Cancer mortality in the asphalt industry: a ten year follow up of an occupational cohort

A historical cohort study was conducted to study the possible risk of cancer associated with exposure to asphalt. Altogether 1320 unskilled workers employed in the asphalt industry were followed up over a ten year period and compared with 43,024 unskilled men in terms of cause specific mortality. Both groups were identified from census records and followed up by an automatic record link that had been established previously between the census register, National Register, and Death Certificate Register. The cancer mortality was significantly increased in asphalt workers aged 45 or more, when five years' latency from enrolment into the study was allowed for (SMR for cancer: 159, 95% confidence interval: 106-228). Non-significant increases were seen for respiratory, bladder, and digestive cancers but a significant increase was seen for brain cancer (SMR = 500, 95% CI: 103-1461). Components of asphalt fumes may have been important to the observed association between risk of cancer and employment in the asphalt industry.     

A mortality study of Danish stokers.

This study was set up to investigate whether work as a stoker is associated with an increased risk of specific malignant neoplasms. For this purpose, a cohort of 2777 male stokers was followed up through a 10 year period with regard to cause specific mortality. Comparisons were made with another cohort of unskilled male workers in physically demanding jobs. The mortality of the stokers was significantly increased for lung cancer (standardised mortality ratio (SMR) 145, 95% confidence interval (95% CI) 110-186) and for multiple myeloma (SMR 388, 95% CI 106-994). Also, increases were seen for cancer of the urinary organs and cancer of the mouth and throat. The combustion products to which the stokers have been exposed comprise several carcinogenic agents including polycyclic aromatic hydrocarbons, benzene, arsenic, and radionuclides. It seems likely that the occupational exposure of stokers has contributed to their excess cancer mortality.     

A mortality study of Danish stokers.

This study was set up to investigate whether work as a stoker is associated with an increased risk of specific malignant neoplasms. For this purpose, a cohort of 2777 male stokers was followed up through a 10 year period with regard to cause specific mortality. Comparisons were made with another cohort of unskilled male workers in physically demanding jobs. The mortality of the stokers was significantly increased for lung cancer (standardised mortality ratio (SMR) 145, 95% confidence interval (95% CI) 110-186) and for multiple myeloma (SMR 388, 95% CI 106-994). Also, increases were seen for cancer of the urinary organs and cancer of the mouth and throat. The combustion products to which the stokers have been exposed comprise several carcinogenic agents including polycyclic aromatic hydrocarbons, benzene, arsenic, and radionuclides. It seems likely that the occupational exposure of stokers has contributed to their excess cancer mortality.     

Mortality of mastic asphalt workers

This study was conducted to investigate the adverse health effects of exposure to bitumen fumes. A cohort of 679 mastic asphalt workers was followed from 1959 to 10 June 1986, during this period 169 deaths occurred. The overall standardized mortality ratio (SMR) was 163 (95% confidence interval (95% CI) 141-190), the SMR was 225 (95% CI 172-288) for cancer and 223 (95% CI 130-358) for external causes. Among persons aged 40 to 89 years, significant increases were seen for lung cancer (SMR 290, 95% CI 188-429), nonpulmonary cancer (SMR 200, 95% CI 141-276), and liver cirrhosis (SMR 467, 95% CI 188-962). Bronchitis, emphysema, and asthma also occurred in excess (SMR 207, 95% CI 95-393). In conclusion, the inhalation of bitumen fumes may have contributed to the elevated mortality from cancer and respiratory diseases among mastic asphalt workers.     

High mortality in lower salaried Norwegian men: the healthy worker effect?

STUDY OBJECTIVE--This study aimed to examine whether the high mortality in lower salaried men in Norway was related to an inflow into this group of unskilled workers with high mortality. DESIGN--Individual information on occupation was derived from the 1970 and the 1980 censuses and linked to mortality data for the period 1980-5 by the official, individual identification numbers. PARTICIPANTS--The study population included Norwegian men aged 20-64 years in 1980. All men enumerated in the 1980 census (and who were registered in the 1970 census) within the two occupational groups, unskilled workers and lower salaried employees, were included. MEASUREMENTS AND MAIN RESULTS--The subjects were allocated to the two occupational groups according to the official Norwegian classification of socioeconomic status. Mortality was measured by standardised mortality ratios (SMR). The findings suggest that a fairly large number of unskilled workers with high mortality move into the lower salaried employee group. This transition produces a higher SMR in lower salaried employees and, simultaneously, an artificially but modestly lower SMR in unskilled workers. The difference in SMR between the two groups is thereby exaggerated by 44%. The difference among the elderly was smaller. CONCLUSION--Occupational mobility consistent with "the healthy worker effect" increases the SMR of lower salaried men and, at the same time, reduces slightly the SMR of unskilled workers.     

