Different measures of asbestos exposure in estimating risk of lung cancer and mesothelioma among construction workers

To analyze occupation, expert-evaluated cumulative exposure, and radiographic abnormalities as indicators of asbestos-related cancer risk we followed 16,696 male construction workers for cancer in 1990-2000. We calculated standardized incidence ratios (SIR) in comparison to the Finnish population and relative risks (RR) in a multivariate analysis in comparison to the internal low-exposure category of each indicator. Overall, the risk was increased for mesothelioma (SIR 2.0, 95% CI = 1.0-3.3), but not for lung cancer (SIR 1.1, 95% CI = 0.9-1.2). Radiographic lung fibrosis indicated a 2-fold and a high value of the exposure index a 3-fold RR of lung cancer, while there was no risk among those with pleural plaques. The risk of lung cancer was the highest in insulators (RR 3.7, 95% CI = 1.4-9.9). Occupation, expert-evaluated cumulative exposure, and lung fibrosis are useful indicators of lung cancer risk among construction workers.     

Association between pleural plaques and coronary heart disease.

OBJECTIVE: The aim of this study was to verify a clinical impression that patients with coronary heart disease disproportionately frequently have calcified pleural plaques. METHODS: Chest X-rays were collected from 148 patients referred consecutively to the Helsinki University Central Hospital for coronary angiography and from 100 consecutive lung cancer patients seen at the same hospital. The radiographs were analyzed for the presence of calcified pleural plaques according to the classification the International Labour Office. A generalized linear model with binomial distribution and log link was used to estimate the relative risks and their 95% confidence intervals (95% CI). RESULTS: The prevalence of calcified pleural plaques was 35% for the coronary patients and 19% for the lung cancer patients. Calcified pleural plaques were more common among the men than the women, and the risk increased with age. The relative risk of calcified pleural plaques, adjusted for age and gender, was 2.19 (95% CI 1.44-3.32) for the coronary patients as compared with the lung cancer patients. CONCLUSIONS: Further studies with better information on past exposure to asbestos and other potential risk factors are warranted to confirm the observations and to examine whether the association between coronary heart disease and calcified pleural plaques is related to an etiologic or an individual susceptibility factor common to both of these conditions.     

Asbestos exposure,pleural plaques and the risk of lung cancer

Summary Studies which have evaluated the relationship between pleural plaques and smoking have found a higher prevalence of smokers among persons with pleural plaques. Pleural plaques are a relatively frequent finding among persons with occupational exposure to asbestos. Some studies, but not others, have shown that persons with pleural plaques have a higher risk of lung cancer. None of these studies controlled for the effects of smoking, and since smoking is more prevalent among persons with pleural plaques, it is unlikely that the increased risk of lung cancer to persons with pleural plaques, found in some studies, is due to the pleural plaques.     

The Occupational Cancer Incidence Surveillance Study (OCISS): risk of lung cancer by usual occupation and industry in the Detroit metropolitan area

This case-referent study assesses occupational risk factors associated with lung cancer, utilizing colon and rectum cancer referents. Complete occupational and tobacco use histories were obtained by telephone interview for 5,935 incident lung cancer cases and 3,956 incident colon and rectum cancer referents. The analysis included 43 usual occupational groups and 48 usual industry groups comprised of at least 10 cases. Among all cases, there were significant elevated risks for excavating and mining workers (OR = 4.01), furnace workers (OR = 3.11), armed services personnel (OR = 3.10), agricultural workers (OR = 2.05), driver sales (OR = 2.21), mechanics (OR = 1.72), painters (OR = 1.96), and drivers (OR = 1.88). Industries with significant elevated lung cancer risk included farming (OR = 2.21), mining (OR = 2.98), and primary ferrous metals manufacturing (OR = 2.43). Analyses of white and black men separately revealed that the excess of lung cancer among mechanics is restricted to black males (OR = 4.16). The risk of lung cancer among armed services personnel is higher among black men (OR = 10.54) than among white men (OR = 3.06). Five of the occupations observed more often among lung cancer cases have probable exposure to diesel exhaust.     

