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The Webfooted Astronomer - November 2001


Nighttime Lighting May be Hazardous to Your Health

By Bruce Weertman

AS an astronomer you are probably aware that nighttime lighting causes sky glow that has increasingly obscured our view of the heavens. Perhaps you’ve read that nighttime lighting interferes with the migration of birds. But what you may not be aware of is that nighttime lighting might also be bad for your health!

Statistically, one out of nine women in the United States will develop breast cancer. This is three to five times the rate of non-industrialized nations. A clear cause for the increased risk of breast cancer in industrialized nations has yet to be discovered. Perhaps until now… Two recent independent epidemiological medical studies published in the Journal of the National Cancer Institute indicate that women who work night shifts are more likely to develop breast cancer than women who do not work night shifts.

In a paper authored by Scott Davis (Fred Hutchinson), Dana Mirick (Fred Hutchinson) and Richard Stevens (University of Connecticut), graveyard shift work was correlated with a 60% increase in breast cancer. Furthermore, the Davis et al. study suggests that women who sleep in relatively bright bedrooms are at an increased risk for breast cancer.

The mechanism for the increased risk probably has something to do with the hormone melatonin. Melatonin is produced by the pineal gland at night and is involved in circadian rhythm. Through a mechanism that is not completely understood, but involves the eye, light exposure suppresses the production of melatonin. Melatonin is a potential tumor suppressor.

Studies have shown that artificially reduced melatonin levels in rats with chemically induced tumors increase their rate of tumor growth. Furthermore, in women, melatonin reduces estrogen levels and high estrogen levels are associated with breast cancer. Whether shift work is associated with adverse health effects on men is not clear. More studies need to be made.

Although the graveyard shift studies do not directly address the broader issues of light pollution, they certainly serve to help the dark sky movement. Testimony by doctor Richard Stevens to various Connecticut state committees recently helped long time dark sky activist Cliff Haas “Slam Dunk” a Full-Cut-Off roadway lighting bill.

These medical studies show that light pollution isn’t just a problem for astronomers, but is a problem for everybody.

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