FOR a century, Drosophila melanogaster has been the species at the heart of genetic research – and now it’s helped Jeffrey Hall, Michael Rosbash and Michael Young to win the Nobel Prize in Physiology or Medicine for their work on circadian rhythms (biological clocks), explaining how plants, animals, and humans – every living thing of earth – synchronisetheir biological rhythms with the turning of the earth that creates day and night.

Yet since the invention of gas lighting in the 1790s, we’ve been doing our utmost to banish night.

And boy, have we succeeded. Look at a picture of the globe by night and the northern hemisphere will tell you a tale of light pollution so vast that about one in three humans can no longer make out the Milky Way.

Humans have been stargazing since time immemorial; it’s very strange to think that we have managed, in such a short period of time, to dramatically alter one of our most essential experiences, something that connected us to our foremothers and fathers to the gazillionth generation.

Does it matter, apart from the aesthetics of seeing a sky thick with stars? Yes, it does. Light pollution is having a real impact on wildlife and plants – frogs and migrating birds and baby turtles are led astray by it, while it’s bad news for plants that are pollinated by moths lured away by the irresistible temptations of streetlights and porch lamps.

But it’s the effects on us humans that I think about when I’m trying to banish light from hotel rooms. There’s always a battery of little lights: a green light that tells you the TV is on, a blue light on the kettle, a series of red and orange lights on the remote controls for the TV, the aircon and even, in one room I stayed in, the remote that opened and closed the curtains.

The worst was in a Nairobi hotel, a room equipped with an empty glass-fronted fridge which blared a blue-white light into the room so bright you could have done your make-up by it.

The 24-hour swing from light to dark and back again, the circadian clock, has important impacts on our physiological processes – brain waves, hormones, and how each cell in our bodies works, for example.

No wonder “Disruption of the circadian clock is linked to several medical disorders in humans, including depression, insomnia, cardiovascular disease, and cancer, says Paolo Sassone-Corsi, chairperson of the Pharmacology Department at the University of California, Irvine, who has done extensive research on the circadian clock. ‘Studies show that the circadian cycle controls from ten to fifteen percent of our genes,' he explains. 'So the disruption of the circadian cycle can cause a lot of health problems'."

Artificial light at night (ALAN), is a big circadian disruptor. (The acronym always makes me laugh – it reminds me of the Walk on the Wildside prairie dog shouting, “Alan! Alan! Alan! It’s been shown that exposure to light at night suppresses the production of melatonin (the ‘sleep hormone’) and raises blood sugar, high enough to tip people over into a prediabetic state.

“In 2007, the World Health Organization designated shift work as a ‘probable carcinogen' after findings from epidemiological and laboratory studies proved that light at night increases the risk of breast cancer,” notes a paper published earlier this year.

ALAN has profound positive effects, of course: I’d hate to have had to negotiate London’s dark and dangerous streets in the 18th century, before gas lamps, or struggle to read by a guttering candle. But as is so often the case with grand human advances, we only find out about the negative consequences much later.

Interestingly the worst impact seems to come from light in the bluer part of the spectrum: “… blue light suppressed melatonin for about twice as long […] and shifted circadian rhythms by twice as much.”

This makes sense when you discover that sunlight in the middle of the day contains more alert-making, wake-up blue wavelengths; as we move towards sunset, these short wavelengths are scattered and the light shifts towards the redder part of the spectrum.

It’s precisely this blue/white light that the Nairobi fridge was pumping out – and that we’re all overdosing on as we read tablets and catch up on Facebook and finish a proposal on our laptops under a fluorescent light.

Do we have to give up lighting our world to avoid the health (and environmental) impacts? Nooo… but I do think we should be thinking a bit more about the impact of light and how we use it. In his book The End of Night, Paul Bogard points out that a lot of our lighting is very wasteful – light spills out into the sky and the neighbour’s property from street lights and security lights that could be more focused and tightly directed.

We could also shift to more red-spectrum light bulbs; we could avoid screens with blue/white light for about two to three hours before bedtime; and if we have to do screen-time at night, we could invest in spectacles that block the blue/white wavelengths.

I know you can get them in South Africa, but not that easily – so here’s a business opportunity, with a huge potential market of tired, unhealthy people who want to make their circadian rhythms as perfect as those of the fruitflies!

Mandi Smallhorne is a versatile journalist and editor. Views expressed are her own. Follow her on Twitter.







