Everyone loves how the city's plans to begin installing LED streetlamps across Seattle would save energy. But a near-universal sentiment of people living in the seven areas where the city is testing the LEDs is that the lights are unsettling; unlike the orange-ish color of the existing lights, the LEDs cast blue-green beams and make neighborhoods look like sets of zombie movies. As I note in this week's paper, the issue isn't purely aesthetic:

According to Dr. David Avery—a professor of behavioral sciences and light therapy at the University of Washington and the region's leading researcher on the impact of light on human chemistry—the LED lights could interfere with human biorhythms. Certain photoreceptors in the eye's retina react to cooler colors of the light spectrum, sending a signal to the brain that the sun is up. When humans see the blue light, our bodies think it's daytime. "The sensitivity to these cells for the blue and greenish color makes perfect sense, because the sky is blue. So for millions of years, life has evolved with this 24-hour rhythm of blue light being very prominent for part of the day and then darkness," he says. "This is kind of a conductor of a circadian symphony in the brain and body."

According to Avery, "Theoretically, if someone has one of these LEDs or a blue light outside their window, it could fool the eyes and the brain into thinking that the sun is still up, so the melatonin hormone might not rise normally and sleep might be disrupted."

The full article is here.