There has been recent interest in the possible carcinogenic potential of vegetable fibers (plant fibers) containing amorphous silica. These fibers referred to as Biogenic Amorphous Silica Fibers (BAS) are the normal constituents of number of plant species such as sugar cane, wheat, barley, oats, rice etc. Exposure to fibers within the respirable range has been documented during sugar cane and rice farming and processing operations. Some studies have suggested that such exposure could increase the risk for lung cancer while others have suggested the contrary. In countries like India, sugar cane farming is the major occupation in a number of provinces. A large workforce is involved in its farming and processing. In order to investigate the risk for lung cancer among one such population in Western Maharashtra, we carried out a hospital-based case-control study in the region. As part of this study we measured the exposures to BAS fibers during the harvesting of the sugar cane and the processing of the cane in the mills. / Cases of lung cancer were ascertained from 6 cancer treatment centers and matched to controls who had other types of cancers on age, sex, area of residence and timing of diagnosis. After controlling for potential confounding variables such as smoking, asbestos exposure, family history of lung cancer, income, education and farming of other crops, the risk for lung cancer was elevated in workers involved in the farming of the sugar cane, Odds ratio (OR) 1.92; 95% Confidence Interval (CI) 1.08--3.40. Specifically, the risks were elevated for those involved in the preparation of the farm (OR: 1.81; 95% CI: 0.99--3.27) and in the burning of the farms after harvesting (OR: 1.82; 95% CI: 0.99--3.34). Risks were moderately elevated for those involved in the harvesting of the crop (OR: 1.41; 95% CI: 0.70--2.90) and in the processing of the crop in the sugar mills (OR: 1.70; 95% CI: 0.20--12.60). Smoking modified the relationship between sugar cane farming and lung cancer. Sugar cane farmers who smoked had a 6-fold higher risk compared to those who never farmed and did not smoke. / Environmental measures both during harvesting and processing of the crop in the mills showed exposure to vegetable fibers. Some of these fibers contained silica and resembled BAS fibers in morphology. However a majority of the fibers lacked mineral content and were unlikely to be those of BAS. / The epidemiological study showed increased risk for lung cancer among sugar cane farmers but the limited exposure data did not show high concentration of BAS fibers. The role of polynuclear aromatic hydrocarbons and crystalline silica in particular needs to explored in future studies.
| Identifer | oai:union.ndltd.org:LACETR/oai:collectionscanada.gc.ca:QMM.35975 |
| Date | January 1999 |
| Creators | Amre, Devendra. |
| Contributors | Infante-Rivard, Claire (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 Epidemiology and Biostatistics.) |
| Rights | All items in eScholarship@McGill are protected by copyright with all rights reserved unless otherwise indicated. |
| Relation | alephsysno: 001681969, proquestno: NQ55297, Theses scanned by UMI/ProQuest. |
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