Cohort analysis of changes in incidence of bronchial carcinoma in a textile asbestos factory

Our plain-English summary of Cohort analysis of changes in incidence of bronchial carcinoma in a textile asbestos factory, by J.F. Knox, R.S. Doll, I.D. Hill (Annals of the New York Academy of Sciences, 1965).

The study

• Authors: J.F. Knox, R.S. Doll, I.D. Hill
• Journal: Annals of the New York Academy of Sciences
• Published: 1965;132(1):526-35
• Cited by: 29 articles, as counted by NIH iCite
• Read it: PubMed · Publisher
• In J-M's library: Johns-Manville's company medical library held a copy (J-M no. 001531).

Summary of the article

The authors examined whether the lung cancer risk among workers in a large British asbestos textile factory, where chrysotile was predominantly used, had changed since dust-control regulations made in 1931 took effect at the start of 1933. They extended an earlier study (Doll, 1955) to the end of 1961. From personnel records they identified 198 men who had completed at least 20 years in the regulated 'scheduled areas'. These men were divided into four groups by their length of experience before 1933. A further group of 427 men and 175 women was first employed on or after 1 January 1933 and completed at least 10 years. Observed deaths were compared with numbers expected from England and Wales rates. Among men with over 10 years' experience before 1933 (57 men), there were 15 deaths from lung and pleural cancer against 0.94 expected. There were 41 deaths from all causes against 15.00 expected. Men with 5-10 years' pre-1933 experience had 5 lung cancer deaths against 0.81 expected. The remaining male groups showed no excess. Women had 8 deaths against 4.02 expected (P=0.052), including one lung cancer. The risk rose with age and fell with shorter exposure before 1933. The authors concluded that the risks were much reduced, mainly because of the improved working conditions. They stated that complete elimination of the hazard could not yet be asserted.

PubMed has no abstract for this study, and the article doesn't print one. We wrote this summary from the full article with the help of AI. It is not the authors' wording.

In plain English

This cohort study followed deaths among workers at a large English asbestos textile factory that used mainly chrysotile; some crocidolite exposure could not be ruled out. It extended an earlier study by Doll (1955) to the end of 1961. Workers were grouped by time in 'scheduled areas', taking 1 January 1933 as the start of improved dust control under the 1931 regulations. Deaths were compared with numbers expected from England and Wales rates. Among 57 men who completed at least 20 years in scheduled areas, over 10 before 1933, 15 died of cancer of lung and pleura against 0.94 expected. Among 45 such men with 5 to 10 years before 1933, 5 died against 0.81 expected. Groups with less or no pre-1933 exposure, including 427 men who started in 1933 or later and worked at least 10 years, showed no evidence of excess risk, though follow-up was relatively short. Among 175 such women, 8 died against 4.02 expected (P=0.052), one from lung cancer. The authors concluded the risks were now much reduced but could not confidently say they had been eliminated.

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 (observed versus expected deaths using England and Wales rates), extending an earlier study of the same factory
• Who was studied: Workers at one large asbestos textile factory in England. The 20-year study had 198 men who worked at least 20 years in 'scheduled areas', divided into four groups by experience before 1 January 1933: Group 1, over 10 years, 57 men; Group 2, 5 to 10 years, 45 men; Group 3, up to 5 years, 16 men; Group 4, none, 80 men. The 10-year study had people first employed on or after 1 January 1933 with at least 10 years in scheduled areas: 427 men and 175 women. Follow-up ran to the end of 1961.
• Exposure: Work in the 'scheduled areas' of an asbestos textile factory where chrysotile was predominantly used. Some exposure to crocidolite could not be ruled out, but no worker had used it for a considerable part of their working life. Exposure was compared before and after 1 January 1933, when dust-control regulations made in 1931 were taken to be in force.
• Main results:
  • Group 1 (57 men with at least 20 years in scheduled areas, over 10 of them before 1933): 15 observed deaths from cancer of lung and pleura versus 0.94 expected (P<0.000001). There were 41 deaths from all causes versus 15.00 expected. The authors saw no evidence of other cancer risk, and attributed the extra all-cause deaths to excess respiratory and cardiovascular disease.
  • Group 2 (45 men with at least 20 years in scheduled areas, 5 to 10 of them before 1933): 5 observed deaths from cancer of lung and pleura versus 0.81 expected (P=0.0015). The authors described the lung cancer risk as present but considerably reduced.
  • The authors found no evidence of any excess risk in Groups 3, 4 and 5, but stressed that their follow-up was relatively short. Deaths from cancer of lung and pleura were 0 observed versus 0.20 expected in Group 3 (16 men), 0 versus 0.30 in Group 4 (80 men), and 3 versus 4.00 in Group 5 (427 men who entered in 1933 or later).
  • One man in Group 4 died of bronchial carcinoma with evidence of asbestosis two years after the study ended.
  • Group 6 (175 women who entered in 1933 or later): 8 deaths from all causes versus 4.02 expected (P=0.052), described by the authors as very nearly statistically significant. One of these deaths was from lung cancer, against 0.09 expected. Only three of the eight deaths appeared at all likely to be linked to occupation.
  • Across both sexes in the 10-year groups, there were 43 deaths against 43.63 expected.
  • In an analysis of the 20 lung cancer deaths among the 20-year men, risk increased with age and decreased with shorter exposure before 1933. There was no evidence of a change with experience beyond the initial 20 years.
• The authors' conclusion: The authors concluded that exposure to asbestos dust before 1933 in this factory carried a greatly increased risk of lung cancer and an increased risk of death from other respiratory and cardiovascular diseases. They found good evidence that these risks were now much reduced, attributing this mainly to improved working conditions under the 1931 regulations. They stated it was not possible to say with confidence that the hazards had been completely eliminated, and that further observation was needed.
• Limitations the authors state:
  • Follow-up of the groups first exposed after 1933 was relatively short and could not show what would happen to them in later decades.
  • The trend analysis was hard to interpret because all 20 lung cancer deaths were in men employed both before and after 1933, so a year of exposure did not mean the same thing across the period.

Topics

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

Medical terms in this study, explained in our Lexicon: Carcinoma, Lung Cancer, Chrysotile.

Related studies

• Practical steps towards the prevention of bronchial carcinoma — R. Doll (1970)
• Incidence of bronchial carcinoma in shipyard workers with pleural plaques — J.R. Edge (1979)
• Unsuspected exposure to asbestos and bronchogenic carcinoma — K.M. Martischnig, D.J. Newell, et al. (1977)
• The relationship between asbestosis and bronchial cancer — G.K. Sluis-Cremer (1980)
• Smoking status, occupational asbestos exposure and bronchial location of lung cancer — C. Paris, J. Benichou, et al. (2003)
• Smoking, occupational risk factors, and bronchial tumor location: a possible impact for lung cancer computed tomography scan screening — M. Gonzalez, J.M. Vignaud, et al. (2012)

Browse more research in Annals of the New York Academy of Sciences, or return to medical research.