Performance testing of the OSIRIS dust monitoring system

OSIRIS is a monitoring system for non-fibrous dusts based on optical scattering methods. It was developed by HSE's Safety Engineering Laboratory primarily for use in the coal-mining industry as an alternative to gravimetric sampling. Up to eight dust monitors can be controlled by a microcomputer via a two-wire telemetry link at distances of up to 8 km. The paper reports the results of comparative tests between OSIRIS and the MRE 113A gravimetric sampler in a calm air dust box, in a wind tunnel and in field trials at two collieries. Results show that OSIRIS can be calibrated against the MRE 113A for a given dust and that the calibration is maintained over the normal working range of 0-40 mg m-3. Results of tests against a variety of available test dusts show that the physical and optical properties of the dust particles have a significant effect on the response of the instrument. OSIRIS therefore needs to be calibrated against a gravimetric sampler for each dust which it will be used to monitor. Once calibrated, OSIRIS would be useful in monitoring respirable dust concentrations in a wide range of industrial or laboratory situations.     

Methods to assess airborne concentrations of cotton dust

Assessment of concentrations of airborne cotton dust in the factory is necessary to determine adherence to applicable Permissible Exposure Limits (PELs) on a day-to-day basis, as well as for investigatory studies of an epidemiological nature. The latter are required on an ongoing basis to determine the adequacy of PELs to prevent disease in the exposed population. A strategy of sampling includes considerations of the numbers of samples to be obtained for statistical validity and the locations of samples. Current practice is to obtain more "personal samples" of exposure wherever possible, but with regard to cotton dust, instrumentation is not available for such sampling. In the U.S., the vertical elutriator is the instrument of choice for determining the concentrations of cotton dust in air. Results are expressed as milligrams of airborne particulate (cotton dust) per cubic meter.     

Performance of the RespiCon personal aerosol sampler in forest products industry workplaces

The RespiCon is a multistage virtual impactor that can be used as either a personal or an area sampler. Particles collected on the first stage of the RespiCon represent the respirable fraction of airborne particulate matter. Particles collected on the first and second stages represent the thoracic fraction, and particles collected on the first, second, and third stages represent the inhalable fraction. The RespiCon is available in two versions, one with photometric aerosol detection and a gravimetric version. In this study, the performance of the gravimetric version was examined in various forest products industry facilities. The precision of the RespiCon was assessed and its performance was compared with that of both a respirable cyclone and an inhalable dust sampler. In addition, some RespiCon samples were examined using scanning electron microscopy to determine physical particle size distribution. Under the conditions of this testing, the RespiCon appeared to be reasonably precise. For most sampling locations there was a close correspondence between measurements made with the RespiCon and the CIS personal inhalable sampler or the BGI-4 respirable cyclone. The results of microscopic examination of filters from the RespiCon were consistent with expected performance characteristics. The RespiCon is a useful sampling device for those situations in which it is important to simultaneously collect either personal or area samples of the respirable, thoracic, and inhalable fractions of airborne particulate matter.     

Temporal variation of airborne fungi concentrations and related factors in subway stations in Seoul, Korea

This study was performed to assess the levels of fungi concentration in subway stations in Seoul, Korea, and to investigate factors contributing to these concentrations. Ninety air samples were collected hourly over the course of a day from five different subway stations. In addition, five settled dust samples and 12 stagnant water samples were collected to investigate these as potential sources of fungi contamination. The number of passengers and frequency of passing trains were also determined during the sampling periods, as they were considered potential factors influencing the airborne fungi concentrations at a given time during the day. The airborne fungi concentrations, as a function of time, were log-normally distributed. The airborne fungi concentrations measured during the morning and evening commute hours (during which the number of passengers and frequency of passing trains was highest) were significantly higher than those measured during non-commute hours. High concentrations of fungi were found in the settled dust samples, suggesting that the settled dust may have been the main source of airborne fungi concentration. The air movement generated mainly by passengers and additionally by trains might have played a role in suspending the fungi from the settled dust. It was also found that stagnant water might be a potential source of airborne fungi.     

