A comparative field study on dust measurements by different sampling methods with emphasis on estimating factors for recalculation from chinese 'total dust' measurements to respirable dust concentrations

In China, dust samplers were originally designed to collect 'total dust' for a short term during production, which is different from the widely adopted sampling strategy for dust. With the aim to provide the conversion factor from Chinese total dust to US and German respirable dust and to look at the influences on conversion factors from environment, production, and instruments, a comparative field study on the dust concentration measurements by different sampling methods was carried out in the same Chinese industries as in the 1989-1990 study and in some other factories. A supplemental experiment was also conducted in a wind tunnel. Dust concentration was measured with a parallel sampling strategy by using the following samplers: 10-mm nylon cyclone for US respirable dust (AR), FSP-Berufsgenossenschaftliches Institut für Arbeitssicherheit (BIA) cyclone for German respirable dust (GR), and samplers for Chinese total dust (CT). Totally, 1434 samples were collected (269 AR, 198 GR, and 967 CT), from which 429 matched sample pairs (249 pairs of AR/CT, 180 GR/CT) were available to calculate conversion ratios. Industry- and job-based conversion factors are presented in this study. The conversion factor of AR/CT was 0.38 for tungsten mines, 0.19 for copper/iron mines, 0.65 for tin mines, and 0.20 for pottery industry, while the factor of GR/CT was 0.69 for tungsten, 0.37 for copper/iron, and 0.52 for pottery. In the job category, AR/CT factors varied from 0.16 to 0.96 and GR/CT from 0.12 to 0.72. For the industries studied in 1988-1989, the AR/CT and GR/CT factors were 0.29 and 0.45, respectively. Both factors were definitely influenced by production, CT dust concentration, sample gain, and variation of dust concentration. Moreover, the respirable dust concentration by FSP-BIA was significantly higher than that by 10-mm cyclones, 63.27-73.10% more as showed also by the wind tunnel experiment. Meanwhile, the GR/CT ratio was significantly larger than the AR/CT in every industry or job with only few exceptions. The GR/CT estimates should be considered as independent ones. Following these results, there is a need to use 'ideal samplers' (consistent with the internationally accepted respirable fraction) in practice and to assess the existent samplers in order to homogenize the exposure data situation.     

Estimating historical respirable crystalline silica exposures for Chinese pottery workers and iron/copper, tin, and tungsten miners.

Collaborative studies of Chinese workers, using over four decades of dust monitoring data, are being conducted by the National Institute for Occupational Safety and Health (NIOSH) and Tongji Medical University in China. The goal of these projects is to establish exposure-response relationships for the development of diseases such as silicosis or lung cancer in cohorts of pottery and mine workers. It is necessary to convert Chinese dust measurements to respirable silica measurements in order to make results from the Chinese data comparable to other results in the literature.This article describes the development of conversion factors and estimates of historical respirable crystalline silica exposure for Chinese workers. Ambient total dust concentrations (n>17000) and crystalline silica concentrations (n=347) in bulk dust were first gathered from historical industrial hygiene records. Analysis of the silica content in historical bulk samples revealed no trend from 1950 up to the present. During 1988-1989, side-by-side airborne dust samples (n=143 pairs) were collected using nylon cyclones and traditional Chinese samplers in 20 metal mines and nine pottery factories in China. These data were used to establish conversion factors between respirable crystalline silica concentrations and Chinese total dust concentrations. Based on the analysis of the available evidence, conversion factors derived from the 1988-1989 sampling campaign are assumed to apply to other time periods in this paper. The conversion factors were estimated to be 0.0143 for iron/copper, 0.0355 for pottery factories, 0.0429 for tin mines, and 0.0861 for tungsten mines. Conversion factors for individual facilities within each industry were also calculated. Analysis of variance revealed that mean conversion factors are significantly different among facilities within the iron/copper industry and within the pottery industry. The relative merits of using facility-specific conversion factors, industry-wide conversion factors, or a weighted average of the two are discussed. The exposure matrix of the historical Chinese total dust concentrations was multiplied by these conversion factors to obtain an exposure matrix of historical respirable crystalline silica concentrations.     

