Workplace risk factors for cancer in the German rubber industry: Part 1. Mortality from respiratory cancers

Our plain-English summary of Workplace risk factors for cancer in the German rubber industry: Part 1. Mortality from respiratory cancers, by S.K. Weiland, K. Straif, L. Chambless, et al (Occupational and Environmental Medicine, 1998).

The study

• Authors: S.K. Weiland, K. Straif, L. Chambless, B. Werner, K.A. Mundt, A. Bucher, T. Birk, U. Keil
• Journal: Occupational and Environmental Medicine
• Published: 1998;55(5):317-24
• Cited by: 24 articles, as counted by NIH iCite
• Read it: PubMed · Publisher · Free full text

Abstract

Objectives: To determine the cancer specific mortality by work area among active and retired male workers in the German rubber industry.

Methods: A cohort of 11,663 male German workers was followed up for mortality from 1 January 1981 to 31 December 1991. Cohort members were classified as active (n = 7536) or retired (n = 4127) as of 1 January 1981 and had been employed for at least one year in one of five study plants producing tyres or technical rubber goods. Work histories were reconstructed with routinely documented "cost centre codes" which were classified into six categories: I preparation of materials; II production of technical rubber goods; III production of tyres; IV storage and dispatch; V maintenance; and VI others. Standardised mortality ratios (SMRs) adjusted for age and calendar year and 95% confidence intervals (95% CIs), stratified by work area (employment in respective work area for at least one year) and time related variables (year of hire, lagged years of employment in work area), were calculated from national reference rates.

Results: SMRs for laryngeal cancer were highest in work area I (SMR 253; 95% CI 93 to 551) and were significant among workers who were employed for > 10 years in this work area (SMR 330; 95% CI 107 to 779). Increased mortality rates from lung cancer were identified in work areas I (SMR 162; 95% CI 129 to 202), II (SMR 134; 95% CI 109 to 163), and V (SMR 131; 95% CI 102 to 167). Mortality from pleural cancer was increased in all six work areas, and significant excesses were found in work areas I (SMR 448; 95% CI 122 to 1146), II (SMR 505; 95% CI 202 to 1040), and V (SMR 554; 95% CI 179 to 1290).

Conclusion: A causal relation between the excess of pleural cancer and exposure to asbestos among rubber workers is plausible and likely. In this study, the pattern of excess of lung cancer parallels the pattern of excess of pleural cancer. This points to asbestos as one risk factor for the excess deaths from lung cancer among rubber workers. The study provides further evidence for an increased mortality from laryngeal cancer among workers in the rubber industry, particularly in work area I.

In plain English

This study followed 11,663 male blue collar workers from five German rubber plants making tyres or technical rubber goods for deaths from 1981 through 1991. All were working or retired on 1 January 1981. Their death rates were compared with those of West German men using standardised mortality ratios (SMRs), which divide the observed number of deaths by the number expected from national rates. Workers were grouped by work area, not by measured asbestos exposure. Seventeen men died of pleural cancer (SMR 401; 95% CI 234 to 642). For 16 of them, the death certificate recorded pleural mesothelioma. Pleural cancer deaths were raised in all six work areas, significantly in materials preparation, technical rubber goods production and maintenance. Lung cancer deaths were also raised (257 deaths, SMR 130; 95% CI 115 to 147), significantly in the same three areas. The authors judged asbestos exposure probably highest in materials preparation, where asbestos and asbestos contaminated talc were used as fillers. They concluded that a causal link between asbestos and the pleural cancer excess was plausible and likely, and that asbestos might be one risk factor for the lung cancer excess.

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: Historical (retrospective) cohort mortality study comparing deaths with national reference rates using standardised mortality ratios (SMRs), analysed by work area
• Who was studied: 11,663 male German blue collar workers (7,536 active and 4,127 retired as of 1 January 1981) employed at least one year at five German plants producing tyres or technical rubber goods; followed from 1 January 1981 to 31 December 1991; reference population was men of German nationality in former West Germany
• Exposure: Employment of at least one year in one of six work areas, reconstructed from company cost centre codes: I preparation of materials; II production of technical rubber goods; III production of tyres; IV storage and dispatch; V maintenance; VI others. Asbestos was not measured. The authors state that asbestos exposure was probably highest in work area I, where asbestos and asbestos contaminated talc were used as fillers. They state it also occurred in work area II, in heat resistant technical rubber goods production, and among maintenance workers. They add that talc used as anti-tacking material may have been contaminated with asbestos. No fiber type is named.
• Main results:
  • Pleural cancer in the whole cohort: 17 deaths, SMR 401 (95% CI 234 to 642). This was the highest relative risk for any cause of death in the cohort.
  • Pleural mesothelioma was recorded on the death certificates of 16 of the 17 pleural cancer deaths. Necropsy reports were available for three cases, and all three confirmed pleural mesothelioma. All 17 deaths occurred more than 20 years after hire.
  • Pleural cancer was increased in all six work areas, significantly in work areas I, II and V. Work area II (technical rubber goods): 7 deaths, SMR 505 (95% CI 202 to 1040). Work area V (maintenance): 5 deaths, SMR 554 (95% CI 179 to 1290). Work area I (preparation of materials): 4 deaths, SMR 448; its confidence interval is printed differently in the table and the abstract (see text problems). Most excess deaths occurred among workers hired before 1960.
  • Lung cancer in the whole cohort: 257 deaths, SMR 130 (95% CI 115 to 147). It was significantly increased in work area I (80 deaths, SMR 162; 95% CI 129 to 202), work area II (99 deaths, SMR 134; 95% CI 109 to 163) and work area V (67 deaths, SMR 131; 95% CI 102 to 167). The increase in work area III was of borderline significance (SMR 127; 95% CI 99 to 161).
  • Among workers hired after 1960, lung cancer was increased in all work areas except VI (SMRs between 135 and 188). The increase was significant in work areas II and V.
  • Laryngeal cancer in the whole cohort was slightly and not significantly increased: 13 deaths, SMR 129 (95% CI 69 to 221). The highest SMR was in work area I: 6 deaths, SMR 253 (95% CI 93 to 551). Among men in the longest employment category in work area I (printed as more than 10 years), the increase was significant: 5 deaths, SMR 330.
• The authors' conclusion: The authors concluded that a causal relation between asbestos exposure and the excess of pleural cancer among rubber workers is plausible and likely. They noted that the pattern of lung cancer by work area paralleled that of pleural cancer, which might point to asbestos as one risk factor for increased lung cancer mortality in some groups of rubber workers. They said the study gives further evidence of increased laryngeal cancer mortality in the rubber industry, which may also be related to asbestos.
• Limitations the authors state:
  • The cohort was limited to men alive and working or retired on 1 January 1981. The authors say this could create a cohort of survivors and underestimate risk, or could overestimate risk.
  • Cost centre codes assign workers to work areas but give no information on specific jobs or tasks.
  • Comparing SMRs between work areas or with other studies must be done cautiously, because SMRs depend on the age distribution of each group.
  • Numbers of pleural cancer deaths by work area are small.
  • Lung cancer risks might be confounded by smoking, which was not measured in this cohort.
  • The role of specific carcinogens, including asbestos, could not be assessed with the available data.

Topics

The National Library of Medicine indexes this study under subjects our site covers: Lung cancer, Throat and laryngeal cancer.

Medical terms in this study, explained in our Lexicon: confidence interval, Laryngeal Cancer, Lung Cancer.

Related studies

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