Intervention study on acquired color vision deficiencies in styrene-exposed workers

The main aim of the study was to examine the possible effects of occupation al exposure to styrene on color vision function and the course after reduct ion of exposure. Color vision function was examined in 22 styrene-exposed l aminators and 11 control subjects at a boat manufacturing plant. The Lantho ny D-15 desaturated panel was used to test acquired dyschromatopsia. In all , six examinations were performed: Monday morning and Thursday afternoon of the same week, before and immediately after a vacation of 4 weeks (altoget her, phase 1), and approximately 10 months later (phase 2), after the expos ure level of styrene had been reduced. Styrene uptake was objectified by bi ological monitoring measuring the metabolites mandelic acid and phenylglyox cylic acid in urine samples taken on Thursday afternoon. In both Thursday e xaminations, styrene-exposed workers had higher color confusion index (CCI) values compared with controls, which indicated quantitative color vision l oss. After an exposure-free period of 4 weeks, a significant decrease of CC I values to normal range was found in laminators. Reexamination 10 months l ater showed also lower CCI values in exposed workers, indicating a dose-eff ect relationship. Abnormal CCI values occurred primary in subjects with an excretion of approximately 500 to 600 mg mandelic acid plus phenylglyoxcyli c acid per gram creatinine or more. We concluded that styrene-induced color vision dysfunction is reversible after an exposure-free interval of 4 week s. The current Biological Tolerance Value of 600 mg mandelic acid plus phen ylglyoxcylic acid per gram creatinine, as used in Germany, protects styrene -exposed workers from this subclinical effect.