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Update: May 2004

Current Massachusetts Regulatory Limit
MMCL = 15 pCi/L. ORS has adopted the MCL published by the U.S. EPA (65 FR 76708).

Federal Regulatory Limit
The MCL is equal to an adjusted gross alpha concentration of 15 pCi/L, calculated by excluding radon and uranium, but including radium 226.

There is no MCLG for alpha emitters 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 proposed in 1991 based on the newly estimated risk levels associated with this MCL. U.S. EPA used updated information on risk coefficients contained in U.S. EPA's Federal Guidance Report-13. The risk coefficients in this report were calculated using state-of-the art methods and models and are a significant improvement over the information used to support the 1991 radionuclides proposal. Concentrations of alpha emitters, assuming consumption of 2 L/day of drinking water each correspond to an excess lifetime cancer risk (ELCR) of 10-4. These concentrations are presented in Appendix C of 56 FR 33050.

Critical Effects
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: 

Alpha emitters release ionizing radiation during alpha decay. U.S. EPA has classified ionizing radiation as a Group A human carcinogen. There are also data on individual alpha emitters that indicate they are carcinogenic.


Analytical Information
: 3 pCi/L

Analytical Methods
U.S. EPA 00-02
SM 7110 C

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.