Exposure to nickel compounds and smoking in relation to incidence of lung and nasal cancer among nickel refinery workers.

OBJECTIVES: To investigate the relation between occupational hazards among nickel refinery workers and their exposure to different forms of nickel over time and the interaction between smoking and total exposure to nickel. METHODS: The cohort consisted of 379 workers with first employment 1916-40 and at least three years of employment and 4385 workers with at least one year of employment 1946-83. Data on smoking (ever or never) were available for almost 95% of the cohort. Two analyses were used, indirect standardisation from observed and expected numbers and Poisson regression. RESULTS: During the follow up 1953-93, 203 new cases of lung cancer were observed v 68 expected (standardised incidence ratio (SIR) 3.0, 95% confidence interval (95% CI) 2.6-3.4) and 32 cases of nasal cancer were observed v 1.8 expected (SIR 18.0, 95% CI 12-25). The Poisson regression analysis showed an excess risk of lung cancer in association with exposure to soluble forms of nickel, with a threefold increase in relative risk (RR) (P < 0.001) and a multiplicative effect of smoking and exposure to nickel. The RRs were 1.1 (95% CI 0.2-5.1) for exposed workers who had never smoked and 5.1 (95% CI 1.3-20.5) for exposed workers who smoked. CONCLUSION: It is not possible to state with certainty which specific nickel compounds are carcinogenic, but a significant excess risk was found for workers exposed to soluble nickel alone or in combination with other forms of nickel. The present study suggests a multiplicative effect of smoking and nickel exposure.     

Can lung cancer risk among nickel refinery workers be explained by occupational exposures other than nickel?

BACKGROUND: Exposures in nickel refineries represent complex chemical mixtures, but only the effect of nickel has been evaluated quantitatively in epidemiologic studies of nickel workers. METHODS: For a Norwegian refinery, time- and department-specific exposure estimates were developed for arsenic, sulfuric acid mists, and cobalt in air on the basis of personal measurements and chemical data on raw materials and process intermediates. Exposure to asbestos, as well as employment in high-risk occupations outside the refinery, were assessed. We conducted a case-control study nested in a cohort of refinery workers, with 213 cases (diagnosed 1952-1995) and 525 age-matched controls. We analyzed lung cancer risk, adjusted for smoking, by cumulative exposure and duration of work. RESULTS: There was a substantial association between cumulative exposure to water-soluble nickel and lung cancer risk. Weaker effects were suggested for exposure to arsenic at the refinery and for occupational exposures outside the refinery for 15 years or more. No detectable excess risk was found for refinery exposure to asbestos or sulfuric acid mists, and no dose-related increase in risk was seen from cobalt. CONCLUSIONS: Exposure to water-soluble nickel remained the most likely explanation for the excess lung cancer risk in the cohort. Other occupational exposures did not confound the strong dose-related effect of nickel to any appreciable degree.     

职业接尘及吸烟致呼吸系统疾病死亡危险度比较的队列研究

目的 比较接尘、吸烟对呼吸系统疾病死亡的影响.方法 在1989年至1992年广州建立职业健康监护档案的基础上对30岁以上、职业接触粉尘和无粉尘接触的80 987名工人进行前瞻性队列研究.结果 （1）队列平均年龄43.5岁,职业性粉尘接触率16.3%,吸烟率43.7%,饮酒率33.5%.（2）队列平均随访8年,35人失访,失访率0.04%,总死亡1 593人中,219人死于肺癌,90人死于非恶性肿瘤性呼吸系统疾病.（3）调整相关因素后,相对于不吸烟者,吸烟者肺癌死亡相对危险度（RR）为3.32,是粉尘接触者相对于无粉尘接触者肺癌死亡RR（1.53）的2.2倍.粉尘接触者非恶性肿瘤性呼吸系统疾病死亡RR为2.41,是吸烟者（1.89）的1.28倍.尤其是矽尘接触者,其非恶性肿瘤性呼吸系统疾病死亡RR为5.72,是吸烟者的3.03倍.既接触粉尘又吸烟,呼吸系统疾病死亡RR增加更明显.（4）男性吸烟者呼吸系统疾病死亡危险分别随日吸烟量、烟龄的增加而增加.结论 职业接触粉尘和吸烟均可引致超额的呼吸系统疾病死亡,两者存在协同作用.吸烟致肺癌死亡RR高于接尘,而致非恶性肿瘤性呼吸系统疾病死亡RR则低于接尘.吸烟与呼吸系统疾病死亡危险存在明显的剂量-效应关系.     