3国不同粉尘采样器测定结果的比较

[目的]比较研究3国不同粉尘采样器的测定结果。[方法]采用中国、美国和德国总尘和呼尘采样器在武昌造船厂的清铲和造型车间于呼吸带高度进行平行采样8d,并测定总尘、呼尘浓度。[结果]中国、美国、德国的总尘和呼尘采样器的测定结果具有一定的相关性(P<0.05)。但中国总尘采样器的测定结果与美国、德国的结果有差异(P<0.05);而呼尘间无差异(P>0.05)。[结论]我国呼尘采样测定结果与国外采样器测定结果具有可比性。     

造船厂矽尘总尘与呼尘浓度的关系探讨

为比较中国、美国和德国粉尘采样方法测定的总尘与呼尘浓度比例关系,分析国产与美国、德国产粉尘采样器测定结果的可比性。在某造船厂的铸造车间于呼吸带高度平行采样8 d,测定总尘、呼尘浓度;分别计算总尘与呼尘浓度的比值,分析其影响因素;以方差分析、相关及回归分析对结果进行统计。结果 :(1)采用国产与美国、德国产采样器测得的总尘与呼尘浓度比值进行比较,差异无统计学意义(ANOVA-SNK检验,P>0.05)。(2)国产与美国产粉尘采样器测定的总尘与呼尘比值随着测尘距离增大而增大,但德国产仪器测定结果则反之。(3)总尘与呼尘浓度呈线性相关,只是国产仪器总尘与呼尘相关程度低于德国和美国。提示,国产仪器粉尘采样总尘、呼尘浓度比值与美国及德国的仪器具有可比性。     

Risk of silicosis in cohorts of Chinese tin and tungsten miners, and pottery workers (I): an epidemiological study

BACKGROUND: Epidemiological evaluations of the risk of silicosis in relation to exposure to crystalline silica have raised the question of whether different types of silica dust exposures vary with respect to their ability to cause silicosis. The aim of this study is to compare the risk of silicosis among cohorts of silica dust-exposed Chinese tin miners, tungsten miners, and pottery workers and to assess whether gravimetric measurements of respirable silica dust sufficiently determine the risk of silicosis or whether other factors of exposure may play a significant role. METHODS: Cohorts were selected from 20 Chinese mines and potteries. Inclusion criteria were starting employment after January 1, 1950 and being employed for at least 1 year during 1960-1974 in one of the selected workplaces. Radiological follow-up for silicosis onset was from January 1, 1950 through December 31, 1994. Silicosis was assessed according to the Chinese radiological criteria for diagnosis of pneumoconiosis (as suspect, Stage I, II, or III). Exposure-response relationships were estimated for silicosis of Stage I or higher. Silica dust exposure was estimated in terms of cumulative total dust exposure, calculated from a workplace, job title, and calendar year exposure matrix, and individual occupational histories. Cumulative total dust exposure was converted in two steps into cumulative respirable dust exposure and cumulative respirable silica dust exposure using conversion factors estimated from side-by-side measurements conducted in 1988-89. RESULTS: The male cohorts included 4,028 tin miners, 14,427 tungsten miners, and 4,547 pottery workers who had similar onset of employment and duration of follow-up. For a given exposure level, the risk of silicosis was higher for the tin and tungsten than the pottery workers. CONCLUSION: The observed differences in the risk of silicosis among the three cohorts suggest that silica dust characteristics, in addition to cumulative respirable silica dust exposure, may affect the risk of silicosis.     

