Search

Objective: - To evaluate exposure-response relationships between 1,3-butadiene and styrene and selected diseases among synthetic rubber polymer workers., Methods: - 21,087 workers (16,579 men; 4508 women) were followed from 1943 through 2009 to determine mortality outcomes. Cox regression models estimated rate ratios (RRs) and 95% confidence intervals (CIs) by quartile of cumulative exposure to butadiene or styrene and exposure-response trends for cancers of the bladder, lung, kidney, esophagus and pancreas, and for all nonmalignant respiratory disease (NMRD), chronic obstructive pulmonary disease (COPD) and pneumonia., Results: - Bladder cancer RRs were 2.13 (95% CI = 1.03 to 4.41) and 1.64 (95% CI = 0.76 to 3.54) in the highest quartiles of cumulative exposure to butadiene and styrene, respectively, and exposure-response trends were positive for both monomers (butadiene, trend p = 0.001; styrene, trend p = 0.004). Further analyses indicated that the exposure-response effect of each monomer on bladder cancer was demonstrated clearly only in the subgroup with high cumulative exposure (at or above the median) to the other monomer. Lung cancer was not associated with either monomer among men. Among women, lung cancer RRs were above 1.0 in each quartile of cumulative exposure to each monomer, but exposure-response was not seen for either monomer. Male workers had COPD RRs slightly above 1.0 in each quartile of cumulative exposure to each monomer, but there was no evidence of exposure-response among the exposed. Monomer exposure was not consistently associated with COPD in women or with the other cancer outcomes., Conclusions: - This study found a positive exposure-response relationship between monomer exposures and bladder cancer. The independent effects of butadiene and styrene on this cancer could not be delineated. In some analyses, monomer exposure was associated with lung cancer in women and with COPD in men, but inconsistent exposure-response trends and divergent results by sex do not support a causal interpretation of the isolated positive associations., (Copyright © 2021 The Authors. Published by Elsevier B.V. All rights reserved.)

Purpose: Pooling of individual-level data for workers involved in uranium refining and processing (excluding enrichment) may provide valuable insights into risks from occupational uranium and external ionizing radiation exposures., Methods: Data were pooled for workers from four uranium processing facilities (Fernald, Mallinckrodt and Middlesex from the U.S.; and Port Hope, Canada). Employment began as early as the 1930s and follow-up was as late as 2017. Workers were exposed to high concentrations of uranium, radium, and their decay products, as well as gamma radiation and ambient radon decay products. Exposure and outcome data were harmonized using similar definitions and dose reconstruction methods. Standardized mortality ratios (SMR) were estimated., Results: In total, 560 deaths from lung cancer, 503 non-malignant respiratory diseases, 67 renal diseases, 1,596 ischemic heart diseases, and 101 dementia and Alzheimer's disease (AD) were detected in the pooled cohort of over 12,400 workers (∼1,300 females). Mean cumulative doses were 45 millisievert for whole-body external ionizing radiation exposure and 172 milligray for lung dose from radon decay products. Only SMR for dementia and AD among males was statistically significant (SMR=1.29; 95% confidence interval: 1.04, 1.54)., Conclusions: This is the largest study to date to examine long-term health risks of uranium processing workers.

The excess relative risk of mortality for all cancers excluding leukemia among nuclear workers was reanalyzed by taking the annual dose as the dose rate into consideration using publicly available epidemiological data from the Hanford site dedicated to the cohort study of nuclear workers in the United States, the United Kingdom, and Canada (Three Countries Study). Values of the dose rate (cut points) were chosen at 2 mSv y intervals from 2 to 40 mSv y, and risk estimates were made for 32,988 workers, considering doses accumulated below the cut point and above the cut point to have different effects. Although the procedure to extract the study population and the methodology used for analysis basically followed those in the Three Countries Study, additional examinations were also carried out for different risk models, lag periods, and impacts of adjusting the monitoring period to find the effect of the dose rate. As a result, no statistically significant difference in dose rate was found among the excess relative risks under different calculation conditions.

Objective: This study updates the mortality experience of over 25,000 workers in a large Canadian petroleum company through December 31, 2006., Methods: Standardized mortality ratios were generated for all-cause and specific cause mortality., Results: All cause and all cancer mortality were favorable compared with the general Canadian population. Cancers of previous interest were largely consistent with expectation. There is a continuing excess of mesothelioma, which is of similar magnitude as the previous update, although based on larger numbers. This excess is mostly attributable to men who died in their 50s and 60s and who worked in the refining sector., Conclusion: Most causes of death show mortality rates lower than the Canadian general population. Given the excess of mesothelioma observed, this study supports ongoing vigilance in asbestos exposure control programs, as refineries continue to remove asbestos from their facilities.

