSTTRAK PM2.5 concentrations was 0.68. Linear regression models indicated that log, DUSTTRAK PM2.5 concentrations significantly predicted loge gravimetric PM2.5 concentrations (p < 0.01). The association between log(e) DUSTTRAK and log, gravimetric PM2.5 concentrations was found to be modified by surrogate measures for seasonal variation and type of aerosol. PM2.5 measurements from the DUSTTRAK are well correlated and highly predictive of measurements from the gravimetric sampling method for the aerosols in these work environments. However, results from this study suggest that aerosol particle characteristics may affect the relationship between the gravimetric and DUSTTRAK PM2.5 measurements. Recalibration of the DUSTTRAK for the specific aerosol, as recommended by the manufacturer, may be necessary to produce valid measures of airborne particulate matter.