An ounce of prevention is worth a pound of cure.

- Benjamin Franklin

How Light Pollution Affects Human Health

There are many organizations and web pages out there that strive to collect money from you to find a cure to breast cancer, such as those listed by the Tampa Bay Times (see #4, 6, 22, & 38). These pages do not do that. It is the philosophy of these pages to help prevent health problems in the first place by raising the awareness of a man-made factor that can increase their risk of occurring, of which seems to include certain cases of cancer. Just as there are many different paths that one can take to get to a particular designation, there are many possible sources or factors that can cause errors in our cell's genetic coding that lead to cancer. Understanding those sources and taking simple intelligent steps to avoid them should be our first response to maintain health. However, light pollution is one factor that is increasingly hard to avoid due to its pervasiveness in society and the fact that it is growing exponentially. It is one factor that we inflict upon each other, near and far. It is one factor that we pay each and every night to make. And it is one factor that anyone can help correct.

Disclaimer: I am not an expert in the fields of biology, neuroscience, endocrinology, or oncology. I am, by training, a physicist. What I'll try to cover here is predominately based on my introductory understanding of articles that I have read. These pages then are a limited and a quite incomplete coverage of the evolution of thought regarding this issue and in what time I have had to devote to it. Whether or not the evidence presented here proves to be true or not, I find them to be of sufficient importance, that I thought that it was a worthy usage of that time. These evolving pages contain a growing collection of reviews of papers about the issue. Each of the reviews will have key findings highlighted and the citations to the paper, with online links if possible, so that you can follow up and corroborate what I understand.

As a quick introduction (or just for those who are impatient), here is a recently covered article in a series about night work on CNN.com.

These pages are not a call for money. They are just a request that we all participate in ending light pollution by ensuring that we do not contribute directly to the problem and that talk about it to others to educate them. To know what to do to correct this problem from affecting yourself or your neighbors, head over to our Light Pollution Prevention page for ideas and tips.

So, does light pollution directly cause health problems? No. Unlike in astronomy, light itself is not the problem.

The next time that someone says to you that it's just light, tell them: no, light is our biological triggering input that suppresses a cascade of subtle, health improving functions that should naturally and nightly occur in our bodies. These functions include those that promote better sleep, fight depression, fight obesity, and consume free radicals which damage DNA and cells and so negate some risk factors for certain cancers. It is NOT just light.

Because more of us are sleeping in overly lit nights, light pollution is being investigated as a interfering, aggravating factor that suppresses natural melatonin levels in humans at night. This suppression simply pulls out the stops to cancer cell growth. The hormone melatonin normally impedes cancer cell growth and can even cause cancer cell death. In women, it does this by inhibiting the sex ovaries from releasing hormones can cause breast tissue cells to replicate. Frequent genetic replications can increase the chances of transcription or genetic copying errors that can give rise to cancerous growth. The papers linked below examine these effects in greater detail. Once you are done here, you may want to head over to our Prevent Light Pollution page to find what steps you can take to end this problem for yourself and others.

The papers that have been reviewed are reorganized by subject and by date in this listing. I have commented on them in a chronological sequence below.

• Factors and conditions that reduce human melatonin levels, which then stimulates breast cancer
  • Excerpt of the Melatonin Summary from the National Cancer Institute
  • Role of pineal gland in aetiology and treatment of breast cancer.
  • Two letters responded to pineal gland aetiology and breast cancer.
  • Cohen, Lippman and Chabner reply to the two letters about their Pineal Gland and Breast Cancer review
  • Effect of Melatonin on Mammary Carcinogenesis in Intact and Pinealectomized Rats in Varying Photoperiods
  • Melatonin: a potent, endogenous hydroxyl radical scavenger
  