Background: Although interventional trials demonstrated that moderate-dose β-carotene supplementation increases lung cancer mortality in smokers and asbestos-exposed workers, differences in serum concentrations in absence of supplementation have not been studied in asbestos-exposed workers., Methods: A mortality analysis was performed to assess the relationship of nonsupplemented serum β-carotene to all-cause and cancer mortalities using 1981 to 1983 serum β-carotene concentration measurements from 2,646 U.S. white male insulators (mean age, 57.7 years). Multivariable-adjusted Cox proportional hazard models that included terms for age, duration of asbestos exposure, smoking, season, and region were fitted to estimate mortality HRs and 95% confidence intervals (CI) according to serum β-carotene concentrations., Results: Median follow-up was 12.8 years and 984 (33.8%) subjects died during the follow-up period, including 415 deaths from overall cancer and 219 deaths from lung cancer. The overall mortality HR for a serum β-carotene increase of 10 μg/dL was 0.97 (95% CI, 0.96-0.99). Compared with the lowest quartile, HRs were 0.90 (95% CI, 0.76-1.07) for the second (38-65 μg/dL), 0.80 (95% CI, 0.67-0.96) for the third (66-104 μg/dL), and 0.63 (95% CI, 0.51-0.77) for the highest serum β-carotene quartile (≥105 μg/dL). There was no association between serum β-carotene and overall cancer mortality (HR, 1.00; 95% CI, 0.97-1.02) or lung cancer mortality (HR, 0.99; 95% CI, 0.96-1.02)., Conclusions: Higher nonsupplemented serum β-carotene concentrations were negatively associated with all-cause mortality among asbestos-exposed individuals., Impact: Serum β-carotene can be a marker of one or more determinants of reduced mortality in asbestos-exposed workers. Cancer Epidemiol Biomarkers Prev; 24(3); 555-60. ©2014 AACR., (©2014 American Association for Cancer Research.)

Background: A 15-country study of nuclear workers reported significantly increased radiation-related risks of all cancers excluding leukaemia, with Canadian data a major factor behind the pooled results. We analysed mortality (1956-1994) in the updated Canadian cohort and provided revised risk estimates., Methods: Employment records were searched to verify and revise exposure data and to restore missing socioeconomic status. Excess relative risks per sievert (ERR/Sv) of recorded radiation dose and 95% confidence intervals (CIs) were estimated using Poisson regression., Results: A significant heterogeneity of the dose-response for solid cancer was identified (P=0.02), with 3088 early (1956-1964) Atomic Energy of Canada Limited (AECL) workers having a significant increase (ERR/Sv=7.87, 95% CI: 1.88, 19.5), and no evidence of radiation risk for 42,228 workers employed by three nuclear power plant companies and post-1964 AECL (ERR/Sv=-1.20, 95% CI: <-1.47, 2.39). Radiation risks of leukaemia were negative in early AECL workers and non-significantly increased in other workers. In analyses with separate terms for tritium and gamma doses, there was no evidence of increased risk from tritium exposure. All workers had mortality lower than the general population., Conclusion: Significantly increased risks for early AECL workers are most likely due to incomplete transfer of AECL dose records to the National Dose Registry. Analyses of the remainder of the Canadian nuclear workers (93.2%) provided no evidence of increased risk, but the risk estimate was compatible with estimates that form the basis of radiation protection standards. Study findings suggest that the revised Canadian cohort, with the exclusion of early AECL workers, would likely have an important effect on the 15-country pooled risk estimate of radiation-related risks of all cancer excluding leukaemia by substantially reducing the size of the point estimate and its significance.

Background: The Sheet Metal Occupational Health Institute Trust (SMOHIT) was formed in 1985 to examine the health hazards of the sheet metal industry in the U.S. and Canada through an asbestos disease screening program. A study of mortality patterns among screening program participants was undertaken., Methods: A cohort of 17,345 individuals with 20 or more years in the trade and who participated in the asbestos disease screening program were followed for vital status and causes of death between 1986 and 2004. Data from the screening program included chest X-ray results by International Labour Office (ILO) criteria and smoking history. Standardized mortality ratios (SMRs) by cause were generated using U.S. death rates and Cox proportional hazards models were used to investigate lung cancer risk relative to chest X-ray changes while controlling for smoking., Results: A significantly reduced SMR of 0.83 (95% CI = 0.80-0.85) was observed for all causes combined. Statistically significant excess mortality was observed for pleural cancers, mesothelioma, and asbestosis in the SMR analyses. Both lung cancer and COPD SMRs increased consistently and strongly with increasing ILO profusion score. In Cox models, which controlled for smoking, increased lung cancer risk was observed among workers with ILO scores of 0/1 (RR = 1.17, 95% CI = 0.89-1.54), with a strong trend for increasing lung cancer risk with increasing ILO profusion score >0/0., Conclusions: Sheet metal workers are at increased risk for asbestos-related diseases. This study contributes to the literature demonstrating asbestos-related diseases among workers with largely indirect exposures and supports an increased lung cancer risk among workers with low ILO profusion scores.

