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PERCHLORATE [8]
CASRN: Various CASRN numbers for different chemical species

Update: May 2004

Current Massachusetts Regulatory Limit
MMCL = 0.002 mg/L. The ORS MMCL for perchlorate is directed at the sensitive subgroups of pregnant women, infants, children up to the age of 12, and individuals with hypothyroidism. They should not consume drinking water containing concentrations of perchlorate exceeding 0.002 mg/L. It is recommended that no one consume water containing perchlorate concentration greater than 0.018 mg/L.

Federal Regulatory Limit
The U.S. EPA has not published an MCL for perchlorate.

Basis for Criteria
ORS developed a health-based ORS MMCLG (Massachusetts Maximum Contaminant Level Goal) for perchlorate of 0.00049 mg/L based on the RfD derived by ORS of 0.00007 mg/kg/day. The RfD was based on iodide uptake inhibition in healthy, iodine-sufficient adult subjects. The calculation assumes that a 70 kg adult ingests 2 L/day of water. A relative source contribution factor of 20% is incorporated into the final value.

RfD: 0.00007 mg/kg/day (MassDEP, 2004)
UF: 300 MF: 1

An MMCL of 0.002 mg/L was identified based on feasibility and cost considerations. Perchlorate has been found to be a byproduct of the drinking water disinfection process and thus may be present in treated waters at low concentration. As is typically done with drinking water contaminants that are present in water a result of treatment to address pathogens, comparative risks were considered in establishing the MMCL of 0.002 mg/L. Other considerations included the analytical feasibility of detecting low levels and the cost considerations of cleanup.

Critical Effects
Perchlorate disrupts normal function of the thyroid gland. It interferes with iodide transport into the thyroid gland, decreasing the availability of iodide needed for the synthesis of thyroid hormones, which are essential for metabolism and normal growth and development. The effects caused by perchlorate are expected to be similar to those caused by iodine deficiency in humans, including impairment in physical development, behavior, movement, speech, hearing, vision and intelligence. Other possible symptoms include hypothyroidism, enlargement of the thyroid gland, and impaired brain development and lower IQ in children. The greatest impacts of perchlorate exposure are on pregnant women, developing fetuses, infants, children and individuals with low levels of thyroid hormones. Rats and mice chronically exposed to high concentrations of perchlorate produced thyroid tumors (Pajer and Kalisnik, 1991; Kessler and Kruskemper, 1966; Argus Research Laboratories, Inc., 1999). A number of genotoxicity assays have indicated that perchlorate is not mutagenic, suggesting a non-genotoxic mechanism of carcinogenesis.

Cancer Assessment: The U.S. EPA has not classified perchlorate under either the old U.S. EPA carcinogen classification system or under their Proposed Guidelines for Carcinogen Risk Assessment (U.S. EPA, 1999a). Using the 1999 proposed guidelines, ORS would tentatively classify perchlorate as having suggestive evidence of carcinogenicity but not sufficient to assess human carcinogenic potential.

Class
Inorganic

Analytical Information
PQL
: Less than 0.001 mg/L

Analytical Methods
U.S. EPA Method 314.0, revision 1.0 (U.S. EPA, 1999b)

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 http://www.epa.gov/safewater/methods/methods.html.

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 http://www.epa.gov/safewater/methods/methods.html.

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.

References
Argus Research Laboratories, Inc. 1999. Oral (drinking water) two-generation (one litter per generation) reproduction study of ammonium perchlorate in rats. Protocol no. 1416-001. Argus Research Laboratories, Inc., Horsham, PA.

Greer MA, Goodman G, Pleus RC, and Greer SE. 2002. Health effects assessment for environmental perchlorate contamination: The dose-response for inhibition of thyroidal radioiodine uptake in humans. Environ Health Perspect. 110:927-37.

Kessler, F.J., Kruskemper, H.J. 1966. Experimentelle Schilddrusentumoren durchmehrjahrige Zufuhr von Kaliumperchlorat. [Experimental thyroid tumors caused by long-term administration of potassium perchlorate.] Klin Wochenschr. 44:1154-1156.

MassDEP (Massachusetts Department of Environmental Protection). May 2004. Perchlorate Toxicological Profile and Health Assessment. Office of Research and Standards. Boston, MA.

Pajer, Z., Kalisnik, M. 1991. The effect of sodium perchlorate and ionizing radiation on the thyroid parenchymal and pituitary thyrotropic cells. Oncology. 48:317-320.

U.S. EPA (U.S. Environmental Protection Agency). July 1999a. Guidelines for Carcinogen Risk Assessment. Review Draft. NCEA-F-0644. Risk Assessment Forum.

U.S. EPA (U.S. Environmental Protection Agency). November 1999b. Method 314.0, Determination of Perchlorate in Drinking Water Using Ion Chromatography.


[8] The MCL is directed at the sensitive subgroups of pregnant women, infants, children up to the age of 12, and individuals with hypothyroidism. They should not consume drinking water containing concentrations of perchlorate exceeding 0.002 mg/L. MassDEP recommends that no one consume water containing perchlorate concentrations greater than 0.018 mg/L.