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 were 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 lymphoreticulosarcoma 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 hematopoietic 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 nonsignificant SMR of 219.

Mortality among employees at a plastics and resins research and development facility.

OBJECTIVES: The study was undertaken to update a previous study of employees from a resins and plastics research and development facility and to further examine the mortality of these employees with particular emphasis on deaths due to pancreatic cancer. METHODS: This retrospective cohort study examined mortality from 1962 to 1992 for 257 men who were employed for at least one year during a 14 year period from 1962 to 1975 at a plastics and resins research and development facility. During the operative period, the primary activities involved applications and process development for polypropylene, polystyrene, epoxy resins, and to a lesser extent high density polyethylene. RESULTS: The cohort was young and was followed up for an average of 26 years. Although mortality for all causes among employees who worked at least one year at this facility was low (standardised mortality ratio (SMR) 0.74), the death rate from cancer was moderately higher than that of the general population (14 observed and 9.4 expected deaths). There were four observed and 0.5 expected deaths from pancreatic cancer among men who worked at this facility for at least one year, which resulted in a statistically increased SMR of 8.88 (95% confidence interval 2.42-22.74). All cases of pancreatic cancer had "laboratory" jobs, and their ages at death were relatively young compared with deaths in the general population from pancreatic cancer. Lung cancer mortality was high but not significant with seven observed and 3.5 expected deaths. There were no deaths due to non-malignant respiratory disease (1.9 expected). CONCLUSIONS: The increased cancer mortality was entirely due to excess deaths from pancreatic and lung cancers. No causative agent or process for these cases of pancreatic cancer has been identified. This study shows no increased colorectal cancer mortality as was found among another group of workers involved in the manufacture of polypropylene.

Mortality, morbidity, and haematological results from a cohort of long-term workers involved in 1,3-butadiene monomer production.

A retrospective mortality analysis and prospective morbidity and haematological analyses were performed for Shell Deer Park Manufacturing Complex (DPMC) male employees who worked in jobs with potential exposure to 1,3-butadiene from 1948 to 1989. 614 employees qualified for the mortality study (1948-89), 438 of those were still employed during the period of the morbidity study (1982-9), and 429 of those had haematological data available for analysis. Industrial hygiene data from 1979 to 1992 showed that most butadiene exposures did not exceed 10 ppm (eight-hour time weighted average (8 hour TWA)), and most were below 1 ppm, with an arithmetic mean of 3.5 ppm. 24 deaths occurred during the mortality study period. For all causes of death, the standardised mortality ratio (SMR) was 48 (95% confidence interval (95% CI) = 31-72), and the all cancer SMR was 34 (95% CI = 9-87). There were only two deaths due to lung cancer (SMR 42, 95% CI = 5-151) and none due to lymphohaematopoietic cancer (expected = 1.2). Morbidity (illness absence) events of six days or more for the 438 butadiene employees were compared with the rest of the complex. No cause of morbidity was in excess for this group; the all cause standardised morbidity ratio (SMbR) was 85 (95% CI = 77-93) and the all neoplasms SMbR was 51 (95% CI = 22-100). Haematological results for the 429 with laboratory data were compared with results for the rest of the complex. No significant differences occurred between the two groups and the distributions of results between butadiene and non-butadiene groups were virtually identical. These results suggest that butadiene exposures at concentrations common at DPMC in the past 10-20 years do not pose a health hazard to employees.

A cohort mortality study of two California refinery and petrochemical plants.

This study examined the 1973 to 1989 mortality experience of Shell's two California manufacturing locations' employees who worked more than 6 months before December 31, 1989 and pensioners who were alive as of January 1, 1973. Vital status of each employee as of December 31, 1989 was determined from various sources including company records, the National Death Index, and the Social Security Administration's Master Beneficiary Record file. The study included many long-term employees, with more than half (57%) of the total population working 20 years or longer. The total population exhibited 11% lower all causes mortality and 20% lower cancer mortality, as compared with the California general population. There were no significant excesses of any cause-specific mortality including cancer. Among total employees, mortality for several cancer sites showed a statistically nonsignificant increase, for example, cancer of the kidney (8 observed deaths and 6.02 expected), cancer of the bladder (11 observed deaths and 9.17 expected), and Hodgkin's disease (2 observed deaths and 1.01 expected). A review of these work histories revealed no predominant work area or job assignment. In contrast to the ecologic studies based on local county rates, lung cancer mortality in this study was significantly lower (Standardized Mortality ratio [SMR] = 0.73). In addition, statistically significant deficits in mortality were found for cirrhosis of the liver (SMR = 0.63) and all external causes of death (SMR = 0.74). This study also failed to show an increased mortality rate for cancers of the brain, stomach, and prostate--causes which have been reported to be elevated in other refinery and petrochemical employee studies.

