Latent Periods In Lung Cancer Mortality In Relation To Asbestos Dose And Smoking

Our plain-English summary of Latent Periods In Lung Cancer Mortality In Relation To Asbestos Dose And Smoking, by F.D.K. Liddell (1980).

The study

• Author: F.D.K. Liddell
• Published: Biological Effects Of Mineral Fibres (J.C. Wagner, Editor), Lyon: Iarc Scientific Publications, Volume 30, Pp. 661-665 (1980)
• Type of article: Conference paper
• Our copy: from Johns-Manville's own medical library, J-M no. 002179. The article is still under copyright, so we describe it here rather than post it.

In plain English

This short preliminary report examined whether the time from first asbestos exposure to lung cancer death depends on dose. The author drew on 244 lung cancer deaths among 4,463 deaths in a cohort of 10,949 men, born 1891 through 1920, who had worked at least a month in the Quebec chrysotile mines and mills. The 'interval' from first employment to death averaged 39.6 years (standard deviation 10.9) and ranged from 6 to 61 years. The men were grouped by accumulated fibre exposure (counted up to 9 years before death) and by smoking habit. No consistent pattern in average interval was found for either factor. In regression analyses, age at first employment was the variable most closely linked to the interval. Fibre 'concentration' contributed only weakly, and the author described this as of no practical importance. The author concluded that among these 244 cases there was no evidence that the latent period depends on dose. The author also noted there is no guarantee this applies to people exposed in other circumstances.

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: Preliminary report analysing lung cancer deaths from an existing cohort mortality study, using cross-classification with analysis of variance and regression analysis of the interval from first employment to death
• Who was studied: 244 male lung cancer deaths among 4,463 deaths in a cohort of 10,949 men born 1891 through 1920 who had worked at least a month in the Quebec chrysotile mines and mills
• Exposure: Chrysotile in Quebec mines and mills. Fibre exposure was measured in fibres per ml-years, accumulated up to 9 years before death (mean 1200, s.d. 2128 among the 244 cases). The analysis also used fibre 'concentration' (that exposure divided by net service) and a smoking habit code.
• Main results:
  • Among the 244 lung cancer deaths, the interval between first employment and death averaged 39.6 years (s.d. 10.9).
  • When the men were cross-classified by fibre exposure and smoking habit, no consistent pattern in average interval was found for either factor.
  • In the three regression analyses (all cases, then excluding intervals under 20 years, then excluding intervals under 30 years), age at first employment had the highest correlation with the interval (r = -.62, -.52 and -.38).
  • Fibre 'concentration' was the only other variable contributing to the regressions, with partial correlations of -.12, -.16 and -.19 (244, 228 and 202 cases). The author attributed any significance to the large numbers and judged it of no practical importance.
  • The shortest intervals were 6 and 7 years.
  • The longest interval was 61 years. Deaths fell into interval classes of up to 20 years (16 men), 20-29 years (26), 30-39 years (69), 40-49 years (91) and 50 years and more (42).
  • The five interval classes were closely similar in length of service, exposure and smoking habits. In each class about 20% had been employed less than a year and about 60% had at least 10 years of service. Tests of similarity gave chi-square statistics between 1.63 and 5.61.
  • Nearly half of the 244 men (105, or 43%) had been at work within nine years of death. Among those with intervals under 20 years, the proportion was 13 of 16 men.
• The authors' conclusion: The authors concluded that among these 244 cases there was no evidence to support the hypothesis that the latent period of asbestos-induced lung cancer depends on the dose.
• Limitations the authors state:
  • There is no guarantee the findings apply to people exposed to asbestos in other circumstances.
  • The author acknowledged the problems of interpretation pointed out by Enterline (1978).
  • Exposure accumulated in the last nine years before death was not counted for the 105 men still working then. The author judged this unlikely to have affected the cancer.
  • Smoking histories were not available for the two deaths before 1950.

Topics

Medical terms in this study, explained in our Lexicon: Lung Cancer, Asbestos Exposure, Quebec Chrysotile, Habit.

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