A study of dose-response relationships for asbestos associated disease

Our plain-English summary of A study of dose-response relationships for asbestos associated disease, by M.M. Finkelstein (British Journal of Industrial Medicine, 1985).

The study

• Author: M.M. Finkelstein
• Journal: British Journal of Industrial Medicine
• Published: 1985;42(5):319-25
• Cited by: 25 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. 000473).

Abstract

The risk of an asbestos worker developing small irregular opacities on the chest radiograph is related to cumulative exposure to asbestos dust, latency, and smoking habit. In this study the use of residence-time weighted exposure as a "dose metric" was explored in a cohort of asbestos cement workers. It was found that this parameter, which incorporates both exposure concentration and latency, is useful for modelling the risk of small opacities and might also be useful for modelling the risk of mesothelioma.

In plain English

This study examined 181 men hired before 1960 at an asbestos cement factory who had worked there at least nine years. The author tested a "dose" measure weighting each year's asbestos dust exposure by the time since it occurred; its simplest form assumes no clearance from the lungs, so it keeps rising after exposure ends. The article does not state the asbestos fiber type used at this factory. In a Cox regression of 147 men with normal chest X-rays 18 years after first exposure, cumulative exposure, smoking and age each contributed to the risk of small irregular opacities. Estimated relative risks for smokers were 1.8, 2.5 and 4.1 for increasingly advanced opacity categories. From 20 to 34 years after first exposure, the dose measure predicted average small-opacity X-ray scores without depending on time since first exposure. Bilateral pleural thickening showed no association with dose. For the 12 mesothelioma deaths, linear and quadratic curves fit equally well. The author concluded that the dose measure was useful for small opacities and might be useful for mesothelioma, though the cohort was too small for a definitive statement.

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: Cohort study of asbestos cement workers testing a residence-time weighted dose measure against chest X-ray abnormalities and mesothelioma deaths
• Who was studied: Men hired at an asbestos cement factory before 1960 with at least nine years' employment and at least one year of asbestos exposure before 1961. All 181 were in the mortality analysis. The 161 with a chest film 15 or more years after first exposure were in the X-ray analysis.
• Exposure: Asbestos dust in an asbestos cement factory (the fiber type used at this factory is not stated). Cumulative exposure was summed over the first 18 years. Dose assumed a fixed share of airborne dust was deposited in the lungs, with each year's amount weighted by its residence time in the lungs. In the main measure no clearance was assumed. Units are f/ml x years squared. Measures with clearance half-times of two and five years were also tested.
• Main results:
  • In a Cox regression of the 147 men with normal films at 18 years after first exposure, cumulative exposure was a significant contributor to the risk of small opacities, as were smoking and age.
  • Point estimates of relative risk for smokers were 1.8 for small opacities of category 1/0 or more, 2.5 for 1/1 or more, and 4.1 for 1/2 or more.
  • The smoking-exposure interaction term was not significant for any category of small opacities.
  • The mean X-ray score for small opacities rose one category with a 50 pack-year smoking history (95% confidence limits 30-70 pack-years). It also rose one category with an asbestos dose of about 2000 f/ml x years squared.
  • These models accounted for only about one third of the variability in X-ray scores.
  • Over the interval 20-34 years after first exposure, the dose measure predicted mean X-ray scores for small opacities without depending on time since first exposure.
  • There was no association between bilateral pleural thickening and the dose measure in this cohort.
  • Dose measures with clearance fit about as well, so the simplest, no-clearance measure was judged most useful.
  • There were 12 deaths from mesothelioma in the cohort.
  • For mesothelioma, linear and quadratic functions of dose fit cumulative risk equally well.
• The authors' conclusion: The author concluded that the no-clearance dose measure could predict both the cumulative risk of small irregular opacities and the average X-ray score in this group. It might also be useful for mesothelioma, though the cohort was too small for a definitive statement.
• Limitations the authors state:
  • The dose estimates have a large margin of uncertainty, more than the cumulative exposure estimates.
  • Whether the results hold beyond 35 years after first exposure was not assessed.
  • The mesothelioma finding rests on a small population and needs verification in other cohorts.
  • There were too few abnormal films before 20 years after first exposure for the regression model to be valid in that period.
  • The dose measures are mathematical models of risk, not descriptions of how the body actually clears fibers. The author notes that clearance is known to occur.
  • Much of the variability in response was unexplained, so predictions can be made only for groups, not individuals.

Topics

Medical terms in this study, explained in our Lexicon: Dose-response relationship, Chest X-Ray, Cumulative Exposure, Latency, Habit, Dose Metric, Asbestos-Cement, Mesothelioma.

Related studies

• Asbestos exposure and benign asbestos diseases in 772 formerly exposed workers: dose-response relationships — G. Mastrangelo, M.N. Ballarin, et al. (2009)
• Pulmonary function in asbestos cement workers: a dose-response study — M. Finkelstein (1986)
• Mortality experience of amosite asbestos factory workers: dose-response relationships 5 to 40 years after onset of short-term work exposure — H. Seidman, I.J. Selikoff, et al. (1986)
• Fiber burden and asbestos-related lung disease: determinants of dose-response relationships — M.R. Becklake, B.W. Case (1994)
• NHLBI workshop summary. Environmental lung diseases. Relationship between acute inflammatory responses to air pollutants and chronic lung disease — J. Crapo, F.J. Miller, et al. (1992)
• Dose-response relationships for asbestos-related disease: implications for hygiene standards. Part II. Mortality — J. Peto (1979)

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