Mortality comparisons of chemical workers hired before, during, and after World War II (1941-1945)

Cause-specific mortality was evaluated by period of hire for 37,682 male chemical workers in order to test the hypothesis that employees hired during World War II (1941-1945) were at increased risk for selected causes of death. One recent study of refinery workers reported that those hired during the war years had experienced greater mortality from external causes (accidents, homicides, and suicides), alcoholism, and cancers of several sites relative to employees hired before or after the war. In the present study, employees were divided into three period-of-hire subcohorts: prior to 1941, 1941-1945 (World War II), and 1946 and after. Comparison of observed mortality among these subcohorts through 1982 was made with expected levels based on age- and calendar year-specific U.S. white male rats. Neither hourly nor salaried employees hired during the war showed evidence of higher mortality from homicide, suicide, alcoholism, or any of the selected cancer types suggested from the refinery study. Hourly, but not salaried, war years new hires experienced excessive mortality from only those accidents involving motor vehicles. Possible reasons for the discrepant findings between this and the earlier study of refinery workers are discussed, with methodological differences being dismissed.     

Long-term mortality of oil refinery workers. II. Comparison of the experience of active, terminated and retired workers

In occupational epidemiology a retrospective cohort study normally includes active, terminated, and retired employees and the mortality results may vary considerably if any of the three groups is excluded from the study. From a large refinery cohort of 12,526 white male workers followed between January, 1937 and January, 1978, the mortality experience of three groups (the active, terminated and retired) has been examined; detailed results, along with the merits and problems of studying these groups separately, are presented. The standardized mortality ratios (SMRs) for all causes are 0.68, 1.04 and 0.89 for the active, the terminated and the retired, respectively, and for all cancer, 0.85, 0.98 and 1.05. Significantly decreased SMRs are seen for most of the causes among the active and may be attributed to the "healthy worker effect." Exclusive study of active workers, although it may yield certain useful information, particularly on diseases of the young and those with short latency periods, is primarily a study of the healthy worker effect. Many favorable effects of the active worker will be encountered. The retirees as a whole experienced no significant excess mortality for any causes, although examination of a subgroup, the early retirees, did reveal a significant excess of deaths from diseases of the nervous system and sense organs. The retired may appear to be an ideal group for study because they usually have worked for an extended period of time, they may have experienced long-term occupational exposure and they have lived long enough to develop diseases with long latency periods; however, serious problems arise from studying only the retirees and these are discussed. The terminated group contributed 41% of the person-years, 49% of the total number of individuals and 38% of the deaths and is far too important to be omitted. Contrary to previous reports, the terminated did not demonstrate a significantly adverse mortality experience when compared with the general population, although they did not show the healthy worker effect that was seen among the active.     

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.     

Long-term follow-up mortality study of petroleum refinery and chemical plant employees

A previous report presented the 1948–1983 mortality patterns of the Shell Deer Park Manufacturing Complex employees who where employed for at least 3 months from 1948 through 1972. The present study updates the earlier investigation by extending the vital status follow-up through 1989 and by expanding the cohort to include employees hired after 1972. As in the previous study, the overall mortality and cancer mortality for both refinery and chemical employees were quite favorable compared to residents in the local population. Among refinery workers, cancers for which a suspicion of work-relatedness was raised in the previous study, i.e. leukemia and cancers of the central nervous system and biliary passage/liver, no supportive evidence was found in this update. For both refinery and chemical plant employees, the mortality rate due to cancers of all lymphopoietic tissue increased with increasing duration of employment; this finding was also noted by the original study. This was also evident for lymphoreticulasarcoma in refinery employees and for leukemia in chemical plant employees. However, elevations of cancers of all lymphatic and hematopoietic tissue are primarily confined to employees who started work at the complex before 1946. By contrast, deaths from cancer of all lymphatic and hematapoietic tissue for employees hired after 1945 were 22% lower than the comparison population. Seven deaths with mesothelioma mentioned on the death certificates were identified, with 3.2 deaths expected, resulting in a statistically nonsignicant SMR of 219. © 1996 Wiley-Liss, Inc.     