Occurrence of pleural plaques in workers with exposure to mineral wool

The objective of this study was to investigate whether occurrence of pleural plaques is associated with exposure to mineral wool. The occurrence of pleural plaques on routine chest radiographs of 933 persons employed in the mineral wool manufacturing industry and 865 referents was compared. Twelve men from the mineral wool industry had pleural plaques, as against three of the referents (P > 0.05). The occurrence of pleural plaques among men in the mineral wool industry was not associated with an increased exposure to mineral wool or with length of time between start of employment and time of chest radiograph. The results do not support the notion that inhalation of man-made mineral fibers causes pleural plaques. It must, however, be conceded-keeping in mind the limits imposed by the study size-that nor do they provide grounds for refutation of such a hypothesis.     

A case control study of lung cancer in Florence, Italy. II. Effect of migration from the south.

Risk of lung cancer related to region of birth in Italy was investigated among migrants to Florence, in a case control study of all histologically confirmed incident cases of primary lung cancer in a three year period in that city (n = 376). Controls (n = 892) were patients in the same hospital of similar age, sex, date of admission, and smoking status with discharge diagnoses other than lung cancer or suicide. Information on place of birth and year of migration to Florence was collected directly from each subject, along with a detailed occupational history. Logistic regression models were used to calculate the odds ratio for birth in the south of Italy relative to birth elsewhere. Male migrants from the south have an odds ratio of lung cancer of 0.5 (95% limits 0.3 to 0.7) relative to those born elsewhere. This "protective effect" is not explained by smoking or by any known occupational risk. The risk is lowest among those born on the island of Sicily (odds ratio 0.2 compared to those born in the centre-north).     

Mortality and cancer morbidity in cohorts of asbestos cement workers and referents.

Total and cause specific mortality and cancer morbidity were studied among 1929 asbestos cement workers with an estimated median cumulative exposure of 2.3 fibre (f)-years/ml (median intensity 1.2 f/ml, predominantly chrysotile). A local reference cohort of 1233 industrial workers and non-case referents from the exposed cohort were used for comparisons. The risk for pleural mesothelioma was significantly increased (13 cases out of 592 deaths in workers with at least 20 years latency). No case of peritoneal mesothelioma was found. A significant dose response relation was found for cumulative exposure 40 years or more before the diagnosis, with a multiplicative relative risk (RR) of 1.9 for each f-year/ml. No relation was found with duration of exposure when latency was accounted for. There was a significant overrisk in non-malignant respiratory disease (RR = 2.6). The overall risks for respiratory cancer, excluding mesothelioma, and for gastrointestinal cancer were not significantly increased. Surprisingly, colorectal cancer displayed a clear relation with cumulative dose, with an estimated increase of 1.6% in the incidence density ratio for each f-year/ml (but not with duration of exposure).     

Mortality and cancer morbidity in cohorts of asbestos cement workers and referents

Total and cause specific mortality and cancer morbidity were studied among 1929 asbestos cement workers with an estimated median cumulative exposure of 2.3 fibre (f)-years/ml (median intensity 1.2 f/ml, predominantly chrysotile). A local reference cohort of 1233 industrial workers and non-case referents from the exposed cohort were used for comparisons. The risk for pleural mesothelioma was significantly increased (13 cases out of 592 deaths in workers with at least 20 years latency). No case of peritoneal mesothelioma was found. A significant dose response relation was found for cumulative exposure 40 years or more before the diagnosis, with a multiplicative relative risk (RR) of 1.9 for each f-year/ml. No relation was found with duration of exposure when latency was accounted for. There was a significant overrisk in non-malignant respiratory disease (RR = 2.6). The overall risks for respiratory cancer, excluding mesothelioma, and for gastrointestinal cancer were not significantly increased. Surprisingly, colorectal cancer displayed a clear relation with cumulative dose, with an estimated increase of 1.6% in the incidence density ratio for each f-year/ml (but not with duration of exposure).     

