钨矿接尘工矽肺危险度

目的　探讨钨矿接尘工矽肺危险度并对其防治措施进行评价。方法　采用职业流行病学队列研究方法 ,按接尘水平进行定量分析和定性分析 ,估算钨矿接尘工矽肺危险度。结果　①接尘工累积接总粉尘不到 10mg/(m3 ·a) ,就有 45例矽肺发病 ,发病率为 0 7% ;②累积接总粉尘量与观察期矽肺发生差异有显著性 (P <0 .0 5 ) ;③钨矿矿尘空气中最高容许水平是 2mg/m3 ,相当累积呼吸性游离二氧化硅尘 0 0 41mg/(m3 ·a) ,此值在钨矿仍有病例发生。结论　我国当前采用的粉尘卫生标准在钨矿不是最低危害作用水平。同时也说明各类接尘厂矿的接触限值是有区别的。     

Exposure to silica and silicosis among tin miners in China: exposure-response analyses and risk assessment

OBJECTIVES—To investigate the risk of silicosis among tin miners and to investigate the relation between silicosis and cumulative exposure to dust (Chinese total dust and respirable crystalline silica dust).
METHODS—A cohort study of 3010 miners exposed to silica dust and employed for at least 1 year during 1960-5 in any of four Chinese tin mines was conducted. Historical total dust data from China were used to create a job exposure matrix for facility, job title, and calendar year. The total dust exposure data from China were converted to estimates of exposure to respirable crystalline silica for comparison with findings from other epidemiological studies of silicosis. Each worker''s work history was abstracted from the complete employment records in mine files. Diagnoses of silicosis were based on 1986 Chinese pneumoconiosis Roentgen diagnostic criteria, which classified silicosis as stages I-III—similar to an International Labour Organisation (ILO) classification of 1/1 or greater.
RESULTS—There were 1015 (33.7%) miners identified with silicosis, who had a mean age of 48.3 years, with a mean of 21.3 years after first exposure (equivalent to 11.0 net years in a dusty job). Among those who had silicosis, 684 miners (67.4%) developed silicosis after exposure ended (a mean of 3.7 years after). The risk of silicosis was strongly related to cumulative exposure to silica dust and was well fitted by the Weibull distribution, with the risk of silicosis less than 0.1% when the Chinese measure of cumulative exposure to total dust (CTD) was under 10 mg/m³-years (or 0.36 mg/m³-years of respirable crystalline silica), increasing to 68.7% when CTD exposure was 150 mg/m³-years (or 5.4 mg/m³-years of respirable crystalline silica). Latency period was not correlated to the risk of silicosis or cumulative dose of exposure. This study predicts about a 36% cumulative risk of silicosis for a 45 year lifetime exposure to these tin mine dusts at the CTD exposure standard of 2 mg/m³, and a 55% risk at 45 years exposure to the current United States Occupational Safety and Health Administration and Mine Safety and Health Administration standards of 0.1 mg/m³ 100% respirable crystalline silica dust.
CONCLUSIONS—A clear exposure-response relation was detected for silicosis in Chinese tin miners. The study results were similar to most, but not all, findings from other large scale exposure-response studies.


     

Silicosis and tuberculosis in Zambian miners

Silicosis and tuberculosis (TB) are significant mining-related illnesses in developing countries. The purpose of this study was to examine annual cases of these diseases in Zambian miners, including comparison of periods before (1960-1970) and after (1992-2002) the arrival of the HIV/AIDS pandemic. The Occupational Health and Safety Research Bureau of Zambia reported 2114 cases from 1945 to 2002. Of these, 22.7% were silicosis, 65.4% TB, and the remaining 11.9% silicotuberculosis. While silicosis cases decreased from 28.6% to 12.4% with the arrival of HIV/AIDS, there was a large increase in tuberculosis cases (37.1% to 86.1%), with a corresponding decrease in silicotuberculosis cases (34.3% to 1.6%). Although silicosis remains an occupational health issue in Zambian miners, the most significant problem appears to be the marked increase in cases of TB.     

