Apportionment of risk among environmental exposures: application to asbestos exposure and cigarette smoking

Our plain-English summary of Apportionment of risk among environmental exposures: application to asbestos exposure and cigarette smoking, by R.C. Grimson (Journal of Occupational Medicine., 1987).

The study

• Author: R.C. Grimson
• Journal: Journal of Occupational Medicine.
• Published: 1987;29(3):253-5
• Cited by: 8 articles, as counted by NIH iCite
• Read it: PubMed
• In J-M's library: Johns-Manville's company medical library held a copy (J-M no. 000317).

Abstract

A new method for assessing the attribution of risk for each of two exposures is developed. In one instance it generalizes a method now used to evaluate compensation for smokers who have been exposed to asbestos and it extends the notion of attributable risk. This method of apportioning risk is applicable in occupational settings where risk assessment and/or compensation is required and an application is presented.

In plain English

This article was a methods paper, not a study of people. The author developed a mathematical way to divide the lung cancer risk of a person exposed to both asbestos and cigarette smoking among asbestos, smoking, and other causes. It was meant for risk assessment or compensation settings. The method built on attributable risk and assumed the two exposures multiply each other's relative risk. The share given to other (background) causes was one divided by the combined relative risk. The interaction part of the risk was split using weights. When the weights followed each exposure's excess relative risk, the formulas reduced to a method already in use, published earlier by Chase and colleagues. As in that earlier work, the author used a separate relative risk for smoking before the end of 1966. In this application, the interaction risk from smoking before 1967 was given in full to asbestos; the author noted that actual risk assessment would split it too. A table compared equal weights with excess-risk weights. The author concluded that the general formulas expressed the apportionment more clearly.

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 (mathematical) paper developing a method for apportioning risk between two exposures, with a worked application; no study population
• Who was studied: No people were studied. The paper presents formulas and a table of example relative-risk values, framed around lung cancer patients employed in the asbestos industry.
• Exposure: Asbestos exposure and cigarette smoking, each expressed as a relative risk of lung cancer, assumed to interact multiplicatively. No fiber types are specified.
• Main results:
  • The fraction of lung cancer risk attributed to other (background) causes was 1 divided by the combined relative risk (as).
  • The previously used apportionment formulas (Chase et al.) were shown to be special cases of the author's more general weighted formulas.
  • For the application, a separate relative risk (sq) was introduced for smoking before the end of 1966, the time of the Surgeon General's warning.
  • In this application, the interaction term involving smoking before 1967 was not split, so that the full risk from that smoking was given to asbestos, following the earlier article. The author noted that in actual risk assessment this term would also be partitioned.
  • A table compared apportioned risks using equal weights with those using weights based on excess relative risk. The excess-relative-risk apportionments agreed with those of Chase et al.
• The authors' conclusion: The author concluded that the extended formulas, being composed of main effects and interactions, offer clarity of expression. The existing formulas are special cases of them.

Topics

Medical terms in this study, explained in our Lexicon: Environmental Exposure, Asbestos Exposure, Attribution, Attributable Risk.

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• Interaction of asbestos, age, and cigarette smoking in producing radiographic evidence of diffuse pulmonary fibrosis — K.H. Kilburn, R. Lilis, et al. (1986)
• A case-referent study of lung cancer, occupational exposures and smoking. II. Role of asbestos exposure — H. Kjuus, R. Skjaerven, et al. (1986)
• Interaction between tobacco smoking and occupational exposures in the causation of lung cancer — K. Steenland, M. Thun (1986)
• Asbestos exposure, cigarette smoking and death rates — E.C. Hammond, I.J. Selikoff, et al. (1979)

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