Light pollution wreaks havoc on biological systems, altering the circadian rhythms which guide the 24-hour cycle of sleep for most life on Earth, and for as much as 80 percent of North America’s population, it hides what was once a constant in the night sky: the light of the Milky Way.

“Light pollution is a form of pollution that is a form of environmental destruction that is absolutely on par with air or water pollution,” said John Barentine, International Dark Sky Association program director.

Most life on Earth is dependent on sunlight, he said, and throughout Earth’s history, life forms evolved to respond to the natural periods of light and dark.
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“When we use electric light at night outdoors, we’re putting light into the environment during a period of time of day when our bodies don’t expect there to be any,” Barentine said.

Lights in Phoenix are in the process of changing to LEDs. A public comment period ended on June 30 that gave residents the chance to weigh in on whether a 4000 Kelvin bulb or a 3000 Kelvin bulb would illuminate better and be cost and energy effective. The respondents split almost down the middle.

Barentine said the International Dark Skies Association is not opposed to LED lighting.  He advised the city research the lighting options because some places have updated lights only to get complaints from residents about the lighting being too sterile or hospital-like. 

​"We're not necessarily going to come back to a point where you can see the Milky Way from downtown Phoenix," Barentine said. "But at the same time, I don't think the right thing to do is to simply accept that living in a heavily light-polluted environment...is a natural consequence of living in a city."