Story originally printed in the Winona Daily News or online at www.winonadailynews.com
Published - Sunday, April 27, 2003
Shedding light on pollution: Illuminating the night might be a bad idea
When it comes to light pollution, most people are still in the dark.
The usual Earth Day pronouncements on pesticides, packaging, population and poop were joined by a cautionary against surplus nighttime illumination.
While Earth Day celebrants basked in the bright spring sunshine Saturday afternoon, Tina Thevenin, Minnesota contact for the International Dark Sky Association, warned that, to our possible peril, the light of day is no longer followed by the dark of night.
 Sylvia Thomas, a fifth-grader from Ridgeway Community School, hoists up her blue heron cut-out as she prepares to join the Earth Day Fair parade Saturday afternoon at Lake Park. Jenny Butler of the Winona Daily News |
Most people never experience a truly dark night, she said. Outdoor lighting - street lights, lighted advertising signs, vehicle headlights and security lighting - have robbed the night of its darkness in all but the most isolated areas. Acknowledging that some illumination is needed to safely navigate the nighttime environment, Thevenin pointed out that much of the light generated is either unnecessary or wasted. A photo of the nighttime earth taken from space clearly outlined the continental United States in points and broad splashes of illumination. "Two billion dollars a year is spent lighting up the sky," she said.
The impact of this light when and where no light should be on living things, people included, is not fully understood. "Life evolved with a period of darkness and a period of light," Thevenin said, and disruption of that cycle might have profound effects. She noted that hormone levels shift in response to light and to darkness, and that the immune system "gets a boost" when we are exposed to the dark.
Outdoor lighting can be better managed by using properly shaded and directed lights and lower wattage bulbs. The human eye naturally adjusts to lower levels of illumination, she said, but people can't see well at all in an environment that contains both bright spots of light and areas of shadow.
The glaring lights and deep shadows created by poorly designed lighting create havens for the criminals they are supposed to discourage, Thevenin said. The mugger crouching behind the bush "can see us just fine" but the glare of the mercury vapor street light utterly conceals him from his intended victim.
Astronomers, who found more and more of the stars in the night sky obliterated by the glow of man-made lighting, first began seriously raising the issue about 15 years ago, she said. Since then it has grown to be a global concern. Several states have taken action to require new outdoor lighting to be shaded and directed to minimize "light leakage" into the night sky and onto areas where lighting is not required.
"It's unnatural that we have light at night," she said, "except for moonlight."
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