A case-control study of lung cancer among refinery workers

A Bayesian approach to assess interaction between known risk factors: the risk of lung cancer from exposure to asbestos and smoking

We review the literature on the combined effect of asbestos exposure and smoking on lung cancer, and explore a Bayesian approach to assess evidence of interaction. Previous approaches have focussed on separate tests for an additive or multiplicative relation. We extend these approaches by exploring the strength of evidence for either relation using approaches which allow the data to choose between both models. We then compare the different approaches.

Assessing the combined effect of asbestos exposure and smoking on lung cancer: a Bayesian approach

We review the literature on the combined association between lung cancer and two environmental exposures, asbestos exposure and smoking, and explore a Bayesian approach to assess evidence of interaction between the exposures. The meta-analysis combines separate indices of additive and multiplicative relationships and multivariate relative risk estimates. By making inferences on posterior probabilities we can explore both the form and strength of interaction. This analysis may be more informative than providing evidence to support one relation over another on the basis of statistical significance. Overall, we find evidence for a more than additive and less than multiplicative relation.

Asbestos Exposure and Cancer Mortality among Petroleum Refinery Workers: A Poisson Regression Analysis of Updated Data

The authors investigated the relationship between asbestos exposure and respiratory cancer mortality among maintenance workers and other blue-collar workers at an Italian oil refinery. The cohort contained 931 men, 29,511 person-years, and 489 deaths. Poisson regression analysis using white-collar workers as an internal referent group provided relative risk estimates (RRs) for main causes of death, adjusted for age, age at hiring, calendar period, length of exposure, and latency. Among maintenance workers, RRs for all tumors (RR = 1.50), digestive system cancers (RR = 1.41), lung cancers (RR = 1.53), and nonmalignant respiratory diseases (RR = 1.71) were significantly increased (p < 0.05); no significant excess was found for all causes and among maintenance (RR = 1.12) and other blue-collar workers (RR = 1.01). Results confirm the increased risk of death from respiratory diseases and cancer among maintenance workers exposed to asbestos, whereas other smoking-related diseases (circulatory system) were not statistically different among groups.

An updated mortality study of workers at a petroleum refinery in Beaumont, Texas, 1945 to 1996

The present investigation represents an update of a previous cohort mortality study of 7543 workers who were employed at a petroleum refinery in Beaumont, Texas, for at least 1 year between 1945 and 1996. The updated study covered an observation period of 51 years, from 1946 to 1996, with a total of 208,627 person-years of observation. A total of 3020 (40.0%) cohort members were known to have died. The mortality data were analyzed in terms of cause-specific standardized mortality ratios (SMRs) and 95% confidence intervals (95% CIs). The overall mortality of the cohort was significantly lower than expected when compared with that of the general US population (SMR, 95.7; 95% CI, 92.3 to 99.2). Overall cancer mortality was also lower than expected (SMR, 85.8; 95% CI, 79.4 to 92.5). For specific cancer sites, significant mortality deficits were observed for the following: buccal cavity and pharynx, esophagus, large intestine, rectum, larynx, lung, and bladder and other urinary organs. No significant increase was reported for any site-specific cancer. A non-significant increase in acute myeloid leukemia was observed among male employees (SMR, 147.2; 95% CI, 76.1 to 257.2). Detailed analyses indicated that the excess was restricted to workers hired before 1950. No increase was detected for other leukemia cell-types, non-Hodgkin's lymphoma, or multiple myeloma. For non-malignant diseases, the majority of SMRs were below 100, and no significant increase was observed for any cause. In particular, significant mortality deficits were reported for ischemic heart disease (SMR, 91.0; 95% CI, 85.4 to 96.9), non-malignant respiratory disease (SMR, 61.5; 95% CI, 52.2 to 72.0), pulmonary fibrosis (SMR, 51.0; 95% CI, 22.0 to 100.4), cirrhosis of the liver (SMR, 47.2; 95% CI, 30.6 to 69.7), and accidents (SMR, 81.7; 95% CI, 66.3 to 99.6). Separate analyses of male workers by job classification (process and maintenance) were conducted. Mortality from acute myeloid leukemia was elevated among employees in maintenance jobs (8 observed deaths vs 4.31 expected; SMR, 185.5; 95% CI, 80.1 to 365.6). However, no upward trend by length of service was found. A detailed analysis indicated that the acute myeloid leukemia mortality excess was limited to maintenance workers who were hired before 1950. No other significant excess was detected for any cause among maintenance or process workers. These findings from the present study were discussed in conjunction with results from previous investigations of employees at the Beaumont refinery and with results from other refinery studies. Potential limitations of the study were also discussed.

A critical review of cancer epidemiology in the petroleum industry, with a meta-analysis of a combined database of more than 350,000 workers

In 1989 we published a critical review of cancer epidemiology in petroleum workers, which included as a component of the review a meta-analysis by cancer site. Subsequently we have completed three additional reviews and meta-analyses on cell-type-specific leukemias (1995), multiple myeloma (1997), and non-Hodgkin's lymphoma (2000). The objective of the present investigation was to update our 1989 review and meta-analysis of nonlymphohematopoietic cancers in cohort studies of petroleum workers. Included in the present investigation were cohort studies of petroleum workers from the United States, the United Kingdom, Canada, Australia, Finland, Sweden, and Italy. Individual studies were reviewed with regard to specific cancer sites. For each cancer of interest, risk ratios from the individual studies were presented. In some studies, subcohort analyses stratified by exposure parameters such as length of employment, job category, and hire year were also reported. These subcohort or stratified analyses were reviewed and the results of these analyses were taken into consideration in our interpretation. In addition to the qualitative review of individual studies, a meta-analysis was performed to combine data from individual cohort studies of petroleum workers. The primary purpose of the meta-analysis was to provide a summary measure of risk for each cancer site. Based on a review and meta-analyses of cohort studies of more than 350,000 petroleum workers in the United States, the United Kingdom, Canada, Australia, Finland, Sweden, and Italy, we concluded that there was no increased mortality from digestive cancers (stomach, large intestine, liver, or pancreas), lung cancer, bladder cancer, kidney cancer, or brain cancer. The summary standardized mortality ratios for these cancer sites were all below unity. Significant increases of melanoma mortality were reported in some small groups of refinery workers in the United Kingdom and upstream operation workers in Canada, but no responsible agent(s) had been identified. The observed mortality from skin cancer in all other studies was similar to the expected. In particular, no significant increase of skin cancer mortality was reported in any of the U.S. studies. Elevated mortality from prostate cancer was noted in short-term workers at a U.S. refinery and in short-term workers employed in certain crafts at U.S. crude oil operations. However, the absence of an upward trend by length of employment in these workers argued against an association between exposure to petroleum products and prostate cancer. For all petroleum workers as a whole, mortality from prostate cancer was as expected.