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Radium

Overview
 
CAS Number: 13982-63-3
Synonyms: Ra-226, Ra-228
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. Radium has two radionuclides that are detected in and regulated in drinking water. Ra-226 is an alpha emitter and the fifth-member decay product of the uranium-238 series. Its half life approximately 1622 yrs. Ra-228 is a beta emitter and the second-member decay product of the thorium-232 series. Its half life is approximately 5.7 yrs. Long half lives lead to their stability in water. Ra-224 is an alpha emitter and the fifth-member decay product of the thorium-232 series. Its half life approximately 3.6 days. [586] Ra-224 is not regulated in drinking water.

Radium is naturally occurring and depends, in part, on the solubility of the parents and decay products ahead of it in its decay series. [586] Radium can adsorb to particulate surfaces. In ground waters, high total dissolved solids offer other ions, particularly divalent cations like calcium and barium, competing for sorption sites that keep radium in solution. [586] Deep wells have limited sorption sites, therefore are more likely to have radium in solution than shallow wells. [586] Radionuclides are detected more frequently in ground water than in surface water. [585] Radium detections in surface water are related to discharges from ground waters or from man-made activities. [586]

Emitted particles ionize or destabilize atoms as they pass thru the body's cells damaging chromosomes that can lead to cancer. [585] Radium is regulated in drinking water because of its increased risk of cancer. [584]

Combined Ra-226 and Ra-228 are regulated by USEPA in drinking water with a maximum contaminant level of 5 pCi/L. [584] USEPA has identified ion exchange, lime softening and reverse osmosis as Best Available Technologies for the control of Ra-226 and Ra-228 in drinking water. [566]

In the National Inorganics and Radionuclides Survey (NIRS) of ground waters [587], Ra-226 detects exceeded the detection level of 0.18 pCi/L in 40.2 percent of 989 sites. The median, mean and maximum levels were, respectively, 0.40, 0.87 and 15.1 pCi/L. Also in the NIRS, Ra-228 detects exceeded the detection level of 1.0 pCi/L in 11.9 percent of 987 sites, and the median, mean and maximum levels were, respectively, 1.47, 2.05 and 12.1 pCi/L. Ref 586 cites a USGS survey of 104 ground water sites in the US known or suspected of having high radium levels. The Ra-226 median, mean and maximum levels were, respectively, 0.4, 1.6 and 16.9 pCi/L, and the Ra-228 levels were, respectively, 0.5, 2.1 and 72.3 pCi/L.

Date of Literature Search: March 2007



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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