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.

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.

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.

A framework for addressing health issues in or near a manufacturing facility.

Clustering of health events in or around industrial facilities sometimes leads to worker and community concerns that plant management or local health professionals must address. We provide an eight-step process to deal with these concerns systematically. We emphasize the use of good scientific practices with managerial oversight for effective worker and community communication. This process is directed to plant management and the local health professional and emphasizes the practical aspects of the investigation.

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.

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.

Multiple myeloma and benzene exposure in a multinational cohort of more than 250,000 petroleum workers.

Case reports have suggested an association between benzene exposure and multiple myeloma. Because petroleum workers are exposed to benzene or benzene-containing liquids, studies of these workers provide an opportunity for investigating the relationship between benzene and multiple myeloma. A large number of cohort studies of petroleum workers have been conducted. However, few of them have reported results of multiple myeloma separately. One reason is that multiple myeloma is usually grouped with other lymphopoietic cancers in the analysis. Another reason is that multiple myeloma is relatively rare, and few individual studies are large enough to provide reliable risk estimates. To determine the risk of multiple myeloma in petroleum (refinery, distribution, production, and pipeline) workers, we have identified 22 cohort mortality studies of petroleum workers in the United States, the United Kingdom, Canada, and Australia. Authors of these studies were contacted, and data on the number of observed deaths and age-specific person-years of observation were requested. Data from individual studies were combined in a pooled analysis (meta-analysis). In addition to the pooled analyses, results for individual cohorts, most of which have never been reported before, are also presented. The combined multinational cohort consisted of more than 250,000 petroleum workers, and the observation period covered an interval of 55 years from 1937 to 1991. A total of 205 deaths from multiple myeloma were observed, compared to 220.93 expected, a total derived from respective national mortality rates. The corresponding standardized mortality ratio (SMR) was 0.93 and the 95% confidence interval (95% CI) was 0.81-1.07. Additional analyses were performed by type of facility and industrial process. Stratum-specific SMRs (95% CIs) were 0.92 (0.77-1.09) for refinery workers and 0.93 (0.69-1.23) for distribution workers. When individual cohorts were stratified by length of observation, no pattern was detected. The pooled analysis indicates that petroleum workers are not at an increased risk of multiple myeloma as a result of their exposure to benzene, benzene-containing liquids, or other petroleum products in their work environment. This conclusion is supported by cohort studies of workers in other industries who were exposed to benzene as well as by population-based case-control studies of multiple myeloma and occupational exposures.

Application of meta-analysis in reviewing occupational cohort studies.

Meta-analysis has been used increasingly in reviewing and summarising epidemiological studies. Reviews incorporating meta-analyses have appeared in medical journals in increasing numbers. Although there are several methodology papers on meta-analysis, most of these papers have been written primarily for discussion among epidemiologists. The present paper considers some of the basic methodological issues, the more practical aspects of meta-analysis, and targets an audience of mainly non-epidemiologists. Thus, the main objective of this paper is to provide some basic guidelines for non-epidemiologists to evaluate meta-analysis in occupational cohort studies. In this methodology paper, the limitations and problems of traditional qualitative reviews are pointed out. Some of these problems can be dealt with by quantitative meta-analysis. The potential limitations and benefits of quantitative meta-analysis are discussed. Rather than replacing traditional qualitative review, quantitative meta-analysis should be made part of the overall assessment. The term "meta-review" is proposed to emphasise the importance of both qualitative and quantitative components in a comprehensive review process. The basic steps in a meta-review are outlined, with a discussion on how to recognise and avoid some of the problems which are likely to occur at each step. A meta-review is useful in selecting studies, and in organising, presenting, and summarising results from individual studies. A meta-review can also be used to detect heterogeneity among studies. Major benefits of conducting a meta-analysis (the quantitative component in a meta-review) include the increase in statistical power and the estimate of a properly weighted summary risk estimate.

Leukemia mortality by cell type in petroleum workers with potential exposure to benzene.

Workers in the petroleum industry are potentially exposed to a variety of petrochemicals, including benzene or benzene-containing liquids. Although a large number of studies of petroleum workers have been conducted to examine leukemia and other cancer risks, few existing studies have investigated cell-type-specific leukemias. One of the major reasons for the lack of cell-type-specific analysis was the small number of deaths by cell type in individual studies. In the present investigation, all cohort studies of petroleum workers in the United States and the United Kingdom were combined into a single database for cell-type-specific leukemia analysis. The majority of these workers were petroleum refinery employees, but production, pipeline, and distribution workers in the petroleum industry were also included. The combined cohort consisted of more than 208,000 petroleum workers, who contributed more than 4.6 million person-years of observation. Based on a meta-analysis of the combined data, cell-type-specific leukemia risks were expressed in terms of standardized mortality ratios (meta-SMRs). The meta-SMR for acute myeloid leukemia was 0.96. The lack of an increase of acute myeloid leukemia was attributed to the low levels of benzene exposure in the petroleum industry, particularly in comparison to benzene exposure levels in some previous studies of workers in other industries, who had been found to experience an increased risk of acute myeloid leukemia. Similarly, no increase in chronic myeloid, acute lymphocytic, or chronic lymphocytic leukemias was found in petroleum workers (meta-SMRs of 0.89, 1.16, and 0.84, respectively). Stratified meta-analyses restricted to refinery studies or to studies with at least 15 years of follow-up yielded similar results. The findings of the present investigation are consistent with those from several recent case-control studies of cell-type-specific leukemia. Patterns and levels of benzene exposure in the petroleum industry are reviewed. The results of the present epidemiologic investigation are discussed in conjunction with recent advances in leukemogenesis from other scientific disciplines.