A comparison of sampling and analytical methods for assessing occupational exposure to diesel exhaust in a railroad work environment

Methods of assessing occupational exposure to diesel exhaust were evaluated in a railroad work environment. The American Conference of Governmental Industrial Hygienists (ACGIH)-recommended elemental carbon and respirable combustible dust methods of sampling and analysis for assessing diesel exhaust were included in the study. A total of 215 personal and area samples were collected using both size-selective (nylon cyclone and Marple) and non-size-selective samplers. The results demonstrate that the elemental carbon method is suitable for the railroad environment and the respirable combustible dust method is not. All elemental carbon concentrations measured were below the proposed ACGIH Threshold Limit Value (TLV) of 0.15 mg/m3. The concentrations of oxides of nitrogen (nitric oxide and nitrogen dioxide) were also found to be below their respective TLVs. There is no correlation between elemental carbon or respirable combustible dust and the oxides of nitrogen. The elemental carbon as fraction of total carbon is about 13 percent, except for onboard locomotives where it is about 24 percent. Comparison of elemental carbon and respirable combustible dust measurements showed consistent relationships for most sampling locations, with respirable combustible dust concentrations 12 to 53 times higher than the elemental carbon levels.     

Comparison of respirable dust samplers for use in hard rock mines

Five respirable dust size selectors and eleven filter holders were compared, some at two flow rates. These included horizontal elutriators, impactors, metal cyclones and nylon cyclones. The comparisons were carried out both in the laboratory and in mines. The respirable dust on the filters was assessed by weighing, and where relevant, by X-ray diffraction for quartz with the use of a direct-on-filter method. The results obtained showed that the relation between most pairs of samplers could be represented by a straight line through the origin and that the personal samplers collecting more dust--the CAMPEDS impactor and the B.C.I.R.A. cyclone--gave higher reproducibility in the low dust concentrations found in many hard rock mines. The samplers based on the nylon cyclone were less suitable for hard rock mines containing a substantial proportion of quartz, though satisfactory in coal mines with their higher dust control standards.     

Risk of silicosis in cohorts of Chinese tin and tungsten miners and pottery workers (II): Workplace-specific silica particle surface composition

BACKGROUND: It is hypothesized that surface occlusion by alumino-silicate affects the toxic activity of silica particles in respirable dust. In conjunction with an epidemiological investigation of silicosis disease risk in Chinese tin and tungsten mine and pottery workplaces, we analyzed respirable silica dusts using a multiple-voltage scanning electron microscopy-energy dispersive X-ray spectroscopy (MVSEM-EDS). METHODS: Forty-seven samples of respirable sized dust were collected on filters from 13 worksites and were analyzed by MVSEM-EDS using high (20 keV) and low (5 keV) electron beam accelerating voltages. Changes in the silicon-to-aluminum X-ray line intensity ratio between the two voltages are compared particle-by-particle with the 90th percentile value of the same measurements for a ground glass homogeneous control sample. This provides an index that distinguishes a silica particle that is homogeneously aluminum-contaminated from a clay-coated silica particle. RESULTS: The average sample percentages of respirable-sized silica particles alumino-silicate occlusion were: 45% for potteries, 18% for tin mines, and 13% for tungsten mines. The difference between the pottery and the metal mine worksites accounted for one third of an overall chi-square statistic for differences in change in measured silicon fraction between the samples. CONCLUSION: The companion epidemiological study found lower silicosis risk per unit cumulative respirable silica dust exposure for pottery workers compared to metal miners. Using these surface analysis results resolves differences in risk when exposure is normalized to cumulative respirable surface-available silica dust.     

Estimating historical exposure to silica among mine and pottery workers in the people's Republic of China

A quantitative retrospective exposure assessment method was developed for use in a nested case-control study of lung cancer among mine and pottery workers exposed to silica dust in the People's Republic of China. Exposure assessment was carried out in 20 mines (10 tungsten, 6 iron/copper, and 4 tin) and nine pottery factories. A job title dictionary was developed and used in both the collection of historical exposure information and work histories of 1,668 (316 cases and 1,352 controls) study subjects. Several data abstraction forms were developed to collect historical and current exposure information and employees' work histories, starting in 1950. A retrospective exposure matrix was developed on the basis of facility/job title/calendar year combinations using available historical exposure information and current exposure profiles. Information on the amount of respirable, thoracic, and free silica content in total dust was used in estimating exposure to silica. Starting in 1950, 6,805 historical estimates had been carried out for 14 calendar-year periods. We estimated the average total dust concentration to be 9 mg/M³, with a range from 28 mg/M³ in earlier years to 3 mg/M³ in recent years. Several exposure indices [such as cumulative dust, average dust, cumulative respirable (<5 μ in particle size) and thoracic (<10 μ in particle size) silica dust, average respirable and thoracic silica dust, exposure-weighted duration, and the highest/longest exposure] were calculated for individuals by merging work history and historical exposure matrix for each study subject. We developed these various measures of exposure to allow investigators to compare and contrast different indices of historical exposure to silica. © 1993 Wiley-Liss, Inc.

