Microscopical Analyses of Asbestos-Cement Pipe and Board
THE MICROSCOPE
2018, Volume 66:1, pp. 3–20
DOI
https://doi.org/10.59082/TNXT8507
AUTHORS
James R. Millette, Steven Compton, and Christopher DePasquale
ABSTRACT
Hundreds of thousands of miles of asbestos cement (AC) pipe were installed in water systems throughout the world, especially during the 1960s and 1970s, and many are still in use. AC pipes are also used as telephone ducts, cable conduits, and warmair heating ducts. The pipes contain from 10% to 25% asbestos by weight. The major U.S. manufacturers combined chrysotile and crocidolite asbestos in their formulations. With the aid of low magnification microscopy, the blue crocidolite fibers can easily be seen mixed with white chrysotile fibers on the surfaces of the pipe. Scanning electron microscopy (SEM) analyses of dust released when touching AC pipe surfaces show asbestos fibers are released during handling of the pipe. Polarized light microscopy (PLM) analyses found 10% to 35% chrysotile and <1% to 15% crocidolite by volume in various samples of AC pipe. A review of several groups of studies — including those by the authors in which standard phase contrast microscopy (PCM) was used to test air samples collected while individuals worked with AC pipe — showed a range of concentrations from below detection to more than 100 fibers per cubic centimeter (F/cc) of air, depending on the tasks. The highest levels were associated with cutting AC pipe with power saws. Levels from 0.2 to 196 F/cc were found when reviewing studies of drilling and cutting AC boards and from non-detectable to 1.1 F/cc for handling boards such as dismantling roofs and stacking sheets.