Exposure to Brake Dust and Malignant Mesothelioma: A Study of 10 Cases with Mineral Fiber Analyses

Abstract

Objectives: A large number of workers in the USA are exposed to chrysotile asbestos through brake repair, yet only a few cases of malignant mesothelioma (MM) have been described in this population. Epidemiologic and industrial hygiene studies have failed to demonstrate an increased risk of MM in brake workers. We present our experience of MM in individuals whose only known asbestos exposure was to brake dust and correlate these findings with lung asbestos fiber burdens.Methods: Consultation files of one of the authors were reviewed for cases of MM in which brake dust was the only known asbestos exposure. Lung fiber analyses were performed using scanning electron microscopy (SEM) in all cases for which formalin-fixed or paraffinembedded lung tissue was available.Results: Ten cases of MM in brake dust-exposed individuals were males aged 51-73 yr. Nine cases arose in the pleura and one in the peritoneum. Although the median lung asbestos body count (19 AB/g) is at our upper limit of normal (range 0-20 AB/g), half of the cases had levels within our normal range. In every case with elevated asbestos fiber levels by SEM, excess commercial amphibole fibers were also detected. Elevated levels of chrysotile and non-commercial amphibole fibers were detected only in cases that also had increased commercial amphibole fibers.Conclusions: Brake dust contains exceedingly low levels of respirable chrysotile, much of which consists of short fibers subject to rapid pulmonary clearance. Elevated lung levels of commercial amphiboles in some brake workers suggest that unrecognized exposure to these fibers plays a critical role in the development of MM.

Asbestos Burden Predicts Survival in Pleural Mesothelioma

“…Hence, significant exposure to chrysotile could have occurred in those with lower numbers of ABs, and this might not be evident in our data. However, lung chrysotile fiber burden has been shown to correlate with asbestos body levels, arguing against significant chrysotile exposure (Butnor et al 2003). …”

The association among ferruginous body, uncoated fibers, asbestos and non-asbestos fibers in lung tissue in terms of length

“…Besides pathological investigation, the asbestos fiber count in the lung tissue is a crucial index of the exposure to asbestos 2 ) . To measure the concentration of asbestos fiber, identification of type and counting of each type of asbestos fibers with scanning electron microscope (SEM) 3 , 4 , 5 ) or transmission electron microscope (TEM) 6 , 7 , 8 ) must be done after preparing the lung tissue by ashing or digesting. Ferruginous body is an inorganic fiber, mainly amphibole asbestos 9 , 10 ) , coated with protein derived from macrophage which attacked the fiber by phagocytosis.…”

Comments on the 2014 Helsinki consensus report on asbestos

“…The sections of the Helsinki report dealing with pathology diagnosis are based on a selective reading of the medical literature. They rely overly much on certain published articles 2 , 3 , 4 ) while omitting reference to other important and highly relevant information. They are heavily influenced by the outdated and incorrect concept that analysis of lung tissue for asbestos fibers and asbestos bodies can provide data to contradict exposures that are documented in a reliable occupational history.…”