Epidemiologic study of cancer mortality among Israeli asphalt workers

BACKGROUND: We describe the results of a cancer mortality study among asphalt workers in Israel. METHODS: Personal identifiers and employment histories of 2,176 workers were extracted from company records. RESULTS: Mortality from all malignant neoplasms was significantly reduced in the whole cohort (SMR 0.68, 95% confidence interval (CI) 0.56-0.83). SMR for lung cancer was elevated in workers exposed to bitumen (SMR 1.05, 95% CI 0.62-1.66). No significant elevation or reduction in mortality was observed in relation to a specific site. SMRs for lung cancer was higher among ever exposed to bitumen than among unexposed. There was no association between lung cancer risk and estimated exposure to bitumen fume, and no dose-response was apparent. CONCLUSIONS: While the results of this cohort study indicate a slightly increased SMR for lung cancer, it did not produce evidence of a causal link between lung cancer and exposure to bitumen fume.     

Mortality of auto mechanics. A ten-year follow-up

This study was set up to investigate whether work in car repair workshops is associated with an increased risk of ischemic heart disease and specific malignant neoplasms. For this purpose, a cohort of auto mechanics has been followed through 10 years with regard to cause-specific mortality. Comparisons were made with another cohort of skilled male workers who were not exposed to asbestos or petrochemical substances. The auto mechanics' mortality was increased for ischemic heart disease [standardized mortality ratio (SMR) 121, 95% confidence interval (95% CI) 102-145], other cardiovascular diseases (SMR 112, 95% CI 82-150), cancer (SMR 115, 95% CI 97-136), other diseases (SMR 119, 95% CI 94-149), and external causes (SMR 131, 95% CI 113-153). For specific cancer sites, increases were seen for pancreatic cancer, urinary cancer outside the bladder, and pleural mesothelioma.     

Cancer mortality among European asphalt workers: an international epidemiological study. I. Results of the analysis based on job titles

BACKGROUND: Inhalation of bitumen fumes is potentially carcinogenic to humans. METHODS: We conducted a study of 29,820 male workers exposed to bitumen in road paving, asphalt mixing and roofing, 32,245 ground and building construction workers unexposed to bitumen, and 17,757 workers not classifiable as bitumen workers, from Denmark, Finland, France, Germany, Israel, the Netherlands, Norway, and Sweden, with mortality follow-up during 1953-2000. We calculated standardized mortality ratios (SMRs) and 95% confidence intervals (CIs) based on national mortality rates. Poisson regression analyses compared mortality of bitumen workers to that of building or ground construction workers. RESULTS: The overall mortality was below expectation in the total cohort (SMR 0.92, 95% CI 0.90-0.94) and in each group of workers. The SMR of lung cancer was higher among bitumen workers (1.17, 95% CI 1.04-1.30) than among workers in ground and building construction (SMR 1.01, 95% CI 0.89-1.15). In the internal comparison, the relative risk (RR) of lung cancer mortality among bitumen workers was 1.09 (95% CI 0.89-1.34). The results of cancer of the head and neck were similar to those of lung cancer, based on a smaller number of deaths. There was no suggestion of an association between employment in bitumen jobs and other cancers. CONCLUSIONS: European workers employed in road paving, asphalt mixing and other jobs entailing exposure to bitumen fume might have experienced a small increase in lung cancer mortality risk, compared to workers in ground and building construction. However, exposure assessment was limited and confounding from exposure to carcinogens in other industries, tobacco smoking, and other lifestyle factors cannot be ruled out.     

A follow-up study on the mortality of truck drivers

The aim of this study was to investigate a possible relationship between occupational exposure to vehicle exhaust and cancer risk. For this purpose, a cohort of 14,225 truck drivers was followed throughout a ten-year period with regard to cause-specific mortality. Comparisons were made with another cohort of unskilled male laborers. Both of the occupational groups compared were identified at a census and no supplementary data on individual exposure history were available. The study showed an increased mortality for lung cancer (standardized mortality ratio (SMR) 160, 95% confidence interval (CI) 126–200) and multiple myeloma (SMR 439, 95% CI 142–1,024). It seems likely that exposure to diesel exhaust has contributed to the increased lung cancer risk observed. The possible relationship between multiple myeloma and certain constituents of vehicle exhaust may be worth attention in future investigations. © 1993 Wiley-Liss, Inc.     

