A case-control study of lung cancer among refinery workers.

This case-control study examined the relationship between lung cancer and the work histories of male employees at a large Texas refinery. The study included 112 lung cancer deaths observed between 1946 and 1987 and 490 matched controls. Employment histories were obtained from personnel records, and smoking information was available from medical records. Both stratification methods and conditional logistic regression were used in data analyses. Overall employment in four general job categories (administrative, engineering/laboratory, process, maintenance/mechanical) was not associated with lung cancer mortality. Results by hire period (< 1940, 1940+) showed that workers hired into process jobs before 1940 had a nonsignificantly elevated odds ratio (OR) of 1.71 (95% confidence interval [CI] = 0.85-3.45) compared with nonprocess workers hired before 1940. Among process workers hired before 1940, there was a significant trend toward increasing OR with increasing duration of employment in process jobs, and the association with lung cancer was strongest among smokers in the highest duration category of 30+ years (OR = 2.98, 95% CI = 1.07-8.31). Latency analyses of process workers hired before 1940 indicated that their lung cancer risk had peaked between 30 and 50 years since first employment. Definitive statements about causal factors are limited because results among process workers were based on small numbers of subjects in some exposure categories, and there was no information on specific workplace exposures. The OR for maintenance/mechanical jobs after adjustment for smoking was 1.00 (95% CI = 0.55-1.82). Furthermore, there was no pattern in relation to duration of employment in maintenance/mechanical jobs. The results from this study do not support the hypothesis that work in maintenance/mechanical jobs increases lung cancer risk. On the basis of analyses in this study, it is unlikely that asbestos exposure contributed to excess lung cancer mortality. Additional analyses were conducted for specific maintenance jobs with potential exposure to asbestos and by duration in jobs with occasional or routine asbestos exposure. No significant increase in lung cancer was found in any subgroup. Furthermore, there was no significant trend toward lung cancer risk in relation to duration of employment in jobs with asbestos exposure.

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.

Updated mortality study of workers at a petroleum refinery in Torrance, California, 1959 to 1997.

The updated cohort consisted of 3328 workers who were employed at the Mobil (now ExxonMobil) Torrance, California, refinery for at least 1 year between 1959 and 1997. The vital status of the cohort was determined through a variety of sources, including company employment or retirement records, the Social Security Administration's Death Master File, and the National Death Index. The updated study covered an observation period of 38 years from 1960 to 1997, with a total of 60,612 person-years of observation. A total of 705 (21.2%) cohort members were identified as having died. Mortality data were analyzed in terms of cause-specific standardized mortality ratios (SMRs) and 95% confidence intervals (95% CIs), with expected deaths based on US national cause-, gender-, race-, year-, and age-specific mortality rates. The overall mortality of the cohort was significantly lower than expected when compared with the US general population (SMR, 81.9; 95% CI, 76.0 to 88.2). Overall cancer mortality was also lower than expected (SMR, 79.8; 95% CI, 67.9 to 93.1). For specific cancer sites, significant mortality deficits were observed for cancer of the digestive system (SMR, 70.9; 95% CI, 49.4 to 98.6) and cancer of the respiratory system (SMR, 74.1; 95% CI, 55.5 to 97.0). No significant increase was reported for any site-specific cancer. For nonmalignant diseases, no significant increase was observed for any cause. In particular, significant mortality deficits were reported for ischemic heart disease (SMR, 87.7; 95% CI, 77.2 to 99.3), chronic endocardial disease and other myocardial insufficiencies (SMR, 8.3; 95% CI, 0.2 to 46.0), all other heart disease (SMR, 64.2; 95% CI, 43.0 to 92.2), and influenza and pneumonia (SMR, 59.2; 95% CI, 33.1 to 97.6). Detailed analysis by length of employment did not reveal any significant mortality excess or upward trend. Analyses of male employees by job classification (process and maintenance) were conducted. Among maintenance workers, mortality from cirrhosis of the liver (SMR, 190.1; 95% CI, 101.2 to 325.1) and suicide (SMR, 208.6; 95% CI, 111.1 to 356.7) were significantly elevated. However, these mortality excesses did not seem to be related to employment at the refinery. No other causes of death showed significant increase among maintenance workers. A similar separate analysis was conducted for process workers, and no significant excess was detected for any cause. The findings from the present study are discussed in conjunction with results from previous investigations of employees at the Torrance refinery and with results from other refinery studies. Potential limitations of the study are also discussed.