This study addressed the question of silica exposure, silicosis, and lung cancer in respect of lung particle burden. Sixty seven paraffin-embedded lung tissue samples of silicotic gold miners (39 non-lung cancer (NLC-SI) and 28 lung cancer (LC-SI)), were analyzed by transmission electron microscopy and energy dispersive X-ray spectroscopy for angular particles and fibres/cleavage fragments. Crystalline silica was characterized by X-ray powder diffraction on silver membrane filter. / Results indicated that both silicotic groups had non-significantly different concentrations and sizes of all particle types except quartz. Indeed, the NLC-SI group had a higher concentration of quartz than the LC-SI (3.77 $ mu$g/mg dry lung tissue compared to 2.47 $ mu$g/mg, p = 0.006, Mann-Whitney test). After adjusting for the differences in age at death, silicosis severity, and other dust exposure variables, but not for unknown smoking habit, the NLC-SI group still had a higher, through statistically non-significant, quartz concentration than did the LC-SI group (3.34 and 2.35 $ mu$g/mg respectively, p = 0.106, ANCOVA). This pattern was in good agreement with a pattern of a higher silicosis severity score in the NLC-SI group. The calendar year of first exposure was a prime determinant of lung burden of total particles, silica, and clay, with the coefficients of determination $ rm (R sp2)$ of 11-15%. A significant correlation between the concentrations of silica particles and quartz was observed, although quartz was the only significant predictor of the silicosis severity in the gold miners $ rm (p < 0.001, R sp2 = 20.5 %).$ A significant correlation between quartz concentration and the year interval since last exposure to death (r = + 0.25, $ rm p < 0.05)$ suggested a possibility of impaired lung clearance of quartz. Years of dust exposure did not show a significant linear relationship with any types of lung particles. The very low asbestos concentrations detected in only a small number of cases ruled out the suspicion of asbestos as a confounder of lung cancer in the miners. In conclusion, this study of lung concentration of quartz and other minerals did not support the association of silica, silicosis, and lung cancer.
| Identifer | oai:union.ndltd.org:LACETR/oai:collectionscanada.gc.ca:QMM.40385 |
| Date | January 1996 |
| Creators | Loosereewanich, Preecha |
| Contributors | DuFresne, Andre (advisor) |
| Publisher | McGill University |
| Source Sets | Library and Archives Canada ETDs Repository / Centre d'archives des thèses électroniques de Bibliothèque et Archives Canada |
| Language | English |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Format | application/pdf |
| Coverage | Doctor of Philosophy (Department of Occupational Health.) |
| Rights | All items in eScholarship@McGill are protected by copyright with all rights reserved unless otherwise indicated. |
| Relation | alephsysno: 001528927, proquestno: NN19743, Theses scanned by UMI/ProQuest. |
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