Reacción a "Reactions to study showing that artificial light is increasingly emitting blue spectra associated with LEDs"

We are witnessing the replacement of our city and road lighting from high-pressure sodium lamps (HPS) to LED luminaires. While the former are orange in colour, the new ones are mostly white because of their blue component in the spectrum. Switching to LEDs is motivated by energy savings and is an opportunity to reduce light pollution if the new luminaires are designed to illuminate more efficiently and low blue LEDs are used.  

Night-time images of the Earth obtained by artificial satellites show the location and intensity of artificial lights. Their analysis makes it possible to assess the increase in extent and brightness. However, these satellites were not designed to study light pollution and are, for example, blind to light emission in the blue region of the spectrum. Therefore, changes in the colour of artificial light sources caused by the onslaught of the switch to LED technology are not recorded. As a result, the estimation of the evolution of light pollution with these measures is not correct. We need blue-sensitive and colour-distinct images such as photographs from digital cameras working in RGB. 

The scientific use of night-time photographs obtained from the International Space Station was presented in the thesis of Alejandro Sánchez de Miguel (UCM, 2015). The analysis of these images makes it possible to estimate both the brightness and the colour of the luminaires. In the work now published, a mosaic of calibrated images covering Europe is shown. The authors can then estimate the colour evolution of the change in lighting technology and, importantly, estimate some of the environmental impacts of the increase in the blue component. As expected there is a measurable shift to bluer luminaires. The transformation of these colour images into environmental impact maps indicates that the risk of harmful effects on ecosystems is increasing.