Lung cancer development in primary smelter workers: a nested case-referent study

OBJECTIVE: The objective of this study was to study the impact of work-related exposure to mainly arsenic and lead versus smoking in primary smelter workers developing lung cancer. METHODS: In a cohort of 3979 primary smelter workers, 46 subjects had contracted respiratory malignancies. They were compared with 141 age-matched male referents by conditional logistic regression analysis. RESULTS: Cases showed a significantly higher smoking rate as compared with referents: odds ratio (OR) = 4.0; 95% confidence interval (CI) = 1.6-10.1; P = 0.003. When restricted to smokers (33 cases, 63 referents), the cumulative air arsenic exposure index, but not the lead exposure indices, was significantly higher among the cases: OR = 1.07; 95% CI = 1.02-1.11; P = 0.005. CONCLUSIONS: Cumulative arsenic exposure and smoking were identified as risk factors for the development of lung cancer; lead exposure, however, was not.     

A case control study of lung cancer in Florence, Italy. I. Occupational risk factors.

A case control study of lung cancer in Florence, Italy was performed to investigate occupational risk factors for both men and women. The case series (n = 376) comprised all incident, histologically confirmed cases of primary lung cancer occurring in a three year period. Controls (n = 892) were patients in the same hospital of similar age, sex, date of admission, and smoking status with discharge diagnoses other than lung cancer or suicide. A detailed occupational history was collected from each subject directly. Logistic regression models were used to calculate odds ratios for specific occupations compared to all others. Among men, the lung cancer risk for bricklayers using firebrick and other refractory materials was elevated (adjusted odds ratio 6.5, 95% limits 2.1 and 20.9). Female hat makers, probably exposed to arsenic while making felt hats, had an elevated risk of lung cancer (6 cases versus 0 controls, p = 0.01). Risks in other occupations are discussed.     

A case-referent study of lung cancer, occupational exposures and smoking. I. Comparison of title-based and exposure-based occupational information

The role of occupational exposures and smoking in the development of lung cancer has been studied among 176 male incident lung cancer cases and 176 referents admitted to two county hospitals in southeast Norway during 1979-1983. After the allocation of all occupational titles in the Nordic Classification of Occupations into three exposure groups according to potential exposure to respiratory carcinogens and other contaminants, each subject was classified according to exposure status of main occupation and number of years in each exposure category. An excess risk of lung cancer was observed both among those in possibly exposed occupations and among those definitely exposed. A more than threefold excess risk was observed among subjects with more than 30 years in exposed occupations. Exposure to 22 agents/processes was further assessed by a separate questionnaire and estimated simultaneously in a logistic regression model. Elevated risks were associated with exposure to asbestos and several other agents/processes, which largely correlated to each other. Smoking was strongly associated with all histological subtypes of lung cancer, while for occupational exposures the risk ratio was highest for small cell carcinoma and lowest for adenocarcinoma. Very high risk ratios for lung cancer were observed among heavy smokers in exposed occupations.     

Cancer mortality and incidence of mesothelioma in a cohort of wives of asbestos workers in Casale Monferrato, Italy

