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

We investigated colour vision impairment in 45 male workers occupationally exposedto toluene (mean value of toluene concentration in ambient air = 119.96 ppm) andin 53 controls. Colour vision was evaluated by Lanthony-D-15 desaturated test andexpressed as Age and Alcohol Intake Adjusted Colour Confusion Score (AACDS) ortypes of dyschromatopsia. Exposure was evaluated by measurement of tolueneconcentration in ambient air and blood, and hippuric acid and orthocresoldetermined in urine after the workshift. A statistically significant higher AACDS valuewas established in the exposed subjects compared to the controls (p < 0.0001).There was no significant difference between AACDS values on Wednesday morningcompared to Monday morning. In the exposed group AACDS significantly correlatedwith the concentration of 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 differencebetween groups was established. In the -exposed group, concentration of toluene inambient air, alcohol intake and age explained 35.1%, concentration of toluene inblood, age and alcohol intake explained 19.9%, and concentration of hippuric acidin urine and age explained 19.2% of the variation in type III dyschromatopsia.Concentration of toluene in ambient air and age explained 28.3% of the variation intotal 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 typeIII dyschromatopsia. In exposed workers a significant difference was found in theAACDS value compared to controls. However, no significant difference was found inthe prevalence of colour vision loss in the yellow-blue and/or red-green axis. Basedon the results of this study the authors conclude that the effect of toluene on colourvision can be chronic and that the possible reparation period in colour visionimpairment is longer than 64 hours.Key words: Colour vision; Lanthony-D-15 test; neurotoxicity; solvents; toluene exposure.