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CASRN: 122349

Update: August 1993

Current Massachusetts Regulatory Limit
MMCL = 0.004 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 0.004 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 drinking water. The MCLG incorporates a relative source contribution factor of 20% and a 10-fold uncertainty factor to account for potential carcinogenicity (55 FR 30370).

RfD: 5 x 10-3 mg/kg/day
UF: 100 (10 = interspecies; 10 = intraspecies)
MF: 1 Confidence in RfD: High

Critical Effects
Acute exposure to simazine for relatively short periods of time at levels above the MCL could result in weight loss and changes in blood. Chronic lifetime exposure to concentrations above the MCL may result in tremors; damage to testes, kidneys, liver and thyroid; gene mutations; and cancer.

A NOAEL of 0.5 mg/kg/day was identified from a two-year chronic feeding study in which rats were given 0, 10, 100 or 1000 ppm (corresponding to 0, 0.4, 4.2 or 45.8 mg/kg/day for males and 0, 0.05, 5.3 or 63.1 mg/kg/day for females) simazine in the diet. Significant reductions in body weight gain and hematology parameters were observed in females at 100 ppm. This NOAEL is supported by a one-year feeding study in which dogs were fed 0, 20 100 or 1250 ppm in the diet. A NOAEL of 20 ppm (corresponding to a dose of 0.7 mg/kg/day) was identified from this study. The NOAEL of 0.5 mg/kg/day from the rat study was used as the basis for the RfD above.

Cancer Assessment: C
U.S. EPA has classified simazine as a Group C carcinogen based on the presence of limited or equivocal evidence of carcinogenicity in animals in the absence of human data. Simazine has been found to produce mammary tumors in female rats. This classification is supported by the fact that both atrazine and propazine, two similar compounds also cause mammary tumors in the rat (55 FR 30370).

A carcinogenic potency for simazine of 1.2 x 10-1 was developed based on the incidence of mammary gland tumors in female Sprague Dawley rats. The MCLG of 0.004 mg/L corresponds to the theoretical cancer risk level of 1 x 10-5 (57 FR31776).


Analytical Information
: 0.001 mg/L

Analytical Methods
U.S. EPA Methods 505; 507; 508.1; 525.2

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. 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. (55 FR 30370)

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).

McCormick, GC, Arthur, AT and Green, JD. Ciba-Geigy Corporation. 1988. Simazine-technical: 104-week oral chronic toxicity and carcinogenicity study in rats. MRID Number: 406144-05. Study Number 2-0011-09. Testing Facility: Pharmaceuticals Division , Summit, NJ.

McCormick, GC and Green, JD. Ciba-Geigy Corporation. 1988b. Simazine-technical: A 52-week oral feeding study in dogs. MRID Number: 406144-02. Study Number: 87122. Testing Facility: Pharmaceuticals Division, Summit, NJ.