BACKGROUND: Family members of asbestos workers are at increased risk of malignant mesothelioma (MM). Although the hazard is established, the magnitude of the risk is uncertain, and it is unclear whether risk is also increased for other cancers. Few cohort studies have been reported. OBJECTIVE: The "Eternit" factory of Casale Monferrato (Italy), active from 1907 to 1986, was among the most important Italian plants producing asbestos-cement (AC) goods. In this article we present updated results on mortality and MM incidence in the wives of workers at the factory. METHODS: We studied a cohort of 1,780 women, each married to an AC worker during his employment at the factory but not personally occupationally exposed to asbestos. Cohort membership was defined starting from the marital status of each worker, which was ascertained in 1988 from the Registrar's Office in the town where workers lived. At the end of follow-up (April 2003), 67% of women were alive, 32.3% dead, and 0.7% lost to follow-up. Duration of exposure was computed from the husband's period of employment. Latency was the interval from first exposure to the end of follow-up. RESULTS: The standardized mortality ratio (SMR) for pleural cancer [21 observed vs. 1.2 expected; SMR = 18.00; 95% confidence interval (CI), 11.14-27.52] was significantly increased. Mortality for lung cancer was not increased (12 observed vs. 10.3 expected; SMR = 1.17; 95% CI, 0.60-2.04). Eleven incident cases of pleural MM were observed (standardized incidence ratio = 25.19; 95% CI, 12.57-45.07). CONCLUSIONS: Household exposure, as experienced by these AC workers' wives, increases risk for pleural MM but not for lung cancer.     

Exposure to titanium dioxide and risk of lung cancer in a population-based study from Montreal

OBJECTIVES: This study assessed the lung cancer risk from exposure to titanium dioxide, an important pigment with limited evidence of carcinogenicity in experimental animals but sparse data for humans. METHODS: The risk of lung cancer among residents in Montreal, Canada, was analyzed, including 857 histologically confirmed cases of lung cancer diagnosed during 1979-1985 among men aged 35-70 years and a group of referents comprising 533 randomly selected, healthy residents and 533 persons with cancer in organs other than the lung. Exposure to titanium dioxide and other titanium compounds was assessed by a team of industrial hygienists on the basis of a detailed occupational questionnaire. RESULTS: Thirty-three cases and 43 referents were classified as exposed to titanium dioxide. The odds ratio was 0.9 [95% confidence interval (95% CI) 0.5-1.5]. No trend was apparent according to the estimated frequency, level, or duration of exposure. The odds ratio was 1.0 (95% CI 0.3-2.7) for medium or high exposure for at least 5 years. Few subjects were classified as exposed to titanium dioxide fumes or to other titanium compounds, but the risk of lung cancer was nonsignificantly increased for exposure to these agents. CONCLUSIONS: Although misclassification of exposure and low exposure prevalence might have resulted in false negative results, this study does not suggest that occupational exposure to titanium dioxide increases the risk of lung cancer.     

Increased risk for primary liver cancer among women exposed to solvents

An earlier case-referent study by the same authors [Int Arch Occup Environ Health 54 (1984) 147-153] reported that solvent-exposed women, but not men, had an increased risk for primary liver cancer. The present study was undertaken to verify these results. The relatives of deceased patients, ie, 377 liver cancer cases, 385 coronary infarction referents, and 476 stomach cancer referents, responded to a questionnaire on past employment and potentially relevant covariables, the response rates being 71.7, 72.7, and 69.0%, respectively. The information was assessed for solvent exposure by two occupational hygienists without knowledge of the patients' diagnoses. Seven male and seven female liver cancer cases had been exposed to solvents, the odds ratio being less than 1 for the men but greater than 3 for the women irrespective of the reference group used for comparison. The results confirm the authors' earlier findings. When both materials were combined, the odds ratio was 7.8 for the female liver cancer cases as compared with the infarction referents. In the combined material, nine female liver cancer cases, two stomach cancer referents, but no infarction referent had had at least probable exposure to chlorinated hydrocarbons. Such exposure was rare among all of the men in the study. This finding may explain why the increased liver cancer risk occurred only for the women, although a sex difference in sensitivity cannot be completely ruled out.     

