Update: August 1993
Current Massachusetts Regulatory Limit
MMCL = 4 mg/L (51 FR 11396; 4-2-86).
Federal Regulatory Limit
The MCL is equal to the MCLG of 4 mg/L. U.S. EPA set a secondary standard of 2 mg/L to prevent the majority of cases of water-related objectionable dental fluorosis while allowing for the beneficial effect of the reduced incidence of dental caries (51 FR 11396).
Basis for Criteria
The MCLG is based on the results of epidemiological studies of crippling skeletal fluorosis. The MCL was derived on the U.S. EPAâ€™s determination that the best technology generally available (BTGA) for removing fluoride from public water supplies is capable of reaching the MCLG of 4 mg/L (51 FR 11396).
The MCLG is based on prevention of crippling skeletal fluorosis. Based on a report by the U.S. Surgeon General, crippling skeletal fluorosis is an adverse effect resulting from intakes of fluoride of 20 mg/day over periods of 20 years or more. For an individual ingesting 2 L drinking water per day, this daily dose would correspond to a fluoride drinking water concentration of 10 mg/L. In studies conducted in other countries, levels of fluoride in drinking water between 10-40 mg/L have been associated with rheumatic attack, pain and stiffness, as well as crippling skeletal fluorosis in a large number of individuals. U.S. EPA concluded that the MCL of 4 mg/L, which includes a safety factor of less than 10, would be protective against crippling skeletal fluorosis with an adequate margin of safety (50 FR 47141; 51 FR 11396).
The U.S. EPA agrees with findings of the Knox Report (the Working Party on the Fluoridation of Water and Cancer) commissioned by the government of Great Britain (Knox, 1985), which concludes that "nothing in any of the major classes of epidemiological evidence which could lead us to conclude that either fluoride occurring naturally in water, or fluoride added to water supplies is capable of inducing cancer or of increasing the mortality from cancer".
PQL: 0.5 ug/L
340.2; ion selective electrode
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 http://www.epa.gov/iris/. 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. April 30, 1985. Environmental Protection Agency. 40 CFR Part 141. National Primary Drinking Water Regulations; Fluoride; Proposed Rules. (50 FR 20164).
Federal Register. November 14, 1985. Part II. Environmental Protection Agency. 40 CFR Parts 141, 142, and 143. National Primary Drinking Water Regulations; Fluoride; Final Rule and Proposed Rule. (50 FR 47141).
Federal Register. April 2, 1986. 40 CFR Parts 141, 142, and 143. National Primary and Secondary Drinking Water Regulations; Fluoride; Final Rule. (51 FR 11396).
Hodge, H.C. 1950. The concentration of fluorides in drinking water to give the point of minimum carries with maximum safety. J. Am. Dent. Assoc. 40:436. Cited in: Underwood, E.S. 1977. Trace Elements in Human and Animal Nutrition. Academic Press. NY.
Knox, E.G., "Fluoridation of Water and Cancer: A Review of the Epidemiological Evidence," Report of the Working Party on Fluoridation of Water and Cancer, London: Her Majestyâ€™s Stationery Office, 1985.