Canada fortifies certain products with folic acid and has periconceptional supplementation guidelines – policies designed to improve folate status and reduce the incidence of poor birth outcomes. Though optimal folate concentrations have been linked to health benefits, concerns have been raised regarding potential associations with adverse health outcomes. Direct biochemical assessment of the folate status of Canadians based on a nationally representative sample has not been done in more than 40 years. The overall purpose of this research was to investigate the folate status of the Canadian population. All analyses used the nationally representative 2007–2009 Canadian Health Measures Survey (CHMS). Red blood cell (RBC) folate was measured by Immulite 2000 immunoassay. Key findings indicate that folate deficiency (<305 nmol/L) was virtually non-existent in the Canadian population (6–79 years old). Still, one-fifth of women of childbearing age (WCBA; 15–45 years old) had sub-optimal concentrations for the prevention of neural tube defects (<906 nmol/L). Folic acid supplement intake was a primary determinant of WCBA achieving a RBC folate concentration ≥906 nmol/L. A distinct shift towards elevated RBC folate concentrations emerged. Three hypothetical cut-offs (1450 nmol/L, 1800 nmol/L and 2150 nmol/L) were examined to create dialogue since a universal definition of high RBC folate concentration does not exist. Females, participants aged 60¬–79 years, and those who were overweight or obese had the greatest prevalence of having high RBC folate at each cut-off. We conducted the first national-level comparison of RBC folate concentrations between the United States and Canada. Two different folate assay methods – microbiologic assay (NHANES) and Immulite 2000 immunoassay (CHMS) – necessitated the application of a conversion equation. Median Canadian RBC folate concentrations (adjusted to microbiologic assay) were lower than those of Americans but unadjusted Canadian median RBC folate values were higher. Canadian WCBA were less likely than American WCBA to have RBC folate ≥906 nmol/L, though Canadian WCBA with unadjusted RBC folate values were more likely to achieve this cut-off. These results indicate a need for strategies targeting WCBA to improve compliance with folic acid supplement recommendations. The strength and necessity of supplements for the general population should be re-assessed. Further, harmonization of folate measurement procedures in future surveillance efforts would support comparisons and inform policy directions.

60 % of Canadians have suboptimal vitamin D (<75 nmol/L) and 25% are obese. Obesity has been reported to be a risk factor for low vitamin D, but there is uncertainty about the magnitude of the association. Linear regression was performed using data from the nationally representative cross-sectional Canadian Health Measures Survey (2007-2009). Height, weight, waist circumference (WC), and vitamin D levels were directly measured. There were 5298 participants aged 6 to 79 years. Using a conservative p value of 0.001, body mass index (BMI) category obese / obese I was positively associated and WC was inversely associated with vitamin D level in crude analysis. WC was inversely associated with vitamin D level in multivariate analysis. The pattern of relationship is not the same as other studies, yet this was a large study with direct measurements. There may be issues with linearity of relationships or subgroups disturbing the relationship.

60 % of Canadians have suboptimal vitamin D (<75 nmol/L) and 25% are obese. Obesity has been reported to be a risk factor for low vitamin D, but there is uncertainty about the magnitude of the association. Linear regression was performed using data from the nationally representative cross-sectional Canadian Health Measures Survey (2007-2009). Height, weight, waist circumference (WC), and vitamin D levels were directly measured. There were 5298 participants aged 6 to 79 years. Using a conservative p value of 0.001, body mass index (BMI) category obese / obese I was positively associated and WC was inversely associated with vitamin D level in crude analysis. WC was inversely associated with vitamin D level in multivariate analysis. The pattern of relationship is not the same as other studies, yet this was a large study with direct measurements. There may be issues with linearity of relationships or subgroups disturbing the relationship.

No description available.

The increased number of international immigrants and associated global problems of health deterioration and vitamin D (vitD) deficiency/insufficiency may lead to significant burdens for host countries. This thesis investigated immigrants’ health deterioration and vitD status through a comprehensive analysis of Canadian national vitD data, systematic evaluation of the quality/content of clinical practice guidelines, and global systematic review of vitD status and determinants among first-generation immigrants. Immigrants had lower serum 25-hydroxyvitamin D (S-25(OH)D) and higher melanin levels than non-immigrants. S-25(OH)D levels improved over time, with ethnicity the main factor explaining variations. The longer immigrants lived in Canada, the higher the prevalence of chronic diseases (CDs), potentially reflecting health deterioration. Low levels of accumulated S-25(OH)D may impact CD-related biomarkers, partially explaining immigrants’ health deterioration over time. Local and international guidance regarding immigrants’ vitD deficiency/insufficiency was lacking. Improving immigrants’ vitD status requires prevention and intervention programs (e.g., vitD supplementation/screening), relevant national/international guidelines, and longitudinal research clarifying the complex bidirectional association between S-25(OH)D and CDs.

