Patterns of mortality among plumbers and pipefitters

Our plain-English summary of Patterns of mortality among plumbers and pipefitters, by K.P. Cantor, J.M. Sontag, M.F. Heid (American Journal of Industrial Medicine, 1986).

The study

• Authors: K.P. Cantor, J.M. Sontag, M.F. Heid
• Journal: American Journal of Industrial Medicine
• Published: 1986;10(1):73-89
• Cited by: 38 articles, as counted by NIH iCite
• Read it: PubMed · Publisher
• In J-M's library: Johns-Manville's company medical library held a copy (J-M no. 000382).

Abstract

A proportionate mortality ratio (PMR) study was undertaken of 7,121 members and retirees of the United Association of Plumbers and Pipefitters in California who died in 1960-79. The PMR for all malignant neoplasms was 1.24, with a major contribution from lung cancers (PMR = 1.41). Lung cancer PMRs were consistently elevated, through the 20-year study period, across the pipe trades and within different birth cohorts. Sixteen mesothelioma deaths occurred, suggesting asbestos as a risk factor. PMRs for malignancies of the stomach, kidney, brain, and lymphopoietic system were also elevated, especially among plumbers. Chronic rheumatic heart disease, emphysema, liver cirrhosis, and all external causes of death were the major non-cancer causes with significantly elevated PMRs. There were significant deficits in diabetes mellitus, all pneumonia, chronic nephritis, and vascular lesions of the central nervous system (CNS). PMRs for successive birth cohorts among all study subjects revealed decreasing emphysema risk, suggesting previous reduction of a risk factor for this disease. Among plumbers, PMRs for death due to several non-respiratory malignancies showed an increasing trend with recency of birth cohort.

In plain English

This proportionate mortality ratio (PMR) study compared causes of death among 7,121 white male members and retirees of California plumbers' and pipefitters' union locals who died in the U.S. in 1960-79 with the pattern expected for white U.S. men of the same ages and periods. Cancer made up a larger share of deaths than expected (PMR 1.24). Lung cancer (PMR 1.41) accounted for 185 of the 337 excess cancer deaths and was elevated in both plumbers and pipefitters. Mesothelioma was the underlying cause of sixteen deaths, against two expected. Twelve mentioned the pleura or a site suggesting it, one the peritoneum, and three an unspecified site. Plumbers also had elevated PMRs for stomach, kidney and brain cancer. The authors concluded that their results confirm earlier findings of increased respiratory cancer and mesothelioma risk in these trades. They judged asbestos likely an important contributor to the lung cancer excess. They cautioned that the PMR method can inflate cancer estimates, that smoking may explain part of the respiratory cancer excess, and that multiple testing may have produced chance findings.

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: Proportionate mortality ratio (PMR) study based on death certificates and union records. Cause-specific deaths were compared with expected proportions for white U.S. males by 5-year age and 5-year calendar period.
• Who was studied: 7,121 white male members and retirees of California locals of the United Association of Plumbers and Pipefitters who died in the U.S. between 1960 and 1979. By last recorded trade: 3,491 plumbers, 3,225 pipefitters, and smaller groups (metal trades, sprinkler fitters, lead burners, other or not recorded).
• Exposure: Work in the pipe trades (plumber or pipefitter), taken from union trade records. The authors describe these trades' exposures as including asbestos, metal fumes, gases from welding, brazing and soldering, and solvents. No asbestos fiber type is named.
• Main results:
  • Among all 7,121 decedents, the PMR for all malignant neoplasms was 1.24 and for lung cancer 1.41.
  • Lung cancer accounted for 185 of the 337 excess deaths from all malignant neoplasms in the whole group.
  • Among plumbers, there were 290 lung cancer deaths, PMR 1.38 (95% CI 1.23-1.54).
  • Among pipefitters, there were 310 lung cancer deaths, PMR 1.44 (95% CI 1.29-1.60).
  • Mesothelioma was the underlying cause of 16 deaths in the whole group, compared with two expected. The expected figure was based on data supplied by personal communication from the National Cancer Institute.
  • Of the 16 mesothelioma deaths, 12 mentioned the pleura or a site suggesting the pleura, one specified the peritoneum, and three were at unspecified sites.
  • Reported mesothelioma deaths rose in each 5-year period: one in 1960-64, three in 1965-69, four in 1970-74 and eight in 1975-79.
  • None of the mesothelioma deaths occurred among the 155 decedents whose death certificate gave a ship, boat or naval yard as usual industry.
  • Mesothelioma deaths were spread among plumbers and the other trades, not only pipefitters.
  • Among plumbers, PMRs were significantly elevated for all malignant neoplasms, stomach, lung, kidney and brain cancer, all lymphopoietic cancer, and lymphosarcoma/reticulosarcoma.
  • Among pipefitters, cancer sites other than lung did not show statistically significant excesses.
  • In the whole group, the major non-cancer causes with significantly elevated PMRs were chronic rheumatic heart disease, emphysema, liver cirrhosis and all external causes. There were significant deficits in diabetes mellitus, pneumonia, chronic nephritis and vascular lesions of the central nervous system.
  • Across all trades, the emphysema PMR fell from 1.77 in men born before 1900 to 0.55 in men born after 1919. The authors suggested that a causal exposure had decreased or been eliminated in the past.
  • In their discussion, the authors judged occupational asbestos exposure likely to be an important contributor to the lung cancer excess.
  • The authors calculated that smoking would account for a lung cancer risk ratio of about 1.14-1.29 in these trades. They judged that tobacco use alone was unlikely to fully explain the respiratory cancer excess.
• The authors' conclusion: The authors concluded that their results confirm and strengthen earlier findings of increased risk of respiratory cancer and mesothelioma among plumbers and pipefitters. They described elevated brain and kidney cancer PMRs, especially among plumbers, as new findings.
• Limitations the authors state:
  • In the PMR method, under-representation of some causes of death inflates the estimated risk for other causes.
  • A healthy worker effect may be operating, and PMR estimates of cancer risk are usually inflated under these conditions.
  • Because many significance tests were run, some associations may have arisen by chance.
  • PMRs could not be calculated by number of years worked in the trade, because information on first year of employment was of uneven quality.
  • Some of the respiratory cancer excess may be related to smoking, since these workers have been reported to smoke more than workers in other occupations.
  • Trends across birth cohorts and death periods were interpreted qualitatively, without formal tests for trend.

Topics

Medical terms in this study, explained in our Lexicon: Pipefitter, Neoplasm, Lung Cancer, Mesothelioma, Emphysema.

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