1 This article is a US Government work and, as such, is in the public domain in the United States of America.

     

Occupational exposure to cotton dust in cottonseed oil mills

Air samples were collected at breathing height in the hulling-separation department of a modern cottonseed oil mill in Uzbekistan. The average elutriated mass concentration measured by standard cotton dust samplers was 4.6 mg/m3, much lower than the average total dust concentration measured by stationary personal samplers, 12.49 mg/m3, and by personal samplers attached to workers, 14.53 mg/m3. Differences in readings among the vertical elutriators, stationary personal samplers, and roving personal samplers are attributed to the distinct sampling nature and dynamics of these samplers. The data suggest that most of the dust consisted of particles larger than 15 microm, the particle size cutoff of the vertical elutriator. Differences in readings among stationary and roving personal samplers are statistically significant, presumably representing biased sampling by the roving personal samplers of regions characterized by high dust concentration (due to machines malfunctioning), the nonstatic nature of the sampling, and the interaction between the sampler and the worker (the personal cloud). Cotton dust concentrations in the hulling-separation room were nonuniform, peaking in front of and between the huller-separator pairs. The high total mass readings show that workers were exposed to very high levels of nonthoracic airborne dust, which upon inhalation tends to deposit in the extrathoracic airways. The high elutriated mass concentrations suggest that workers were exposed to respirable cotton dust at levels higher than 1 mg/m3 mean concentration, the current Occupational Safety and Health Administration (OSHA) Permissible Exposure Limit (PEL) for cotton dust. Regressions between dust concentrations measured by stationary vertical elutriators and by personal samplers attached to workers serve for estimating the potential occupational exposure to cotton dust of workers in the hulling-separation room.     

瓷厂和钨矿生产性粉尘生物学效应的研究

目的 通过体外细胞实验测定瓷厂和钨矿作业点生产性粉尘的毒性等生物学效应,为评价粉尘的危害作用提供依据.方法 以豚鼠的肺泡巨噬细胞(AM)为作用细胞,以标准石英作为对照,应用肺泡灌洗的方法获得AM后,加入15、30、60、120μg/106个细胞浓度标准石英、瓷厂及钨矿作业点的呼吸性粉尘颗粒培养,测定细胞的乳酸脱氢酶(LDH)活力、细胞活力(MTT)、活性氧释放量和肿瘤坏死因子-α(TNF-α)的释放量.结果 瓷厂和钨矿的生产性粉尘均能诱导豚鼠AM培养液中LDH活力升高,诱导豚鼠AM释放活性氧和TNF-α量升高,并随粉尘浓度升高呈现明显的剂量一反应关系.瓷厂和钨矿粉尘与豚鼠AM共培养后导致AM活力下降,随着生产性粉尘的浓度增加而降低.钨矿粉尘引起LDH活力升高以及诱导豚鼠AM释放TNF-α能力强于瓷厂粉尘,在120μg/106个细胞浓度组,赣州钨矿粉尘诱导的TNF-α水平为(5.2±2.0)ng/ml,景德镇瓷厂粉尘诱导的TNF-α水平为(3.3±1.6)ng/ml,均高于标准石英(2.8±0.5)ng/ml.与钨矿尘肺患病和死亡率均高于瓷厂相印证.结论 不同来源的生产性粉尘具有不同的生物学效应结果,实验测定粉尘的生物学效应为区分生产性粉尘危害作用提供了基础数据.     