接尘、吸烟者死亡危险度比较的前瞻性队列研究

目的 比较接尘、吸烟对死亡的影响。方法 以1989～1992年广州市实施并建立的职工职业健康监护档案为基础资料，选年龄≥30岁的80987名接尘和无接尘职工为研究对象，进行前瞻性队列研究。结果 (1)队列平均43．5岁，主要为工人、中学文化程度、已婚，接尘率16．3％，吸烟率43．7％，饮酒率335%。(2)队列平均随访8年，失访35人，死亡1539人，以恶性肿瘤死亡为主。(3)调整相关混杂因素后，全死因、恶性肿瘤、心脑血管疾病等死亡相对危险度(RR)，接尘者和吸烟者基本一致，但鼻咽癌、呼吸系统疾病死亡RR值，接尘者高于吸烟者，而肺癌、胃癌死亡RR值，吸烟者分别是接尘者的2．2倍和1．5倍；接尘可协同吸烟致死亡危险性明显增加。(4)男性总死因、恶性肿瘤和呼吸系统疾病死亡RR值，矽尘接触者高于吸烟者，心脑血管疾病死亡RR值，木尘接触者也高于吸烟者。(5)人群死亡归因危险度百分比(PARP)吸烟者是接尘者的2．5倍。(6)男吸烟者全死因、恶性肿瘤、肺癌、胃癌的死亡危险随日吸烟量、烟龄的增加而明显递增，冠心病、呼吸系统疾病的死亡危险则分别随日吸烟量、烟龄的增加而增加。结论 接尘、吸烟者死亡RR值基本一致，接尘与吸烟存在协同作用，某些死因死亡危险吸烟者较明显，某些接尘者较明显；吸烟者PARP较接尘者高；吸烟与死亡危险存在明显的剂量效应关系。     

An 11-year longitudinal study of the occupational dust exposure and lung function of polyvinyl chloride, cement and asbestos cement factory workers

Standardized questionnaires and lung function tests were administered in 1973, 1980, and 1984 to 126 workers occupationally exposed to polyvinyl chloride (PVC) dust, to cement dust, or to asbestos cement dust until 1974-1978 and to PVC thereafter. The workers in the last group were assigned to two asbestos exposure categories (heavy and slight). The decline in forced vital capacity (FVC) and forced expiratory volume in 1 s (FEV1.0) was analyzed with regard to the length of time since the data of first employment. After adjustment for age, height, and smoking status at the date of first employment, the decline in FVC and FEV1.0 among the nonsmokers-light smokers was slightly accelerated with length of employment in the PVC and slight asbestos exposure groups and markedly accelerated with time since first employment in the heavy asbestos exposure group. The heavy smokers in all the exposure groups had FVC and FEV1.0 predicted values that were lower than those of the nonsmokers-light smokers; these differences remained constant with length of employment. Cessation of asbestos exposure for about 10 years did not seem to change lung function decline.     

Lung cancer and occupation in nonsmokers: a multicenter case-control study in Europe

BACKGROUND: Tobacco smoking is the main cause for lung cancer worldwide, making it difficult to examine the carcinogenic role of other risk factors because of possible confounding by smoking. Therefore, the present study aimed to investigate the association between lung cancer and occupation independent of smoking. METHODS: A case-control study of lung cancer was carried out between March 1998 and January 2002 in 16 centers from 7 European countries, including 223 never-smoking cases and 1039 controls. Information on lifestyle and occupation was obtained through detailed questionnaires. Job and industries were classified as entailing exposure to known or suspected carcinogens; in addition, expert assessment provided exposure estimates to specific agents. RESULTS: The odds ratio of lung cancer among women employed for more than 12 years in suspected high-risk occupations was 1.75 (95% confidence interval = 0.63-4.85). A comparable increase in risk was not detected for employment in established high-risk occupations or among men. Increased risk of lung cancer was suggested among individuals exposed to nonferrous metal dust and fumes, crystalline silica, and organic solvents. CONCLUSION: Occupations were found to play a limited role in lung cancer risk among never-smokers. Jobs entailing exposure to suspected lung carcinogens should receive priority in future studies among women. Nonferrous metal dust and fumes and silica may exert a carcinogenic effect independently from smoking.     

