Nerve conduction velocity studies of workers employed in the manufacture of phenoxy herbicides

Conduction velocities (NCV) of the median motor, median sensory, and sural nerves were measured in 56 workers employed in the manufacture of 2,4,5-trichlorophenoxy acetic acid (2,4,5-T) and 2,4-dichlorophenoxy acetic acid (2,4-D). Mean age was 35 years and mean duration of employment was 7 years. The control group consisted of 25 subjects without exposure to neurotoxic agents. When compared with controls, slowing was noted in the sural nerve (mean = 34.0 vs 40.1 m/sec, P > 0.02). All values were then adjusted for age and temperature and were transformed to Z values (mean = 0, standard deviation = 1), where-upon slowing was seen in the sural (?2.21 vs ?0.52, P < 0.0001) and median motor nerves (0.19 vs 0.91, P < 0.03). Duration of employment was significantly correlated with slowing of sural velocity (r = ?0.40, P < 0.004). Altogether, 46% of the study group had one or more slowed nerve conduction velocity, versus 5% of the control group P < 0.001).