A nested case-control study of lung cancer among silica exposed workers in China.

In an attempt to assess whether silica induces lung cancer, a nested case-control study of 316 male lung cancer cases and 1352 controls was carried out among pottery workers and tungsten, copper-iron, and tin miners from five provinces in south central China. Exposure to dust and silica for each study subject was evaluated quantitatively by cumulative exposure measures based on historical industrial hygiene records. Measurements on confounders such as inorganic arsenic, polycyclic aromatic hydrocarbons (PAHs), and radon were also collected from the worksites. Information on cigarette smoking was obtained by interviews of the subjects or their next of kin. A significant trend of increasing risk of lung cancer with exposure to silica was found for tin miners, but not for miners working in tungsten or copper-iron mines. Concomitant and highly correlated exposures to arsenic and PAHs among tin miners were also found. Risk of lung cancer among pottery workers was related to exposure to silica, although the dose-response gradient was not significant. Risks of lung cancer were significantly increased among silicotic subjects in iron-copper and tin mines, but not in pottery factories or tungsten mines. The results of this study provide only limited support for an aetiological association between silica and lung cancer.     

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.     

Effects of work related confounders on the association between silica exposure and lung cancer: a nested case-control study among Chinese miners and pottery workers

Objective The role of silica in the causation of lung cancer is an ongoing debate. In order to explore whether observed association between silica exposure and lung cancer is confounded by exposure to other occupational carcinogens, we updated a previously nested case-control study among a cohort of male workers in 29 Chinese mines and factories on the basis of an extended follow-up. Methods Five hundred and eleven lung cancer cases and 1,879 matched controls were selected. Exposure to respirable silica as well as relevant occupational confounders were quantitatively assessed based on historical industrial hygiene data. The relationship between exposure to silica and lung cancer was analyzed by conditional logistic regression analysis adjusted for exposure to arsenic, polycyclic aromatic hydrocarbons (PAHs), radon, and smoking. Results In a crude analysis adjusted for smoking only, a significant trend of increasing risk of lung cancer with exposure to silica was found for tin, iron/copper miners, and pottery workers. But after adjustment for relevant occupational confounders, no relationship between silica and lung cancer can be observed. Instead, there is a significant association between lung cancer mortality and cumulative exposure to inorganic arsenic (OR = 1.86, 95% CI: 1.14, 3.04 for each mg/m³-year increase) and carcinogenic PAHs (OR = 1.35, 95% CI: 1.08, 1.69 for each 100 μg/m³-year increase). Conclusion This analysis does not provide any evidence to show that exposure to silica causes lung cancer in the absence of confounding factors.     

Nested case-control study of lung cancer in four Chinese tin mines

Objectives: To evaluate the relation between occupational dust exposure and lung cancer in tin mines. This is an update of a previous study of miners with high exposure to dust at four tin mines in southern China.

Methods: A nested case-control study of 130 male lung cancer cases and 627 controls was initiated from a cohort study of 7855 subjects employed at least 1 year between 1972 and 1974 in four tin mines in China. Three of the tin mines were in Dachang and one was in Limu. Cumulative total exposure to dust and cumulative exposure to arsenic were calculated for each person based on industrial hygiene records. Measurements of arsenic, polycyclic aromatic hydrocarbons (PAHs), and radon in the work sites were also evaluated. Odds ratios (ORs), standard statistic analysis and logistic regression were used for analyses.