Measuring cyclone for the evaluation of dust sampling instruments SPG 10 AND SPG 210

For dust measuring instruments which are used in industrial hygiene-according to standards there were required certain limited controls of the measurements validity. There is, however, no testing tool available, suitable for the applicants, for a gravimetric dust measuring instrument. It is proposed a measuring cyclone for industrial routine, which can be prepared and graduated with little effort. Examinations of the instruments SPG 10 and SPG 210 so far have shown a close dependence between the volume flow and the resistance to flow of the specific dust filter. The volume flow, actually effective for the grain fraction's separation of the airborne dust into certain parts of coarse dust and lung damaging fine dust in the dust precipitator's first stage may be inadmissibly different from the nominal flow. It is therefore proposed in addition to the necessary check of the measuring devices to establish the relation between volume flow and filter covering for every instrument.     

Passive sampler used for simultaneous measurement of breathing zone size distribution,inhalable dust concentration and other size fractions involving large particles

The particle size-dependent sampling velocity of the passive dust sampler developed by Vinzents (1996) is investigated under field conditions. Microscopical determination of the projected area equivalent diameter is used to quantify particles deposited on the sampler foils. Parameters for a semi-empirical model for particle deposition velocities on upward and forward facing foils are fitted to the data and it is shown that deposition mechanisms other than gravitational settling on the upward facing foil can be neglected. For calculation of airborne mass concentration no information on particle density is needed and only the ratio between the dynamic and volume shape factors needs to be known. Given the sampling velocity, the airborne mass per diameter interval is calculated from samples obtained in the wood industry, from which inhalable dust concentrations are calculated. The results are in line with parallel samples obtained with an inhalable dust sampler. A 'total' dust sampling characteristic can be fitted which reproduces measured 'total' dust with a closed face monitor. The results of this study demonstrate the validity of the passive dust sampling principle in environments involving even large (>100 microm) particles and the potential to predict the concentration of several size fractions.     

Efficiency of dust sampling inlets in calm air.

Measurement of airborne dust concentrations usually involves drawing a sample of the dust-laden air into the measuring instrument through an inlet. Even if the surrounding air is calm, theoretical calculations predict that large particles may not be sampled accurately due to the combined effects of gravity and inertia on the particles near the sampling inlet. Tests were conducted to determine the conditions of particle size, inlet radius, and flow rare necessary for accurate dust sampling. A coal-dust aerosol was sampled simultaneously through inlets of different diameters at the same volume flow-rate and collected on filters. The dust was removed from the filters and the particles were counted and sized with a Coulter counter. Results showed that published criteria for inlet conditions for correct sampling are overly restrictive and that respirable-size particles are sampled correctly in the normal range or operation of most dust sampling instruments.     

Assessment of personal direct-reading dust monitors for the measurement of airborne inhalable dust

The performances of five portable direct-reading dust monitors were investigated in a wind tunnel for a range of industrial dusts and three sizes of aluminium oxide test dust to mainly determine their suitability for measuring the inhalable fraction of airborne dust in workplaces. The instruments tested were Split 2 (SKC Ltd), Sidepak (TSI Inc.), Dataram (Thermo Electron Ltd), PDS-2 (Sibata Scientific Technology Ltd) and the Respicon TM (Hund Ltd). The instruments' responses were compared with reference dust samplers. These were the IOM sampler for the inhalable fraction and the Casella cyclone sampler for the respirable fraction. All instruments are predominantly responsive to and are designed to measure particles in the respirable size range, although two of the instruments, the Split 2 and Respicon TM, are claimed to be capable of measuring inhalable-sized particles. For the purpose of the tests, major modifications to an existing wind tunnel dust injection system were made to facilitate the generation of uniform concentrations of large inhalable-sized dust particles at low air velocities. Each monitor greatly underestimated the measurement of inhalable concentration for all the dusts tested, although the linearity was good over a wide range of concentrations for any particular size distribution of dust. However, their calibration factors, defined as the ratio of reference inhalable concentration to monitor concentration, were especially sensitive to changes in particle size as the response of the instruments decreased rapidly with increasing particle size. The monitors generally overestimated the measurement of respirable dust concentration by up to a factor of about 2, apart from the PDS-2, which underestimated it by a factor of up to 3. There was, however, a great deal more scatter in the reference respirable concentration measurements owing to the collection of small dust samples. Therefore, monitor linearity and effects of monitor response to changes in particle size could not be accurately investigated for the respirable fraction. The sampling head of the Split 2 monitor incorporates an IOM inlet and filter to gravimetrically collect the inhalable fraction of airborne dust. This can give a concurrent reference measure of inhalable airborne dust concentration. However, poor sealing within the sampling head resulted in some of the sampled dust not reaching the backup filter. This resulted in the Split 2 underestimating the reference inhalable dust concentration, which meant that it could not be accurately used as a calibration standard. Communications with the manufacturers have since revealed that the sampling head has recently been redesigned in order to improve the seal and eliminate leakage. The Respicon sampler gravimetrically underestimated the inhalable dust concentration, and did so increasingly as the particle size increased.     

