FIBERS IN LUNG TISSUES OF MESOTHELIOMA CASES AMONG MINERS AND MILLERSOF THE TOWNSHIP OF ASBESTOS, QUEBEC

Twenty cases of mesothelioma among miners of the township of Asbestos, Quebec, Canada, have been reported. To further explore the mineral ch aracteristics of various fibrous material, we studied the fibrous inor ganic content of postmortem lung tissues of 12 of 20 available cases. In each case, we measured concentrations of chrysotile, amosite, croci dolite, tremolite, talc-anthophyllite, and other fibrous minerals. The average diameter, length, and length-to-diameter ratio of each type o f fiber were also calculated. For total fibers > 5 mum, we found > 1,0 00 asbestos fibers per mg tissue (f/mg) in all cases; tremolite was ab ove 1,000 f/mg in 8 cases, chrysotile in 6 cases, crocidolite in 4 cas es, and talc anthophyllite in 5 cases. Among cases with asbestos fiber s, the tremolite count was highest in 7 cases, chrysotile in 3 cases, and crocidolite in 2 cases. The geometric mean concentrations of fiber s greater-than-or-equal-to 5 mum were in the following decreasing orde r: tremolite > chrysotile > other fibers > talc-anthophyllite > amosit e. For total fibers < 5mum, we found > 1,000 fibers per mg tissue (f/m g) in all cases; tremolite was above 1,000 f/mg in 12 cases, chrysotil e in 8 cases, crocidolite in 7 cases, and talc-anthophyllite in 6 case s. Tremolite was highest in 8 cases, chrysotile in 2 cases, and crocid olite and amosite in 2 cases. The geometric mean concentrations of fib ers < 5 mum were in the following decreasing order: tremolite > other fibers > chrysotile > crocidolite > talc-anthophyllite > amosite. We c onclude, on the basis of the lung burden analyses of 12 mesothelioma c ases from the Asbestos township of Quebec, that the imported amphibole (crocidolite and amosite) were the dominant fibers retained in the lu ng tissue in 2/12 cases. In 10/12 cases, fibers from the mine site (ch rysotile and tremolite) were found at highest counts; tremolite was cl early the highest in 6, chrysotile in 2, and 2 cases had about the sam e counts for tremolite and chrysotile. If a relation of fiber burden-c ausality of mesothelioma is accepted, mesothelioma would be likely cau sed by amphibole contamination of the plant in 2/12 cases and by the m ineral fibers (tremolite and chrysotile) from the mine site in the 10 other cases. (C) 1995 Wiley-Liss, Inc.