In a quest to reduce energy use, many communities across the country are swapping out high-pressure sodium streetlights for much more energy-efficient LED lights.
But some of the most commonly used LED lights, which tend toward the blue part of the spectrum but appear white to the human eye, could work against helpful intentions to light up the dark, according to a new report by the American Medical Association.
That's because LED lights that emit a large amount of blue light can disrupt circadian sleep rhythms in humans and animals, says the study, as Take Part reports.
The new lamps can have an impact that five times greater than traditional street lamps on circadian rhythms, the AMA says. In addition to increasing glare for nighttime drivers, "[r]ecent large surveys found that brighter residential nighttime lighting is associated with reduced sleep times, dissatisfaction with sleep quality, excessive sleepiness, impaired daytime functioning and obesity," the group says in a statement.
The lights can also have harmful effects on animals, research shows. Some migrating birds are attracted to the unnatural light sources, leading them to collide with buildings or reflective surfaces.
Baby sea turtles that rely on moonlight to guide them to the ocean after they hatch may instead be attracted to nearby artificial lights coming from sources such as strip malls, polluting the night sky, The Christian Science Monitor's Eva Botwin-Kowacki reported.
Those concerns have fueled efforts by researchers and advocates to encourage communities to adopt LED lights with lower color temperatures that don't emit as much blue light, and to use light that is shielded to minimize glare and impacts on local wildlife.
"We're not anti-LEDs at all," Cheryl Ann Bishop, communications and public affairs director for the International Dark-Sky Association (IDA) told the Monitor this month. "But we're really concerned about the retrofit that is going to the higher color temperatures."
"The standard right now seems to be 4000 Kelvin," she said, in the blue-heavy spectrum. "That's why IDA recommends 3000K and below."
The AMA notes that some National Parks in the United States have begun adopting guidelines to minimize the impact of light pollution on the environments of many animals that depend on the dark.
In addition to recommending communities use lights that emit less blue light, the doctors' group is also pushing for consideration of LED lights that can be dimmed during non-peak hours.
Beyond LEDs, the increasing variety of artificial light sources now means that more than 80 percent of the world's population experiences some level of light pollution, according to a recent paper published in the journal Science Advances, the Monitor reported.
These artificial sources, from streetlights to brightly lit billboards, have also come to block out some of the natural world's most wondrous sights, with one third of the world's population unable to see the Milky Way galaxy, the researchers found.
But researchers say the efforts of the AMA and other groups to raise awareness of the impacts of how we use artificial light can help change policies.
So far, only about 10 percent of roadway lighting has been converted to LEDs, while there are currently no national standards for highway lighting, TakePart reports.
"The great thing about this is there are ways we can do far better than we are doing right now," Travis Longcore, assistant professor of architecture and spatial sciences at the University of Southern California and science director at the Urban Wildlands Group, told the Monitor, "and not sacrifice any of the needs we have in terms of lighting at night for human safety and well-being."