Results: Increased risk of lung cancer was related to cumulative exposure to dust, duration of exposure, cumulative exposure to arsenic, and tobacco smoking. The risk ratios for low, medium, and high cumulative exposure to dust were 2.1 (95% confidence interval (95% CI) 1.1 to 3.8), 1.7 (95% CI 0.9 to 3.1), and 2.8 (95% CI 1.6 to 5.0) respectively after adjustment for smoking. The risk for lung cancer among workers with short, medium, and long exposure to dust were 1.9 (95% CI 1.0 to 3.5), 2.3 (95% CI 1.3 to 4.1), and 2.3 (95% CI 1.2 to 4.2) respectively after adjusting for smoking. Several sets of risk factors for lung cancer were compared, and the best predictive model included tobacco smoking (OR=1.6, 95% CI 1.1 to 2.4) and cumulative exposure to arsenic (ORs for different groups from low to high exposure were 2.1 (95% CI 1.1 to 3.9); 2.1 (95% CI 1.1 to 3.9); 1.8 (95% CI 1.0 to 3.6); and 3.6 (95% CI 1.8 5 to 7.3)). No excess of lung cancer was found among silicotic subjects in the Limu tin mine although there was a high prevelance of silicosis. Exposures to radon were low in the four tin mines and no carcinogenic PAHs were detected.

Conclusions: These findings provide little support for the hypothesis that respirable crystalline silica induces lung cancer. Ore dust in work sites acts as a carrier, the exposure to arsenic and tobacco smoking play a more important part in carcinogenesis of lung cancer in tin miners. Silicosis seems not to be related to the increased risk of lung cancer.

     

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.     

Relation of arsenic exposure to lung cancer among tin miners in Yunnan Province, China.

The relation of mining and smelting exposure to arsenic and lung cancer was studied among tin miners in Yunnan Province in the People's Republic of China. Interviews were conducted in 1985 with 107 living tin miners who had lung cancer and an equal number of age matched controls from among tin miners without lung cancer to obtain information on risk factors for lung cancer including detailed history of employment and tobacco use. Occupational history was combined with industrial hygiene data to estimate cumulative arsenic exposure. Similar methods were also used to estimate radon exposure for simultaneous evaluation in this analysis. The results indicate that subjects in the highest quarter of cumulative arsenic exposure have a relative risk of 22.6 compared with subjects without exposure after adjusting for tobacco and radon exposure, and a positive dose response relation was observed. Simultaneous evaluation of arsenic and tobacco exposure indicates a greater risk for arsenic, whereas simultaneous assessment of arsenic and radon exposure suggests radon to be the greater risk. There is no evidence of synergism between arsenic and tobacco exposure. Among arsenic exposed individuals, cases of lung cancer have longer duration but lower average intensity of arsenic exposure than controls, indicating that duration of exposure to arsenic may be more important than intensity in the aetiology of lung cancer. Finally, risk of lung cancer among workers exposed to arsenic only in mining is only slightly less than for miners whose exposure to arsenic was limited to smelting, although risks are highest when workers were exposed to both mining and smelting.     

金属矿山和瓷厂的粉尘及有害因素

本文为研究金属矿工和瓷厂作业工人的肺癌病因,对4类金属矿(钨、锡,铜、铁)和9个瓷厂作业环境的粉尘,30种化学元素、放射性氡子体、γ射线和17种多环芳烃(PAH)等有害因素作了现场测定,并对各厂矿的历史测尘资料进行了整理分析。结果发现粉尘浓度早期以钨矿为最高。自70年代开始,钨矿降为最低。但游离SiO_2含量以钨矿最高,瓷厂次之,铁矿最低。瓷厂粉尘分散度比矿尘低。元素结果表明,砷、镉以锡矿最高:铁、镍以铁矿最高,这些被认为致癌物和可疑致癌物元素,可能成为矿工的致癌因素之一。井下氡子体仅铜矿超标,故铜矿工肺癌高发可能受氡暴露的影响。PAH 以井下使用柴油铲运机的锡矿、铜矿、铁矿为最高。但因其接触时间不长,其致癌作用还需进一步观察。     

