It has been a matter of controversy whether there is an increased risk of lung cancer among asbestos-exposed workers without radiographic asbestosis. A previous study of lung cancer risk among asbestos-cement workers has been updated with an additional 12 years of follow-up.
Subjects had received radiographic examination at 20 and 25 years from first exposure to asbestos. Radiographs were interpreted by a single National Institute of Safety and Health (NIOSH)-certified B-reader using the 1971 International Labor Office (ILO) Classification of the pneumoconioses as reference standard. Asbestosis was defined as an ILO coding of 1/0 or higher. Standardized Mortality Ratios (SMRs) were calculated using the general population of Ontario as reference.
Among asbestos-cement workers without radiographic asbestosis at 20 years latency the lung cancer SMR was 3.84 (2.24-6.14). Among workers without asbestosis when examined at 25 years latency the SMR was 3.69 (1.59-7.26).
Workers from an Ontario asbestos-cement factory who did not have radiographic asbestosis at 20 or 25 years from first exposure to asbestos continued to have an increased risk of death from lung cancer during an additional 12 years of follow-up.
Comment In: Am J Ind Med. 2011 Jun;54(6):495-6; author reply 497-821328422
In the 1980s and 1990s, the Government of Canada closed and/or issued advisories for a number of shellfish fisheries in coastal areas of British Columbia because of dioxin contamination. Only the direct health risks (i.e., cancer) of consuming contaminated shellfish for the general population were considered by the Government in the formulation of risk management options. A focus on the direct risks does not provide an adequate basis for risk decisions as the countervailing risks which may be created from management measures may easily be overlooked. This study describes the potential health impacts of risk management options for aboriginal coastal peoples in the management of dioxin contamination. Gold River and Powell River in British Columbia, Canada, are the areas of focus. The cancer risks of consuming dioxin contaminated shellfish for these sites are estimated. To assess the countervailing risks of management decisions for comparison, a scenario was developed in which First Nations peoples substitute shellfish with store-bought foods in their diets in the event of a fishery closure or advisory. Increases in mortality due to coronary heart disease are estimated. The results suggest that the health risks of dietary changes among aboriginal peoples may be as significant as those related to eating dioxin contaminated shellfish.
A cohort study of the mortality experience (1971-1987) of male Canadian prairie farmers has been conducted. This involved linking the records of 156,242 male Alberta, Saskatchewan and Manitoba farmers identified on the 1971 Census of Agriculture and the corresponding Census of Population to mortality records. Exposure indices for individual farm operators were derived from 1971 Census of Agriculture records. Cancer histologies for brain cancer cases were obtained from the Canadian National Cancer Incidence Database and from Provincial Cancer Registries. A statistically significant association was noted between risk of dying of glioblastomas and increasing fuel/oil expenditures (test for trend p = 0.03, top quartile relative risk = 2.11, 95% confidence interval = 0.89-5.01). No significant association was found between brain cancer and either education or mother tongue. However, low income was associated with a significantly reduced risk of brain cancer mortality.
The objective of this study is to assess the carcinogenicity of pentachlorophenol and tetrachlorophenol using data from the BC sawmill workers cohort study.
The cohort consisted of 27,464 men employed by 14 sawmills for 1 year or more between 1950 and 1995. Fatal (1950-1995) and incident (1969-1995) cancers were identified using national registries. Plant records and systematic interviews with senior employees were used to estimate dermal exposure. Comparisons were made with the general BC population and dose-response relationships were assessed using Poisson regression.
There were 1,495 fatal cancer and 2,571 incident cancers. There were no large or statistically significant excesses of any of the specific cancers were observed compared to the general population. Internal analyses showed strong dose-response relationships for non-Hodgkin's lymphoma, multiple myeloma, and kidney cancer. These relationships were strongest when exposure was restricted to pentachlorophenol. The strength of the dose-response increased when exposure was lagged by 20 years.
Dermal exposure to pentachlorophenol was associated with non-Hodgkin's lymphoma, multiple myeloma, and kidney cancer, but not with other cancers of a priori interest.
