24 June 2016

Sky survey, AMA recommendations say it's time to reduce light pollution

A major focus of the International Year of Light and Light-Based Technologies was raising awareness of light pollution. With the rapid dissemination of LED lighting, one unfortunate side-effect is the proliferation of a higher color-temperature illumination. This has many documented negative effects on wildlife behavior and migration, as well as on human circadian rhythms. In addition, scientists are studying further problems in human health that may be indirectly related to different lighting, including higher incidence of some cancers.

Meanwhile, cities and towns across the globe enthusiastically switch to LED street lighting. The energy savings are significant, but in news reports of the plans and projects, there is usually no mention of the technical specifics (or “warmth”) of the light. Early bright white LED streetlights were mostly above 4000K, whereas warmer versions are now available, 3000K or below.

One problem with extremely bright light is that it impairs vision in darker areas, so any illusion of safety at night vanishes as visibility diminishes once you get into a shadow. For drivers as well as pedestrians, this can be dangerous.

Now the American Medical Association (AMA) has issued guidance encouraging communities to adopt LED lighting that minimizes blue-rich light. The AMA also recommended that “all LED lighting should be properly shielded to minimize glare and detrimental human health and environmental effects, and consideration should be given to utilize the ability of LED lighting to be dimmed for off-peak time periods,” according to a press release.

“The guidance adopted by grassroots physicians who comprise the AMA's policy-making body strengthens the AMA's policy stand against light pollution and encourages public awareness of the adverse health and environmental effects of pervasive nighttime lighting,” the release says.

We requested a copy of the original report that led to these recommendations from the AMA. Here’s an excerpt:

More recently engineered LED lighting is now available at 3000K or lower. At 3000K, the human eye still perceives the light as “white,” but it is slightly warmer in tone, and has about 21% of its emission in the blue-appearing part of the spectrum. This emission is still very blue for the nighttime environment, but is a significant improvement over the 4000K lighting because it reduces discomfort and disability glare. Because of different coatings, the energy efficiency of 3000K lighting is only 3% less than 4000K, but the light is more pleasing to humans and has less of an impact on wildlife.

“Disability glare” is defined by the Lighting Research Center at Rensselaer Polytechnic Institute as “the reduction in visibility caused by intense light sources in the field of view [because of] stray light being scattered within the eye.”

One city that put the brakes on the brighter LEDs is Davis, California. In 2014, as new lights were being installed, the Davis city council put the project on hold after multiple complaints from residents. Later, the city decided to spend an additional $325,000 to replace those too-bright streetlights in residential areas. However, Davis is the exception. Places that have not yet committed to the switch are encouraged by the International Dark-Sky Association (IDA), the Lighting Research Center, and others to ask the right questions and study the issues involved beyond the simple let’s-save-energy approach. (In fact, that justification is up for debate as well -– it seems that when something gets cheaper, people tend to use more of it.)

Last fall, SPIE Newsroom published an article exploring these issues and collecting the advice of lighting experts. Recommendations for municipalities considering a change are included. (See “LED light pollution: Can we save energy and save the night?” by Mark Crawford.)

Just this month, a world atlas of artificial sky luminance, described in Science Advances reported that 80% of North Americans and one third of all humans are unable to see the Milky Way because of light pollution. Calculated with data from professional researchers and citizen scientists, the atlas also takes advantage of the newly available, low-light imaging data from the VIIRS DNB sensor on the Suomi National Polar-orbiting Partnership (NPP) satellite. The authors conclude:

"Light pollution needs to be addressed immediately because, even though it can be instantly mitigated (by turning off lights), its consequences cannot (for example, loss of biodiversity and culture)."

The IDA says this is a "watershed moment." The sky atlas and the AMA recommendations offer "an unprecedented opportunity to implore cities to transition to LEDs in the most environmentally responsible way possible." It's a good chance to start a conversation with your elected officials.

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