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

[Abstract]: [Objectives]: We conducted a 6-year cohort study to evaluate the relationship between carbon disulfide (CS2) 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 CS2 exposure during the follow-up period (ex-exposed workers). MCV and SCV were measured at baseline and followed up. CS2 personal exposure concentration was measured two times a year during a 6-year follow-up period and mean (range) CS2 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 CS2 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 CS2 on SCV around a mean exposure level of 4 ppm may be reversible, since it disappeared in the ex-exposed workers after CS2 exposure cessation for a mean period of 4.1 years.