Lung Cancer in Chinese Women: Evidence for an Interaction between Tobacco Smoking and Exposure to Inhalants in the Indoor Environment

Background

Epidemiologic data suggest that Chinese women have a high incidence of lung cancer in relation to their smoking prevalence. In addition to active tobacco smoke exposure, other sources of fumes and airborne particles in the indoor environment, such as cooking and burning of incense and mosquito coils, have been considered potential risk factors for lung cancer.

Objectives

We used a case–control study to explore effects of inhalants from combustion sources common in the domestic environment on lung cancer and their modification by active tobacco smoking.

Methods

We analyzed 703 primary lung cancer cases and 1,578 controls. Data on demographic background and relevant exposures were obtained by face-to-face interviews in the hospital.

Results

We observed a positive relationship with daily exposure to incense or mosquito coils and to cooking fumes only among smokers, and no association among lifetime nonsmokers. Interactions between smoking and frequency of cooking, or exposure to incense or mosquito coils were statistically significant and consistent with synergistic effects on lung cancer. The odds ratio (OR) comparing smokers without daily incense or mosquito coil exposure with nonsmokers without daily exposure was 2.80 [95% confidence interval (CI), 1.86–4.21], whereas the OR comparing smokers with daily exposure to the same referent group was 4.61 (95% CI, 3.41–6.24). In contrast, daily exposure to incense or mosquito coils was not associated with lung cancer among nonsmokers (OR = 0.91; 95% CI, 0.72–1.16). We observed the same pattern of associations for smokers without (OR = 2.31; 95% CI, 1.52–3.51) and with (OR = 4.50; 95% CI, 3.21–6.30) daily cooking exposure compared with nonsmokers, with no evidence of an association with daily cooking exposure among nonsmokers.

Conclusion

Our results suggest that active tobacco smoking not only is an important risk factor for development of lung cancer, but also may cause smokers to be more susceptible to the risk-enhancing effects of other inhalants.     

A case-control study of lung cancer among refinery workers

This case-control study examined the relationship between lung cancer and the work histories of male employees at a large Texas refinery. The study included 112 lung cancer deaths observed between 1946 and 1987 and 490 matched controls. Employment histories were obtained from personnel records, and smoking information was available from medical records. Both stratification methods and conditional logistic regression were used in data analyses. Overall employment in four general job categories (administrative, engineering/laboratory, process, maintenance/mechanical) was not associated with lung cancer mortality. Results by hire period (< 1940, 1940+) showed that workers hired into process jobs before 1940 had a nonsignificantly elevated odds ratio (OR) of 1.71 (95% confidence interval [CI] = 0.85-3.45) compared with nonprocess workers hired before 1940. Among process workers hired before 1940, there was a significant trend toward increasing OR with increasing duration of employment in process jobs, and the association with lung cancer was strongest among smokers in the highest duration category of 30+ years (OR = 2.98, 95% CI = 1.07-8.31). Latency analyses of process workers hired before 1940 indicated that their lung cancer risk had peaked between 30 and 50 years since first employment. Definitive statements about causal factors are limited because results among process workers were based on small numbers of subjects in some exposure categories, and there was no information on specific workplace exposures. The OR for maintenance/mechanical jobs after adjustment for smoking was 1.00 (95% CI = 0.55-1.82). Furthermore, there was no pattern in relation to duration of employment in maintenance/mechanical jobs. The results from this study do not support the hypothesis that work in maintenance/mechanical jobs increases lung cancer risk. On the basis of analyses in this study, it is unlikely that asbestos exposure contributed to excess lung cancer mortality. Additional analyses were conducted for specific maintenance jobs with potential exposure to asbestos and by duration in jobs with occasional or routine asbestos exposure. No significant increase in lung cancer was found in any subgroup. Furthermore, there was no significant trend toward lung cancer risk in relation to duration of employment in jobs with asbestos exposure.     