A prospective study of morbidity patterns in a petroleum refinery and chemical plant.

This study examined the morbidity experience from 1981 to 1988 of a prospective cohort of 3422 refinery and petrochemical plant employees from the Shell Deer Park manufacturing complex. The morbidity data for this study, which include all illness and absence records in excess of five days, were extracted from the morbidity section of the Shell health surveillance system. Standardised morbidity ratios (SMRs) of disease prevalence in this cohort were calculated using an internal comparison group of all manufacturing employees of the Shell Oil Company. Among production employees, the overall morbidity was statistically significantly higher (SMR = 109) than that of the comparison group. Illness due to hypertension (SMR = 144), haemorrhoids (SMR = 149), diseases of the nervous system (SMR = 120), respiratory system (SMR = 108), and digestive system (SMR = 117) were also raised for this group. The increased risk due to these medical conditions does not appear to be associated with occupational factors. Lymphatic and haematopoietic tissue neoplasms were raised (SMR = 124), but were based on only four cases.

Personal and job characteristics of musculoskeletal injuries in an industrial population.

A cross-sectional study was conducted of 10,350 full-time regular employees who worked at Shell Oil Company's manufacturing facilities between 1987 and 1989. Two hundred seventy-five employees with low-back and 456 with nonlow-back musculoskeletal injuries were compared with 8295 employees who did not have musculoskeletal injuries during this period. Based on morbidity data collected from a prospective health surveillance system, this study shows that estimated relative risks (RRs) for low-back injuries are significantly higher among smokers (RR = 1.54, P less than .01) and overweight persons (RR = 1.42, P less than .01). This observation is also true for nonlow-back musculoskeletal injury (RR = 1.23, P = .05 for smokers and RR = 1.53, P less than .01 for overweight persons). In addition, persons in potentially more physically demanding jobs (primarily maintenance job titles) had an increased RR for both low-back and nonlow-back musculoskeletal injuries (RR = 1.57, P less than .01 and RR = 1.35, P = .02, respectively). The findings of this study suggest that it may be possible to reduce the impact of musculoskeletal injury through implementation of an integrated injury prevention program. Such programs would include not only the traditional elements of job factors evaluation and modifications, employee education and training, and an overall increased attention to ergonomics but also medical counseling and support for personal fitness programs, workplace smoking cessation programs, and weight-reduction programs.

Morbidity patterns among employees at a petroleum refinery.

This study examined the morbidity experience of a prospective cohort of 2132 male employees who worked at a petroleum refinery from 1981 through 1988. The morbidity data included all illness-absence episodes in excess of 5 days during the study period. Standardized morbidity ratios (SMRs) of disease prevalence were calculated using data from all manufacturing employees of the Shell Oil Company as an internal comparison group. As such, there is no potential bias associated with the "healthy worker effect" in this type of study design. Morbidity for all causes combined was virtually the same as that for the comparison group with 2,311 observed and 2,318 expected disease prevalence events. However, there were statistically increased prevalence of musculoskeletal system disorders (SMR = 136) and injuries (SMR = 125) among staff employees and skin and subcutaneous tissue disorders (SMR = 138) among production employees. A review of the original morbidity reports for these skin conditions revealed that none were due to exposure to chemical products or solvents. The SMR for neoplasms of the lymphatic and hematopoietic tissue among production employees was slightly elevated but was based on only three cases (2.4 expected). Of the three cases, none was due to leukemia.

Medical surveillance for leukemia at a petrochemical manufacturing complex: four-year summary.

Four-year results are presented on 2086 participants of a medical surveillance program of current and retired employees at a manufacturing complex in Illinois. Annual complete blood cell count testing and intensive follow-up of all out-of-normal-range results began in 1985 on a voluntary basis. The program to date has not identified any evidence for an unusual distribution of out-of-range complete blood cell count results. Active employees with out-of-range complete blood cell count values had no increase in adverse health outcomes compared with those with in-range values. Retired employees with out-of-range values were more likely to have a serious underlying medical condition, but this appeared to be more a function of age than of occupational exposure. Four cases of myelodysplastic syndrome were brought to our attention as a result of the program, but there is no similarly followed population available for comparison to determine whether this represents an increase over expected cases. The lack of correlation of out-of-range complete blood cell count results in active employees with serious hematologic disease raises significant questions about the utility of such surveillance for chemically exposed groups (eg, benzene-exposed workers) when exposure levels are low and well controlled.

Prospective morbidity surveillance of Shell refinery and petrochemical employees.