Objectives: The purpose of our study was to assess the risk of cardiovascular disease (CVD) mortality in a Canadian cohort of 337 397 individuals (169 256 men and 168 141 women) occupationally exposed to ionizing radiation and included in the National Dose Registry (NDR) of Canada., Material and Methods: Exposure to high doses of ionizing radiation, such as those received during radiotherapy, leads to increased risk of cardiovascular diseases. The emerging evidence of excess risk of CVDs after exposure to doses well below those previously considered as safe warrants epidemiological studies of populations exposed to low levels of ionizing radiation. In the present study, the cohort consisted of employees at nuclear power stations (nuclear workers) as well as medical, dental and industrial workers. The mean whole body radiation dose was 8.6 mSv for men and 1.2 mSv for women., Results: During the study period (1951-1995), as many as 3 533 deaths from cardiovascular diseases have been identified (3 018 among men and 515 among women). In the cohort, CVD mortality was significantly lower than in the general population of Canada. The cohort showed a significant dose response both among men and women. Risk estimates of CVD mortality in the NDR cohort, when expressed as excess relative risk per unit dose, were higher than those in most other occupational cohorts and higher than in the studies of Japanese atomic bomb survivors., Conclusions: The study has demonstrated a strong positive association between radiation dose and the risk of CVD mortality. Caution needs to be exercised when interpreting these results, due to the potential bias introduced by dosimetry uncertainties, the possible record linkage errors, and especially by the lack of adjustment for non-radiation risk factors.

Introduction: Despite significant reductions, the number of injuries and fatalities in mining remains high. A persistent area of concern continues to be equipment-related incidents., Method: Mine Safety and Health Administration (MSHA) and Current Population Survey (CPS) data were used to examine equipment-related injuries over the period 1995-2004. Incidents were reviewed to determine which types of mining equipment were most often involved and to identify and characterize trends., Results: Non-powered hand tools was the equipment category most often involved with non-fatal injuries while off-road ore haulage was the most common source of fatalities., Summary: Younger employees had an elevated risk of injury while workers >55 years had an elevated risk for fatality. A large majority of incidents involve workers with <5 years experience., Impact on Industry: Results should increase hazard awareness and enable mine management to select and prioritize problem areas and safety system weaknesses in both underground and surface mining.

Background: Previously, the mortality was reported in a cohort of male workers at an Ontario chemical plant., Aims: To expand the cohort and to investigate the mortality and cancer incidence risk among chemical manufacturing sites., Methods: We followed 5277 men and 1301 women from 1950 to 1999., Results: Employees experienced lower mortality and cancer incidence rates than the general population for several major causes of death, including heart disease, respiratory cancer and many other cancers. There were no cases of angiosarcoma of the liver. We observed a lower mortality rate of prostate cancer [standardized mortality ratio = 0.79, 95% confidence interval (CI) 0.43-1.32], but a higher incidence rate of prostate cancer [standardized incidence ratio (SIR) = 1.22, 95% CI 1.00-1.48]. Among the Sarnia employees, the incidence of pleural neoplasms was increased (5 observed versus 1.48 expected, SIR = 3.37, 95% CI 1.09-7.86). These cancers were included in the 12 deaths with malignant mesothelioma at Sarnia., Conclusion: Consistent with the earlier report, lower mortality rates were observed for the major classifications of disease and malignant neoplasms. The higher incidence rates of prostate cancer are not readily explainable but may reflect increased screening among current employees and recent retirees. Past asbestos exposure prior to 1980 is probably a contributor to the deaths due to malignant mesothelioma but is not reflected in lung cancer mortality. We find little indication of any other increased rates of mortality or cancer within the overall workforce of these chemical plants.

Occupational exposure is an important potential confounder in air pollution studies because it is plausible that individuals who live in highly polluted areas also work in more polluted environments. While the original investigators made some efforts to control for possible confounding by occupational variables, it was felt that these could be improved upon. The reanalysis team attempted to control for occupational confounding by supplementing the original data sets with two new variables, an indicator of the "dirtiness" of a subject's job and an indicator of possible exposure to occupational lung carcinogens. The attribution of these variables was based on the job title recorded by the original investigators and on the judgment of our experts concerning typical exposure patterns in different occupations. We fitted Cox proportional-hazards models identical to those that had been used by the original investigators while also including one or both of the new occupational covariates in the models. In none of the analyses did the inclusion of the occupational variables materially change the results. It would therefore appear that, in general, the results reported by the original investigators were not distorted by inadequate control of occupational variables. We also carried out some analyses using the dirtiness index as a stratification variable to assess effect modification. There was some indication, albeit inconsistent, that the effect of air pollution on mortality was greater among subjects with dirty jobs than among those with clean jobs.

