Performance testing of three portable,direct-reading dust monitors

Three portable direct-reading dust monitors were tested in a recirculating dust tunnel and a calm air dust chamber against a range of industrial dusts with different size distributions to investigate sources of variation in their responses. Responses were found to be linear compared to reference gravimetric respirable samplers over a range of concentrations for a particular particle size distribution. Their calibration factors were dependant on particle size, particle composition and air velocity. If particle size and air velocity do not change significantly then the calibration factor can be applied to the monitor readings to give an accurate measure of dust concentration. The DataRam and HAM, factory calibrated against respirable dust concentration, were found to agree closely, whereas the Microdust gave higher readings, having been factory calibrated against total suspended particulate concentration. The calibration of the DataRam was significantly altered by either contamination of the optics with dust or by cleaning the optics. This was not observed with either the Microdust or HAM, since both monitors include a reference calibration element.     

Field comparison of personal samplers for inhalable dust

The performances of two designs of personal inhalable fraction sampler, which have been shown to differ in laboratory wind tunnel studies, were assessed in 23 real industrial environments, relative to the collection of dust by a simulated worker. This took the form of a mobile, articulated, breathing robot which was fitted with an oral filter, and could be moved around the workplace to follow and mimic real workers. Statistical analysis of the resulting data show that if a small correction for bias is applied there is no significant difference either between the personal samplers as predictors of the 'real' worker exposure, or in the reproducibility obtained with the two personal samplers. The ratio between dust concentrations measured simultaneously on opposite lapels was greater than 2 on more than 5% of occasions, and is believed to be largely due to real concentration gradients in the environments sampled. It would appear that the differences between sampler performances demonstrated in laboratory studies are not significant under conditions encountered in the field.     

Field comparison of inhalable and total dust samplers for assessing airborne dust in swine confinement barns

Inhalable and total dust sampling devices were compared for evaluating airborne dust in swine confinement buildings. Measurements from three swine facilities (n = 77 paired means) were obtained by area sampling using the IOM (Institute of Occupational Medicine, Edinburgh, U.K.) inhalable dust sampler and a 37-mm closed-face total (TCF) dust sampler. The overall geometric mean IOM concentration (1.18 mg/m(3), geometric standard deviation [GSD] = 2.00) was significantly greater (P < 0.05) than the overall geometric mean TCF concentration (1.08 mg/m(3), GSD = 1.98). Regression analysis with IOM and TCF values as independent and dependent variables, respectively, yielded a factor of 0.86 (+/-0.04 95% confidence interval), which can be used to estimate TCF values from the IOM measurements. Additional paired sampling data were obtained to compare the following pairs of dust samplers: (1) IOM sampler and conical inhalable sampler (CIS) (n = 20 paired means), (2) IOM and open-face total (TOF) dust samplers (n = 14), (3) CIS and TCF samplers (n = 19), and (4) TCF and TOF samplers (n = 8). Paired t-tests showed significantly (P < 0.05) higher IOM concentrations than the CIS sampler; no significant difference (P > 0.05) was found for the other three pairs compared. It may be necessary to establish work-specific conversion coefficients to obtain a reasonable estimate of worker exposure to total dust from measurements using other types of dust sampling devices.     

Scientific principles and pragmatic solutions for the measurement of exposure to inhalable dust

In order to understand and control the risks presented by inhalation of dust at work, research over many years has been focused on understanding how dust present in the air enters the human nose and mouth during the act of breathing. For health-related dust exposure monitoring, sampling devices are needed that collect the same 'inhalable fraction' of dust as the human head. Mark and Vincent's 1986 paper presented a study that has contributed more than any other to the practical realization of this inhalable dust concept. The authors developed a simple solution--the IOM personal inhalable dust sampler--to what we now know is an extremely complex problem. Although scientific understanding has grown in the years since this paper was published, very few other dust sampling instruments have emerged as being able to meet both the scientific criteria and the practical need for inhalable dust measurement. Both authors have continued to build on this work and have made further contributions to our theoretical and practical understanding in this field.     

