Epidemiologic basis for the asbestos standard

Our plain-English summary of Epidemiologic basis for the asbestos standard, by P.E. Enterline (Environmental Health Perspectives, 1983).

The study

• Author: P.E. Enterline
• Journal: Environmental Health Perspectives
• Published: 1983;52:93-7
• Cited by: 1 article, 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. 002534).

Abstract

The current standard for occupational exposure to asbestos is 2 fibers/cm3 averaged over an 8-hr day. A NIOSH/OSHA committee has recently concluded that the 2 fiber/cm3 standard is grossly inadequate to protect workers from asbestos-related disease, and that all levels of asbestos exposure studied thus far have demonstrated asbestos-related disease. The committee recommends that a 0.1 fiber/cm3 limit replace the current 2 fiber/cm3 standard on the grounds that this is the lowest level detectable with currently available analytical techniques. Thus a 0.1 fiber/cm3 limit is not based on epidemiological data but on the presumption that any level of exposure is disease producing. This paper addresses the question of whether it would be possible to detect health effects of exposure below the current 2 fiber/cm3 standard. Five studies are reviewed which provide evidence on the strength of the relationship between asbestos fiber exposure and lung cancer. Calculation of sample sizes needed to be 95% certain of detecting the kind of excess probably associated with exposure to 2 fibers/cm3 suggests that epidemiology is not likely to be useful in detecting lung cancer below the current standard. Some outcome measures other than lung cancer or clinical asbestosis will be needed if observations on humans are to be used as evidence for a lowering of the present standard.

In plain English

This 1983 article reviewed the history of U.S. and British asbestos exposure limits. It asked whether epidemiology could detect lung cancer from exposure below the then-current U.S. standard of 2 fibers/cm3. The author compared dose-response estimates for lung cancer calculated from six published studies, including Quebec miners and millers, U.S. retired asbestos products workers and a British asbestos textile factory. At 100 fiber/cm3-years, the models predicted lung cancer standardized mortality ratios from 106.2 to 500.0. The author then calculated how many deaths each model required to be 95% certain of detecting the excess from 2 fibers/cm3 over 50 years, treating 0.1 fiber/cm3 as essentially unexposed. The answers ranged from 28 to 55,055 deaths from all causes in each of two groups, or roughly 110 to 220,000 people with an average 25-year follow-up. If linear relationships held, 25 years of exposure would about quadruple these numbers. Only three of the six studies gave fiber counts. The others had to be converted from particle counts. The author concluded that future epidemiology would probably need outcomes other than lung cancer or clinical asbestosis.

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: Review of exposure-limit history and of published dose-response data, with sample-size calculations (no new data collected)
• Who was studied: No new people studied. The author calculated estimates from six published studies, including Quebec miners and millers, U.S. retired asbestos products workers and a British asbestos textile factory (an original study and an update of that factory).
• Exposure: Asbestos exposure at the 2 fibers/cm3 standard for 50 years (or 25 years), compared with 0.1 fiber/cm3, which was treated as essentially unexposed. The studies at the two extremes dealt primarily with chrysotile.
• Main results:
  • Predicted lung cancer SMR at 100 fibers/cm3-yr by model: McDonald (BACOA) 106.2, Peto 107.8, Enterline (BACOA) 121.9, Weill 129.7, Peto (BACOA) 150.0, Dement 500.0
  • Under the Peto (BACOA) model, 1,003 deaths from all causes were needed in each of two groups to be 95% certain of detecting a 50% lung cancer excess from 2 fibers/cm3 for 50 years
  • All-cause deaths needed in each of two groups, by model in the order listed: 55,055 (McDonald BACOA), 35,035 (Peto), 4,758 (Enterline BACOA), 2,644 (Weill), 1,003 (Peto BACOA), 28 (Dement)
  • Approximate population needed with an average 25-year follow-up: 220,000, 140,000, 20,000, 10,000, 4,000 and 110 for the same six models
  • If linear relationships held, 25 years of exposure would produce half the excess of 50 years and would about quadruple the deaths and population sizes needed
  • Under those conditions, the required samples were judged unlikely to be obtainable for any model except Dement, and perhaps Peto (BACOA)
• The authors' conclusion: The author concluded that epidemiology may help set future asbestos limits, but would probably need outcome measures other than lung cancer or clinical asbestosis
• Limitations the authors state:
  • Only three of the six studies gave fiber counts. The others gave particle counts, which had to be converted to fibers/cm3.
  • Finding many workers with 50 years of exposure at 2 fibers/cm3 would be very difficult
  • Comparing with a standard population instead of a control group would make it hard to control confounding such as tobacco smoking

Topics

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

Medical terms in this study, explained in our Lexicon: Occupational Exposure, NIOSH, OSHA, Asbestos Exposure, Lung Cancer, Epidemiology.

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