Carc inogenic i ty Study with Technica l - Grade Dichlorodiphenyltr ichloro - ethane and 1 , 1 - Dichloro - 2 , 2 - bis

Studies conduc ted by o thers have revealed that 1 ,1 -d ich lo ro2 ,2 -b i s (p -ch lo ropheny l )e thy lene (DDE), a proximal metabol i te of d ich lo rod ipheny l t r i ch lo roe thane (DDT), is a st rong hepatocel lu lar ca rc inogen in mice. Since hamsters appear to be resistant to tumor induct ion by DDT, we wanted to invest igate whe the r DDE has any neoplast ic ef fect in this species. DDE (99% pure) was mixed into the diet at doses of 500 or 1 0 0 0 ppm and given to g roups of male and female Syrian go lden hamsters for life. Ano ther g roup of animals received a diet conta in ing 1000 ppm techn ica l -g rade DDT, and a fur ther g roup served as control . Groups conta ined a minimum of 40 hamsters per sex. The tested c o m p o u n d s had no ef fect on the inc idence of tumors at all sites, compared to contro ls . A speci f ic f inding in animals exposed to DDE was the appea rance of hepatoce l lular tumors late in life. They were c lassi f ied as neoplast ic nodules, and the inc idence was 15% in females and 4 7 % in males of the 500 -ppm DDE dose g roups and 21% in females and 3 3 % in males of the 1 0 0 0 p p m DDE dose groups. None of the unt reated or DDT-t reated animals had these tumors. Eight animals t reated with 1 0 0 0 ppm DDE and four of those t reated with DDT had hyperp las t ic foci of the liver. In addit ion, adrenocor t ica l adenomas, spon taneous to Syr ian go lden hamsters, were more f requent in DDEand DDT-t reated animals than in contro l animals. These resul ts showing that DDE, but not its parental compound, induces liver cell tumors in hamsters emphas ize the impor tance of this metabol i te as a proximal ca rc inogen of DDT.