Sampling and analysis method for measuring airborne coal dust mass in mixtures with limestone (rock) dust

Airborne coal dust mass measurements in underground bituminous coal mines can be challenged by the presence of airborne limestone dust, which is an incombustible dust applied to prevent the propagation of dust explosions. To accurately measure the coal portion of this mixed airborne dust, the National Institute for Occupational Safety and Health (NIOSH) developed a sampling and analysis protocol that used a stainless steel cassette adapted with an isokinetic inlet and the low temperature ashing (LTA) analytical method. The Mine Safety and Health Administration (MSHA) routinely utilizes this LTA method to quantify the incombustible content of bulk dust samples collected from the roof, floor, and ribs of mining entries. The use of the stainless steel cassette with isokinetic inlet allowed NIOSH to adopt the LTA method for the analysis of airborne dust samples. Mixtures of known coal and limestone dust masses were prepared in the laboratory, loaded into the stainless steel cassettes, and analyzed to assess the accuracy of this method. Coal dust mass measurements differed from predicted values by an average of 0.5%, 0.2%, and 0.1% for samples containing 20%, 91%, and 95% limestone dust, respectively. The ability of this method to accurately quantify the laboratory samples confirmed the validity of this method and allowed NIOSH to successfully measure the coal fraction of airborne dust samples collected in an underground coal mine.     

石棉造纸行业粉尘重量浓度与纤维计数浓度关系研究

本文用现场平行采样的方法研究石棉造纸行业的各扬尘点粉尘重量浓度与纤维计数浓度间的转换关系。结果认为,可以对各不同工作点分别找出两种浓度的转换关系,可据此将该厂过去测定的重量浓度记录转换为纤维计数浓度,为进行石棉纤维计数浓度的剂量-反应关系计算提供基本资料。     

空气中石棉浓度的测定与矿工微核率关系的探讨

石棉为诱变物,应用计重法和计数法,测定朝阳新生石棉矿10个车间空气中石棉尘浓度及矿工末梢血淋巴细胞微核率。结果得出:两种方法测得值无相关性。矿工血微核率的增加与计数法石棉纤维数值相关显著,与工龄成正比,与计重法无关。说明计重法不能代替计数法,只有计数法才能真正反映石棉的致病作用。     

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.     

Evaluation and field calibration of the Miniram PDM-3 aerosol monitor for measuring respirable and total coal dust.

The MIE Miniram PDM-3 is a real-time aerosol dust monitor designed to measure dust based on Mie scattering. It has an optional in-line filter that, when attached to a constant flow air sampling pump, allows a gravimetric air sample to be collected from the same air stream that passes through the Miniram sensing chamber. This study compared real-time Miniram digital respirable and total dust readings with concentrations from an in-line 5 microns polyvinyl chloride filter connected to a constant flow pump and with results from traditional respirable and total dust samples. Area samples were collected at three coal-fired power generating facilities over a 2-month period. Traditional respirable dust concentrations ranged from 0.04 to 10.8 mg/m3. In the monitored range of concentrations the Miniram respirable concentrations and the in-line respirable dust concentrations were not significantly different (p > or = 0.05), nor were the Miniram in-line filter concentrations and the side-by-side respirable dust concentrations significantly different (p > or = 0.05). However, the Miniram respirable concentrations and the traditional respirable concentrations were significantly different (p = 0.02). The Statistical Analysis System (SAS) procedure CALIS, which meets the statistical requirements for developing calibration lines for two variables each measured with error, is used to develop field calibration curves for the comparisons between direct-reading instrument concentrations and concentrations from traditional National Institute for Occupational Safety and Health methods for total and respirable dust.     