Les ignifuges sont ajoutés à divers produits afin de les rendre conformes aux normes d’inflammabilité. Les plus communs sont les polybromodiphényléthers (PBDE) et les esters d’organophosphorés (OPE), qui sont détectés en forte proportion dans la population générale. Quelques industries, comme celle du recyclage électronique, peuvent exposer les travailleurs à des niveaux élevés de ces ignifuges, dont certains sont soupçonnés d’être des perturbateurs endocriniens. L’objectif de cette thèse était d’évaluer l’exposition à des ignifuges chez les travailleurs et d’étudier les effets endocriniens associés. Trois types de données ont été utilisés. D’abord, deux bases de données populationnelles ont permis de déterminer les valeurs biologiques de base des PBDE chez les travailleurs des populations générales canadienne et états-unienne, et d’identifier les secteurs industriels les plus exposés. Ensuite, une revue systématique de littérature a recensé les niveaux d’exposition professionnelle aux ignifuges dans diverses industries en portant un regard critique sur les méthodes de prélèvement. Finalement, des prélèvements d’air en poste personnel, d’urine et de sang ont été réalisés auprès de 100 travailleurs dans six entreprises de recyclage électronique et une de recyclage commercial. Des modèles Tobit et des régressions de Cox inversées ont identifié les tâches les plus exposantes. L’association entre les mesures biologiques d’exposition et les niveaux d’hormones thyroïdiennes et sexuelles a été explorée avec des modèles Tobit et des régressions sur composantes principales. L’analyse des données populationnelles a révélé que les travailleurs canadiens, tous secteurs confondus, avaient des concentrations sériques de PBDE 10 à 20% plus élevées que celles des non-travailleurs. La revue systématique a identifié les milieux du recyclage électronique, de la fabrication de câbles, du transport aérien et des casernes d’incendie comme étant parmi les plus exposants aux ignifuges, particulièrement au BDE209. Cependant, les méthodes de prélèvement utilisées dans ces études étaient généralement peu appropriées pour les ignifuges. L’analyse des données de l’étude terrain a mis en évidence des concentrations d’ignifuges dans l’air plus élevées dans le recyclage électronique que dans le recyclage commercial, avec une concentration en BDE209 plus élevée que toutes les valeurs publiées à ce jour (moyenne géométrique [MG] : 5100 ng/m³). Les tâches de démantèlement et de compactage étaient respectivement associées à des expositions en moyenne 2,2 et 1,4 fois plus élevées que celle de supervision. Finalement, les concentrations sanguines de BDE209 (MG : 18 ng/g lipides) chez les travailleurs du recyclage électronique étaient plus élevées que dans le recyclage commercial (MG : 1,7 ng/g lipides), mais moins élevées que celles rapportées dans la fabrication de câbles (moyenne : 54 ng/g lipides). On a estimé chez l’homme des diminutions de 18% de la testostérone libre et totale pour un doublement de la concentration de tb-TPhP (métabolite OPE), et une augmentation de 16% de l’estradiol pour un doublement de la concentration de o-iPr-DPhP (métabolite OPE). Cette thèse montre que l’exposition aux ignifuges est très répandue, particulièrement chez les travailleurs de quelques industries. Les concentrations plus élevées de certains ignifuges dans le recyclage électronique par rapport aux autres industries, et l’association entre l’exposition aux OPE et les niveaux d’hormones sexuelles chez l’homme ont été identifiées pour la première fois. Bien que devant être reproduits, ces résultats justifient des efforts préventifs de maîtrise de l’exposition aux ignifuges dans cette industrie. / Flame retardants are added to various products to comply to flammability standards. The most common are polybrominated diphenyl ethers (PBDEs) and organophosphate esters (OPEs), which are detected in high proportion in the general population. A few industries, such as electronic recycling, can expose workers to high levels of flame retardants, some of which are suspected of being endocrine disruptors. The objective of this thesis was to evaluate the exposure to flame retardants in workers and to study the associated endocrine effects. Three types of data were used. First, two population databases were used to determine baseline PBDE levels for workers in the general population in Canada and the United States, and to identify the major industrial sectors that are exposed the most. Then, a systematic literature review identified levels of occupational exposure to flame retardants in various industries while critically examining sampling methods. Finally, personal air, urine and blood samples were collected from 100 workers in six electronic recycling and one commercial recycling companies. Tobit models and reverse Cox regressions identified the most exposing tasks. The association between biological concentrations of flame retardants and thyroid and sex hormone levels was explored with Tobit models and principal component regressions. The analysis of the population data revealed that Canadian workers, taking all sectors into consideration, had serum PBDE levels 10 to 20% higher than those of non-workers. The systematic review identified electronic recycling, cable manufacturing, air transport and fire stations as some of the workplaces where flame retardants were found in the highest concentrations, particularly BDE209. However, the sampling methods used in these studies were generally not optimal for flame retardants. Analysis of the field study data revealed higher air concentrations of flame retardants in electronic recycling than in commercial recycling, with a higher BDE209 concentration than all values published to date (geometric mean [MG]: 5100 ng/m³). Dismantling and bailing tasks were associated with exposures averaging 2.2 and 1.4 times higher than supervisory tasks, respectively. Finally, blood concentrations of BDE209 (MG: 18 ng/g lipid) in electronic recycling workers were higher than in commercial recycling (MG: 1.7 ng/g lipid), but lower than those reported in cable manufacturing (average: 54 ng/g lipid). Decreases of 18% in free and total testosterone were estimated in humans for a doubling of the concentration of tb-TPhP (OPE metabolite), and a 16% increase in estradiol for a doubling of the concentration of o-iPr-DPhP (OPE metabolite). This thesis shows that exposure to flame retardants is widespread, particularly among workers in a few industries. The higher concentrations of some flame retardants in electronic recycling compared with other industries, and the association between exposure to OPEs and sex hormone levels in humans were identified for the first time. Although these results must be reproduced, they justify preventive efforts to control exposure to flame retardants in this industry.