Street lighting is getting brighter and more blue-tinged in many countries in Europe 鈥� and that may interfere with our sleep and be bad for our health in other ways.
The shift to the bluer side of the light spectrum, caused by the increased use of LEDs in public street lamps, has been revealed by informal photographs taken by crew members on the International Space Station (ISS).
Exposure to blue light from phones and TVs can interfere with people鈥檚 sleep because light-detecting cells in the eye that control the release of the sleep hormone melatonin are especially sensitive to blue light. Some studies suggest that too much artificial light exposure can also promote conditions such as obesity and diabetes.
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Streetlights are seen as good for our safety, but are often viewed as a potential hazard for nocturnal animals and a disruption for stargazers.
To reduce the carbon emissions of the lights, many countries have been switching their orange-tinged sodium lamps to ones that use white LEDs because the newer ones are more energy efficient.
Despite this advantage, LEDs tend to be more blue-tinged, says at the University of Exeter, UK.
S谩nchez de Miguel鈥檚 team scoured a NASA database of photos taken on the ISS that show Europe at night over two periods, 2012 to 2013 and 2014 to 2020. The researchers then calculated how the spectra of artificial lights had changed in different countries over time.
The shift towards blue light was particularly prominent in the UK, Ireland, Italy and Romania. In the UK, the blue light component of artificial lighting had risen by 18 per cent between the two periods studied.
People may be more affected by light coming from electronic devices than they are by light outside houses, says S谩nchez de Miguel. However, previous studies have shown that even a low light level, equivalent to a bright street lamp shining through thin curtains all night, can reduce people鈥檚 ability to regulate blood sugar the next day.
at University College London says the new findings should raise concerns. 鈥淭he spectral composition will disturb our circadian rhythms and there鈥檚 an excess of light at inappropriate times of the day,鈥� he says.
Another study, released earlier this month, found that while blue light exposure before bedtime reduced melatonin levels, it didn鈥檛 affect people鈥檚 self-reported sleep quality if the exposure stopped 50 minutes before they tried going to sleep.
Science Advances
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