Estimation of Possible Suppression of Melatonin Production Caused by Exterior Lighting in Commercial Business Districts in Metropolises

ABSTRACT : Policymakers and standardization bodies have started to make recommendations about the use of lighting products at night, with the goal of reducing negative impacts on human health. We report a series of field measurements to quantify the responses of different human photoreceptors and the possible suppression of melatonin production caused by the exterior lighting in metropolises. In total, 888 spectral and 888 illuminance measurements were taken at 5.6 ft. above the ground in six commercial business districts, with three in Hong Kong and three in Shanghai. It was found that 47% and 86% of the measured light stimuli in Shanghai and Hong Kong may introduce suppression of melatonin production, as characterized using circadian stimulus (CS), because they had CS values beyond 0.05, a working threshold for acute melatonin suppression. In addition, both field measurements and computer simulations suggested that light stimuli with higher correlated color temperature (CCT) may not necessarily cause stronger melatonin suppression than those with lower CCT values.