A proposed threshold exposure for airborne asbestos

Our plain-English summary of A proposed threshold exposure for airborne asbestos, by J.H. Lange, G. Mastrangelo, L. Cegolon (Occupational and Environmental Medicine, 2012).

The study

• Authors: J.H. Lange, G. Mastrangelo, L. Cegolon
• Journal: Occupational and Environmental Medicine
• Published: 2012;69(3):227-8
• Type of article: Letter, Comment
• Cited by: 3 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

In plain English

This was a short letter to the editor from authors at the University of Padova, Italy, responding to a published cohort study of asbestos and cancer by Clin and colleagues; it reported no new data. The authors noted that other investigators had reported a no-effect threshold of around 25 fibre/ml-years, possibly lower for some people. Citing other work, they wrote that lung cancer risk did not exceed unity for non-smokers even at high exposure, while smokers and former smokers had a significant increased risk. They added that about 60% or more of abatement workers smoke, depending on the population observed, which makes a threshold hard to estimate. Drawing on earlier studies of mixed chrysotile and amphibole exposure and a reported asbestosis value of about 23 fibre/ml-years, they proposed a threshold of 0.8 fibre/ml as a time weighted average over 25 working years, equal to 20 fibre/ml-years. They suggested chrysotile alone might warrant a higher value. The authors stated that comparing this value with Clin et al's lung cancer and mesothelioma data for 25 years or less of exposure supported it, while noting any threshold will be controversial.

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: Letter to the editor (commentary on a published study); no original data
• Who was studied: No study population of its own; the letter comments on the cohort studied by Clin et al and cites other published studies
• Exposure: Airborne asbestos, measured as cumulative exposure (fibre/ml-years); mixed fibre exposure (chrysotile and amphibole) and chrysotile alone are discussed
• Main results:
  • The authors noted that other investigators (not this letter) had reported a threshold of around 25 fibre/ml-years, possibly lower for some members of an exposed group
  • Citing another report (Frost, Health & Safety Executive), the authors wrote that lung cancer risk for non-smokers did not exceed unity even at high asbestos exposure, while smokers and former smokers had a significant increased risk
  • The authors stated that about 60% or more of asbestos abatement workers smoke, depending on the population observed
  • The authors suggested that for chrysotile alone a higher threshold value would be warranted
  • Allowing a safety margin for a lower value reported elsewhere for causing asbestosis (about 23 fibre/ml-years), the authors proposed a threshold printed as 0.8 fibre/ml-year (20 fibre/ml-years)
  • Using a 25-year working period, the authors suggested a threshold of 0.8 fibre/ml as a time weighted average
  • The authors stated that, at present exposure levels, workers in developed nations are unlikely to exceed a cumulative exposure of 20 or 25 fibre/ml-years
• The authors' conclusion: The authors concluded that comparing their proposed threshold with Clin et al's lung cancer and mesothelioma data for 25 years or less of exposure supported the proposed threshold value
• Limitations the authors state:
  • The authors acknowledged that any threshold value will be controversial
  • The authors stated that the high rate of smoking among asbestos workers makes it difficult to estimate a threshold
  • The authors noted that the 25-year working period used in their calculation is not likely for asbestos workers in the USA

Related studies

• Exposure to airborne asbestos during abatement of ceiling material, window caulking, floor tile, and roofing material — J.H. Lange, S.L. Sites, et al. (2006)
• Non-enzymatic extramicrosomal bioactivation of chemical carcinogens by phagocytes: a proposed new pathway — A.A. Roman-Franco (1982)
• Area and personal airborne exposure during abatement of asbestos-containing roofing material — J.H. Lange, K.W. Thomulka (2000)
• The role of threshold limit values in U.S. air pollution policy — J.C. Robinson, D.G. Paxman (1992)
• Airborne asbestos in buildings — R.J. Lee, D.R. Van Orden (2008)
• Occupational exposure to airborne asbestos from phenolic molding material (Bakelite) during sanding, drilling, and related activities — F. Mowat, M. Bono, et al. (2005)

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