Light-emitting diode streetlights are a favorite of the eco-conscious, the frugal and many a municipal official. That's because LEDs — compared to traditional high-pressure sodium and metal-halide lamps — last much longer, which means fewer bulbs to buy and lower labor costs to change them. They use about 50 percent less energy, which saves money and power-plant emissions.
Those savings can add up. NYC's Department of Transportation told the Wall Street Journal that switching over to LED bulbs could save the city $6 million a year on energy and $8 million on maintenance. So you can see why many cities, including Seattle, New York and Los Angeles, have been switching over to the new bulbs in recent years. LEDs now make up about 13 percent of public lights in the United States, according to U.S. Energy Department figures.
But LED lights are also known for having an ugly bluish, overly bright light. "A strip mall in outer space is the metaphor I've been using," one Brooklyn resident tells CBS News in the video below, showing a reporter just how bright her room is during the night:
Bright is in the eye of the beholder
Not everyone is equally affected by bright lights. While some people found the LED lights too bright, others liked a daylight atmosphere at night, while others didn't notice. But the brightness isn't just an aesthetic concern; poorly designed streetlights can mess with some people's ability to sleep because they may depress melatonin, the natural hormone produced in our bodies that encourages sleep. That's one of the reasons the American Medical Association has released a report that's critical of LED, mentioning the glare factor and the health effect of too-bright lights on circadian rhythms.
"Improper design of the lighting fixture can result in glare, creating a road hazard condition," the report details. "Many early designs of white LED lighting generated a color spectrum with excessive blue wavelength. This feature further contributes to disability glare, i.e. visual impairment due to stray light, as blue wavelengths are associated with more scattering in the human eye, and sufficiently intense blue spectrum damages retinas. The excessive blue spectrum also is environmentally disruptive for many nocturnal species."
That disruption — for any creature — is again driven by color. According to the report, a white LED lamp is "at least five times more powerful in influencing circadian physiology than a high pressure sodium light based on melatonin suppression." For animals, the color and brightness of outdoor lights are similarly meaningful, affecting how birds migrate, if lightning bugs procreate and determining the success rate of turtle hatchlings trying to make their way to the sea.
The changes in circadian rhythms due to LED's blue hues may also affect people's hormone levels. A 2018 study shows that people who live in areas with LED streetlights have an increased risk of developing prostate or breast cancer — both of which are hormone related cancers. The study followed more than 4,000 people in Spain and established a link between high levels of exposure to LEDs and double the risk of developing prostate cancer and 1.5 times higher risk for breast cancer.
Despite the increasing risks, there are ways to mitigate most, if not all of the negative effects of the LED lights while keeping the benefits. Yellower LED bulbs can mellow the intensity of the blue light, and lower intensity lights can help make a neighborhood feel less like a stadium lit up at night — while still making the streets feel safe. Shields on the sides of the lights can help too, so light is directed down onto the ground rather than all around, including through people's windows.
As more cities roll out LEDs along their streets, they can learn from the mistakes of early adopters, getting the economic benefits of LED minus the sleepless nights.
Editor's note: This article has been updated since it was originally published in October 2016.