Recent epidemiologic studies have consistently reported increased daily mortalities and hospital admissions associated with exposure to particulate air pollution. Ischemic heart disease (IHD*, International Classification of Diseases, Eighth Revision [ICD-8], codes 410-414) is among those diseases that contribute in large measure to this excess mortality. Some occupational studies have suggested elevated risk of IHD among workers exposed for short periods to styrene, which can be emitted from fossil fuel combustion, aircraft exhausts, and motor vehicle exhausts. Styrene is found in ambient air at average concentrations of a few micrograms per cubic meter or less but may reach very high concentrations at particular locations and times. Unmeasured aerosols of styrene may also increase population exposures. This case-cohort study explored a possible association and dose-response relation between styrene exposure and risk of acute IHD in an occupational setting. The population under study was 6587 male workers employed between 1943 and 1982 in two US plants manufacturing styrene-butadiene polymers used in synthetic rubber. The study assessed all 498 subjects who died from IHD along with a subcohort of twice that size, 997 subjects, selected as a 15% random sample of the full target cohort. IHD deaths during the study led to some overlap between cases and the subcohort, leaving 1424 unique subjects. Job histories were collected for all subjects. Industrial hygienists and engineers from the industry estimated relative exposures for all jobs. Exposure data were collected for many of the jobs from different sources. For any job with no available exposure measurements, z scores were used to estimate job exposure in each plant from the relative exposure level for that job in similar plants and the measurement distribution parameters of the study plant. Standardized mortality ratio (SMR) analyses were used to examine the overall risk of dying from IHD among study subjects compared with the US general population. A significantly elevated SMR of 1.47 with a 95% confidence interval (95% CI) of 1.17 to 1.77 for chronic IHD was found among black workers who had left the plants. A modification of the Cox proportional hazard regression model was used to control for confounders and examine dose-response relations between styrene exposure and the risk of IHD. Employment time-weighted average (TWA) styrene concentration intensity for the most recent 2 years was found significantly associated with death from acute IHD among active workers with a relative hazard of 3.26 to 6.60, depending on duration of employment. In this analysis, the highest relative hazard of 6.60 (95% CI, 1.78-24.54) was among active workers who had been employed for at least 5 years. The results suggest that the exposure intensity was more important than duration of exposure. On the basis of the dose-response relation established in this study, we estimate that for each 10 microg/m3 increase in ambient styrene, acute IHD mortality might increase 0.4%. At normal ambient styrene levels, the relative risk would be increased, at most, 0.1% compared with no exposure. At certain locations and times, however, ambient styrene could reach levels that would result in a relative hazard for acute IHD mortality as high as 3.386-fold the risk at no exposure.

Objectives: To update mortality for 34 560 employees from diverse operating segments of a Canadian petroleum company; and to investigate potential relations with occupational factors., Methods: Employees from 1964-83 were linked to the Canadian mortality data base to provide 11 years additional follow up. There were 6760 deaths and 750 683 person-years of follow up compared with 3909 and 428 190, respectively, in the earlier study. Analyses used standardised mortality ratios (SMRs) to compare worker cause specific mortality with the Canadian general population. Duration of employment and latency analyses were performed for causes previously found to be increased in this and other petroleum cohorts, as well as any findings of interest., Results: For the period 1964-94, employees experienced significantly low overall mortality (SMR=0.86 men, SMR=0.80 women). Kidney cancer, which has been increased in some studies of petroleum workers, was not increased. Acute non-lymphocytic leukaemia in exposed operating segments was consistent with the expected or only slightly, non-significantly increased. The most notable finding was increased deaths from mesothelioma among refinery and petrochemical workers (SMR 8.68; 95% confidence interval (95% CI) 5.51 to 13.03), most of whom were long term employees in jobs with presumed exposure to asbestos (mechanical and pipefitters). Deaths from multiple myeloma among marketing and distribution workers, which were previously increased, remained increased (SMR 2.08; 95% CI 0.95 to 3.95) in the update period 1984-94; however, there was no clear pattern by duration of employment or latency. Aortic aneurysms, which also were previously significantly increased among marketing and distribution workers approached the expected in the update period (SMR 1.18; 95% CI 0. 65-1.98). Analyses by duration of employment showed suggestive trends for aortic aneurysms, but earlier studies of this cohort have not found a relation between aortic aneurysms and exposure to hydrocarbons., Conclusion: The additional 2851 deaths and 322 493 person-years of follow up strengthened the assessment of mortality patterns relative to occupational factors. With the exception of mesothelioma, no clear work related increases in disease were identified.

