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As reported by the U.S. News and World Report, February 21, 2008.
Shedding Light On A Cause Of Breast Cancer
UConn Scientist Studying Treatment Derived from Patient’s Own Cells
By Ben Harder
When Edison invented the light bulb, did he accidentally spawn a
cancer epidemic? It's certainly starting to look that way. In study
after recent study, exposure to artificial light has been linked to
certain kinds of tumors, especially those in the breast.
Consider some of the evidence: Blind women have low rates of breast
cancer. So do women in underdeveloped countries, where artificial
lighting is an uncommon luxury. By contrast, female nurses and other
women who frequently work night shifts have high breast cancer rates.
The reason, experts believe, is that their schedules expose them to
illumination during what should be the darkest hours of their days, and
that disrupts the body's production of the cancer-suppressing hormone
melatonin. In lab experiments, human breast tumors have been found to
grow relatively quickly when fed by the blood of women who have been in
a brightly lit room in the middle of the night. When blood is drawn from
women who've been sitting in darkness, it's richer in melatonin and less
nourishing to the cancer.
Based on those and other observations, a unit of the World Health
Organization announced in December that shift work is a "probable human
carcinogen." But shift work may be merely the tip of Edison's epidemic.
In fact, any woman whose community is filled with streetlamps and
other light sources may face an unnaturally high risk of breast cancer.
A new study, slated to appear in the journal Chronobiology
International, finds that breast cancer incidence is about 73 percent
higher in communities with the greatest amount of artificial light at
night than in communities with the least. The researchers assessed
different communities' nocturnal light levels by analyzing satellite
images of how much illumination escapes into space. (You can see this
Washington Post article for details.)
Light pollution seems to have other untoward consequences, including
harmful
effects on animals like migratory birds and sea turtles. But the
apparently
carcinogenic effects of light pollution have received—and arguably
deserve—the lion's share of scientists' attention. No one has paid more
notice to the light-cancer connection than Richard Stevens, the
University of Connecticut Health Center epidemiologist who first
proposed a possible link more than two decades ago. Stevens collaborated
on the new study with four colleagues in Israel, and I asked him to
comment on its significance.
He was quick to say that the study falls short of proving cause and
effect. But it's consistent, he said, with the hypothesis that light at
night accounts for a "substantial fraction of breast cancer."
"Lighting the night is as important an ecological issue for the
planet as global warming," he added. "In addition to its effects on all
life forms, unnecessary lighting of the night accounts for a lot of
fossil fuel consumption and also contributes to global warming." |
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