22 March 2017

AAS Council Issues New Resolution on Light Pollution

James Lowenthal Smith College

At its January 2017 meeting, the AAS Council unanimously passed a new resolution endorsing recent reports on light pollution and calling on all AAS members to advocate for dark skies in their own communities. The resolution was drafted by the AAS Committee on Light Pollution, Radio Interference, and Space Debris, which also hosted a special session on community solutions to light pollution at the Grapevine meeting.

The bad news is that light pollution is bad and getting worse worldwide, spurred on by a surge of cities aiming to save money and electricity by installing new energy-efficient LED streetlights. The problem is that not all LEDs are the same. Most first-generation white LED outdoor lights are very rich in blue light (which, as astronomers know well, scatters in the atmosphere much more than longer wavelengths), brighter than the old lights they replace, and poorly shielded against glare and light trespass. And there remain persistent myths and unfounded assumptions in state and local governments and the general public that more light is better, and that darkness is to be feared.

The good news is that LED technology is evolving rapidly for the better. While many new streetlights just a few years ago had very blue correlated color temperatures (CCT) of 4000K or even 5000K, now 3000K is common, and new products coming to market now have CCT of 2000K or even less. Even the best of these white LEDs create significantly more (2x-7x) sky glow than the high-pressure sodium (HPS) lights that have been common in US cities for decades. Fortunately, options to mitigate this are available: various types of filtered LEDs that remove emission entirely below 500-550 nm, phosphor-converted amber (PCA), and true narrow band amber (NBA). The PCA LEDs have a mellow amber color similar to HPS, while NBA is a reasonable spectral analog for the best dark-sky lighting of all, low-pressure sodium. The benefits: significantly less sky glow, as well as less glare, less impact on human health and wildlife, and a more pleasing appearance. Effective advocacy by the International Dark-Sky Association, the American Medical Association, the International Astronomical Union, and other organizations over the last decade has helped raise awareness of these issues in the face of perhaps the most rapid outdoor lighting transition in history.

The new AAS resolution on light pollution — the first since the AAS backed National Dark Sky Week in 2003 — endorses the IAU's 2009 resolution "In Defence of the Night Sky and the Right to Starlight," affirming that access to a dark night sky is a universal human right, as well as the AMA's report (May 2016) on "Human and Environmental Effects of Light Emitting Diode (LED) Community Lighting." The resolution also lists basic rules for good outdoor lighting (not too blue, not too bright, well shielded against glare, and on only when necessary) and calls on all AAS members to take local action in support of dark skies.

What local action? Here are some ideas:
  • If your city or town has not yet switched its streetlights to LEDs, quick! Contact your mayor, city councilor, planning office, and/or department of public works and make sure they know about the basic rules of good outdoor lighting (see above) before they make a mistake they'll be stuck with for 20 years. Emphasize the serious threats to human health that bad outdoor lighting poses: disruption of circadian rhythms, suppression of melatonin, and elevated rates of cancer, diabetes, and obesity. Give them the latest illustrated info brochures from the IDA.
  • Form an outdoor lighting advisory committee in your city or town. Include not just astronomers, but also experts in, or at least people concerned about, public health, public safety, wildlife, and energy savings.
  • Help draft an outdoor lighting ordinance that reflects current best practices, including proper treatment of LED lights. The IDA website has useful resources including a Model Lighting Ordinance — you don't have to start from scratch.
  • Get in touch with existing environmental organizations, such as local chapters of the Sierra Club, the Appalachian Mountain Club, The Nature Conservancy, etc., teach them about the importance of controlling light pollution for the health and welfare of wildlife, and enlist their aid in spreading the word.
  • Contact the environmental studies, geography, architecture, and/or urban planning departments on your (or on a nearby) campus and educate them about the far-reaching hazards of light pollution and the importance of good outdoor lighting.
  • Visit a local elementary, middle, or high school and teach kids about light pollution. The IDA and the Globe at Night citizen science program offer lots of good teaching resources.