Mortality among workers at a nuclear fuels production facility

A retrospective cohort mortality study was conducted in a population of workers employed at a facility with the primary task of production of nuclear fuels and other materials. Data for hourly and salaried employees were analyzed separately by time period of first employment and length of employment. The hourly (N = 6,687 with 728 deaths) and salaried (N = 2,745 with 294 deaths) employees had a mortality experience comparable to that of the United States and, in fact, exhibited significant fewer deaths in many categories of diseases that are traditionally associated with the healthy worker effect. Specifically, fewer deaths were noted in the categories of all causes, all cancers, cancer of the digestive organs, lung cancer, brain cancer (hourly workers only), diabetes, all diseases of the circulatory system, all respiratory diseases, all digestive system diseases, all diseases of the genitourinary system (hourly only), and all external causes of death. A statistically significant, and as yet unexplained increase in leukemia mortality (6 observed vs. 2.18 expected) appeared among a subset of the hourly employees, first hired before 1955, and employed between 5-15 years.     

Vermont granite mortality study: an update with an emphasis on lung cancer

This mortality study extends the period of observation of an article published in 1988 of 5414 workers in Vermont granite sheds and quarries to assess whether previously reported reductions in silicosis and tuberculosis mortality were maintained. The relationship between lung cancer and quartz exposure is also examined by comparing mortality in workers hired before and after 1940, when dust controls were introduced and exposures were reduced by 80% to 90%. Before 1940, general stone shed air contained 20 million particles/cubic foot (mppcf) (approximately equivalent to 0.2 mg/m of quartz), and pneumatic chisel workers were exposed on average to 60 mppcf (approximately equivalent to 0.6 mg/m of quartz). Other workers had variable exposures. After 1940, a period of decline occurred in dust levels and then stabilized in approximately 1955, when average dust levels were 5 to 6 mppcf (equivalent to 0.05-.06 mg/m of quartz). Dust exposures in the Vermont industry is considered to be free of confounding occupational substances such as arsenic, although cigarette smoking was common. By the end of 1996, 2539 workers, or 46.9% of the cohort, had died. There were no silicosis deaths in workers hired after 1940 who were exposed only in the Vermont granite industry, illustrating the effect of lowering quartz exposures. Tuberculosis caused 2 deaths in those hired after 1940 (standardized mortality ratio [SMR] = 0.52; not significant). Overall lung cancer mortality was elevated in shed workers who had been exposed both to high levels of quartz before 1940 and to the lower levels prevailing after 1940 (SMR = 1.32; P < 0.01). Quarry workers did not show an excess of lung cancer (SMR = 0.73; not significant). When shed workers with high and low exposure histories (before and after 1940) but with comparable latency and tenure were contrasted, lung cancer mortality was similar. Differing levels of quartz exposure, which resulted in large differences in the mortality experience from silicosis, did not result in differences in lung cancer mortality. The results do not support the hypothesis that granite dust exposure has a causal association with lung cancer.     

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.     

An investigation of bias in a study of nuclear shipyard workers

The authors examined discrepant findings between a 1978 proportional mortality study and a 1981 cohort study of workers at the Portsmouth, New Hampshire, Naval Shipyard to determine whether the healthy worker effect, selection bias, or measurement bias could explain why only the proportional mortality study found excess cancer deaths among nuclear workers. Lower mortality from noncancer causes in nuclear workers (the healthy worker effect) partly accounted for the observed elevated cancer proportional mortality. More important, however, was measurement bias which occurred in the proportional mortality study when nuclear workers who had not died of cancer were misclassified as not being nuclear workers based on information from their next of kin, thereby creating a spurious association. Although the proportional mortality study was based on a small sample of all deaths occurring in the cohort, selection bias did not contribute materially to the discrepant results for total cancer deaths. With regard to leukemia, misclassification of occupation in the proportional mortality study and disagreement about cause of death accounted for some of the reported excess deaths.     

Retrospective mortality and medical surveillance studies of workers in benzene areas of refineries

The mortality and health experiences of refinery workers employed in benzene processes or operations are described. A retrospective cohort mortality study of benzene workers employed from 1952 to 1978 revealed no excess in overall general mortality or in cancer mortality compared either with the experience of the U.S. general population or with that of an internal control group. Ascertainment of vital status was accomplished for 99% of the cohort. Recent industrial hygiene data that included 1,394 personal samples indicated that 84% of all benzene exposures were less than 1 part per million (ppm), with a median exposure of 0.14 ppm for the refinery workers, and 0.53 ppm for those in the benzene-related units. Among these workers, no deaths from leukemia were observed. A medical surveillance program for benzene workers is also described, with special emphasis on the effectiveness of laboratory screening. Evaluation of data for a 21-year period showed no significant changes in the blood indices of the workers as a group. The limited value of establishing screening guidelines without the support of epidemiological studies is discussed.     