Cohort mortality study among French asphalt workers

BACKGROUND: In conjunction with the European cohort study among asphalt workers coordinated by the International Agency for Research on Cancer (IARC), we studied the mortality of 15,011 French men who were followed for 17 years for a total of 175,062 persons-years. This group contained 2,506 subjects who had ever been employed as asphalt workers: they contributed 30,692 person-years of risk. A reference group was composed of 6,675 subjects (i.e., 61,856 persons-years) who had been employed only in building or ground construction. METHODS: Mortality ratios standardized for age and period were computed with their 95% confidence intervals (CI) from the age and period mortality rates of all French men for the years covered by the study (1979-1996). We also compared the mortality of exposed workers and the reference group with Poisson regression models after adjustment for age, calendar period, and either duration of employment or length of follow-up. RESULTS: Mortality from lung cancer was equivalent to the expected rate [SMR = 1.01 95% CI (0.6-1.6)], but was 40% greater than among the non-exposed reference group [RR = 1.4 95% CI (0.7-2.8)]. We also found an excess of gastrointestinal cancers, especially of the esophagus [SMR = 1.94, 95% CI (0.9-3.6)] and stomach [SMR = 2.2, 95% CI (0.8-4.7)]. Comparison with the internal reference group confirmed these findings, especially for stomach cancer [RR = 2.8, 95% CI (0.7-11.4)]. CONCLUSIONS: Although our results are not statistically significant, they suggest that road-paving workers may have a slightly higher rate of lung cancer and a moderately higher rate of stomach cancer than their non-exposed counterparts. The excess of lung cancer may be due to potential confounding factors, including the occupational risk factor of coal tar exposure and the lifestyle risk factor of smoking. A nested case-control study is under way that will make it possible to control for smoking and other potential carcinogenic exposures; this is necessary before any definitive conclusions can be drawn.     

A cohort mortality study of employees in the U.S. carbon black industry

OBJECTIVES: The objectives of this study are to evaluate historical mortality patterns, especially due to cancers, among employees of the U.S. carbon black industry and to address the methodological shortcomings of previous U.S. mortality studies. METHODS: We followed mortality of 5011 workers employed 1 year or more since the 1930s at 18 carbon black facilities through December 31, 2003. Age-, race-, sex-, and calendar year-adjusted standardized mortality ratios (SMRs) were calculated using state-specific mortality rates. RESULTS: Follow up was 96% complete. All-cause (SMR = 0.74, 95% confidence interval [CI] = 0.70-0.78) and all-cancer mortality (SMR = 0.83, 95% CI = 0.74-0.92) showed significant deficits. No excess was observed from lung (SMR = 0.97, 95% CI = 0.82-1.15) or bladder (SMR = 0.93, 95% CI = 0.47-1.87) cancers or from nonmalignant respiratory diseases (SMR = 0.99, 95% CI = 0.83-1.18). No trends were seen with duration of employment or time since hire for any cause of death. CONCLUSION: Employment in carbon black production in the United States seems not to be associated with increased mortality overall, cancer overall and, in particular, lung cancer. Further research, however, incorporating a detailed exposure assessment is needed to determine whether exposure to carbon black at high levels may be associated with an increased risk of cancer.     

A retrospective cohort study of male workers exposed to PVA fibers

In order to ascertain whether PVA fibers can produce cancer in humans or not, we have conducted a retrospective cohort study of workers exposed to PVA fibers. A total of 447 exposed and 2416 non-exposed male workers who were engaged before 1980 were followed up until the end of 1996. The SMR for all causes was 0.57 (observed 38, 95% CI: 0.41-0.78) for the exposed, and 0.66 (observed 210, 95% CI: 0.58-0.75). As for lung cancer, its SMR was 0.77 (observed 3, 95% CI: 0.15-2.24) for the exposed workers and 0.67 (12 observed, 95% CI: 0.34-1.16) for the non-exposed workers. Lung cancer SMR was 0.86 (observed 2, 95% CI: 0.10-3.11) for the workers with 20 or more years' employment. This study showed no difference in lung cancer risk between the workers exposed to PVA fibers and the non-exposed workers.     

