Air Emissions and Animal Agriculture


While ammonia and hydrogen sulfide are odorants and not odors per se, they are produced through processes often associated with odor, including municipal sewage treatment systems, coal burning, industries and factories and livestock operations. Both ammonia and hydrogen sulfide can cause olfactory losses as a result of chronic or prolonged exposure. Ammonia can also affect the central nervous system. A number of other chemical pollutants, including some insecticides, result in losses in olfaction by damaging olfactory receptors. The use of medications may exacerbate chemosensory disorders.

No single compound has been identified as a good predictor of odor sensation across situations in the field. Because of this, human panelists conduct odor measurements and quantify odor intensity and unpleasantness. Perception of a mixture of odorants, such as those in livestock odor, is very different from how each chemical would be perceived independently. Odorants can act as additive agents, counteractants, masking agents or be synergistic in nature. The combination of two odorants can have an odor equal to that of either one of the components, have an odor less than that of one of the components, have an odor equal to the sum of the components or even have an odor greater than the sum of the components. This makes odor quantification and characterization a challenging process.

Odor can be evaluated subjectively in terms of intensity (strength) or in terms of quality (i.e., offensiveness).  Odor quality is evaluated by describing the odor or comparing the sample odor to familiar odors.  Evaluation of odor quality is difficult because of the challenges that come with trying to describe odors.

Last Updated 05/30/2011