Determination of the Moisture Content and the Generation of Airborne Particulate Matter From Various Types of Footing From Indoor Riding Arenas Considered to Have Optimal Rideability

It has been known for some years now that the occurrence of lameness in horses is closely related to the characteristics of the riding surface and that respiratory tract diseases can be induced by airborne particles. To ensure both optimal rideability (e.g., grip, elasticity, etc.) and low dust production, riding surfaces have to be regularly attended to, which also includes watering the floor. However, at present, it is not known what the individual moisture content of the various types of riding surface should be to ensure optimal rideability or what their potential for releasing dust is at the time of optimal rideability. The aim of the present study was to determine the moisture content, the density as weight/liter, particle size distribution and the release of airborne particulate matter (APM) with a diameter <10 mu m (PM10) of the footing material from three types of indoor riding arena surfaces considered to have optimal rideability. Loose footing material samples were taken from the surfaces of 25 indoor riding arenas [5 pure sand (S), 10 sand-wood chips (SW), and 10 sand-fibre (SF)] and investigated under standardized conditions. The evaluation of the surface's rideability was carried out subjectively by the respective facility manager. The ambient particulate monitor TEOM 1400a was used to measure the PM10 production from the footing samples. Although, according to the facility managers, all of the investigated riding surfaces had optimal rideability at the time of sampling; obvious differences could be found with respect to their moisture content, density, particle size distribution, and release of APM, both between and within the 25 indoor arenas. The moisture content of SW (14.96 +/- 4.00%) was significantly higher than that of SF (8.99 +/- 2.95%; P =.0046), but the S moisture content (10.82 +/- 2.65%) was not significantly different to either of them (S vs. SW: P .0982 and S vs. SF: P =.2446). With respect to the release of APM, it could be shown that the average release from SF was 2.50-5.47 times higher than either for the S or SW (C-sum -S: 12.81 mg/m(3) air, SW: 5.86 mg/m(3) air, and SF: 32.06 mg/m(3) air; t-test-S vs. SW: P =.3882, S vs. SF: P =.2560, and SW vs. SF: P =.0031). The reason for this was the extremely high APM release in three of the ten investigated SF samples. In addition, significant differences were also observed in the APM release within the three individual types of footing. Although no factors significantly affected the release of APM in either the S or SW footings, the density of the SF footing was found to have a significant influence on its APM production: the higher the density, the lower the APM release. The density itself was related to both the footing's moisture content and fiber content. The reason why SF footings with a low density (associated with a high fibrous material content) and a high moisture content tended to cause a greater release of APM is that there was a segregation of the fibrous material caused by the measuring technique used. This led to the fibrous material rising to the top of the sample resulting in a release of APM directly from this material. To prevent such a high release of particles from SF footings with a high fiber content occurring in practice, such footings should be regularly and adequately watered, and any segregation of the fibrous material should be prevented using suitable arena grooming techniques. (C) 2019 Elsevier Inc. All rights reserved.