LED in street lamps: Researchers see possible risks

Street lighting is gradually being modernized in many countries. Energy-efficient LED lamps are in trend. But the blue light inhibits the release of melatonin and can disturb the circadian rhythm.

The use of LED light sources for street lamps means that fewer stars are visible in cities.

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(dpa) The switch from street lamps to LED lamps (light-emitting diodes) in many European countries has changed the color spectrum of night-time lighting – with possible consequences for people and animals. This is what British scientists write in the journal Science Advances. Using photos taken from the International Space Station (ISS), they found that the proportion of emissions in the blue area of ​​the spectrum in particular had increased as a result of the whiter LED lamps.

Since blue light, for example, inhibits the release of the hormone melatonin, which promotes sleep, switching to LED light could have an impact on animals and humans, writes the research team led by Kevin Gaston from the University of Exeter in Penryn.

“The benefits that LED technology can bring to public lighting, and street lighting in particular, have been widely touted, with a focus on increased energy efficiency and the associated reduction in energy bills and carbon emissions,” the study said. From the point of view of the researchers, the negative consequences for the environment resulting from the use of white LED lamps in street lighting should not be ignored. At the very least, the color spectrum of night-time lighting should be measured regularly.

Researchers evaluated photos from space

“While data on the spatial and temporal variation in the intensity of artificial light was available at regional and global levels, data on the variation in its spectral composition was only collected for a few locations,” the researchers write. The reason for this lies in the satellite sensors that are usually used to measure artificial lighting and only register the intensity of the light, but not its color. In addition, these sensors are hardly sensitive to the wavelength of blue light.

Gaston and colleagues therefore resorted to less systematically taken photos: photos taken by astronauts from the ISS. Around 1.25 million recordings have been made since 2003. The scientists selected photos from 2012 and 2013 showing Europe at night and compared them with photos of the same regions from 2014 to 2020. The boundary between the two periods marks the point at which LED lamps are ready for the market as light sources for street lamps .

Blue light influences the biorhythms of humans and animals

The researchers saw an 11.1 percent increase in green light but a 24.4 percent increase in blue light during the second period. A shift in the light spectrum towards blue light occurs above all when so-called sodium vapor lamps with orange-yellow light are replaced by white LED lamps, which emit a significantly larger proportion of blue light. The scientists observed such a shift in particular in Italy, Romania, Ireland and Great Britain. The smallest change was in Germany and Austria.

With regard to the effects of these changes on the biological environment, Gaston’s team cites four aspects: Because blue light inhibits the release of melatonin, the biorhythms in animals, but also in humans, can be disrupted. Previous studies have shown that nocturnal lighting has negative consequences for the movement and feeding behavior of bats. In addition, the use of LED lighting means that there are even fewer stars visible in cities and that the movement patterns of moths and other insects approaching or avoiding light sources are further changing.

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