Field performance of the RespiCon for size-selective sampling of industrial wood processing dust

The RespiCon sampler is a multistage virtual impactor that simultaneously collects the ISO/CEN/ACGIH size fractions of inhalable, thoracic, and respirable particulate matter. The field performance of the device for measurement of industrial wood processing dust was evaluated against reference size-selective samplers: the IOM sampler (inhalable dust), the GK 2.69 cyclone (thoracic dust), and the SKC aluminum cyclone (respirable dust). Seventy-one sets of area samples were collected from 10 wood processing plants, with the samplers mounted either in the free-field or on a two-dimensional bluff body. The geometric mean (range) dust levels across all plants measured by the reference samplers were: inhalable, 1.35 mg/ m3 (0.11-11.06); thoracic, 0.31 mg/m3 (0.05-1.38); and respirable, 0.10 mg/m3 (0.02-0.54). In comparing the RespiCon with the reference samplers, there was no significant difference between sampling in the free-field versus bluff-body modes. For inhalable dust, there was no significant difference between the RespiCon and the IOM sampler after applying a correction factor of 1.5 to the extrathoracic data obtained from the RespiCon. Without the correction factor, the RespiCon undersample inhalable dust by an average of 23%. For thoracic dust, the RespiCon was shown to oversample the extrathoracic dust fraction resulting in an overall error of 48%. A simple correction based on the inhalable and thoracic dust levels reported by the RespiCon is proposed. For respirable dust, there was a significant difference between the RespiCon and the SKC cyclone, but the data were equivocal due to imprecision in measurement of the low respirable dust concentrations encountered and the likelihood of bias in the reference sampler. Overall, the RespiCon sampler appears to be a suitable size-selective sampling device for industrial wood processing dust, although adjustments should be made to the inhalable and thoracic dust results.     

Chamber for testing asbestos-containing products: validation and testing of a re-created chrysotile-containing joint compound

Joint compound products containing chrysotile asbestos were commonly used for building construction from the late 1940s through the mid-1970s. Few relevant data exist to support reconstructing historical worker exposures to fibers generated by working with this material. Therefore, we re-created 1960s-era chrysotile-containing joint compound (JCC) and compared its characteristics to a current-day asbestos-free joint compound (JCN). Validation studies showed that a bench-scale chamber with controlled flow dynamics, designed to quantify particulate emissions from joint compound products, provided precise and reliable measurements of generated airborne dust mass, chrysotile fiber concentrations, and corresponding activity-specific emission rates. Subsequent chamber studies characterized fibers counted by phase contrast microscopy (PCM) per mass of respirable dusts and total suspended particulate dusts (total dusts), generated during JCC sanding or sweeping, as well as corresponding dust emission rates for JCC and JCN, and the ratio of total to respirable dust mass for JCN. From these data we estimated factors, F(CH-rd) and F(CH-td) (in units of f cm(-3) per mg m(-3)), by which respirable JCN dust mass concentrations collected during construction use can be converted to corresponding airborne PCM fiber concentrations generated by sanding or sweeping JCC. For sanding, median values (95% confidence limits) of F(CH-rd) and F(CH-td) were estimated to be 0.044 (0.039-0.050) and 0.212 (0.115-0.390) f cm(-3) per mg m(-3), respectively. The F(CH-td) to F(CH-rd) ratio indicates that approximately five times as many airborne PCM fibers are anticipated per unit air volume sampled when JCC dust is collected on cassettes (as done historically), than when respirable JCC dust is collected on cyclones. As the sizes of individual fibers collected appear to be primarily respirable, this difference may be a sampling artifact and suggests caution in interpreting historical fiber concentration measures made using cassettes during work with JCC-like materials. F(CH-rd) can be used with published and newly generated field measurements of respirable dust mass concentrations associated with the use of JCN or equivalent JCN materials to better characterize historical worker exposures to PCM fibers from use of JCC or equivalent JCCs. The experimental process described also can be used to develop conversion factors for other combinations of modern-day asbestos-free and historical chrysotile-containing products.     

