Sensory irritation potential of selected nasal tumorigens in the rat.

Several important chemicals, including formaldehyde, 1,4-dichloro-2-butene, bis-chloromethyl ether, hexamethylphosphoramide, and epichlorohydrin have been shown to produce nasal tumours in rats following repeated or continuous inhalation exposures. Some of these compounds are respiratory irritants. To determine whether there is a correlation between the ability of a chemical to produce sensory irritation and to elicit nasal tumours, the atmospheric concentration causing a 50% decrease in the respiratory rate (RD50) of male rats was determined. Three other nasal tumorigens, dimethylcarbamoyl chloride, 2,3,4-trichloro-1-butene and 1,2-ethoxy-3-phenoxypropane, were also studied. No correlation between sensory irritation potency and nasal tumorigenic potential was observed. The most potent nasal tumorigen hexamethylphosphoramide, which produces tumours in rats following 12 months' continuous exposure to 50 ppb, failed to cause any decrease in respiratory rate when tested at 351 ppm (an aerosol exposure level which exceeds atmospheric saturation by approximately ten times).