Mesothelioma: risk apportionment among asbestos exposure sources

Our plain-English summary of Mesothelioma: risk apportionment among asbestos exposure sources, by B. Price, A. Ware (Risk Analysis, 2005).

The study

• Authors: B. Price, A. Ware
• Journal: Risk Analysis
• Published: 2005;25(4):937-43
• Cited by: 16 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

The mesothelioma epidemic in the United States, which peaked during the 2000-2004 period, can be traced to high-level asbestos exposures experienced by males in occupational settings prior to the full recognition of the disease-causing potential of asbestos and the establishment of enforceable asbestos exposure limits by the Occupational Safety and Health Administration (OSHA) in 1971. Many individuals diagnosed with mesothelioma where asbestos has been identified as a contributing cause of the disease have filed claims seeking compensation from asbestos settlement trusts or through the court system. An individual with mesothelioma typically has been exposed to asbestos in more than one setting and from more than one asbestos product. Apportioning risk for mesothelioma among contributing factors is an ongoing problem faced by occupational disease compensation boards, juries, parties responsible for paying damages, and currently by the U.S. Senate in its efforts to formulate a bill establishing an asbestos settlement trust. In this article we address the following question: If an individual with mesothelioma where asbestos has been identified as a contributing cause were to be compensated for his or her disease, how should that compensation be apportioned among those responsible for the asbestos exposures? For the purposes of apportionment, we assume that asbestos is the only cause of mesothelioma and that every asbestos exposure contributes, albeit differentially, to the risk. We use an extension of the mesothelioma risk model initially proposed in the early 1980s to quantify the contribution to risk of each exposure as a percentage of the total risk. The percentage for each specific discrete asbestos exposure depends on the start and end dates, the intensity, and the asbestos fiber type for the exposure. We provide justification for the use of the mesothelioma risk model for apportioning risk and discuss how to assess uncertainty associated with its application.

In plain English

This was a methods paper, not a study of real patients. The authors described a way to divide a person's mesothelioma risk among their different asbestos exposures, so compensation could be split among responsible parties. They extended a risk model first proposed in the early 1980s, in which each exposure's share depends on its start and end dates, intensity and fiber type. For the purpose of apportionment, they assumed asbestos was the only cause of mesothelioma. Their example was a hypothetical man diagnosed at age 68. He did 20 years of home repair with chrysotile-only materials (0.85 fibers per cc), then 15 years of pipe and boiler work with a 50/50 chrysotile-amosite mix (averaging 1.72 fibers per cc). Using potency ratios from Hodgson and Darnton's earlier analysis, the model split the risk from these two exposure sources: 2.3% to the home repair work and 97.7% to the pipe and boiler work. The authors noted that the percentages describe a group diagnosed at the same age with the same exposure profile, not a unique individual. They concluded that the model is a scientifically based, practical method for apportionment.

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: Methods (risk-modeling) paper illustrated with a hypothetical worker; no new data on real people
• Who was studied: One hypothetical male worker, born 1935, who began home repair/remodeling work in 1955 at age 20 and was diagnosed with mesothelioma in 2003 at age 68
• Exposure: Hypothetical profile: home repair/remodeling from age 20 to 40 with chrysotile-only materials at 0.85 f/cc. Then pipe and boiler insulation maintenance, repair and replacement from age 40 to 55 with a 50%/50% chrysotile and amosite mix, averaging 1.72 f/cc. The pipe and boiler intensities were the OSHA permissible exposure limits in force at the time.
• Main results:
  • For the hypothetical worker, the model divided the risk among the two specific identifiable exposure sources, not total risk including background or spontaneous risk. It assigned 2.3% to home repair/remodeling (chrysotile) and 97.7% to pipe and boiler maintenance, repair and replacement (chrysotile and amosite).
  • The calculation used k = 3.0 and age T = 68. Relative potencies came from Hodgson and Darnton's earlier analysis: chrysotile = 1, amosite = 100, and 50.5 for the 50/50 chrysotile-amosite mix.
• The authors' conclusion: The authors concluded that the mesothelioma risk model provides a scientifically based, practical and effective method for apportioning compensation among responsible parties where previously there was none
• Limitations the authors state:
  • The model parameters come from population data, so the percentages represent a group of people with the same exposure profile and age at diagnosis, not a unique individual
  • No approaches for personalizing mesothelioma risk to an individual's own sensitivity had been proposed or evaluated
  • The authors did not address how much risk comes from background exposure or spontaneous mesothelioma compared with exposures linked to responsible parties
  • For apportionment, the method assumes asbestos is the only cause of mesothelioma

Topics

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

Medical terms in this study, explained in our Lexicon: Mesothelioma, Asbestos Exposure, OSHA, Occupational Disease, Damages.

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