Estimation of respirable dust exposure among coal miners in South Africa

The use of retrospective occupational hygiene data for epidemiologic studies is useful in determining exposure-outcome relationships, but the potential for exposure misclassification is high. Although dust sampling in the South African coal industry has been a legal requirement for several decades, these historical data are not readily adequate for estimating past exposures. This study describes the respirable coal mine dust levels in three South African coal mines over time. Each of the participating mining operations had well-documented dust sampling information that was used to describe historical trends in dust exposure. Investigator-collected personal dust samples were taken using standardized techniques from the face, backbye (underground jobs not at the coal face), and surface from 50 miners at each mine, repeated over three sampling cycles. Job histories and exposure information was obtained from a sample of 684 current miners and 188 ex-miners. Linear models were developed to estimate the exposure levels associated with work in each mine, exposure zone, and over time using a combination of operator-collected historical data and investigator-collected samples. The estimated levels were then combined with work history information to calculate cumulative exposure metrics for the miner cohort. The mean historical and investigator-collected respirable dust levels were within international norms and South African standards. Silica content of the dust samples was also below the 5% regulatory action level. Mean respirable dust concentrations at the face, based on investigator-collected samples, were 0.9 mg/m(3), 1.3 mg/m(3), and 1.9 mg/m(3) at Mines 1, 2, and 3, respectively. The operator-collected samples showed considerable variability across exposure zones, mines, and time, with the annual means at the face ranging from 0.4 mg/m(3) to 2.9 mg/m(3). Statistically significant findings were found between operator- and investigator-collected dust samples. Model-based arithmetic mean dust estimates at the face were 1.2 mg/m(3), 2.0 mg/m(3), and 0.9 mg/m(3) for Mines 1, 2, and 3, respectively. Using these levels, the mean cumulative exposure for the cohort was 56.8 mg-years/m(3). Current miners had a mean cumulative exposure of 66.5 mg-years/m(3), compared with ex-miners of 26.8 mg-years/m(3). Improvements in dust management or the use of different sampling equipment could account for the significant differences seen between operator- and investigator-collected data. Regression modeling for estimating mean dust levels over time using combined historical and investigator-collected data seems a reasonable method and useful in constructing models to describe cumulative exposures in a cohort of current and ex-miners.     

瓷厂及钨矿生产性粉尘对血管内皮细胞的损伤效应

目的 评价瓷厂和钨矿生产性粉尘对血管内皮细胞的直接损伤作用,探讨粉尘引发心血管疾病的机制.方法 以人脐静脉内皮细胞(HUVEC)株HUV-EC-C为作用细胞,以瓷厂、钨矿作业点收集的生产性粉尘为实验粉尘,以中国标准石英为对照,将粉尘配制成25、50、100、200、400μg/ml浓度与HUVEC共培养24 h,测定细胞乳酸脱氢酶(LDH)活力、细胞的活力噻唑蓝(MTT)、一氧化氮(NO)和肿瘤坏死因子-α(TNF-α)的释放量.结果 瓷厂和钨矿作业点的生产性粉尘均能使HUVEC细胞培养液中LDH活力升高,释放NO及TNF-α水平升高,并随粉尘浓度升高呈现明确的剂量-反应关系.瓷厂和钨矿作业点生产性粉尘均能导致HUVEC细胞活力下降,呈剂量-反应关系.石英粉尘诱导HUVEC培养液中LDH活力升高的能力明显高于瓷厂和钨矿的生产性粉尘,差异有统计学意义(P＜0.05).瓷厂和钨矿生产性粉尘诱导HUVEC细胞活力下降及释放NO的能力相近且与标准石英相当.在较低剂量组(25、50、100μg/ml)时,瓷厂和钨矿生产性粉尘诱导TNF-α的释放量与标准石英相当,差异无统计学意义(P＞0.05),而在较高剂量组(200、400 μg/ml)时,标准石英诱导TNF-α的释放量明显高于瓷厂和钨矿生产性粉尘,差异有统计学意义(P＜0.05).结论 不同来源的生产性粉尘及标准石英均能损伤血管内皮细胞,诱导TNF-α释放,引起不同程度的生物学效应.     

