Second in a three part Dark Sky series
“Darkness is as essential to our biological welfare, to our internal clockwork, as light itself.” -Verlyn Klinkenborg, “Our Vanishing Night,” National Geographic magazine, November 2008
Last week in the first article of our three part series on Dark Skies , we took a look at the Dark Sky movement, some of the impacts and examples of light pollution here in the Denver area, and considered ways to choose exterior lighting fixtures that do not contribute to light pollution.
The effects of light pollution run far deeper than wasted energy in the form of light directed at the skies and minimized visibility of stars. More insidious impacts of light pollution are engaging a wider community than astronomers and sustainability advocates, such as cancer researchers and sleep experts.
From an evolutionary standpoint, human lives have long been regulated by night (dark) and light (day) cycles. Light/dark cycles regulate our internal timeclocks, or circadian rhythms, and are critical for the production of hormones and immune system function.
For thousands of years, our ancestors woke with the rising sun and went to sleep when cued by darkness. Until the industrial era, firelight, and later, gas lamps, were the only “artificial” light available after nightfall. Even then, artificial light was characterized by a golden glow similar to the warmth of a dimmed incandescent bulb.
Our nighttime world stands in marked contrast to this. Viewing a map of the earth at night, our cities glow like stars in the sky, and we have worked assiduously to render the night a replica of day time through excessive use of artificial light, certain that this makes us more secure.
What have we accomplished? Numerous studies indicate that high levels of artificial light do not create a safe night environment. In our quest for security, we have managed to skew circadian rhythms and, in the last 80 years alone, render more damage to our ability to sleep, our immune system function, and our blood sugar regulation than our predecessors managed to achieve in thousands of years.
Various studies from locations around the globe show increased cancer risk among women in industrialized countries, as well as shift workers. What do these people have in common? Exposure to artificial light at night.
Dr. George Brainard, a researcher at George Washington University who studies the impact of light on sleep cycles, notes the impact of a light on participants in sleep lab research. Participants slept in a completely darkened room. After control data was taken, a light emitter the size of a dime was taped to the back of each participant’s knee. The effect of this minimal amount of light on the skin? Sleep cycles were significantly disrupted, and immune system function was suppressed. Any light exposure at night, particularly in the cooler (more blue) portion of the light spectrum, suppresses melatonin production, which in turn promotes wakefulness. And with melatonin suppression comes diminished Natural Killer cell (NK) and T cell production, the front line of immune system function.
The danger of night time light’s effect on human health is significant enough that the conservative American Medical Association (AMA) has voiced a formal position decrying the impacts of light pollution and recommending immediate action to minimize it. According to the AMA, “Light trespass has been implicated in disruption of the human and animal circadian rhythm, and strongly suspected as an etiology of suppressed melatonin production, depressed immune systems, and increase in cancer rates such as breast cancers.” Find more information on this important step in supporting Dark Sky legislation here.
As individuals, we can take action in our homes to guard ourselves against the effects of light trespass. Add blackout curtains or blinds in bedrooms to make sure they are completely darkened at night. If a light is required, such as in a child’s room, use a nightlight in the amber or red portion of the spectrum, which is shown to have much less impact on the dark-adapted eye and circadian rhythm than light in the blue portion of the spectrum. Talk to neighbors to respectfully request that their glaring spot light is redirected and shielded.
The next step is to eliminate the sources of light trespass outside the house. In our third and last article in this three part Dark Sky series, we will consider ways to interact with the community at large to promote Dark Skies and enact regulations for Dark Sky compliant lighting.