Asbestos fiber length as related to potential pathogenicity: A critical review

Abstract

The data presented argue that asbestos fibers of all lengths induce pathological responses and that caution should be exerted when attempting to exclude any population of inhaled fibers, based on their length, from being contributors to the potential for development of asbestos-related diseases.

Prismatic to Asbestiform Offretite from Northern Italy: Occurrence, Morphology and Crystal-Chemistry of a New Potentially Hazardous Zeolite

“…According to [4], an elongated particle is defined as "inhalable" for humans when its diameter is <3.5 µm, while [19] considers as inhalable the fibers with a diameter-length ratio ≥1:3, a length >5 µm, and a diameter <3 µm. Fibers ≤0.25 µm in diameter and >8 µm in length seem to be the most carcinogenic [3], but the majority of fibers detected in the lung and mesothelial tissues are generally <1 µm in diameter and shorter than five µm in length [5,75,76]. Consequently, small-size fibers should not be excluded from those contributing to the induction of human MM, especially in high exposure environments.…”

Malignant pleural mesothelioma in a female Lion (Panthera leo)

“…Experimental evidence suggests that asbestos fibers pose a risk for mesothelioma (Gibbs and Berry, 2008), and that heavy and prolonged exposure to chrysotile can produce lung cancer (Bernstein and Hoskins, 2006). Studies performed in rats also supported that chrysotile fibers were contributory to the induction of malignant mesothelioma (Dodson et al, 2003).…”

“…To our best knowledge, no asbestos fibers have been found in other cases of (large) feline mesotheliomas. Possible reasons for the absence of asbestos fibers in an asbestos-related mesothelioma are related to a ready clearing of short fibers and asbestos dust (Dodson et al, 2003). On the contrary, chrysotile asbestos were identified by XRD in samples from shelter material.…”

Collegium Ramazzini response to ‘Asbestos, asbestosis, and cancer, the Helsinki criteria for diagnosis and attribution 2014: recommendations’

“…Today they are readily visible under the electron microscope and are counted by some laboratories and not by others. The Helsinki report considers neither short asbestos fibers nor their possible contribution to the pathogenesis of asbestos-related diseases (17)(18)(19)8). It also does not consider the well-documented wide intra-and inter-laboratory variability in procedures for the counting of short fibers (7,10,8) (iii) Use of the scanning electron microscope (SEM) at low magnification as a tool for evaluation of asbestos-related disease.…”