Combined effects of working environmental conditions in VDT work

The combined effects of city noise and luminance of the computer display we re evaluated from the changes in lymphocytes and mental activities of parti cipants. Healthy male students were tested under the following four experim ental conditions: (1) a calculating task on a video display terminal (VDT) with luminance of 90 cd m(-2) without city noise; (2) a calculating task on a VDT with luminance of 20 cd m(-2) without city noise; (3) a calculating task on a VDT with luminance of 90 cd m(-2) with city noise of 70 dB(A); an d (4) a calculating task on a VDT with luminance of 20 cd m(-2) with city n oise of 70 dB(A). A visual reaction test (VRT) was performed, and critical flicker fusion frequency (CFF), heart rate (HR), numbers of circulating whi te blood cells (WBCs), lymphocyte subsets and subjective symptoms of fatigu e were measured (1) before; (2) just after; and (3) 30 min after each 60 mi n test. Subjective symptoms of fatigue significantly increased just after e xperiments conducted under the two noisy conditions. VRT and CFF showed sig nificant changes in the case of the high-luminance display with noise. WBCs and neutrophils showed significant increases in the two quiet conditions. These results suggested that high luminance with noise had the most effect on subjective fatigue and mental activities.