Results for a prospective morbidity study of 14,170 refinery and chemical workers from 1981 through 1988 are presented. Illness/absence data for this study were extracted from the morbidity section of the Shell Health Surveillance System which includes records of all illness/absences in excess of five days. Age adjusted annual morbidity frequency rates and annual durations of absence are presented by age, sex, job, and work status. Generally, rates and durations of absence were highest for older age groups, women, and production workers. Increased risk was associated with the presence of known disease risk factors. Overall, 48% of the employees had at least one illness/absence in excess of five days during the eight year period. Twelve per cent of the employees had four or more absences, which accounted for 54% of the total number of absences and 52% of the total work days lost. Among men, the five most common conditions accounted for 72% of all illness/absences. In descending order they were injuries (25%), respiratory illnesses (17%), musculoskeletal disorders (14%), digestive illnesses (9%), and heart disease (7%). Similar patterns were noted among women. These findings may be useful in setting priorities and directing efforts such as health education programmes and other strategies for the prevention of disease.

Morbidity prevalence study of workers with potential exposure to epichlorohydrin.

This study examined the morbidity experience from 1981 to 1988 of two cohorts (Shell cohort and Enterline cohort) of workers who had potential exposure to epichlorohydrin (ECH). The morbidity prevalence data for this study were extracted from the morbidity section of the Shell health surveillance system which included all illness and absence records in excess of five days. For both cohorts, the standardised morbidity ratios (SMRs) for all causes and all neoplasms were similar to an internal comparison group. There were no increases in heart disease morbidity for the Shell cohort (SMR = 97) or the Enterline cohort (SMR = 90). The SMRs for heart disease in the lower exposure group of the Shell cohort were 101 and 93 for the corresponding Enterline cohort. They were 92 and 87, respectively, in the higher exposure group. The increased risk of heart disease mortality reported by Enterline et al in workers more heavily exposed to ECH was not confirmed in this morbidity study. Morbidity from skin and subcutaneous tissue disorders, however, was found to be increased significantly in the Shell cohort. The SMR was 98 for the lower exposure group and 195 for the higher exposure group. A review of the original morbidity reports for each case suggested that factors unrelated to exposure to ECH such as the physical demands of a particular job, amount of time outside--for example, exposure to poison ivy--and other underlying medical conditions may be of greater importance than exposure to ECH.

Smoking and morbidity frequency in a working population.

As part of Shell's health surveillance program, morbidity frequency and severity by smoking status (current smoker, exsmoker, nonsmoker) were compared for the 3-year period 1985 through 1987. Morbidity data for this study were extracted from the morbidity section of the Shell Health Surveillance System, which included all illness and absence events in excess of 5 days. Statistically significant positive associations were seen between smoking habits and overall morbidity, diseases of the circulatory system, and diseases of the respiratory system for both male and female employees. In addition, a significantly increased association between smoking and both non-motor vehicle accidents and motor vehicle accidents among current smokers was noted. Current smokers had a greater than 60% higher frequency rate (P less than .05) for non-motor vehicle accidents than nonsmokers for both men and women. Male smokers also had a 75% increased (P less than .05) motor vehicle accident rate. These results suggest that it may be possible to reduce overall illness and injury morbidity through implementation of successful smoking cessation programs.

Cancer of the larynx: occupational and environmental associations.

This paper briefly reviews the available evidence for the influence of environmental and occupational factors in the development of cancer of the larynx. Although several occupational exposures have been suggested to play a role in the etiology of this disease, few have been convincingly confirmed. The strong association between smoking and cancer of the larynx, the weaker but still important association between alcohol consumption and cancer of the larynx, and the strong synergism between the two is emphasized. Other accepted or suspected environmental and occupational factors are also discussed.

Medical effects of combined industrial exposures.

The problem of combined workplace exposures has been long recognized but rarely written about. This article explores some of the problems of approaching and defining-combined exposures, reviews several categories of combined exposures, and emphasizes a practical preventive medicine approach to combined exposures. It is hoped that this article will stimulate other papers in this area.

The efficacy of percutaneous liver biopsy in the initial staging of patients with lymphoma.

To evaluate the usefulness of percutaneous needle liver biopsy in the initial staging of lymphoma patients, 115 patients presenting to M. D. Anderson Hospital between Sept 1, 1972, and Aug 31, 1975, and having either percutaneous (45) or celiotomy (70) liver biopsy were identified. Sixty-six patients had Hodgkin's disease, 49 non-Hodgkin's lymphoma. Overall, results of 13 biopsies were positive--six by percutaneous biopsy, seven by celiotomy. Results showed little difference in yield between percutaneous and celiotomy biopsy. Positivity increased with increasing clinical stage, increasing age (Hodgkin's patients), and increasing number of abnormal liver function tests. It is concluded that percutaneous liver biopsy is useful in lymphoma staging, especially in patients with at least one abnormal liver function test, and in patients with Hodgkin's disease, mixed cell type. The early identification of otherwise unrecognized stage IV disease can spare many patients the morbidity of staging celiotomy.