Respirable Dust and Respirable Silica Exposure in Ontario Gold Mines

A comprehensive survey of respirable dust and respirable silica in Ontario gold mines was conducted by the Ontario Ministry of Labor during 1978–1979. The aim was to assess the feasibility of introducing gravimetric sampling to replace the assessment method which used konimeters, a device which gave results in terms of number of particles per cubic centimeter (ppcc) of air. The study involved both laboratory and field assessments. The field assessment involved measurement of airborne respirable dust and respirable silica at all eight operating gold mines of the time. This article describes the details of the field assessment. A total of 288 long-term (7–8 hr) personal respirable dust air samples were collected from seven occupational categories in eight gold mines. The respirable silica (α-quartz) was determined by x-ray diffraction method. The results show that during 1978–1979, the industry wide mean respirable dust was about 1 mg/m³, and the mean respirable silica was 0.08 mg/m^3.The mean% silica in respirable dust was 7.5%. The data set would be useful in future epidemiological and health studies, as well as in assessment of workers’ compensation claims for occupational diseases such as silicosis, chronic obstructive pulmonary disease (COPD), and autoimmune diseases such as renal disease and rheumatoid arthritis.     

Endotoxin,cat, and house dust mite allergens in electrostatic cloths and bedroom dust

Environmental exposure to endotoxin, Fel d I (cat) allergen and Der p I (house dust mite) allergen have been associated with asthma symptoms and have been measured in the environment using various sampling methods, including the electrostatic dust collector. The objectives of this study were to investigate whether levels of endotoxin and allergens were detectable in electrostatic dust collectors and to examine the correlation of allergen and endotoxin levels between electrostatic dust collectors and vacuum sampling methods (floor dust and mattress dust). Electrostatic cloths, bedroom floor dust and mattress dust samples from a subset of 60 homes were randomly selected from the Health of Occupants of Mouldy Homes study for allergen and endotoxin analysis. Fel d I and Der p I allergens were analyzed by double monoclonal antibody ELISA and endotoxin by the kinetic Limulus amoebocyte lysate assay. An enhanced ELISA method was used to analyze Der p I in the electrostatic cloths. Endotoxin was detected in all samples, however Fel d I and Der p I were not detected in all electrostatic dust collector samples (detection in 53% and 15% of cloths respectively). No correlations were found between cloth and dust samples for endotoxin or Der p I, but moderate-to-strong correlations were found between all three sampling methods for Fel d I (r_s = 0.612–0.715, p < 0.001). Poor correlation was found between floor dust and mattress dust samples for Der p I (r_s = 0.256, p = 0.048). Electrostatic dust collectors may provide a way to measure airborne dust and allergen. Given the moderate-to-low correlations with vacuum dust sampling, this may present a unique measurement system which, when collected alongside traditional vacuum dust sampling, could provide additional exposure measures. Further studies are required to correlate endotoxin and allergen levels measured by electrostatic dust collector with air sampling and to explore the relationships between these bioaerosols, environmental factors and asthma.     

Estimating factors to convert Chinese 'Total Dust' measurements to ACGIH respirable concentrations in metal mines and pottery industries

Historical data on the dust exposures of Chinese workers in metal mines (iron/copper, tin, tungsten) and pottery industries are being used in an ongoing joint Chinese/United States epidemiological study to investigate the exposure-response relationship for the development of silicosis, lung cancer, and other diseases. The historical data include 'total dust' concentrations determined by a Chinese method. Information about particle size distribution and the chemical and mineralogical content of airborne particles is generally not available. In addition, the historical Chinese sampling strategy is different from a typical American eight-hour time-weighted average (TWA) sampling strategy, because the Chinese samples were collected for approximately 15 minutes during production so the sample could be compared to their maximum allowable concentration (MAC) standard. Therefore, in order to assess American respirable dust exposure standards in light of the Chinese experience, factors are needed to convert historical Chinese total dust concentrations to respirable dust concentrations. As a part of the joint study to estimate the conversion factors, airborne dust samples were collected in 20 metal mines and 9 pottery factories in China during 1988 and 1989 using three different samplers: 10mm nylon cyclones, multi-stage 'cassette' impactors, and the traditional Chinese total dust samplers. More than 100 samples were collected and analysed for each of the three samplers. The study yielded two different estimates of the conversion factor from the Chinese total dust concentrations (measured during production processes) to respirable dust concentrations. The multivariate analysis of variance (MANOVA) reveals that, with a fixed sampling/analysis method, conversion factors were not statistically different among the different job titles within each industry. It also indicates that conversion factors among the industries were not statistically different. However, the two estimates consistently showed that conversion factors were the lowest in the pottery industry. Average conversion factors were then calculated for each of the estimates across the industries studied. A pooled mean conversion factor, 0.25+/-0.04, was then derived for all the job titles and industries. Respirable dust levels were estimated from the historical 'total dust' concentrations collected between 1952 and 1992 by adopting the American standard.     