Non-Hodgkin's lymphoma and exposure to benzene in a multinational cohort of more than 308,000 petroleum workers, 1937 to 1996

Petroleum workers are exposed to benzene or benzene-containing petroleum products. As such, studies of these workers provide an opportunity for investigating the relationship between benzene and non-Hodgkin's lymphoma (NHL). However, few cohort studies of petroleum workers report results of NHL separately. One reason is that NHL is usually grouped with other lymphopoietic cancers in the analysis. Another reason is the relatively small number of NHL cases in some studies. To determine the risk of NHL in petroleum workers, we identified 26 cohorts of petroleum workers in the United States, the United Kingdom, Canada, Australia, Italy, and Finland. Authors of the original studies were contacted, and data on the number of observed deaths and person-years of observation were requested. Data from these studies were reviewed individually as well as combined in a pooled analysis (meta-analysis). In particular, results for individual cohorts, most of which had never been reported before, were presented. The combined multinational cohort consisted of more than 308,000 petroleum workers (6.6 million person-years), and the observation period covered an interval of 60 years from 1937 to 1996. A total of 506 NHL deaths were observed, compared with 561.68 expected. The standardized mortality ratio was 0.90 and the 95% confidence interval was 0.82 to 0.98. Analyses were performed by type of facility and industrial process. Stratum-specific standardized mortality ratios (95% confidence intervals) were 0.96 (0.86 to 1.07) for US refinery workers, 1.12 (0.90 to 1.37) for non-US refinery workers, 0.64 (0.50 to 0.82) for product (gasoline) distribution workers, and 0.68 (0.47 to 0.95) for crude oil workers. When individual cohorts were stratified by length of observation, no pattern was detected. In general, exposure levels before 1950 were much higher than thereafter. However, analysis of workers by hire date (< 1950, > or = 1950) revealed no difference in NHL mortality. Furthermore, none of the individual studies showed significant exposure-response relations. In summary, results from individual studies, as well as from the pooled analysis, indicated that petroleum workers were not at an increased risk of NHL as a result of their exposure to benzene or other benzene-containing petroleum products in their work environment. This conclusion was supported by cohort studies of workers in other industries who were exposed to benzene as well as by population-based case-control studies of NHL and occupational exposures.     

Cancer mortality of granite workers

A retrospective cohort study was undertaken to investigate the cancer mortality of granite workers. The study comprised 1,026 workers hired between 1940 and 1971. The number of person-years was 20,165, and the number of deaths 235. During the total follow-up 46 tumors were observed and 44.9 were expected. An excess mortality from tumors was observed for the workers followed for 20 years or more, the greatest excess occurring during the follow-up period of 25-29 years (observed 11, expected 5.2). Of the 46 tumors, 22 were lung cancers (expected 17.1) and 15 were gastrointestinal cancers (expected 9.7), nine of which were cancers of the stomach (expected 6.0). Mortality from lung cancer was excessive for workers with at least 15 years since entry into granite work (latency) (21 observed and 9.5 expected), being highest during the follow-up period of 25-29 years (observed 8, expected 2.1). The results indicate that granite exposure per se may be an etiologic factor in the initiation or promotion of malignant neoplasms.     

An epidemiological study of petroleum refinery employees.

A cohort study of 14179 current and former Chevron USA employees at the Richmond and El Segundo, California, refineries was conducted. The cohort consisted of everyone working at either refinery for a minimum of one year. The observed mortality of the cohort, by cause, was compared with the expected based on the United States mortality rates, standardised for age, race, sex, and calendar time. Analyses by refinery, job category, hire date, duration of employment, and latency were performed. For the entire cohort, mortality from all causes was 72.4% of that expected, a deficit that was statistically significant. In addition, a significantly lower mortality was found for all forms of cancer combined, digestive cancer, lung cancer, heart disease, non-malignant respiratory disease, diseases of the digestive system, and accidents. Only lymphopoietic cancer showed a pattern of increased risk suggestive of a possible relation to an occupational exposure. The excess appears confined to cancer of lymphatic tissue (not leukaemias) at Richmond, and only among those hired before 1948. A follow up case analysis of the deaths from lymphatic cancer failed to identify a common exposure pattern.     

