309 cases of organic dementia, cerebral atrophy or psycho-organic syndrome, admitted for 5 days or more to one of 18 Quebec hospitals, were individually matched to a psychiatric referent, admitted with some other diagnosis, and a general hospital referent. Lifetime occupational history was obtained by telephone. Occupational solvent exposure was assessed by (i) individual ratings blind to case status and (ii) a job-exposure matrix. Subjects working with moderate or high solvent concentrations for at least 10 years were considered exposed. With the psychiatric referent series an odds ratio of 1.44 (90% CI 1.03-2.01) was calculated for individual exposure ratings and 1.41 (90% CI 0.89-2.23) for the job matrix. The increased risk was found largely in those with diagnoses of both organic dementia or cerebral atrophy and an alcohol related condition. A similar pattern of risk was found with the general hospital referents. Adjustment for possible confounders did not appreciably alter the risk estimates.

Through the study of the effects of Virtual Reality (VR) on human subjects, scientists have determined that the main cause of discomfort while experiencing VR is the time lag between the head movements and its corresponding scene changes. / The main purpose of this thesis is to study and to propose solutions to reduce VR effects. The proposed solution is an alternative controller based on a Proportional Derivative (PD) model. Compared with a simple Proportional Controller, the PD Controller offers several enhancements: namely, a larger bandwidth and a faster and more stable reaction time. The proposed controller will also reduce the physical side effects commonly experienced by users of Virtual Reality.

The soleus H-reflex modulation pattern was measured in 8 normal and 8 spastic paretic subjects during standing and walking, under the conditions of 0% and 40% body weight support (BWS). In standing, both the normal and patient groups showed no significant difference (p $<$ 0.01) in the H-reflex amplitude between 0% and 40% BWS. Normal subjects had a phase dependent modulation of the H-reflex during gait, there being no significant difference (p $<$ 0.001) in this modulation with 40% BWS. The patients had an abnormally elevated H-reflex throughout the step cycle, although five showed some modulation. In the patient group, 40% BWS produced a decrease of the H-reflex amplitude mainly in the push-off phase. BWS produced a decrease in electromyographic (EMG) mean burst amplitude of the lower limb muscles investigated, with more appropriate EMG activity timing. BWS improved knee and ankle angular displacements in patients, which were associated with an improved locomotor pattern. However, these improvements in locomotor pattern were not reflected clearly by changes in the H-reflex modulations. Thus the relationship between H-reflex amplitude, EMG activity, and ankle position under 0% and 40% BWS, needs to be further investigated.

Renal cell carcinoma, which accounts for 85% of all kidney cancers, is among the ten leading malignancies in industrialized countries. To identify occupational risk factors for cancer, a multi-site case-control study was conducted in Montreal; renal cell carcinoma was one of the sites. A total of 142 cases of renal cell cancer and 2,433 controls were interviewed in this study. Complete occupation histories were obtained, and a team of industrial hygienists and chemists estimated each subject's exposure to a list of industrial substances. Statistical analyses were carried out to estimate the association between renal cell cancer and each non-occupational and occupational variable. Among non-occupational variables collected and analysed, increased risks were observed for highest level of body mass index (BMI) and a previous history of hypertension. Negative associations were found for tea and coffee consumption. Increased risks were found in the following industries: printing related service, laundries, military, wholesale and retail trade industries. Increased risks were found in the following occupations: managers, plumbers, welders, printers, nursery workers, and aircraft mechanics. Exposure to the following substances significantly increased the risks for renal cell carcinoma: hair dust, felt dust, styrene-butadiene rubber, ozone, hydrogen sulphide, inorganic acid solution, nitric acid, phosphoric acid, jet fuel, aviation gasoline, jet fuel engine emissions, ink, chromium compounds, and ultraviolet radiation. The above findings were not adjusted for mutual confounding. After adjustment for known risk factors using multivariate logistic regression models, one non-occupational and several occupational risk factors were associated with renal cell carcinoma. These were: high BMI, asbestos, hair dust, felt dust, styrene-butadiene rubber, ozone, exposed to any of jet fuel, aviation gasoline, and jet fuel engine emission, nitric acid, phosphoric acid, and ultraviolet

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.

