Abstract

OBJECTIVES
The effect of chronic exposure to low levels of n-hexane on peripheral nervous system and the relationship between duration of employment and impairment of peripheral nervous system was studied.
METHODS
In 21 workers at two shoe - maker factories and 21 unexposed controls, measurement of exposure of solvents, symptom Questionnaire, physical examination and electrophysiological study were conducted.
RESULTS
Mean ages of study subjects in the exposed and the unexposed were 39.9 and 40.1 years old. Mean durations of employment were 15.1 and 10.0 years, respectively. Mean concentraions of urinary 2,5-HD were 2.23 mg/kg creatinine, 0.23 mg/kg creatinine, respectively. Mean concentration of solvents in air were 21.1 ppm of n-hexane, 72.2 rpm of toluene and 0.5 ppm of MEK. There were no differences in the prevalence of subjective symptoms and abnormal neurological signs between the exposed and the unexposed. But vibration extinction time(VAT) of the exposed(8.8 second) was shorter than that of the unexposed(11.9 second)(p < 0.05). Mean values of electrophysiological studies(EPS) of the two groups were within normal limit. However, mean conduction velocity of median motor nerve and median F wave(MMNCV and MFCV), mean amplitude of median sensory action potential(MSAP) were decreased in the exposed(p < 0.05). Moreover, the rate of abnormal finding more than one in sensory nerves wart increased in the exposed than those in the unexposed(p,0.05). Correlation coefficients between duration of employment and mean conduction velocity of median sensory nerve (MSNCV) and between duration of employment and MFCV were -0.57 -0.43, respectively(p < 0.05).
CONCLUSIONS
These results showed that chronic (mean 15 years) low level(mean 23 ppm) exposure to n-hexane cause subclinical impairment of peripheral nervous system. These results also suggest that the longer duration of employment, the shorter values of EPB and VAT.