Application of neurophysiological methods in occupational medicine in relation to psychological performance.

Many years ago, we introduced advanced neurophysiological and psychobehavioural methods to our laboratory and have since applied our techniques on workers exposed to various occupational factors. In this article, we summarized our recent findings on the neurophysiological subclinical effects of lead, mixed solvents, toluene, styrene, local vibration and visual display terminal (VDT) work in relation to psychobehavioural effects. The methods used were as follows: 1) cerebral evoked potentials, i.e. short-latency somatosensory and visual evoked potentials (SSEP and VEP) and brainstem auditory evoked potential (BAEP), 2) event-related potential (P300), 3) psychological performance test, 4) computerized static posturography, 5) electrocardiographic R-R interval variability (CVRR), 6) distribution of nerve conduction velocities (DCV), and 7) conventional nerve conduction velocity (NCV). The following results were obtained: 1) Delay in SSEP latency in lead workers, in VEP latency in lead and VDT workers, in BAEP latency in vibrating tool workers and in P300 latency in lead workers, as well as significant correlations of P300 latency with blood lead concentrations in lead workers and of BAEP latency with length of work in brush saw operators; 2) Increase in postural sway and its significant correlation with urinary hippuric acid in toluene workers; 3) Decrease in CVRR in lead, mixed solvent, toluene, styrene and vibrating tool workers, and a significant correlation of the CVRR with length of exposure in mixed solvent workers; 4) Slowing of faster nerve fibre conduction in DCV and of NCV in lead, mixed solvent, styrene and vibrating tool workers, and their correlations with blood lead and length of work in lead and chain saw operators, respectively; 5) Decrease in the score on picture completion test in lead and styrene workers and its correlation with blood lead in lead workers. These findings suggest that recent advances in neurophysiological methods have enabled the detection of subclinical effects of various occupational and environmental factors.