The assessment methods and application to detect potential hazards of neurotoxicity by environmental chemicals.

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Objective : To make clear the relationship between color visual and exposure level of styrene, especially in relation to both current exposure concentration and CEI (Cumulative Exposure Index).Method : Color vision and other neurobehavioral test batteries were examined among 74 workers in a FRP plant exposed to styrene and among 103 non-exposed controls by Lanthony desaturated panel D-15 test. The current exposure levels were expressed by end-shift urinary mandelic acid (MA), phenylglycoxylic acid (PGA) and urinary styrene. The CEI was calculated by concentration of the worker's urinary mandelic acids that were measured from 1991 to 1997 twice yearly.Result : The mean of urinary MA, PGA, styrene at the end-shift were 0.26±0.34, 0.11±0.11 g/g creatinine and 120.32± 146.20μ g/l. The average CEI was 7.1±5.9 years ; CCI (Color Confusion Index) of exposed workers showed a significant difference compared with the age-matched controls. The multiple regression analysis showed the concentration of urinary MA and PGA were related to color vision. Exposed workers were divided into two groups by a limit of urinary MA+PGA of 0.24 g/g creatinine. The CCI value in the higher exposed group was significantly increased. But no significant difference in CCI was observed between the lower exposed group and the age-matched controls. The results of this study suggest that both higher than 10 ppm exposure to styrene might impair color vision. As the consequence, re-evaluation for the safety limit of exposure to styrene is needed.