锡矿作业工人粉尘接触和队列死因分析

[目的]评价混合性粉尘接触对锡矿作业工人健康的影响及累积粉尘接触与主要引起工人死亡疾病的关系。[方法]建立广西4个锡矿1972~1974年在册且工作一年以上工人的研究队列,以全国城市居民年龄别死亡率为参照,标化死亡比(SMR)作为统计指标。[结果]队列共计7837人,至1994年底,共计165156.7人年,死亡1094人。影响锡矿工人健康的主要疾病按累积死亡率从高到低排序分别是:肿瘤(5.3%)、脑血管疾病(2.4%)、心血管系统疾病(1.9%)和呼吸系统疾病(1.7%),这4种疾病引起的死亡占总数的80.7%,恶性肿瘤以肺癌和肝癌最多,分别占总死亡数的12.6%和10.9%。全死因标化死亡比(SMR=0.94)接近全国平均水平,而鼻咽癌、肝癌、肺癌、白血病、尘肺和脑血管疾病的SMR较高,分别为3.41、1.97、2.49、2.31、33.89和1.15。队列中接尘工人4629名,研究发现矿尘接触导致死亡率上升,与粉尘接触存在明确剂量反应关系的疾病主要是尘肺、肺癌和肺结核。[结论]混合性粉尘明显影响工人健康,累积粉尘接触与肺癌死亡存在剂量-反应关系,可能与粉尘中高含量的砷和游离二氧化硅有关。     

Exposures to silica mixed dust and cohort mortality study in tin mines: exposure-response analysis and risk assessment of lung cancer

BACKGROUND: Mineral dusts that contain crystalline silica have been associated directly or indirectly with the development of pneumoconiosis or silicosis, non-malignant respiratory diseases, lung cancer, and other diseases. The health impacts on workers with silica mixed dust exposure in tin mines and dose-response relationships between cumulative dust exposure and the mortality from lung cancer are investigated. METHODS: A cohort of 7,837 workers registered in the employment records in 4 Chinese tin mines between 1972 and 1974 was identified for this study and the mortality follow-up was traced through 1994. Of the cohort, the cause of death was ascertained for 1,061 (97%) of the 1,094 deceased workers. Standardized mortality ratios (SMRs) were calculated for all workers, non-exposed workers, and dust-exposed workers with different exposure levels, silicotics, and non-silicotics based on Chinese national rates. RESULTS: The mortality from all causes in four tin mines was nearly the same as the national mortality. Malignant neoplasm, cerebrovascular disease, and cardiovascular disease accounted for 68.6% of all deaths. Mortality excess from lung cancer, liver cancer, all malignant diseases, and non-malignant respiratory diseases was observed among dust-exposed workers; a 50-fold excess of pneumoconiosis was observed. There was an upward trend for SMRs of lung cancer was noted from no exposure to low, medium, and high exposure levels (SMRs=1.29, 2.65, 2.66, 3.33). The shape of the exposure-response curve for risk of lung cancer at high exposure levels was inconsistent in these four mines. CONCLUSIONS: The findings indicated a positive dose-response relation between exposure to cumulative dust and the mortality of lung cancer. High arsenic content in dust particles, together with crystalline silica, may play an important role in causing increased mortality from lung cancer.     

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.     

不同类型厂矿接尘工人肺癌病因学研究──矽尘或矽肺与肺癌的关系

为评价游离二氧化硅（简称矽尘或ＳｉＯ２）是否致肺癌？矽肺是否是肺癌前变基础？选择四类接尘厂矿进行队列和队列内病例对照研究。队列对象６８２８５人。有矽肺６４８７例，肺癌３３０例（男３１９，女１１），配对照１３５８例。根据厂矿历年工业卫生记录和近期对已知致癌物监测结果，定量评估了每个对象的接尘水平及每个病例对照的累积接触量。研究对象追访到１９８９年底，死亡６１９２人。与全国居民死亡平均数计算的期望值近似。全死因中癌症是第一死因，但全癌低于国家居民死亡率。分析结果说明：（１）矽尘单独存在时不是肺致癌剂。肺癌不超高，与接尘关系不明显；（２）在６４８７名矽肺队列中，肺癌相对危险度仅比非矽肺高０．２２倍，主要反应在铜铁矿工人中（Ｒ＝２．２），而矽肺患病率最严重的钨矿工人，其肺癌危险度反而随接尘水平上升而下降，再则肺癌死亡率与矽肺期别不呈正比；形态学上观察也不支持肺癌病变与矽肺纤维化病变相关。本研究结果难以支持矽尘或矽肺与肺癌病因学相关的假说。     

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.     

