Gaseous Formaldehyde and Hydrogen Chloride Induction of Nasal Cancer in the Rat2

Abstract

The carcinogenic response to the combined and separate exposures to formaldehyde (HCHO) and hydrochloric acid (HCI) was investigated in male inbred SD rats. The rats were exposed to gaseous HCHO, 14 ppm, and HCI, 10 ppm, in two experiments. In one experiment the gases were premixed at high concentrations before being diluted in the exposure chamber air to maximize the formation of the carcinogen bis(chloromethyl)ether (BCME). In the second experiment exposure was repeated to HCI and HCHO premixed at high concentrations, and not premixed (to minimize BCME formation), as well as to HCHO alone and HCI alone. The second experiment is being reported on at an interim stage. HCHO alone induced squamous carcinomas of the nasal cavity as did the combined exposures to HCHO and HCI. No carcinogenic response was observed with HCI alone. HCHO accounted for most, if not all, of the carcinogenic activity of the mixture of HCHO-HCI.