Another reason to flip off the switch tonight

PARIS: For the 11th year running, cities worldwide will turn their lights off today to mark Earth Hour in a global call to action on climate change.

But the moment of darkness should also serve as a reminder, activists say, of another problem that gets far less attention: light pollution. More than 80 per cent of humanity lives under skies saturated with artificial light, scientists recently calculated.

In the United States and western Europe, that figure goes up to 99 per cent of the population, most of whom cannot discern the Milky Way in the night sky.

Even the most ardent critics of light pollution are not saying cities should go dark, or that lighting is not an essential element of urban life.

But society needs to address a growing list of concerns, they suggest.

“In general, it’s getting worse,” Diana Umpierre, president of the International Dark-Sky Association, said of light pollution in her home state of Florida.

And things are moving in the wrong direction.

“We are predicted to have 15 million more residents in the next 50 years” — with all the extra lighting that entails.

By contrast, in Chad, the Central African Republic and Madagascar — not coincidentally among the poorest countries in the world — three quarters of people have clear view of the heavens.

One of the biggest challenges in fighting light pollution was convincing people that “brightness” was not synonymous with “safety”, said Umpierre.

“Sometimes it’s just the opposite,” she argued, citing studies showing that people drove more carefully — and slowly — on roads with less or no lighting at night.

Over the last 15 years, biologists, doctors, non-governmental organisations and even the United Nations have joined the fight against light pollution.

In 2012, the American Medical Association concluded that exposure to “excessive” night light “can disrupt sleep and exacerbate sleep disorders”.

And it called for more research into possible links to cancer, obesity, diabetes and depression.

Last year, the AMA raised another red flag, this time about lightemitting diodes (LEDs).

Local governments in wealthy countries are racing to replace existing streetlights with LEDs, which consume less energy and last longer.

That is good news for the fight against global warming, cutting on fossil-fuel burning for electricity, but it may be bad news for health, the AMA cautioned.

Not only do the bluish, highintensity lights create a view-obscuring glare, they have “five times greater impact on circadian sleep rhythms than conventional street lamps,” the AMA concluded.

The new technology also obscured our view on the night sky even more than traditional city lighting.

“LEDs could double or triple the luminosity of the sky” — which means the stars get lost against the background, said the authors of a 2016 world atlas of night sky brightness. AFP of humans live under skies saturated with

artificial light