A study of mortality in workers engaged in the mining, smelting, and refining of nickel. I: Methodology and mortality by major cause groups

Following the publication of the NIOSH nickel criteria document in 1977, the Joint Occupational Health Committee of the International Nickel Company (INCO) commissioned a mortality study of the company's Ontario workforce. This paper describes the detailed methodology and primary mortality results of the ensuing study; subsequent papers will describe more detailed findings of cause-specific mortality. An historical prospective mortality study of approximately 54,000 INCO workers has been conducted. Men with six months or more of service were followed for mortality during a 35-year period by computerized record linkage to the Canadian National Mortality Data Base. From a company-provided list of men known to have died and through independent follow-up of a random sample of 1,000 subjects of unknown status, we estimate a mortality ascertainment rate of 95%. Cause-specific standardized mortality ratios calculated with respect to Ontario provincial mortality rates indicate an excess of accidental deaths in men working in the Sudbury area and an excess of cancer deaths at the company's Port Colborne nickel refinery. A strong healthy worker effect was found for both all-disease mortality ad cancer mortality. The lower than expected mortality persisted for about 15 years beyond initial hiring.     

Gender differences in the healthy worker effect among synthetic vitreous fiber workers

The aim of this study was to determine whether the healthy worker effect and its component parts operate similarly for women and men. A cohort of workers from 14 synthetic vitreous fiber factories in seven countries, employed for at least 1 year between 1933 and 1977 and followed up to the early 1990s, included 375 deaths and 53,608 person-years among females and 2,568 deaths and 210,073 person-years among males. Standardized mortality ratios for all-cause and circulatory diseases were adjusted for country, age, calendar time, and gender. In addition, internal comparisons were adjusted for time since hire and employment status. The analyses addressed the following: 1) the healthy hire effect, 2) the time since hire effect, and 3) the healthy worker survivor effect. In this cohort, an overall healthy worker effect was not present in either gender. The healthy hire effect, based on standardized mortality ratios for years 1-4 since hire, was observed in males (standardized mortality ratio (SMR) = 0.8; 95% confidence interval (CI): 0.7, 1.0) but was less in females (SMR = 0.9; 95% CI: 0.5, 1.6). The relative risks increased slightly with time since hire in males but not in females. Higher mortality ratios were seen among those leaving employment than among those who remained actively employed; however, this effect was substantially greater for women (relative risk (RR) = 3.4; 95% CI: 1.8, 6.3) than men (RR = 1.8; 95% CI: 1.5, 2.1). The gender difference for active versus inactive status was stronger up to age 60 (men: RR = 1.7; 95% CI: 1.4, 2.0; women: RR = 3.6; 95% CI: 1.8, 7.1) than above that age. In conclusion, it appears that there is a stronger selection of healthy men than women into the workforce, while health-related selection out of the workforce is stronger for women than men.     

Cause of death among workers of a refinery in Rome]

We evaluated mortality among subjects employed in an oil refinery plant in Rome, Italy. We studied two subgroups of refinery employees: blue collar and white collar workers. A total of 682 men (505 blue collars, 148 white collars, 29 unknown) employed between 1965 and 1992, were followed up for mortality since employment in the plant to July 1999. Standardized Mortality Ratios (SMR), and their 90% Confidence Intervals (90% CI), comparing mortality rates of the cohort members with those of the general population of the Lazio region. For blue collar workers, we performed analyses by latency since first employment and by duration of employment for selected cancer sites. We observed 94 total deaths (100.8 expected) (SMR = 0.93; 90% CI = 0.78-1.11) among blue collar workers and 16 total deaths (31.7 expected) (SMR = 0.50; 90% CI = 0.32-0.77) among white collar workers, and a large deficit of deaths from non-neoplastic cardiovascular diseases (respectively SMR = 0.60; 90% CI = 0.41-0.86 and SMR = 0.18; 90% CI = 0.03-0.56). All cancer mortality was slightly increased only in blue collars (SMR = 1.27 CI = 0.97-1.65). There was an excess risk from cancer of the lung (20 obs SMR = 1.80, 90% CI = 1.19-2.62), bladder (5 obs SMR = 3.19, 90% CI = 1.26-6.72), and benign/unspecified cancer of the brain (4 obs SMR = 4.11, 90% CI = 1.12-10.6). The lower mortality from cardiovascular disease indicates the presence of a strong healthy worker effect. The findings of elevated mortality from cancer of the lung and bladder in blue collar workers are in agreement with those of other studies. Confounding factors from cigarette smoking might have played only a marginal role in influencing the results. Exposure to polynuclear aromatic hydrocarbons (PAHs) is a plausible explanation for the excesses found.     

