The objective of this thesis was to characterize the distribution, variability and determinants of exposures to extremely low frequency (ELF) electric and magnetic fields in environments where no information was previously available, and to advance the methodology of exposure estimation. The thesis is divided into three related papers. / The first paper reports a study of personal ELF field exposure measurements of 465 randomly selected workers in an electrical utility. By job category, arithmetic mean magnetic field exposures ranged from 0.09 to 2.36 $ mu$T (electric fields: 2.5 to 400 V/m). ELF magnetic field exposures were highest for substation workers, hydroelectric generating station operators and cable splicers; electric fields were highest for forestry workers, equipment electricians and distribution linemen. Most alternative indices of exposure were highly correlated with the arithmetic or the geometric means (r $ ge$ 0.8). Job category explained half of the total variance in logarithms of weekly magnetic and electric field means. / The second paper reports a method developed to estimate past ELF field exposures of the electric utility workers. The present intensities and durations of exposures for tasks were measured, then separately extrapolated to the past based on information from interviews with long-service personnel at the utility. From reconstructed time weighted average (TWA) exposures, magnetic fields were estimated to have increased most over time for substation and distribution-line jobs; the increase for electric fields was less than for magnetic. The method is applicable to other exposures where monitoring records allow calculation of the intensity and duration of exposures for tasks and estimates of past intensities and durations of exposures for these tasks can be obtained. / In the third paper, the methodology developed in the occupational setting was applied to a study of personal exposures to ELF fields among 365 randomly selected Canadian children. Overall, the arithmetic mean total magnetic field was 0.121 $ mu$T (electric field: 14.4 V/m), with magnetic fields highest in Quebec and lowest in Alberta. Magnetic fields were highest at home during the day. Measurements were at their lowest at night but provided the highest correlation with total magnetic field exposure (r =.91). This study found that children's magnetic fields exposures varied substantially between certain provinces (province accounting for 14.7% of the variation) most likely because of differences in the proportion of residences in multiple dwellings, heated electrically or cooled by air conditioning. These attributes were identified as potentially useful predictors of magnetic fields.
| Identifer | oai:union.ndltd.org:LACETR/oai:collectionscanada.gc.ca:QMM.42012 |
| Date | January 1997 |
| Creators | Deadman, Jan-Erik. |
| Contributors | Armstrong, Ben (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: 001559056, proquestno: NQ29919, Theses scanned by UMI/ProQuest. |
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