Incidence of cancer among welders and other shipyard workers with information on previous work history

The incidence of cancer among 4480 shipyard workers, including 861 welders, was investigated for a potential relationship between exposure to welding fumes and lung cancer. A subcohort of 3150 workers with information on previous work history was studied separately. This investigation is a historical prospective cohort study. Environmental air samples were collected in 1973, 1977, and 1989. Information on smoking habits was surveyed in 1976 and 1984. The employment work histories were collected from the personnel register. There were 411 observed cancers of all sites versus 387.5 expected, and 45 cases of lung cancer versus 51.3 expected. Nine cases of lung cancer were found among the welders versus 7.1 expected. Among 310 former seamen with welding experience, there was 1 case of lung cancer versus 2.1 expected. These shipyard workers showed no excess risk of lung cancer. Tobacco smoking and asbestos exposure are potential confounders in the study. There was no clear relationship between exposure to welding fumes and lung cancer, but welders with the longest experience had a relative risk of 1.9 for lung cancer. The differences in lung cancer incidence among the different shipyard workers could not be attributed to differences in recruitment patterns or previous work history.     

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.

     

The potential hazardous effect of exposure to iron dust in Egyptian smoking and nonsmoking welders

Exposure to iron dust and welding fumes is widespread and may increase the risk of lung inflammation. The aim of this study was to identify associations between exposure to iron/welding fumes and the levels of inflammatory parameters and allergic mediators among 120 Egyptian men. Forty nonsmoking and 40 smoking Egyptian welders as well as 40 healthy volunteers who were never exposed to welding fumes and were nonsmoking were enrolled in the study. Peak expiratory flow rates (PEFR) assessed at the end of the shift of work on working days revealed an impairment in lung function, with the smoking workers showing the worse results, followed by nonsmoking workers, as compared to healthy volunteers. Moreover, the results of the present study showed a significant increase in serum iron and immunoglobulin E, as well as plasma thiobarbaturic acid reactive substances, C-reactive protein, tumor necrosis factor-alpha, haptoglobin, interleukin-2, interleukin-6 and interleukin-23 histamine, lactate dehydrogenase isoenzyme-3, and calcitonin. In addition, the results revealed significant decrease in plasma α-1-antitrypsin and serum transferrin, as well as blood activities of antioxidant enzymes: catalase, superoxide dismutase, glutathione peroxidase, and glutathione reductase (as compared with control group). However, there was a nonsignificant change in arginase and α-L-fucosidase in smoking and nonsmoking welders exposed to iron dust and welding fumes. In conclusion, occupational exposure to iron dust and welding fumes increases lung inflammation risk among Egyptian blacksmith workers, a condition that worsens with smoking.     

Respiratory health of workers exposed to metal dusts and foundry fumes in a copper refinery.

OBJECTIVES--To assess airflow limitation in workers exposed long term to metal dust, the prevalence of pleural plaques in those workers exposed in the past to asbestos, the influence of pleural plaques on lung function, and the possible association with airway disease caused by asbestos. METHODS--A cross sectional and longitudinal (seven year) survey of 494 long term (mean (SEM) 21(1) years) workers in a copper refinery was carried out from medical questionnaires, chest radiographs, and forced spirometry. RESULTS--The prevalence of lifetime non-smokers was 19%, current smokers 39%, and ex-smokers 42%. The prevalence of chronic obstructive pulmonary diseases (COPD) (forced expiratory volume in one second (FEV1) < 80% predicted) was 5%, small airway dysfunction (SAD) (maximal mid-expiratory flow (MMEF) < 60% predicted) was 7%, and this did not differ from the control population. The COPD and SAD were associated with cumulative smoking index but not with the cumulative work years at the plant or with any type of work at the plant. The mean (SEM) reduction of FEV1 was 20(7) ml in non-smokers, 26(4) ml in smokers, and 26(5) ml in ex-smokers (P > 0.05). In the smokers and ex-smokers with COPD, the loss of FEV1 was 53(10) (P < 0.02). The prevalence of pleural plaques was 11% (P < 0.0001); pleural plaques were found in older workers with known exposure to asbestos. The pleural plaques were circumscribed and associated with a non-significant 196 ml reduction in forced vital capacity (FVC) and non-significant reduction of FVC over time. The pleural plaques were not associated with COPD or SAD. The cumulative smoking index obtained by a technician did not differ from that by a chest physician. CONCLUSIONS--Despite exposures to asbestos that produced pleural plaques and exposures to metal dusts and foundry fumes the long term workers of this plant did not have excessive prevalence of COPD or SAD. The data suggest that low level long term exposure to metal dusts, gases, and foundry fumes do not necessarily cause respiratory dysfunction, circumscribed pleural plaques with low grades of width and extent do not reduce FVC significantly, and exposure to asbestos dust that produced pleural plaques does not necessarily produce airway dysfunction.     