<p> In the spring of 2012, based on recommendations from the International Commission on Radiological Protection (ICRP), the Nuclear Regulatory Commission (NRC) proposed three amendments to reduce current radiation exposure limits for radiation workers. The NRC proposals have caused some concern within the radiopharmaceutical industry. The regulatory changes may affect the ability of radiopharmacy workers to remain on the job, thereby inflicting additional costs to radiopharmacies if they are required to replace workers who have reached their yearly exposure limits. </p><p> This research sought to determine whether or not the new regulatory proposals will in fact have a financial impact on the radiopharmaceutical industry. This research was a retrospective case study that analyzed four radiopharmaceutical production facilities and their employee radiation exposure reports. Results of the study suggest that the NRC's proposed amendments to reduce radiation levels will not have a great adverse effect, either financially or from an employee exposure standpoint, on the current radiopharmacy system. The research demonstrated that existing as low as reasonably achievable (ALARA) standards have resulted in radiopharmacy workers receiving exposures well below the current limits, and within the NRC proposed limits. Of 77 employees studied over a 10 year period, only seven employees (9 %) would have been removed from the production process for overexposure to any one of the NRC's proposed limits. However, this research reviewed small a subset of four radiopharmacies and did not examine other industries and professions utilizing ionizing radiation.</p>

<p>U.S. Army Regulations require soldiers to be fit, as excessive weight negatively impacts their readiness, health, and morale. A quantitative study examined if personal, behavioral, and/or environmental factors predict a soldier&rsquo;s self-efficacy and body mass index. Data were obtained from 117 soldiers on 6 scales: the Armed Services Vocational Aptitude Battery, the Army Physical Fitness Test, the General Self-Efficacy Scale, the Stress Management Questionnaire, the Lifestyle Assessment Inventory, and the Multifactor Leadership Questionnaire. Multiple regression analysis was used to determine if personal (intellectual capabilities and physical fitness), behavioral (lifestyle and stress management), and/or environmental (supervisor leadership) factors predict self-efficacy and body mass index in a convenience sample of battalion personnel. The analysis showed that lifestyle and stress management behavioral factors predict self-efficacy, whereas physical fitness predicts body mass index. In addition, there were significant correlations between self-efficacy, personal factors, and behavioral factors; between personal factors, behavioral factors, and body mass index; and between behavioral and environmental factors. Positive social change implications include the U.S. Army using these findings to promote healthy lifestyles, reduce stress, and increase physical fitness among soldiers to achieve higher self-efficacy and a lower body mass index. These findings also suggest that the military services would see better physical readiness by considering personal, behavioral, and environmental factors to meet standards. </p>

<p> Heat stress due to ambient outdoor temperatures is a workplace hazard that has not been well studied or characterized. The incidence of occupational heat-related illness is unknown. Heat-related morbidity and mortality have been well-studied at the population level, however it cannot be determined if these findings extend systematically to workers exposed to high heat conditions. Remarkably, there is no U.S. federal standard to protect workers from the peril of elevated environmental temperatures and few states have protective regulations. This dissertation research will add to the limited knowledge base of occupational heat-related illnesses, by characterizing worker fatalities due to environmental heat stress. Three independent, but related, research strategies were designed, executed, and completed to evaluate the current research, as well as knowledge gaps, and to thoroughly describe these fatalities based on available information. </p><p> This work was initiated with a thorough literature review to summarize research findings that characterize U.S. occupational heat-related morbidity and mortality and identify gaps in the existing research literature. This review of science, health, and medical databases found that few studies examine ambient heat stress or characterize the incidence of occupational heat-related illnesses and outcomes. Significantly more research examining the heterogeneity of worker and environmental risk factors to heat exposure is needed to identify unsafe working conditions and implement practical, evidence-based heat-stress policies and interventions. The subsequent study describes the epidemiological characteristics of heat-related deaths among workers in the U.S. from 2000 to 2010. Fatality data were obtained at the Bureau of Labor Statistics from the confidential on-site Census of Fatal Occupational Injuries database. Fatality rates and risk ratios with 95% confidence intervals were calculated by year, sex, age group, ethnicity, race, state, and industry. Between 2000 and 2010, 359 occupational heat-related deaths were identified in the U.S., for a yearly average fatality rate of 0.22 per 1 million workers. Highest rates were found among Hispanics, men, the agriculture and construction industries, the states of Mississippi and Arkansas, and very small establishments. This study provides the first comprehensive national profile of heat-related deaths in the U.S. workplace. Prevention efforts should be directed at small businesses, states, industries and individuals who may be at increased risk of heat stress. </p><p> Lastly, to further characterize these fatalities, research was performed to: 1) determine the ranges of heat index and temperature at which workers fatally succumb to environmental heat; 2) identify risk factors that may influence heat-related deaths; and 3) translate these findings to policy recommendations. The Census of Fatal Occupational Injuries and the National Climate Data Center were used to identify worker heat-related deaths in the U.S., 2000- 2010, and to assign a maximum daily temperature and heat index to each case. Demographic, meteorological, and geographical variables were analyzed to evaluate any differences in fatal heat exposure. The National Weather Service temperature alert tools, the Excessive Heat Event warning and the heat index category chart, were utilized to assess community threshold suitability for workers subjected to exertional heat stress. Of the 327 cases that qualified for the analysis, there were no differences found in mean temperatures and heat indexes between the sexes, races, age groups, ethnic groups, and industries. Southern workers died at significantly higher temperatures than workers in the North. This study supports the use of heat index and temperature as a guide when evaluating environmental conditions for workers. </p><p> Population-level heat index threshold alerts are unsuitable for preventing exertional heat stress and new warning systems should be developed. Since heat-related health hazards at work can be anticipated before they manifest, preventive measures can be implemented before illness occurs. With no federal regulatory standards to protect workers from environmental heat exposure, and with climate change as a driver for adaptation and prevention of heat disorders, it is increasing sensible and imperative for the Occupational Safety and Health Administration to take action. National leadership is needed to promulgate regulations, develop new heat alert tools using the heat index as a metric, and promote state-specific occupational heat stress prevention policies.</p>

