Cohort mortality results

Spirtas R, Stewart PA, Lee JS, et al. 1991. Retrospective cohort mortality study of workers at an aircraft maintenance Facility 1. Epidemiological results. Br J Ind Med 515-530. 

Mortality studies for workers exposed occupationally to lead are available. These studies all report discrepant results, and all are limited with respect to study design. Therefore, no firm conclusions regarding cause and effect can be drawn from these studies relative to a minimum lethal dose. A cohort mortality study of employees at lead-producing facilities was conducted (Cooper 1988 Cooper et al. 

In humans, cases of hepatomas have appeared years after acute exposure to carbon tetrachloride, however, none of the cases could establish a causal link between the exposure and development of neoplasms." Epidemiological studies have also given inconclusive results. A cancer mortality study of a population of rubber workers reported a significantly elevated odds ratio relating carbon tetrachloride with lymphatic leukemia, and lymphosarcoma and reticulum cell carcinoma." A recent retrospective cohort mortality study of aircraft maintenance workers found an increased risk of... 

A cohort study of 5668 NG-exposed workers found an increased standardized mortality ratio for deaths from ischemic heart disease. The increase was more pronounced for those with 10 or more years of exposure and was statistically significant for the 40- to 49-year age group, whereas a deficit of cardiovascular mortality had been anticipated because of preplacement and annual medical examinations designed to exclude persons with cardiovascular abnormalities. These results were confirmed in a retrospective cohort mortality study that found a significant excess of ischemic heart disease mortality among workers actively exposed to NG and under the age of 45. ° (Note this study failed to detect a chronic cardiovascular effect as excess risk was only associated with workers actively exposed to NG.)... 

Brown (1992) conducted a cohort mortality study of workers employed at four pesticide manufacturing plants. The 1158 workers employed at Plant 3 of the study, which produced aldrin and dieldrin, were also potentially exposed to l,2-dibromo-3-chloropropane produced at the plant between 1975 and 1976. The cohort included all white males employed for six or more months before 1964 with follow-up through 1987. Although overall cancer mortality at Plant 3 was not elevated (SMR, 0.9 95% Cl, 0.7-1.1 = 72), an excess of liver and biliary tract cancer was observed (SMR, 3.9 95% Cl, 1.3-9.2 5 observed). All of the deaths occurred at least 15 years after first employment (SMR, 4.9), but no association was observed with duration of employment. The SMR for lung cancer was 0.7 (95% Cl, 0.4-1.0). Levels of exposure were not reported. Amoateng-Adjepong et al. (1995) reported the results of an update of the same cohort with three additional years of follow-up. No new association was reported. 

Olsen et al. (1994) reported on the results of a retrospective cohort mortality study... 

Several epidemiological studies on the effects of PPOA in humans have been conducted on workers. These studies did not examine developmental outcomes. A retrospective cohort mortality study demonstrated a statistically significant association between prostate cancer mortality and employment duration in the chemical facility of a plant that manufactures PPOA. However, this result was not observed in an update to the study in which more specific exposure measures were used. 

Smoking has not been associated with an increased risk of prostate cancer, but smokers with prostate cancer have an increased mortality resulting from the disease when compared with nonsmokers with prostate cancer (relative risk 1.5 to 2). In addition, in a prospective cohort analysis, alcohol consumption was not associated with the development of prostate cancer. 

Recently, the results of three prospective cohort mortality studies have been reported (44,82,83). The design of these cohort studies has addressed weaknesses in the cross-sectional analyses of population statistics. Cohort studies analyze the incidence of health effects in a sample of individuals whose relevant personal characteristics are recorded along with the exposures in question. Measurement of smoking, sex, age, occupation, and other individual characteristics for each participant in the study allow for direct adjustment for hypothesized confounders. 

One other study deserves a mention. The Cancer Prevention Study 11 was a prospective investigation using a very large cohort of over one million adult Americans, in which the effects of commercial multivitamin supplements and vitamins A, C or E on mortality were studied, during a follow-up period of seven years. The results were complex in that the use of multivitamins plus vitamins A, C and/or E significantly reduced the risk of lung cancer in both former smokers and life-long non-smokers, but vitamins A, C and E apparently increased the risk in current smokers. 

A much larger cohort of 8854 men, 2293 of whom were exposed to acrylamide, from 1925 to 1983 was examined for mortality. This cohort consisted of four chemical plant populations. No statistically significant excess of all-cause or cause-specific mortality was found among acrylamide workers. Analysis by acrylamide exposure levels showed no trend of increased risk of mortality from several cancer sites. Although the authors concluded that the results do not support the hypothesis that aery-... 

In more detailed analysis of the mortality experience of this cohort up to year end 1977, the results of other studies relative to an excess of lung cancer were not confirmed, but there were indications of a higher than expected mortality in pancreatic cancer, lymphohe-matopoietic cancers, genitourinary cancer, nonmalignant respiratory disease, and benign and unspecified neoplasms. ... 

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