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DALAPON (sodium salt)
CASRN: 75990

Update: August 1993

Current Massachusetts Regulatory Limit
MMCL = 0.2 mg/L. ORS has adopted the MCL published by the U.S. EPA as part of the Phase V rule (57 FR 31776: 7-17-92).

Federal Regulatory Limit
The MCL is equal to the MCLG of 0.2 mg/L.

Basis for Criteria
The MCLG is based on the RfD presented below and assumes that a 70 kg adult ingests 2 L/day of water. A relative source contribution factor of 0.2 is incorporated into the MCLG.

RfD: 3 x 10-2 mg/kg/day
UF: 300 (10 = interspecies; 10 = intraspecies; 3 = incomplete database on chronic toxicity)
MF: 1 Confidence in RfD: medium

In a study in which Paynter et al. (1960) exposed albino rats for two years to 5, 15 and 50 mg/kg/day of dalapon sodium, the average kidney weights of male rats at the highest dose showed a statistically significant increase compared to male controls. The level of 15 mg/kg/day was identified as a NOAEL for this study. Since the NOAEL was based on the sodium salt of dalapon that was 65% pure, the NOAEL was corrected to 8 mg/kg/day to represent the equivalent value for the pure acid.

Critical Effects
Dalapon is not known to cause health effects upon acute exposure, although it is readily absorbed and widely distributed throughout the body. Upon longer-term exposure to levels above the MCL, dalapon has the potential to cause an increased kidney to-body-weight.

Cancer Assessment: 
There is inadequate evidence to state whether dalapon has the potential to cause cancer from lifetime exposure in drinking water. U.S. EPA has classified dalapon as a Group D chemical.

chlorinated pesticide

Analytical Information
Analytical Methods
U.S. EPA Method 515.1; 552.1

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. July 25, 1990. Part II. Environmental Protection Agency. 40 CFR Part 141 et al. National Primary and Secondary Drinking Water Regulations; Synthetic Organic Chemicals and Inorganic Chemicals; Proposed Rule.

Federal Register. July 17, 1992. Part III. Environmental Protection Agency. 40 CFR Parts 141 and 142. National Primary Drinking Water Regulations; Synthetic organic Chemicals and Inorganic Chemicals; Final Rule. (57 FR 31776).

Paynter, O.E., Tusing, T.W., McCollister, D.D. and Rowe, V.K. 1960. Toxicology of Dalapon Sodium (2,2-Dichloropropionic Acid, Sodium Salt). Agric. Food Chem. 8:47-51.