An updated cohort mortality study of workers at a northeastern United States petroleum refinery.

An update of a cohort study of 4855 employees at a Paulsboro, New Jersey refinery was conducted to further examine mortality patterns. The earlier study investigated refinery workers employed for a minimum of 1 year between 1 January 1946 and 1 January 1979. The vital status of these workers was ascertained through 1979. The update extended enrollment in the study and vital status follow-up for an additional 8 years (1980-1987). As in the previous study, mortality from all causes [standardized mortality ratio (SMR) = 87; 95% confidence interval (95% CI): 83-91] was significantly lower than expected compared with the general population. Total cancer mortality was also lower than expected (SMR = 96; 95% CI: 86-106). A borderline significant mortality increase in prostatic cancer was found (SMR = 144; 95% CI: 106-190). This increase was similar to the nonsignificant increase reported in the original study (SMR = 135; 95% CI: 90-196). The excess was of comparable magnitude among white males and nonwhite males, although it was not significant for the latter. Detailed analysis indicated that the prostatic cancer was not likely to be related to employment at the refinery. Mortality from lymphatic and hematopoietic cancers was similar to the expected mortality. Mortality from overall leukemia was as expected and detailed analyses by specific cell type showed no increase. An increase in mortality occurred from non-Hodgkin's lymphoma among male workers (SMR = 132; 95% CI: 74-217). The increase was not statistically significant and unlikely to be associated with refinery employment. Mortality from multiple myeloma among male employees was lower than expected (SMR = 74; 95% CI: 20-190). Mortality from asbestos-related diseases (pulmonary fibrosis, lung cancer, malignant mesothelioma) was also lower than expected among male workers. No cause-specific mortality was found to be associated with duration of employment at the refinery, including several causes which have been reported to be elevated in previous studies. The findings of this updated study indicate, as in the previous report, the generally favorable mortality experience of Paulsboro refinery workers.

Cell-type-specific leukemia analyses in a combined cohort of more than 208,000 petroleum workers in the United States and the United Kingdom, 1937-1989.

A large number of epidemiologic studies of workers in the petroleum industry have been conducted to investigate the carcinogenic and other health effects of exposure to petroleum products during manufacture and distribution. Of particular interest is the relationship between exposure to benzene or benzene-containing liquids in the petroleum industry and leukemia risk. However, few studies have investigated cell-type-specific leukemia risk. In the present investigation, all cohort studies of petroleum workers in the United States and the United Kingdom were combined into a single database for cell-type-specific leukemia analysis. The majority of these workers were petroleum refinery employees, but production, pipeline, and distribution workers in the petroleum industry were also included. The combined cohort consisted of 208,741 petroleum workers. Between 1937 and 1989, these workers contributed a total of 4,665,361 person-years of observation. More than 56 thousand deaths were reported among these workers during the 53 years of observation. Cell-type-specific leukemia risks were calculated using a meta-analysis procedure appropriate for combining occupational cohort studies. These risks were expressed in terms of cell-type-specific leukemia standardized mortality ratios (meta-SMRs). The meta-SMR for acute myelogenous leukemia was 0.96. The lack of an increase of acute myelogenous leukemia was attributed to the low levels of benzene exposure in the petroleum industry, particularly in comparison to benzene exposure levels in some previous studies of workers in other industries, who had been found to experience increased risk of acute myelogenous leukemia. Similarly, no increase in chronic myelogenous, acute lymphocytic, or chronic lymphocytic leukemias was found in petroleum workers (meta-SMRs of 0.89, 1.16, and 0.84, respectively). Meta-analyses restricted to refinery studies or to studies with at least 15 years of follow-up yielded similar results. The findings of the present investigation are consistent with those from several recent case-control studies.

Review of the carcinogenic potential of gasoline.

This review examines the animal, human, and mechanistic studies that precede the new studies reported in this volume. Wholly vaporized unleaded gasoline was found to produce a dose-dependent increase in renal carcinoma in male rats and an excess above background incidence of hepatocellular tumors in female mice in the high-dose group. Mechanistic studies suggest that gasoline is not mutagenic and that the probable mechanism for the male rat renal tumors involves a rat-specific protein, alpha 2u-globulin, whose binding with highly branched aliphatic compounds results in renal tubule cell death and, in turn, a proliferative sequence that increases renal tubule tumors. Human evidence generated predominantly from studies of refinery workers does not support a kidney or liver cancer risk in humans. The current epidemiologic database is inadequate to access leukemia risk from low-level benzene exposure from gasoline. Studies of gasoline-exposed workers that incorporate quantitative exposure information are needed.

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.

Critical review of cancer epidemiology in petroleum industry employees, with a quantitative meta-analysis by cancer site.

A critical review of close to 100 published and unpublished but otherwise available epidemiologic reports of petroleum industry employees from the United States, United Kingdom, Canada, Europe, Australia, and Japan was conducted. Analyses by duration of employment and latency are discussed, and summary standardized mortality ratios (SMRs) or meta-SMRs are developed for selected cancer sites. Findings indicate that the industry experienced a significantly lower cancer mortality than the general population for all cancer sites combined, digestive system, stomach, and lung. For the industry as a whole, SMRs similar to the general population were observed for skin, brain, pancreatic, prostatic, and kidney cancers. However, some data indicate that certain small groups within the industry might have elevated prostatic and kidney cancer risk. This review supports the conclusion that some refinery employees, particularly those employed before the 1940s, may have been at increased risk of leukemia. There is some indication that cancer of other lymphatic tissue may also be elevated. Unresolved issues affecting these conclusions are discussed, and specific directions for future research are offered.