Peripheral nervous system functions of workers exposed to n-hexane at a low level

In order to assess the effects on the peripheral nervous system of n-hexane at a low level, an epidemiological study using a questionnaire, neurological examinations, and neurophysiological studies was carried out on two age-matched groups; one, consisting of 14 exposed workers and the other, of 14 control workers. The 8 h time weighted average of n-hexane concentration in the exposure environment was 58 +/- 41 (mean +/- SD) ppm. In the individual worker, no obvious signs could be found indicating damage to the nervous system that were referable to the n-hexane exposure. On the other hand, when the subjects were taken in groups, the results obtained from the exposed group showed a minor partiality for functional impairment of the peripheral nervous system in many test items. In particular, statistically significant differences between the two groups were detected in the following items: (1) inquiries by questionnaire for persistent or transient symptoms regarding muscle weaknesses and dyesthesia of limbs; (2) the jump test on one foot; (3) the tuning fork test for vibration sensation on the radial processes; (4) the maximal velocity and the residual latency of motor nerve conduction of the posterior tibial nerve. In conclusion, it is not likely that at exposure levels less than the current threshold limit value of 100 ppm proposed by ACGIH, n-hexane may induce clinically overt polyneurophathy. However, there is no gainsaying the possibility that in the exposed workers as a whole, small cumulative effects in the peripheral nervous system may be brought about by long-term n-hexane exposure less than 100 ppm.