Most analytic studies of human epidemiologic data have affirmed the linear association between excess lung cancer risk and airborne arsenic exposure. Recent Canadian analyses, however, based on the mortality follow-up of Tacoma smelter workers from 1940-1976, provided strong evidence of a nonlinear dose-response when lung cancer risk was expressed in terms of the standardized mortality ratio. Using recently updated data covering ten additional years of mortality experience among Tacoma workers (1940-1986), new analyses were undertaken to further explore nonlinearity in the lung cancer dose-response in this worker cohort. Lung cancer risk was expressed in terms of both the standardized mortality ratio (SMR) and the excess mortality rate (EMR). As in Canadian analyses, nonlinearity was assessed through a three parameter model containing both linear and negative exponential terms for dose. Dropping the negative-exponential dose-term lead to the standard suite of linear dose-response models, with and without intercept, used for comparative purposes. Analyses were undertaken by subcohort as there was strong evidence of confounding by year of initial hire, which largely explained the nonlinearity in the dose-response observed in Canadian analyses. Subcohort analyses based on initial employment, prior to 1940 or thereafter, showed that the nonlinearity in the dose-response was strongly influenced by date of initial hire. whether the cohort risk was measured by either the SMR or EMR, a nonlinear dose-response was evident only among workers hired prior to 1940. This, however, was strongly related to the artifactually low lung cancer mortality seen among workers hired between 1930 and 1939. Among workers hired after 1940, analyses showed that a linear dose-response provided a clearly superior fit. While analyses showed comparable goodness of fit when models were fitted to the SMR and EMR. Only those based on the EMR provided strong evidence of a dose-response. Overall, nonlinearity as observed in Canadian analyses was likely the result of several sources of bias not taken into account by Canadian investigators., (Copyright 1999 Academic Press.)

Objective: To detect unsuspected associations between workplace situations and specific causes of death in Canada., Methods: An occupational surveillance system was established consisting of a cohort of 457,224 men and 242,196 women employed between 1965 and 1971, constituting about 10% of the labour force in Canada at that time. Mortality between 1965 and 1991 has been determined by computerised record linkage with the Canadian mortality database. Through regression analysis, associations between 670 occupations and 70 specific causes of death were measured., Results: There were almost 116,000 deaths among men and over 26,800 deaths among women. About 28,000 comparisons were made between occupations and specific causes of death. With various reporting criteria, several potential associations were highlighted, including: infectious disease mortality among barbers and hairdressers; laryngeal cancer among male metal fitters and assemblers; lung cancer among female waiters; breast cancer among female metal fitters and assemblers; brain cancer among female nursing assistants and male painters; and ischaemic heart disease among female inspectors and foremen and among male taxi drivers and chauffeurs., Conclusions: When excess risk of mortality is apparent, the intention of this occupational surveillance system is to spark further studies to gain aetiological knowledge.

Despite the special working environment and exposures of airline pilots, data on risk of death and cancer incidence in this occupational group are limited. The authors investigated a cohort of 2,740 Air Canada pilots who contributed 62,449 person-years of observation. All male pilots employed for at least 1 year on and since January 1, 1950, were studied. The cutoff date for outcome information was December 31, 1992. Standardized mortality ratio (SMR) and standardized incidence ratio (SIR) were used to compare mortality rates and cancer incidence rates of the cohort with the respective Canadian population rates. Ninety percent confidence intervals of the SMR and SIR were calculated. Statistically significant decreased mortality was observed for all causes (SMR = 0.63, 90% confidence interval (CI) 0.56-0.70), for all cancers (SMR = 0.61, 90% CI 0.48-0.76), and for all noncancer diseases (SMR = 0.53, 90% CI 0.45-0.62). Mortality from aircraft accidents was significantly raised (SMR = 26.57, 90% CI 19.3-35.9). Significantly decreased cancer incidence was observed for all cancers (SIR = 0.71, 90% CI 0.61-0.82), rectal cancer (SIR = 0.42, 90% CI 0.14-0.96), lung cancer (SIR = 0.28, 90% CI 0.16-0.46), and bladder cancer (SIR = 0.36, 90% CI 0.12-0.82). Prostate cancer (SIR = 1.87, 90% CI 1.38-2.49) and acute myeloid leukemia (SIR = 4.72, 90% CI 2.05-9.31) were significantly increased. The preferred relative risk model for radiation-induced nonchronic lymphoid leukemia (Beir V report) was applied to the cohort by using published estimates of in-flight radiation exposures. The estimated relative risk ranged from 1.001 to 1.06 and did not differ significantly from the observed SIR (SIR = 1.88, 90% CI 0.80-3.53). However, the incidence rate of acute myeloid leukemia was significantly increased. Monitoring of in-flight radiation exposure and long-term follow-up of civil aviation crew members is needed to further assess cancer incidence and leukemia risk in this special occupational group.

This study examined mortality to December 31, 1989 in a cohort of 2,222 males employed between 1947 and 1975 at a transformer manufacturing plant in Canada, where there had been extensive use of transformer fluid, some containing polychlorinated biphenyls (PCBs). A combined cohort list of 2,222 names was independently obtained from plant management and union officials. Mortality of 1,939 workers with known birthdates was ascertained by record linkage with the Canadian Mortality Data-base. Standardized mortality ratios (SMRs) for different criteria for acceptance of the death certificate link and for cohort membership (based on work history) ranged from .71-1.05. There was no significant increase in overall cancer deaths. The only significant site-specific increased mortality was pancreatic cancer (11 deaths), with SMRs ranging from 2.92-7.64 and higher mortality risk in those who entered the cohort prior to 1960. All but one of these deaths had a latency period of at least 10 years, and greatest SMRs were found in departments with the greatest exposure to transformer fluid. Several previous studies have found excess pancreatic cancers in association with oil exposures and electrical equipment manufacturing. The need to further investigate pancreatic cancer in transformer manufacturing and related exposures is evident.

