Ill Health

“Many species (including humans) need darkness to survive and thrive.” American Medical Association Council on Science and Public Health (2012)


Exposure to artificial light at night can harm your health
Humans evolved to the rhythms of the natural light-dark cycle of day and night. The spread of artificial lighting means most of us no longer experience truly dark nights

Research suggests that artificial light at night can negatively affect human health —increasing risks for obesity, depression, sleep disorders, diabetes, breast cancer and more.


Circadian Rhythm and Melatonin
Like most life on Earth, humans adhere to a circadian rhythm — our biological clock — a sleep-wake pattern governed by the day-night cycle. Artificial light at night can disrupt that cycle.

Day and Night

Our bodies produce the hormone melatonin in response to circadian rhythm. Melatonin helps keep us healthy. It has antioxidant properties, induces sleep, boosts the immune system, lowers cholesterol, and helps the functioning of the thyroid, pancreas, ovaries, testes, and adrenal glands. Nighttime exposure to artificial light suppresses melatonin production.



Shiftwork that involves circadian disruption is probably carcinogenic (cancerous) to humans.”— International Agency for Research on Cancer (2007)   


building at night

Not All Artificial Light Is Created Equally
Exposure to blue light at night is particularly harmful. Unfortunately,most LEDs used for outdoor lighting — as well as computer screens, TVs, and other electronic displays — create abundant blue light. 

To minimize harm from blue light, choose the right light bulb and download a color temperature app that adapts your electronic screen to the time of day – cool light during the day and warm light at night.


Color temperature apps:

  • F.lux is available for Mac OS/X, Windows, Linx, iPhones and iPads
  • Flux is available for Android devices (free or pay )
  • Twilight is available for smartphones or tablets



Choosing the Right Bulb

In the picture on the right, the bulb on the left is rich in high-color temperature blue light, while the one on the right is not.

Be sure to look at the packaging. All packaging for new CFL & LED light bulbs provide color temperature information. Use low color temperature light sources for interior and exterior light. Their light is less harsh and less harmful to human health and theenvironment. Look for warm white sources with a color temperature of 3000K or lower.

Bulb vertical

The Kelvin temperature chart below shows you what the numbers mean.

Kelvin scale






Higher color temperatures mean bluer light, the kind that should be avoided after dusk.




antique-night Kelly Beatty

Glare from Bad Lighting is a Safety Hazard

Glare from poorly shielded outdoor lighting is also harmful to your health, because it decreases vision by reducing contrast. This limits our ability to see potential dangers at night. Aging eyes are especially affected. 

The glare of the outdoor street lighting on the right makes it harder for drivers and pedestrians to see.

"Glare from nighttime lighting can create hazards ranging from discomfort to frank disability."  — American Medical Association Council on Science and Public Health (2012)




Light at Night and Human Health Videos

Prevent Light Pollution for Your Health from What You Can Do on Vimeo.

Learn about light at night and human health from Night Sky Ranger Kevin Poe in just one minute.



Researchers explain how they measured the circadian rhythms of people following their everyday routines and then sent them camping in the woods for a week. When exposed to a more "natural" light-dark cycle, the researchers found that, surprisingly, later risers dramatically shifted their clocks, now exhibiting a rhythm more like early risers.


Recent Health News

  • The end of night 
    An eternal electric day is creeping across the globe, but our brains and bodies cannot cope in a world without darkness. Read more.
  • AMA Addresses Light Pollution (Sky & Telescope)
    Researchers are raising several possible health concerns related to nighttime light exposure, among them a higher risk of cancer. Read more.
  • LED streetlights save energy, but could have some serious side effects
    Exposure to blue-rich LED lights can disrupt natural circadian rhythms in humans and wildlife. Read more.
  • Resetting internal clocks may call for a camping trip, study shows (
    Before the days of electric light, most of the earth’s population went to bed with the sunset and awoke with the sunrise. A new study sheds light on what may be a need to return, if not for a small time, to our ancestral schedule. Read more.
  • Night work 'throws body into chaos'
    Shift work has been linked to higher rates of type 2 diabetes, heart attacks and cancer. Read more.
  • Melatonin linked to prostate cancer risk (Live Science)
    Men with higher levels of the sleep hormone melatonin may be less likely to develop prostate cancer, a new study suggests. Read more.
  • iPads, smartphones, TVs rob Americans of sleep, Harvard Medical School scientists say
    "We have biologically shifted ourselves so we can't fall asleep earlier," said Charles A. Czeisler, a  professor of sleep medicine at Harvard Medical School. "The amazing thing is that we are still trying to get up with the chickens." Read more.
  • Desperate for a good night's sleep? Putting a red bulb in your bedside lamp might do the trick, but, from weight gain to insomnia, research suggests artificial light may wreak havoc on your health Read more.