Health Effects of Censored Elongated Mineral Particles: A Critical Review

Abstract

Detection limits for asbestos and elongated mineral particles (EMPs) necessarily depend on what “counts” by a given test method or procedure. Censored data in this context include both fibers that fall below and outside of a laboratory’s counting criteria. For microscopic methods, in particular, counting criteria may be based on health effects, methodological convenience, or geologic definition. For purposes of public health, data censorship for asbestos or EMPs should be predicated on the toxicity of the fibers and not on a geologic definition. Some geologic definitions of EMPs are inconsistent with existing evidence of EMP toxicity. For this study, we used systematic search techniques and grounded theory to review published studies, government records, corporate documents, and public statements. Research links asbestos health effects to fiber dimensions, fiber surface area, biopersistence, chemical composition, and surface properties. We review the evidence that indicate that short fibers (<5 µm long), thin fibers (<0.2 µm wide), some nonasbestos EMPs, and asbestos mineral “cleavage fragments” affect human health. Current EMP test methods allow the censorship of these fibers from reported data. We believe that a health perspective is crucial for determining what data to censor in the measurement of EMPs. Fiber-counting methods should be altered to better encompass health-relevant EMPs by employing transmission electron microscopy, eliminating the requirement for an asbestiform habit, including short fibers (<5 µm long), and removing all minimum fiber width criteria. EMP test methods should explicitly call for counting talc and erionite fibers.