AMMONIA EMISSIONS CAN BE DANGEROUS
Gas combining with sulphuric acid in air can cause health problems
Once you have sniffed ammonia, you are not likely to forget its penetrating odour. Just ask the paramedics who responded to an emergency call from a home in Virginia: they were almost overcome by the powerful smell of the gas. They quickly transported the occupant, who was in respiratory distress, to hospital and alerted the Sheriff ’s Department about the overpowering odour. Deputies wearing protective suits and breathing equipment found 40 chickens, three dogs and a cat occupying the premises. The homeowner who had been overcome by the ammonia fumes managed to recover, only to be charged with three counts of inadequate care of a companion animal and two counts of inadequate care of an agricultural animal. His residence was condemned by the fire marshal. Mammals, like dogs and cats, eliminate extra nitrogen from their bodies by incorporating it into urea, a water-soluble compound that is excreted in the urine. Poultry and birds have a different mechanism for nitrogen disposal, eliminating excess in the form of uric acid instead of urea. Since birds don’t have different orifices for eliminating urine and feces, both are expelled together. Uric acid is not very soluble and its white crystals dominate the colour of bird poop. Both urea and uric acid break down to release ammonia when acted upon by urease, an enzyme produced by various bacteria that are found in fecal matter as well as in the soil. This makes animal output a source of ammonia gas, a significant air pollutant. When animals are kept indoors without adequate air circulation, ammonia can build up to toxic levels, as the Virginia victim discovered. In commercial barns and poultry houses, the gas can have a negative impact on animal health and can irritate the lungs of workers. Outdoors, volatilized ammonia can travel hundreds of miles from animal-production facilities and cause problems. It combines with traces of sulphuric acid in the air to form tiny particles of ammonium sulphate that can penetrate deep into the lungs, exacerbating respiratory and cardiovascular disease. The particles also cause haze and a reduction in visibility. Where does the sulphuric acid come from? It forms when sunlight promotes the reaction of sulphur dioxide, produced by burning sulphur-containing fossil fuels, with moisture in the air. There are still further problems. Ammonia in the air can dissolve in surface waters, fertilizing the growth of algae. When these die, they decompose via a process that uses up oxygen in the water, leading to the decline of fish populations. Obviously, any measure that can lessen ammonia emissions is welcome. A novel approach is to reduce the amount of nitrogen that cattle eliminate by increasing the proportion of the feed that the animal can incorporate into its body mass. The Food and Drug Administration in the U.S. has recently approved a cattle feed additive that accomplishes this. “Lubabegron” was initially studied for potential applications in human health, particularly in the treatment of diabetes. However, along the way, researchers discovered that it improved the assimilation of food, giving rise to the idea of incorporating it into animal feed. Just how much of an impact it will have on ammonia emissions isn’t clear from the small-scale studies that have been carried out, but no adverse effects on the animals’ health or on the meat they yield have been noted. Ammonia pollution is just another complication of our reliance on eating meat. But don’t think that if we eat only plant foods, we solve the problem. True, plants don’t poop, but they do require fertilizer. That fertilizer is often urea, which can release ammonia when it comes into contact with soil microbes that are equipped with urease. That’s why there is research into chemicals called urease inhibitors that can prevent the release of ammonia from urea. The application of urea combined with N-(n-butyl)thiophosphoric triamide (NBTPT), the most widely used urease inhibitor, can reduce ammonia loss by up to 90 per cent when compared with untreated urea. This also results in a boost in crop yield, since the nitrogen that is not lost as ammonia helps fulfil the nutrient demand of the crop. Not all ammonia emissions are unwelcome. Helicobacter pylori, the bacteria that can cause ulcers, are equipped with urease. To diagnose whether the bacteria are present in the digestive tract, a biopsy specimen is removed during gastroscopy and is placed into a medium containing urea and an indicator such as phenol red. If the bacteria are present, the urease they produce converts urea to ammonia, raising the pH of the medium and causing the indicator to change from yellow to red. Antibiotics can then be used to treat the problem. Finally, you will sometimes see hockey players break open a little ampoule and sniff its contents. They are hoping that a jolt of ammonia will give them a temporary boost in alertness that translates to better performance. And it’s perfectly legal.