Light pollution is becoming as much of a threat to the health of the planet as holes in the ozone layer, experts believe.

The amount of artificial light humans are being exposed to is increasing at double the rate of population growth, delegates at the New Zealand Starlight Conference in Tekapo were told this week.

Marnie Ogg, founding director of the Australasian Dark Sky Alliance (ADSA), said while the effects of light pollution were still being determined, it was important action was taken now to offset the worst of the potential effects.

Eating, sleeping and breeding patterns are all guided by circadian rhythms and artificial light can alter these rhythms, affecting food and water availability and animal behaviours, Alicia Dimovski of La Trobe University, Melbourne, said.

Whilst a summary of evidence on the impact of blue light on health produced by the Royal Society Te Apārangi was inconclusive, preliminary evidence indicates high levels of light exposure, particularly blue light, can contribute to health problems.

“In humans, there is research supporting the impact that the disruption of normal circadian rhythms has on mood disorders, such as depression, as well as cognitive dysfunction, increased risk of obesity and some types of cancer.”

Dimovski studied the affects of total darkness, amber light and white light on the nighttime activity, energy consumption and reproduction of fat-tailed dunnarts, a species of mouse-like marsupial.

She found white LEDs (light-emitting diodes, an energy efficient alternative to traditional light bulbs) had a significant impact on behaviours, causing delayed activity and increased food consumption but decreased body mass and fat mass.

“One possible explanation of this could be attributed to increased stress caused by the individuals under continuous illumination, leading to an increase in resting energy requirements.”

Other studies in Australia have shown artificial lights disorientate endangered marine turtles trying to make it to sea; prevent hatching of clownfish; decrease prey availability for the mountain pygmy possum; and change the growth, timing of flowering and resource allocation in plants.

“We need to better understand our ecology in order to put in the best lighting,” Dimovski said.

“If we take into account lighting colour, direction, duration and intensity and match the best lighting to our needs we can avoid wasted light, wasted energy, save money and ultimately make a [better] future for us and animals.”

The Australian government is developing light pollution guidelines to protect its ecology, presented at the conference by Karen Arthur, Australian Department of the Environment and Energy.

“The aim is that light will be managed so that wildlife is not disrupted within, or displaced from, important habitat and is able to undertake critical behaviours such as foraging, reproduction and dispersal,” Arthur said.

This is being developed through educating on best practice lighting design, environmental impact assessments and sharing case studies to limit artificial light and sky glow within 20km of important habitats.

Globally, there has been much more research into the impact of light upon human health.

Sean Cain, associate professor of sleep and circadian medicine at Monash University in Melbourne, explained “every cell in our body is a clock”.

The hormone melatonin which maintains our 24 hour circadian rhythm and therefore bodily processes such as temperature, cortisol levels and metabolism, is easily confused by light, he said.

“We now have total control of our light and this is problematic,” Cain said.

“If you take the whole of human evolution and put it into a 24 hour day, we’ve only been in control of our light for about 77 seconds, we didn’t evolve to be able to make good choices about our light environment.”

Earlier this year Cain published research into individual responses to light and found on average 24.6 lux (the unit of illuminance, equal to one lumen per square metre) is enough to suppress melatonin secretion by 50 per cent.

A full moon emits about 1 lux while a single 114W 4000 kelvin LED streetlight can produce 20 lux.

Alexander Tups, Centre for Neuroendocrinology and Brain Health Research Centre, explained melatonin not only maintains the 24 hour circadian rhythm, it is the most important antioxidant, an antiinflamatory, antihypertensive, antithrombotic and antilipidemic.

“The likely consequences of frequent circadian disruptions [are] sleep disorders, cancer, depression, dementia, obesity and diabetes,” he said.

“We need to urgently design a study that investigates the effects of LED street lighting on melatonin levels. Who is liable if the streetlight outside your house gives you cancer?”

Policy inspiration could be taken from the Canary Islands where the dark sky is protected as a human right, director of the starlight foundation, Antonia Varela Perez said.

The ‘Declaration in Defence of the Night Sky and the Right to Starlight’ was developed in 2007 between global organisations including the United Nations Educational, Scientific and Cultural Organisation (UNESCO) and the Convention on the Conservation of Migratory Species of Wild Animals.

The policy is based upon the dark sky as a human right, stating “an unpolluted night sky that allows the enjoyment and contemplation of the firmament should be considered an inalienable right of human kind equivalent to all other environmental, social and cultural rights, due to its impact on the development of all peoples and on the conservation of biodiversity.”