  
• How Society's Light Pollution affects Human Breast Cancer
  • Geographic Patterns of Breast Cancer in the U.S.
  • Electric Power Use and Breast Cancer: A Hypothesis
  • Inverse association between breast cancer incidence and degree of visual impairment in Finland
  • Night Shift Work, Light at Night, and Risk of Breast Cancer
  • Rotating Night Shifts and Risk of Breast Cancer in Women Participating in the Nurses' Health Study
  • Blocking Low-Wavelength Light Prevents Nocturnal Melatonin Suppression with No Adverse Effect on Performance during Simulated Shift Work
  • Melatonin-Depleted Blood from Premenopausal Women Exposed to Light at Night Stimulates Growth of Human Breast Cancer Xenografts in Nude Rats
  • Light at Night Co-distributes with Incident Breast but not Lung Cancer in the Female Population of Israel.
  • Light-at-night, circadian disruption and breast cancer: assessment of existing evidence
  • Does the Modern Urbanized Sleeping Habitat Pose a Breast Cancer Risk?
  • Circadian and Melatonin Disruption by Exposure to Light at Night Drives Intrinsic Resistance to Tamoxifen Therapy in Breast Cancer
  
  
• Lights at night and Prostate Cancer Risks in Men
  • Prospective Cohort Study of the Risk of Prostate Cancer among Rotating-Shift Workers: Findings from the Japan Collaborative Cohort Study
  • Global Co-Distribution of Light at Night (LAN) and Cancers of Prostate, Colon, and Lung in Men.
  • Melatonin May Lower Prostate Cancer Risk
    Urinary melatonin levels, sleep disruption, and risk of prostate cancer
  
  
• Health Association Viewpoints on Light Pollution affecting Human Health
  • IARC Monographs Evaluates the Carcinogenic Risks of Shiftwork to Humans
  • American Medical Association UNANIMOUSLY passes Resolution 516 against Light Pollution
  • American Cancer Society adds night work as a breast cancer risk factor
  
  
• A New Possible Link Between Light Pollution and Obesity!
• Other sites about the negative health effects of light pollution

Obesity is now the second leading cause of preventable premature death in the United States (after smoking), and accounts for approximately 400,000 deaths per year, its almost 8 percent of the total cost of illness and is growing. The next article may give a hint why:

A New Possible Link Between Light Pollution and Obesity?

Foodconsumer.org has a page that shows another resulting effect of light pollution -- obesity. They report our biological nights, defined as the period between the onset and cessation of melatonin secretion shortens due to light pollution. Our bodies then act as if it is Summer All the Time. Our body clocks evolved to fit the lifestyles of our hunter-gatherer ancestors, who had no artificial lighting. They may have slept less in the longer days of summer, which was also the time for storing up fat reserves for the leaner winter ahead. But in today's common sleep-deprived, electrified modern lifestyle may be telling our internal clocks it's summer all the time. Combined with readily available food year-round and you have a simple prescription for substantially increased caloric intakes, and thus greater obesity.

The short sleep durations could be a signal to our metabolic regulatory systems that it's summertime-it's time to go out, gain weight, build up fat reserves, to prepare for winter.
-- sleep epidemiologist Jim Gangwisch, University of Columbia

Other information and sites about the negative health effects of light pollution

Other sites about the negative health effects of light pollution to check out are:

• A new study reports that lights on at night can worsen smog conditions for a city. For those that want to work to improve the health conditions for people in overly lit cities, not only does one need to heed what is described below but also you can improve the air by turning the lights off at night so smog components can get naturally cleaned up. Jump to the link provided to learn more.
  
  
• ScienceNews has been following the problems of light pollution's effects on human health in a series of articles.
  
  
• The SkyKeepers.org out in California has their own Light At Night (LAN) and Health page covering additional articles and reports on the effects of lights at night and human health.

When I think about the term "light pollution", I know that it sounds extreme. However, when one considers the damaging effects it causes us and the animals out in the wild, one realizes that light pollution is just as damaging as a toxic chemical spill across the land. The results are almost the same. The difference is that with light pollution, we keep paying for and consuming energy resources, night after night, just to re-make this very same pollution, which we could so easily correct if we just put in some effort. In short, stop harming yourself and others in society. Just turn the lights off.