Silicosis and lung cancer in U.S. metal miners

The association between silicosis and lung cancer mortality was estimated in 9,912 (369 silicotics and 9,543 nonsilicotics) white male metal miners. These miners were examined by the U.S. Public Health Service during 1959-1961 and were followed through 1975. Miners were excluded from this study if they were employed in a mine during 1959-1961 that used diesel equipment underground. The ores that were mined consisted of copper, lead-zinc, iron, mercury, lead silver, gold and gold-silver, tungsten, and molybenum. The standardized mortality ratio (SMR, U.S. white male rates) for lung cancer was 1.73 (95% CI: .94-2.90) in silicotics and 1.18 (95% CI: .98-1.42) in nonsilicotics. Additionally, SMRs were higher in silicotics than in nonsilicotics, even in most subgroups stratified by cigarette smoking habit, type of ore mined, years of service in an underground job, radon exposure group, or year of hire. When lung cancer mortality between silicotics and nonsilicotics was compared, the age-adjusted rate ratio (95% CI) was 1.56 (.91-2.68), and the age- and smoking-adjusted rate ratio was 1.96 (.98-3.67). Corresponding figures for miners who were employed in mines with low levels of radon exposure were 1.90 (.98-3.67) and 2.59 (1.44-4.68), respectively. These findings indicate that lung cancer mortality risk was increased in silicotics, and this probably did not result from chance or bias. However, confounding from radon exposure could not be ruled out. The findings indicate that further follow-up of this cohort is needed.     

Dioxin: exposure-response analyses and risk assessment

Low-levels of dioxin cause cancer in animals. In 1997 dioxin was found to be a human carcinogen by the International Agency for Research on Cancer, based largely on four studies of industrial workers exposed to high levels. Recently there has been interest in estimating human cancer risk at low level environmental exposures. Here we review quantitative exposure-response analyses and risk assessment for low environmental levels based on the largest existing cohort of workers exposed to dioxin (the U.S. NIOSH cohort). We estimate that doubling background levels of exposure, which may occur for example by eating a lot of fish which have accumulated dioxin, will increase lifetime risk of cancer death by 0.1 to 1.0%. In the US the background risk of cancer death by age 75 is 12%, so doubling background levels of dioxin exposure would increase this lifetime risk to somewhere between 12.1 and 13.0%. Our results agree broadly with results from a German cohort, which is the only other cohort for which a quantitative risk assessment has been conducted.     

Silica exposure and silicosis among Ontario hardrock miners: III. Analysis and risk estimates

An epidemiological investigation was undertaken to determine the relationship between silicosis in hardrock miners in Ontario and cumulative exposure to silica (free crystalline silica--alpha quartz) dust. This report describes the analytic method and presents the risk estimates.     

Quantitative risk assessment of lung cancer in U.S. uranium miners

The National Institute for Occupational Safety and Health (NIOSH) has recently updated the vital status of the U.S. cohort of U miners through the end of 1982. This represents 69 additional lung cancer deaths since the last published follow-up through 1977. This more recent data was used to generate quantitative risk estimates of lung cancer after exposure to Rn daughters. Relative risks were estimated through use of the Cox proportional hazards model with an internal referent group. Results indicated that the exposure-response relationship was a slightly convex curve, predicting excess relative risks between 0.9 and 1.4 per 100 working level months (WLM) in the lower cumulative exposure range. Other findings of interest include a significant exposure-rate effect with low exposure rates more harmful per unit of cumulative exposure (WLM). Two temporal effects which modify relative risk estimates were also found. Relative risk increased with age at initial exposure to underground U mining. However, relative risk of lung cancer fell dramatically in the years following cessation of exposure.     

