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Update: May 2004

Current Massachusetts Regulatory Limit
The MMCL = the concentration which produces an annual dose of 4 millirem/year. ORS has adopted the MCL published by the U.S. EPA. 

Federal Regulatory Limit
The MCL for beta particles and photon emitters is a concentration which produces an annual dose of 4 millirem (mrem) effective dose equivalent (ede) per year (i.e., 4 mrem-ede) (65 FR 76708).

There is no MCLG for beta particles and photon 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 original MCL and methodology for deriving concentration limits for individual beta particles and photon emitters developed when the radionuclides rule was first promulgated in 1976. Appendix B of 56 FR 33050 lists the concentrations in pCi/L that correspond to 4 mrem-ede for each beta emitter, assuming lifetime intake of 2 L/day of drinking water. Based on the latest dosimetry model, as contained in U.S. EPA's Federal Guidance Report-13, the newest risk estimates for the beta emitter concentration limits fall within the U.S. EPA's target excess lifetime cancer risk (ELCR) range for drinking water contaminants of 104 - 10-6 (while some are slightly above and some are slightly below, all round to values within these orders of magnitude) (56 FR 33050).

Critical Effects
A number of human epidemiological studies indicate increasing risks of various types of cancer associated with increasing doses of ionizing radiation. The most notable of these studies pertain to the Japanese atomic bomb survivors. These results are supported by animal toxicological results (56 FR 33050). 

Cancer Assessment A
Beta particles and photon emitters are ionizing radiation that decays primarily by electron and photon emissions. U.S. EPA has classified ionizing radiation as a Group A human carcinogen. 


Analytical Information
: 4 pCi/L

Analytical Methods
U.S. EPA 900.0
SM 302
7110 B
USGS 1120-76

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

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

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.