Cumulative exposure to styrene and visual functions

Background: Results from a 1990-1992 longitudinal study of several reinforc ed plastics plants showed that for those workers whose styrene exposure had decreased, color vision (CV) improved; while near visual contrast sensitiv ity (CS) was poorer. Methods: In 1999, we retested these visual functions in 18 workers with goo d visual acuity. A cumulative exposure index (CEI), corrected for respirato r use, was calculated for each worker. Results: Intra-individual comparison of mandelic acid (MA) showed a signifi cant decrease over time (Friedman; P = 0.015), but current values were not related to CEI, For CV, no significant difference was observed between 1992 and 1999; present results were not related to MA or CEI. The CS profile de creased over time, with significant differences at 3 cpd (Friedman; P < 0.0 5). CS did not vary with MA levels, but was significantly depressed at the intermediate frequencies among those in the upper CEI category (Kruskal-Wal lis; P < 0.05). Conclusions: These findings suggest that CS loss increases with long-term c umulative exposure, reflecting chronic damage to the neuro-optic pathways. (C) 2001 Wiley-Liss, Inc.