Risk of gastric cancer in pneumoconiotic coal miners and the effect of respiratory impairment.

OBJECTIVES--This study was carried out to investigate the mortality patterns in a group of 3790 coal miners. The study population had abnormal chest x ray films at a routine medical examination that was performed in the 1950s. METHODS--The total group of 3790 coal miners were followed up for mortality up to 1 January 1992. Causes of death, determined and coded at time of death, were traced with help from the Central Bureau of Statistics. RESULTS--Total mortality in this group of coal miners with abnormal chest x ray films was significantly higher than expected (SMR 127.1, 95% CI 122.5-131.6), mainly a reflection of the increase in mortality from non-malignant respiratory disease (SMR 411.0, 95% CI 382.3-441.3). Mortality from gastric cancer was also significantly increased (SMR 147.5, 95% CI 122.3-176.3). This risk of mortality from gastric cancer was confined to workers with no pneumoconiosis or only a mild form. Despite the strong relation to duration of employment and pneumoconiosis the group of workers with more severe manifestations of pneumoconiosis did not experience an excess in mortality from gastric cancer. CONCLUSION--This study confirms the earlier reported risk of gastric cancer in coal miners. Also it confirms the hypothesis that this risk of gastric cancer is limited to workers with a mild degree of pneumoconiosis or none. In workers with severe forms of pneumoconiosis the pulmonary clearance system is impaired in such a way that the inhaled coal dust does not reach the digestive tract.     

Cancer mortality among European asphalt workers: an international epidemiological study. II. Exposure to bitumen fume and other agents

BACKGROUND: An increased risk of lung cancers among asphalt workers has been suggested in epidemiological studies based on large scale statistical analyses. METHODS: In a multi-country study of 29,820 male workers employed in road paving, asphalt mixing and roofing, 32,245 ground and building construction workers and 17,757 other workers from Denmark, Finland, France, Germany, Israel, the Netherlands, Norway, and Sweden, with mortality that was documented from 1953-2000. Exposures to bitumen fume, coal tar, 4-6 ring polycyclic aromatic hydrocarbons, organic vapor, diesel exhaust, asbestos, and silica dust were assessed via a job-exposure matrix. Standardized mortality ratios (SMRs) and 95% confidence intervals (CIs) based on national mortality rates, as well as relative risks (RRs) based on Poisson regression models were calculated. RESULTS: The SMR of lung cancer among workers exposed to bitumen fume (1.08, 95% CI 0.99-1.18) was comparable to that of non-exposed workers (SMR 1.05, 95% CI 0.92-1.19). In a sub-cohort of bitumen-exposed workers without exposure to coal tar, the SMR of lung cancer was 1.23 (95% CI 1.02-1.48). The analysis based on the semi-quantitative, matrix-based exposures in the whole cohort did not suggest an increased lung cancer risk following exposure to bitumen fume. However, in an analysis restricted to road pavers, based on quantitative estimate of bitumen fume exposure, a dose-response was suggested for average level of exposure, applying a 15-year lag, which was marginally reduced after adjustment for co-exposure to coal tar. The results for cancer of the head and neck were similar to those of lung cancer, although they were based on a smaller number of deaths. There was no clear suggestion of an association with bitumen fume for any other neoplasm. CONCLUSIONS: The results of the analysis by bitumen fume exposure do not allow us to conclude on the presence or absence of a causal link between exposure to bitumen fume and risk of cancer of the lung and the head and neck.     

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.     

Mortality of butchers and cooks identified from the 1961 census of England and Wales.

OBJECTIVES--To explore a suspected hazard of lung cancer in butchers and cooks. METHODS--4018 male butchers and 2062 male cooks were identified from the 1961 census of England and Wales. 4857 (79.9%) of these men were traced through the National Health Service Central Register, and 3518 deaths were recorded during follow up to the end of 1992. Mortality from lung cancer and other causes was compared with that of the general population by the person-years method. RESULTS--Mortality from all causes was significantly below that of the national population in both butchers (standardized mortality ratio (SMR) 0.94, 95% confidence interval (95% CI) 0.90-0.98) and cooks (SMR 0.89, 95% CI 0.84-0.95). When allowance was made for a latency of 20 years from entry to follow up, the deficit in butchers was reduced, but that in cooks persisted, and was largely explained by a shortfall of deaths from cancer and circulatory disease. Mortality from lung cancer was close to expectation in the butchers (SMR 1.01, 95% CI 0.90-1.13) and below expectation in the cooks (SMR 0.93, 95% CI 0.75-1.13). Cooks had increased mortality from cancers of the oral cavity (SMR 5.57) and pharynx (SMR 2.66). CONCLUSIONS--The findings provide no support for an occupational hazard of lung cancer in either butchers or cooks. The possibility of excess risk in sub-groups of these occupations cannot be discounted. The high rates of oral and pharyngeal cancer in cooks are probably a consequence of high alcohol consumption.     

