Effect of exposure to low levels of organic solvent mixtures On color vision

ABSTRACT

Color vision deficiency has a relatively high prevalence in working population and cause difficulties in everyday tasks. Occupational exposure to various neurotoxic chemicals has been shown to be associated with acquired color vision impairment. This study was undertaken to determine the effect of occupational exposure to mixed organic solvents at low levels on color perception. A cross sectional study was conducted in an automobile plant. Workers employed in painting saloon, were considered as cases and workers employed in assembly saloon were considered as controls, as well. We administered a questionnaire, containing age, years of employment, histories of congenital color vision impairment or eye injuries, alcohol consumption and for workers. After considering exclusion criteria, Color vision of 121 case workers compared with 157 controls. The LD-15 test showed that 31.4% of case group had an acquired color vision defect .Most defects were of the blue-yellow type in the case group. Also the prevalence of acquired color vision defect was 3.8% in the control group. The prevalence of acquired color vision defect of exposed employees were statistically significantly higher than those of the control subjects [OR = 11.52, CI = 4.67- 28.38] [P<0.001]. Besides mean of the color-confusion index [CCI] derived from the LD-15 test for exposed employees were statistically significantly higher than those of the control subjects [1.14 and 1.03 respectively and P<0.001].The logistic regression for color confusion index [CCI] showed that it was positively related to exposure to mixed organic solvents [P<0.001]. The results of this study suggest that, chronic occupational exposure to mixed organic solvents even at lower concentrations than permissible levels can cause acquired color vision impairment. Also acquired color vision impairment seems to be a sensitive indicator which can detect solvent-induced neurotoxicity in car painters. Finally we propose that the color confusion index [CCI] may be used as an appropriate indicator of early neurotoxic effects in workers exposed to low concentrations of mixture of organic solvents