Relation of radon exposure and tobacco use to lung cancer among tin miners in Yunnan Province, China

We studied the relation of radon exposure and tobacco use to lung cancer among tin miners in Yunnan Province in the People's Republic of China. Interviews were conducted in 1985 with 107 living tin miners with lung cancer and an equal number of age-matched controls from among tin miners without lung cancer to obtain information on lung cancer risk factors including a detailed history of employment and tobacco use. Occupational history was combined with extensive industrial hygiene data to estimate cumulative working level months (WLM) of radon daughter exposure. Similar data were also used to estimate arsenic exposure for control in the analysis. Results indicate an increased risk of lung cancer for water pipe smoking, a traditional form of tobacco use practiced in 91% of cases and 85% of controls. Ever use of water pipes was associated with a twofold elevation in risk when compared with tobacco abstainers, and a dose-response relation was observed with increasing categories of pipe-year (dose times duration) usage. Estimated WLM of radon exposure varied from 0 to 1,761 among subjects but averaged 515 in cases versus only 244 in controls. Analyses indicated that the persons in the highest quarter of the radon exposure distribution had an odds ratio (OR) = 9.5 (95% confidence interval = 2.7-33.1) compared to persons without radon exposure after controlling for arsenic exposure and other potential confounders. Examination of duration and rate of radon exposure indicated higher risk associated with long duration as opposed to high rate of exposure. Cross-categorizations of radon exposure and tobacco use suggest greater risk associated with radon exposure than tobacco in these workers.     

肺癌病因研究中接尘量计算的真实性评价

为评价肺癌病例对照研究中接尘剂量估算方法的真实性,对广西锡矿病因研究对象进行了重新计算。广西锡矿队列发现男性肺癌死者１３０例,配对照６２７例。共７５７人。其中接法工人５７２名,发现各期矽肺共２４３例,根据在斩工业卫生监测资料估算所有接尘工人的累积总粉尘接触量,再计算不同接尘水平下矽肺的发病率。结果显示,随接尘水平上升,矽肺发病率升高,两者存在明显的接触剂量反应关系。完全符合矽肺发病特点。从而间接证     

Mortality of a cohort of tin miners 1941-86.

The mortality patterns of United Kingdom tin miners were examined in relation to calendar period and duration of underground work with particular attention to lung cancer and exposure to radon. Subjects were all men who had worked for at least one year between 1941 and 1984 at one of two United Kingdom tin mines and for whom a complete work history could be constructed from mine records. Standardised mortality ratios (SMRs) were calculated using national (England and Wales) rates. The pattern of SMRs in relation to potential explanatory variables was analysed using Poisson regression methods. Mortalities from lung cancer and silicosis (including silicotuberculosis) were significantly raised and showed a significant relation with duration of underground work (mortality from stomach cancer was raised in both underground and surface workers, but not significantly). Excess mortality from silica related disease declined steeply from 35% among workers first exposed before 1920 to 1% among those first exposed after 1950. Thirteen surface workers with known exposure to arsenic had high rates of lung and stomach cancer. The SMR for lung cancer showed a consistent pattern in relation to duration of underground exposure, rising from 83 (observed/expected = 8/9.6) for surface workers (without exposure to arsenic) to 447 (15/3.4) for workers with more than 30 years underground exposure. Examination of the SMR for lung cancer by total underground exposure, age, and time since last exposure gave rise to a model for the expression of risk which depends only on total exposure and time since exposure. The fitted model implies that the effect of exposure to radon in a given year has no effect on risk for 10 years, then rapidly rises to a maximum from which the excess risk then declines, halving every 4.3 years. There were no direct measurements of historic radon levels. A conservative estimate based on measurements taken since 1969 by the National Radiological Protection Board and the Mines and Quarries Inspectorate is that the annual dose to an underground worker was about 10 working level months (WLM). Given this assumption, the risk/exposure slope implied by the present data, and the model fitted to it, was somewhat lower than that given in the fourth Committee on the Biological Effects of Ionisation Radiation (BEIR IV) report (about 40% lower for lifetime exposures). The present data also imply different risks depending on the age at exposure, with relatively higher lifetime risks for exposure at older ages, and relatively lower risks for exposures at younger ages. In conclusion, there was a clear relation between exposure to radon and death from lung cancer. The relative risk of lung cancer due to exposure to radon was not constant in cessation of exposure. The lifetime excess risk of lung cancer implied by these data for 40 years exposure at the current statutory limit of four WLM a year starting at age 20, was about 8% (79 excess deaths per 1000 exposed), assuming average smoking habits among the exposed workers. Control of dust concentrations in the mines has substantially reduced--and may have eliminated--direct mortality from silica related disease.     

