Lung Mineral Fibers of Former Miners and Millers from Thetford-Mines and Asbestos Regions: A Comparative Study of Fiber Concentration and Dimension

Abstract

Fiber dimension and concentration may vary substantially between two necropsy populations of former chrysotile miners and millers of Thetford-Mines and Asbestos regions. This possibility could explain, at least in part, the higher incidence of respiratory diseases among workers from Thetford-Mines than among workers from the Asbestos region. The authors used a transmission electron microscope, equipped with an x-ray energy-dispersive spectrometer, to analyze lung mineral fibers of 86 subjects from the two mining regions and to classify fiber sizes into three categories. The most consistent difference was the higher concentration of tremolite in lung tissues of workers from Thetford-Mines, compared with workers from the Asbestos region. Amosite and crocidolite were also detected in lung tissues of several workers from the Asbestos region. No consistent and biologically important difference was found for fiber dimension; therefore, fiber dimension does not seem to be a factor that accounts for the difference in incidence of respiratory diseases between the two groups. The greater incidence of respiratory diseases among workers of Thetford-Mines can be explained by the fact that they had greater exposure to fibers than did workers at the Asbestos region. Among the mineral fibers studied, retention of tremolite fibers was most apparent.

Quantitative Analysis of Asbestos Burden in a Series of Individuals with Lung Cancer and a History of Exposure to Asbestos

“…The exposures to the "noncommercial" forms of asbestos may be due to their presence as mixtures in products made from other minerals. For example, it has been reported that some chrysotile is "contaminated" with amphiboles (McDonald & McDonald, 1997;McDonald et al, 1989;Churg, 1988;Churg et al, 1993;Sebastien et al, 1989;Nayebzadeh et al, 2001). It has also become increasingly evident to health scientists, as mineralogists have long recognized, that types of asbestos can be found in mineral deposits that are mined for various products often construed to be asbestos free Dodson & Levin, 2001;DeVuyst et al, 1987;McDonald et al, 1986).…”

Asbestos in brakes: Exposure and risk of disease

“…Only two of the seven ATSDR panelists felt there was a reasonable certainty of no harm from short fibers while the other five remained concerned about the ability of short fibers to cause harm [ATSDR, 2003]. In fact, tremolite asbestos fibers were found to produce the highest average fibrosis grades when exposures were to average tremolite fibers less than 5 mm in length [Nayebzadeh et al, 2001].…”

Revision of French Occupational Exposure Limits of Asbestos and Recommendation of Measurement Method: Can the Dimensional Characteristics of the Asbestos Fibers (Long, Thin, Short) Be Taken Into Account?

“…The gradation of the diameter of the bare fibers and central fibers of asbestosic bodies according to the type of asbestos mainly follows the following trend: chrysotile < crocidolite < amosite < tremolite < anthophyllite. The diameter, however, tends to increase with the length of the fibers (Case and Dufresne, 1997;Case et al, 2000;Nayebzadeh et al, 2001) Long asbestos fibers, and in particular amphibole fibers, are found in the lungs of cases exposed through activities principally based on SAFs, such as servicing brake pads, which are known to only contain chrysotile (Finley et al, 2007).…”