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STATE OF CALIFORNIA DEPARTMENT OF HEALTH SERVICES TOXIC SUBSTANCES CONTROL PROGRAM TOXICOLOGY AND RISK ASSESSMENT UNIT SCIENTIFIC GUIDANCE MEMO 89-3 AUGUST 9, 1989 Page 2 of 8 PCDDs and PCDFs were present, and whether these impurities could account for the observed carcinogenic activities of4 � e two the grades of PCP• HandSCD hadoxicologists them a alyzed obtained PCDDs land PCDFs by NTP test articles the DHS Hazardous Materials Laboratory.and T ae much resultslesserextent revealed that technical grade PCP, EC-7 grade PCP, contained low levels of PCDDs and PCDFs. P test cles Comparisons of the tumorigenic d cin NTP le experimentty Of the al studies aof1TCDD with the tumor rates observed in (NTP, 1982) and HxCDDs (National Cancer Institute, 1PCDD and B6C3F1 mice have allowed the follo• e PCP may shave •contributed to PCDF contaminants in technical y-arade the liver cancer activity seen in the stevidencedy of lof the pCp, Therefore, this study presents equivocal ability of technical grade pentachlorophenol to induce liver cancer. Ds (2) Our ana?Y'rade^ of dPCP acould not account t the low levels of or CDiie and PCDFs in the EC g rade of PCP, as observed livery carcinogeeref activity wey concluded gthat this study shown in figu�e 1. - presents clear evidence of its own he carcinogenic Tipotential lusion pis grade pentachlorophenol in supported by: (a) PCDD and PCDF contaminants in EC-ac do vityt account for all of the observed liver care nogencancer i cc activities of and 2) in the experiments studying tumors were observed only to occur in the liver, whereas, HXCDDs , tumors were in the studies of both technical and E` oneochromccytomas of observed at other sites besides `io arcomas( of the circulatory the adrenal medulla, and hemang of EC-7 grade PCP demonstrates system) . In conclusion, the study that PCP is carcinogenic in its own right. he on Determinations of Applied A °inLaccordaevels nceswith TSect ion u4 . 51of of AALs for PCP were conductedTree (DHS , 1986) . Since the California Site Mitigation Decision no threshold level for PCP is considered to be a carcinogen, production of an adverse efc s prlocedures -oderive1a calculated using low-dose extrapolation F at a level of risk no greater than Maximum Exposure Level (ME1 eo le exposed. one excess cancer in a million p P The low-dose Description of uantitative Procedures: The GLOBAL86 (a extrapolation model of Crump (Howe et al , was co.,,puter program version of ,.he ultistage model) , linearized m used, in accordance with State level Californiaof extrar4skde equal tolines or 1985) , to calculate a MEL at exposure. less than one in a million for a lifetime ent( forlife year)e span was For t was assumed that no adjustment'^ ItFwas assumed O. PCPr 1 needed, since the data were from a chronic study.