Qualitative color vision impairment in toluene-exposed workers

Objective: The aim of this study was to evaluate whether toluene, like many other organic solvents and solvent mixtures. could impair color vision. Subjects and methods: We investigated color vision impairment in three groups of workers, two groups occupationally exposed to toluene and a nonexposed group. The first exposed group, group E-1, comprised 41 workers (median value of toluene in air 35.00 ppm, range 11.3-49.3 ppm) and the second exposed group, group E-2, comprised 32 subjects (median value of toluene in air 156.00 ppm. range 66.0-250.0 ppm). The nonexposed group, group NE, comprised 83 subjects. Color vision was evaluated by the Lanthony D-15 desaturated test according to Verriest's classification: type I, loss in the red-green range; type II, loss in the blue-yellow and red-green ranges, and type III, loss in the blue-yellow range. Subjects were classified as dyschromates if specific acquired loss was determined in at least one eye. In both exposed groups: exposure was evaluated by measurement of the concentration of toluene in the ambient air and in the blood. In group E-2, level of hippuric acid and orthocresol in urine after the work shift were also determined. The Mann-Whitney U-test: t-test, chi(2)-test, and Spearman's rank correlation and multiple regression analysis were used for statistical analysis. Results: Type III dyschromatopsia was detected in all groups examined: 26.6% of the workers in group NE, 31.7% of those in group E-1, and 50% of those in group E-2. As many as 15.6% of the workers in group E-2, 4.8% of those in group E-1, and only 1.2% of those in group NE had type II dyschromatopsia. A statistically significant difference in the prevalence of total dyschromatopsia (type III + type II) was established among the three examined groups together (chi(2) = 14.13; df = 2; P < 0.01), between group E-2 and group E-1 (chi(2) = 4.96; P < 0.05), and between group E-2 and group NE (chi(2) = 12.50; P < 0.005), whereas no significant difference was found between groups Ei and NE. Type III dyschromatopsia was significantly correlated with age in group NE (P < 0.01) and in group E-1 (P < 0.005). In group E-2, both type II (P < 0.05) and type III dyschromatopsia correlated with toluene in ambient air and with the duration of exposure to toluene (both P < 0.005). In group E-2, total dyschromatopsia correlated significantly with toluene in ambient air and in blood (both P < 0.05) as well as with hippuric acid in urine after the work shift (P < 0.001). Conclusion: This study suggests that toluene can impair color vision.