Neurophysiological findings among workers occupationally exposed to styrene.

Ninety-six male workers occupationally exposured to styrene in 24 plants producing reinforced polyester plastic products were studied neurophysiologically. The mean age of the subjects was 29.6 +/- 7.4 years, and the duration of the exposure varied from 6 months to 14 years (mean 5.0 years). Mandelic acid concentration in the urine (mean of five values determined during five consecutive weeks) was used as the measure of exposure. The individual means of the mandelic acid concentrations varied from 7 to 4,715 mg/dm3 (median 808 mg/dm3). Neurotoxic effects of styrene exposure upon the central nervous system were revealed by abnormalities in the EEG. The overall prevalence of abnormal EEGs was 24% (23 out of 96), which is higher than that found among a normal population (p less than 0.05). Abnormal EEGs were found in one-third of the subjects with relevant styrene exposure (mandelic acid concentration over 700 mg/dm3), while low-level styrene exposure did not increase the prevalence of normal EEGs above that found in a normal population. Nerve conduction velocity measurements performed on 40 subjects did not reveal any definite relationship between neuropathy and styrene exposure. The EEG examination is useful in the investigation of the neurotoxic effects of styrene. Whenever a possibility exists of excessive styrene exposure or beginning poisoning, the workers should be submitted to an EEG examination.