There are limitations to conventional occupational health and safety research approaches and practices and numerous barriers to overcome in order to achieve progress. Occupational health and safety is impacted by the broader social-political environment. Corporatism affects the directions, ideas and practice of regulators, educators, the labour movement, scientists, medical professionals, and society as a whole, thus inhibiting workers' power to influence change. The thesis therefore explores both the wider influences and barriers to occupational health and safety advances, focusing particularly on the Canadian situation, through the general research questions: What has influenced occupational health and safety policies and practices, especially in Canada? What are some of the limitations of conventional occupational health and safety research and practices? To what extent can participatory action research and mapping address identified limitations? These questions are explored from the perspective of the population potentially at risk. New theories and approaches to occupational health and safety research are then applied in this thesis in order to explore a more specific multi-part research question: Can mapping within worker-based participatory action research be used to explore occupational health and safety conditions? In particular, can mapping contribute to occupational health and safety improvements at a local level and beyond; establish workers' previous exposures for compensation purposes; support efforts to bring about justice through compensation for workers affected by unsafe working conditions; and raise worker and public awareness of health and safety? These questions are explored through two different case studies, which examine, in depth, occupational health and safety action and possible remedies. Casino gaming workers in Windsor, Ontario, Canada undertook a collaborative study to investigate and improve current health and safety conditions. Former Holmes foundry and asbestos insulation workers in Sarnia, Ontario, Canada undertook a collaborative study to provide evidence of exposures and ensuing health problems to support claims for compensation. The outcomes of the case studies shed light on the bigger Canadian health and safety picture and demonstrate that mapping as a data collection method used within a participatory action research approach can accomplish a broad range of objectives. Mapping can raise workers' awareness, facilitate communication, build solidarity and cohesiveness, foster community support, mobilise workers to take action to reduce hazards or win compensation, in turn influencing employers, the compensation board and government agencies. The case studies accomplished the shared objective of raising worker and public awareness. The casino workers also gained occupational health and safety improvements and the Holmes workers were successful in gaining compensation.

The primary consequence of night shift work is a misalignment of the endogenous circadian pacemaker with the inverted sleep-wake cycle. This study evaluated the efficacy of a judicious schedule of light exposure on circadian adaptation to night work. Fifteen night shift workers (mean age +/-S.E.M.: 41.8 +/- 1.8 years) were studied for 3 weeks in their work environments under one of two experimental conditions. Treatment group participants underwent an intervention including bright light in the workplace, while control group participants were studied in their habitual light environments. The efficacy of the intervention was evaluated in the laboratory via constant routines. Following the intervention, treatment group subjects displayed a mean phase delay of (+/-S.E.M.) -9.32 +/- 1.06 hours and full entrainment to the night-oriented schedule while control group subjects displayed a phase delay -4.09 +/- 1.94 hours and a partial entrainment (F(1,30) = 11.33, p = 0.002). The results of this study suggest a means of alleviating the difficulties associated with night shift work with control of the overall pattern of light exposure.