Why you should turn off the light

Wednesday, Jul 1, 2015, 11:57 PM | Source: Pursuit

Margaret Grose

While lights may make our streets safer after dark, artificial light at night has been shown to pose a range of health risks.

Dr Margaret Grose, senior lecturer in Landscape Architecture at the Melbourne School of Design, argues urban planners need to consider the health implications associated with street lighting, as well as the safety and environmental issues.

“Artificial light at night (ALAN) disrupts the production of melatonin in the human body, which regulates everything from our sleep/wake cycle to our mood, energy and appetite. According to the American Medical Association it’s a sleeping giant,” she says.

Medical concern about ALAN has grown since a ground-breaking 1980 study published in Science, which showed that light suppresses melatonin secretion in humans. Melatonin acts as an anti-carcinogen for a variety of tumours, and production of the hormone naturally increases in the human body between 9pm and 7am, hours traditionally associated with darkness.

Inher paper published in the Health Promotion Journal of Australia last year, Dr Grose wrote: “In 2007, the World Health Organisation declared that ALAN (artificial light at night) is a carcinogenic risk factor for shift-workers exposed to light during normal sleeping hours.

But it’s not just shift-workers who need to be concerned. Light at night is an issue that spans urban design, population health research, and areas of public governance.

Termed “light trespass”, street lights that beam into a house can also interrupt the sleep/wake cycle, which morphs urban design into a public health issue.

Research suggests street lights can interrupt our sleep

Dr Grose says there is an opportunity for Australian councils to address the health issues associated with streetlights now, as many are updating their old stock. Once updated, the new lights are likely to remain for 20 – 25 years.

However, old public lights are currently being replaced across Australia with the more energy-efficient LED bulbs. Although the energy-efficiency level of the LED bulbs is higher, the fact that they are brighter, and emit a bluer light, is of concern.

Professor Trichur Vidyasagar, a neuroscientist with the University of Melbourne, explains the nerve cells at the back of the eye contain a special pigment that is sensitive to blue light, which is found in the undertone of white lights.

These cells help to control our circadian rhythms, so too much exposure to these lights at night can cause rough sleep, he said.

“Just seconds to minutes of exposure to white light can impact our sleep patterns, moods and some cognitive functions.

Professor Vidyasagar says it’s best to avoid very bright lights altogether, to block out excessive white light and to use lamps with a yellow hue emitted by incandescent bulbs.

“It’s true that light is being looked at as therapy for a range of disorders, but for most people, it’s better for your health to avoid over-stimulating that system in the brain which should remain dormant at night.”

But it’s not all doom and gloom. Decreasing the health risks associated with streetlights is relatively straightforward, says Dr Grose.

“In contrast to many issues of creating healthier built environments, changes to street lighting can be carried out rapidly,” said Dr Grose. “Solutions like the installation of shields to prevent or reduce light trespass into bedrooms, dimming lights or turning lights off later in the night are all options.

“We can also change the spectrum of lighting used, from the blue end to the red end,” she says.

Dr Grose has recently been awarded a grant on Improving artificial light at night, to involve a pilot study of light intrusion into homes in Melbourne to be completed by December 31st 2015. Dr Grose will also host a workshop with local Government and industry to determine their issues about revised public lighting.

Headline and insert images sourced from Flickr and published under Creative Commons

University of Melbourne Researchers