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

The circadian clock regulates the correct functioning of multiple systems in the human body. The main synchronising factor of this system is the light that enters our eyes through the retina. Blue light, that with a spectrum of 380-450 nm, is the most effective in synchronising (or altering) this system. The systemic shift to mainly LED street lighting has been promoted in many European cities to reduce environmental impact. However, little is known about the change in light colour of this new street lighting and its impact on human and planetary health.

The study by Alejandro Sánchez de Miguel et al. highlights the shortcomings of previous studies that have assessed the increase in artificial night-time lighting using night-time images, but without taking into account the colour of the light emitted, so estimates may have been underestimated. In the present work, the authors have used images taken from the International Space Station with cameras that provide information on light colour and have shown an increase in artificial light levels, especially blue light, in Europe following the widespread switch to LEDs.

The study highlights the importance of assessing the impact of exposure to artificial light at night, especially in the blue spectrum. In addition, the authors of the paper also highlight the footprint that this increase in blue light may have not only for humans but also for many other species. The article demonstrates this progressive increase in blue light levels in European cities, although more studies are needed to assess its effects on human health and to propose preventive measures.