The Science of Smell Part 1: Odor perception and physiological ... - PDF document

The Science of Smell Part 1: Odor perception and physiological factors, makes the task of reducing livestock odors Table 1. Examples of varying threshold measurements of odorous substances (odorants). than 5,000 odors but some individuals experi ence anosmia (smell blind ness) for one or more odors. In this situation, the individual apparently has a normal sense of smell, but is unable to detect one partic ular odor regardless of its intensity. For because methyl mercaptan has an odor recognition threshold of only 0.0021 ppm (Table 1), it is often mixed with natural gas as an indicator of leaks; however, approxi mately one in one thou sand persons is unable to detect the strong odor of this mercap tan. 1) the substance must be volatile enough to 2) the substance must be at least slightly 3) the substance must be lipid-soluble 4) a minimum number of odorous particles Olfactory Tract Nares - Vestibule (Nostril)Rhinencephalon - Limbic Center -Taste and Smell . . . and justice for allThe U.S. Department of Agriculture (USDA) prohibits discrimination in all its programs and activities on the basis of race, color, national origin, gender, religion, age, disability, po lit i cal beliefs, sexual orientation, and marital or family status. (Not all prohibited bases apply to all programs.) Many materials can be made available in alternative formats for ADA clients. To Þ le a complaint of dis crim i na tion, write USDA, OfÞ ce of Civil Rights, Room 326-W, Whitten Building, 14th and In de pen dence Avenue, SW, Washington, DC 20250-9410 or call 202-720-5964.Issued in furtherance of Cooperative Ex ten sion work, Acts of May 8 and June 30, 1914, in cooperation with the U.S. Department of Agriculture. Stan-ley R. Johnson, director, Cooperative Extension Service, Iowa State University of Science and Technology, Ames, Iowa.the mechanism of smelling odors. Most can be ed into one of two groups: a physical theory or a chemical theory. The physical theory proposes that the shape of the odorant molecule determines Each receptor cell has several different types of molecular receptor sites, and selection and The chemical theory, which is more widely accepted, as sumes that the odorant molecules bind chemically to protein receptors in the branes of the olfactory cilia. The type of receptor in each olfactory cell determines the type bers. Receptor sensitivity may explain some of the variation in detection olds exhibited by different compounds. For exam ple, ammo nia has an odor threshold of 0.037 ppm whereas the corresponding values for de and sulfur dioxide are 0.00047 and 0.009 ppm, respectively (Table 1).Odor responsesOdor adaptation is the process by which one becomes accustomed to an odor. The adapta tion time needed is greater when more than one odor tion to a particular odor has occurred through pro longed exposure. This situation would apply to milkers or dairy While ammonia and hydrogen sulÞ de are odorants, and not odors per se, they are produced including municipal sewage treatment systems, coal burning, industries and factories, and Both ammonia and hydrogen sulÞ de can cause olfactory losses as a result of chronic or prolonged vous 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 On average, olfactory receptors renew themselves every thirty days. Pollutants may alter this ed for a number of pollut ants, above which odor or irritation occur. Unfortunately, however, knowl edge of the exact mechanisms by which pollutants alter olfaction is Resources This publication along with PM 1963b, Science of and Animal Agriculture Web page at: http://www.extension. iastate.edu/airquality. Proc. of Nuisance Concerns in Animal Management: Odor and Flies Conference, Gainesville, Florida, March 21-22.Table and Þ gures from Water Environment Federation. 1978. Odor Control for Wastewater Facilities. Manual Prepared by Wendy Powers, extension environmental specialist, Department of Animal Science, and edited by Marisa Corzanego, extension communications intern, File: Environmental Quality 4-1