Objective: To estimate the extent of occupational disease morbidity and mortality in Canada by comparing and contrasting four different data sources., Data Sources: 1) Canadian National Workers' Compensation Boards Statistics, 2) U.S. Bureau of Labor Statistics adjusted to Canadian Workforce, 3) California Physician's First Reports adjusted to the Canadian Workforce, and 4) proportionate model of overall disease incidence obtained through literature review., Main Findings: Each data source was limited in its ability to provide a true estimate of the extent of morbidity and mortality due to occupational disease in Canada. Collectively, an estimate of between 77,900 and 112,000 new cases of occupational diseases and 2,381 to 6,010 occupational disease deaths were obtained., Conclusions: Occupational diseases are a significant and under-estimated cause of morbidity and mortality in Canada.

We conducted a retrospective mortality study among 6672 petroleum marketing and distribution workers from 226 locations throughout Canada. These employees worked for at least 1 year in the marketing distribution segment from 1964 through 1983 or were annuitants as of 1964. Industrial hygienists assigned hydrocarbon (HC) exposure frequency scores for several jobs, departments, and job functions. We computed standardized mortality ratios for the total cohort, HC exposure frequency groups, and tank truck drivers, and we also used Poisson regression techniques to model mortality for selected causes of death according to HC exposure frequency. Results indicate overall mortality below that of the general Canadian population for all marketing distribution workers [Standardized mortality ratio (SMR) = 0.88]. Mortality from aortic aneurysms was significantly elevated in all marketing/distribution workers (SMR = 1.79) but was due to raised mortality in nonexposed workers (SMR = 2.80). Tank truck drivers showed significantly elevated mortality due to leukemia (SMR = 3.35) based on five deaths. The leukemia findings were not evident in the larger group of marketing distribution workers classified as exposed to hydrocarbons (SMR = 1.01). No other cause of death was elevated in truck drivers. The leukemia findings are suggestive of a possible influence due to exposure to HCs in tank truck drivers, although other explanations cannot be ruled out. Other findings of elevated mortality in the marketing distribution group are generally not statistically significant. These included moderately increased mortality due to multiple myeloma, malignant melanoma, and kidney cancer. Small numbers of observed and expected deaths limit concise interpretations for these diseases.

An incidence study of malignant melanoma of the skin (MMS), conducted previously among the workers of four plants of a large telecommunications industry located in Montreal, Canada, showed a standardised incidence ratio of 2.7 (95% confidence interval (95% CI) 1.3-5.02) for the years 1976 to 1983. To describe more precisely the magnitude of the problem a mortality study was started among the same population (n = 9590) for the same period (1976-83). At the end of 1983, 9180 workers were alive, 261 were dead, and 149 (1.5%) were not traced. Standardised mortality ratios (SMRs) for all causes of death were surprisingly low for men (SMR = 0.57; 95% CI 0.50-0.64) and women (SMR = 0.56; 95% CI 0.37-0.82). The SMRs for major causes of death were also less than expected. These results may be explained by a pronounced selection bias (healthy worker effect) and by the short duration of follow up (eight years). For MMS, two deaths occurred among men (SMR = 2.00; 95% CI 0.24-7.22) and one among women (SMR = 4.81; 95% CI 0.12-26.78). A third man who died of MMS was miscoded as having a primary pulmonary melanoma. Including this case increased the SMR for MMS to 3.00 (95% CI 0.62-8.77; p = 0.08). Polyvinyl chloride and polychlorinated biphenyls were used in the plants and some of the workers did soldering. A planned case-control study will investigate other possible exposures at work.

This retrospective mortality study was conducted among 34,597 oil industry workers in diverse operating segments. Employees were traced through Statistics Canada, and overall mortality (SMR = 0.85) was lower than general population rates and similar to other petrochemical cohorts. The most notable finding was a significant excess of malignant melanoma [observed deaths (N) = 16, SMR = 1.87, 95% CI = 1.07, 3.04], which concentrated among upstream workers (N = 6, SMR = 6.00, 95% CI = 2.19, 13.06), and was directly related to employment duration and latency. Specific substances or hydrocarbon (HC) streams could not be implicated, although possible explanations include dermal HC exposure, ultraviolet light exposure, or a synergistic effect between these two factors. Marketing/transportation workers showed a non-significant excess of multiple myeloma (SMR = 1.81), which was also related to employment duration, latency, and commencement of employment before 1950. Lymphatic cancer, skin cancer, and kidney cancer mortality was not elevated in refinery workers, a finding at odds with some previous refinery worker studies. Although the malignant melanoma and possibly the multiple myeloma mortality patterns are consistent with an occupational link, further studies are needed to investigate the relationship of these diseases with particular exposures.

