Different types of bedding have different properties including differences in water-holding capacity, littering effects, airborne dust particles, and combustion potential. Temperature and humidity can change the qualities of bedding material, affecting the microbial ecology of clean and soiled bedding as well as the surrounding environment. Chronic obstructive pulmonary disease and exercise-induced pulmonary hemorrhage can develop as a result of organic particulate matter, such as bedding dust, forage-residing fungi, and molds. Therefore, horses are sensitive to organic particulate matter. The objective of this study was to compare the chemical, physical, and environmental properties of pelleted newspaper (PN), straw (S), and wood shavings (WS) as bedding material for horses. Horses were individually housed in boxstalls, where four types of bedding were tested: two types of PN (0.32 and 0.64 x 2.54 cm), S and WS. In the first experiment, only feces were cleaned daily in order to challenge the each material’s properties, and additional bedding was added as needed. In the second experiment, PN (0.32 x 2.54 cm), S and WS were also tested, but in this experiment feces and wet spots were removed every day and new bedding was added to an amount that was similar to the amount added in commercial conditions. The results indicated that the amount of clean bedding that needed to be added varied depending on the type of bedding material (S>WS>PN). Due to the higher water-holding capacity of PN and WS, less replacement bedding was required. More bedding (of all tested) was required during the autumn compared to the summer. The bedding environment was also influenced by type of material and season. PN had the greatest increase in pH and S had the lowest increase in pH. Stalls bedded with PN had higher concentrations of breathable NH3N during the autumn. The used PN with higher pH and less ventilation during the autumn contributed to the poor air quality. The number and species of microorganisms found in the breathing zone, nasal cavity and on the leg of the horse were affected by the season, type of bedding and duration of its use. The amount of dust also varied with type of bedding and duration of use. PN and WS resulted in more dust than S. The results indicate that bedding materials need to be managed based on the type of material and season of year.