Dose-response relationships for asbestos-related disease: implications for hygiene standards. Part II. Mortality

Our plain-English summary of Dose-response relationships for asbestos-related disease: implications for hygiene standards. Part II. Mortality, by J. Peto (Annals of the New York Academy of Sciences, 1979).

The study

• Author: J. Peto
• Journal: Annals of the New York Academy of Sciences
• Published: 1979;330:195-203
• Cited by: 20 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. 004027).

Summary of the article

This conference paper argued that, for the purpose of setting hygiene standards, excess cancer risk from asbestos should be assumed to be linearly related to dust level until this is disproved. The author presented this as a pragmatic proposal rather than a scientific statement. He reasoned that threshold models can underestimate low-dose risk by an order of magnitude, and that a standard is not an absolute maximum, because individual exposures vary around the average. Using hypothetical worked examples, he showed how risks observed in exposed cohorts could be scaled to lower dust levels. For bronchial carcinoma, relative risk was assumed to remain constant after exposure. A 10% rise in relative risk would then mean about nine asbestos-induced deaths per 1000 men, given that 9% of male deaths in England and Wales were due to lung cancer. For mesothelioma, incidence data from North American insulation workers fitted three different time models similarly up to 45 years after first exposure. In the example, lifelong risk was about 8% for mesothelioma and 9% for bronchial carcinoma at an average of 20 fibers/cm3, implying about 1.7% at 2 fibers/cm3. The paper also described a method for converting risks between fiber types. Modelled effects of age at first exposure and duration were shown, with gastrointestinal cancer and asbestosis set aside. The author concluded that occupational exposure must be rigorously monitored, but that risk to the general population is likely to be extremely low.

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 methods and policy paper reported no new worker study. For hygiene standards, the author proposed assuming that excess cancer risk (above unexposed men's risk) rises in proportion to dust level until disproved: a pragmatic proposal, not a scientific statement. Hypothetically, if lung (bronchial) cancer were doubled 30 years after first exposure in men exposed 10 to 30 years, a tenth of the dust would raise it about 10% then. Assuming this persisted into retirement, with national-average smoking, the author projected about nine asbestos-induced lung cancer deaths per 1000 such men. For hypothetical men exposed 10 to 30 years, first exposed at ages spread evenly from 20 to 45, with a set mesothelioma rate at 30 years and 1975 England and Wales death rates, a 90% dust cut would mean about eight in 1000 eventually developing mesothelioma. Three models fitted published North American insulation workers' mesothelioma data about equally well. Predictions suggested age at first exposure strongly affected the mesothelioma-to-lung-cancer balance. The author warned some predictions could be considerably in error. The author concluded that occupational exposure needs rigorous monitoring but general-population risk is likely extremely low.

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: Methodological and policy discussion paper using statistical models applied mainly to hypothetical data, plus published mesothelioma data from another study; not an original epidemiologic study
• Who was studied: No new study population. Examples were hypothetical asbestos factory workers. Table 1 used previously published mesothelioma incidence data (credited to Nicholson) on North American insulation workers.
• Exposure: Airborne asbestos dust levels, measured in fibers per cubic centimetre, in hypothetical factory exposures (for example, comparisons at 20 and 2 fibers per cubic centimetre). Differences between fiber types (chrysotile versus amphibole) were discussed in general terms.
• Main results:
  • The author's working assumption was that excess cancer mortality (the increase above the rate in unexposed men of the same age) is linearly related to dust level.
  • Illustrative prediction under the linear assumption: if bronchial carcinoma were doubled 30 years after first exposure in a group of factory workers exposed for 10 to 30 years, a similar variety of exposures at a tenth of those levels would increase bronchial carcinoma incidence by about 10% at 30 years after first exposure, for men exposed for 10 to 30 years.
  • Assuming the raised relative risk persists in retirement, and using the fact that 9% of male deaths in England and Wales were from lung cancer, the author calculated that this 10% increase would correspond to roughly nine asbestos-induced lung cancer deaths per 1000 exposed men over their lifetime. The author justified this by English factory workers' smoking habits being similar to the national average.
  • In the hypothetical cohort (10 to 30 years of exposure, a given mesothelioma incidence 30 years after first exposure), the lifelong mesothelioma risk would be approximately 8%. This assumed that ages at first exposure were spread evenly between 20 and 45 and that death rates from other causes were those of men in England and Wales in 1975.
  • For that same hypothetical cohort, a 90% reduction in dust levels would, if the dose-response relationship is linear, mean about eight men in 1000 of similar age and duration of exposure eventually developing mesothelioma.
  • Three different models fitted to the North American insulation workers' mesothelioma data gave similar predictions. The author explained that all of them assume the future pattern of mesothelioma incidence over time will resemble the past.
  • In a hypothetical example, a combined lifelong risk of 8% for mesothelioma and 9% for bronchial carcinoma at an average of 20 fibers per cubic centimetre would fall to about 1.7% at 2 fibers per cubic centimetre under the linear assumption.
  • Hypothetical predictions (Table 2) suggested that the share of excess respiratory cancer due to mesothelioma could vary by more than 30 times within the same cohort, depending on age at first exposure and duration of exposure.
  • The author judged it probably reasonable to leave gastrointestinal cancer and asbestosis out of formal predictions for low dust levels, while noting that these diseases may still contribute some excess.
  • The author reported that a preliminary analysis of a study of the entire workforce of an English factory found only one case (in context, of mesothelioma) among more than 15,000 men exposed for less than two years since 1933.
• The authors' conclusion: The author concluded that a linear dose-response relationship should be assumed when setting hygiene standards. The author also concluded that occupational exposure must be rigorously monitored, but that the risk to the general population is likely to be extremely low.
• Limitations the authors state:
  • Available epidemiologic data could not rule out that the risk at low dust levels is considerably higher or lower than the linear model suggests.
  • The linear assumption was offered as a pragmatic proposal, not a scientific statement.
  • Accurate dust-level histories are never available for cohorts in which excess mortality is high enough to be estimated.
  • The model-based predictions for different ages and durations of exposure (Table 2) may be considerably in error.
  • A single study cannot be used as a basis for general legislation, because different fiber types and working conditions may produce widely differing effects.
  • The lung cancer calculation relied on English factory workers smoking like the national average. Adjustment would be needed for women and for countries with different or changing smoking habits.

Topics

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

Medical terms in this study, explained in our Lexicon: Dose-response relationship, Carcinoma, Relative Risk, Lung Cancer, Mesothelioma, Insulator, Occupational Exposure.

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• An air quality data analysis system for interrelating effects, standards, and needed source reductions: Part 13--Applying the EPA Proposed Guidelines for Carcinogen Risk Assessment to a set of asbestos lung cancer mortality data — R.I. Larsen (2003)

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