Lung cancer risk and welding: Results from a case-control study in Germany

In a case-control study, 839 male hospital-based cases of primary lung cancer and the same number of population-based controls—matched by sex, age, and region of residence—were personally interviewed for their job and smoking histories. The study allows to quantify occupational asbestos exposure that was thought to be a welding-associated risk: 6% of cases and 2% of controls were classified into the occupational category “welders or burners” (odds ratio [OR] = 2.65). This OR was reduced to 1.93 (95% confidence limit [CL]: 1.03–3.61) after adjustment for smoking and asbestos. In contrast, a history of welding in general for at least a half-year is 28% among cases and 23% among controls, yielding an OR of 1.25 (95% CL: 0.94–1.65) after adjustment for both confounders. The OR of welding for more than 6,000 hr is 1.45 (95% CL = 1.04–2.02), reduced to 1.10 after adjustment for smoking and asbestos. Oxyacetylene welding for more than 6,000 hr lifelong is associated with an OR of 1.86 (95% CL = 1.01–3.43) reduced to 1.46 (n.s.) after adjustment for smoking and asbestos. The risk of oxyacetylene welding seems to be highest for oat cell carcinoma with an adjusted OR for ever-exposure of 1.46 (95% CL = 0.69–3.10). Therefore, the present study supports the hypothesis that some, but not all, of the excess risk of welders observed in the literature may be due to a history of cigarette smoking and occupanional asbestos exposure. The elevated risk for the subgroup of employees in the aircraft industry reported for the midterm evaluation of the study still prevails, though no longer statistically significant. However, employees in this industry who ever welded show an OR of 2.29 (95% CL = 1.19–4.42) after adjustment for smoking and asbestos. Am. J. Ind. Med. 33:313–320, 1998. © 1998 Wiley-Liss, Inc.     

Occupational risk factors for lung cancer among young men

OBJECTIVES: This study evaluated whether occupational exposure plays a role for lung cancer at a very young age. METHODS: In a pooled analysis of 2 German case-referent studies including 3498 incident cases among men and 3541 male population referents, a group of men (187 cases and 202 referents) aged > or =45 years was compared with a group of 2186 cases and 2146 referents aged 55-69 years. Occupational exposure to known (A list) or suspected (B list) lung carcinogens was assessed using job and industry codes, and exposure to asbestos was assessed using job-specific supplementary questionnaires. A conditional logistic regression was used to calculate the odds ratios (OR) and to control for smoking. RESULTS: Asbestos exposure showed an odds ratio (OR) of 2.39 [95% confidence interval (95% CI) 1.41-4.04] for the younger group and 1.46 (95% CI 1.24-1.72) for the older group. Having ever worked in a job belonging to the A list as compared with never working in an A- or B-list job was associated with a significantly increased risk for the younger (OR 2.06, 95% CI 1.03-4.12) and older (OR 1.35, 95% CI 1.10-1.65) groups, adjusted for asbestos. Lung cancer risk for those working in A-list jobs at a very young age (under 16 years) was increased in the younger group (OR 6.14, 95% CI 1.41-28.01) in contrast to the older group (OR 1.19, 95% CI 0.91-1.63). CONCLUSION: Occupational risk factors play an important role for lung cancer among young men. Early age at first exposure may favor an early age of the onset of lung cancer.     

Relationship of epithelial ovarian cancer to other malignancies within families

The relationship of family history of cancer of the breast, colon/rectum, cervix, endometrium, lung, and thyroid to the risk of epithelial ovarian cancer was investigated in a large population-based case-control study. The data consisted of family histories from 493 epithelial ovarian cancer cases and 2,465 controls aged 20-54 years. After controlling for potential confounders, risk for epithelial ovarian cancer was found to be significantly elevated among women reporting breast cancer and colo/rectal cancer in a first-degree relative. Adjusted odds ratios were 1.5 (95% CI = 1.1-2.1) and 1.9 (95% CI = 1.1-3.3), respectively. None of the remaining four types of cancer was found to be statistically associated with the risk of epithelial ovarian cancer. However, when histologic subtypes of epithelial ovarian cancer were considered, a family history of breast cancer was found to be associated with an elevated risk of endometrioid ovarian cancer (odds ratio = 2.3; 95% CI = 1.1-4.7), as was a family history of endometrial cancer (odds ratio = 2.7; 95% CI = 1.0-6.9). The results are considered in the context of other studies of familial patterns of cancer and are compared with published findings concerning the occurrence of multiple primary cancers in the same individual. The findings indicate that further study is warranted regarding possible genetic relationships between epithelial ovarian cancer and cancers arising in other organs.     

