## 1 Introduction
Monitoring occupational exposure to these biological risk agents in animal enclosures is complex as animal caretaker personnel are not limited to a single activity during a shift but instead perform a variety of tasks which contribute at different levels to the total occupational exposure. For example, animal technicians and caretakers had elevated rat and mouse urinary allergen exposure compared to scientific staff and supervisors. For both allergens, cleaning cages and moving animals to new cages were associated with the highest personal exposures; lower exposures were seen with feeding and handling animals. Washing cages was the lowest-exposure task [28]. Moreover, significantly higher concentrations of mouse allergens in the breathing zone were found in mouse handlers than in those not handling mice [13]; a strong correlation between time spent moving cages was also evidenced [28], and differences in the rate of exposure in areas classified as low risk (changing workers' rooms, corridors, offices) and high risk (holding rooms, procedure rooms, cage-washing) were also reported [29]. Typical rat and mouse allergen concentrations in laboratory animal environments range from 10 to 200 ng/m\({}^{3}\). Usually, average endotoxin exposures are considered very low when they range from 0.02 to 1.5 ng/m\({}^{3}\). Average exposure in the range 60-1000 ng/m\({}^{3}\) can be found in grain handlers, hog confinement workers and poultry farmers [30; 31; 32]. A study conducted in a conventional laboratory rabbit room reports a higher concentration of endotoxins in the stationary and personal air samples during specific working activities (cage/tray changing, animal handling, control of food and water and room cleaning) with a typical range of 0.4-1.3 ng/m\({}^{3}\) and 0.7-3.6 ng/m\({}^{3}\), respectively, in static position and personal air sampling. This study clearly demonstrates that the previously listed tasks cause a release of airborne endotoxins [4]. The main objective of this paper was to characterize the complex exposures of workers employed in animal facilities to endotoxin and animal allergens, through samples of air in the breathing zone of the staff during daily working activity, in order to identify the work categories at highest risk of exposure. Since exposure to allergens and endotoxins induces important respiratory effects, personal monitoring represents an important tool aimed at improving prevention and control strategies. Based on our knowledge, few observational studies on the levels of airborne allergens and endotoxins among laboratory animal workers have been carried out in Europe, with scarce data collected in Italy. We believe that this work adds useful information in the context of risk management from biological agents. This study provides a more detailed analysis than that of a previous study [24] whose main objective was to determine which factors (working tasks, changing cages frequency and animal strains) were associated with the greatest level of exposure to biological agents of the personnel working with rodents through environmental monitoring in animal rooms and washing and storage areas. In relation to working tasks, our data showed that (1) changing cages is a determinant factor in increasing the concentration of the airborne bio-contaminants, (2) the preparation of bedding and distribution of feed is another critical working task in terms of exposure to endotoxins, (3) the dirty washing area presents the highest concentration of Mus m 1 allergen.