Assessment of bioaerosols and inhalable dust exposure in Swiss sawmills

An assessment of wood workers' exposure to airborne cultivable bacteria, fungi, inhalable endotoxins and inhalable organic dust was performed at 12 sawmills that process mainly coniferous wood species. In each plant, samples were collected at four or five different work sites (debarking, sawing, sorting, planing and sawing cockpit) and the efficiency of sampling devices (impinger or filter) for determining endotoxins levels was evaluated. Results show that fungi are present in very high concentrations (up to 35 000 CFU m(-3)) in all sawmills. We also find that there are more bioaerosols at the sorting work site (mean +/- SD: 7723 +/- 9919 CFU m(-3) for total bacteria, 614 +/- 902 CFU m(-3) for Gram-negative, 19 438 +/- 14 246 CFU m(-3) for fungi, 7.0 +/- 9.0 EU m(-3) for endotoxin and 2.9 +/- 4.8 g m(-3) for dust) than at the sawing station (mean +/- SD: 1938 +/- 2478 CFU m(-3) for total bacteria, 141 +/- 206 CFU m(-3) for Gram-negative, 12 207 +/- 10 008 CFU m(-3) for fungi, 2.1 +/- 1.9 EU m(-3) for endotoxin and 0.75 +/- 0.49 mg m(-3) for dust). At the same time, the species composition and concentration of airborne Gram-negative bacteria were studied. Penicillinium sp. were the predominant fungi, while Bacillus sp. and the Pseudomonadacea family were the predominant Gram-positive and Gram-negative bacteria encountered, respectively.     

The application of performance standards to personal airborne dust samplers

This paper summarizes current proposals for the specification and testing of personal sampler performance, and discusses their implications for the precision of dust concentration estimates. A method of specifying the performance of a sampling instrument in terms of the range of masses it would collect from various dust clouds is proposed. Some of the practical difficulties which are likely to arise in the process of testing real samplers with respect to performance standards are discussed.     

A method for establishing tentative occupational exposure limits for inhalable dust

Four-fold classification tables are used on five datasets containing 112 parallel personal measurements of total dust and inhalable dust. The classifications are carried out in such a way that the frequency of non-compliance is equal for total dust and inhalable dust. The results can be used as tentative occupational exposure limits (OELs) for inhalable dust, and the results range from 0.7 to 3.4 of OELs for total dust. The results depend on the industry and the content of the dust.     

Laboratory and field testing of sampling methods for inhalable and respirable dust

The performance of four sampling devices for inhalable dust and three devices for respirable dust was tested with different kinds of dusts in the laboratory and in the field. The IOM sampler was chosen as the reference method for inhalable dust, and the IOM sampler provided with the porous plastic foam media was used as the reference method for respirable dust. The other tested instruments were the Button sampler, the optical Grimm aerosol monitor, and the Dekati two-stage cascade impactor with cutoff sizes of 10 and 4 mu m. The study confirmed the applicability of the IOM and Button samplers. The new foam product followed the respirable criteria well. However, the foam sampler was unstable for measuring inhalable dust, probably due to its moisture absorption. In addition, high dust loads should be avoided with the foam sampler due to increase in filtering efficiency. The concentrations of inhalable dust measured with the Button sampler, the Grimm monitor, and the impactor sampler were usually close to those measured with the reference sampler. On the other hand, impactor sampling yielded higher respirable dust concentrations than the reference method in the field, which may have been caused by particle bounce; high dust loads should be avoided while using the impactor. The results also showed that the Grimm monitor enables real-time dust concentration determinations that are accurate enough for routine monitoring of occupational exposure and for testing efficiency of control measures in workplaces.     

Weighing imprecision and handleability of the sampling cassettes of the IOM sampler for inhalable dust

The weight stability of the sampling cassette of the IOM sampler for inhalable dust was tested in several weighing experiments. The results show that the reliability of repeated weighings was good, but the absorption of water vapour was slow and varied considerably among cassette specimen. The exponential time constant for water absorption was approximately 4 days, and 15-20 days were needed to obtain weight stability. With the help of cassette blanks the imprecision in dust weight could be held below 0.05 mg, if the cassettes were allowed one week's storage in the weighing room before weighing, both before and after sampling. The IOM sampling cassettes seem to consist of a few subsets, each with identical relative weight increase in a weighing room. To keep the variability low it is important that both the blanks and the cassettes used for sampling come from the same subset. Experiments indicate that the conducting plastic of the IOM sampling cassette may be replaced with another kind of plastic with similar electrical conductivity, but whose humidity absorption is 30 times lower. A lid, which is weighed with the cassette, was designed so that the potential dust loss from the cassette proper to the commercial transport clip was eliminated. A flow adapter, which simplifies the measurement of the air flow during personal sampling, was designed.     

