n-Hexane-'free' hexane mixture fails to produce nervous system damage

The occurrence of neurological disease in humans exposed repeatedly to high levels of commercial hexane has been well-documented. Chronic exposure of rats to elevated levels of n-hexane, a component in commercial hexane, will also cause polyneuropathy. No evidence was available, however, regarding the neuropathogenic potential of the other aliphatic and alicyclic hydrocarbon components of commercial hexane. This study reports that rats exposed 22 hours per day for periods up to six months at a concentration of 500 ppm of an n-hexane-'free' hexane mixture gave no evidence of neurotoxic effects. A second group of rats exposed to 100 ppm of methyl n-butyl ketone, the positive control, developed histological evidence of peripheral neuropathy after four months of continuous exposure. Finally, rats exposed to 500 ppm of methyl ethyl ketone, the negative control, did not develop any indication of polyneuropathy.