Home Madrid university Photos from space claim that streetlights emit more blue spectra

Photos from space claim that streetlights emit more blue spectra


A group of environmental scientists from England have collected photos of Earth taken from the International Space Station over the past decade showing a broad trend across Europe of artificial nighttime lighting veering much more towards the blue spectrum than before.

Write in the journal Scientists progressthey warn that the change “significantly increases the risk of adverse effects on ecosystems”.

The observation of more pronounced blue spectra is not in itself a surprise, given that many outdoor LED fixtures tend to emit more blue-rich wavelengths than the lights they replaced, such as as low pressure sodium and others.

But as the University of Exeter team noted, photographs taken by astronauts over two time periods – 2012 to 2013 and 2014 to 2020 – provide what scientists say is the first large-scale depiction blue stain that actually occurs. Astronauts took the photos using DSLR cameras and scientists analyzed the spectral content captured in the images.

“While data on the spatial and temporal variation of the intensity of artificial lighting are available at regional and global scales, data on the variation of its spectral composition have only been collected for a few places, preventing the variation in associated risks to the environment and human health from being mapped,” said the team from the Penryn campus in Exeter.

Here we use images obtained with digital cameras by astronauts from the International Space Station to map the variation in spectral composition of illumination across Europe for 2012-2013 and 2014-2020” , continued the team, led by Alejandro Sánchez de Miguel, who is also affiliated with the Complutense University of Madrid. “These show a widespread regional spectral shift, from that associated primarily with high-pressure sodium lighting to that associated with large white LEDs and greater blue emissions. By re-expressing the color maps in terms of As spectral indicators of environmental pressures, we find that this trend greatly increases the risk of adverse effects on ecosystems.

The authors point out that the trend has been uneven across Europe.

“Countries that have seen less marked changes are Austria and Germany,” they note. “These countries are traditionally very conservative in their lighting conversions. For example, Germany probably has the highest proportion of gas lighting of any country, and many fluorescent and mercury vapor lamps are still used, so the spectral change with the LED transition is less marked. Conversely, there were marked increases in blue in Italy, Spain, the UK, Ireland and Romania, they wrote.

In places where it occurs, the blue spectrum has a “substantial biological impact” on humans and ecosystems, they noted. While referencing previous studies showing effects on bats, invertebrates, and others, the authors selected examples that they analyzed.

The team pointed to adverse effects on melatonin production in many organisms. Melatonin is a hormone associated with sleep and the circadian cycle in many animals as well as humans. They also noted that an excess of artificial light at night, especially in the blue spectrum, impairs the ability of not only humans but also animals to see the stars, to the detriment of creatures that use the stars for navigation. And they wrote that blue wavelengths impair the light-determined (“phototactic”) activities of moths and other insects.

The authors also wondered if some of the benefits of LED street lighting were overstated. For example, energy savings are not always substantial, depending on the specific case, they note.

As part of a U.S.-based commercial market effort, the DesignLights Consortium established its LUNA Technical Requirements to simplify the ability to specify and implement outdoor lighting products that mitigate these concerns for humans and ecosystems while reducing energy consumption, providing appropriate light distribution, intensity, and color in their intended application. LED magazine will follow up on outdoor lighting regulations and programs in other regions over the coming year.

LED magazine has written numerous stories about the positive and negative effects of blue spectra and outdoor lighting on the night sky. Here are a few :

There are still disagreements over the commercialization of circadian lighting principles

Inside, adjustable lighting could help seniors stay stable

Outside, concerns arise over energy consumption due to excessive lighting

Turtle-friendly amber lighting also addresses dark sky concerns

Informed Local Communities Seek Dark Sky Approved Fixtures

BRAND HALPER is editor of LEDs Magazine and a journalist specializing in energy, technology and business ([email protected]).

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