Silicosis compensation in Western Australian gold miners since the introduction of an occupational exposure standard for crystalline silica

Occupational exposure limits for crystalline silica are under review worldwide because of the large numbers of exposed people and, especially, because of the recent International Agency for Research on Cancer classification of silica as a human carcinogen. OBJECTIVES: The aims of this study were to (i) re-examine the incidence of silicosis in Western Australian gold miners and, using estimates of the total population at risk, (ii) estimate the upper confidence limit for the risk of silicosis in Western Australian gold miners since 1974, when the current exposure standard for crystalline silica was implemented. METHODS: Work histories of cases compensated for pneumoconiosis after 1974 were examined. Numbers of workers in the total workforce likely to be exposed to crystalline silica in Western Australia were estimated as the population at risk. RESULTS: There were no cases of compensated silicosis in Western Australian miners whose first dust exposure began during or after 1974. The upper 95% confidence interval for this zero rate was estimated to be 4.8 per 100,000 person-yr. CONCLUSIONS: There have been no compensated cases of silicosis in Western Australia among miners first exposed to crystalline silica after introduction of the current exposure standard. A rate of compensated silicosis higher than five cases per 100,000 person-yr is unlikely.     

Mortality of white South African gold miners.

OBJECTIVES--This two part study aimed to determine whether there was an excess mortality generally or for some diseases among middle aged white South African gold miners on the Witwatersrand and whether the underground dust exposure of these miners contributed to the development of lung cancer, chronic obstructive pulmonary disease (COPD), or ischaemic heart disease (IHD). METHODS--A cohort of 4925 white miners in South Africa, born between 1 January 1916 and 31 December 1930 who were alive and working in the vicinity of Johannesburg on 1 January 1970, then aged between 39 and 54, was followed up for 20 years by which time 2032 had died. Most were gold miners (about 87% had worked 85% or more of their shifts in gold mines). Standardised mortality ratios (SMRs) were calculated as percentages of the number of deaths observed in the cohort for a condition as stated on the death certificate divided by the number expected on the basis of concurrent mortality in the reference population (the total age specific white male population of South Africa). A case-control analysis was performed for three diseases (lung cancer, COPD, and IHD), the results of which are presented for those miners in the cohort who had spent at least 85% of their service on gold mines and had worked at least 15% of their shifts underground. RESULTS--The SMR for all causes of death was 129.6%, raised because of excess mortality due to the following causes: lung cancer (SMR = 139.8%), IHD (124.1%), COPD (189%) and cirrhosis of the liver (155.3%). Smoking was confirmed to be the main risk factor for lung cancer and COPD although cumulative dust exposure was found to increase the risk of COPD in conjunction with smoking. No significant risk of lung cancer resulted from exposure to dust. High blood pressure and smoking were found to increase the risk of IHD, but no association between IHD and the quetelet index (weight/height2) was found. CONCLUSIONS--The most significant and unexpected finding was the 30% increase in the SMR for all causes. Very little of this increase could be attributed to mining and the main factor for this was probably the adoption of an unhealthy lifestyle by these men (compared with other South African white men) particularly smoking (86% were smokers) and alcohol consumption.     

Mortality among sulfide ore miners.

Lung cancer mortality was studied during 1965-1985 in Outokumpu township in North Karelia, where an old copper mine was located. Age-specific lung cancer death rates (1968-1985) were higher among the male population of Outokumpu than among the North Karelian male population of the same age excluding the Outokumpu district (p less than .01). Of all 106 persons who died from lung cancer during 1965-1985 in Outokumpu township, 47 were miners of the old mine, 39 of whom had worked there for at least three years and been heavily exposed to radon daughters and silica dust. The study cohort consisted of 597 miners first employed between 1954 and 1973 by a new copper mine and a zinc mine, and employed there for at least 3 years. The period of follow-up was 1954-1986. The number of person-years was 14,782. The total number of deaths was 102; the expected number was 72.8 based on the general male population and 97.8 based on the mortality of the male population of North Karelia. The excess mortality among miners was due mainly to ischemic heart disease (IHD); 44 were observed, the expected number was 22.1, based on the general male population, and the North Karelian expected number was 31.2 (p less than .05). Of the 44 miners who died from IHD, 20 were drillers or chargers exposed to nitroglycerin in dynamite charges, but also to several simultaneous stress factors including PAHs, noise, vibration, heavy work, accident risk, and working alone. Altogether 16 tumors were observed in the cohort. Ten of these were lung cancers, the expected number being 4.3. Miners who had died from lung cancer were 35-64 years old, and had entered mining work between 1954 and 1960. Five of the ten lung cancer cases came from the zinc mine (1.7 expected). Three of them were conductors of diesel-powered ore trains. The slight excess mortality from lung cancer could be explained by exposure to radon daughters and by the combined effect of silica dust and diesel exhaust gases in the zinc mine.     

