Ecology Archives

artificial light

[ Ecology Archive ]
[ Main Archives Page ] [ Glossary/Index ]
[ FAQ ] [ Recommended Books ] [ Bulletin Board ]
   Search this site!

artificial light & cancer

Posted by
Marion [3232.1399] on January 19, 2005 at 06:42:31:

Hi all,

I found the interesting article below on the link between artificial light and cancer. Other articles I red were suggesting that artificial light is causing not only cancer, but also addiction, infertility, diabetes, mental illness, heart problems etc.


It was the opening session of a workshop exploring the effect that artificial light has on breast cancer risk, and University of Connecticut epidemiologist Richard Stevens showed an aerial slide of the United States by night. Dots of white city lights twinkled against the blackness, coalescing into splotches in areas of high population density.

The pattern recalled maps showing the geographical distribution of breast cancer rates, with the high-incidence areas along the northeast coast, the Great Lakes’ boundary, and in the coastal cities of California.1 The image neatly captured the hypothesis that participants would consider for the next two days at the conference (“Circadian Disruption as Endocrine Disruption in Breast Cancer,” sponsored by the National Action Plan on Breast Cancer): that artificial light at night is a type of pollution that contributes to breast cancer.

The hormone melatonin is produced at night and regulates circadian rhythms, our daily wake-sleep patterns. Give people melatonin supplements and they nod off. Artificially reverse light and dark, and melatonin production switches accordingly; so do sleep rhythms. As we age, calcium deposits accumulate in the pineal gland, which produces melatonin—and some researchers suspect that both melatonin levels and hours of sleep may be diminished as a result.

Melatonin has cancer-fighting properties. Seventy-five percent of cancer shows oxidated DNA damage. Melatonin rivals vitamin C in its ability to counteract the oxidating effects of estrogen and radiation.

The discovery that the pineal gland actually secretes something dates only to the 1970s, but this hormone of darkness is ancient. Species at all evolutionary levels, from algae to moths to humans, secrete melatonin at night. Nature tripped these circadian switches until a century ago, when Thomas Edison invented electric light. We in the industrialized North can now choose from 15,000 sources of artificial light to shorten our long winter nights.

“If light were a drug, I’m not sure the Food and Drug Administration would approve it,” Charles A. Czeisler quipped in the Medical Tribune last year. Even tiny slivers of light at night disrupt the melatonin levels of rats, promoting tumor growth. Removing the pineal gland in rats stimulates tumor growth, and melatonin inhibits the growth of estrogen-receptor-positive (ER+) breast cancer cells in vitro by 30 to 40 percent. This leads researchers to speculate that reducing our exposure to light at night might decrease rates, and that pharmacological use of melatonin may be effective in treating cancer.

Research Findings

Josephine Arendt, a professor at the Centre for Chronobiology in Surrey, England, became interested in melatonin after she was diagnosed with breast cancer 19 years ago. Her work illustrates the difficulty of testing hypotheses with real-world studies. Comparing blood serum melatonin levels of sighted individuals living in the United Kingdom with those of blind people and inhabitants of parts of Antarctica where the sun does not rise at all for three months, Arendt found no significant differences. Two studies of profoundly blind women have found lower breast cancer rates, as predicted, in this population; a third study did not.

Arendt also found no differences between melatonin levels in women with benign and malignant breast tumors (an American study has found a difference). Since melatonin levels diminish with age, Arendt stresses that epidemiological research should control for this variable. Small pilot studies are inherently limited but, as Arendt observes, “these studies are not cheap, and it’s hard to get funding for a large, prospective study with negative pilot data.”

Epidemiologist Richard Stevens, meanwhile, points to a study that found elevated breast cancer rates among Finnish flight attendants, noting that the incidence is too high to be accounted for solely by increased radiation exposure. Disruption of circadian rhythms might well be a causative factor in these cancers, he says. And alcohol disrupts sleep, which in turn could suppress melatonin, perhaps explaining why excessive alcohol consumption increases breast cancer risk.

Windows of Time

William Hrushesky, M.D., a clinical researcher at the Stratton VA Medical Center in Albany, New York, believes that research on cycles should extend beyond circadian rhythms to menstrual and seasonal cycles. We already know, he points out, about certain “windows of time” that can optimize the effectiveness of cancer therapy while reducing side effects. Cancer drugs should be administered in the morning, when bone marrow and gut proliferate at two to three times the nighttime rate. In a study of women with ovarian cancer, optimal timing of chemotherapy improved efficacy from 11 to 44 percent. Performing breast surgery in the early luteal phase of the menstrual cycle (days 14-21) yields a 25 percent advantage in ten-year survival over surgery in other phases, he says, while mammography screening is less effective in the luteal phase. (The day menstrual bleeding begins is considered the first day of the cycle.) Pap smears for cervical cancer are more sensitive during the summer, Hrushesky says, and breast cancer is most often diagnosed in the spring.