This paper reviews the epidemiologic evidence of cancer risks among workers in aluminum reduction plants with emphasis on associations with specific work areas and exposures. Studies of workers manufacturing carbon products outside the aluminum industry were also reviewed since the work environment is similar to that encountered in the carbon area of aluminum plants. We obtained 22 reports from references cited in earlier reviews, through compact disc literature search 1980-1990, and from the Nordic Aluminum Industry's Secretariat for Health, Environment and Safety. Six reports were excluded because the material was included in later studies or because a critical evaluation was impossible. This left 16 publications from 11 separate studies. Work in potrooms with Söderberg electrolytic cells was associated with increased risk of bladder cancer, and the increase was correlated to duration of tar exposure. There was a suggestion of increased risk of leukemias and pancreatic cancers in potroom workers, and of kidney and brain cancers without any clear association with specific exposures or work areas. Singular results showed associations between lung cancer risk and tar exposure in Söderberg plants, and between lung cancer and work in prebake or carbon plants, but interpretation was limited by inadequate data on smoking and asbestos exposure, and by problems connected with the choice of reference populations in these studies.

There is extensive information on discordance in general between accuracy of medical diagnoses on death certificate categorization of cause of death and available clinical and histopathological data. This is as true for occupational disease as for other conditions. But occupational illnesses bear a special problem. Discordance is not equal across the board--it may vary with each occupationally related disease, and no single formula can be applied. It may be high for angiosarcoma and low for acute hydrogen sulfide poisoning, low for bladder cancer, high for unsuspected methyl mercury poisoning. We have found that for one agent--asbestos--there were different rates of discordance for different asbestos-related diseases (e.g., lung cancer, mesothelioma, asbestosis, kidney cancer) among 4,951 deaths studied prospectively from 1967 to 1986. Caution is therefore required before accepting generalizations concerning (unstudied) discordance in occupational mortality studies, and in their use in risk assessment models.

We compared death certificates for asbestos-associated diseases (mesothelioma, lung cancer, asbestosis) in two asbestos workers' cohorts. One (insulation workers) had current or recent employment and a strong, continuing union support system which gave them much information about the effects of asbestos exposure. The second cohort, asbestos factory workers, had no such advantage. The factory had closed almost 30 years before, and its workers had dispersed into many areas of the state and nation. Accuracy of medical diagnosis was comparable in the two groups, but occupational listings were not. Three-quarters of the insulators' death certificates told of asbestos work, while virtually none of the factory workers' certificates provided such information, even for deaths of mesothelioma and asbestosis. The data indicate that disease categories, based on medical and pathological diagnoses, at least for asbestos-associated disease, tend to be accurate. Attempts to identify groups at risk by sorting occupational categories can give variable results, good for those with current exposures, much less satisfactory for those with long-past occupational exposures.

A cohort of 54,128 men who worked in Ontario mines was observed for mortality between 1955 and 1986. Most of these men worked in nickel, gold, or uranium mines; a few worked in silver, iron, lead/zinc, or other ore mines. If mortality that occurred after a man had started to mine uranium was excluded, an excess of carcinoma of the lung was found among the 13,603 Ontario gold miners in the study (standardised mortality ratio (SMR) 129, 95% confidence interval (95% CI) 115-145) and in men who began to mine nickel before 1936 (SMR 141, 95% CI 105-184). The excess mortality from lung cancer in the gold miners was confined to men who began gold mining before 1946. No increase in the mortality from carcinoma of the lung was evident in men who began mining gold after the end of 1945, in men who began mining nickel after 1936, or in men who mined ores other than gold, nickel, and uranium. In the gold mines each year of employment before the end of 1945 was associated with a 6.5% increase in mortality from lung cancer 20 or more years after the miner began working the mines (95% CI 1.6-11.4%); each year of employment before the end of 1945 in mines in which the host rock contained 0.1% arsenic was associated with a 3.1% increase in lung cancer 20 years or more after exposure began (95% CI 1.1-5.1%); and each working level month of exposure to radon decay products was associated with a 1.2% increase in mortality from lung cancer five or more years after exposure began (95% CI 0.02-2.4%). A comparison of two models shows that the excess of lung cancer mortality in Ontario gold miners is associated with exposure to high dust concentrations before 1946, with exposure to arsenic before 1946, and with exposure to radon decay products. No association between the increased incidence of carcinoma of the lung in Ontario gold miners and exposure to mineral fibre could be detected. It is concluded that the excess of carcinoma of the lung in Ontario gold miners is probably due to exposure to arsenic and radon decay products.

Data have been gathered from Labour Canada and the Quebec Workers' Compensation Board to examine estimates of mortality in 482 Canadian occupations. These data contain information on job-related fatalities within four-digit occupations for 1980, 1981, 1985, and 1986. Compared with comparable data from the United States, the estimates indicate that the incidence of job-related fatalities is significantly higher in Canada.

