Conversion of p,p' -DDT to p,p' -DDD by intestinal flora of the rat

p,p-DDD 1,1-dichloro- 2,2-bis(p-chlorophenyl)-ethane] occurs in the feces and livers of rats, that are given p, p-DDT 1,1,1-trichloro-2,2-bis-(p-chlorophenyl)-ethane] by stomach tube, but not of rats injected intraperitoneally with p,p-DDT. Coliform bacteria, isolated from feces of control animals, can effect reductive dechlorination of p,p-DDT to p,p-DDD. These findings indicate that the normal flora of the gastrointestinal tract, rather than the liver, as others have suggested, is the major source of the p,p-DDD that is found in animals fed p,p-DDT.