A proportional study of cancer registrations of dockyard workers

Our plain-English summary of A proportional study of cancer registrations of dockyard workers, by K.P. Lumley (British Journal of Industrial Medicine, 1976).

The study

• Author: K.P. Lumley
• Journal: British Journal of Industrial Medicine
• Published: 1976;33(2):108-14
• Cited by: 24 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. 001115).

Abstract

Evidence of an occupational effect due to asbestos exposure was sought by comparing cancer registrations for dockyard workers with those for Plymouth men in the same age groups for 1960-69. The results show a significant excess of pleural tumours in the dockyard group but no significant excesses at other sites. Registrations for pleural mesothelioma were recorded for men with many dockyard occupations and the observed mean interval between first exposure to asbestos and registration for a pleural tumour (37.6 years) indicates that cases of pleural mesothelioma may be expected to occur among these workers for many years, even though crocidolite is no longer used in naval ships. A trend of increasing annual excess of stomach and gastrointestinal registrations was observed in the dockyard group. No cases of peritoneal mesothelioma were recorded but it is likely that some did occur which were diagnosed as cancers arising from other sites. This may account for some of the excess of gastrointestinal registrations.

In plain English

This study compared cancer registrations for workers at the Royal Naval dockyard in Devonport, Plymouth, with those for all males in the Plymouth area, dockyard workers included, using regional cancer registry records for 1960-69. Of 4998 registrations for Plymouth males aged 15 and over, 1377 were for dockyard workers. The age make-up of the dockyard workforce was unknown, so the author used a proportional method that compares each cancer's share of all registrations. Dockyard workers had 23 pleural tumour registrations against 8.1 expected, a statistically significant excess. These were 22 pleural mesotheliomas and one pleural endothelioma, compared with three pleural mesotheliomas in other Plymouth men. Excesses of lung, stomach and pancreatic cancer were not statistically significant. No peritoneal mesothelioma was registered. Where this was known (19 men), the average time from first asbestos exposure to registration for a pleural tumour was 37.6 years. The author concluded that pleural mesothelioma cases may keep occurring among these workers for many years. The author suggested that some peritoneal mesotheliomas may have been diagnosed as other gastrointestinal cancers. Workers could not be grouped by asbestos exposure.

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: Proportional registration study comparing cancer registry records for dockyard workers with those for all Plymouth males, dockyard workers included
• Who was studied: Cancer registrations at the Plymouth office of the South Western Regional Cancer Registry, 1960-69, for males aged 15 and over living in the Plymouth area: 4998 registrations, of which 1377 were for dockyard workers (current and retired) at the Royal Naval Base, Devonport
• Exposure: Employment at Devonport naval dockyard, where the author states many men had varying exposure to crocidolite (blue), amosite and chrysotile asbestos before strict precautions were introduced. Individual exposure was not measured for the comparison.
• Main results:
  • Pleural tumours in dockyard workers: 23 observed against 8.1 expected, a Proportional Registration Ratio (PRR) of 282.7, statistically significant
  • The pleural excess consisted of 22 pleural mesotheliomas and one pleural endothelioma in dockyard workers, compared with three pleural mesotheliomas in other Plymouth males
  • Thoracic cancers in dockyard workers: 388 observed against 347.4 expected, PRR 111.7 (p less than 0.02). The significance was confined to pleural tumours. Lung cancer was 363 observed against 338.0 expected, PRR 107.4, not significant.
  • Gastrointestinal cancers in dockyard workers: stomach 179 observed against 157.1 expected (PRR 113.9), pancreas 46 against 42.2 (PRR 109.0), whole gastrointestinal tract 416 against 408.5 (PRR 101.8). None was statistically significant.
  • No registrations for peritoneal mesothelioma were recorded
  • Among men with pleural tumours where this was known, the mean interval from first asbestos exposure to registration was 37.6 years (range 23-69; 19 men). Mean exposure duration was 28.7 years (range 12-47; 18 men).
  • None of the dockyard men with pleural tumours was an asbestos lagger or sprayer; their occupations varied
  • Year-by-year figures, based on relatively small numbers, suggested increasing excesses of stomach and gastrointestinal registrations and a decreasing trend for lung cancer among dockyard workers
  • Registrations made from death certificates only: 273 for Plymouth males, 72 of them for dockyard workers against 75.2 expected, showing no evidence of a difference between the groups
  • The author stated that the long interval from first exposure indicates pleural mesothelioma cases may be expected among these dockyard workers for many years
• The authors' conclusion: The author concluded that the study confirms a significant excess of pleural tumours but shows no evidence of a significant excess of cancers at any other site for the dockyard workers as a whole
• Limitations the authors state:
  • The dockyard group could not be divided according to asbestos exposure, and the author considered cancer risk likely to be greater in the more heavily exposed
  • Cancer registration may be incomplete
  • Peritoneal mesothelioma was probably missed, because of lack of awareness in the early 1960s and the need for necropsy to confirm it. The author considered that such cases may have been recorded as other gastrointestinal cancers.
  • Under the proportional method, an excess at one site must be offset by deficits elsewhere, so deficits were not tested for significance
  • The year-by-year trend analysis rested on small numbers

Topics

The National Library of Medicine indexes this study under subjects our site covers: Shipyards and maritime work.

Medical terms in this study, explained in our Lexicon: Asbestos Exposure, Pleural Mesothelioma, Crocidolite, Peritoneal Mesothelioma.

Related studies

• Experience with asbestos disease and its control in Great Britain's naval dockyards — P.G. Harries (1976)
• Cancer risks among iron and steel workers in Anshan, China, Part I: Proportional mortality ratio analysis — Z. Xu, G.W. Pan, et al. (1996)
• Asbestos disease in sheet metal workers: proportional mortality update — D. Michaels, S. Zoloth (1988)
• Cancer in electrical workers: an analysis of cancer registrations in England, 1981-87 — N.T. Fear, E. Roman, et al. (1996)
• Mortality among shipyard workers in Genoa, Italy — R. Puntoni, M. Vercelli, et al. (1979)
• Mortality among workers exposed to asbestos at the shipyard of Genoa, Italy: a 55 years follow-up — D.F. Merlo, M. Bruzzone, et al. (2018)

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