Lots of Americans would love to go watch a horse show. The major drawback for those with respiratory problems is arena dust. This dust is not only dangerous to the spectators and riders, but also the horses.
Arena dust occurs when the base of an arena is not properly compacted or has become mixed with the soil that is used. For an average arena, a normal year's wear and tear will only wear the surface down 1/8 of an inch. As the surface becomes more used, the dirt is reduced down more and more until the particles are small enough to become airborne.
Sometimes unwashed sand is used to cover the arena floor, but it does not produce dust because the particles are of adequate size to not become airborne. Another benefit of unwashed sand is that it contains from 10 percent to 30 percent clay. Clay is a small particle that can easily become airborne, but it has other qualities that reduce the amount of the dust. One is that clay has the capability to bind with other particles in the sand. This helps to minimize the smaller particles that could become airborne that are in with the sand.
A liquid that is used to minimize arena dust is water. This is an effective method, but it is a temporary solution. To increase its potency, it must be done in significant quantities. In most cases, if water is soaked down two inches, this will be sufficient enough until the moisture evaporates. For most arenas to control dust, not only can they make use of water, but they could also use salt.
The most common salts are calcium or magnesium chloride. The physical properties of these salts are what make them compatible with water. This is their "hydroscopic properties" or ability to absorb moisture. Unfortunately, there is a risk that is associated with calcium chloride and its caustic effect on the horses and a rider's skin. Magnesium chloride is the recommended salt. As an added precaution, it is recommended that the horse's lower legs and hooves be washed down after being in an arena treated with magnesium salts.
There are other dust suppressors for an arena, but magnesium chloride combined with water is the most efficient solution to combat arena dust.