Risk of chronic effects on the central nervous system at low toluene exposure

This study evaluates the chronic effects on the central nervous system of exposure to low concentrations of toluene (TWA < 20 ppm) on workers in a rotogravure plant. Ninety-eight male workers from a selection pool of 107 (92%) were examined neuropsychologically using a Cognitive Function Scanner, and neurologically by computerized methods measuring co-ordination ability, tremor and position stability. In addition measures of symptoms and former exposure were obtained by questionnaire. The workers were divided into three groups: Group 0 with no exposure to organic solvents (n = 19); Group 1 with exposure to TWA < 20 ppm of toluene for less than 13 years (n = 30) and Group 2 with exposure for more than 12 years (n = 49). Within Group 2, 37 (75%) had been exposed at levels exceeding 100 ppm for 10+ years before 1983. No significant differences were found between Group 0 and Group 1 regarding symptoms and results of the applied tests. Group 2 differed significantly from the two other groups in scoring higher on a symptom index (p = 0.04), particularly regarding concentration ability, reduced memory and fatigue. Group 2 scored significantly poorer on tests for visuospatial function, number learning and word recognition, while no differences regarding neurological functions were observed. The study showed no differences regarding neuropsychological and neurological functions between a non-exposed group of male workers and workers exposed to toluene less than 13 years at TWA < 20 ppm. However, long-term exposure to TWA (time weighted average) of toluene exceeding 100 ppm was associated with impaired neuropsychological function.