In society, personal load carriage systems (backpacks) are commonly used to transport loads by foot, however, they have also been implicated in causing injuries. The aim of this study was to develop a model for load carriage which could be used to determine safety limits in humans. To start, a number of experiments were conducted to determine the appropriateness of using pressure mapping technology to measure peak and mean pressures acting on humans during load carriage limits. Tests of accuracy and repeatability were performed using three common pressure mapping technologies: capacitance, piezoresistive and resistive ink. Pressure mapping was tested statically and dynamically on a human-like flat surface, as well as on human shoulder-shaped model. Error was found to be ≥ 20% on static flat and curved surfaces and it rose to 36-51% under dynamic conditions. Since pressure mapping would require significant modifications before it could be used to study human load carriage, a psychophysical approach was used instead. For this approach, an epidemiological study of pain was conducted based on 48 subjects who used multiple backpack designs to complete occupationally relevant tasks. As a result, pain trends and new methods of data analysis were identified that had potential use on human trials. In a final study, pain mapping, quantification of pain intensity, and physiological/motor testing were conducted on humans performing endurance exercise with light to heavy payloads. Results showed that all subjects were able to exercise with a 15-35 kg payload for 45 minutes and with a 50 kg payload for 30 minutes, without stopping. As well, pain was found to be highest in the anterior acromial (shoulder) region, particularly for the 50 kg payload (mean peak pain = 3.4/10). Based on these findings, two models were proposed: an assertive model and a conservative model to allow prediction of human load carriage limits for endurance exercise. / Thesis (Ph.D, Rehabilitation Science) -- Queen's University, 2007-10-06 15:33:31.933

It is accepted that material handling is an activity presenting a high risk for injury, particularly to the back. In this study, an observation strategy has been developed and validated in order to evaluate the presence of these risky conditions while performing a handling task. Moreover, certain future utilisation conditions were specified. / Fifty-one observation variables were identified and an observation structure was elaborated from three data sources. These sources were: a literature review on observation grids, interviews with expert handlers and video sequences of a laboratory manual handling study where 10 inexperience subjects performed a total of 1500 container transfers. Observational data entry was recorded from a sample of these 174 sequences for which biomechanic measures were also done. / The results show that observations can be reliable and valid and that the diversity of observation objects can be important and extend beyond postural variables. The observations performed on an uninterrupted video sequence are the ones that present the most difficulties. The observers' experience does not seem to be an important factor in obtaining reliable results. On the other hand, the observation criteria, the training and the breakdown of variable classes are factors susceptible to influence reliability. / Many observation variables for balance had a significative impact on the biomechanical measure of balance, particularly when the object is taken and put down. This is the case with the number of foot supports, the weight distribution at the base of support and the position of the object, especially it's lateral deportation with respect to the body. The backward movement of the pelvis, which enables to compensate for the added external weight to the body, was significantly associated to balance. In general grouped variables, have more impact on the measure of balance than variables taken individually. Grouped variables are also less prone to variations when handling contexts are changed. For asymmetry, shoulder orientation with respect to the pelvis, back flexion, parallelism of the shoulders to the ground, and the position of the hands on the object handled all had a significative impact on the effort asymmetries when the object was taken from the plate-form. For the control and fluidity, a difficulty in finding a corresponding biomechanical measure or reliability problems did not enable us to verify whether our observations could have permitted to evaluate the risky conditions. (Abstract shortened by UMI.)

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.

A comparison was made between NIOSH-type, prepacked nutshell charcoal tubes and layers of commercial charcoal cloth in a stainless steel cassette designed for the active sampling/adsorption of different concentrations of a mixture of volatile organic chemicals (VOCs) (benzene, trichloroethylene, toluene, tetrachloroethylene, chlorobenzene and o-xylene). Physicochemical parameters of the charcoal cloth including breakthrough times and volumes and adsorption capacities were determined for toluene and the VOC mixture. The quantitative removal of VOCs from the charcoal cloth by solvent desorption, by supercritical fluid extraction (SFE), and by thermal desorption was studied prior to analysis by gas liquid chromatography with photoionization detection. Optimal conditions were explored both in laboratory and industrial environments. / Charcoal cloth was comparable to the NIOSH tube, adsorbed VOCs being quantitatively removed at any time up to 32 days after sampling. Although solvent (pentane, hexane) desorption yielded accurate, reproducible results with a high percent recovery of the VOCs, a major disadvantage was the irreparable damage done to the cloth, preventing its repeated use. Desorption by SFE proved unreliable for these low molecular weight VOCs, both the collecting solvents and the VOCs being lost during extraction. Thermal desorption proved to be efficient, sensitive and reliable, repeated heating having no effect on the adsorptive properties of the cloth. Charcoal cloth would appear to be a useful adsorbing medium for air sampling of both industrial and office building/home environments for either single chemicals or mixtures.

No description available.

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.

No description available.

No description available.