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U.S.EPA IRIS Substance file-Norflurazon:CASRN 27314-13-2 hnp://www.epa.gov/ngispgm3/iris/subst/0082.htm _I. CHRONIC HEALTH HAZARD ASSESSMENTS FOR NONCARCINOGENIC EFFECTS _LA. REFERENCE DOSE FOR CHRONIC ORAL EXPOSURE (RfD) Substance Name -- Norflurazon CASRN -- 27314-13-2 Last Revised -- 04/01/1991 The oral Reference Dose (RfD) is based on the assumption that thresholds exist for certain toxic effects such as cellular necrosis. It is expressed in units of mg/kg-day. In general, the RfD is an estimate (with uncertainty spanning perhaps an order of magnitude) of a daily exposure to the human population (including sensitive subgroups) that is likely to be without an appreciable risk of deleterious effects during a lifetime. Please refer to the Background Document for an elaboration of these concepts. RfDs can also be derived for the noncarcinogenic health effects of substances that are also carcinogens. Therefore, it is essential to refer to other sources of information concerning the carcinogenicity of this substance. If the U.S. EPA has evaluated this substance for potential human carcinogenicity, a summary of that evaluation will be contained in Section II of this file. I.A.I. ORAL Rfl) SUMMARY Critical Effect Experimental Doses* OF MF RfD --------- ----------------------- ----- --- --------- Liver and thyroid NOEL: 150 ppm 100 1 4E-2 effects (3.75 mg/kg/day) mg/kg/day 6-Month Dog Feeding LEL: 450 ppm Study (10.25 mg/kg/day) Sandoz-Wander, 1973 *Conversion Factors: 1 ppm = 0. 025 mg/kg/day (assumed dog food consumption) _I.A.2. PRINCIPAL AND SUPPORTING STUDIES (ORAL RfD) Sandoz-Wander, Inc. 1973. MRID No. 00111618. Available from EPA. Write to FOI, EPA, Washington, DC 20460. Four groups of 4 male and 4 female beagle dogs were exposed to 0, 50, 150, or 450 ppm Norflurazon in the diet for 6-months. At 450 ppm, effects were seen in the liver and the thyroid. Liver effects were increased weights, of 7 5/15/00 11:14 AM