Circadian blues
Exposure to LED lights in our homes, offices and streets is disrupting our body clocks and putting us at risk of depressive disorders, obesity and cancers, according to a major new report.
It was 3.30am on a Monday in July 2016 and astronomer Ian Griffin was looking down at Dunedin from the Nasa research plane Sofia. The Boeing 747 was returning to its base at Christchurch Airport after spending the night taking infrared images of distant star formations from 12km above the Southern Ocean. Griffin, director of Otago Museum and the man responsible for installing its planetarium, asked the pilots to fly directly over his hometown. He wanted to see just how much light the sleeping city gave off.
“The place was ablaze with it,” he says.
“You could see Port Chalmers, the city centre, but also small centres such as Portobello and Waitaki. You don’t need to see them. The burghers of Dunedin are paying an enormous amount of money to light the underside of planes flying over at night.”
Famed for the photos he posts to Twitter of the Aurora Australis taken from around Otago, Griffin has been on a mission to reduce the light pollution emanating from Dunedin, which, like every other city in the country, is upgrading its high-pressure sodium street lights to newer LEDs.
The technology behind the blue-light-emitting diode in 2014 won its Japanese inventors the Nobel Prize in physics. It is more power-efficient, longer-lived and easier to maintain than incandescent and fluorescent bulbs.
Lighting consumes a quarter of the world’s electricity, so LEDs stand to play a major role in reducing emissions from fossil fuel-burning power plants. But they also emit blue-enriched white light, which can appear more like daylight than the yellow-orange sodium street lights they will have largely replaced here by the middle of the 2020s.
“The reason the sky is blue is because sunlight is scattered by particles in the atmosphere,” says Griffin.
“The bluer your lights, the more scattering you get and the easier it is to see. The lights at night will appear brighter to your eyes. But your visibility to the stars will decrease.”
In 2015, astronauts on the International Space Station took a night-time photo of Italy’s fashion capital, Milan, and compared it with a photo taken in 2012. The difference was stark. In the intervening years, the city had installed LED streetlights. Milan’s centre went from having a soft orange glow to a spider’s web of harsh white lines.
Griffin and his colleagues on the Dunedin City Council’s dark skies advisory panel want a different fate for their city. They recommended the council install LEDs with a warmer colour temperature (2600-3000 kelvin) than city planners typically favoured for optimum night-time visibility.
The council listened and settled on 3000k lamps with shielding to prevent light being cast upwards and smart controls to adjust their intensity remotely. Griffin is confident that the measures will, over the next decade, reduce light pollution and the glow on the horizon that pervades his astronomy photos.
More than half the country experiences a pristine night sky, but only 3% of us live under it. Most of us can’t see the Milky Way in all its glory.
“You are not going to be richer or poorer as a result of not seeing the Milky Way,” says Griffin. “But I would argue that going out of your house and looking up and seeing the stars has an impact on your life.”
The same LED technology powering those new street lights also illuminates our homes and lights up the smartphones, tablets, laptops and televisions that we gaze at for hours every day. Our exposure to the blue light they emit can have effects far greater than spoiling our star gazing.
The report “Blue Light Aotearoa”, released this week by the Royal Society Te Apārangi, confirms international concerns that exposure to blue light outside normal daylight hours can disrupt sleep and our circadian body clock, leading to a slew of negative health effects from depressive disorders and obesity to increased risk of cancers.
“Over the past hundred years, we’ve tried to control the light-dark environment and separate it from the natural environment,” says Lora Wu, a clinical psychologist and senior researcher at Massey University’s Wellington-based Sleep/Wake Centre.
“Doing so has messed with our body clocks. Every cell in your body has a clock, your organs have clocks and then we have this massive clock, and they can all get mixed up.”
Our bodies have evolved to
“The burghers of Dunedin are paying an enormous amount of money to light the underside of planes flying over at night.”
expect to be exposed to light during the day and darkness at night. Blue light, strongest at about noon, is good for us. But our 24-7 lifestyles, and immersion in a digital world that exposes us to overhead lighting and digital screens long after the sun has gone down, have a range of consequences.
The influence on biology of the circadian clock is well established in scientific literature. So-called photosensitive retinal ganglion cells in our eyes are constantly signalling the hypothalamus, where our body clock is located. The signals affect our circadian rhythms and neuroendocrine regulation – how our nervous system and endocrine hormones interact.
The complex processes can help explain everything from jet lag after passing through time zones to the poorer sleep of shift workers.
Then there’s melatonin, the hormone in our body that regulates wakefulness. It, too, is controlled by the circadian body clock and is influenced by light. Studies show that blue light exposure can suppress the night-time production of melatonin. Some people take melatonin pills to help get to sleep.
Wu treats patients suffering mood and sleep disorders and considers light exposure a major factor in many of her clinical cases.
“Light exposure is the biggest one. But for people, especially those with depression, you also see a fallout of social rhythms and normal daily behavioural rhythms as well.”
CANCER CONNECTION
The Royal Society describes the research into blue-light exposure and elevated risk of cancer as “preliminary”. When breastcancer-prone mice were exposed to light/ dark cycles that simulated shift work, they were found to have a higher rate of tumour development. There was enough evidence in human studies completed in Sweden for the World Health Organisation to classify shift work as a “probable carcinogen” due to circadian disruption.
