Objectif Estimer les associations entre les expositions professionnelles aux fibres/poussières textiles et le risque de cancer du sein post-ménopausique. Méthodes Une étude cas-témoins populationnelle menée à Montréal (20082011) a identifié les cas incidents (N=695) dans les hôpitaux et les témoins (appariés par groupe d’âge) sur la liste électorale provinciale (N=608). Les renseignements sur leurs facteurs de risque personnels et leurs antécédents professionnels ont été recueillis lors d’entrevues. Des hygiénistes du travail ont évalué ces antécédents afin d’attribuer des expositions professionnelles à plusieurs fibres naturelles et synthétiques. Les indices d'exposition calculés comprenaient: toute exposition antérieure (exposée/non-exposée), intensité cumulative moyenne d’exposition et exposition cumulative moyenne. Pour l’ensemble des tumeurs et selon leur classification biomoléculaire, une régression logistique a été utilisée pour calculer les rapports de cotes (RC) et les intervalles de confiance à 95% (IC95%), avec différents modèles incluant divers facteurs de confusion. Des analyses de sensibilité ont permis d’évaluer la robustesse des estimations. Résultats Une association a été trouvée pour toute exposition antérieure au polyester (RCmodèle8=0,55; IC95%:0,33-0,91). Quelques tendances ont été trouvées pour le même indice d’exposition avec les fibres synthétiques (RCmodèle8=0,63; IC95%:0,38-1,05) et le coton (RCmodèle8=1,42; IC95%:0,95-2,16), et, dans une analyse de sensibilité n’incluant que les expositions avant l'âge de 36 ans ou la première grossesse à terme, avec les fibres naturelles (RCmodèle8=1,59; IC95%:0,95-2,74) et les fibres traitées (RCmodèle2=1,39; IC95%:0,97-2,01). L’analyse par sous-type biomoléculaire n’a révélé aucune tendance. Conclusion Notre étude suggère la possibilité d’associations entre l’exposition professionnelle à certaines fibres textiles et le risque de cancer du sein post-ménopausique. / Objective To estimate the associations between occupational exposures to textile fibers/dusts, and postmenopausal breast cancer risk. Methods A population-based case-control study conducted in Montreal (20082011) identified incident cases (N = 695) in hospitals and frequency age-matched controls from the provincial electoral list (N = 608). Information on subjects’ personal risk factors and occupational history were collected through interviews. Occupational hygienists assessed these histories to attribute occupational exposures to several natural and synthetic fibers. Exposure indices included: any previous exposure (exposed/unexposed), average cumulative intensity of exposure and average cumulative exposure, among others. For all tumors and according to their biomolecular classification, logistic regression was used to calculate odds ratios (OR) and 95% confidence intervals (95%CI), with different models including various confounders. Sensitivity analyses were used to assess the robustness of the estimates. Results An association was found for any previous exposure to polyester (ORmodel8=0.55; 95%CI: 0.33-0.91). Some trends were found for the same exposure index with synthetic fibers (ORmodel8=0.63; 95%CI: 0.38-1.05) and cotton (ORmodel8=1.42, 95%CI: 0.95-2.16), and, in the sensitivity analysis including only exposures before the age of 36 or before the first full-term pregnancy, with natural fibers (ORmodel8=1.59; 95%CI: 0.95-2.74) and treated textile fibers (ORmodel2=1.39; 95%CI: 0.97-2.01). Analysis by tumor biomolecular subtype revealed no differences. Conclusion Our study suggests possible associations between occupational exposure to certain textile fibers and postmenopausal breast cancer risk.