A collaborative european study of personal inhalable aerosol sampler performance

Following the adoption of new international sampling conventions for inhalable, thoracic and respirable aerosol fractions, a working group of Comité Européen de Normalisation (CEN) drafted a standard for the performance of workplace aerosol sampling instruments. The present study was set up to verify the experimental, statistical and mathematical procedures recommended in the draft performance standard and to check that they could be applied to inhalable aerosol samplers. This was achieved by applying the tests to eight types of personal inhalable aerosol sampler commonly used for workplace monitoring throughout Europe. The study led to recommendations for revising the CEN draft standard, in order to simplify the tests and reduce their cost. However, some further work will be needed to develop simpler test facilities and methods. Several of the samplers tested were found to perform adequately with respect to the inhalable sampling convention, at least over a limited range of typical workplace conditions. In general the samplers were found to perform best in low external wind speeds, which are the test conditions thought to be closest to those normally found in indoor workplaces. The practical implementation of the CEN aerosol sampling conventions requires decisions on which sampling instruments to use, estimation of the likely impact that changing sampling methods could have on apparent exposures, and adjustment where necessary of exposure limit values. The sampler performance data obtained in this project were affected by large experimental errors, but are nevertheless a useful input to decisions on how to incorporate the CEN inhalable sampling convention into regulation, guidance and occupational hygiene practice.     

Exposure levels and determinants of inhalable dust exposure in bakeries

The study's objectives were to measure full-shift exposure to inhalable dust in bakeries and define the determinants of full-shift exposure. Inhalable dust was measured gravimetrically. Ninety-six bakery workers, employed in seven different bakeries, participated in the study. Two side-by-side full-shift inhalable dust samples were obtained from each study participant on a single occasion. Samples were collected on 18 days selected at random. During the entire sampling period, bakers were observed and information on 14 different tasks was recorded at 15 min intervals. Other production characteristics were also recorded for each sampling day. These task and production variables were used in statistical modelling to identify significant predictors of exposure. The mean full-shift inhalable dust exposure was 8.2 mg/m³ (range: 0.1–110 mg/m³). A regression model explained 79% of the variability in exposure. The model indicated that tasks such as weighing, pouring and operating dough-brakers and reversible sheeters increased the exposure, while packing, catching and decorating decreased the exposure. Bread and bun production lines were associated with increased full-shift inhalable dust exposure, while cake production and substitution of dusting with the use of divider oil were associated with decreased exposure. Production tasks and characteristics are strong predictors of personal full-shift exposures to flour dust among bakers; these can be altered to reduce exposure levels.     

Testing a revised inlet for the personal dust monitor

A person-wearable dust monitor that provides nearly real-time, mass-based readings of respirable dust was developed for use in underground coal mines. This personal dust monitor (PDM) combined dust sampling instrumentation with a cap lamp (and battery) into one belt-wearable unit, with the air inlet mounted on the cap lamp. However, obsolescence of belt-carried cap lamp and batteries in coal mining ensued and led end users to request that the cap lamp and battery be removed from the PDM. Removal of these components necessitated the design of a new air inlet to be worn on the miner’s lapel. The revised inlet was tested for dust collection equivalency against the original cap-mounted inlet design. Using calculated inlet respirable fractions and measured dust mass collection, the performance of the two inlets is shown to be similar. The new inlet requires a 1.02 factor for converting dust masses obtained from it to equivalent masses collected from the original inlet.     

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.     

