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Background. Housekeeping is an important aspect of safety in the workplace. There have been only a limited number of studies assessing the impact on injury of housekeeping. In addition, measuring the state of housekeeping has posed continuous problems in these studies due to the lack of standardized and objective instrumentation. Objectives. The objectives of the first part of this thesis involved the development and evaluation of an instrument for measuring the state of housekeeping in industry. The second part examined the association between housekeeping and safety. Methods. This study began with the development of a checklist for evaluating housekeeping and proceeded to a fifteen-month prospective cohort study of fifty-seven companies in the transportation equipment and machinery manufacturing sector in Quebec, Canada, each employing between twenty and sixty workers. Companies were followed over 16 months to evaluate housekeeping levels. At the end of the study, information on compensable injuries that occurred during the study period was obtained. Results. Inter-observer reliability of the instrument was reasonably high (ICC 0.88, 95% CI 0.81--0.94) though test-retest reliability was less stable (ICC 0.73, 95% CI 0.68--0.78). In the second part of this study, housekeeping was found to be significantly associated with both injury rates (IRR 1.35, 95% CI 1.08--1.70) and rate of days lost (IRR 1.48, 95% CI 1.39--1.57), and trends were seen across categorical housekeeping levels. The association between cleanliness and safety was not as strong, nor was a trend found. Conclusions. The housekeeping checklist demonstrated high inter-observer reliability. The less stable test-retest reliability is partly due to changes in housekeeping between visits. Obstructions (lack of clutter, clear access to workstations, equipment and exits) and cleanliness components of housekeeping were more difficult, to measure and observers disagreed more when evaluating these components

This dissertaion comprises three related papers. / The first paper reports a historical cohort mortality study which was carried out among 21,744 electrical utility workers in the province of Quebec. A total of 1582 deaths were observed at the end of follow-up (1970-1988). A job exposure matrix (JEM) was used to estimate the exposure to 60 Hz electric, magnetic, and pulsed electromagnetic fields (PEMF) from the code of the last job held by each worker. The results showed no evidence of excess of cause specific or general mortality relative to provincial death rates in the cohort overall. The ratios of Standardized Mortality Ratios (SMRs) as estimates of rate ratio (RR) in the exposed relative to the background group were also calculated. Statistically significant RRs were found for pancreatic cancer for electric fields (RR = 2.8, 95% Confidence intervals (CI) 1.13-7.01) and for lung cancer for PEMF (RR = 1.56, 95% CI 1.05-2.25). Deaths caused by accidents and violence showed significant RRs for electric fields (RR = 2.16, 95% CI 1.59-2.92), magnetic fields (RR = 1.76, 95% 1.29-2.39) and for PEMF (RR = 1.96, 95% CI, 1.40-2.71). Occupational accidents related to power lines explain for some of the excess of deaths from accidents and violence. There was a small non-significant association with magnetic fields for leukaemia (RR = 1.52, 95% CI 0.45-4.47) and brain cancer (RR = 1.59, 95% CI 0.57-4.31), but the results for these two sites were based on small numbers. / The second paper reports a case-cohort study to investigate a previously suggested association between exposure to electric and magnetic fields and suicide. Forty-nine deaths from suicide between 1970 and 1988 were identified in the above-mentioned cohort and a sub-cohort comprising a one percent random sample was selected from it. Cumulative and current exposures to electric fields, magnetic fields and PEMF were estimated for the sub-cohort and cases through the JEM. For cumulative exposure, rate ratios (RR) for all three fields showed mostly small non-significant increases in the medium and high exposure groups. The most elevated risk was found in the medium exposure group for electric field-geometric mean (RR = 2.76, 95% CI 1.15-6.62). The results did not differ after adjusting for socioeconomic status (SES), alcohol use, marital status and mental disorders. There was little evidence for an association of risk with exposure immediately prior to the suicide. Small sample size (deaths from suicide) and inability to control for all potential confounding factors were the main limitations of this study. / The third paper reports a study of validity attributing magnetic field exposure by using a worker's last job. This was done by comparing, in a sample of the cohort, estimates obtained using last job with those obtained using full work histories. The correlation between indices based on last job and those based on all jobs varied between 0.75 and 0.78. The study showed that the last job was particularly good in identifying the highest exposed individual. The results are most likely to be generalizable to other industries in which highest exposed jobs are also skilled jobs.

