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.     

广西锡矿工人恶性肿瘤死亡率研究

对大厂和栗木锡矿1972～1974年的在册职工7849人进行了历史前瞻性队列研究;并通过多种监测手段对环境有害因子进行了监测。结果表明,锡矿全死因死亡率为632.7/10万,与全国居民死亡率计算的期望数比较,SMR=1.11(95％CI为1.03～1.19),恶性肿瘤死亡为全死因之首(占39.3％),其次是脑血管疾病和心脏病。恶性肿瘤死亡明显超高(SMR=1.56),且主要集中在肺癌、肝癌和鼻咽癌,其中肺癌占首位(32.1％),SMR为1.98,肝癌和鼻咽癌的SMR为1.79和3.71。监测结果进一步表明,大厂矿肺癌超高与接尘水平及其可吸入砷浓度的高低有明显的联系。     

Mortality in uranium miners in west Bohemia: a long-term cohort study.

A cohort of 4320 uranium miners in West Bohemia who started work at the mines during 1948 to 1959 and worked there for at least four years were followed up to the end of 1990 to determine cause specific mortality risks in relation to exposures in the mines. The miners had experienced high radon exposures, on average 219 working level months during their uranium mining careers, for which detailed measurements were available. They had also been exposed to high arsenic levels in one of the two major mines, and to dust. New follow up methods, not previously used for occupational cohorts in Czechoslovakia, were utilised. By the end of follow up 2415 (56%) of the cohort were known to have died. Overall mortality was significantly raised compared with that in the general population (relative risk (RR) = 1.56, 95% confidence interval (95% CI) 1.50-1.63), with significantly raised risks of lung cancer (RR = 5.08, 95% CI 4.71-5.47), accidents (RR = 1.59, 95% CI 1.34-1.87), homicide (RR = 5.57, 95% CI 2.66-10.21), mental disorders (RR = 5.18, 95% CI 2.83-8.70), cirrhosis (RR = 1.51, 95% CI 1.16-1.94), and non-rheumatic circulatory diseases (RR = 1.16, 95% CI 1.08-1.25). The relative risk of lung cancer was greatest four to 14 years after entry to the mines. Relative risks for homicide and accidents were raised up to 25 years from entry but not after this. Substantial significantly raised risks at 15 to 24 years after entry occurred for cirrhosis, non-rheumatic circulatory diseases,a nd pneumonia and other respiratory infections. Sizeable significantly raised risks at 25 and more years after entry, but not earlier, were present for mental disorders, tuberculosis, and non-malignant non-infectious respiratory conditions. No specific causes showed risks significantly related to age at entry to mining. Risk of lung cancer was significantly positively related to radon exposure, estimated arsenic exposure, and duration of work in the mines, but no other cause was significantly positively related to these variables. The raised risk of lung cancer in uranium miners, which is well established, is related aetiologically to radon exposure, and in the present cohort it may also in part have been due to exposure to arsenic. The raised risks of accidents, tuberculosis, and non-infectious respiratory diseases have also been seen in other uranium mining cohorts, and are likely to reflect the dangerous and dusty working conditions and the confined spaces in which work occurred. The cirrhosis and homicide deaths probably related to the lifestyle associated with mining. The raised risk of circulatory diseases does not seem to be related to radon or arsenic exposure; its causes are unclear. The use of multiple follow up methods was found to be mortality in the cohort.     

Risk factors and early detection of lung cancer in a cohort of Chinese tin miners

PURPOSE: To examine risk factors and establish a biologic specimen and data bank for the study of early markers of lung cancer.

METHODS: We designed a dynamic cohort using an ongoing lung cancer screening program among radon- and arsenic-exposed tin miners in Yunnan China. Through the first four years of the study, 8,346 miners aged 40 years and older with over 10 years of occupational exposure have been enrolled, risk factors have been assessed, annual sputum and chest radiographs have been obtained, and numerous biologic specimens have been collected.

RESULTS: A total of 243 new lung cancer cases have been identified through 1995. Radon and arsenic exposures are the predominant risk factors, but lung cancer risk is also associated with chronic bronchitis and silicosis, as well as a number of measures of exposure to tobacco smoke, including early age of first use, duration, and cumulative exposure. Tumor and sputum samples are being examined for early markers of lung cancer.

CONCLUSION: A cohort of occupationally-exposed tin miners with an extensive biologic specimen repository has been successfully established to simultaneously study the etiology and early detection of lung cancer.     

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.     

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.     

A mortality study of workers manufacturing friction materials: 1941-86.

The mortality of workers employed at a factory producing friction materials has been studied from 1941 to 1986, extending a previous study by seven years. Apart from two periods before 1944, when crocidolite asbestos was used on one particular contract, only chrysotile asbestos has been used. Thirteen deaths were attributed to mesothelioma and of these, 11 were of subjects who had known contact with crocidolite asbestos. Of the remaining two, in one instance the diagnosis is uncertain and in the other the occupational history of the subject is not well established. There was no excess of deaths from lung cancer or other asbestos related tumours, or from chronic respiratory disease. After 1950 hygienic control was progressively improved and from 1970 levels of asbestos in air have not exceeded 0.5-1.0 f/ml. It is concluded that with good environmental control chrysotile asbestos may be used in manufacture without causing excess mortality.     