Mortality of a cohort of tin miners 1941-86

The mortality patterns of United Kingdom tin miners were examined in relation to calendar period and duration of underground work with particular attention to lung cancer and exposure to radon. Subjects were all men who had worked for at least one year between 1941 and 1984 at one of two United Kingdom tin mines and for whom a complete work history could be constructed from mine records. Standardised mortality ratios (SMRs) were calculated using national (England and Wales) rates. The pattern of SMRs in relation to potential explanatory variables was analysed using Poisson regression methods. Mortalities from lung cancer and silicosis (including silicotuberculosis) were significantly raised and showed a significant relation with duration of underground work (mortality from stomach cancer was raised in both underground and surface workers, but not significantly). Excess mortality from silica related disease declined steeply from 35% among workers first exposed before 1920 to 1% among those first exposed after 1950. Thirteen surface workers with known exposure to arsenic had high rates of lung and stomach cancer. The SMR for lung cancer showed a consistent pattern in relation to duration of underground exposure, rising from 83 (observed/expected = 8/9.6) for surface workers (without exposure to arsenic) to 447 (15/3.4) for workers with more than 30 years underground exposure. Examination of the SMR for lung cancer by total underground exposure, age, and time since last exposure gave rise to a model for the expression of risk which depends only on total exposure and time since exposure. The fitted model implies that the effect of exposure to radon in a given year has no effect on risk for 10 years, then rapidly rises to a maximum from which the excess risk then declines, halving every 4.3 years. There were no direct measurements of historic radon levels. A conservative estimate based on measurements taken since 1969 by the National Radiological Protection Board and the Mines and Quarries Inspectorate is that the annual dose to an underground worker was about 10 working level months (WLM). Given this assumption, the risk/exposure slope implied by the present data, and the model fitted to it, was somewhat lower than that given in the fourth Committee on the Biological Effects of Ionisation Radiation (BEIR IV) report (about 40% lower for lifetime exposures). The present data also imply different risks depending on the age at exposure, with relatively higher lifetime risks for exposure at older ages, and relatively lower risks for exposures at younger ages. In conclusion, there was a clear relation between exposure to radon and death from lung cancer. The relative risk of lung cancer due to exposure to radon was not constant in cessation of exposure. The lifetime excess risk of lung cancer implied by these data for 40 years exposure at the current statutory limit of four WLM a year starting at age 20, was about 8% (79 excess deaths per 1000 exposed), assuming average smoking habits among the exposed workers. Control of dust concentrations in the mines has substantially reduced--and may have eliminated--direct mortality from silica related disease.     

A retrospective mortality study of workers exposed to arsenic in a gold mine and refinery in France

A historical mortality study of a cohort of employees of a gold mining and refining company was carried out in Salsigne, France. A major goal of the study was to investigate the relationship between lung cancer mortality and exposure to arsenic, radon, silica, and other contaminants of the working environment. A twofold excess of lung cancer was found both among miners and smelters, mainly concentrated among workers who had experienced exposure to past levels of arsenic, radon, and silica. The consistency of the results in the mine and the refinery are suggestive of a carcinogenic risk from both soluble and insoluble arsenic, although the potential role of other factors cannot be dismissed. © 1994 Wiley-Liss, Inc.     

