Nerve function in workers with long term exposure to trichloroethene

Abstract

Certain functions of the nervous system were examined in 31 printing workers (mean age 44) exposed to trichloroethene (mean duration 16 years) and 28 controls (mean age 45). In the sural nerve the conduction velocity (SNCV), response amplitude, and refractory period (SRP) were measured. The latencies of the masseter and the blink reflex were determined to test the trigeminal nerve. In the peroneal nerve the conduction velocity of fast and slow nerve fibres, the response amplitude, and the refractory period were determined. As a measure of autonomic nerve function the response of the heart rate was determined to isometric muscle contraction and deep breathing. Individual cumulative exposure was calculated on the basis of exposure levels in the past. The mean cumulative exposure of the exposed workers was 704 ppm x years. For the assessment of the exposure effect relation a multiple linear regression model was used. A slight reduction (-1.1 m/s) in the SNCV was found and a prolongation (0.4 ms) of the SRP (mean of the controls 1.95 ms). The latency of the masseter reflex (mean 10.4 ms) had increased (0.4 ms). With respect to the blink reflex no prolongation was found. No impairment was found in the functions of motor and autonomic nerves. This study shows that the refractory period may be a sensitive indicator of preclinical toxic neuropathies. Long term exposure to trichloroethene at threshold limit values (about 35 ppm) may slightly affect the trigeminal and sural nerves.