Pseudoasbestos bodies and fibers in bronchoalveolar lavage of refractory ceramic fiber users

Refractory ceramic fibers (RCF) are widely used to replace asbestos in appl ications requiring high heat resistance. Ferruginous bodies mimicking asbes tos bodies (ABs) have been detected in the lungs of RCF production workers. This raises the question about their presence in other occupational groups and whether "typical ABs" still reflect past asbestos exposures in all set tings. An AB counting by phase-contrast light microscopy and a screening te st by analytical electron microscopy were systematically performed on all b ronchoalveolar lavage fluids (BALF) submitted to our laboratory in 1992 thr ough 1997 (n = 1,800). When RCF were detected in electron microscopy, the s tructures considered as "typical ABs" were marked under light microscopy an d prepared for further chemical and structural analysis. Pseudo-ABs on RCF were detected in samples from nine subjects (0.5%). All of them had worked either as foundry workers, steel workers, or welders. In these subjects, al umino-silicate fibers compatible with RCF accounted for 42% of the core fib ers analyzed, other nonasbestos fibers for 28%, and asbestos fibers for 30% . ABs thus remain a valid marker of asbestos retention but attention must b e paid to a possible occurrence of pseudo-asbestos bodies on RCF and other nonasbestos fibers in end-users of refractory fibers.