VISUAL DYSFUNCTION AMONG STYRENE-EXPOSED WORKERS

Objectives The present study was undertaken to examine the relation be tween visual functions and occupational exposure to styrene. Methods A total of 128 workers (85% of the total population), from three glass- reinforced plastics plants in Canada, agreed to participate in the stu dy. Environmental and biological measures were made on the day(s) prio r to the assessment of near visual acuity (National Optical Visual Cha rt), chromatic discrimination (Lanthony D-15 desaturated panel), and n ear contrast sensitivity (Vistech 6000). The analyses were performed o n 81 workers with near visual acuity of at least 1 min of are at 0.5 m . Results The subjects were relatively young [29 (SD 8) years], with l ittle seniority [5 (SD 4) years]. Styrene exposure for 8 h ranged from 6 to 937 (first quartile 21 mg . m(-3), third quartile 303 mg . m(-3) ), depending on the job site. The end-shift concentrations of urinary mandelic acid ranged from nondetectable to 1.90 mmol . mmol creatinine (-1). Significant positive relations were found between the internal a nd external styrene exposure measurements and color vision loss adjust ed for age, alcohol consumption, and seniority in a multiple regressio n analysis. The multiple regression analysis also showed that the end- shift concentration of urinary mandelic acid was inversely related to contrast sensitivity at 6 and 12 cycles degree(-1). Logistic multiple regression models indicated that the end-shift concentration of urinar y mandelic acid was related to the prevalences of blurred vision, tear ing, and eye irritation. Conclusions These findings suggest that there is a positive relation between styrene exposure and early color and c ontrast vision dysfunction.