ODOR
Molecules that Influence our Life

Odors influence human beings

The senses smell and emotion are tightly connected. The sense of smell influences important behaviors such as eating, orientation, procreation. Without our being aware of it, it affects our life and influences for instance sexual desires, whether we like or dislike a person or thing.

Anything that smells emits tiny amounts of molecules into the surrounding air. The odor reaches the mucous membranes (30 million cells) that convert the chemical odor signal into an electric cell answer. If – for instance – a person smells ammonia, a complicated process starts in our body: The sense of smell differentiates between various gaseous or water-soluble molecules. As the sense of taste, the sense of smell is considered a chemical sense. It is thought to be genetically the oldest sense of the human race.

The Effect of Ammonia

Unpleasant odors, for instance, are caused by ammonia. It is a colorless, sharp smelling, water soluble, irritating gas. It not only irritates the mucous membranes, a deciding factor is the strength of odors. The „Laenderausschuss fuer Immissionsschutz” (LAI), the committee of the states for protection from emissions, suggested a guideline for the threshold of odor of 1900ug/m³ for ammonia. Studies have proven that even 10fold increases did not have a negative effect on a persons health. Thus it can be assumed that by observing the odor threshold of ammonia the toxic aspects of its effect on people is also taken into consideration.

The largest amount of ammonia emission in Europe today results from agriculture. The raising of animals presents with 70 to 90 percent of the total emission the largest share of pollution, followed by the use of nitrogen containing fertilizers. The most important source is the decomposition of animal excretions. In excrements nitrogen is contained in hard to break down proteins, in urine it is mainly as easily degradable urea. Bacterial and enzymatic decomposition of nitrogen containing compounds from urine and excrement create a quickly evaporating ammonia. About one third of the ammonia emissions are the result of animals being raised on grassland. A greater animal waste problem was created until a few years ago by an increased breeding of animals and keeping them in large numbers in central locations. The use of nitrogen containing fertilizers added considerable amounts of emissions.

The industrial area emits approx. one to two percent ammonia into the atmosphere; fertilizer-, ammonia- and nitre- factories are to blame but also the use of coolants. Fossil fuels emit lesser amounts, especially when burning coal in power plants (Entstickung), in waste incinerators and by the combustion of diesel fuel and gasoline. There are natural sources for ammonia emission besides the anthropogenetic (man made) ones. Microscopic decomposition and transformation help to release ammonia from the soil. The small role of NH₃-emission from natural sources in middle Europe is made clear by the fact that the anthropogenetic sources are 15 to 30 fold higher.

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