Mortality in a cohort of vermiculite miners exposed to fibrous amphibole in Libby, Montana

Background: Fibrous tremolite is a widespread amphibole asbestiform mineral, airborne fibres of which constitute an environmental hazard in Libby, Montana, northern California, and elsewhere.

Aims: To determine excess risk from lung cancer, mesothelioma, and all-cause mortality in a cohort of men exposed to tremolite, but no other form of asbestos.

Methods: Mortality by certified cause and various measures of exposure to tremolite and related amphibole fibres was assessed in a cohort of 406 vermiculite mineworkers in Libby, Montana, employed before 1963 and followed until 1999.

Results: Total deaths were: lung cancer 44 (SMR 2.40), non-malignant respiratory disease (NMRD) 51 (SMR 3.09), all causes 285 (SMR 1.27); included among the total were 12 deaths ascribed to mesothelioma (4.21% of all deaths). Adjusted linear increments in relative risks (per 100 f/ml.y), estimated by Poisson regression, were: lung cancer (0.36, 95% CI 0.03 to 1.20), NMRD (0.38, 95% CI 0.12 to 0.96), and all deaths (0.14, 95% CI 0.05 to 0.26).

Conclusions: The all-cause linear model would imply a 14% increase in mortality for mine workers exposed occupationally to 100 f/ml.y or about 3.2% for a general population exposed for 50 years to an ambient concentration of 0.1 f/ml. Amphibole fibres, tremolite in particular, are likely to be disproportionately responsible for cancer mortality in persons exposed to commercial chrysotile, but to what extent cannot be readily assessed.

     

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 and cancer incidence in a small cohort of miners exposed to low levels of alpha radiation

Due to the continuing controversy over the effects on humans of low-level ionizing radiation, overall mortality and cancer incidence among miners from a magnetite mine was investigated. The study comprises 332 underground miners. The average concentration of Rn progeny is presently 0.10-0.15 working levels (WL). Included in the study were those employed for more than 36 months in the period 1940-1960, who were still alive in 1953. The follow-up period covers 1953-1980. Mortality was equal to estimated values based on age-specific national figures. The observed/expected ratio for lung cancer incidence was 1.1. Comparison was also made to 190 miners from a mine with negligible radiation (less than 0.02 WL). The same mortality was observed, but this mine showed a ratio for lung cancer incidence of 2.2. The study population is too small to repudiate the hypothesis of increased health risk after exposure to low levels of alpha radiation.     

Mortality from lung cancer among copper miners.

A cohort mortality study of lung cancer in 7088 copper miners was made from 1 January 1969 to 31 December 1988. There was an excess of deaths from lung cancer in the copper miners. The standardised mortality ratio (SMR) was 147 (p < 0.01). The SMR increased with calendar period. There was a higher risk of deaths from lung cancer in the miners employed in the 1950s. Age at the start of exposure had no effect on the risk of lung cancer. The risk of death from lung cancer increased with the duration of exposure and the time since first exposure. The SMR for lung cancer was 173 in underground miners and 193 for drilling miners (both p < 0.01). These data show that exposure to dust is associated with an excess of deaths from lung cancer in copper miners whereas exposure to radiation does not seem to carry such risk.     

Mortality from stomach cancer in Ontario miners.

An excess of mortality from stomach cancer has been found in Ontario gold miners (observed (obs) 104, standardised mortality ratio (SMR) 152, 95% confidence interval (95% CI) 125-185) and no excess of stomach cancer could be detected in other miners in Ontario (obs 74, SMR 102, 95% CI 80-128). The excess of stomach cancer appeared five to 19 years after the miners began gold mining in Ontario. In that interval, similar patterns of excess mortality from stomach cancer were found in miners born in north America (obs 14, SMR 268, CI 147-450) and in miners born outside north America (obs 12, SMR 280, 95% CI 145-489). Twenty or more years after the miners began mining gold, an excess of mortality from stomach cancer was found in gold miners born outside of north American (obs 41, SMR 160, 95% CI 115-218) but not in gold miners born in north America (obs 37, SMR 113, 95% CI 80-156). The excess of stomach cancer in gold miners under the age of 60 (obs 45, SMR 167, 95% CI 122-223) seems larger than the excess in gold miners between the ages of 60 and 74 (obs 59, SMR 143, 95% CI 109-184). Exposures to arsenic, chromium, mineral fibre, diesel emissions, and aluminium powder were considered as possible explanations of the excess of stomach cancer in Ontario gold miners. Exposure to diesel emissions and aluminium powder was rejected as gold miners and uranium miners were exposed to both agents but an excess of stomach cancer was noted only in gold miners. The association between the excess of stomach cancer and the time since the miner began mining gold suggested that duration of exposure to dust in gold mines ought to be weighted according to the time since the exposure to dust occurred and that an appropriate time weighting function would be one in the interval five to 19 years after each year of exposure to dust and zero otherwise. A statistically significant association between the relative risk of mortality from stomach cancer and the time weighted duration of exposure to dust in gold mines was found in miners under the age of 60. Time weighted indices of exposure to chromium and arsenic were formed for each gold miner by time weighting the product of the duration of exposure to dust in a gold mine and the percentages of arsenic and chromium in rocks in that gold mine. Exposure to mineral fibre was measured in terms of the time weighted duration of employment in those gold mines that contain mineral fibre. A statistically significant association between the excess of stomach cancer in gold miners under the age of 60 and the time weighted index of exposure to chromium occurred and not association was found between the excess of stomach cancer and either the time weighted duration of employment in mines containing mineral fibre. The excess of stomach cancer in gold miners under the age of 60 was better associated with the time weighted index of exposure to chromium than to the time weighted duration of exposure to dust in gold mines. Although the number of cases of gastric cancer that were classified according to the system of Lauren was small, the data suggest that for miners under the age of 60, exposure to chromium is associated with the development of the intestinal rather than the diffuse type of gastric cancer.     