A mortality study of workers at seven beryllium processing plants.

The International Agency for Research on Cancer (IARC) has found that the evidence for the carcinogenicity of beryllium is sufficient based on animal data but "limited" based on human data. This analysis reports on a retrospective cohort mortality study among 9,225 male workers employed at seven beryllium processing facilities for at least 2 days between January 1, 1940, and December 31, 1969. Vital status was ascertained through December 31, 1988. The standardized mortality ratio (SMR) for lung cancer in the total cohort was 1.26 (95% confidence interval [CI] = 1.12-1.42); significant SMRs for lung cancer were observed for two of the oldest plants located in Lorain, Ohio (SMR = 1.69; 95% CI = 1.28-2.19) and Reading, Pennsylvania (SMR = 1.24; 95% CI = 1.03-1.48). For the overall cohort, significantly elevated SMRs were found for "all deaths" (SMR = 1.05; 95% CI = 1.01-1.08), "ischemic heart disease" (SMR = 1.08; 95% CI = 1.01-1.14), "pneumoconiosis and other respiratory diseases" (SMR = 1.48; 95% CI = 1.21-1.80), and "chronic and unspecified nephritis, renal failure, and other renal sclerosis" (SMR = 1.49; 95% CI = 1.00-2.12). Lung cancer SMRs did not increase with longer duration of employment, but did increase with longer latency (time since first exposure). Lung cancer was particularly elevated (SMR = 3.33; 95% CI = 1.66-5.95) among workers at the Lorain plant with a history of (primarily) acute beryllium disease, which is associated with very high beryllium exposure. The lung cancer excess was not restricted to plants operating in the 1940s, when beryllium exposures were known to be extraordinarily high. Elevated lung cancer SMRs were also observed for four of the five plants operating in the 1950s for workers hired during that decade. Neither smoking nor geographic location fully explains the increased lung cancer risk. Occupational exposure to beryllium compounds is the most plausible explanation for the increased risk of lung cancer observed in this study. Continued mortality follow-up of this cohort will provide a more definitive assessment of lung cancer risk at the newer plants and among cohort members hired in the 1950s or later at the older plants. Further clarification of the potential for specific beryllium compounds to induce lung cancer in humans, and the possible contribution of other exposures in specific processes at these plants, would require a nested case-control study. We are currently assessing whether available industrial hygiene data would support such an analysis.     

Mortality of United Kingdom oil refinery and petroleum distribution workers, 1951-1998

The mortality experienced by cohorts of 28 630 oil refinery workers and 16 480 petroleum distribution workers has been investigated. Study subjects were all those male employees first employed in the period 1946-1974 at one of eight UK oil refineries or at one of 476 UK petroleum distribution centres; all subjects had a minimum of 12 months employment with some employment after 1 January 1951. The observed numbers of cause-specific deaths were compared with expectations based on national mortality rates. The resultant standardized mortality ratios (SMRs) were significantly below 100 for all causes, in both oil refinery workers (observed, 9341; expected, 10 649.7; SMR = 88) and petroleum distribution workers (observed, 6083; expected, 6460.3; SMR = 94). Significantly elevated SMRs were shown in oil refinery workers for cancer of the gall bladder (observed, 24; expected, 14.0; SMR = 172), cancer of the pleura (observed, 38; expected, 15.0; SMR = 254) and melanoma (observed, 36; expected, 22.2; SMR = 162). Significantly elevated SMRs were not found in petroleum distribution workers for any site of cancer. SMRs for selected causes of death were calculated by period from commencing employment, by year of hire and by job type. The only findings that suggested the presence of an occupational cancer hazard were an excess of mesothelioma in oil refinery workers and an excess of leukaemia in petroleum distribution workers, both excesses occurring in long-term follow-up for workers first employed >30 years ago.     

