Ammonia is an inorganic compound with the chemical formula NH3. Humans and other animals are exposed to ammonia in a number of natural and human-made settings.
Ammonia is a colorless gas with a density of 0.73 kg/m3 and a specific gravity (compared to air) of 0.597, indicating that it is about half as dense as air. It has a strong, pungent, suffocating, characteristic odor. It is very soluble in water, with which it reacts to form ammonium hydroxide, a weak base. Pure gaseous ammonia is sometimes referred to as anhydrous (“without water”) ammonia.
Ammonia is a very important industrial chemical. It ranks second only to sulfuric acid in quantity produced in the United States each year. Of the approximately 20 million tons made annually, about 80 percent is used in the manufacture of fertilizers. Ammonia is also used for a variety of other purposes, including as a coolant in refrigeration units; in the production of cleaning and bleaching agents; as a fungicide to protect fruit crops; in the synthesis of a host of other chemicals, including plastics; and in the processing of metals. Ammonia is also produced naturally during the decomposition of dead plants and animals. By some estimates, about 200 million tons of ammonia are produced each year through this process.
The ambient levels of ammonia to which individuals are exposed in daily life are too low to cause any health problems. Normal amounts of ammonia released from the ground, water, and synthetic products are readily abosrbed by moisture in the air or in the ground, leaving concentrations in the air so low as to be generally harmless. However, accidents sometimes occur in which large concentrations of the gas are released to the surrounding environment. In such instances, ammonia exposure may result in significant harm to the health of humans and other animals.
Ammonia releases may occur during production of the compound or during one of its many uses. For example, ammonia used to make nitric acid (which, in turn, is used to make synthetic fertilizer) can escape from leaks in pipes at a production plant or when breaks in equipment occur. By far the more common instances of ammonia release, however, involve its transport and use as anhydrous ammonia fertilizer and its use in refrigeration systems. Some examples include the following:
Ammonia accidents are relatively uncommon in both the United States and the rest of the world. The U.S. Occupational Safety and Health Administration (OSHA), for example, reported that it had investigated a total of 224 discrete ammonia accidents between 1984 and 2006, with a total of 50 deaths attributable to those accidents. Other countries around the world have had an even better record than the United States. For example, Germany has reported a total of two deaths from ammonia-related accidents in 22 years of record-keeping, while most developed nations have had only one death or not at all. Sweden, Norway, Finland, and Denmark, for example, have all been keeping records for more than 60 years, with only one ammonia-related death having been recorded during that time.
The health risks posed by ammonia increase with concentration. The following list indicates the signs and symptoms typical of various concentration levels of the gas.
Ammonia is not known to be a carcinogen or a teratogen. Although little data are available, ammonia is not thought to have health effects on children different from those on adults. Individuals with asthma or other respiratory disorders are likely to experience more severe reactions than those with normal respiratory function.
Diagnosis of ammonia exposure is generally easily made based on the report of an ammonia spill incident or a person's report of exposure to the characteristic odor of the gas.
In all cases of exposure to high concentrations of ammonia, medical help should be provided as soon as possible. In cases of inhalation, the patient should be removed to an area with fresh air and, if breathing is difficult, provided with oxygen and, if necessary, artificial respiration. Burns to the skin should be treated with a fresh water rinse that lasts for at least 15 minutes. Ingestion of the gas should be treated with large volumes of water by mouth, while avoiding inducing vomiting.
Ammonia exposure is generally not a serious problem for individuals who do not work in proximity to facilities where ammonia is available in large quantities, such as farms or refrigeration facilities. The amount of ammonia inhaled from household products, for example, is too low to cause serious health problems. Facilities where large quantities of the gas are in use can take a number of steps to ensure that their systems are in good repair, functioning properly, and lacking cracks or breaks through which ammonia can escape. The U.S. Environmental Protection Agency (EPA) has published a brochure providing detailed suggestions for inspection of systems in which ammonia is kept and transported. The EPA also recommends the installation of ammonia detection devices that can warn of leaks that may pose a threat to workers.
See also Asthma ; Fungicide ; Occupational Safety and Health Administration ; Teratogen .
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Agency for Toxic Substances and Disease Registry, 4770 Buford Hwy., N.E., Atlanta, GA, USA, 30341, (800) 232–6348, http://www.atsdr.cdc.gov/ .
David E. Newton, EdD