Mortality and cancer incidence among tire manufacturing workers hired in or after 1962

Our plain-English summary of Mortality and cancer incidence among tire manufacturing workers hired in or after 1962, by C. Beall, M. Corn, H. Cheng, et al (Journal of Occupational and Environmental Medicine, 2007).

The study

• Authors: C. Beall, M. Corn, H. Cheng, R. Matthews, E. Delzell
• Journal: Journal of Occupational and Environmental Medicine
• Published: 2007;49(6):680-90
• Cited by: 5 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

Objective: This study evaluated mortality during 1962 through 2003 and cancer incidence during 1995 through 2003 at a tire manufacturing plant.

Methods: The mortality study included 3425 men and women, employed for at least one year. Of these, 3069 were eligible for the cancer incidence study.

Results: Employees experienced 390 deaths compared with 608 expected (standardized mortality ratio (SMR)=64; 95% confidence interval (CI)=58-71). Total cancer mortality (123 observed, SMR=75, CI=62-89) and lung cancer mortality (47 observed, SMR=72, CI=53-96) were lower than expected. Hourly white men had small increases in stomach cancer, bladder cancer, and leukemia deaths. During 1995 through 2003, 169 incident cancers were observed compared with 197 expected (SIR=86, 95% CI=74-100). Three mesothelioma cases occurred among hourly white men (SIR=653, CI=135-1907); all were exposed potentially to asbestos before starting at the rubber plant.

Conclusions: Small numbers and limited information on jobs, occupational agents, and lifestyle preclude attribution of observed increases to workplace exposures.

In plain English

This study followed 3425 men and women who worked at least one year between 1962 and 2003 at a Goodyear tire plant in Tyler, Texas. It compared their death rates with those of the surrounding 15-county region. For 3069 workers who lived in Texas in or after 1995, it also compared their cancer rates during 1995 through 2003. There were 390 deaths against 608 expected, and deaths from cancer and from lung cancer were lower than expected. Long-term hourly white men had small increases in stomach cancer and leukemia deaths that were not statistically significant. Three mesothelioma cases occurred, all in hourly white men with 20 or more years since hire and 10 or more years worked. Among hourly men this was the only statistically significant excess (standardized incidence ratio 591, 95% confidence interval 122 to 1726). Two of the men had earlier worked at a plant making asbestos pipe insulation. The third had spent 20 years repairing Air Force communications equipment. The authors concluded the mesothelioma excess may be due to employment outside the tire plant. They noted missing work histories and lifestyle data, small numbers and a short incidence period.

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 study of mortality, with a cancer incidence follow-up. Workers' rates were compared with those of the general population of the surrounding region using standardized mortality and incidence ratios.
• Who was studied: 3425 men and women who worked at least one year between 1962 and the end of 2003 at the Goodyear Tire and Rubber Company tire plant in Tyler, Texas. Of these, 3069 who lived in Texas in or after 1995 were in the cancer incidence study.
• Exposure: Employment at a tire manufacturing plant. Personal air samples for many agents, including asbestos, were compared with workplace limits. During 1972 to 1988, 10 of 1192 samples exceeded the limit; during 1988 to 2006, 11 of 2311 did.
• Main results:
  • All employees: 390 deaths observed compared with 608 expected (SMR 64, 95% CI 58 to 71), using regional rates.
  • All employees: cancer deaths were lower than expected overall (123 deaths, SMR 75, CI 62 to 89).
  • All employees: lung cancer deaths were lower than expected (47 deaths, SMR 72, CI 53 to 96).
  • Hourly white men with 20 or more years since hire and 10 or more years worked: stomach cancer deaths 3 observed (SMR 347, CI 72 to 1015); leukemia deaths 4 observed (SMR 256, CI 70 to 656).
  • None of these small increases in deaths was statistically significant.
  • All employees, 1995 through 2003: 169 incident cancers observed compared with 196 expected (SIR 86, CI 74 to 100).
  • Hourly men: mesothelioma was the only statistically significant excess in cancer incidence (3 cases, SIR 591, CI 122 to 1726).
  • All 3 mesothelioma cases were in hourly white men with 20 or more years since hire and 10 or more years worked (SIR 966, CI 199 to 2823).
  • Two of the mesothelioma cases, one pleural and one peritoneal, had worked at a plant that manufactured asbestos insulation for pipe before starting at the tire plant.
  • The third mesothelioma case started at the tire plant at age 39, after 20 years repairing communications equipment in the Air Force and a few months as a pipeline welder.
  • Two white male hourly employees had mesothelioma on their death certificates. No comparison rates were available to estimate the expected number of mesothelioma deaths.
• The authors' conclusion: The authors concluded that the cancer incidence results did not indicate any increases likely to be due to exposures at the plant, and that the observed excess of mesothelioma may be due to employment outside the tire plant.
• Limitations the authors state:
  • Detailed work histories were lacking for many employees.
  • Some employees whose early jobs were hourly were probably misclassified as salaried.
  • Lack of lifestyle data, such as smoking, hampers interpretation of results for diseases like lung cancer.
  • The authors suspected confounding by smoking in the lung cancer results but could not confirm it.
  • The study group was small, so data on rare diseases were sparse.
  • The cancer incidence analysis covered only a short observation period.
  • Relying on the Texas Cancer Registry alone meant some cancer cases were missed.

Topics

Medical terms in this study, explained in our Lexicon: standardized mortality ratio (SMR), confidence interval, Lung Cancer, Stomach Cancer, Mesothelioma, Attribution.

Related studies

• Cohort study of workers employed in an Italian tire manufacturing plant, 1962-2004 — D. Mirabelli, A.M. Cacciatore, et al. (2012)
• Mortality and incidence of cancer among oil exposed workers in a Norwegian cable manufacturing company. Part I. Exposure conditions 1920-79 — A. Rønneberg, K. Skyberg (1988)
• A cancer incidence and mortality study of Dow Chemical Canada Inc. manufacturing sites — C. Burns, K. Harrison, et al. (2005)
• Cancer incidence among mild steel and stainless steel welders and other metal workers — K.S. Hansen, J.M. Lauritsen, et al. (1996)
• Employment characteristics and cause-specific mortality at automotive electronics manufacturing plants in Huntsville, Alabama — N. DeBono, D. Richardson, et al. (2019)
• Incidence of cancer and mortality among workers exposed to mercury vapour in the Norwegian chloralkali industry — D.G. Ellingsen, A. Andersen, et al. (1993)

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