Relative importance of cigarette smoking in occupational lung disease.

Since 1900 respiratory disease has remained a constant serious cause of chronic ill health and premature death in Britain. The falling importance of tuberculosis and pneumonia has been off-set by the rise in lung cancer. Bronchitis morbidity and mortality have fallen only slightly since 1935. To produce any real improvement in the future existing information as to cause must be studied. The relative contribution of occupational exposure is compared with the importance of cigarette smoking. Relevant information is scanty and has been produced to emphasise the existence of occupational diseases rather than assess their importance to the community as whole. In Britain the evidence is that within the coal mining and iron and steel industries conditions are now such that dust exposure contributes little to the morbidity or mortality compared with the workers' smoking habits. Similar results have been shown by a cross-sectional survey of many dusty occupations in Western Germany. Only in the disappearing Welsh slate industry has dust disease been at least as important as smoking. Until the current regulations were introduced conditions existed among asbestos workers such that the combined effect of cigarette smoking and dust exposure led to a loss of life expectation of over 10 years in moderate smokers. Since the new regulations were introduced the risk for asbestos workers should approximate to that for other industrial workers. While control of occupational exposure to respiratory hazards remains important, a far greater improvement to respiratory health would be produced by controlling tobacco smoking.     

A cohort study of bronchial carcinomas in workers producing chromate pigments.

A cohort study of the incidence of bronchial cancer in male workers in a small company producing chromate pigments is presented. Altogether 133 workers had been employed by the company from the time production was started in 1948 until the end of 1972. Workers with more than three years employment were included in the study, and three cases of bronchial carcinoma were found among the 24 workers who fulfilled this requirement. Based on the data of the Cancer Registry of Norway the risk of bronchial cancer for a corresponding group of the general population was found to be 0.079, which gives a risk ratio for exposed workers of approximately 38. The average age of the cancer patients was as low as 50 years at the time of diagnosis. All workers in the company had been exposed mainly to zinc chromate dust, and the exposure levels of the workers developing bronchial cancers had probably been from 0-5 to 1-5 mg Cr/m-3 for six to nine years. Two of the three patients were smokers. It is assumed that exposure to chromate pigments, and probably to zinc chromate, may be related to the increased incidence of bronchial cancer in this group of workers. The possibility of a contributing effect of tobacco smoking in at least two of the three cases cannot be ruled out.     

A cohort study of bronchial carcinomas in workers producing chromate pigments.

A cohort study of the incidence of bronchial cancer in male workers in a small company producing chromate pigments is presented. Altogether 133 workers had been employed by the company from the time production was started in 1948 until the end of 1972. Workers with more than three years employment were included in the study, and three cases of bronchial carcinoma were found among the 24 workers who fulfilled this requirement. Based on the data of the Cancer Registry of Norway the risk of bronchial cancer for a corresponding group of the general population was found to be 0.079, which gives a risk ratio for exposed workers of approximately 38. The average age of the cancer patients was as low as 50 years at the time of diagnosis. All workers in the company had been exposed mainly to zinc chromate dust, and the exposure levels of the workers developing bronchial cancers had probably been from 0-5 to 1-5 mg Cr/m-3 for six to nine years. Two of the three patients were smokers. It is assumed that exposure to chromate pigments, and probably to zinc chromate, may be related to the increased incidence of bronchial cancer in this group of workers. The possibility of a contributing effect of tobacco smoking in at least two of the three cases cannot be ruled out.     