瓷厂与锡矿及钨矿石英粉尘表面铝硅酸盐包裹的测定和分析

目的 探讨石英粉尘表面铝硅酸盐包裹的测定方法和包裹对粉尘致病作用的影响.方法 应用呼吸性粉尘采样器以2 L/min采集江西钨矿、瓷厂和广西锡矿粉尘,用扫描电镜-能散X线分光计（SEM-EDS）以5 keV和20 keV电压照射测定呼吸性粉尘颗粒中各元素成分的含量,计算不同电子伏特照射下粉尘颗粒中硅与铝的比值.结果 7个瓷厂、3个锡矿和3个钨矿的47个粉尘样本共计3 982个粉尘颗粒,瓷厂样本的89%（24/27）与锡矿样本的27%（3/11）和钨矿样本的56%（5/9）存在明确的铝硅酸盐包裹,与对照样本比较,差异有统计学意义（P＜0.01）.瓷厂粉尘颗粒的45%、锡矿的18%和钨矿的13%存在表面铝硅酸盐包裹.瓷厂粉尘与钨矿和锡矿粉尘表面铝硅酸盐含量的差异有统计学意义（P＜0.01）,高铝硅酸盐含量的粉尘颗粒在瓷厂、锡矿和钨矿样本中的比率分别为22%、7%和10%.结论 瓷厂工作场所粉尘颗粒表面夹杂铝硅酸盐含量高于钨矿和锡矿的粉尘,粉尘颗粒表面成分的分析对解释不同厂矿尘肺发病的差异有一定作用.     

Quartz measurement in coal dust with high-flow rate samplers: laboratory study

A laboratory study was performed to measure quartz in coal dust using high-flow rate samplers (CIP10-R, GK2.69 cyclone, and FSP10 cyclone) and low-flow rate samplers [10-mm nylon and Higgins-Dewell type (BGI4L) cyclones] and to determine whether an increased mass collection from high-flow rate samplers would affect the subsequent quartz measurement by Fourier transform infrared (FTIR) and X-ray diffraction (XRD) analytical procedures. Two different sizes of coal dusts, mass median aerodynamic diameter 4.48 μm (Coal Dust A) and 2.33 μm (Coal Dust B), were aerosolized in a calm air chamber. The mass of coal dust collected by the samplers was measured gravimetrically, while the mass of quartz collected by the samplers was determined by FTIR (NIOSH Manual of Analytical Method 7603) and XRD (NIOSH Manual of Analytical Method 7500) after one of two different indirect preparations. Comparisons between high-flow rate samplers and low-flow rate samplers were made by calculating mass concentration ratios of coal dusts, net mass ratios of coal dusts, and quartz net mass. Mass concentrations of coal dust from the FSP10 cyclone were significantly higher than those from other samplers and mass concentrations of coal dust from 10-mm nylon cyclone were significantly lower than those from other samplers, while the CIP10-R, GK2.69, and BGI4L samplers did not show significant difference in the comparison of mass concentration of coal dusts. The BGI4L cyclone showed larger mass concentration of ～9% compared to the 10-mm nylon cyclone. All cyclones provided dust mass concentrations that can be used in complying with the International Standard Organization standard for the determination of respirable dust concentration. The amount of coal dust collected from the high-flow rate samplers was found to be higher with a factor of 2-8 compared to the low-flow rate samplers but not in direct proportion of increased flow rates. The high-flow rate samplers collected more quartz compared to low-flow rate samplers in the range of 2-10. There was no significant difference between the per cent (%) quartz in coal dust between the FTIR and XRD analyses. The findings of this study indicated that the increased mass of quartz collected with high-flow rate samplers would provide precise analytical results (i.e. significantly above the limit of detection and/or limit of quantification) compared to the mass collected with low-flow rate samplers, especially in environments with low concentrations of quartz or where short sampling times are desired.     