The objective of this thesis was to investigate the contributions of both the vestibular and foot/ankle somatosensory inputs to the mechanisms controlling lower limb muscular activity of normal human subjects. The standing subject was modelled as a single-link inverted pendulum, producing whole head-body tilts about an axis colinear with the ankle joints. / A paradigm was developed whereby the vestibular and the ankle proprioceptive afferent systems were systematically and selectively controlled or eliminated. There was a greater tendency for reflex response to be activated in the three lower limb muscles when the forward tilts had an acceleration larger than 1.4 g. This was found when the whole head-body tilts were delivered with minimal changes in ankle angle or a significant change in ankle angle from the neutral position towards dorsiflexion. Frequency of occurrence was greater for the more proximal muscle when there was minimal ankle dorsiflexion, and for one of the distal muscles when there was ankle dorsiflexion. The proximal hip extensor muscle tended to have the shortest latency during whole head-body tilts alone, while the most distal muscles had the shortest latency when the tilts occurred concomitantly with ankle rotation.

This dissertation is a result of an epidemiological prospective cohort study carried out among apprentice welders at four vocational teaching institutions in welding profession in the Montreal region, for the purpose of: (1) assessing the respiratory health of students, before starting welding, such as respiratory symptoms suggestive of asthma, lung function and bronchial responsiveness as well as immunological sensitization to common allergens and to metals; (2) providing a reassessment of the respiratory health of these same students as well as an assessment of the incidence of systemic symptoms suggestive of metal fume fever (MFF) after being exposed to welding fumes; (3) estimating the association between MFF and the incidence of bronchial hyperresponsiveness (BHR) and/or the presence of welding-related respiratory symptoms suggestive of occupational asthma (OA); (4) determining whether atopy, immunological sensitization to metals encountered in the welding environment, smoking and a personal history of asthma, are associated with an increased level of BHR or welding-related respiratory symptoms suggestive of OA; and (5) determining the relationship between exposure to metal oxide fumes and the outcome variables, i.e., MFF, immunological sensitization to metals, welding-related respiratory symptoms suggestive of OA and BHR. / The undertaken study consisted of an initial pre-exposure assessment survey and two follow-up reassessment surveys that took place between September 1998 and June 2001. During these surveys a series of tests were carried out. These included a respiratory symptom questionnaire as well as a systemic symptom questionnaire, skin prick tests, spirometry and methacholine challenge tests. Industrial hygiene sampling for welding fumes in the breathing zone of these students was also performed. The overall results of the epidemiological study are presented in three interrelated manuscripts. / The first manuscript describes in detail the underlying methodology. In addition, it provides incidence figures, which are lacking in the reviewed literature, for the outcomes of interest described afterwards. The second manuscript determined the incidence of bronchial hyperresponsiveness (BHR) and the increase in airway obstruction from baseline values. The third manuscript confirmed our earlier findings (1) of a strong association between welding-related MFF and welding-related respiratory symptoms suggestive of OA. (Abstract shortened by UMI.)

A case-referent study was designed to investigate the relationship between occupational solvent exposure and mental disorders. New cases of mental disorder (males, 40 to 69 years old), were individually matched for age and date of admission to hospital patients and neighbors. An occupational history was obtained from 91.7% of the sample (1143 subjects, or 381 'trios'), during a telephone interview or by mail. / No increased risk of mental disorders was found among subjects exposed to moderate levels of solvents, but the risk was elevated--though not to a statistically significant degree--at exposure to high levels. When diagnoses were divided into psychotic (ICD-9 codes 290-299) and non-psychotic (ICD-9 codes 300-316), the latter group presented an increased risk with exposure to high levels of solvents (odds ratio = 2.43, 90% C.I. = 1.16-5.08). No systematic exposure-response relationship was demonstrated, although there was a suggestion of increased risk of mental disorders among subjects exposed to high levels for 5 to 9 years. / Various aspects of referent selection--with a specific comparison of hospital and population referents--were also examined as a methodological issue of case-referent studies.

