WASHINGTON Naphthalene, which gives mothballs and public restroom deodorizers their distinctive aroma, causes cancer in rats, U.S. government researchers said. Rats who breathed naphthalene fumes developed cancer at a rate high enough to worry scientists at the National Toxicology Program (NTP), who must now decide whether people have the same risk. The rats especially developed rare cancers in the nose, the researchers found. "The rats in the study were exposed by inhalation, just as most people are, in doses comparable to some human consumer and workplace exposures," the National Institute of Environmental Health Sciences, which administers the NTP, said in a statement. The Occupational Safety and Health Administration, Environmental Protection Agency and other agencies suggested the tests after some German workers exposed to naphthalene developed cancers including larynx, gastric, nasal, and colon cancer. The report was the 500th issued by the NTP using laboratory rats. "Since NTP was established in 1978, its reports have changed how substances are handled in occupational and home settings, and in the more general environment," it said in a statement. Some chemicals restricted because of its tests include tetrachloroethylene and carbon tetrachloride, once used in home cleaning fluids; mirex, which was restricted in its use as a pesticide and fire retardant; benzene, an ingredient in gasoline, and phenolphthalein, once an active ingredient in most over-the-counter laxatives. "Unlike the old cliche that everything causes cancer', almost half the chemicals tested do not produce tumors in laboratory rodents, and with a few rare exceptions, chemicals that cause tumors or other diseases in rodents eventually are found to cause similar if not identical problems in humans," the NTP said.

(Reuter)