Lung cancer risk in iron and steel foundry workers: a nested case control study in Asturias, Spain

BACKGROUND: Workers of iron and steel foundries have a high lung cancer risk but the findings on specific processes associated with this risk are inconsistent. We examined the risk of lung cancer among workers in the main industrial processes of a large iron and steel foundry in Asturias, Spain. METHODS: We conducted a nested case-control study comprised of 144 male lung cancer cases and 558 controls, selected from a study base of about 24,400 workers employed in the industry between 1952 and 1995. Cases were identified through linkage of industry records with those of two cancer registries. Controls were selected through industry records using incidence density sampling, were matched to cases by age and date of birth and had to be alive and without lung cancer at the time of selection. Smoking history was obtained through company medical records. Unconditional logistic regression was applied and all ORs were adjusted for age and tobacco consumption. RESULTS: Workers were, on an average, heavy smokers and a very strong relation was observed for smoking (OR for "ever smoker" = 32.4). Workers having ever been employed in the blast furnace had an excess lung cancer risk (OR = 2.55, 95% CI 1.25-5.21) compared to a reference group of workers not employed in metal producing departments. A similar excess was observed for workers having as their longest held job employment in the blast furnace. A two-fold risk was also observed for workers in the main foundry. For subgroups of workers, tobacco smoking appeared to be an important positive or negative confounder. CONCLUSIONS: In this large Spanish foundry, a high risk was observed for workers employed in departments with high exposure to crystalline silica, PAHs, and various other carcinogenic chemicals. Although comparisons were made between workers of the same industry, smoking habits differed and adjustment by smoking modified considerably the risk estimates.     

Lung cancer and occupation: results of a multicentre case-control study.

The objective of the current study was to estimate the risk of lung cancer attributable to occupational factors and not due to tobacco. At 24 hospitals in nine metropolitan areas in the United States, 1793 male lung cancer cases were matched for race, age, hospital, year of interview, and cigarette smoking (never smoker, ex-smoker, smoker (1-19 and > or = 20 cigarettes per day)) to two types of controls (cancer and non-cancer hospital patients). Information on usual occupation, exposure to specific potential carcinogens, and cigarette smoking was obtained by interview. Risk of lung cancer was increased significantly for electricians; sheetmetal workers and tinsmiths; bookbinders and related printing trade workers; cranemen, derrickmen, and hoistmen; moulders, heat treaters, annealers and other heated metal workers; and construction labourers. All of these occupations are potentially exposed to known carcinogens. Odds ratios (ORs) were increased for exposure to coal dust (adjusted OR = 1.5; 95% confidence interval (95% CI) 1.1-2.1). After stratification, this association was statistically significant only after 10 or more years of exposure. Lung cancer was also related to exposure to asbestos (adjusted OR = 1.8; 95% CI 1.5-2.2). The ORs increased with increasing duration of exposure to asbestos for all smoking categories except for current smokers of 1-19 cigarettes per day. The statistical power to detect ORs among occupations that were previously reported to be at increased risk of lung cancer but that failed to show an OR of at least 1.5 in the current study was small. The cumulative population attributable risk (PAR) of lung cancer due to occupation was 9.2%. It is concluded that occupational factors play an important part in the development of lung cancer independently of cigarette smoking. Because occupations at high risk of lung cancer were under-represented, the cumulative PAR of the present study is likely to be an underestimate of the true contribution of occupation to risk of lung cancer.     