Field trials of an electret-based passive dust sampler in metal-processing industries

A prototype passive dust sampler using an electret to capture dust particles has been designed on the basis of previous laboratory investigations. The device weighs 15 g whereas conventional samplers, which require a pump and a battery, can weigh more than 1 kg. The electret used in the sampler is the same size as a standard sampling filter and can, to a large extent, be analysed in the same way, though sample weights tend to be small. The device has potential as both a static sampler and a personal sampler. Personal samplers have been assessed by field trials involving a number of volunteers, each wearing a passive sampler and one or more conventional samplers. The industries chosen for the trials were a hard-metal factory, platinum processing works and iron foundries, five factories in all being included in the tests. Correlations between the results of the passive samplers and those obtained using conventional inhalable dust samplers were good in four cases. Quantitative estimates of dust concentration require the electrical mobility of the dust to be known; and values were consistently high when scaled with measurements of aerosol electrical mobility made on the same occasion using a miniaturized electret device. In the instance where the passive sampler data could be compared with respirable dust samples the correlation was not particularly good.     

Change of exposure response over time and long-term risk of silicosis among a cohort of Chinese pottery workers

An analysis was conducted on a cohort of Chinese pottery workers to estimate the exposure-response relationship between respirable crystalline silica dust exposure and the incidence of radiographically diagnosed silicosis, and to estimate the long-term risk of developing silicosis until the age of 65. The cohort comprised 3,250 employees with a median follow-up duration of around 37 years. Incident cases of silicosis were identified via silicosis registries (Chinese X-ray stage I, similar to International Labor Organisation classification scheme profusion category 1/1). Individual exposure to respirable crystalline silica dust was estimated based on over 100,000 historical dust measurements. The association between dust exposure, incidence and long-time risk of silicosis was quantified by Poisson regression analysis adjusted for age and smoking. The risk of silicosis depended not only on the cumulative respirable crystalline silica dust exposures, but also on the time-dependent respirable crystalline silica dust exposure pattern (long-term average concentration, highest annual concentration ever experienced and time since first exposure). A long-term "excess" risk of silicosis of approximately 1.5/1,000 was estimated among workers with all annual respirable crystalline silica dust concentration estimates less than 0.1 mg/m(3), using the German measurement strategy. This study indicates the importance of proper consideration of exposure information in risk quantification in epidemiological studies.     

Lung cancer risk, silica exposure, and silicosis in Chinese mines and pottery factories: the modifying role of other workplace lung carcinogens.

BACKGROUND: Aims of our study were to explore whether and to what extent exposure to other lung carcinogens, or staging and clinical features of silicosis modify or confound the association between silica and lung cancer. METHODS: We used data from a nested case-control study, conducted in the late 1980s in 29 Chinese mines and potteries (10 tungsten mines, 6 copper and iron mines, 4 tin mines, 8 pottery factories, and 1 clay mine), that included 316 lung cancer cases and 1,356 controls, matched by decade of birth and facility type. The previous analysis of these data presented results by type of mine or factory. RESULTS: In our study, pooling all 29 Chinese work sites, lung cancer risk showed a modest association with silica exposure. Risk did not vary after excluding subjects with silicosis or adjusting the risk estimates by radiological staging of silicosis. Strong correlation among exposures prevented a detailed evaluation of the role of individual exposures. However, lung cancer risk was for the most part absent when concomitant exposure to other workplace lung carcinogens, such as polycyclic aromatic hydrocarbons (PAHs), nickel or radon-daughters, was considered. The cross classification of lung cancer risk by categories of exposure to respirable silica and total respirable dust did not show an independent effect of total respirable dust. Silicosis showed a modest association with lung cancer, which did not vary by severity of radiological staging, or by radiological evidence of disease progression, or by level of silica exposure. However, among silicotic subjects, lung cancer risk was significantly elevated only when exposure to cadmium and PAH had occurred. CONCLUSIONS: Our results suggest that, among silica-exposed Chinese workers, numerous occupational and non-occupational risk factors interact in a complex fashion to modify lung cancer risk. Future epidemiological studies on silica and lung cancer should incorporate detailed information on exposure to other workplace lung carcinogens, total respirable dust, and on surface size and age of silica particles to understand whether and to what extent they affect the carcinogenic potential of silica.