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.     

Mortality of Sardinian lead and zinc miners: 1960-88.

The mortality of 4740 male workers of two lead and zinc mines was followed up from 1960 to 1988. Exposure to respirable dust was comparable in the two mines, but the median concentration of silica in respirable dust was 10-fold higher in mine B (12.8%) than in mine A (1.2%), but the mean annual exposure to radon daughters in underground workplaces differed in the opposite direction (mine A: 0.13 working levels (WL), mine B: 0.011 WL). Total observed deaths (1205) were similar to expected figures (1156.3) over a total of 119 390.5 person-years at risk. Underground workers of mine B had significant increases in risk of pulmonary tuberculosis (SMR 706, 95% confidence interval (95% CI) 473-1014) and non-malignant respiratory diseases (SMR 518; 95% CI 440-1606), whereas the only significant excess at mine A was for non-malignant respiratory diseases (SMR 246; 95% CI 191-312). Total cancer and lung cancer mortality did not exceed the expectation in the two mines combined. A 15% excess mortality for lung cancer, increased up to an SMR 204 (95% CI 89-470) for subjects employed > or = 26 years, was, however, found among underground workers in mine A who on the average experienced an exposure to radon daughters 10-fold higher than those of mine B. By contrast, despite their higher exposure to silica, mine B underground workers experienced a lower than expected lung cancer mortality. A ninefold increase in risk of peritoneal and retroperitoneal cancer combined was also found among underground workers of mine A (SMR 917; 95% CI 250-2347; based on four deaths). A causal association with workplace exposures is unlikely, however, as the SMR showed an inverse trend by duration of employment. These findings are consistent with low level exposure to radon daughters as a risk factor for lung cancer among metal miners. Exposure to silica at the levels estimated for the mine B underground environment did not increase the risk of lung cancer.     

Carcinoma of the lung in Ontario gold miners: possible aetiological factors.

A cohort of 54,128 men who worked in Ontario mines was observed for mortality between 1955 and 1986. Most of these men worked in nickel, gold, or uranium mines; a few worked in silver, iron, lead/zinc, or other ore mines. If mortality that occurred after a man had started to mine uranium was excluded, an excess of carcinoma of the lung was found among the 13,603 Ontario gold miners in the study (standardised mortality ratio (SMR) 129, 95% confidence interval (95% CI) 115-145) and in men who began to mine nickel before 1936 (SMR 141, 95% CI 105-184). The excess mortality from lung cancer in the gold miners was confined to men who began gold mining before 1946. No increase in the mortality from carcinoma of the lung was evident in men who began mining gold after the end of 1945, in men who began mining nickel after 1936, or in men who mined ores other than gold, nickel, and uranium. In the gold mines each year of employment before the end of 1945 was associated with a 6.5% increase in mortality from lung cancer 20 or more years after the miner began working the mines (95% CI 1.6-11.4%); each year of employment before the end of 1945 in mines in which the host rock contained 0.1% arsenic was associated with a 3.1% increase in lung cancer 20 years or more after exposure began (95% CI 1.1-5.1%); and each working level month of exposure to radon decay products was associated with a 1.2% increase in mortality from lung cancer five or more years after exposure began (95% CI 0.02-2.4%). A comparison of two models shows that the excess of lung cancer mortality in Ontario gold miners is associated with exposure to high dust concentrations before 1946, with exposure to arsenic before 1946, and with exposure to radon decay products. No association between the increased incidence of carcinoma of the lung in Ontario gold miners and exposure to mineral fibre could be detected. It is concluded that the excess of carcinoma of the lung in Ontario gold miners is probably due to exposure to arsenic and radon decay products.