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| NAWQA Program |
National Water-Quality Assessment (NAWQA) Program | VOC National Synthesis
Oxygenates, when added to gasoline, are designed to add oxygen to the gasoline, thereby decreasing vehicular carbon monoxide emissions and ozone levels in the atmosphere. The Clean Air Act Amendments (CAAA) of 1990 mandate seasonal or year-round use of oxygenated compounds in gasoline in specific areas of the United States. Methyl tert-butyl ether (MTBE) has historically been the most widely used oxygenate in the United States. From 1984 to 2000, the production of MTBE increased by about 20 percent annually with around 9.1 billion kilograms produced in 2000. Ethanol, the second most commonly used gasoline oxygenate, had an average increase in production of 10 percent from 1984 to 2000, with about 4.9 billion kilograms produced in 2000.
Routine monitoring of ambient ground water by the U.S. Geological Survey's (USGS's) National Water-Quality Assessment (NAWQA) Program between 1993-1998 documented the frequent occurrence of MTBE, typically at low levels, in shallow urban ground water. In 1997, the NAWQA Volatile Organic Compound National Synthesis (VOCNS) Team created a web site listing publications with a primary focus on the water-quality aspects of MTBE.
The detection of MTBE in ground water and its classification as a possible carcinogen by the U.S. Environmental Protection Agency (USEPA) led to several assessments of MTBE and its environmental impacts. In 1997, the Office of Science and Technology Policy, Executive Office of the President, released an interagency assessment of the scientific basis for, and efficacy of, the winter oxygenated gasoline program. Shortly thereafter in 1998, the MTBE Blue Ribbon Panel was created by a Charter from the Clean Air Act Advisory Committee to provide independent advice and counsel to the USEPA related to the use of MTBE and other oxygenates in gasoline. They concluded that MTBE detections have primarily caused consumer odor and taste concerns, and that in some instances MTBE has been found in drinking water supplies at levels above USEPA's drinking water advisory of 20 to 40 mg/L which is based on taste and odor thresholds. Some States have established drinking water standards, advisories, and guidelines for MTBE.
Although MTBE, and to a lesser extent, ethanol currently dominate the oxygenate market, no specific oxygenate is required or designated by the 1990 CAAAs. Other ethers and alcohols can serve as gasoline oxygenates and the use of these compounds may become more prevalent, depending on various economic factors such as: cost; ease of production and transfer; blending characteristics; and environmental and health concerns. These gasoline oxygenates are classed as: (1) ethers, including ethyl tert-butyl ether (ETBE), diisopropyl ether (DIPE), dimethyl ether (DME), methyl tert-butyl ether (MTBE), tert-amyl ethyl ether (TAEE), tert-amyl methyl ether (TAME); and (2) alcohols, including ethanol (EtOH), methanol (MeOH), tert-amyl alcohol (TAA), and tert-butyl alcohol (TBA).
The previously described MTBE bibliography has been expanded to include select publications pertaining to all gasoline oxygenates with the focus on occurrence and trends of the compounds and environmental processes that may affect the behavior and fate of the compounds.
The Oxygenate Bibliography includes references from a variety of sources. Many references were obtained through the Chemical Abstracts Data Base. Additional references were compiled with the help of other interested parties including international research sources, industry and their commercial affiliates, research laboratories, and other governmental agencies, including the USEPA.
Every effort has been made to include only published materials. Only proceedings and abstracts/extended abstracts from conferences and symposia that have gone through peer review processes are included in the Oxygenate Bibliography. Gasoline oxygenate publications focusing on occurrence, trends and understanding of gasoline oxygenates in water are emphasized. Because of extensive coverage on other web sites, such as the USEPA's, information on the following topics generally are not included: drinking-water standards and health advisories; economics and production; human health; laboratory experiments; remediation and cleanup technologies; and toxicity to aquatic organisms.
The references were categorized by a member of the NAWQA VOC National Synthesis Team. Citations retrieved by a search are in U.S. Geological Survey bibliographic format.
The Oxygenate Bibliography is searchable using a keyword search. The initial word search should begin with the oxygenate acronym(s) (e.g. the acronym for methyl tert-butyl ether is MTBE). Topics that aid in further defining the search include transformation, transfer, and transport processes, environmental occurrences and miscellaneous. Each topic has a listing of searchable keywords to facilitate a search. References may appear under more than one of the keyword searches.
In addition, the Oxygenate Bibliography is searchable using a free text search. The free text search locates references only if the search word is contained within the citation. Citations for publications from a particular year or author can by retrieved using the free text search (for example, search for 1998 or Moran)
In addition, the full bibliography can be viewed as follows: sorted by author | or sorted by publication date
The bibliography will be updated periodically. Suggestions for new listings or other comments are appreciated. Please submit them to Joshua Valder using this comment form.
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