Mortality among Navajo uranium miners.

OBJECTIVES. To update mortality risks for Navajo uranium miners, a retrospective cohort mortality study was conducted of 757 Navajos from the cohort of Colorado Plateau uranium miners. METHODS. Vital status was followed from 1960 to 1990. Standardized mortality ratios were estimated, with combined New Mexico and Arizona non-White mortality rates used for comparison. Cox regression models were used to evaluate exposure-response relationships. RESULTS. Elevated standardized mortality ratios were found for lung cancer (3.3), tuberculosis (2.6), and pneumoconioses and other respiratory diseases (2.6). Lowered ratios were found for heart disease (0.6), circulatory disease (0.4), and liver cirrhosis (0.5). The estimated relative risk for a 5-year duration of exposure vs none was 3.7 for lung cancer, 2.1 for pneumoconioses and other respiratory diseases, and 2.0 for tuberculosis. The relative risk for lung cancer was 6.9 for the midrange of cumulative exposure to radon progeny compared with the least exposed. CONCLUSIONS. Findings were consistent with those from previous studies. Twenty-three years after their last exposure to radon progeny, these light-smoking Navajo miners continue to face excess mortality risks from lung cancer and pneumoconioses and other respiratory diseases.     

锡矿工人接尘与矽肺危险度评价

目的探讨粉尘暴露与矽肺危险度之间的接触效应关系。方法选择广西４个锡矿１９６０～１９６５年间工作１年以上的３０１０名接尘工人进行队列研究。用生存分析法统计累积粉尘接触量和矽肺出现的关系。结果追访到１９９４年底,检出矽肺１０１５例（３３．７％）。矽肺平均潜伏期２１．３年。总粉尘浓度７．５ｍｇ／ｍ３（ＴＷＡ）。拟合生存分析模型表明：矽肺发病危险度与累积接尘量的关系适合Ｗｅｉｂｕｌ分布。累积总粉尘接触量低于１０ｍｇ·ｍ－３·ａ－１时,矽肺危险小于１％;累积总粉尘接触量超过２０ｍｇ·ｍ－３·ａ－１时,矽肺累积危险度升高加快;累积总粉尘接触量达１５０ｍｇ·ｍ－３·ａ－１时,矽肺危险超过６８％。接尘时间与接尘量和矽肺危险度呈正相关。结论矽肺危险度与累积接尘量之间存在接触效应关系。     

Radon progeny exposure and lung cancer risk among non-smoking uranium miners

Studies of miners provide the basis for public health efforts to reduce residential radon progeny exposure. Because the preponderance of households do not have members who smoke indoors, studies of non-smoking miners contribute essential data for risk assessments for residential radon progeny exposure. We studied a cohort of 2,209 never-smokers who were underground uranium miners employed in the western U.S. from 1956 to the early 1990's and who participated in a screening program for lung cancer conducted by Saccomanno and colleagues. After determining the vital status and cause of death in the cohort, we conducted a nested case-control study of 55 lung cancer deaths in males and 3 age-matched controls for each case. The relative risk of lung cancer was 29.2 (95% CI 5.1, 167.2) for miners with greater than 1,450 WLM compared with those exposed to less than 80 WLM. Temporal factors affected risk, including average dose rate, which was inversely associated with lung cancer risk, and the length of time since last exposure, which was directly associated with decreased risk. As in studies of non-smokers and smokers combined, the exposure response relationship in never-smokers was consistent with a decreased slope at higher WLM, which resulted, in part, from an inverse dose rate effect.     

Silicosis and lung cancer among Chinese granite workers.

