Colour vision and occupational toluene exposure: results of repeated examinations

Potential effects of human occupational exposures to toluene on colour vision were investigated in a follow-up study over 4 years with three repeated examinations. Colour vision was measured with the Lanthony desaturated colour vision test D-15d, and the colour confusion index (CCI) was calculated. The mean current exposures were 26+/-21 ppm for printers (high toluene level) and 3+/-4 ppm for end-processors (low toluene level). The mean exposure durations were 23+/-6 years for "long-time exposed" and 7+/-2 years for "short-time exposed" subjects. Repeated analyses (n=162) and multiple regressions (maximum available n=267) did not reveal significant effects of toluene with respect to intensity or duration of current or long-term exposure. Age and occupational qualification were significantly associated with CCI in both kinds of analysis, whereas alcohol consumption (carbohydrate-deficient transferrin, CDT) and smoking habits (cigarettes per day) were not. It is concluded that current industrial exposure limits of toluene provide sufficient protection against possible disturbance of colour vision.