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

The mortality experience of 7,119 workers who were employed at a Beaumont, Texas, refinery for at least 1 year between 1945 and 1987 was investigated. Mortality analyses based on standardized mortality ratios (SMRs) and 95% confidence intervals (95%CI) showed overall mortality was significantly lower than expected compared with the U.S. general population (SMR <=;=> 82, 95%CI = 79–86). Total cancer mortality was also lower than expected (SMR = 92, 95% CI = 84–100). Significant mortality deficits from several malignant and nonmalignant diseases were reported. A significant mortality increase in the broad category of lymphatic and hematopoietic cancers was found (SMR = 133, 95%CI = 103–170). This increase was attributed to a nonsignificant elevation in leukemia of all cell types combined (SMR = 139, 95%CI = 92–201) and a borderline significant increase in other lymphatic tissue cancer (SMR = 158, 95%CI = 101–235). The elevation in leukemia was confined to workers hired before 1950. Furthermore, the leukemia excess was shown to have peaked during the 1960s, with mortality no longer elevated post-1980. Analyses of cell type-specific leukemias showed a similar temporal pattern for acute myeloid leukemia (AML) which was not significantly elevated (SMR = 136, 95%CI = 59–268). Mortality from other leukemia cell types was similar to or lower than expected. Mortality from non-Hodgkin's lymphoma (NHL) (SMR = 140, 95%CI = 88–211) and multiple myeloma (MM) (SMR = 121, 95%CI = 55–230) were increased, but neither was statistically significant nor likely to be related to refinery employment. No death from asbestosis was reported, and mortality from mesothelioma and pulmonary fibrosis was lower than expected. Lung cancer mortality for the overall cohort was similar to expected. For the overall cohort, analyses by duration of employment and time since first employment showed no evidence of any trends for increasing cause-specific mortality. Separate analyses of male workers employed in operator jobs showed mortality patterns that were more favorable than those of the total cohort. Maintenance craftworkers showed statistically significant elevations in mortality for prostate cancer (SMR = 145, 95%CI = 107–194), leukemia (SMR = 179, 95%CI = 111–273), and other lymphatic tissue cancer (SMR = 233, 95%CI = 138–368). Detailed analyses indicated that, among maintenance craftworkers, mortality was elevated for AML, NHL, and MM, but none was significant. Furthermore, no upward trend by duration of maintenance jobs was observed. A small increase of lung cancer was observed among maintenance craftworkers (SMR = 120, 95%CI = 99–145), which was borderline significant. No relationship between lung cancer and duration of maintenance employment was found. In contrast, a deficit of pulmonary fibrosis was reported among maintenance craftworkers (SMR = 62, 95%CI = 17–159). These findings are discussed in conjunction with results from other refinery studies, and the limitations of the study are discussed. Am. J. Ind. Med. 33:61–81, 1998. © 1998 Wiley-Liss, Inc.     

A retrospective cohort mortality study of blending and packaging workers of Mobil Corporation

This retrospective cohort mortality study examined 2,467 workers in lubrication products blending and packaging (B&P) operations at two refineries of Mobil Corporation between January 1, 1945 and December 31, 1978. Ninety-seven percent were male. Compared with U.S. males, there were significantly fewer deaths observed among males due to all causes, external causes, and diseases of the circulatory, respiratory, digestive, and genitourinary systems. Deaths observed from all cancer were fewer than expected, although not statistically significant. No statistically significant excess cause-specific mortality occurred at B&P facilities combined or separately. Nonsignificant increases in mortality were observed for cancers of the stomach, large intestine, prostate, the category of "other lymphatic tissue" cancer, and leukemia and aleukemia. Analyses demonstrated a statistically significant pattern of increasing SMR with employment duration for "other lymphatic tissue" cancer. Within the highest cumulative duration of employment category, the excess was confined to workers after 30 or more years since first employment. Although the interpretation of cancer mortality patterns is limited due to small numbers of deaths, the absence of associations with specific B&P departments is evidence against a causal interpretation.     

A 50-year historical cohort mortality study of workers in a pharmaceutical plant

An historical cohort study was conducted of workers at a pharmaceutical manufacturing plant. The cohort mortality experience of workers ever employed at the plant over the period from 1950 to 1999 was examined. The 1958 workers accumulated 44,294 person-years of experience at the plant, and a total of 384 deaths were identified. Our findings from external comparisons based on standardized mortality ratios (SMRs) in the cohort provide no evidence of excess mortality risk from all causes combined (SMR=0.75), all cancers combined (SMR=0.96), or from certain other individual causes of death. No patterns of excess mortality risk were apparent after stratifying on age and sex or job classification. The mortality experience of this cohort was generally more favorable than that of the general population.