By GALEN GISLER
Los Alamos

An editorial in the Jan. 24, 2022 issue of the Santa Fe New Mexican, “Dark skies are another draw for New Mexico” points out that the dark skies we enjoy here are a benefit to tourism as well as to the well-being of wildlife, human health, and calming the soul. Seven International Dark Sky Parks are in our state, the newest being the Valles Caldera National Preserve, which achieved that prestigious status in 2021.

Unfortunately, most people in the world do not enjoy dark night-time skies and can see at most a handful of stars on a moonless night. With advances in lighting technology, the problem of light pollution is constantly getting worse. Modern LED lamps use much less energy and are much less expensive to operate than older technologies such as incandescent, mercury vapor, or high-pressure sodium lamps. Municipalities and businesses therefore have an incentive to use more light than is needed.

Light pollution is light that is wasted or ill-used. Lights that are too bright produce dark shadows that can hide hazards. Lights that shine directly in our eyes cause glare that blind us and distract us from things we need to pay attention to. Badly positioned or poorly shielded lights shine into our bedrooms and disturb our sleep. Walk around Los Alamos or White Rock at night, and you will see examples of all of the above, on streetlights, on private residences, and in parking lots that are very brightly lit even long after activity ceases. Your walk will also show you numerous examples of good lighting, where doorways, sidewalks, and roads are illuminated and distinguished by diffuse, non-glaring lights.

We have an opportunity here in Los Alamos to take action as a community that will help to preserve and improve the dark skies that we presently enjoy. On the same day the above Santa Fe New Mexican editorial appeared, Dekker/Perich/Sabatini (DPS) and the Los Alamos Community Development Department (CDD) released a draft of Module 2 of an update to the Los Alamos Development Code (Chapter 16 in the County Charter). This document is now up for public comment (see https://losalamosconnect.org) until March 15, with a public open house Zoom meeting scheduled for 5:30 p.m. Feb. 15. The entire document is 172 pages long, of which half a dozen pages are devoted to lighting.

DPS and the CDD have done a commendable job in drafting a lighting ordinance that modernizes and improves the ordinance contained in Chapter 16-276 of the the present County Charter. There are a few points that can be improved still further.

The vast majority of streetlights in Los Alamos are of the high-pressure sodium type, which shine with a warm orange glow, and provide adequate light to guide traffic and protect pedestrians (and the deer that frequent our neighborhoods). Lighting professionals describe the color of lights with a number called correlated color temperature (CCT) or simply color temperature. The color temperature of the warm street lights we are comfortable and familiar with is about 2200 K. There are LED streetlights available with color temperatures of 2200 K and below, but most common LEDs on the market have color temperatures much higher, 3000 K up to 5000 K. These higher CCT lights shine with greater blue content and appear much whiter to our eyes.

It is paradoxical, but true, that lights that appear “cooler” have higher color temperatures. At the same luminosity, high CCT lamps seem brighter because our eyes are more sensitive to blue light than to red. But our heightened sensitivity to blue means that when we look away from those bright lights into the shadows we lose our adaptation to darkness and may miss seeing a hazard. The blue content of high CCT lamps is also reflected off pavements and scattered off dust and droplets in the air more efficiently, and contributes to glare, light trespass, and skyglow, even when the lamps themselves are fully shielded. Examples of such high-CCT LED lamps can be seen in the parking lots of businesses. schools, and churches around town, and (notoriously!) on the approach to the roundabout where NM 502 enters Los Alamos.

The Outdoor Lighting Section (16-4-6) of the DPS Module 2 draft recommends. in several places, an upper limit CCT of 3000 K for outdoor lighting. This is too high. A study performed by the National Park Service (L-W Hung et al. 2021, Journal of Environmental Management, 292, 112776.) found that “one-for-one HPS to 3000 K LED replacements are likely to increase light pollution”. This study was done of Chelan County in Washington State, which conducted such a replacement and indeed found its skyglow to increase as a result. Like Los Alamos, Chelan County is a neighbor to units of the National Park Service.

We need to make sure Los Alamos County does not repeat Chelan County’s mistake. Our neighbors at Valles Caldera National Preserve and Bandelier National Monument would not forgive us if we do. Let’s make the upper limit CCT the same as our existing HPS streetlights, 2200 K. Alternatively, or in addition, let’s include a clause that eliminates the emission of blue light with wavelength shorter than 500 nm.