Cancer incidence among members of the Norwegian trade union of insulation workers

Insulation work has been described as an occupation with high exposure to asbestos. A cohort of members of the Norwegian Trade Union of Insulation Workers (n = 1116), hired between 1930 and 1975, was established. During 2002, the cohort was linked to the Cancer Registry of Norway. The standardized incidence ratio (SIR) of pleural mesothelioma was 12.9 (95% confidence interval [CI] = 6.0-24.6). Two cases with peritoneal mesotheliomas were found (SIR, 14.8; 95% CI = 1.8-53.4). The SIR of lung cancer was 3.0 (95% CI = 2.3-3.8). Four cases of lung cancer were observed among cork workers without any exposure to asbestos, but to cork dust and tar smoke (SIR, 5.3; 95% CI = 1.5-13.6). Our study showed a high risk of mesothelioma and an elevated risk of lung cancer among members of the Trade Union of Insulation Workers.     

Railways and asbestos in Japan (1928-1987)--epidemiology of pleural plaques, malignancies and pneumoconioses-

Asbestos has been an indispensable insulating material for railway industries, especially steam locomotives (SLs). This review (1928-1987) consists of three parts. 1) Pleural plaques: Since the 1970s, pleural plaques have been regarded as evidence of past asbestos inhalation, and more recently recognized as a risk factor of asbestos-related malignancies. For diagnostic criteria on plain radiographs, the modified ILO 1980 International Classification of Radiographs of Pneumoconioses was used. Most cases had pleural plaques with normal lungs. Large plant workers showed a significantly higher rate of plaques than workers in smaller plants. Bilateral plaques were dominant followed by the left, then the right lung, and chest wall plaques were dominant over the diaphragm. The manifestation of pleural plaques was more correlated to years since the onset of the asbestos exposure than the sum of asbestos work years, although the result was not significant. The boilermen of railway ferry steamers had a significantly higher plaque rate than other seamen. CT studies on plaques started in 1978. 2) Asbestos-related malignancies: Five retrospective cohort studies 1960-1970 were made on primary lung cancer incidence and mortality among 350,000 active railway men with smoking information. The follow-up period was 20 yr at the longest. Almost all plant workers showed a tendency of higher incidence or mortality than the controls. Two cases of mesothelioma were reported in 1980. 3) Pneumoconioses: Most studies (1928-1975) had relatively low prevalence rates among SL-related workers.     

Evidence for excess colorectal cancer incidence among asbestos-exposed men in the Beta-Carotene and Retinol Efficacy Trial

The relation between asbestos exposure and colorectal cancer remains controversial. The authors of this 1984-2004 US study examined the association among 3,897 occupationally exposed participants in the Beta-Carotene and Retinol Efficacy Trial (CARET) for chemoprevention of lung cancer, followed prospectively for 10-18 years. When a Cox stratified proportional hazards model was used, risks of colorectal cancer were elevated among male heavy smokers exposed to asbestos. Their relative risk was 1.36 (95% confidence interval: 0.96, 1.93) when compared with that for CARET heavy smokers not exposed to asbestos, after adjusting for age, smoking history, and intervention arm. The presence of asbestos-induced pleural plaques at baseline was associated with a relative risk of 1.54 (95% confidence interval: 0.99, 2.40); colorectal cancer risk also increased with worsening pulmonary asbestosis (p = 0.03 for trend). A dose-response trend based on years of asbestos exposure was less evident. Nonetheless, these data suggest that colorectal cancer risk is elevated among men occupationally exposed to asbestos, especially those with evidence of nonmalignant asbestos-associated radiographic changes.