Increased risk of lung cancer among different types of professional drivers in Denmark

OBJECTIVES: To study risk of lung cancer among groups of professional drivers probably exposed to different levels of traffic exhaust fumes. METHODS: A nationwide case-control study (1970-89) based on employees comprising 28,744 men with primary lung cancer and incidence density sampled matched controls (1:1). Employment histories were reconstructed back to 1964 for each study subject from the records of a nationwide pension scheme with compulsory membership. Socioeconomic status was derived from the individual job title taken from the national population registry. Information on tobacco smoking habits was available from historical surveys. Relative risks were estimated by odds ratios (ORs) based on conditional logistic regression analyses. RESULTS: In total 2251 of the male lung cancer cases had been employed as bus, lorry, taxi, or unspecified drivers. No significant difference in tobacco smoking habits was found among professional male Danish drivers and the total employed population. The OR for lung cancer adjusted for socioeconomic status was 1.6 (95% confidence interval (95% CI) 1.2 to 2.2) among taxi drivers, who were considered to be exposed to the highest concentrations of vehicle exhaust fumes, and 1.3 (1.2 to 1.5) for bus and lorry drivers. The OR was 1.4 (1.3 to 1.5) for unspecified drivers. The adjusted risk of lung cancer increased significantly with increasing duration of employment as a driver, and the risk was highest for long term taxi drivers with 10 years of lag time (OR 3.0; 1.2 to 6.8). CONCLUSION: Occupational factors, probably exposure to vehicle exhaust, seems to play an important part in the development of lung cancer among drivers.     

Dust exposure and mortality in chrysotile mining, 1910-75.

We report a further follow-up of a birth cohort of 11 379 workers exposed to chrysotile. The cohort consisted of 10 939 men and 440 women, born 1891-1920, who had worked for at least a month in the mines and mills of Asbestos and Thetford Mines in Quebec. For all subjects, length of service and estimates of accumulated dust exposure were obtained, with a smoking history for the vast majority. Three methods of analysis, two based on the "man-years" methods, the other a "case-and-multiple-controls" approach, gave results consistent with one another and with previous analyses. By the end of 1975, 4463 men and 84 women had died. Among men, the overall excess mortality, 1926-75 was 2% at Asbestos and 10% at Thetford Mines, much the dustier region. The women, mostly employed at Asbestos, had a standardised mortality ratio (SMR) all causes, 1936-75) of 0.90. Analysis of deaths 20 years or more after first employment showed that in men with short service (less than five years) there was no discernible correlation with dust exposure. Among men employed at least 20 years, there were clear excesses in those exposed to the heaviest dust concentrations. Reanalysis in terms of exposure to age 45 showed definite and consistent trends for SMRs for total mortality, for lung cancer, and for pneumoconiosis to be higher the heavier the exposure. The response to increasing dose was effectively linear for lung cancer and for pneumoconiosis. Lung cancer deaths occurred in non-smokers, and showed a greater increase of incidence with increasing exposure than did lung cancer in smokers, but there was insufficient evidence to distinguish between multiplicative and additive risk models. There were no excess deaths from laryngeal cancer, but a clear association with smoking. Ten men and one woman died from pleural mesothelioma. If the only subjects studied had been the 1904 men with at least 20 years' employment in the lower dust concentrations, averaging 6.6 million particles per cubic foot (or about 20 fibres/cc), excess mortality would not have been considered statistically significant, except for pneumoconiosis. The inability of such a large epidemiological survey to detect increased risk at what, today, are considered unacceptable dust concentrations, and the consequent importance of exposure-response models are therefore emphasised.     

Persisting risk of nickel related lung cancer and nasal cancer among Clydach refiners

Objective

To evaluate the risk of lung cancer and nasal cancer among workers employed at the Clydach nickel refinery, South Wales since 1930 by combining data from the two most recently published papers on this cohort.

Methods

Observed and expected numbers of cancer deaths were extracted for workers who had a minimum of five years service and were employed for the first time between 1902 and 1992. Standardised mortality ratios (SMR) were calculated for subgroups according to year of employment, time since first employment, and process work.

Results

A persisting excess of respiratory cancer was found for workers employed in the period 1930–92, with a lung cancer SMR of 133 (95% CI 103 to 172) and a SMR for nasal cancer of 870 (95% CI 105 to 3141). The lung cancer excess was most clearly seen 20 years or more after first employment and seemed to be confined to process workers. There was no indication of a further reduction in risk since 1930.

Conclusion

The extreme nickel related cancer hazard at the refinery before 1920 was greatly reduced during subsequent years. Some of the carcinogenic exposures seem to have remained after 1930, producing an elevated risk of nasal cancer and a 30% excess of lung cancer in the workforce. There was evidence of a persisting risk among process workers first employed since 1953.