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Caractérisation des expositions professionnelles des éleveurs laitiers bretons : déterminants professionnels de l’exposition à la fraction thoracique des bioaérosols, à l’ammoniac et à l’acétaldéhyde, et effets inflammatoires des poussières organiques

Abstract : Dairy farmers have an increased risk of lower airway diseases that is likely related to occupational exposures to airborne contaminants. Nevertheless, occupational determinants of dairy farmers’ exposures remain poorly documented and the biological effects of the contaminants chronically inhaled by farmers need to be fully characterized. In this context, the objectives of this PhD thesis were i) to identify the occupational determinants of exposure to thoracic bio-aerosols (organic dusts, endotoxins, bacteria and moulds), ammonia and acetaldehyde, and ii) to characterize the pro-inflammatory effects of thoracic dusts emitted during the mechanical spreading of straw bedding, a task well-known to generate inhalable dusts. To achieve these goals, we carried out a 112-repeated exposure measurement campaign on 29 dairy farms located in Britany. Using multivariate mixed-effect regression models, we have demonstrated that farmers’ exposures to bio-aerosols were mainly induced by tasks related to bedding material distribution and cow feeding (straw, hay, silage). Exposure levels to ammonia were highly dependent on cow numbers and times spent by the farmers in stable and milking parlour. Acetaldehyde exposure was modulated according to the farm size and times spent to distribute silage. Our work also highlighted that an increase of the area of wall opening significantly reduced exposure to mould, acetaldehyde and ammonia. Finally, our study showed that dusts emitted during mechanical straw spreading have (1) a size small enough to allow them to deposit in the tracheobronchial regions, (2) a complex bacterial and fungal composition, and (3) strong in vitro pro-inflammatory effects that induced TNF-α, IL-1β, IL-6 and IL-8 expression in human macrophages. In conclusion, these results have identified different dairy farm characteristics and occupational tasks that significantly increased the exposure levels to chemical contaminants and thoracic organic dusts. Statistical models built during this research project already allow reconstitution of dairy farmers’ exposure that may of use in future epidemiological studies and to develop new preventive measures.
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Hugo Pfister. Caractérisation des expositions professionnelles des éleveurs laitiers bretons : déterminants professionnels de l’exposition à la fraction thoracique des bioaérosols, à l’ammoniac et à l’acétaldéhyde, et effets inflammatoires des poussières organiques. Médecine humaine et pathologie. Université Rennes 1, 2017. Français. ⟨NNT : 2017REN1B046⟩. ⟨tel-01830189⟩

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