Predictors for Increased and Reduced Rat and Mouse Allergen Exposure in Laboratory Animal Facilities.

Introduction: Exposure to rat and mouse allergens during work in laboratory animal facilities represents a risk for being sensitized and developing allergic diseases, and it is important to keep the exposure level as low as possible. The objective of this study was to characterize the personal Mus m 1 and Rat n 1 exposure during work in laboratory animal facilities, and to investigate the effect of identified predictors of increased and reduced exposure. Methods: Mus m 1 and Rat n 1 were analysed in whole day or task-based personal air samples by enhanced sensitivity sandwich enzyme-linked immunosorbent assay. Information about cage-and-rack systems, tasks, and other conditions known to influence the allergen exposure was registered. Predictors for allergen exposure were identified by multiple linear regression analyses. Results: The median allergen exposure was 3.0 ng m(-3) Mus m 1 and 0.5 ng m(-3) Rat n 1, with large task-dependent variations among the samples. The highest exposed job group were animal technicians. Cage emptying and cage washing in the cage washroom represented the highest exposure, whereas animal experiments in the lab/operation room represented the lowest exposure, with laminar airflow bench being an exposure-reducing determinant. Cage changing was the highest exposed task in the animal room, where individually ventilated cages (IVCs) were predictors of reduced exposure for both Mus m 1 and Rat n 1, whereas cage-rack systems with open shelves and sliding doors were predictors of increased Rat n 1 exposure. Cages of IVC type with positive air pressure (IVC+) as well as open shelves and sliding doors were strong predictors of increased exposure during cage emptying and cage washing. Conclusions: Significant different exposure levels depending on type of work and task imply different risks of sensitization and allergy development. The fact that IVC+ cages have opposite impact on Mus m 1 and Rat n 1 exposure during different tasks may have positive clinical implications when taken into account.