A study of the mortality of female asbestos workers

Our plain-English summary of A study of the mortality of female asbestos workers, by M.L. Newhouse, G. Berry, J.C. Wagner, et al (British Journal of Industrial Medicine, 1972).

The study

• Authors: M.L. Newhouse, G. Berry, J.C. Wagner, M.E. Turok
• Journal: British Journal of Industrial Medicine
• Published: 1972;29(2):134-41
• Cited by: 100 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. 001342).

Abstract

Newhouse, M. L., Berry, G., Wagner, J. C., and Turok, M. E. (1972).Brit. J. industr. Med.,29, 134-141. A study of the mortality of female asbestos workers. A cohort study of over 900 women employed at an asbestos factory making both textiles and insulation materials is described. It extends the information about asbestos-related disease at this factory which was previously available only for male workers. The cohort was defined as all the women who started employment at the factory between 1936 and 1942 and the main analysis was of mortality up to the end of 1968. This analysis was made in relation to job, length of exposure, and age at first exposure. Compared with national rates there was excess overall mortality among those who worked in jobs with low to moderate exposure partly accounted for by deaths from cancer. In the group with severe exposure, who had worked in the factory for less than two years, there was an excess of cancer of the lung and pleura. However, the most marked increased mortality was in those with severe exposure who had worked for more than two years in the factory; in this group there were excess deaths from cancer of the lung and pleura, from other cancers, and from respiratory diseases. There were no significant trends of excess mortality with age at first exposure. The smoking habits of some of the deceased women were obtained and the indications were that the proportion of smokers in the cohort was higher than the national rate. This could account for some of the excess mortality but the trend of this excess with exposure indicated the role of asbestos. Necropsy reports and/or histological material were obtained for 43% of those who had died. Three deaths registered as cancer of the pleura were identified as pleural mesothelial tumours; in all there were 11 mesotheliomas, six of pleural and five of peritoneal origin.

In plain English

This cohort study followed women who started work between 1936 and 1942 at one asbestos factory that used chrysotile, crocidolite and amosite. Their deaths to the end of 1968 were compared with national rates for England and Wales. Of 928 women, 716 (77%) were traced and 140 had died. Six untraced women were then excluded, leaving 922. Of 126 women with low to moderate exposure, 29 died where 18.1 deaths were expected. Among 239 severely exposed women employed over two years, 56 died where 24.5 were expected. These included 14 deaths from lung and pleura cancer (0.5 expected) and 17 from other cancers (6.1 expected). Severely exposed women employed under two years had 6 lung and pleura cancer deaths (1.0 expected). Eleven mesotheliomas were found, six pleural and five peritoneal. No excess deaths appeared within 10 years of first exposure. Smoking habits were known for 93 women who died in 1960-70. Of these, 65% had smoked, against 42% expected from national rates for women. The authors noted that smokers would be over-represented among deaths anyway. They thought the cohort probably smoked more than women nationally. Even so, they concluded that asbestos was responsible for an appreciable proportion of the excess lung cancers.

