Meeting report: mode(s) of action of asbestos and related mineral fibers

Our plain-English summary of Meeting report: mode(s) of action of asbestos and related mineral fibers, by M.R. Gwinn, D. DeVoney, A.M. Jarabek, et al (Environmental Health Perspectives, 2011).

The study

• Authors: M.R. Gwinn, D. DeVoney, A.M. Jarabek, B. Sonawane, J. Wheeler, D.N. Weissman, S. Masten, C. Thompson
• Journal: Environmental Health Perspectives
• Published: 2011;119(12):1806-10
• Cited by: 15 articles, as counted by NIH iCite
• Read it: PubMed · Publisher · Free full text

Abstract

Background: Although asbestos in general is well known to cause a range of neoplastic and non-neoplastic human health effects, not all asbestos fiber types have the same disease-causing potential, and the mode of action (MOA) of specific types of asbestos and related fibers for various health outcomes are not well understood.

Objectives: A workshop was held to discuss the state of the science of the MOA for asbestos-related disease. The objective was to review the range of asbestos-induced health effects (including those at sites remote to the respiratory tract). We sought to identify existing knowledge gaps and define what research is needed to address these gaps and advance asbestos research.

Discussion: Discussions centered on areas of uncertainty in the field, including the ways asbestos is defined and characterized, the role of different fiber characteristics (e.g., length and mineralogy) in disease, and the impact of low-dose exposures on human health. Studying the dosimetry and mode of action of multiple fiber types would enhance our understanding of asbestos-related disease. To better elucidate the MOA of specific asbestos fibers, the risk assessor requires data as to specific characteristics of asbestos in determining fiber toxicity (e.g., surface area, mineral type), which may inform efforts to assess and control exposures and prevent adverse human health outcomes for the diverse range of fiber types. Specific research aims were defined for these topics and for overarching issues to be addressed, including the use of standardized terminology, test materials, and better experimental models to aid in data extrapolation to humans.

Conclusion: To resolve these and other issues, participants agreed that diverse scientific disciplines must coordinate to better understand the MOA leading to the various asbestos-related disease end points.

In plain English

This article was a meeting report, not a study with new data. It summarized a workshop held on 16 to 17 December 2009 in Chapel Hill, North Carolina, run by the National Institute of Environmental Health Sciences with the U.S. Environmental Protection Agency and the Centers for Disease Control and Prevention. Expert teams wrote reviews on pulmonary, pleural and non-pulmonary health outcomes, mutagenicity, susceptibility and low-dose exposure. The writers, invited reviewers and public observers then discussed these reviews. The term "asbestos" was used broadly to include other elongate mineral fibers. The report said there was no consensus on how to define "asbestos" or "fiber." It also found no consensus on whether fibers shorter than 5 micrometers play a role in disease, or on the relative potency of different fiber types. There was general agreement that some asbestos types are genotoxic in laboratory (in vitro) studies, and less agreement on whether they are mutagenic. The report stated that measuring dose by mass alone is probably not sufficient. The authors concluded that major knowledge gaps remain about how various types of asbestos fibers act to cause disease.

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: Meeting report summarizing an expert workshop; no new data were collected
• Who was studied: Workshop participants: expert writing teams who prepared topic reviews, invited reviewers recommended by those teams, and public observers, at a workshop in Chapel Hill, North Carolina, USA, 16 to 17 December 2009. The number of participants is not given.
• Exposure: Asbestos in general, used as a broad term that also covered other elongate mineral fibers. Discussion covered how asbestos is defined and characterized, fiber characteristics such as length and mineralogy, and low-dose exposures.
• Main results:
  • The report stated there is no consensus on how to define the basic terms "asbestos" and "fiber."
  • Participants did not agree on whether short fibers (under 5 micrometers) play a role in causing disease. Many researchers believe they do not, and others disagree.
  • Participants did not reach consensus on the relative potency of different fiber types.
  • There was general agreement that some types of asbestos are genotoxic in vitro (in laboratory cell studies). There was less agreement on whether asbestos fibers are mutagenic, particularly in vivo.
  • A companion review (Huang et al. 2011), discussed at the workshop, suggested a role for mutagenesis in asbestos-induced neoplastic (cancer) diseases but not in non-neoplastic diseases.
  • The report stated that using mass alone as the dose measure is probably not sufficient when comparing fiber types.
  • Participants agreed that much is known about the mechanisms of asbestos-induced lung cancers, but that understanding is limited for how fiber properties contribute to all asbestos-induced diseases, particularly non-pulmonary ones.
  • Breakout groups proposed research ideas, including involving geologists more in toxicology and epidemiology studies.
• The authors' conclusion: The authors reported that the workshop participants concluded major knowledge gaps still hinder understanding of the modes of action of various types of asbestos fibers.
• Limitations the authors state:
  • The workshop did not aim to draw conclusions on the adverse effects of specific mineral fibers. It only identified areas of agreement and uncertainty.
  • A full discussion of each type of asbestos fiber was beyond the scope of the report.

Topics

Medical terms in this study, explained in our Lexicon: Mineral Fiber, Mineralogy.

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