High-power Light at Night a Carcinogen

HAIFA, Israel, Sept. 6 (UPI) — Israeli researchers call “environmental light pollution,” or high-power light at night, a carcinogenic pollution.

Researchers at the Center for Interdisciplinary Chronobiological Research at the University of Haifa in Israel have linked light at night, especially environmental light pollution to greater cancer growth. They suggest this is due to lessened production of melatonin — a hormone released by the pineal gland during the dark hours of the day.


Study leader Abraham Haim and colleagues divided lab mice injected with cancerous cells into four groups: Long days — 16 hours of light/ 8 hours of darkness; long days but treated with melatonin; short days — 8 hours light/16 dark hours — and short days but exposed to a half-hour of light during the dark hours.

The study found the smallest cancerous growths in mice with short days. Mice with short days but exposed to light during dark hours had larger growths — averaging a cubic half-inch. The mice exposed to long days had growths averaging 2 cubic inches.

However, “long days” mice treated with melatonin had small tumors — similar in size to those of “short days” mice. Melatonin-treated mice — versus untreated mice — had significantly lower death rates.

“Exposure to light at night disrupts our biological clock and affects the cyclical rhythm that has developed over hundreds of millions of evolutionary years that were devoid of light at night,” the researchers said in a statement.

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Categorized | Light Pollution, Other
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