A cohort study on the mortality of firefighters.

This study was set up to investigate the effect of exposure to combustion effluents on the chronic health of firefighters. A cohort of firefighters was followed up through 10 years with regard to cause specific mortality. Comparisons were made with another cohort of civil servants and salaried employees in physically demanding jobs. After a latency of five years, an excess mortality from cancer was seen for persons aged 30 to 74 (standardised mortality ratio (SMR) 173, 95% confidence interval (95% CI) 104-270). A significant increase in lung cancer was seen in the group aged 60 to 74 (SMR 317, 95% CI 117-691), whereas non-pulmonary cancer was significantly increased in the group aged 30 to 49 (SMR 575, 95% CI 187-1341). It is concluded that inhalation of carcinogenic and toxic compounds during firefighting may constitute an occupational cancer risk. An extended use of respiratory protective equipment is advocated.     

Laryngeal cancer in Denmark: a nationwide longitudinal study based on register linkage data

To identify high and low risk groups for laryngeal cancer in Denmark, all individuals aged 30-74 in the 1970 census were followed up over 10 years. Census data were linked with the Central Population Register to identify persons who died or emigrated during the follow up, and with the Danish Cancer Register to identify cases of laryngeal cancer. Individuals were categorised according to sex, age, and sociodemographic characteristics as declared on the census forms. A multivariate analysis was carried out by means of multiplicative Poisson models. The study showed that the risk of laryngeal cancer was strongly related to sociodemographic factors. The risk for skilled workers living in Copenhagen (relative risk (RR) 4.76, 95% confidence interval (CI) 3.61-6.28) was estimated to be almost five times higher than the risk for men self employed in agriculture and living in rural areas. The variation in the risk of laryngeal cancer is not fully explained by known variations in tobacco and alcohol consumption, and this study highlights additional risk factors particularly related to occupation and marital state.     

A cohort study on the mortality of firefighters

This study was set up to investigate the effect of exposure to combustion effluents on the chronic health of firefighters. A cohort of firefighters was followed up through 10 years with regard to cause specific mortality. Comparisons were made with another cohort of civil servants and salaried employees in physically demanding jobs. After a latency of five years, an excess mortality from cancer was seen for persons aged 30 to 74 (standardised mortality ratio (SMR) 173, 95% confidence interval (95% CI) 104-270). A significant increase in lung cancer was seen in the group aged 60 to 74 (SMR 317, 95% CI 117-691), whereas non-pulmonary cancer was significantly increased in the group aged 30 to 49 (SMR 575, 95% CI 187-1341). It is concluded that inhalation of carcinogenic and toxic compounds during firefighting may constitute an occupational cancer risk. An extended use of respiratory protective equipment is advocated.     

Laryngeal cancer in Denmark: a nationwide longitudinal study based on register linkage data.

To identify high and low risk groups for laryngeal cancer in Denmark, all individuals aged 30-74 in the 1970 census were followed up over 10 years. Census data were linked with the Central Population Register to identify persons who died or emigrated during the follow up, and with the Danish Cancer Register to identify cases of laryngeal cancer. Individuals were categorised according to sex, age, and sociodemographic characteristics as declared on the census forms. A multivariate analysis was carried out by means of multiplicative Poisson models. The study showed that the risk of laryngeal cancer was strongly related to sociodemographic factors. The risk for skilled workers living in Copenhagen (relative risk (RR) 4.76, 95% confidence interval (CI) 3.61-6.28) was estimated to be almost five times higher than the risk for men self employed in agriculture and living in rural areas. The variation in the risk of laryngeal cancer is not fully explained by known variations in tobacco and alcohol consumption, and this study highlights additional risk factors particularly related to occupation and marital state.