Comments on the Health Effects Institute-Asbestos Research (HEI-AR) report: "Asbestos in public and commercial buildings," with emphasis on risk assessment methods used

Our plain-English summary of Comments on the Health Effects Institute-Asbestos Research (HEI-AR) report: "Asbestos in public and commercial buildings," with emphasis on risk assessment methods used, by T.D. Sterling, C.W. Collett, W.L. Rosenbaum, et al (American Journal of Industrial Medicine, 1993).

The study

• Authors: T.D. Sterling, C.W. Collett, W.L. Rosenbaum, J.J. Weinkam
• Journal: American Journal of Industrial Medicine
• Published: 1993;24(6):767-81
• Cited by: 8 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

A Health Effects Institute--Asbestos Research Report calculates the risk of exposure to environmental asbestos fibers (EAF) by downward extrapolation from the mortality of workers exposed for 20 years. This extrapolation is improper because 1) relative risks of asbestos exposure very likely are not linearly progressive; 2) the composition of EAF may not be equivalent to that in mining or fabricating; 3) the same environmental asbestos concentration probably represents different exposure doses for different populations; and 4) health effects of asbestos exposure on children, seniors, patients, the institutionalized, the handicapped, and the chronically ill may not be the same as those of healthy workers. Evidence of asbestos-related disease among family members of exposed workers demonstrates that the risk observed for EAF is substantially larger than that estimated from downward extrapolation and suggests a basis for an alternative approach to estimating asbestos-related health risks. Such epidemiologic procedures are well established and ought to form the basis for detecting the health effects of EAF. It is also unclear which industry supports HEI-AR.

In plain English

This article was the authors' commentary on a 1992 Health Effects Institute-Asbestos Research (HEI-AR) report, "Asbestos in Public and Commercial Buildings." It collected no new data. The report estimated risk from environmental asbestos fibers by straight-line (linear) downward extrapolation from asbestos workers exposed for 20 years at 10 fibers per milliliter. The authors argued that four of the assumptions behind this method may not hold: that risk falls in a straight line with dose, that building fibers match those in mining and fabricating, that a given fiber level means the same dose for everyone, and that children, seniors and the ill respond like healthy workers. They re-plotted rat injection data from the report. For amosite, crocidolite and chrysotile A, the proportion of rats with tumors quickly reached between .6 and .8 and then leveled off. They also fitted a curved function to published data on amosite factory workers. The authors faulted the report for leaving out family members of asbestos workers. They concluded that downward extrapolation is improper and that epidemiologic studies of people exposed involuntarily offer an alternative.

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: Commentary and critique of a published report's risk assessment method, including the authors' re-plotting and curve-fitting of previously published animal and worker data
• Who was studied: No study population. The subject is the 1992 HEI-AR report on asbestos in public and commercial buildings. The authors also re-analysed published data: rat injection studies reproduced in the report, and Seidman et al. (1986) on a cohort of 820 men in an amosite asbestos factory in Paterson, New Jersey.
• Exposure: Environmental asbestos fibers (EAF) encountered outdoors, in residences, and in commercial and public buildings by people who are not asbestos workers. Data discussed include amosite, crocidolite and chrysotile A injected into rats, and amosite exposure in factory workers.
• Main results:
  • The HEI-AR method starts from the lifetime cancer risk of asbestos workers exposed for 20 years at 10 f/mL and scales it down in proportion for lower exposures.
  • In rat injection data from the HEI-AR report (doses from 0.01 mg to 15 mg of amosite, crocidolite and chrysotile A), the authors found that the proportion of rats developing tumors rose rapidly to between .6 and .8 and then stayed level or rose only slightly.
  • The authors fitted the function SMR = 1 + square root of (A times dose) to mortality ratios from Seidman et al. (1986) for all asbestos disease and for lung cancer in amosite factory workers. They reported R-squared values of 0.95, 0.92, 0.98 and 0.94 for the four figures, and stated that downward linear extrapolation from high dose to zero would grossly misrepresent the true risk in these data.
  • Lung cancer relative risks for Quebec miners and millers, as shown in the HEI-AR report, did not rise steadily with exposure. The authors described these data as sparse and erratic and said they support no particular dose-response function.
  • The HEI-AR report estimated 4-40 premature cancer deaths per million persons exposed to increased ambient asbestos levels. The authors stated that detecting an annual increased risk of 40 per 1,000,000 would require on the order of 200,000 cases and as many controls.
  • The authors cited another study (Joubert et al., 1991) that observed 43 cancer deaths where 25 were expected among 115 decedents who had been involuntarily exposed to asbestos. They used it to argue that household risk can be detected in small samples.
  • The authors stated that the HEI-AR report left out family members of asbestos workers, including homemakers who washed work clothing, who are exposed to asbestos carried home on the worker.
• The authors' conclusion: The authors concluded that downward extrapolation from workers' mortality is improper. Based on evidence of disease among family members of asbestos workers, they concluded that the risk from involuntary exposure to environmental asbestos fibers is considerably higher than extrapolation estimates. They proposed epidemiologic studies of involuntarily or occasionally exposed populations as an alternative, and said the sources of HEI-AR's support should be clearly stated.
• Limitations the authors state:
  • The authors stated that the good fit of their square-root function to the Seidman data does not prove it is the true risk function. It only suggests that a proper nonlinear model might be similar.

Topics

Medical terms in this study, explained in our Lexicon: Relative Risk, Asbestos Exposure.

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