<p>  </p> <p>Globally, communities are embracing the cured-in-place-pipe (CIPP) process due to the need to address damaged buried water and sewer pipes. CIPP involves the chemical manufacture of a new plastic pipe inside an existing buried water and sewer pipe, without the need for excavation. The process is popular because it can be 80% less costly than alternative methods and construction workers can be present for hours to not days to weeks. However, as CIPP use has grown, so have the number of hazardous material (HAZMAT) incidents caused by using this practice. Evacuations of daycare centers, schools, homes, healthcare, institutional, and other buildings have been caused. In some cases, chemical exposure victims have required medical assistance and hospital admission. For decades, organizations within the CIPP industry and municipalities have encouraged chemical waste discharge into ambient air, resulting in preventable exposures. Recent work has indicated tons of volatile organic compounds (VOC) may be released during a single CIPP project into the air. Chemicals released include hazardous air pollutants (HAP), carcinogens (CAR), endocrine disrupting chemicals (EDR), and other compounds with little toxicological information. While polymer composites have been manufactured for other applications for more than 50 years, little information exists about what chemicals and materials are used to manufacture CIPPs. As CIPP use has grown along with the number of bystander chemical exposures, concerns about the type, magnitude, and toxicity of chemical emissions from CIPP projects have markedly increased. To reduce the potential for human harm and environmental degradation, a better understanding of CIPP composite chemistry and manufacturing is needed. This dissertation aimed to elucidate the processes that control the composition of waste generated during plastic CIPP manufacture and ascertain how to modify the manufacturing practice to minimize impacts on composite integrity and emission toxicity. </p> <p>Chapter 1 focused on indoor VOC exposure simulation and styrene contamination/ decontamination to evaluate the risk of occupant exposure during CIPP installation. Styrene is a common monomer used in many CIPP resins and can be discharged into the air at CIPP worksites. A review of prior incidents revealed that CIPP waste (liquid, organic chemicals, etc.) could enter nearby buildings through multiple routes including windows, doors, or heating, ventilation, and air conditioning outdoor air intakes. When CIPP is manufactured inside a sanitary sewer pipe, waste can enter buildings through sewer laterals of nearby buildings and through foundation cracks. Study results showed that plumbing seal backflows in bathrooms caused by sewer repair work are hydraulically possible: the minimum pressure required to displace water in the plumbing trap was estimated to be 0.995 kPa and 8.85 kPa for a sink and toilet, separately. These pressures are much lower than those applied by the contractor during the sewer lining (up to 193.05 kPa). Based on the indoor exposure events, the dissipation potential of vapors, as well as the hydraulic calculations, indoor air chemical contamination and decontamination profiles were also examined. A mass balance model of chemical vapor dispersion was developed. Modeling results revealed that bathroom exhaust fan operation during a CIPP project can increase the indoor styrene concentration by enhancing the inflow of styrene-containing air from the sink and toilet. However, the styrene concentration decreased as air leaked across the bathroom door due to reduced suction in the plumbing. Based on incident reviews, chemical magnitudes, and modeling results it was concluded that CIPP waste discharge should be treated as hazardous material discharge, because of its threat to human health. Actions are needed to reduce waste generation and contain the waste, so it does not leave the worksite. Chapter 2 aimed to determine the manufacturing conditions that most influence chemical residual left in the thermally manufactured CIPP. Bench-scale testing of multiple styrene- and non-styrene composites revealed the manufacturing conditions (curing time, temperature, initiator loading) necessary to produce a high integrity composite while minimizing chemical residual and air emissions. Even though the VOC loading of the non-styrene resin (4 wt.%) was much less than that of styrene resin (39 wt.%), the non-styrene resin did contain HAP, EDR, CAR compounds including ethylbenzene, 2-ethylhexanoic acid, methacrylic acid, styrene, toluene, and <em>m</em>-xylene. Study results also revealed that by changing initiator loading a drastic reduction in the amount of styrene (-42 wt.%) and styrene oxide (-33 wt.