Changes of median nerve conduction velocity in rayon manufacturing workers: A 6-year cohort study.

OBJECTIVES

We conducted a 6-year cohort study to evaluate the relationship between carbon disulfide (CS) exposure and reductions in the motor and sensory nerve conduction velocity (MCV and SCV) of the median nerve.

METHODS

Study subjects at baseline included 432 exposed workers and 402 unexposed workers. Among the exposed workers, 145 workers terminated CS exposure during the follow-up period (ex-exposed workers). MCV and SCV were measured at baseline and followed up. CS personal exposure concentration was measured two times a year during a 6-year follow-up period and mean (range) CS exposure concentrations (ppm) were 5.96 (0.8-16.0) and 3.93 (0.6-9.9) in the exposed and ex-exposed workers, respectively.

RESULTS

Reductions in MCV during the follow-up period did not differ among the exposed, ex-exposed, and unexposed workers. Reduction in SCV (m/s) of the exposed workers (-4.47±3.94) was significantly larger than that of the unexposed (-3.38±3.97) and ex-exposed workers (-3.26±3.79). For SCV reduction, a partial multiple regression coefficient of (ex-exposed workers) / (unexposed workers) was significantly positive (+0.915, p < 0.01) after adjustment for confounding variables.

CONCLUSIONS

This cohort study showed that 6-year CS exposure around a mean level of 6 ppm did not affect MCV reduction but induced significant SCV reduction beyond the influence of aging. The effect of CS on SCV around a mean exposure level of 4 ppm may be reversible, since it disappeared in the ex-exposed workers after CS exposure cessation for a mean period of 4.1 years.