Update of the Texaco mortality study 1947-93: Part II. Analyses of specific causes of death for white men employed in refining, research, and petrochemicals

Our plain-English summary of Update of the Texaco mortality study 1947-93: Part II. Analyses of specific causes of death for white men employed in refining, research, and petrochemicals, by B.J. Divine, C.M. Hartman, J.K. Wendt (Occupational and Environmental Medicine, 1999).

The study

• Authors: B.J. Divine, C.M. Hartman, J.K. Wendt
• Journal: Occupational and Environmental Medicine
• Published: 1999;56(3):174-80
• Cited by: 36 articles, as counted by NIH iCite
• Read it: PubMed · Publisher · Free full text

Abstract

Objective: To examine patterns of mortality for specific causes of death with increases in the Texaco mortality study to determine if the patterns are related to employment in the petroleum industry.

Methods: Mortality patterns by duration of employment in various job groups were examined for mesothelioma, non-Hodgkin's lymphoma, multiple myeloma, cell type specific leukaemia, and brain tumours.

Results: Mortality from mesothelioma was examined for the total cohort and for two maintenance groups with the greatest potential for exposure to asbestos. The insulator group had a standardised mortality ratio (SMR) of 3029, and a larger group consisting of insulators, carpenters, labourers, electricians, pipefitters, boiler-makers, and welders had an SMR of 411. The mortalities from mesothelioma increased with increasing duration of employment. Mortality was lower for those first employed after 1950. An analysis of all brain tumours for the total cohort and some job and unit subgroups resulted in an SMR of 178 for those employed on the units related to motor oil and 166 for those employed as laboratory workers. Mortality from brain tumours in both of these job groups was higher for those employed > or = 5 years in the group. An analysis of non-Hodgkin's lymphoma showed no consistent patterns among the various employment groups. Mortality from multiple myeloma was non-significantly increased among people employed on the crude (SMR = 155) and fluid catalytic cracking units (SMR = 198). Leukaemia mortality was not increased for the total cohort, and a cell type analysis of leukaemia mortality for the total cohort showed no significant increases for the major cell types. However, there were significant increases for acute unspecified leukaemia (SMR = 276) and leukaemia of unknown cell type (SMR = 231).

Conclusions: Analyses of specific causes of death by duration of employment in various job and process units did not show any patterns which suggest that, other than for mesothelioma, any of these increases in mortalities were likely to have resulted from workplace exposures or from employment at one of the places included in the Texaco mortality study.

In plain English

This was a further analysis of the Texaco mortality study of white men employed at company refineries, petrochemical plants and research laboratories, 1947 to 1993. Deaths were compared with numbers expected from United States rates; a standardised mortality ratio (SMR) of 100 means deaths equalled expectation. The whole cohort had 44 deaths with mesothelioma on the death certificate, an SMR of 297 (95% confidence interval 216 to 399). Men employed as insulators for more than one year had an SMR of 3029 (95% CI 1510 to 5420; 11 deaths). Men employed for more than one year as insulators, pipefitters, welders, labourers, boilermakers, electricians or carpenters had an SMR of 411 (95% CI 275 to 590; 29 deaths). Mesothelioma rates rose with longer employment and were higher for men first employed before 1950. The article did not name asbestos fibre types. Lung cancer was not significantly increased in these job groups, and no smoking data were available. Brain tumours, non-Hodgkin's lymphoma, multiple myeloma and leukaemia were also examined. The authors concluded that, apart from mesothelioma, the increases were not likely to have resulted from workplace exposures.

We wrote this plain-English summary from the full article with the help of AI, and a second AI model checked each sentence against the article. It is not the authors' wording; the abstract and the article are their own account.