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 mortality study comparing observed deaths with deaths expected from national (England and Wales) rates
• Who was studied: 928 women who started work at one asbestos factory between 1 January 1936 and 31 December 1942. Of these, 716 (77% of 928) were traced, 576 alive and 140 dead at 31 December 1968. Six untraced women with unknown dates of birth were excluded, leaving 922 in the analysis cohort. Follow-up ran to the end of 1968.
• Exposure: Work at an asbestos factory. 126 women had low to moderate exposure: office, canteen, laboratory and print stores, plus some brake lining and rubber jointing work. The rest were considered severely exposed. Their jobs were textile carding, spinning, doubling and weaving, mattress making, sectional pipe making, gas mask filters and the yarn store. Crocidolite was used in spinning and doubling. Chrysotile and amosite were used in carding, weaving and mattress making. Crocidolite alone, or crocidolite with amosite, was used in the other severe-exposure jobs. Results were analysed by job, length of employment (under or over two years) and age at first exposure.
• Main results:
  • Low to moderate exposure group (126 women): 29 deaths from all causes observed versus 18.1 expected (p less than 0.05). These included 2 deaths from cancer of the lung and pleura versus 0.3 expected, and 8 from other cancers versus 4.4 expected.
  • Severe exposure, less than two years' employment (557 women): 6 deaths from cancer of the lung and pleura versus 1.0 expected, described as a highly significant excess. All causes: 55 observed versus 49.9 expected.
  • Severe exposure, more than two years' employment (239 women): all causes 56 observed versus 24.5 expected. Cancer of the lung and pleura: 14 versus 0.5. Other cancers: 17 versus 6.1. Respiratory disease excluding cancer: 11 versus 3.6. Three of the 11 respiratory deaths were certified as asbestosis.
  • Excess annual lung cancer death rates were 63 per 100 000 years' exposure in the low to moderate group, 44 in the severe short-exposure group, and 241 in the group with severe exposure for two years or longer. The third group's excess rate was significantly higher (p less than 0.001).
  • Eleven mesotheliomas were identified, six pleural and five peritoneal. Six occurred in women who had worked less than two years at the factory, one of whom had worked there only six weeks.
  • Three of the 22 deaths certified as cancer of the lung or pleura were reclassified as pleural mesothelioma, and the diagnosis was confirmed in a further three.
  • Among women with severe and long exposure, three deaths were registered as ovarian cancer, against 0.6 expected. The authors called this a significant finding but said the numbers were too small for definite conclusions.
  • No excess mortality was seen within 10 years of first exposure. Excess lung cancer began to show at 10 to 20 years and was much more marked after 20 years.
  • In absolute terms there were no significant differences in excess mortality between age-at-first-exposure groups. Excess annual lung cancer rates were 108, 76 and 122 per 100 000 years at risk for ages 15-24, 25-34 and 35 or over.
  • Smoking histories were found for 93 of the 103 women who died between 1960 and 1970. Of these, 60 (65%) were reported to have been smokers, against 39 (42%) expected from age-adjusted 1956 United Kingdom smoking prevalence for women. The authors noted that smokers would be expected to be over-represented among deaths, and that the data needed to test whether 65% exceeded what this would produce were sparse for women. They judged it probable that the cohort had a higher proportion of smokers than the national female population.
  • Lung tissue was examined in 23 women who died; evidence of asbestosis was found in all but two.
• The authors' conclusion: The authors concluded that the much higher excess lung cancer risk with severe exposure, together with the pleural mesotheliomas, showed that asbestos exposure was responsible for an appreciable proportion of the excess lung cancers. They also concluded that, within the severe exposure group, asbestos exposure resulted in excess deaths from other cancers and respiratory diseases. They suggested that asbestos has a similar absolute lung cancer effect in men and women.
• Limitations the authors state:
  • Only 77% of the cohort was traced, which could bias results if untraced women's mortality differed.
  • Smoking information was incomplete and obtained second hand, and the cohort probably had more smokers than the national female population.
  • Death rates for 1961-65 were used to calculate expected deaths for 1966-68.
  • National rates were used, although rates from a smaller, geographically similar area such as Greater London might have been more appropriate.
  • The age-at-first-exposure analysis made no allowance for length of follow-up.
  • The ovarian cancer numbers were too small for definite conclusions.

Topics

The National Library of Medicine indexes this study under subjects our site covers: Asbestos textiles.

Medical terms in this study, explained in our Lexicon: Cohort Study, Pleura, Habit, Autopsy, Mesothelioma.

Related studies

• Mortality in the chrysotile asbestos mines and mills of Quebec — J.C. McDonald, A.D. McDonald, et al. (1971)
• Follow-up study of chrysotile asbestos textile workers: cohort mortality and case-control analyses — J.M. Dement, D.P. Brown, et al. (1994)
• Technological feasibility of the 2 fibers/cc asbestos standard in asbestos textile facilities — R.A. Curtis, P.H. Bierbaum (1975)
• Mortality and cancer morbidity in a cohort of Canadian petroleum workers — R.J. Lewis, A.R. Schnatter, et al. (2003)
• An updated mortality study of workers at a petroleum refinery in Beaumont, Texas — G.K. Raabe, K.W. Collingwood, et al. (1998)
• Mortality rates among nuclear industry workers at Lucas Heights Science and Technology Centre — R.R. Habib, S.M. Abdallah, et al. (2005)

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