%) residual left in the newly manufactured composite was achieved. Discoveries prompted a new hypothesis that this decreased residual also prompted a decreased amount of VOCs emitted into the air. The explanation is that this occurs because that a greater amount of the monomer styrene was incorporated into the resin during polymerization and not permitted to enter the air. Despite decades of polymer composite use, this study provides a new fundamental understanding of composite chemicals and techniques for reducing air pollutant emissions during plastic composite manufacture. In Chapter 3, the complexity of organic vapor chemicals found in the air during thermal heating of CIPP composites was explored and quantified. The emission rate of a popular monomer, styrene, was quantified from the materials before, during, and after composite manufacture. Scaling up bench-scale results, 1.9 to 14 US tons and 0.18 to 1.35 US tons of VOCs (0.05 to 0.36 US tons and 0.001 to 0.007 US tons of styrene) were estimated to be emitted during curing of styrene- and non-styrene CIPPs (i.e., typically 1-3 m of diameter pipes). By modifying standard air sampling methods, previously undetectable chemicals associated with CIPP manufacture were found in the styrene-laden air. These include acetophenone, benzaldehyde, phenol, and 1,3,5-trimethylbenzene. Results have immediate relevance to improved air monitoring for public and worker safety. Further, results can be used to examine the cumulative health and environmental risks of the CIPP pollutant mixtures. Chapter 4 focused on identifying CIPP technology/knowledge gaps and feedback from health officials from multiple state and federal agencies. Through this study, a public health workgroup was assembled to include disciplinary experts and 13 federal, state, and city health agencies and public health associations. Building on dialogue with U.S. health officials, the state of knowledge pertaining to CIPP chemical exposures, mitigation, and response actions was reviewed. Topics included 1) CIPP manufacturing process and waste; 2) sewers and buildings; 3) chemical exposure and health; 4) chemical risk assessment; 5) risk communication. This study helped establish relationships among federal, state, and city officials to improve public health response. Additionally, a primer for CIPP chemical fate and transport, as well as assisting in identifying and prioritizing public health information needs was developed. Identification and prioritization of current public health knowledge gaps and proposed practices for reducing exposures to the public and workers were reported. CIPP-related bench and research results throughout the dissertation can serve as an important basis for environmental policy and public health guidelines on the prevention and mitigation aspects of environmental and human health impacts resulting from CIPP manufacturing practices.</p>

L'association entre le tabac et le cancer du poumon ou entre l'exposition professionnelle à l'amiante et le mésothéliome pleural ont largement été étudiées. Cependant, comme pour de nombreuses autres relations expositions prolongées-cancer, le rôle de l'intensité d'exposition tout au long de la vie a été peu étudié. La prise en compte de la variation de l'intensité au cours de la vie et de son effet dépendant du temps dans les analyses statistiques des données cas-témoins pose en effet quelques défis méthodologiques. Les objectifs de la thèse étaient 1) d'étudier l'effet dépendant du temps de l'intensité d'exposition au cours de la vie sur le risque de cancer et 2) d'identifier les profils de trajectoires d'intensité d'exposition sur la vie entière et comparer les risques de cancer associés. Pour répondre à ces deux objectifs, nous avons utilisé un indice cumulé d'exposition pondéré flexible déjà existant et nous avons développé un nouveau modèle conjoint à classes latentes, pour analyser les données de deux études cas-témoins françaises sur le mésothéliome pleural et le cancer du poumon. Les résultats montrent la contribution importante de l'intensité de la consommation de tabac récente pour le cancer du poumon et des expositions professionnelles anciennes à l'amiante pour les deux cancers. Ils confirment l'importance de considérer l'aspect temporel des expositions pour évaluer l'association avec le risque de cancer et illustrent l'intérêt des approches statistiques considérées. / The association between smoking and lung cancer or between occupational exposure to asbestos and pleural mesothelioma have been extensively investigated. Nevertheless, as for many protracted exposures-cancer relationships, the role of exposure intensity over lifetime has been rarely addressed. Accounting for individual variation of intensity over lifetime and investigating time-dependent effect in the statistical analysis of case-control data indeed raise several methodological issues. The thesis objectives were 1) to study the time-dependent effect of exposure intensity over lifetime on the risk of cancer and 2) to identify lifetime profiles of exposure intensities and to compare their associated risks of cancer. To address these objectives, we used an existing flexible weighted cumulative index of exposure and we developed a new joint latent class mixed model, to analyze the data from two French case-control studies on lung cancer and pleural mesothelioma. The results show the important contribution of recent smoking intensity for lung cancer and distant intensity of exposure to asbestos for both cancers. They confirm the importance of the timing of exposure in the association with the risk of cancer and illustrate the relevance of the proposed statistical approaches.

