The Dark Side of LEDs: Suppression of Melatonin by Blue Light

You may have heard that blue light can disrupt your sleep. As it turns out, it’s also harmful to wildlife.

At an inner-city university, mobs of wallabies are helping researchers understand how artificial light affects nocturnal marsupials.

Alicia Dimovski, a graduate of La Trobe University, studies how exposure to light affects tammar wallabies.

In an enclosure, they were exposed to light-emitting diodes (aka LEDs). A second case had blue shielded LEDs, similar to the “night mode” setting on your phone or laptop. Wallabies in a third enclosure experienced natural darkness.

After 10 weeks, Alicia took blood samples to test the wallabies’ melatonin levels. As it turns out, LEDs have a dark side.

The “Hormone of Darkness”

Like us, wallabies depend on the hormone melatonin for a good night’s sleep. And the levels of melatonin produced in our bodies are regulated by a light-sensitive protein in our eyes called melanopsin. When certain wavelengths of light hit melanopsin, it suppresses our melatonin production. Reduced levels of melatonin in our blood could disrupt our body’s natural sleep-wake cycle.

“Melatonin is known as the ‘hormone of darkness,'” says Alicia.

“This is because the production of melatonin is suppressed by light and peak production occurs during the dark period.”

Melatonin is also important for the immune system. In mammals, melatonin acts as an antioxidant and scavenges free radicals.

Free radicals are unstable atoms created by the body as a byproduct of various normal cellular processes. Despite their potential to damage DNA and other cells, the body is perfectly fine with small amounts of free radicals. However, when we have an infection, the body’s immune response can cause an increase in free radicals. Without melatonin, this increase in free radicals can cause oxidative stress, which increases inflammation.

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Not all light activates melanopsin equally. Blue light with a wavelength between 420 and 440 nanometers activates melanopsin better.

In 2009, the Australian government began phasing out incandescent light bulbs in favor of energy-efficient alternatives such as LEDs.

Since then, LEDs have been the main light source for Australian homes, shops and street lamps. Unfortunately, energy-saving light bulbs cause health problems for nocturnal wildlife.

After 10 weeks of exposure to nocturnal LEDs, Alicia’s wallabies had lower melatonin levels.

“White LEDs cause problems because they contain a lot of blue light, so they’re very effective at suppressing melatonin,” says Alicia.

However, the study found that removing the blue light from the LEDs made a big difference in melatonin levels. In fact, the wallabies exposed to amber LED light had melatonin levels on par with wallabies experiencing natural darkness.

Sleepless in the suburbs

Aside from melatonin, for wallabies the changing light level during the four seasons is a timer for vital processes like reproduction.

“Animals that breed at a specific time of year, like tammar wallabies, rely on this biological clock to ensure births occur when there is enough food to raise their young,” says Alicia.

“Many Australian mammals have been shown to reduce their activity even during a full moon due to an increased risk of predation. Therefore, even very little light pollution can disrupt our wildlife.”

The WA Department of Biodiversity, Conservation and Attractions has issued guidelines for businesses to reduce light pollution. However, they are not required or enforced by law. Compliance with the guidelines is entirely voluntary.

“DBCA promotes the guidelines through training with industry and government agencies to ensure optimal lighting design and reduce the potential impact of artificial light on wildlife,” said a DBCA spokesman.

So if you find nocturnal wildlife’s best friend near your home, consider getting blue wavelength filters for your LEDs and placing them closer to the ground. They will love it!

This article first appeared on Particle, a science news website based at Scitech, Perth, Australia. Read the original article.