A 13-week vapor inhalation study of n-hexane in rats with emphasis on neurotoxic effects

Male and female Fischer 344 rats were exposed to 0-, 3000-, 6500-, or 10,000-ppm n-hexane vapors 6 hr per day, 5 days per week, for 13 weeks. The 13-week exposures had no adverse effect on the growth of female rats. However, the mean body weight gain of male rats in the 10,000-ppm group was significantly lower than for controls at 4 weeks of exposure and thereafter. In addition to the depression of body weight gain, the male exposed to 10,000 ppm had slightly but significantly lower brain weights at necropsy. No adverse testicular effects were noted. Axonopathy was observed in the tibial nerve in four of five male rats from the 10,000-ppm group and one of five male rats in the 6500-ppm group and in the medulla from one male rat in the 10,000-ppm group. These axonal changes were detectable only in teased nerve fiber preparations or in Epon embedded specimens. Histopathologic studies on Formalin fixed tissues did not reveal any lesions that were attributed to n-hexane exposure.