Symposium on Lung Disease

Our plain-English summary of Symposium on Lung Disease, by C.E. Rossiter, H. Weill (1974).

The study

• Authors: C.E. Rossiter, H. Weill
• Published: 7th International Scientific Meeting, August 17-21 1974. Brighton.
• Type of article: Conference paper
• Our copy: from Johns-Manville's own medical library. The article is still under copyright, so we describe it here rather than post it.

In plain English

This symposium paper asked whether asbestos dust harms smokers' lung function more than non-smokers'. Lung function was tested in 819 current and 40 retired employees of two New Orleans asbestos cement plants. Each man's total dust exposure was estimated from his work history. Results were standardized for age and height using 244 workers with minimal dust exposure, no radiographic changes and no major respiratory symptoms. At first, the smoker versus non-smoker gap in forced expiratory flow rate gradually grew with exposure, except in the highest exposure group, suggesting synergism. But among low-exposed workers, smokers' flow rate fell with age about 10 times as fast as non-smokers'. Using one age equation for everyone could create the pattern by itself. After correction, the authors found this interaction entirely accounted for the apparent synergism in flow rate, and the same conclusion held for every lung function index. Non-smokers showed a slightly greater response to exposure, but this was not statistically significant. The authors noted the subgroup was only 244 men and urged great care before treating synergism as proven.

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: Cross-sectional analysis of lung function in relation to estimated dust exposure and smoking habits (symposium paper)
• Who was studied: 819 current and 40 retired employees of two New Orleans plants manufacturing asbestos cement products, tested at Tulane University. A sub-group of 244 workers with minimal dust exposure, no radiographic changes and no major respiratory symptoms (142 current smokers, 45 ex-smokers, 57 non-smokers) was used for standardization.
• Exposure: Asbestos dust in asbestos cement manufacturing. Total dust exposure was estimated from occupational histories in millions of particles per cubic foot-years (mppcf-years) and grouped into 5 exposure groups. Smoking habits were grouped as smokers, ex-smokers and non-smokers. Fiber type was not specified.
• Main results:
  • Initial observation: standardized forced expiratory flow rate declined with exposure in smokers. In ex-smokers it declined from 100% to 82%, mainly in the more heavily exposed. In non-smokers it was usually above 100%.
  • The difference between smokers and non-smokers gradually increased with exposure, except for the highest exposure group. The initial conclusion was that synergism existed.
  • In the 244 low-exposed workers, the yearly decline in forced expiratory flow rate with age for smokers was about 10 times that for non-smokers, with ex-smokers intermediate.
  • Example: smokers in the lowest exposure group (average age 34.6 years, height 176 cm) had an average forced expiratory flow rate of 4.06 litres, 93.8% of the expected 4.33 litres. Compared with the 4.23 litres expected for unexposed smokers, the standardized value was 96.0%.
  • For forced expiratory flow rate, the age-smoking habits interaction entirely accounted for the apparent synergism between smoking and dust exposure.
  • After correction, non-smokers showed a slightly greater response to exposure than smokers, but the difference was not statistically significant.
  • For each lung function index in the New Orleans study, any apparent synergism was explicable by an age-smoking habits interaction.
• The authors' conclusion: The authors concluded that the apparent synergism between smoking and asbestos cement dust exposure on lung function can arise from the method of calculating predicted values. They said great care must be taken before such synergism is considered proven.
• Limitations the authors state:
  • The sub-group used to estimate the age-smoking interactions was only 244 men, so the interactions might not be real. The authors note that other studies show similar interactions.

Topics

Medical terms in this study, explained in our Lexicon: Asbestos-Cement, Occupational History.

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