Neurophysiological effects of long-term exposure to a mixture of organic solvents

Neurophysiological effects of long-term exposure to a mixture of organic solvents was studied among 102 car painters from 27 car repair garages in Helsinki. The reference group consisted of 102 age-matched railroad engineers from the Finnish State Railways. The mean age was 35 years and the exposure time ranged from 1 to 40 years (mean 14.8, SD 8.5). According to measurements the mean concentration of the solvent mixture was relatively low in the garages, namely, 31.8% of the Finnish threshold limit value (TLV), the range of separate components varying from 4 to 212% of the respective TLVs. The main components of about 20 organic solvents of the mixture were toluene, xylene, butyl acetate and white spirit. Electroencephalograms (EEGs) of all the 102 exposed and 102 nonexposed subjects were studied, but electroneuromyographic measurements were made of only 59 car painters and 53 referents with a similar age distribution. Motor (MCV and CVSF) and sensory conduction (SCV) velocities, as well as motor distal latencies, were recorded from nerves in the upper and lower extremities. Abnormal EEGs were encountered in 32 car painters and 37 referents. The frequency of abnormal EEGs was in both groups higher than expected on the basis of EEG literature (about 10%). Twenty-six car painters had a complex of four common symptoms of disturbances in the central nervous system; the same symptom complex was found in 12 engineers. Forty-six percent of the car painters with this symptom complex had an abnormal EEG, while only 26% of those without this symptom complex had an abnormal EEG. Railroad engineers did not show such a tendency. Abnormally slow MCVs or SCVs and/or prolonged motor distal latencies were found in 12 of the 59 car painters but in none of the 53 engineers studied. Other authors have stressed that many solvents primarily cause neuropathy, while objective signs of central nervous involvement have been minor, if any. Our findings are similar; they showed slight positive signs of slowed nerve conduction velocities among the car painters and no increase in EEG abnormalities in comparison to the reference group of railroad engineers.