Prevalence and features of advanced asbestosis (ILO profusion scores above 2/2). International Labour Office

Our plain-English summary of Prevalence and features of advanced asbestosis (ILO profusion scores above 2/2). International Labour Office, by K.H. Kilburn (Archives of Environmental Health, 2000).

The study

• Author: K.H. Kilburn
• Journal: Archives of Environmental Health
• Published: 2000;55(2):104-8
• Cited by: 4 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

In this study, the author addressed the following question: Do workers with advanced asbestosis have a restrictive pulmonary physiology, and, alternately, do those who have restrictive physiological tests have advanced asbestosis? One group was identified by obvious radiographic measurements, and the other group was defined via physiologic measurements. Total lung capacity, vital capacity, and flows were measured in 12,856 men exposed to asbestos, of whom 3,445 had radiographic signs of asbestosis, as defined by the International Labour Office criteria. Radiographically advanced asbestosis-International Labour Office criteria profusion greater than 2/2 was present in 85 (2.5%) of men. An additional 52 men had physiologically restrictive disease. The author, who compared pulmonary flows and volumes of these two groups, used mean percentage predicted, adjusted for height, age, and duration of cigarette smoking. Men with radiographically advanced asbestosis had normal total lung capacity (i.e., 105.5% predicted), reduced forced vital capacities (i.e., 82.7% predicted), air trapping (i.e., residual volume/total lung capacity increased to 54.4%), and reduced flows (i.e., forced expiratory flow [FEF25-75] = 60.6% predicted, forced expiratory volume in 1 s = 78.0% predicted, and forced expiratory volume in 1 s/forced vital capacity = 65.5%). In contrast, men selected from the same exposed population for restrictive disease (i.e., reduced total lung capacity [72.6% predicted] and forced vital capacity [61.5% predicted]) also had airflow obstruction (i.e., forced expiratory volume in 1 s/forced vital capacity of 74.5% predicted) and air trapping (i.e., residual volume/total lung capacity of 46.7%). Only half of these men had asbestosis--and it was of minimal severity. In summary, advanced asbestosis was characterized by airway obstruction and air trapping, both of which reduced vital capacity but not total lung capacity; therefore, it was not a restrictive disease. In contrast, restrictive disease was rare and was associated with minimal asbestosis.

In plain English

The study drew on 12,856 male construction workers from 69 US sites. All had at least 5 years of asbestos exposure, beginning at least 15 years earlier. The article does not say which asbestos fiber types these workers encountered. The author compared two non-overlapping groups. The first was 85 men whose chest X-rays showed advanced asbestosis (ILO profusion above 2/2). They were 0.66% of all men studied and 2.5% of the 3,445 with X-ray signs of asbestosis. The second was 52 men with restrictive disease: X-ray-estimated total lung capacity and breathing-test forced vital capacity both below 80% of predicted. In the advanced asbestosis group, no man had total lung capacity below 80% of predicted (mean 105.5%). Their forced vital capacity was reduced, airflow was significantly reduced, and they had air trapping. Only half of the restrictive group had asbestosis on X-ray. This group also had reduced mid-flows. The author concluded that reduced lung volume occurs rarely in severe asbestosis diagnosed by X-ray. The author noted that smoking might have offset volume loss; only 4 of the 85 had never smoked.

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 comparison of two subgroups selected from a population of asbestos-exposed workers examined by one medical team
• Who was studied: 12,856 asbestos-exposed men, a national sample of male construction workers from 69 US sites, most of them active or retired members of plumbers and pipefitters or boilermakers unions. About 3,445 (27%) had radiographic asbestosis. Of 88 men with advanced asbestosis, 3 were excluded because of lung resections, leaving 85. These were compared with 52 men with physiological restrictive disease (both TLC and FVC below 80% of predicted). Study years are not stated.
• Exposure: Occupational asbestos exposure for at least 5 years, beginning at least 15 years earlier. Fiber types encountered by the study's workers are not specified.
• Main results:
  • Radiographically advanced asbestosis (ILO profusion above 2/2) was found in 85 of 12,856 men (0.66%), which was 2.5% of the 3,445 with typical opacities
  • In the 85 men with advanced asbestosis, mean total lung capacity (calculated from chest radiographs) was 105.5% of predicted, and no man had a total lung capacity below 80% predicted
  • In the 85 men with advanced asbestosis, mean forced vital capacity was reduced to 82.6% predicted (82.7% in the table), and the residual volume to total lung capacity ratio (times 100) was elevated to a mean of 54.4
  • In the 85 men with advanced asbestosis, expiratory airflows were significantly decreased. The FEV1/FVC ratio was 65.5, against a predicted 73.7. Six men had severe airway obstruction and only 6 had no obstruction.
  • In the 85 men with advanced asbestosis, 58% had asthma or chronic bronchitis, and only 4 had never smoked cigarettes
  • In the 52 men with restrictive disease, forced vital capacity was 61.5% predicted and total lung capacity was 72.6% predicted. These volumes were significantly lower than in the advanced asbestosis group (p less than .0001).
  • Only 50% of the 52 men with restrictive disease had radiographic pulmonary asbestosis, at a low average ILO profusion of 1/0
  • The 52 men with restrictive disease also showed small-airways obstruction (reduced mid-flows)
• The authors' conclusion: The author concluded that diminished lung volume occurs rarely in severe asbestosis diagnosed radiographically, and that when it occurs its cause should be sought
• Limitations the authors state:
  • Effects of smoking on lung volume could have offset volume loss, since only 4 of the 85 men with advanced asbestosis had never smoked. The author stated that resolving this question was impractical.

Topics

The National Library of Medicine indexes this study under subjects our site covers: Asbestosis.

Medical terms in this study, explained in our Lexicon: Total Lung Capacity (TLC), Obstructive Lung Disease.

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• Relation of spirometric function to radiographic interstitial fibrosis in two large workforces exposed to asbestos: an evaluation of the ILO profusion score — A. Miller, R. Lilis, et al. (1996)
• Pleural abnormalities in the Framingham Heart Study: prevalence and CT image features — T. Araki, M. Yanagawa, et al. (2017)
• Airways obstruction from asbestos exposure. Effects of asbestosis and smoking — K.H. Kilburn, R.H. Warshaw (1994)
• Asbestosis in an asbestos composite mill at Mumbai: a prevalence study — V. Murlidhar, V. Kanhere (2005)
• Prevalence of chronic respiratory disease. Asbestosis in ship repair workers — B.G. Ferris, M.V. Panadive, et al. (1971)

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