Occupational histories collected during interviews in an epidemiological study and then expressed as types and levels of occupational exposure have been compared to the results acquired in a physico-chemical analysis of the particles extracted from pulmonary parenchyma of forty-two subjects with different types of cancer. The original scenario was for a group of workers, ten exposed mainly to asbestos fibers, ten to silica, ten to welding fumes, six smokers, and six nonsmokers not exposed to the target contaminants. Fragments of tissue that had been formolated or covered in paraffin were used after having been standardized by two pathologists. The preparation and analytical protocols were validated so that a representative number of particles could be counted and "reasonably" characterized from their morphology and their chemical composition by transmission electron microscopy and laser microprobe mass analyser. / A Kappa test revealed that there was a limited correlation at the 5% level of confidence between the work history history and physico-chemical estimators for the group of subjects exposed to asbestos fiber (k = 0.475, p = 0.001), a 10% level for the group with silica exposure (k = 0.213, p = 0.089) and at a 5% level in the unexposed nonsmoker group (k = 0.417, p = 0.003). The average pulmonary dust burden of the log-normalized values for certain minerals that were extracted from subjects belonging to certain groups of interest were statistically different.

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Shift work is a major feature of modern work practices. It involves individuals working at times considered unconventional for most workers, such as at night. Although the community often benefits from such work practices, shift work can be hazardous, for both the workers and the community. The thesis reviews the main problems of shift work, especially when involving night work. These are: an increased risk for accidents and errors; increased sleepiness and fatigue due to difficulties sleeping; increased health problems; and disruption to family and social life. Strategies to limit the risk associated with these hazards are also reviewed, and include using knowledge of circadian principles to plan shift schedules, sleeping schedules and meal times; planned napping; consideration of the work environment; and newer techniques such as using bright lights and melatonin. While this information is known to the research community, it has not filtered down to many shift work workplaces and thus has had little if any positive effect on actual shift work practices. For a change in shift work practices to occur, the research knowledge must become available to every shift work workplace, as must some incentive or motivation to ensure that workplaces make the necessary changes. The Occupational Health and Safety (OHS) laws provide such a framework. Considering shift work as an OHS hazard would ensure that all shift work workplaces identified the hazards of shift work, conducted a risk assessment to identify the risk associated with the hazards, and then implemented the appropriate strategies, from the hierarchy of shift work hazard control measures, for both employers and employees, to fulfil their duty of care to minimise the risks. Considering shift work as an OHS issue would ensure that the research information was used as intended – to improve the safety, performance, and quality of life of all shift workers. The present thesis reviews the shift work research and introduces an OHS perspective as a method to manage shift work effectively.

Statement of problem: Dynamic work environments and physically demanding jobs in the healthcare and commercial construction industries present workers with a constantly changing suite of hazards, and hence the changing need for controls. Workers in these industries experience high rates of MSDs and other illnesses and injuries. Hazard recognition and control are essential and inspections are essential elements used to identify and anticipate hazards and to implement corrective action as part of a systems-level approach to tackle the dynamic worksite. Methods: Because there is a dearth of practical resources for evaluating ergonomic risk factors in healthcare environments the first step in this dissertation was to explore the development of a tool and process for identifying modifiable aspects of acute care hospital patient care units to prevent work-related MSDs. To address a lack of systems-level approaches to worksite-based interventions in construction, an ergonomics program that relies heavily on inspections was developed and evaluated on five pairs of commercial construction sites. To examine associations between physical working conditions and safety climate, the relationship between weekly safety inspections and weekly safety climate scores was examined on six commercial construction sites. Results: The inspection process provided a structured method for recognizing hazards in dynamic and physically demanding work environments and reporting both observations and recommendations to decision makers. There were no significant intervention effects, however key challenges to intervention implementation were competing safety and production priorities and break practices leading to inconsistencies delivering the intervention and key resources to workers. Variations in week-to-week safety inspections were highly correlated with variations in week-to-week safety climate. Conclusions: Inspection tools and processes were useful in a systems-approach to workplace interventions in the dynamic industries of healthcare and commercial construction. Worksite-based ergonomics interventions focusing efforts on hazard identification, recommendations for solutions, and reinforcing both positive and negative feedback to safety management and workers can have a major impact on worker wellbeing. In addition, physical working conditions (as identified through weekly safety inspections) are an important aspect of the week to week changes of safety climate in the dynamic commercial construction environment.