“The physiological link might be through melatonin disruption,” Wu says.
The same can go for other activity that disrupts the body clock.
“If you eat in the middle of the night when your gut is not active and you activate it, that disrupts the link between your body clock and your gut clock.
“If that happens on a large scale, over and over, you may see increased rates of cancer.”
The more common effect of blue-light exposure is the sluggishness and inability to concentrate associated with working late into the night or lying in bed scrolling through your smartphone’s Facebook feed.
“We hold cellphones up to our face,” says Wu. “With young people, it is more about TV and video games. They are not as bad because you are sitting across the room. It is not as bright.”
She advises avoiding late night-time use of devices that emit blue light, but admits that such behaviour is hard to change.
Tech companies such as Google, which makes the Android operating system that powers most of the world’s smartphones, and Apple have introduced modes that reduce blue light from phone screens in the evening. Wu describes them as “band-aid” solutions, but better than nothing.
“It would be more ideal to just not use the screens at night. You need to think about the amount of time you are using it, how bright it is and how far away you are from it.”
She sees research into exposure to light as a neglected area when it comes to discussion of mental-health issues. “It is baffling to me not to look at sleep and circadian rhythms when we know there are such strong links between mental and physical health and social well-being. To completely ignore it is stunning.”
Also overlooked in the move to LED lighting is the impact on flora and fauna, from insects and seabirds to plants and trees.
Animals and plants are also subject to circadian rhythms and in many cases are more
sensitive to the light/dark cycle than we are.
“The timing of day length and the lunar cycle are things that animals can use to navigate and do certain activities,” says Margaret Stanley, a terrestrial ecologist at the University of Auckland and a co-author of the Royal Society report. “Under light pollution, that can be masked entirely.”
Anecdotal evidence suggests blue lights from LED lamps are confusing some animals into thinking it is daylight. Overseas, there are reports of turtle hatchlings emerging from their sandy burrows and heading towards the lights of town rather than running their usual gauntlet to the ocean. Fledgling seabirds have been drawn to the bright lights of cruise liners heading along the coast to and from Auckland’s port.
A New Zealand study found that flying insects, such as moths and flies, were more attracted to white LED lights than highpressure sodium street lights. The effects vary by species, though the research is still patchy.
Stanley is starting a project looking at the effects of light on nocturnal pollination by moths, beetles and other insects. Her concern is that when councils switch to LED lights, they do so with little understanding of the full effects on the natural world.
“How does that then flow on to the ecosystem in terms of insects being prey to bats and birds? What are the consequences for pollination? It is a bit of a worry.”
Ellery McNaughton, a PhD student supervised by Stanley, has studied the behaviour of birds before and after the introduction of LED lights on certain Auckland streets. Early results suggest there hasn’t been much change.
“The animals already surviving in urban areas are a bit more adaptable and flexible,” says Stanley. “It could also be due to the LED lighting we are putting up and how we are mitigating it with shielding and dimming.”
Part of McNaughton’s work has involved surveying light pollution across Auckland, which she found extends into the Waitakere Ranges and the Hauraki Gulf.
“We’ve focused on street lights,” says Stanley, “but there are massive commercial centres and industrial zones that are not shielding lights and spilling out these LED security lights.”
She believes tighter regulation of lighting on commercial buildings and even residential homes is needed to reduce the effects of night-time lighting on the environment.
GOING BATTY
Bats were on the mind of city planners in Hamilton as the city switched its 16,000 street lights to LEDs. “The effect on nocturnal creatures was quite a big thing for us,” says John Kinghorn, who leads Hamilton’s Smart City initiative. “We have quite a big bat population, especially in south-west Hamilton. We wanted to make sure the effect on them was minimised.”
The $7.2 million project was largely paid for by the New Zealand Transport Agency, which has made funding available to upgrade street lights all over the country. Hamilton was the first city to opt for warmer 3000k lights on all of its streets and arterial routes, rather than the cooler blue-tinged 4000k LEDs used elsewhere, including main roads of Auckland.
“There wasn’t any evidence we found to suggest that going from a 3000k to 4000k LED was anywhere near the difference to going from a sodium light to that LED colour. It was a logical choice for us to go with a warmer light,” says Kinghorn.
LED light levels and colour tones haven’t elicited a single complaint from Hamilton’s 160,000 residents. The lighting has also received the tick of approval of the Hamilton Astronomical Society.
When the project kicked off, the transport agency’s list of approved luminaires included LEDs around the 4000k mark. Bluer-toned lights are considered good for street illumination and helping driver reaction speeds.
But Hamilton was able to negotiate a roll-out of warmer-tone LEDs, supplied by lighting company Signify, and the agency now approves use of warm-white light, which suggests that with the right lighting design, shading and dimming, the worst effects of shifting to LEDs can be avoided. Dunedin is on the same path, says Griffin. “We are at an important juncture. Hopefully, with a bit of foresight, New Zealand can have safe streets at night but really nice dark skies.”
Imagine if you could look up from the centre of our biggest cities and see the Milky Way.
“It is baffling to me not to look at sleep and circadian rhythms when we know there are such strong links between mental and physical health and social well-being.”