The aim of this study was to investigate the incidence of cancer among 318 male employees of a niobium mining company which was only operated between 1951 and 1965. Many of the workers, especially underground miners, were exposed to the daughters of radon and thoron and also to thorium. The accumulated doses to the workers from short-lived radon and thoron daughters in the mine atmosphere were assessed to be relatively low; up to 300 working-level months. During the follow-up period 1953-1981, 24 new cases of cancer were observed compared to an expected number of 22.8. Twelve cases of lung cancer had occurred versus 3.0 expected. Among the 77 miners, 9 cases of lung cancer were observed against 0.8 expected. Associations between the occurrence of lung cancer and exposure to alpha radiation and smoking were found. For the radon and thoron daughter exposure, about 50 excess cases per million person-years at risk per working-level month were observed.
AIMS: To assess whether cancer incidence and mortality in chronic obstructive lung diseases were increased in the Swedish polyurethane foam industry cohort, updated with 11 more years of follow up. METHODS: The mortality and cancer incidence (1959-98) experienced by a cohort of 4175 male and female employees employed for at least one year in the period 1959-87 at one of nine Swedish polyurethane foaming plants were investigated. Comparisons were based on calendar year, sex, and five-year age group specific mortality and incidence rates for Sweden. Workplaces and job tasks were categorically assessed for exposure to toluene diisocyanate (TDI) and methylene diphenyldiisocyanate (MDI) by occupational hygienists. RESULTS: Fewer cancer cases than expected were observed, but the lung cancer incidence was enhanced in women. Women with "apparent exposure" to TDI or MDI did not, however, have a higher lung cancer incidence than those with "no or low exposure". Moreover, a nested case referent study did not find that polyurethane dust exposure had been more prevalent among the female lung cancer cases than among referents. No increased mortality in chronic obstructive lung diseases was observed in the cohort. CONCLUSIONS: Results support the findings from two other cohort studies of an increased lung cancer risk among female workers in the polyurethane foam manufacturing industry. Chance or confounding from smoking are not obvious explanations for the coherent findings. However, the study was not able to link isocyanate exposed employment with lung cancer risk.
OBJECTIVE--The aim of this study was to study the incidence of cancer and deaths from cancer and other diseases among patients referred to the 11 clinics of occupational medicine in Sweden between 1967 and 1987 for examination because of exposure to organic solvents. METHODS--The cohort comprised 5791 persons, 5283 men and 508 women. Information about cancer incidence and causes of death was collected from the Cancer Register of the National Board of Health and Welfare and the National Death Register of Statistics Sweden, respectively. The expected values were calculated from the national death rates and incidence rates of cancer. RESULTS--The overall mortality rate was close to expected, but the mortality rate was decreased for diseases of the circulatory system [standardized mortality ratio (SMR) 0.7, 95% confidence limit (95% CI) 0.5-0.9] and increased for suicide (SMR 2.0, 95% CI 1.2-3.2). The total cancer incidence was slightly elevated [standardized incidence ratio (SIR) 1.2, 95% CI 0.99-1.4], and some specific cancer sites showed an increased incidence, although the lower confidence limits surpassed one. Malignancies of the lymphohematopoietic system and cancer of the uterine cervix had an increased risk (SIR 1.9, 95% CI 1.2-3.2, and SIR 3.7, 95% CI 2.2-6.2, respectively). Patients with presumerably high solvent exposure had an SIR of 1.4 for all malignancies (95% CI 0.9-2.1) and those with presumerably low exposure had an SIR of 1.1 (95% CI 0.9-1.4). CONCLUSIONS--The study showed an increased risk for malignancies of the hematopoietic system and the uterine cervix among patients originally examined with regard to solvent-induced disorders. There was also an increased risk of suicide and a decreased risk of death from diseases of the circulatory system. There was no increased risk for deaths from mental or neurological disorders.
A cohort study of 43,826 male pensioners of the Canadian National Railway Company was conducted. The cause of death of 17,838 pensioners who died between 1965 and 1977 was ascertained by computerized record linkage to the Canadian national mortality data base. The main finding was an elevated risk of lung cancer for those employed in occupations involving exposure to diesel fumes and coal dust, with highly significant dose-response relationships observed. That such association may be due in part to smoking cannot be excluded; but in view of the widespread exposure to diesel fumes, the finding warrants further investigation. The present study also demonstrated the utility and feasibility of large-scale occupational cohort studies conducted with the use of computerized record linkage to national mortality records.