Asbestos fiber length and its relation to disease risk

Abstract

Differences in chemical and crystalline composition, fiber dimension, aerodynamic characteristics and biodurability are among the critical factors that define the toxicological and pathological consequences of asbestos exposure. Specifically, fiber dimension can impact whether the fiber is respired, whether and how deeply it is deposited in the lung, and how efficiently and rapidly it may be cleared. This paper provides a current, comprehensive evaluation of the weight of evidence regarding the relationship between asbestos fiber length and disease potency (for malignant and nonmalignant endpoints). In vitro studies, animal exposure studies and epidemiology data were reviewed. We found that the data reported over the last several decades consistently support the conclusions that exposure to fibers longer than 10 µm and perhaps 20 µm are required to significantly increase the risk of developing asbestos-related disease in humans and that there is very little, if any, risk associated with exposure to fibers shorter than 5 µm. Fiber length as a predictor of potency has been evaluated by several federal agencies in the U.S. and could significantly influence future regulatory decisions for elongated mineral particles (EMPs) and high-aspect ratio nanoparticles (HARNs).

Keywords:

• Asbestos
• fiber length
• risk assessment
• short fiber
• lung cancer
• fibrosis
• mesothelioma

Disclosure statement

All of the authors are employed by Cardno ChemRisk, a consulting firm that provides scientific advice to the government, corporations, law firms and various scientific/professional organizations. This manuscript was prepared and written exclusively by the authors. No outside financial support was provided to any of the authors for preparing the manuscript. One of the authors (C.A.B.) has served as an expert in asbestos-related litigation. It is likely that this work will be relied upon in occupational health and exposure assessment research and asbestos-related litigation.