Quantification of the pathological response and fate in the lung and pleura of chrysotile in combination with fine particles compared to amosite-asbestos following short-term inhalation exposure

Abstract

The marked difference in biopersistence and pathological response between chrysotile and amphibole asbestos has been well documented. This study is unique in that it has examined a commercial chrysotile product that was used as a joint compound. The pathological response was quantified in the lung and translocation of fibers to and pathological response in the pleural cavity determined. This paper presents the final results from the study. Rats were exposed by inhalation 6 h/day for 5 days to a well-defined fiber aerosol. Subgroups were examined through 1 year. The translocation to and pathological response in the pleura was examined by scanning electron microscopy and confocal microscopy (CM) using noninvasive methods.The number and size of fibers was quantified using transmission electron microscopy and CM. This is the first study to use such techniques to characterize fiber translocation to and the response of the pleural cavity. Amosite fibers were found to remain partly or fully imbedded in the interstitial space through 1 year and quickly produced granulomas (0 days) and interstitial fibrosis (28 days). Amosite fibers were observed penetrating the visceral pleural wall and were found on the parietal pleural within 7 days postexposure with a concomitant inflammatory response seen by 14 days. Pleural fibrin deposition, fibrosis, and adhesions were observed, similar to that reported in humans in response to amphibole asbestos. No cellular or inflammatory response was observed in the lung or the pleural cavity in response to the chrysotile and sanded particles (CSP) exposure. These results provide confirmation of the important differences between CSP and amphibole asbestos.

Evaluation of the fate and pathological response in the lung and pleura of brake dust alone and in combination with added chrysotile compared to crocidolite asbestos following short-term inhalation exposure

“…For all fibers lengths there was no subsequent clearance and the clearance half-time was estimated as greater than 1000 days. In previous biopersistence studies with amphibole asbestos, the clearance half-time was reported to range from 418 to N1000 days (Musselman et al, 1994;Hesterberg et al, 1996Hesterberg et al, , 1998Bernstein et al, 2005bBernstein et al, , 2011.…”

“…Chrysotile can vary in characteristic depending upon the mine and processing of the ore. In earlier studies of chrysotile alone or of chrysotile mixed with a joint compound (Bernstein et al, 2003(Bernstein et al, , 2004(Bernstein et al, , 2005a(Bernstein et al, , 2005b(Bernstein et al, , 2008(Bernstein et al, , 2011 the clearance half-time of the longer fibers ranged from 0.7 to 11.4 days. The lack of a fiber related response in the histopathological findings in either the lung or the pleural cavity strongly suggests that the few (group 2: 6.5-10 fibers counted on the filter; group 3: 1-5 fibers counted on the filter) remaining fibers longer than 20 μm in the current study were in the airways and not in the parenchyma.…”

“…The authors reported that following 5 days of exposure tremolite asbestos produced a pronounced inflammatory response with the rapid development of granulomas followed by the development of fibrosis characterized by collagen deposition within these granulomas and by 90 days even mild interstitial fibrosis. In the Bernstein et al (2011) study amosite asbestos was evaluated as a positive control. The study was designed to evaluate the pathological response Fig.…”

Tumors that mimic asbestos-related mesothelioma: time to consider a genetics-based tumor registry?

“…Asbestos occurs in two mineralogic forms: commercially used amphiboles (e.g., commercially available amosite and crocidolite) and chrysotile. Amosite and crocidolite are considerably more persistent in tissue than is chrysotile, which disappears from lung tissue rapidly (Bernstein et al, 2005, 2010, 2011). This difference in biopersistence is believed to be the one of reasons that mesothelioma incidence rates are much higher in those who used or manufactured products with amosite and crocidolite, when compared to those exposed to only chrysotile (Churg, 1998; Hodgson and Darnton, 2000; Yarborough, 2006).…”

The So-called Short-Fiber Controversy: Literature Review and Critical Analysis

“…32 Animal investigations have also demonstrated long commercial amphibole fibers directly penetrating the visceral pleura and extending into the pleural space. 33 …”