Most often, ammonia irritates vulnerable tissues such as skin, eyes, nasal passages, sinuses, the respiratory tree and the lungs. The effect can range from short-lived reversible discomfort, to serious health effects that are chronic, irreversible, and sometimes even life-threatening.
What makes the health risks even more serious is the fact that because of emotional context and olfactory fatigue, our self-protective response to ammonia exposure in the stable is impaired. If we’re better informed about this noxious gas, we can stop underestimating not only its inherent dangers, but also the impact we can have on significantly reducing ammonia in the stable. How much ammonia is too much? The standard reference that sets the safety limits for exposure to noxious gases, including ammonia, is the Acute Exposure Guideline Level, or AEGL. There are three AEGL levels of exposure, each divided into five exposure periods: 10 min, 30 min, one hour, four hours, and eight hours. The stronger the ammonia, the shorter the exposure time that can cause irreversible injury. What you need to know about ammonia in the stable Ammonia levels in the stable are higher, and a more serious health risk for ourselves and our horses, than most people think. Most assessments of air quality in stables are made subjectively, by olfactory-fatigued noses of humans, standing upright in the stables and barns. Assessments are rarely done objectively, with instruments designed to measure ammonia, not only at standing human nose level but in all relevant areas of the barn, especially at floor level in the stables. It must also be noted that much of the air a stabled horse draws into his lungs is within that low-down floor-level range where ammonia levels are highest — when he’s standing and nibbling at feed that was placed on, or has fallen to, the floor, and when he’s lying down and sleeping (when he’s breathing most deeply, really pulling those fumes in). Because foals sleep so much, a foal in that stable would breathe higher levels of ammonia than fresh air. 
Managing ammonia
Most owners and grooms are aware that ammonia is unpleasant, and they take steps to address it. Nevertheless, ammonia levels easily can be high enough, even in well-heeled stables, to pose a health risk. The methods most often employed to reduce ammonia levels include: - moving the fumes, with ventilation, - improving hygiene through more frequent stall cleaning, and - applying agents such as lime and zeolite products to the wet spots in stalls, to absorb and “neutralise” the ammonia. There is nothing wrong with these methods, but it’s clear that they are not enough. They treat the symptoms, not the underlying problem. The underlying problem To get at the source of the fumes, we need to understand where the ammonia in the stable comes from. It’s not, technically, from urine. Ammonia is not a normal component of urine. Urine contains urea, which is a byproduct of the digestion and metabolism of protein in the horse’s diet. But urea is odourless. So where does the ammonia come from? From the breakdown of urea, which is done by various bacteria that happen to love urea as a food source. If it’s available to them, they’ll flourish on it. They’re equipped with an enzyme called urease which digests the urea and produces ammonia as a by-product. But healthy urine is sterile. It doesn’t have bacteria in it. So where do those urea-digesting, ammonia-belching bacteria come from? They’re abundant in many substrates on the ground. If urea is regularly available to them, their originally small population there will explode, and the level of ammonia in the stable will intensify exponentially with every new “delivery” of urea-rich food (your horse’s urine). The situation quickly escalates to the point at which stripping the stall and leaving it empty for a few days to dry does nothing to dampen the ammonia smell. There’s so much stockpiled urine already soaked deeply into the substrate that the bacteria can live on its urea for a long time, while the ammonia continues to stream up and into the stall. Removing the source In the construction of stables, the tradition is to provide “good drainage” in the stalls. Now, we know better. Good drainage is important to keep the barn from flooding in heavy rains, but for the stalls themselves, it’s important to stem the tide of ammonia fumes by making the floor non-porous. That way, you can contain the urine. This gives the bedding more chances to absorb it, so that when you muck out the wet bedding you can remove all the urine and starve subterranean populations of bacteria that have been thriving on its steady supply of urea. A good way to achieve that is to equip new or existing stalls with a wall-to-wall, non-porous, seam-sealed and perimeter-sealed rubber mat such as ComfortStall from Haygain. ComfortStall installation resulted in a significant reduction in ammonia within a couple months of installing them over previously porous floors. It is the flooring of choice for Cornell University Veterinary Hospital where over 1,000 horses a year recover from surgery on the system. |
|