Tetrachloroethylene is a nonflammable colorless liquid. Other names for tetrachloroethylene include perchloroethylene, PCE, PERC, tetrachloroethene, and perchlor. Tetrachloroethylene is used as a dry cleaning agent and metal degreasing solvent. It is also used as a starting material (building block) for making other chemicals and is used in some consumer products. It has also been used in water repellants, paint removers, printing inks, glues, sealants, polishes, and lubricants. Tetrachloroethylene has been in commercial use since the early 1900s. Tetrachlorethylene has been suspected of causing some types of cancer, based on both human and animal evidence. Laboratory studies have found that ingesting or inhaling tetrachlorethylene increased the risk of liver cancer in mice. In rats, inhaling tetrachloethylene was linked to kidney cancer and a rare type of leukemia. EPA has classified tetrachloroethylene as likely to be carcinogenic to humans by all routes of exposurebased on suggestive evidence in epidemiological studies and conclusive evidence in rats (mononuclear cellleukemia) and mice (increased incidence of liver tumors). The International Agency for Research on Cancer(IARC) has classified tetrachloroethylene as probably carcinogenic to humans (Group 2A).

Diftalone is a symmetrical tetracyclic compound with anti-inflammatory and antipyretic activities. The anti-inflammatory potency of diftalone is greater than that of aspirin, approximately equal to that of phenylbutazone, but lower than that of indomethacin. Diftalone exhibited limited but statistically significant antipyretic activities. It less potent than aspirin or phenylbutazone. Diftalone seems to be an effective and safe anti-inflammatory agent in the treatment of rheumatoid arthritis. It demonstrated the same activity as indomethacin and phenylbutazone. However, because of hepatotoxicity and carcinogenicity (hepatoma) in preclinical studies and hemotoxicity and gastrointestinal adverse effects in humans, diftalone was withdrawn by its manufacturer.