Of the 184 cases of silicosis registered between 1 January 1970 and 31 December 1984 in Singapore, all the relevant information was available for 159, which were linked to the population-based National Cancer Register for lung cancer. Nine cases of lung cancer were found. The standardized incidence ratio (SIR) was computed with the age- and calendar-specific incidence of lung cancer rates of Chinese males in Singapore as a basis. Excess risk of lung cancer was found (SIR 2.01, 95% confidence interval 0.92-3.81). Adjustment for smoking showed that it alone could not account for the excess lung cancer risk. There was an increasing, but not significant, trend with increasing severity of silicosis and exposure duration. The results suggest that the severity of silicosis and possibly exposure to free silica may have contributed to the excess of lung cancer among the cases of silicosis studied.     

Pulmonary dysfunction in gold miners with reactive airways.

In a cross sectional study of a working population of black South African gold miners a sample of 1197 older miners was examined. Airway reactivity determined by a greater than 10% response of the forced expiratory volume in one second (FEV1) to inhaled salbutamol was detected in 139 (12%) of the men. No relation was found between the extent of exposure to the underground environment and the frequency of airway reactivity. There was evidence of increased chronic airflow limitation in the men with reactive airways. This increase persisted after controlling for age, tobacco smoking, and for the presence and degree of silicosis. On average, the presence of reactive airways was associated with reduced (after bronchodilator) forced vital capacity (FVC) of 118 ml, 95% confidence interval (CI) 16 to 220 ml, FEV1 of 168 ml (95% CI 74-262 ml), FEV1/FVC% of 3% (95% CI 2.3-3.7%), and maximal mid-expiratory flow of 300 ml/s (95% CI 86-514 ml/s). Although there was no evidence that airway reactivity was induced by this occupational exposure, those with reactive airways appeared to be more susceptible to the adverse effects of the underground environment on the bronchial tree.     

矿砷致矿工肺癌特征性危险度评定

根据危险度评定原则,对201例50年代开始接触砷的矿工肺癌进行了特征性危险度评定。结果发现,初次下井年龄是砷致矿工肺癌特征性危险度重要因素之一;接砷矿工肺癌潜隐期与初次下井年龄呈负相关(回归系数b=-0.248,t_r=-4.028,P<0.001),未成年(<20岁)开始下井矿工肺癌潜隐期平均为30.1年,中位数为30年,成年后(≥20岁)开始下井矿工肺癌的平均潜隐期为27.2年,其中位数为29年;矿工肺癌发病年龄与初次下井年龄呈正相关(回归系数b=0.749,t_r=11.587,P<0.001),未成年下井者平均发病年龄为46.6岁,中位数为47.0岁,成年后下井者平均发病年龄为56.0岁,中位数为56.0岁;即初次下井年龄越小,其寿命损失越大,未成年下井者寿命损失比成年后下井者寿命损失多约10年。故研究砷致矿工肺癌时,须充分考虑初次下井年龄这一危险因素。结果表明,在立法时应限制接砷的年龄,不满20岁者不应从事接砷的劳动。     

Malaria among gold miners in southern Pará, Brazil: estimates of determinants and individual costs

As malaria grows more prevalent in the Amazon frontier despite increased expenditures by disease control authorities, national and regional tropical disease control strategies are being called into question. The current crisis involving traditional control/eradication methods has broadened the search for feasible and effective malaria control strategies--a search that necessarily includes an investigation of the roles of a series of individual and community-level socioeconomic characteristics in determining malaria prevalence rates, and the proper methods of estimating these links. In addition, social scientists and policy makers alike know very little about the economic costs associated with malarial infections. In this paper, I use survey data from several Brazilian gold mining areas to (a) test the general reliability of malaria-related questionnaire response data, and suggest categorization methods to minimize the statistical influence of exaggerated responses, (b) estimate three statistical models aimed at detecting the socioeconomic determinants of individual malaria prevalence rates, and (c) calculate estimates of the average cost of a single bout of malaria. The results support the general reliability of survey response data gathered in conjunction with malaria research. Once the effects of vector exposure were controlled for, individual socioeconomic characteristics were only weakly linked to malaria prevalence rates in these very special miners' communities. Moreover, the socioeconomic and exposure links that were significant did not depend on the measure of malaria adopted. Finally, individual costs associated with malarial infections were found to be a significant portion of miners' incomes.