Age specific standardised mortality ratios (ASMRs) were compared for commercial fishermen under 55 years old and those who were aged 55 and older in the Canadian Atlantic coastal provinces of Nova Scotia, New Brunswick, and Prince Edward Island. The subjects were a cohort of 31,415 fishermen licensed by the Department of Fisheries and Oceans during 1975-83. Mortality was obtained by a computerised linking of the registry of licensed commercial fisheries and the Canadian Mortality Data Base. Fishermen under 55 had ASMRs between 1.4 and 1.7 for death from all causes and around 1.0 for death from non-accidental causes. The older fishermen had ASMRs as low as 0.6 for all causes and non-accidental causes. The same pattern was shown for death from specific causes such as ischaemic heart disease, accidents, and cancer, as well as for different years of entry into the cohort. This pattern differed widely from that of most other occupations. Dividing the cohort into owners and crew members showed that the high mortality ratios at younger ages existed in crew members only. It was concluded that the high death rates for fishermen under 55 had a socioeconomic component.

A historical prospective mortality study was conducted at a glass filament plant in Ontario, Canada. The cohort consisted of 1465 men and women who had worked for a total of at least one year between 1951 (when the operations began) and 1986. Ninety six deaths were found in the 96% of persons traced. Mortality was compared by the person-years method with that of the Ontario population. An estimate of cumulative dust exposure was made based on long term employees' recollections of past conditions. Overall mortality was below that expected (standardised mortality ratio (SMR) = 76) based on 82 deaths. There were 11 deaths due to lung cancer; slightly but not significantly more than expected (SMR = 136, p = 0.31). Analysis by both duration of employment and cumulative exposure showed this increase to be inconsistent with an occupational aetiology.

A cohort of 12,110 male workers employed 1 or more years in eight styrene-butadiene polymer (SBR) manufacturing plants in the United States and Canada has been followed for mortality over a 40-year period, 1943 to 1982. The all-cause mortality of these workers was low [standardized mortality ratio (SMR) = 0.81] compared to that of the general population. However, some specific sites of cancers had SMRs that exceeded 1.00. These sites were then examined by major work divisions. The sites of interest included leukemia and non-Hodgkin's lymphoma in whites. The SMRs for cancers of the digestive tract were higher than expected, especially esophageal cancer in whites and stomach cancer in blacks. The SMR for arteriosclerotic heart disease in black workers was significantly higher than would be expected based on general population rates. Employees were assigned to a work area based on job longest held. The SMRs for specific diseases differed by work area. Production workers showed increased SMRs for hematologic neoplasms and maintenance workers, for digestive cancers. A significant excess SMR for arteriosclerotic heart disease occurred only in black maintenance workers, although excess mortality from this disease occurred in blacks regardless of where they worked the longest. A significant excess SMR for rheumatic heart disease was associated with work in the combined, all-other work areas. For many causes of death, there were significant deficits in the SMRs.

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.

The cancer mortality experience from 1964 to 1973 of employees of the Imperial Oil Limited was examined in a cohort study. Employees in jobs which exposed them on a daily basis to crude petroleum or its products, compared with nonexposed employees, were found to have more than three times the risk of esophageal and stomach cancer and about twice the risk of lung cancer. In the exposed group, increasing risks of both cancers occurred with increasing duration of employment. In the absence of more complete information on the similarity of the exposed and nonexposed employees, these results cannot be ascribed with certainty to a carcinogenic effect of petroleum. However, there was no other clear explanation for the results, and further study is required. When refinery workers were compared with nonrefinery workers without consideration of exposure to petroleum in either group, the refinery workers were found to have twice the risk of cancer of the intestines (including rectum) and other digestive organs. No relationship with duration of employment was evident. Although the increased intestinal cancer mortality in the refinery workers was not consistent, bias was not an obvious explanation for the observed relationship. Therefore, the presence on a refinery site of a carcinogen other than petroleum has not been ruled out, and further study is urged.

Mortality among 2,113 U.S. and Canadian members of the Pulp, Sulfite, and Paper Workers' Union, 1935 through 1964, was studied using a proportionate mortality analysis. Mortality due to gastric cancer was found to be elevated in all jurisdictions, but only in mills using sulfate or sulfite pulping. An excess of mortality due to kidney cancer was limited to mills in Oregon and Washington. Excesses of deaths due to leukemia, Hodgkin's disease, and lymphosarcoma were observed only in mills in Oregon, Washington, and Wisconsin and the province of Quebec. Based on small numbers, excesses of deaths due to cancers of rectum, pancreas, kidney, and lymphosarcoma were seen primarily among sulfite process workers, while Hodgkin's disease deaths occurred primarily in sulfate (kraft) process workers. These findings suggest that cancer mortality in pulp and paper workers may be related both to pulping process and to tree species processed.