What is light pollution? Light pollution is excessive light that shines where it is not wanted or needed.
It is kind of like grass. In your yard, grass is good. Grass prevents erosion and makes a soft, safe place for kids to run and play. However, anyone with flower beds could tell you that grass is not wanted or needed in the mulched beds next to peonies. There, grass is a weed. The same is true with light.
In the right place and used the right way, lighting is an important component of safely enjoying your property at night. But excessive light shining into the sky, shining into bedroom windows or shining into your eyes, making you wince from the glare, becomes light pollution.
Light pollution, also known as Artificial Light at Night (ALAN), is a growing concern and has been the subject of increasing research since the first world atlas of night sky brightness was published in 2001. Between 2000 and 2005 there were about 30 studies a year. This number has increased dramatically with more than 450 studies in 2021 alone. These studies demonstrate that ALAN has negative effects on plants, animals and people. All this excessive lighting is wasting energy to the tune of three billion dollars a year.
You can most clearly “see” light pollution when you try to see stars from your backyard. In the United States 99% of the public has skies that are polluted to the point that people can’t see the Milky Way.
This may sound like just another sad tale; however, light pollution is the only pollution that is instantly reversible. For example, when there is a widespread power outage, light pollution disappears. Unfortunately, for most of us it is a little more complicated than that. To fight pollution, you don’t have to get rid of all your lights. Lights are important for safety reasons, revealing trip hazards or accessing door locks. The best way you can fight light pollution is to FOCUS the light where you need it, when you need it.
Focus your lighting. Make sure the light is targeted, directed and focused on where it needs to be, on the ground or on your doorknob for example. Full cutoff fixtures help here.
Only as bright as it needs to be and not excessively bright to cause glare or trespass. Learn what a lumen is and try to keep it under 1500 lumens.
Control the lights so that they are not on all the time wasting energy, but only on when they are needed. For example, turn them off when you go to bed or use timers or motion sensors.
Use only lights that have a clear purpose.
Soft white light (low color temperature >3000k) is best for human eyes because bright white light can be jarring and have negative effects on sleep.
These five concepts are reflected in the outdoor lighting standards for Fairfax County. When considering new lights make sure you educate yourself on the outdoor lighting standards for where you live. When it comes time to replace your outdoor fixture it’s important to be able to recognize good dark sky compliant lights. The lighting standards require full cutoff fixtures, which means the light in these fixtures only shines down where it is needed, reducing glare. One way to make sure you get a compliant light is to make sure the bulb is not showing. Visible bulbs cause glare and harsh shadows which are unsafe.
The recent lighting upgrade below is an example of the little changes we can all do to make a difference. The original light on the left is a glare-causing light fixture which can be found on many Fairfax County homes. The light shines out to the side and upward where it is wasted. The fixture on the right is a new, improved, code compliant light that shines downward where it is needed. It illuminates the ground where people walk, helping to prevent tripping hazards, and, in this case, it shines onto the house number so people can see it.
This is just one example where focused lighting can be an upgrade that is easy to achieve and gives you good vibes for helping the environment. If enough of us do it, we may again be able to see the Milky Way from our own yards. This 2020 study from NASA showed that street lights in Tucson were only 13 to 18% of the light from the city. That means most of the light is coming from other sources. This is why the collective action of citizens and business owners can make a real difference. Walk around your property and see if you can FOCUS the lighting you have and make a difference in the levels of light pollution near your home.
More information about the Dark Sky movement in Fairfax County can be found on the Park Authority Dark Skies topic page.