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RADIUM 226 and 228
CASRN: 7440144

Update: May 2004

Current Massachusetts Regulatory Limit
MMCL = 5 pCi/L. ORS has adopted the MCL published by the U.S. EPA (65 FR 76708).

Federal Regulatory Limit
The MCL for radium 226 and 228 is 5 pCi/L.

There is no MCLG for Radium 226 and 228 since MCLGs were not established before the 1986 Amendments to the Safe Drinking Water Act.

Basis for Criteria
U.S. EPA has retained the MCL of 5 pCi/L proposed when the radionuclides rule was first promulgated in 1976. In 1991, new, higher MCLs were proposed for these isotopes. However, a more current risk analysis, conducted based on new data contained in the U.S. EPA Federal Guidance Report-13, indicated that the risks associated with these higher proposed MCLs were well above the U.S. EPA target excess lifetime risk (ELCR) range of 10-6 - 10-4. Thus, the MCL for both radium isotopes together is finalized as 5 pCi/L, which brings the risk associated with this MCL within U.S. EPA's target ELCR range for carcinogens.

Critical Effects
Radium 226 and 228 emit alpha radiation. All alpha radiation is considered to have the potential to cause cancer as a result of its interaction with genetic material. A number of human epidemiological studies indicate increasing risks of various types of cancer associated with increasing doses of ionizing radiation. The cancers produced by radiation cover the full range of carcinomas and sarcomas. Every form of cancer has been shown to be induced by radiation (56 FR 33050).

Cancer Assessment: Group A
Bone sarcomas and head carcinomas were seen in workers (e.g., radium dial painters) occupationally exposed via ingestion to paints containing radium-226. Similar findings were seen with radium-228 exposures, although head carcinomas are not believed to be associated with ingestion of radium-228. Supporting studies for these findings include a number of other studies, in which humans or animals injected with various radium isotopes had an increased incidence of cancer.


Analytical Information
: (radium-226) 1 pCi/L
          (radium-228) 1 pCi/L

Analytical Methods
U.S. EPA 903.0; radiochemical
U.S. EPA 904.0; radiochemical
U.S. EPA 903.1; radon emanation

PQLs and analytical methods may have been updated since this guidance value was last revised. Updated analytical methods for drinking water and their associated PQLs may be found at US EPA Drinking Water Analytical Methods .

Other Regulatory Data
Any Health Advisories, Reference Doses (RfDs), cancer assessments or Cancer Potency Factors (CPFs) referenced in this document pertain to the derivation of the current guidance value. Updated information may be obtained from the following sources:

Health Advisories - The U.S. EPA provides guidance for shorter-term exposures for chemicals based on their non-cancer effects. Current health advisories may be more current than those used to derive MCLs and may be found at US EPA Current Drinking Water Health Advisories .

RfDs, cancer assessments and CPFs - For specific information pertaining to derivation of drinking water criteria, consult the Federal Register notice that announces the availability of the most current guidance for that chemical. In addition, information on other current RfDs and CPFs as well as cancer assessments for specific chemicals may be found in the U.S. EPA Integrated Risk Information System (IRIS) at Please note that the information in IRIS may differ from that used in the derivation process as published in the Federal Register notice.

Federal Register. December 7, 2000. Part II. Environmental Protection Agency. Parts 9, 141, and 142. National Primary Drinking Water Regulations; Radionuclides; Final Rule. (65 FR 76708).

Federal Register. April 21, 2000. Part IV. Environmental Protection Agency. 40 CFR Parts 141 and 142. National Primary Drinking Water Regulations; Radionuclides; Notice of Data Availability; Proposed Rule. (65 FR 21576).

Federal Register. July 18, 1991. Part II. Environmental Protection Agency. 40 CFR Parts 141 and 142. National Primary Drinking Water Regulations; Radionuclides; Proposed Rule. (56 FR 33050).

U.S. Environmental Protection Agency. September 1999. Cancer Risk Coefficients for Environmental Exposure to Radionuclides. Federal Guidance Report No. 13. Air and Radiation. U.S. EPA-402-R-99-001.