reached in the review process. The other sections contain U.S. EPA 

 information which is specific to a particular EPA program and has 

 been subject to review procedures prescribed by that Program Office. 

 The regulatory actions in Section IV may not be based on the most 

 current risk assessment, or maybe based on a current, but unreviewed, 

 risk assessment, and may take into account factors other than health 

 effects (e.g., treatment technology). When considering the use of 

 regulatory action data for a particular situation, note the date of the 

 regulatory action, the date of the most recent risk assessment relating 

 to that action, and whether technological factors were considered. 

 Background information and explanations of the methods used to 

 derive the values given in IRIS are provided in the five Background 

 Documents in Service Code 5. 



Status or data for gamma-Hexachlorocyclohexane (gamma-HCH). 



Category (section) Status Last Revised 



Oral RfD Assessment (I.A.) on-line 03/01/88 



Inhalation RfD Assessment (I.B.) no data 



Carcinogenicity Assessment (II.) pending 



Drinking Water Health Advisories (III.A.)on-line 03/01/88 



U.S. EPA Regulatory Actions (IV.) on-line 03/01/88 



Supplementary Data (V.) on-line 01/31/87 



I. CHRONIC HEALTH HAZARD ASSESSMENT FOR NONCAR- 

 CINOGENIC EFFECTS 



Substance Name - gamma-Hexachlorocyclohexane (gamma-HCH) 

 Primary Synonym -- Lindane 

 CASRN - 58-89-9 

 Last Revised - 03/01/88 



The Reference Dose (RfD) is based on the assumption that thresholds 

 exist for certain toxic effects such as cellular necrosis, but may not exist 

 for other toxic effects such as carcinogenicity. 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 sub- 

 groups) that is likely to be without an appreciable risk of deleterious 

 effects during a lifetime. Please refer to Background Document 1 in 

 Service Code 5 for an elaboration of these concepts. RfDs can also be 

 derived for the noncarcinogenic health effects of compounds which 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 car- 

 cinogenicity, a summary of that evaluation will be contained in Section 

 II of this file when a review of that evaluation is completed. 



lA. REFERENCE DOSE FOR CHRONIC ORAL EXPOSURE 

 (RfDo) 



Ij\.1. oral RfD SUMMARY 



Critical Effect Experimental Doses* UF MF RfD 



Liver and kidney NOAEL: 4 ppm diet 1000 1 3E-4 



toxicity 3 (m/kg/day females) mg/kg/day 



Rat, Subchronic Oral LOAEL: 20 ppm diet 



Bioassay (1.55 mg/kg/day males) 



Zoecon Corp., 1983 