L’ampleur des problèmes de santé mentale, les coûts qui en découlent et le lien établi entre le travail et les problèmes de santé mentale sont autant d’éléments qui expliquent l’intérêt croissant pour les interventions en santé mentale au travail. Dans un contexte où la personnalisation des interventions en santé mentale est davantage encouragée, les traits d’identité culturelle pourraient contribuer à une telle personnalisation. Nous définissons un trait d’identité culturelle comme un élément matériel ou non matériel d'une identité culturelle, hérité ou non héritée, considéré comme isolable et susceptible d'une analyse spécifique. Personnaliser les interventions en santé mentale suivant les traits d’identité culturelle implique d’adapter ces interventions, de manière à répondre aux situations spécifiques en milieu de travail dans lesquelles les traits d’identité culturelle pourraient agir comme des facteurs importants. Cette thèse de doctorat est un début de réponse sur l’intérêt ou non d’une telle démarche. Cette thèse vise à mieux comprendre en quoi les traits d’identité culturelle, plus particulièrement l’ethnicité et le statut d’immigrant, pourraient modifier la façon dont le travail s’associe aux symptômes de détresse psychologique et aux symptômes dépressifs dans la main-d’œuvre canadienne. La place limitée réservée aux traits d’identité culturelle dans les modèles dominants du stress au travail représente un obstacle à la compréhension du rôle des traits d’identité culturelle dans l’association qui relie le travail aux problèmes de santé mentale. Or les traits d’identité culturelle sont à la fois associés au travail et à la santé mentale. La composition de la population canadienne justifie toute aussi la pertinence d’intégrer les traits d’identité culturelle dans l’analyse du travail et de la santé mentale, car un peu plus de 250 000 nouveaux immigrants entrent sur le territoire canadien chaque année. Parmi ceux-ci, environ 80% proviennent d'Asie, d’Afrique, et d’Amérique latine. Or les immigrants et les personnes issues des minorités visibles semblent plus à risques de se retrouver dans des conditions de travail plus contraignantes. Ces deux groupes semblent également avoir en général une prévalence de symptômes de détresse psychologique et de dépression élevée. Afin de contourner les limites inhérentes aux modèles dominants du stress au travail, nous avons pris appui dans cette étude sur le modèle multiniveaux du stress au travail inspiré de la théorie du stress social; et des approches sociologiques abordées aux États-Unis dans une perspective micro-macro et en Europe dans une perspective d’agent-structure. La théorie du stress social permet de comprendre les mécanismes qui lient certaines conditions de l’organisation sociale à la santé mentale. Les approches micro-macro et d’agent structure s’intéressent non seulement à scinder la réalité sociale en niveaux, mais essayent également de comprendre le sens de la relation entre les différents niveaux. Le modèle théorique proposé présente trois principales hypothèses dans lesquelles les variables du travail à l’exception de la déqualification sont inspirées de celles retrouvées dans le modèle multiniveaux. Ces hypothèses postulent 1) une relation directe entre les traits d’identité culturelle (le statut d’immigrant et l’ethnicité) et les problèmes de santé mentale (symptômes de détresse psychologique et symptômes dépressifs); 2) un rôle modérateur des traits d’identité culturelle entre les facteurs du travail (déqualification, utilisation des compétences, autorité décisionnelle, demandes psychologiques, demandes physiques, soutien social au travail, insécurité d'emploi, heures travaillées, horaire irrégulier) et les problèmes de santé mentale; 3) un rôle médiateur des facteurs du travail dans la relation entre les traits d’identité culturelle et les problèmes de santé mentale. Grâce à l’analyse de médiation, nous avons également testé la possibilité d’une exposition différentielle aux facteurs du travail selon les traits d’identité culturelle. Nous avons utilisé les données longitudinales de l’Enquête nationale sur la santé de la population (ENSP) menée par Statistique Canada. Les données ont été collectées sur une période de 18 ans, débutée en 1994 et terminée en 2012 après 9 cycles. Des analyses de régressions multiples et multiniveaux ont été menées sur un échantillon de 6 477 travailleurs. Les résultats des analyses sont présentés sous forme de trois articles retrouvés aux chapitres 5 à 7. Les résultats suggèrent un rôle de l’ethnicité dans la relation entre le travail et les symptômes analysés. En effet, l’ethnicité semble s’associer aux symptômes dépressifs, mais pas aux symptômes de détresse psychologique. Des multiples effets de modération et de médiation testés, seul un effet s’est avéré significatif. Il s’agit du rôle médiateur de l’utilisation des compétences dans la relation entre l’ethnicité et les symptômes de détresse psychologique. Il semble également exister certaines expositions différentielles au travail de par l’ethnicité. Les personnes issues des minorités visibles semblent exposées de manière différentielle à plus de déqualification, à moins d’utilisation des compétences, et à moins d’autorité décisionnelle en comparaison à celles qui sont caucasiennes. L’analyse du rôle du statut d’immigrant dans la relation entre le