Determinants of inhalable dust exposure in the European carbon black manufacturing industry

A large study to investigate the respiratory health effects of occupational exposure to carbon black in the European carbon black manufacturing industry commenced in 1987. During the study, a large amount of personal occupational exposure data was collected. This article describes the empirical models used to study the determinants of inhalable dust exposure, using data from 16 factories collected in the third and last cross-sectional phase of this study. Information on activities during the measurements was collected using short job category-specific questionnaires. In addition, questionnaires were completed by factory representatives on the implementation of control measures and changes in production process since the first cross-sectional phase. Mixed effects analyses of variance models were used to identify determinants of exposure, while taking into account the within- and between-worker (random) variance components. The results of these models show that, for any job category, factory is a strong predictor of exposure in this industry. These differences could not be explained entirely by factors such as age of the factory or the control measures implemented since the first phase of the study. Surprisingly, implementation of local exhaust ventilation systems had an effect that was counterintuitive; for example, in warehouses where local exhaust ventilation systems had been implemented, higher dust exposure levels were found compared to those where such control measures had not been installed since the first cross-sectional survey. Season appeared to have some effect on exposure for some job titles, with generally relatively low exposures being found in the summer. Finally, a number of activities were identified that caused higher levels of dust exposure, most notably "changing of filters" and "clean-up of carbon black spills."     

可吸入大气颗粒物污染与居民每日死亡关系的Meta分析

目的综合分析国内外可吸入大气颗粒物（PM10）短期暴露与人群死亡关系的流行病学资料,以获取大气PM10污染与居民死亡的暴露-反应关系。方法在计算机联机检索文献和手工检索的基础上,对近十年来发表的相关研究文献采用meta分析的方法进行综合评价,并检验、校正可能存在的发表偏倚,从而准确、定量地确定PM10污染与居民死亡的暴露-反应关系。结果建立了居民短期接触大气PM10污染的暴露一反应关系,即在未考虑发表偏倚的情况下,大气中PM10每增加1130μg／m3,居民死亡的相对危险度增加3．87％（95％CI：2．84％～5．02％）,在校正了发表偏倚后大气中PM10每增加100μg／m3,死亡的相对危险度增加下降为1．41％（95％CI：0．30％-2．43％）,与考虑偏倚前相比下降了63．6％。结论本研究建立的暴露-反应关系较早注意到发表偏倚的影响,具有一定的代表性与科学性,可用于大气颗粒物暴露健康危险度评价工作参考,为制定相关环境决策提供科学依据。     

Evaluation of personal inhalable aerosol samplers with different filters for use during anthrax responses

Risk of inhalation exposure to viable Bacillus anthracis (B. anthracis) spores has primarily been assessed using short-term, stationary sampling methods which may not accurately characterize the concentration of inhalable-sized spores reaching a person's breathing zone. While a variety of aerosol sampling methods have been utilized during previous anthrax responses, no consensus has yet been established for personal air sampling. The goal of this study was to determine the best sampler-filter combination(s) for the collection and extraction of B. anthracis spores. The study was designed to (1) evaluate the performance of four filter types (one mixed cellulose ester, MCE (pore size = 3 µm), two polytetrafluoroethylene, PTFE (1 and 3 µm), and one polycarbonate, PC (3 µm)); and (2) evaluate the best performing filters in two commercially available inhalable aerosol samplers (IOM and Button). Bacillus thuringiensis kurstaki [Bt(k)], a simulant for B. anthracis, served as the aerosol challenge. The filters were assessed based on criteria such as ability to maintain low pressure drop over an extended sampling period, filter integrity under various environmental conditions, spore collection and extraction efficiencies, ease of loading and unloading the filters into the samplers, cost, and availability. Three of the four tested collection filters—except MCE—were found suitable for efficient collection and recovery of Bt(k) spores sampled from dry and humid as well as dusty and clean air environments for up to 8 hr. The PC (3 µm) filter was identified as the best performing filter in this study. The PTFE (3 µm) demonstrated a comparable performance, but it is more expensive. Slightly higher concentrations were measured with the IOM inhalable sampler which is the preferred sampler's performance criterion when detecting a highly pathogenic agent with no established “safe” inhalation exposure level. Additional studies are needed to address the effects of environmental conditions and spore concentration. The data obtained in this investigation are crucial for future efforts on the development and optimization of a method for assessing inhalation exposure to B. anthracis.