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Uranium

Overview
 
CAS Number: 7440-61-1
Synonyms: U-234, U-235, U-238
Contaminant Type: Radiological

Some drinking water sources have very low levels of radionuclides (radioactive elements). A radionuclide is an unstable (decaying) form of a nuclide. Uranium has three radionuclides that are detected in and regulated in drinking water. U-238 is an alpha emitter and the parent compound in the uranium-238 series. Its half life is approximately 4.5 billion years. U-235 is also an alpha emitter and the parent compound in the actinium series. Its half life is approximately 710 million years. U-234 is a beta emitter and the third-member decay product of the uranium-238 series. Its half life is approximately 250,000 years. Long half lives lead to their stability in water. [586] Uranium is regulated in drinking water as the sum of its isotopes.

Uranium is naturally occurring and predominantly found in groundwater in the Colorado Plateau, the Western Central Platform, the Rocky Mountain System, Basin and Range, and the Pacific Mountain System. Granite, metamorphic rocks, lignites, monazite sand, and phosphate deposits typically contain uranium. Before it is transported into water, however, it must be oxidized. [586] The abundance of uranium isotopes found in the Earth's crust is typically not duplicated in ground water. U-234 is enriched in water when standardized to U-238. While more prevalent in ground water, uranium can be found in both ground and surface water. [586]

Emitted particles ionize or destabilize atoms as they pass thru the body's cells damaging chromosomes, which can lead to cancer. In addition to radiotoxicity, exposure to elevated uranium levels in drinking water may lead to kidney failure (chemical toxicity). [585] Uranium is regulated in drinking water due to its chemical and radio toxicity. [584]

Uranium is regulated by USEPA in drinking water with a maximum contaminant level of 30 µg/L. [584] USEPA has identified ion exchange, lime softening, reverse osmosis, and enhanced coagulation/filtration as Best Available Technologies (BATs) for the control of uranium in drinking water. [566]

In the National Inorganics and Radionuclides Survey (NIRS) of ground waters, uranium detects exceeded the detection level of 0.08 µg/L in 72.2 percent of 978 sites. The median, mean and maximum levels were, respectively, 0.53, 2.6 and 88.2 µg/L. [587]

Date of Literature Search: June 2009



566 USEPA; 2002; Implementation Guidance for Radionuclides; Implementation Guidance for Radionuclides; EPA-816-F-00-002. Office of Ground Water and Drinking Water, USEPA, Washington, DC.
584 USEPA; 2007; Basic information about radionuclides in drinking water; http://www.epa.gov/safewater/radionuclides/basicinformation.html; As posted on August 27, 2007. Office of Ground and Drinking Water, USEPA, Washington, DC.
585 USEPA; 2007; Technical fact sheet: final rule for (non-radon) radionuclides in drinking water; http://www.epa.gov/safewater/radionuclides/regulation_techfactsheet.html; As posted on August 27, 2007. Office of Ground and Drinking Water, USEPA, Washington, DC.
586 USEPA; 2000; Radionuclides Notice of Data Availability: Technical Support Document; Radionuclides Notice of Data Availability: Technical Support Document; Targeting and Analysis Branch Standards and Risk Management Division, Office of Ground Water and Drinking Water, US EPA, Washington, DC.
587 Longtin, J.; 1988; Occurrence of radon, radium and uranium in groundwater; J. AWWA; 80:7:84



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