“We are doing great harm because we ignore cycles,” he charges. His work has been ridiculed and ignored, he says, because of inertia and linear thinking in the research community. Although five prospective studies on the timing of breast cancer treatments are now in progress, he predicts that only one, an Italian study, is properly designed to yield meaningful results.

Translating the Data

While little of the research that exists on circadian rhythms is definitive and can be translated to real-world practice, some lends itself to an approach based on the best-available evidence. The good news is that starlight, moonlight, and lightning all fall outside the spectrum of light that depresses melatonin. Researchers speculate that the body is made aware of lighting not through vision but through another system in the retina—so if your bedroom window is next to a street light, eye shades or a light-tight blind are harmless ways to keep the melatonin flowing. Red-spectrum light is least disruptive and therefore best for night lights or clocks with illuminated time displays; blue-green light is most disruptive.

For advocates, research into circadian rhythms offers plenty of scope for action. Melatonin is a product that can’t be patented, which suggests why research into its therapeutic potential is so sluggish. Also, circadian rhythms lie outside the realm of much of cancer research, so proposals are more apt to flounder. Finally, as William Hrushesky argues, we need to put hard-won knowledge about “windows of time” to better use.

For me, the National Action Plan on Breast Cancer’s workshop recalled an early radicalizing experience, a 1991 conference at which Congressional representative Pat Schroeder blasted cancer researchers for excluding women from clinical trials. Because women’s cyclical physiology doesn’t fit the linear shoe of fashionable science, she charged, “they even used male rats to study breast cancer.” Finally, a critical mass of researchers is saying that cycles matter.

Re: artificial light & cancer

Posted by Ron [1013.1671] on January 19, 2005 at 12:59:35:

In Reply to: artificial light & cancer posted by Marion [3232.1399] on January 19, 2005 at 06:42:31:

Hi Marion,

I can remember this being discussed in the winter almost every year for the last 10 years or so.
This is an old topic under a slightly different name.
Could it be that the media is actually looking for things
to write about because it is a slow news week in the dark winter?
All I did was a search in google on "night shift cancer risk" and got a lot of returns.

If this is true, it is going to set back the women's movement by decades as the nightshift workers stay home in droves out of fear of breast cancer.
(Just like the cel phone has been discarded by the millions who fear brain tumours.) Yah! Right!

Here is a list of links which you will se go back at least since 2001 when "USA Today" wrote about it.

Follow Ups:

Re: artificial light & cancer

Posted by ANN [1003.516] on January 19, 2005 at 14:11:16:

In Reply to: artificial light & cancer posted by Marion [3232.1399] on January 19, 2005 at 06:42:31:

thanks for a good article-nice to see you're still with us.
William Campbell Douglass MD writes about fluourescent lights being associated with skin cancer. He cites studies in which skin cancer rate is much higher among office workers than lifeguards and he encourages people to avail themselves of sunlight for their health.

Re: artificial light & cancer

Posted by Ron [2014.1671] on January 19, 2005 at 17:08:27:

In Reply to: Re: artificial light & cancer posted by ANN [1003.516] on January 19, 2005 at 14:11:16:

Hi Ann,

That could have to do with the lack of Vitamin D which is a problem for night workers.

Unles the lights are full-spectrum like grow-lights, there is no vitamin D generated in the body from the rays.

I'll bet that Cod Liver Oil is also not on the list of things to take when you talk to a shift worker.


Follow Ups:

Re: artificial light & cancer (Archive in ecology.)

Posted by Walt Stoll [9.1465] on January 20, 2005 at 08:36:51:

In Reply to: artificial light & cancer posted by Marion [3232.1399] on January 19, 2005 at 06:42:31:

Thanks, Marion.

Points up the absolute need to maintain an open and scientific mind, doesn't it? This is something that a monopoly has no use for: "Keep things the same since they are so good right now."


Follow Ups:


Posted by
tom [3394.1837] on March 02, 2005 at 18:16:05:

In Reply to: artificial light & cancer posted by Marion [3232.1399] on January 19, 2005 at 06:42:31:

contact me at

TOTALLY VOICE ACTIVATED PHONE SYSTEM: BRAND NEW IN BOX. Just say hello, and speakerphone answers a ringing phone. To dial out, just say the name of person (after programming), and it dials that
telephone number. Automatic hang-up. 3 phones in 1, voice activated, handset or just regular speakerphone. $100 delivered.

True Hands free voice recognition speaker phone. Memory preset up to 60 names. Voice Command auto dialing & answering. Auto hang up on busy tone or no answer. Optional digit dialing capability. You can
use as a regular telephone or speakerphone. 3 phones in 1. Easy to program and use. $100 delivered


Follow Ups:

[ Ecology Archive ]
[ Main Archives Page ] [ Glossary/Index ]
[ FAQ ] [ Recommended Books ] [ Bulletin Board ]
   Search this site!