A mortality study of workers manufacturing friction materials: 1941-86

The mortality of workers employed at a factory producing friction materials has been studied from 1941 to 1986, extending a previous study by seven years. Apart from two periods before 1944, when crocidolite asbestos was used on one particular contract, only chrysotile asbestos has been used. Thirteen deaths were attributed to mesothelioma and of these, 11 were of subjects who had known contact with crocidolite asbestos. Of the remaining two, in one instance the diagnosis is uncertain and in the other the occupational history of the subject is not well established. There was no excess of deaths from lung cancer or other asbestos related tumours, or from chronic respiratory disease. After 1950 hygienic control was progressively improved and from 1970 levels of asbestos in air have not exceeded 0.5-1.0 f/ml. It is concluded that with good environmental control chrysotile asbestos may be used in manufacture without causing excess mortality.     

Mortality in a cohort of tannery workers.

OBJECTIVES: To evaluate the mortality of a group of tannery workers. METHODS: The cohort consisted of 1244 workers (870 men and 374 women) employed at a chrome tannery between 1955 and 1988. A total of 36414 person-years of follow up was calculated (369 people had died). National and regional mortalities were used to estimate the expected numbers. RESULTS: All cause mortality was similar to that of the general population. The most remarkable excess was for bladder cancer (observed 10, standardised mortality ratio (SMR) 242, 95% confidence interval (95% CI) 116 to 446). An excess of colorectal cancer (observed 17, SMR 180, 95% CI 105 to 288) was also found, based on an increased risk of both colon (SMR 166) and rectal cancer (SMR 206). No recognisable patterns emerged from the analyses by years since first employment, calendar year of hire, or lagging exposures. CONCLUSIONS: The increased mortality from bladder cancer is likely due to exposure to benzidine based leather dyes. If the apparent excess of colorectal cancer is real, its causes are as yet unknown.     

Mortality from lung cancer in Ontario uranium miners.

Mortality from lung cancer was greater in Ontario uranium miners than in the general male population of Ontario (observed = 152, expected = 67.6, standardised mortality ratio 225, 95% confidence interval 191-264). Part of the excess of lung cancer may be because the proportion of men who are smokers or have smoked is greater in uranium miners than in Ontario men. Smoking does not explain the whole excess. Mortality from lung cancer in Ontario uranium miners is clearly related to exposure to short lived radon progeny. The excess relative risk of lung cancer from the same degree of exposure to short lived radon progeny is greatest five to 14 years after exposure and less subsequently. It is greater in men under the age of 55 years and less in older men. Part of the excess of lung cancer mortality in Ontario uranium miners is probably also due to exposure to arsenic that occurred earlier in gold mines. In Ontario uranium miners, the lung cancer mortality from exposure to arsenic increases as the intensity of exposure to short lived radon progeny increases. This finding is consistent with the hypothesis that the risk of lung cancer from exposure to arsenic is enhanced by exposure to other carcinogens. In Ontario uranium miners, the proportion of lung cancers that are small cell carcinomas is greater than in the general population. The proportion of small cell carcinomas is especially great five to 14 years after exposure to short lived radon progeny and in men who die from lung cancer at younger ages.     

云锡矿工慢性支气管炎与肺癌关系的队列研究

目的探讨云锡矿工既往慢性支气管炎与肺癌的关系。方法利用前瞻性队列研究方法,分析云锡矿工肺癌高危人群慢性支气管炎与肺癌死亡危险的关系。结果1992—1999年,共9 295名云锡矿工进入队列,随访至2001年底,共443例肺癌死亡。慢性支气管炎可增加肺癌死亡危险性,调整危险比(HR)为1.5(95%CI:1.3～1.8),慢性支气管炎与肺鳞癌呈显著正相关,与腺癌和小细胞癌症的关联则无显著性。分层分析结果表明,两者关联仅在吸烟者中差异具有显著性。结论慢性支气管炎可能是云锡矿工肺癌死亡的危险因素之一,其致肺癌的危险应引起重视并加以控制。