How Light Pollution is Ruining Your Health

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November 20, 2008 | 51,113 views

Humans are diurnal creatures, with eyes adapted to living in the sun's light. Because of this, we’ve engineered the night for our own comfort by filling it with light.

Light pollution is largely the result of poor lighting design, which allows artificial light to shine outward and upward into the sky. Wherever human light spills into the natural world, some aspect of life -- migration, reproduction, feeding -- is affected.

Scientists speak of songbirds and seabirds being "captured" by searchlights, circling and circling in the thousands until they drop. Migrating birds are apt to collide with brightly lit tall buildings. Many nocturnal mammals forage more cautiously under the permanent day of light pollution, because they've become easier targets for predators.

Like most other creatures, humans need darkness. The regular oscillation of waking and sleep is a biological expression of the regular oscillation of light on Earth. At least one new study has suggested a correlation between higher rates of breast cancer in women and the nighttime brightness of their neighborhoods. This was a fascinating article in National Geographic. I subscribe to this magazine for the amazing nature photography, but this was an excellent article on a health topic.

Light pollution refers to “any adverse effect of artificial light, including sky glow, glare, light trespass, light clutter, decreased visibility at night, and energy waste,” writes the International Dark-Sky Association (IDA).

Obvious examples would be the glow that can be seen from miles outside of a big city, or the absence of stars in the night sky if you live in an urban environment. More subtle examples of light pollution are the strips of light that come in around your curtains at night, or even the glow from your clock radio. All of these have the potential to negatively impact your health and the natural rhythms of nature. IDA writes:

“Light pollution wastes energy, affects astronomers and scientists, disrupts global wildlife and ecological balance, and has been linked to negative consequences in human health.”

One such consequence is cancer.

How Light Pollution May Cause Cancer

While it’s typically thought that your biological clock is what tells you when it’s time to wake up or go to sleep, light and dark signals actually control your biological clock. To get more specific, a part of your brain called the Suprachiasmatic Nucleus (SCN) -- a group of cells in your hypothalamus -- controls your biological clock. And the cells that make up your SCN respond to light and dark signals.

Light actually travels through your eye’s optic nerve to your SCN, where it signals your body’s clock that it’s time to wake up. Light also signals your SCN to initiate other processes associated with being awake, such as raising your body temperature and producing hormones like cortisol.

Meanwhile, when your eyes signal to your SCN that it’s dark outside, your body will begin to produce melatonin The level of melatonin produced is related to the amount of exposure you have had to bright sunshine the previous day. The less bright light exposure the lower your melatonin levels. 

Melatonin is known as a hormone that helps you sleep and radically decreases your risk of cancer. There are many studies on this powerful association. The more your sleep is disrupted by light pollution, the lower your melatonin levels and the greater your risk of developing cancer becomes.

Melatonin is secreted primarily in your brain and at night it triggers a host of biochemical activities, including a nocturnal reduction in your body's estrogen levels. It’s thought that chronically decreasing your melatonin production at night -- as occurs when you’re exposed to nighttime light -- increases your risk of developing cancer.

In fact, one of the first studies linking cancer to light showed that blind women have a 36 percent lower risk of breast cancer compared to sighted women. Why? Because they are unreceptive to light. This means that their bodies maintain high melatonin levels at night regardless of how much light is in the room.

Artificial Light’s Impact on the Environment

Organisms evolved to adjust themselves to predictable patterns of light and darkness. Once artificial light effectively varied the length of a day, something that happened less than a century ago, the average night's sleep decreased from around nine consistent hours to roughly seven, varying from one night to the next.

The irregularity prevents circadian rhythms from adjusting to a pattern, and creates a state of permanent "jet lag." This is true not only in humans but in many other species as well. IDA lists many of the far-reaching effects that light pollution has on the environment:

• Lighted towers and tall buildings confuse migrating and local birds, causing them to collide or circle the lights until they die of exhaustion.
• Sea turtle hatchlings are meant to crawl toward the ocean, guided by the light of the moon. Coastline lighting confuses them, drawing them away from the ocean instead of toward it.
• Glowworms and fireflies communicate through light, and artificial lighting makes this difficult.
• Intense lights for fishing at night attract large numbers of fish, leading to over-fishing and contributing to the decline of fish worldwide.
• Nighttime lighting from sports stadiums can stop the mating activity of nearby frogs.

So while electricity and efficient lighting have clearly provided major benefits to society, these benefits come with a price. A sensible solution, as IDA suggests, is to use outdoor light at night only when and where it is needed and at appropriate lighting levels. They also suggest using fully shielded, light-efficient fixtures aimed directly at the ground, and incorporating timers and sensors to shut off lights when they’re not needed.

Conducting a Light Check in Your Bedroom

Sleeping in a pitch-black bedroom is an important and relatively easy lifestyle choice to make for your health. Even the dim glow from your clock radio could be interfering with your ability to sleep, and more importantly, your long term health and risk of developing cancer.

Personally, I sleep in a room that is so dark, that I can’t see my hand in front of my face. If your bedroom is currently affected by light pollution, you will notice a major improvement when you eliminate it.

To get your room as dark as possible:

• Install blackout drapes
• Close your bedroom door if light comes through it, and even put a towel along the base to prevent light from seeping in
• Get rid of your electric clock radio (or at least cover it up at night)
• Avoid night lights of any kind
• Keep all light off at night (even if you get up to go to the bathroom) -- this includes the TV!

If you are interested in finding more information on this vital subject, I highly suggest reading Lights Out: Sleep, Sugar, and Survival by T. S. Wiley and Bent Formby. The authors believe that it is light, not what we eat or whether we exercise, that causes obesity -- and diabetes, heart disease and cancer. I recently had the pleasure of meeting Dr. Wiley at a conference I attended.

Now, if it’s been awhile since you’ve had the luxury of gazing up at a truly dark night sky, you might want to plan your next vacation around it. IDA has an inspiring list of vacation spots in the United States and world where you can take stargazing to a whole new level.

[+]Sources and References [-]Sources and References