Scientists say exposure to blue light is kicking our natural body clock out of rhythm causing some to experience a perpetual jetlag.

Blue light is a part of daylight and is at its peak during the middle of the day, the orange glow we see at sunrise and sunset is due to less blue light wavelengths reaching us. Different types of artificial lights and screens emit varying amounts of blue light.

In 2002, scientists discovered a new type of cell in the human eye that detects blue light which send signals to the part of the brain responsible for our internal rhythms, such as when we feel sleepy or hungry or when different hormones are produced.

The Royal Society Te Apārangi produced a report on Tuesday which summarises the latest research evidence surrounding blue light and its effects.

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Dr Lora Wu, senior research officer at Massey University's Sleep/Wake Research Centre and a contributor to the report, said the blue-light sensitive cells in our eyes reset our body clock to the new time zone when we travel, but if these cells perceive too much blue light at night, then our body gets the wrong message about what time of day it is.

"This not only disrupts our sleep but can have a range of negative flow-on effects to our health, such as increased risk of obesity, depression and potentially some types of cancer. New evidence for health problems caused from disrupted sleep is emerging all the time."

SUPPLIED Royal Society Te Apārangi President Professor Wendy Larner said there is growing concern about potential health problems from people being exposed to blue light from artificial lights and screens at night.

People need to be exposed to blue light in the morning to keep their body clock in sync, she said.

"The message can be summed up with a little ditty 'Blue light at night, not so bright, blue light in the morning, stops you yawning'."

"What we're saying is people need to be exposed to blue light during the day, particularly in the morning, to keep their internal body clock in sync with the actual light-dark cycle. The best way of receiving this light is by being outside or via strong natural light coming in through a window.

"But, at the other end of the day, we need to limit how much blue light we are exposed to so as to not disrupt our sleep cycle and the many other factors of metabolism that are associated with our body clock, like digestion and cell renewal."

Rather than sitting in the dark, there are practical things we can do to reduce our exposure to blue light at night, Wu said.

"Inside our homes we can replace bluer 'cooler' light bulbs to bulbs that emit more yellow 'warm' light and use dimmers. We can also use software that reduces bright blue light from our digital screens at night or turn them off. It's also important to make sure your bedroom is dark while you sleep, so unplug any 'glowing' devices and use good quality curtains."

Exposure to artificial light can also disrupt body clocks of wildlife and affect pollination, feeding behaviours and reproduction.

123RF It’s not just humans who are affected by artificial blue light. Plants and animals also possess body clocks that regulate their rhythms of activity throughout the day and across the seasons.

Lindsay Bulman of Forest Protection at Scion said recent research has highlighted just how little artificial light it takes to have an impact on the environment.

"We were surprised that even small solar powered LEDs, the kind people have in their gardens, can alter insect behaviour, attracting some and reducing the activeness of others.

"Research carried out by Scion scientists also found that night time lighting caused large changes in the feeding behaviour of the native black-backed gull Larus dominicanus, extending its feeding until at least 1am in an isolated location.

"If we want to minimise the effect of nighttime lighting on the environment we need to think about how, when and where we use lighting at home and in public spaces, and look at using lights that do not have a significant blue wavelength component."

Our ability to study the night sky can also be compromised because blue wavelength light is more strongly scattered by the night sky, increasing skyglow if the lights are left unshielded.

ROYAL SOCIETY TE ĀPARANGI Rather than sitting in the dark, there are practical things we can do to reduce our exposure to blue light at night.

Associate Professor Karen Pollard, Director of the University of Canterbury Mt John Observatory said we need dark skies to be able to detect the faint lights from objects in outer space.

One way to protect wildlife and our ability to study the night sky is to set up dark sky reserves to reduce light pollution, she said.

Great Barrier Island received dark sky sanctuary certification in 2017 and more reserves are to be established in Martinborough, Stewart Island, Waiheke Island and Naseby.

"It's heartening to see this positive action towards reducing light pollution in Aotearoa," said Pollard.

"Outside these areas, people are talking about how we can best light roads and urban spaces – finding win-win solutions where we have the light we need to move about safely without increasing other risks to human health, wildlife or the visibility of our night sky. The technology exists now or will soon exist for us to achieve this balance."

TIPS TO REDUCE HARMFUL EFFECTS ON YOURSELF

* Expose yourself to daylight in the morning and darkness at night for better circadian health and wellbeing.

* Limit blue light exposure from digital screens including smartphones, televisions and computers at night by reducing screen brightness, using night-time apps that lower blue light output or turning devices off.

* Replace brighter blueish-white lightbulbs with warmer coloured yellowish-white lightbulbs.

TIPS TO REDUCE HARMFUL EFFECTS ON PLANTS AND WILDLIFE

* Be aware that plants and animals are also sensitive to light; some are strongly affected by blue wavelengths whereas others may be more strongly affected by other colours.

* Use outdoor lighting only when and where needed and ensure light does not spill into unintended areas.

* Change the colour of outdoor light by filtering or by changing the light source if it will benefit species in your area.

TIPS TO REDUCE HARMFUL EFFECTS ON THE NIGHT SKY

* Be aware that light pollution reduces our ability to see features in the night sky.

* Reduce light pollution by using outdoor lighting only when and where needed; ensure light does not spill upwards or into unintended areas; and select amber or warm white sources over those with higher blue emissions.

* Modify the lighting of communities, parks, reserves and sanctuaries so that they meet international standards for good outdoor lighting practice set out in the Dark Sky Places Program.