Assessment of colour vision impairment in male workers exposed to toluene generally above occupational exposure limits

We investigated colour vision impairment in 45 male workersoccupationally exposed to toluene (mean value of toluene concentrationin ambient air=119.96 ppm) and in 53 controls. Colour visionwas evaluated by Lanthony-D-15 desaturated test and expressedas Age and Alcohol Intake Adjusted Colour Confusion Score (AACDS)or types of dyschromatopsia. Exposure was evaluated by measurementof toluene concentration in ambient air and blood, and hippuricacid and orthocresol determined in urine after the workshift.A statistically significant higher AACDS value was establishedin the exposed subjects compared to the controls (p<0.0001).There was no significant difference between AACDS values onWednesday morning compared to Monday morning. In the exposedgroup AACDS significantly correlated with the concentrationof toluene in ambient air, concentration of toluene in bloodand the concentration of hippuric acid in urine after the workshift(all p<0.0001). Dyschromatopsias were detected in both groups,although no significant difference between groups was established.In the exposed group, concentration of toluene in ambient air,alcohol intake and age explained 35.1%, concentration of toluenein blood, age and alcohol intake explained 19.9%, and concentrationof hippuric acid in urine and age explained 19.2% of the variationin type III dyschromatopsia. Concentration of toluene in ambientair and age explained 28.3% of the variation in total dyschromatopsia,and concentration of hippuric acid and age explained 13.8%.In the control group, age and alcohol intake explained 19.6%of the variation in type III dyschromatopsia. In exposed workersa significant difference was found in the AACDS value comparedto controls. However, no significant difference was found inthe prevalence of colour vision loss in the yellow-blue and/orred-green axis. Based on the results of this study the authorsconclude that the effect of toluene on colour vision can bechronic and that the possible reparation period in colour visionimpairment is longer than 64 hours.