travail et les symptômes analysés s’est avérée non concluante. De nombreuses limites inhérentes à notre stratégie de recherche (mesure de l’ethnicité, non prise en compte de la qualité de l’emploi, non-distinction des catégories d’immigrants, immigrants en majorité de longue date, variables de contrôle ne témoignant pas de nombreuses réalités du processus migratoire et d’intégration, etc.) appel à être prudent quant à l’interprétation faite des résultats de cette thèse. Les résultats de cette thèse ne permettent pas de mettre un point final sur la question du lien entre les traits d’identités culturelles, le travail et la santé mentale. Toutefois, ils y apportent un certain éclairage. Ils laissent penser que réduire les conditions de travail à risque et combattre l’exposition différentielle aux facteurs du travail pourraient offrir deux axes d’interventions contre les problèmes de santé mentale dans la main-d’œuvre canadienne. Intervenir sur ces deux pôles pourrait également contribuer à baisser les dépenses en santé mentale qui semblent de plus en plus importantes au Canada. Un élément qui semble ressortir le plus de cette étude est bien la nécessité de se pencher davantage sur la question de la déqualification professionnelle. / The increased disability claims linked to mental health problems, the economic implications of mental illness in terms of costs for businesses, and the established link between work and mental health are some of the rising concerns explaining the growing interest in mental health interventions and programs in the workplace. In a context where the personalization of mental health interventions is further promoted, cultural identity traits could contribute to such a personalization. We define cultural identity traits as a tangible or intangible element of a cultural identity, inherited or not, considered as isolable and that could be subject of a specific analysis. To personalize mental health interventions according to cultural identity traits, it would require adapting these interventions to meet specific workplace situations in which cultural identity traits may act as important factors. This thesis is the beginning of an answer on whether such an approach is worth of interest. This thesis examines how cultural identity traits, such as ethnicity and immigration status, affect how work is related to mental health symptoms such as psychological distress symptoms and depressive symptoms in the Canadian workforce. The limited attention paid to cultural identity traits by current models to analyze work stress, prevents a better understanding of the cultural identity traits role in the association linking work to mental health issues, while they are associated with both work and mental health. The composition of the Canadian population justifies the relevance of including cultural identity traits into a comprehensive analysis of work and mental health, as over 250 000 newcomers settle in Canada every year, with approximately 80% coming from Asia, Africa, and Latin America. Studies show that immigrants and those identified as visible minorities are more likely to end up in jobs where the working conditions are much more difficult. These two groups appear to have a higher prevalence of psychological distress symptoms and depressive symptoms. In order to address the inherent limits of the current theoretical models explaining work stress in the literature, we use in this study a multilevel analysis approach of work stress inspired by the social stress theory, and sociological approaches discussed in the United States from a micro–macro perspective, and in Europe from an agency-structure perspective. Social stress theory allows us to understand the mechanisms linking some conditions of social organization to mental health. Micro-macro and agency-structure approaches are not only concerned with dividing social reality into levels, but also try to understand the direction between levels. Our theoretical model examines three main hypotheses in which work factors with the exception of overqualification are inspired by those found in the multilevel model: 1) a direct relationship between cultural identity traits (immigrant status and ethnicity) and mental health problems (psychological distress symptoms and depressive symptoms); 2) a moderating effect of cultural identity traits on the relation between work factors (overqualification, skill utilization, decision latitude, psychological demands, physical demands, social support at work, job insecurity, worked hours, irregular work scheduling) and mental health problems; 3) a mediating role of work factors on the relation between cultural identity trait and mental health problems. The mediating effect allows us to analyze if a differential exposure to work factors based on ethnicity and immigrant status exist. The data for this study were collected from the nine cycles of the National Population Health Survey (NPHS) conducted by Statistics Canada over an 18-year period starting from 1994 and ending in 2012 after 9 cycles. Multilevel regression analyses were conducted on a sample of 6477 workers. The results of the analysis are presented in three articles representing the chapters 5 to 7 of this thesis. Results suggest that ethnicity seems to influence the relationship between work and the two analyzed symptoms. Ethnicity (visible minority versus