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The Effect of Bright Light on Physiological Circadian Rhythms and Subjective Alertness of Shift Work Nurses in Iran

Kakooei H., Ardakani Z. Z., Ayattollahi M. T., Karimian M., Saraji G. B., Owji A. A.

International Journal of Occupational Safety and Ergonomics

2010

Vol. 16, No. 4

477--485

In this study, the effects of bright light (BL) on the rhythms in body temperature, plasma melatonin, plasma cortisol and subjective alertness, in 34 shift work nurses at a university hospital were assessed. They were exposed to very BL (4 500 lx) during 2 breaks (21:15–22:00 and 3:15–4:00) or dim light (300 lx). The subjects were studied under 24 h of realistic conditions during which their plasma cortisol and melatonin were measured at 3-h intervals; their body temperature was also measured during and after night shift work. Subjective alertness was evaluated with the Karolinska sleepiness scale. Administration of BL significantly suppressed night-time melatonin levels. A one-way ANOVA revealed that BL tended to increase cortisol levels and body temperature and significantly improved alertness. These results demonstrate that photic stimulation in a hospital setting can have a powerful influence on the adjustment of the circadian system.

Evaluation of Workers’ Exposure to Methylene Diphenyl Diisocyanate (MDI) in an Automobile Manufacturing Company, Iran

Kakooei H., Shahtaheri S. J., Karbasi H.- A.

International Journal of Occupational Safety and Ergonomics

2006

Vol. 12, No. 4

443--449

Evaluation of personal inhalation exposure to methylene diphenyl diisocyanate (MDI) among 39 employees, working in the window fixation and window glue processes in an automobile manufacturing company was performed. This study was conducted for both case and control groups. After sampling and sample preparation processes, MDI was determined with a UV-VIS spectrophotometer at 590 nm; the lung function was assessed with a digital spirometer, too. The average concentration of MDI in the window fixation, and window glue workplaces were 34.53 and 27.37 μg/m3, respectively, which was lower than the threshold limit value (TLV) recommended by the American Conference of Governmental Industrial Hygienists (ACGIH) (51 μg/m3). Respiratory symptoms in the exposed group were significantly different compared to the unexposed group (p < .05). Lung capacities in the case group were lower than in the control group (p < .05). Therefore, MDI can be easily measured making it possible to evaluate the adverse effects caused by occupational exposure.