The prevalence of asthma and the role of occupational exposures was investigated in a cross-sectional study of 498 Montreal adults aged 20 to 44 years. Prevalences of asthma standardised for age and gender, using four definitions were: current wheeze: 23 8%, asthma symptoms and/or medicine: 12.9%, airway hyper-responsiveness: 15.1%, airway hyper-responsiveness and current wheeze: 7.0%. Imputation to adjust for non-response to airway challenge gave similar results. 56.9% of subjects reported occupational exposure ever to sensitisers and 10.8% to irritants. Current wheeze was associated with exposure to irritants (OR: 2.12 (1.03, 4.34)), and airway hyper-responsiveness with exposure to sensitisers (OR: 2.20 (1.10, 4.38)). Childhood asthma and atopy did not affect the associations. Population attributable risk was about 30% for airway hyper-responsiveness with exposure to sensitisers, and 5% for current wheeze with exposure to irritants. Studies with more precise exposure information may provide better evidence for the causality of the association.

The influence of psychological status on recovery from a first lifetime episode of acute low-back pain was assessed in compensated workers seen in a physiatry clinic. One hundred thirty-four participants of a back school intervention trial were selected and followed for 1 year. The objectives were to determine the evolution of psychological distress, well-being, pain, self-reported disability and spinal flexibility, and to determine the psychological factors associated with return to work and recurrence. Improvement occurred post-treatment in all measures except well-being which did not fluctuate over the year. Additional improvement in functional disability occurred at 6 and 12 months. Using multiple logistic regression, low baseline psychological distress predicted late return to work and high baseline well-being predicted recurrence. A second model for recurrence that was constructed with post-treatment scores on the longitudinal measures had greater predictive power than the model using baseline scores. These results have implications for the management of return to work.

The goal of this study was to verify if differences in respirable dust and respirable quartz concentrations exist with respect to the mines, the ore deposit types and the nature of workstations. / One hundred and seventy-nine respirable dust samples were collected in the six mines studied, in compliance with the method recommended by the Institut de recherche en sante et securite du travail du Quebec (IRSST). Then, samples were analysed using X ray powder diffraction technique to determine respirable quartz concentrations. / Results indicated statistically significant differences in the normalised exposure levels to respirable dust (p = 0.017), to respirable quartz (p < 0.001) as well as the quartz percentage in the respirable dust (p < 0.001) of the six mines studied. When grouped by ore deposit type, normalized exposure levels to respirable dust were not statistically different. However, statistically significant differences were noticed for normalized exposure levels to respirable quartz (p = 0.004) and respirable quartz percentage (p < 0.001) according to ore deposit types. / For all mines studied, respirable dust concentrations were all below the admissible exposure value whereas about 9% of the respirable quartz concentrations were equal or above the admissible exposure limit. Gold ore deposits hosted in quartz veins had the highest normalized respirable quartz exposure levels, as well as the highest percentage of quartz in the respirable dust when compared to gold ore deposits with sulfide lodes, the copper-zinc ore deposit and the disseminated gold ore deposit. / The study also revealed that workers who worked in the ore crushing and hoisting departments as well as loading and transport had higher normalised exposure levels to respirable quartz than workers who worked in the drilling and blasting or those who worked in the maintenance department. / In conclusion, this study stressed that quartz content in the mined rocks seems to be the most important factor influencing on respirable quartz concentrations in the mine worker's respiratory zone, but the relation between the two variables were not strongly correlated (Rs = 0.254, p = 0.005). Furthermore, the study showed that the gold ore deposits with quartz lodes had the highest normalized exposure levels to respirable quartz. Also, the workers assigned to ore crushing and hoisting departments as well as transport and loading had the highest exposure levels to respirable quartz. (Abstract shortened by UMI.)

Microcomputer technology and the provision of alternative data entry devices offers numerous opportunities for physically disabled individuals to integrate into work and school settings. For therapists specializing in adapted access one of the main challenges involves prescribing and customizing suitable input devices since objective procedures to facilitate this process are lacking. The two papers presented in this thesis aimed to respond to this limitation. In the first paper the adapted access process was viewed within the context of a human factors model. A critical review of the literature relating specific human factors criteria (e.g. digit loading) to ergonomic solutions (e.g. input/output efficiency) substantiated clinical approaches to adapted device prescription and customization. Two case studies were used to illustrate the application of this approach to physically disabled individuals. The second paper investigated therapists' abilities to judge the mechanical characteristics of switches. Objective data characterizing the activation force-displacement trajectories for eight commonly used adapted switches were collected and compared to clinicians' subjective evaluation of the same characteristics. The major finding was that although therapists' subjective estimates of activation force and displacement were reasonably good there were specific areas of weakness that should be rectified with quantitative, objective data. It is anticipated that these two papers will enhance the application of microcomputer usage for physically disabled individuals.

Purpose. The objective of this thesis was to examine work in mines. Specifically, part #1 performed in-situ time/motion analyses of common mining jobs and part #2 analyzed in-situ energy expenditures while working in a mine. Methodology. Part #1- task and sub-task duration and subjective work intensity were investigated for thirty eight subjects from six different mining jobs. These jobs were then organized into 4 groups for statistical analysis based on precedence: Group 1 (Bolting & Screening (attaching steel mesh to walls and ceiling), Group 2 (Conventional Mining (using a hand-held drilling carriage to drills holes in rock walls and ceiling)), Group 3 (Support Services (mechanic, welder, pipe layer)), Group 4 (Production Drill (using a machine mounted drilling unit), Scooptram(TM) (ore transport with no air conditioner), Shotcrete (concrete applied by spraying)). Part #2- In-situ metabolic energy expenditures were estimated through indirect open circuit calorimetry and deep tissue and skin temperatures were measured for those same groups. Results. Part #1- twenty three common mining tasks were identified with differences identified between various group for time and intensity. Part #2- metabolic requirements between groups were similar with one difference identified between groups 3 and 4 (P &lt; 0.05). Deep tissue and skin temperatures did not change significantly through the course of a work day. Conclusion. Part #1- a variety of tasks is performed by each group and there is no uniform work protocol. Part #2- each mining group's metabolic energy expenditure requirements to perform various mining tasks are similar.

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