caucasian) seems to be associated with depressive symptoms, but not with psychological distress symptoms. Among the effects of moderating variables and the effects of mediating variables tested, only one variable is proven significant. The skill utilization plays a mediating role in the relationship between ethnicity and psychological distress symptoms. There seems to be a differential exposure to work factors based on ethnicity. Compared to caucasians, visible minorities are more exposed to overqualification and less to skill utilization and decision latitude. All analyses conducted with immigration status have led to inconclusive results. Many limitations related to our research strategy (measurement of ethnicity, job quality is not taken into account, immigrant categories are not distinguished, mostly long-term immigrants, confounding variables not reflecting many realities face by the migration and integration process, etc.) call to be caution when interpreting the results of this thesis. The results of this thesis do not close debates on how cultural identity traits, such as ethnicity and immigration status affect the way work is related to mental health symptoms. However, they provide some insights into it. The results suggest that reducing risky working conditions and tackling differential exposure to work factors might provide two avenues for action against mental health problems in the Canadian workforce. Taking tangible steps on these two directions could also help lower cost related to mental health issues, which are continuously growing in Canada. One element that seems to stand out the most from this study is the need to look more closely at the issue of professional deskilling.

<p>Surface electromyography (sEMG) has been used to monitor muscle activity and predict fatigue in the workplaces. However, objectively measuring fatigue is challenging in complex work with unpredictable work cycles, where sEMG may be influenced by the dynamically changing posture demands. The sEMG is affected by various variables and substantial change in mean power frequencies (MPF), and a decline over 8-9% is primarily considered musculoskeletal fatigue. These MPF thresholds have been frequently used, and there were limited efforts to test their appropriateness in determining musculoskeletal fatigue in live workplaces (which predominantly consist of complex tasks). In addition, the techniques that consider both muscular and postural measurements that incorporate dynamic posture changes observed in complex work have not yet been explored. The overall objective of this work is to leverage both postural and muscular cues to identify musculoskeletal fatigue in complex tasks/jobs (i.e., tasks involving different levels of exertions, durations, and postures). The work was completed in two studies.</p> The first study aimed to (1) predict subjective fatigue using objective measurements in non-repetitive tasks, (2) determine whether the musculoskeletal fatigue thresholds in non-repetitive tasks differed from the previously reported threshold, and (3) utilize the empirically calculated thresholds to test their appropriateness in determining musculoskeletal fatigue in live surgical workplaces. The findings showed that the multi-modal measurements indicate better sensitivity than single-modality (sEMG) measurements in detecting decreases in MPF, a predictor of fatigue. In addition, the results showed that the thresholds in dynamic non-repetitive tasks, like surgery, are different than the previously reported 8% threshold. Additionally, implementing muscle-specific thresholds increased the likelihood of more accurately reporting subjective fatigue. The second study aimed to develop a multi-modal fatigue index to detect musculoskeletal fatigue. A controlled laboratory study was performed to simulate the non-repetitive physical demands at different postures. A series of experiments were conducted to test the effectiveness of various metrics/models to identify subjective fatigue in complex tasks. Next, the composite fatigue index (CFI) function was developed using the time-synced integration of both muscular signals (measured with sEMG sensors) and postural signals (measured with Inertial Measurement Unit (IMU) sensors). The variables from sEMG (amplitude, frequency, and the number of muscles showing signs of fatigue) and IMU (the prevalence of static and demanding postures and the number of shoulders in static/demanding posture) sensors were integrated to generate the CFI function. The prevalence of static/demanding postures was developed using the cumulative exposures to static/demanding postures based on the material fatigue failure theory. The single value fatigue index was obtained using the resultant CFI function, which incorporates both muscular and postural variables, to quantify the muscular fatigue in dynamic non-repetitive tasks. The findings suggested that the propagation of musculoskeletal fatigue can be detected using the multi-modal composite fatigue index in complex tasks. The resultant CFI function was then applied to surgery tasks to differentiate the fatigued and non-fatigued groups. The findings showed that the multi-modal fatigue assessment techniques could be utilized to incorporate the muscular and postural measurements to identify fatigue in complex tasks beyond single-modality assessment approaches.