What the study did and found

• Design: Retrospective cohort mortality study (an update of the Texaco mortality study), comparing observed deaths with deaths expected from United States rates using standardised mortality ratios (SMRs)
• Who was studied: White men employed at Texaco refineries, petrochemical plants and research laboratories in the United States, followed from 1947 to 1993. The study cohort was described as over 28 840 workers.
• Exposure: Potential asbestos exposure from asbestos-containing thermal insulation on refinery vessels and pipes, estimated by job: insulators, and a wider maintenance group (insulators, pipefitters, welders, boilermakers, carpenters, electricians, labourers). No fibre type is named. Other analyses used job and process unit groups (motor oil units, laboratories, fluid catalytic cracking unit, crude stills and others) as stand-ins for chemical exposures.
• Main results:
  • Whole cohort: 44 deaths had any mention of mesothelioma on the death certificate. The mesothelioma SMR was 297 (95% CI 216 to 399), which was statistically significant.
  • Men employed as insulators for more than one year (printed as '>1 year'): 11 mesothelioma deaths, SMR 3029 (95% CI 1510 to 5420).
  • Men employed for more than one year (printed as '>1 year') as insulators, pipefitters, welders, labourers, boilermakers, electricians or carpenters: 29 mesothelioma deaths, SMR 411 (95% CI 275 to 590).
  • Mesothelioma SMRs rose with longer employment in each group. The highest was among insulators in the longest-duration category of 20 years or more (SMR 9916). In the wider maintenance group, men in that category had 16 deaths and an SMR of 1053 (95% CI 601 to 1710).
  • SMRs were higher for men first employed before 1950. Insulators first employed before 1950 had 9 deaths, SMR 4586 (95% CI 2092 to 8706). Insulators first employed in 1950 and after had 2 deaths, SMR 1200 (95% CI 134 to 4335), which was still significant. In the wider group, men first employed in 1950 and after had 4 deaths, SMR 230 (95% CI 62 to 591).
  • Men never employed in the maintenance subgroup had 7 mesothelioma deaths against 5.3 expected (SMR 130). Men never employed in any maintenance job had 2 deaths against 3.9 expected (SMR 51).
  • Lung cancer (excluding mesothelioma deaths coded as lung cancer): no SMR in the insulator or wider maintenance groups was statistically significant. The whole-cohort lung cancer SMR was 67 (95% CI 61 to 73; 537 deaths).
  • All brain tumours combined, whole cohort: 85 deaths against 75 expected, SMR 113 (95% CI 90 to 140). Motor oil unit workers: SMR 178 if ever employed, and 326 (95% CI 140 to 643) if employed 5 years or more. Laboratory staff: SMR 166 if ever employed, and 185 (95% CI 103 to 305) if employed 5 years or more.
  • Multiple myeloma was non-significantly increased among men ever employed on the fluid catalytic cracking unit (SMR 198, 95% CI 79 to 408) and on the crude unit (SMR 155, 95% CI 70 to 294). None of the non-Hodgkin's lymphoma SMRs was significant.
  • Leukaemia by cell type, whole cohort: acute myelogenous leukaemia SMR 129 (95% CI 78 to 199), not significant. There were significant excesses for acute unspecified leukaemia (15 deaths, SMR 276, 95% CI 154 to 455) and leukaemia of unspecified cell type (15 deaths, SMR 231, 95% CI 129 to 381).
• The authors' conclusion: The authors concluded that, apart from mesothelioma, the patterns did not suggest that any of the increases in deaths were likely to have resulted from workplace exposures or employment at the study locations. Mesothelioma rose with duration of employment and was higher in job groups with greater potential for asbestos exposure.
• Limitations the authors state:
  • No smoking histories were available for the cohort.
  • There were no measurements of asbestos exposure levels for the crafts until the 1970s, by which time work practices had already changed.
  • No information on previous employment, such as wartime shipbuilding, was available.
  • Mesothelioma has no specific code in ICD-8, and published mesothelioma death rates were lacking. Expected numbers were therefore based on cancer incidence data, with assumed rates for the 1950s and 1960s. As a result, comparability with other studies is unknown.
  • Cell type information for leukaemia on death certificates is much less accurate than the leukaemia diagnosis itself.
  • Information on specific chemical exposures by job and unit was not available. Job groupings gave little information linking exposure and outcome.
  • In many groups the numbers of deaths, especially among more recently employed workers, were too small to interpret easily.

Topics

Medical terms in this study, explained in our Lexicon: Mesothelioma, Myeloma, Insulator, Pipefitter.

Related studies

• Dangerous and cancer-causing properties of products and chemicals in the oil refining and petrochemical industry: Part V--Asbestos-caused cancers and exposure of workers in the oil refining industry — M.A. Mehlman (1991)
• Dangerous and cancer-causing properties of products and chemicals in the oil-refining and petrochemical industries. Part IX: Asbestos exposure and analysis of exposures — M.A. Mehlman (1991)
• Mortality among maintenance employees potentially exposed to asbestos in a refinery and petrochemical plant — S.P. Tsai, L.C. Waddell, et al. (1996)
• Update of the Texaco mortality study 1947-93: Part II — M.M. Finkelstein (2000)
• Update of mortality and cancer incidence in the Australian petroleum industry cohort — R.T. Gun, N. Pratt, et al. (2006)
• Maintenance work and asbestos-related cancers in the refinery and petrochemical sector — M.M. Finkelstein (1999)

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