Longitudinal study of dust and airborne endotoxin in the home

To characterize the seasonal variability of endotoxin levels, we measured endotoxin in dust from the bed, bedroom floor, and kitchen floor in 20 homes, and in air from the bedroom in 15 of the homes. All homes were located in the greater Boston, Massachusetts, area and were sampled each month from April 1995 to June 1996. Outdoor air was collected at two locations. We found greater within-home than between-home variance for bedroom floor, kitchen floor, and airborne endotoxin. However, the reverse was true for bed dust endotoxin. Thus, studies using single measurements of dust endotoxin are most likely to reliably distinguish between homes if bed dust is sampled. Dust endotoxin levels were not significantly associated with airborne endotoxin. Airborne endotoxin was significantly (p = 0. 04) and positively associated with absolute humidity in a mixed-effect model adjusting for a random home effect and fixed effect of sampling month and home characteristics. This finding implies that indoor humidity may be an important factor controlling endotoxin exposure. We found a significant (p < 0.05) seasonal effect in kitchen floor dust (spring > fall) and bedroom airborne endotoxin (spring > winter), but not in the other indoor samples. We found significant seasonal pattern in outdoor airborne endotoxin (summer > winter).     

A new static sampler for airborne total dust in workplaces

This paper describes the development and laboratory testing of a new static dust sampler for airborne total dust in workplaces. Particular attention is paid to designing the sampling head and entry consistent with the concept of inspirability which in turn defines a biologically-relevant aspiration efficiency. The sampling head has a small cylindrical body and a transverse entry slot with thin protruding lips forming an integral part of a weighable capsule containing a 37 mm filter which collects all of the sampled dust (without introducing errors due to external particle blow-off or internal wall losses). A battery-powered sampling pump provides both air suction at 3 L/min and rigid mounting for the sampling head. The sampling head is rotated continuously through 360 degrees at approximately 1.5 rpm by a simple electric drive, connected to the stationary pump through a rotating seal. Wind tunnel testing of the instrument showed it to display an entry efficiency very close to the inspirability curve of Vincent and Armbruster (now recommended by the ACGIH Technical Committee on Air Sampling Procedures for defining inspirable particulate matter (IPM] for particles of aerodynamic diameter up to 90 micron and for windspeeds in the range of one to three m/sec.     

Fungal types and concentrations from settled dust in normal residences

Analysis of settled dust collected from carpeting and furnishings is occasionally used by investigators to determine whether an environment contains unusual fungi. Little information is available concerning the types and concentrations of culturable fungi present on textile surfaces in normal residential settings not affected by unusual mold reservoirs, such as from fungal growth sites within the built environment. This study presents the results of the collection and analysis of surface dust from 26 residential environments that were prescreened by interview, physical inspection, and air sampling to limit the surface dust collection to structures in which there was no history of water intrusion, flooding, plumbing leaks, signs of mold growth, or evidence of unusual airborne fungal spore types or concentrations. In those structures found to have no history or indications of water events or unusual fungi, surface dust was vacuumed from prescribed horizontal areas on carpet and textile-covered furnishings. These samples were then subjected to fungal culture, from which viable colonies were enumerated and identified. Based on the study results, it does not appear reasonable that the frequently quoted total fungi concentration exceeding 10(5) CFU/g is definitive evidence that a residential surface is contaminated with unusual amounts of culturable fungi. Collocated samples collected from eight side-by-side carpets sections revealed poor reproducibility. While settled dust sampling may be appropriate for determining the fungal status of a localized area, or as a gross screening tool, using settled dust results alone to establish the presence of unusual fungal types or concentrations within a structure appears to be inappropriate, and using settled dust results with other investigative methods, such as visual observations and air sampling, requires cautious interpretation.