Heo, J. - Y., Kim, K., Fava, M., Mischoulon, D., Papakostas, G. I., Kim, M. - J., et al. (2017). Effects of smartphone use with and without blue light at night in healthy adults: A randomized, double-blind, cross-over, placebo-controlled comparison. J Psychiatr Res, 87, 61–70.
Abstract: Smartphones deliver light to users through Light Emitting Diode (LED) displays. Blue light is the most potent wavelength for sleep and mood. This study investigated the immediate effects of smartphone blue light LED on humans at night. We investigated changes in serum melatonin levels, cortisol levels, body temperature, and psychiatric measures with a randomized, double-blind, cross-over, placebo-controlled design of two 3-day admissions. Each subject played smartphone games with either conventional LED or suppressed blue light from 7:30 to 10:00PM (150 min). Then, they were readmitted and conducted the same procedure with the other type of smartphone. Serum melatonin levels were measured in 60-min intervals before, during and after use of the smartphones. Serum cortisol levels and body temperature were monitored every 120 min. The Profile of Mood States (POMS), Epworth Sleepiness Scale (ESS), Fatigue Severity Scale (FSS), and auditory and visual Continuous Performance Tests (CPTs) were administered. Among the 22 participants who were each admitted twice, use of blue light smartphones was associated with significantly decreased sleepiness (Cohen's d = 0.49, Z = 43.50, p = 0.04) and confusion-bewilderment (Cohen's d = 0.53, Z = 39.00, p = 0.02), and increased commission error (Cohen's d = -0.59, t = -2.64, p = 0.02). Also, users of blue light smartphones experienced a longer time to reach dim light melatonin onset 50% (2.94 vs. 2.70 h) and had increases in body temperature, serum melatonin levels, and cortisol levels, although these changes were not statistically significant. Use of blue light LED smartphones at night may negatively influence sleep and commission errors, while it may not be enough to lead to significant changes in serum melatonin and cortisol levels.
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Alzahrani, H. S., Khuu, S. K., & Roy, M. (2019). Modelling the effect of commercially available blue-blocking lenses on visual and non-visual functions. Clin Exp Optom, in press.
Abstract: BACKGROUND: Blue-blocking lenses (BBLs) are marketed as providing retinal protection from acute and cumulative exposure to blue light over time. The selective reduction in visible wavelengths transmitted through BBLs is known to influence the photosensitivity of retinal photoreceptors, which affects both visual and non-visual functions. This study measured the spectral transmittance of BBLs and evaluated their effect on blue perception, scotopic vision, circadian rhythm, and protection from photochemical retinal damage. METHODS: Seven different types of BBLs from six manufacturers and untinted control lenses with three different powers (+2.00 D, -2.00 D and Plano) were evaluated. The whiteness index of BBLs used in this study was calculated using Commission International de l'Eclairage (CIE) Standard Illuminates D65, and CIE 1964 Standard with a 2 degrees Observer. The protective qualities of BBLs and their effect on blue perception, scotopic vision, and circadian rhythm were evaluated based on their spectral transmittance, which was measured with a Cary 5,000 UV-Vis-NIR spectrophotometer. RESULTS: BBLs were found to reduce blue light (400-500 nm) by 6-43 per cent, providing significant protection from photochemical retinal damage compared to control lenses (p </= 0.05). All BBLs were capable of reducing the perception of blue colours, scotopic sensitivities and circadian sensitivities by 5-36 per cent, 5-24 per cent, and 4-27 per cent, respectively depending on the brand and power of the lens. CONCLUSION: BBLs can provide some protection to the human eye from photochemical retinal damage by reducing a portion of blue light that may affect visual and non-visual performances, such as those critical to scotopic vision, blue perception, and circadian rhythm.
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Teare, S. W. (2000). The night sky brightness at Mount Wilson Observatory. The Observatory, 120, 313–317.
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Mammola, S., Isaia, M., Demonte, D., Triolo, P., & Nervo, M. (2018). Artificial lighting triggers the presence of urban spiders and their webs on historical buildings. Landscape and Urban Planning, 180, 187–194.
Abstract: Different spider species living in the urban environment spin their webs on building facades. Due to air pollution, web aggregations entrap dirt particles over time, assuming a brownish-greyish colouration and thus determining an aesthetic impact on buildings and street furniture. In Europe, the most common species causing such an aesthetic nuisance is Brigittea civica (Lucas) (Dictynidae). In spite of the socio-economical relevance of the problem, the ecological factors driving the proliferation of this species in the urban environment are poorly described and the effectiveness of potential cleaning activities has never been discussed in scientific literature. Over one year, we studied the environmental drivers of B. civica webs in the arcades of the historical down-town district of Turin (NW-Italy). We selected a number of sampling plots on arcade ceilings and we estimated the density of B. civica webs by means of digital image analysis. In parallel, we collected information on a number of potential explanatory variables driving the arcade colonization, namely artificial lighting at night, substrate temperature, distance from the main artificial light sources and distance from the river. Regression analysis showed that the coverage of spider webs increased significantly at plots with higher light intensity, with a major effect related to the presence of historical lampposts with incandescent lamps rather than halogen lamps. We also detected a seasonal variation in the web coverage, with significant higher values in summer. Stemming from our results, we are able to suggest good practices for the containment of this phenomenon.
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Kersavage, K., Skinner, N. P., Bullough, J. D., Garvey, P. M., Donnell, E. T., & Rea, M. S. (2018). Investigation of flashing and intensity characteristics for vehicle-mounted warning beacons. Accident Analysis & Prevention, 119, 23–28.
Abstract: Reducing the potential for crashes involving front line service workers and passing vehicles is important for increasing worker safety in work zones and similar locations. Flashing yellow warning beacons are often used to protect, delineate, and provide visual information to drivers within and approaching work zones. A nighttime field study using simulated workers, with and without reflective vests, present outside trucks was conducted to evaluate the effects of different warning beacon intensities and flash frequencies. Interactions between intensity and flash frequency were also analyzed. This study determined that intensitiesof 25/2.5 cd and 150/15 cd (peak/trough intensity) provided the farthest detection distances of the simulated worker. Mean detection distances in response to a flash frequency of 1 Hz were not statistically different from those in response to 4 Hz flashing. Simulated workers wearing reflective vests were seen the farthest distances away from the trucks for all combinations of intensity and flash frequency.
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