Electrophysiological investigation of central, peripheral and autonomic nerve function in workers with long-term low-level exposure to carbon disulphide in the viscose industry

Abstract

Objective: Neurotoxicity of carbon disulphide (CS₂) is well known. The air concentration at the workplace at which such adverse effects can first be observed is the subject of controversial discussion. Methods: In a cross-sectional study on CS₂-exposed workers peripheral motor and sensory nerve conduction studies, somatosensory evoked potentials, thermotesting and investigation of forced respiration sinus arryhtmia have been carried out. The data from 222 workers exposed to CS₂ in the viscose industry were evaluated and compared with data from 191 employees from the same factory with similar physical and psychological stress factors but without detectable occupational contact to neurotoxic substances. Median exposure to CS₂ was below the currently valid occupational-medical threshold limit value (MAK-value) of 10 ppm. Multiple linear or multiple logistic regression analysis was used to check for statistical differences. Results: Binary evaluation (comparison of exposed persons versus controls after multiple linear regression) revealed a slightly lower value in the exposed group for the motor nerve conduction velocity (MNCV, –0.76 m/s, median 48 m/s), but a long way from pathological thresholds. No dose-response relationship could be found within the exposed group for any evaluation criteria of CS₂-exposure. Somatosensory evoked potentials, thermotesting and analysis of heart rate variability yielded no indication of a neurotoxic effect of CS₂. Conclusion: Isolated decrease of MNCV in binary evaluation is, with regard to the known mechanism of CS₂-neurotoxicity and the lack of a dose-response relationship, obviously not due to toxic effects. We interpret our results as showing that an adverse effect of carbon disulphide at the exposure ranges found was not detectable in the exposed group.