Electrophysiological findings in diphenyl poisoning

The fungistatic agent diphenyl caused fatal poisoning with signs of neurotoxicity in a worker in a Finnish paper mill. This initiated a neurophysiological study of 24 workers occupationally exposed to diphenyl. Ten men showed EEG abnormalities, mainly diffuse or generalized ones. The abnormalities persisted on re-examination one and two years later. Nine subjects had EMG abnormalities; seven also exhibited fibrillations in some muscles. One subject showed a long rhythmic series of fasciculations similar to the spontaneous activity described in infantile spinal muscular atrophy. Nerve conduction velocity, especially that of slower motor fibres, was reduced in several cases. Electroneuromyographic abnormalities also persisted on re-examination. Although diphenyl is considered a comparatively safe chemical, it showed evidence of neurotoxicity when workers were exposed to concentrations in excess of the presently accepted threshold limits. Electrophysiological methods should be applied for the early detection of occupational hazards.