A survey of occupational cancer in the rubber and cablemaking industries: results of five-year analysis, 1967-71

Our plain-English summary of A survey of occupational cancer in the rubber and cablemaking industries: results of five-year analysis, 1967-71, by A.J. Fox, D.C. Lindars, R. Owen (British Journal of Industrial Medicine, 1974).

The study

• Authors: A.J. Fox, D.C. Lindars, R. Owen
• Journal: British Journal of Industrial Medicine
• Published: 1974;31(2):140-51
• Cited by: 65 articles, as counted by NIH iCite
• Read it: PubMed · Publisher · Free full text
• In J-M's library: Johns-Manville's company medical library held a copy (J-M no. 002352).

Abstract

Fox, A. J., Lindars, D. C., and Owen, R. (1974).British Journal of Industrial Medicine,31, 140-151. A survey of occupational cancer in the rubber and cablemaking industries: results of five-year analysis, 1967-71. A mortality study of 40 867 subjects employed in the rubber and cablemaking industries on 1 February 1967 is reported. No evidence is found of a continued excess risk of neoplasms of the bladder in people who entered the industry after 1949. For those employed before that date, during the period when known bladder carcinogens were in use, the SMR is higher than predicted, indicating that men are still dying with occupationally induced tumours. An excess of all neoplasms was noted in the five years of the study. In certain sections of the industry (tyre manufacture, belting hose rubber with asbestos, and flooring industry) there is a particular excess of bronchial carcinoma. In those sections which use asbestos such an excess is not altogether surprising, but this does not apply to the tyre industry. The latter industry is sufficiently large (16 035 men in the study compared with 4 350 in the belting, hose rubber with asbestos, and flooring industry) for attention to be focused on particular operations. Two job groups are found to share the excess: moulding, press, autoclave, and pan curemen; and finished goods, packaging, and despatch. Job selection may play a part in the latter, as the work is generally considered suitable for older and perhaps less healthy people. Crude analyses have been undertaken to indicate whether the excesses are due to regional differences or to the population comprising an abnormally high proportion of smokers. No excesses are found in other smoking-related diseases. Although the effects of differences in smoking habit and regional differences cannot be ruled out, the indications are against these factors being the primary cause. The difficulties of this type of study are discussed. It is emphasized that the results can be used only as an indication of a problem area and the type of further study required. A more exact study would concentrate on five-year cohorts of people who left the industry between 1940 and 1960. A study of five-year cohorts of people who entered the industry in the same period would also be valuable. An attempt has been made to perform the latter, but it would be hazardous to draw too many conclusions from this because the population comprises those who `survive' in the industry until 1967.

In plain English

This was a mortality study of 40 867 men aged 35 to 65 who were working in the rubber and cablemaking industries in Great Britain on 1 February 1967. Their deaths were followed through 1971, and deaths in 1968-71 were compared with the numbers expected from national death rates. Across the whole group there was a statistically significant excess of deaths from all cancers (659 observed, 572 expected). Bladder cancer deaths (23 observed, 20 expected) were not significantly raised in any exposure group. In the tyre sector there were 131 deaths from bronchial carcinoma against 97.8 expected. The section listed as belting, hose rubber with asbestos, and flooring had 4 350 men. In that section, the article's table shows 42 bronchial carcinoma deaths and a standardized mortality ratio of 164, where 100 would mean the number expected from national rates. The authors wrote that, because this group came into contact with asbestos and other chemicals, this was not altogether surprising. They added that the asbestos levels these workers met needed study. No smoking records were kept. The authors said smoking and urban effects could not be ruled out, especially in this asbestos section. The authors concluded that the evidence was not conclusive and should serve only as a basis for further study.

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: Mortality study of a working population identified by a 1967 census, comparing observed deaths with deaths expected from national (England and Wales) rates (standardized mortality ratios)
• Who was studied: Men aged 35 to 65 employed in the rubber and cablemaking industries in Great Britain (381 firms) on 1 February 1967. Of 41 981 suitable subjects, 40 867 were traced through National Health Service central registers. Deaths were followed 1967-71, with 1967 excluded from the statistical comparisons.
• Exposure: Men were sorted into exposure groups by use of known bladder carcinogens (benzidine, alpha- and beta-naphthylamine) in their factories, before or after 1950. They were also sorted by industry sector, including industrial group 6, 'belting, hose rubber with asbestos, flooring', and by job held on 1 February 1967. Asbestos fiber type and exposure levels were not reported.
• Main results:
  • Whole study population, 1968-71: significant excess of deaths from all neoplasms (659 observed, 572 expected, SMR 115, p less than 0.001)
  • Bladder cancer, 1968-71: 23 deaths observed against 20 expected overall. Group A (entered factories using known carcinogens before 1950): 11 observed, 8.5 expected, SMR 130. Group B: 7 observed, 7.2 expected, SMR 97. Group C: 5 observed, 4.4 expected, SMR 114. None of these was statistically significant. The authors said this was not conclusive evidence of no risk, but suggested that any excess is small.
  • Tyre sector (16 035 men): significant excesses of all neoplasms (273 observed, 217.4 expected, P less than 0.001) and of carcinoma of the bronchus (131 observed, 97.8 expected, P less than 0.001)
  • Industrial group 6 (belting, hose rubber with asbestos, flooring), 1968-71: Table 8 gives 42 deaths from carcinoma of the bronchus, with an SMR of 164 (marked p less than 0.001). The expected number is printed illegibly as '25i67'.
  • The authors wrote that the excess in group 6 was not altogether surprising because this group comes into contact with asbestos as well as other chemicals. They said further study was needed to discover the asbestos levels involved.
  • Two tyre-sector job groups had marginally significant excesses of bronchial carcinoma, but on extremely small numbers. These were moulding, press, autoclave and pan curemen (15 observed, 8.37 expected, SMR 179) and finished goods, stores, packaging and despatch (13 observed, 6.75 expected, SMR 193).
  • As a check on smoking and urban effects, the authors compared the tyre sector with the remainder of the industry using Merseyside rates. Bronchitis and emphysema came out about 8% lower in the tyre sector, while bronchial carcinoma came out about 24% higher. The authors took this to suggest that neither smoking nor urban effects were likely to be the primary cause of the tyre-sector excess.
• The authors' conclusion: The authors concluded that the evidence was not conclusive and should be used only to form hypotheses for further study. They named specific tyre jobs and the belting, hose rubber with asbestos, and flooring industry for initial attention.
• Limitations the authors state:
  • No information on smoking habits was collected
  • Smoking and urban effects could not be entirely ruled out, particularly for the belting, hose rubber with asbestos, and flooring industry, where SMRs for most diseases were raised
  • The population was largely a survivor population, because many earlier workers had left the industry or died
  • Jobs were recorded only as of 1 February 1967, so earlier jobs and job rotation were not accounted for
  • The screening comparisons between industry sectors used crude expected values that ignored differences in age structure
  • The belting, hose rubber with asbestos, and flooring industry was small (about one quarter the size of the tyre industry), which made detailed analysis difficult

Topics

Medical terms in this study, explained in our Lexicon: Neoplasm, Carcinoma, Habit.

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