Using Light Smartly

Outdoor

Lighting Basics

We need outdoor lighting for a variety of activities, including safety and commerce. The Local Solar System Foundation recognizes this necessity but advocates that lighting be implemented wisely. To minimize the harmful effects of light pollution, lighting should:

Light only the area that needs it (such as within a pathway limit, or inside the parking and walking area of a parking lot)
Be no brighter than necessary (studies show that lower light levels are actually relaxing for humans)
Minimize blue light emissions (blue light has been proven to be damaging, especially at night)
Be fully shielded (i.e., pointing downward)

The inventory below provides an easy visual guide to understanding the differences between undesirable and unshielded light fixtures and those fully shielded fixtures that minimize skyglow, glare and light trespass.

Examples of Acceptable / Unacceptable Lighting Fixtures

Light Options

Most people are familiar with incandescent or fluorescent bulbs for indoor lighting, but outdoor lighting usually makes use of different, more industrial sources of light. Common light sources include high-pressure sodium (“HPS”), metal halide and light-emitting diodes (“LEDs”) and low-pressure sodium (“LPS”).

LPS is very energy-efficient but emits only a narrow spectrum of orange-colored light that some find to be undesirable. However, LPS is an excellent choice for lighting near astronomical observatories and in some environmentally sensitive areas, due to the use of the near-red spectrum.

HPS is commonly used for street lighting in many cities. Although it still emits an orange-colored light, its coloring is more similar to daylight than that of LPS.

In areas where it’s necessary to use white light, two common choices are metal halide and LEDs. One of the advantages of LED lighting is that it can be dimmed. Thus, instead of always lighting an empty street or parking lot at full brightness, LEDs can be turned down, or even off, when they aren’t needed, and then brought back to full brightness as necessary. This feature both saves on energy and reduces light pollution during the night.

Because of their cost and long life, LEDs are rapidly coming into widespread use, replacing the existing lighting in many cities. However, there are important issues to consider when making such a conversion.

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While it is crucial to have fully shielded lighting, the color of light is also very important. Both LED and metal halide fixtures contain large amounts of blue light in their spectrum. Because blue light brightens the night sky more than any other color of light, it’s important to minimize the amount emitted. Exposure to blue light at night has also been shown to harm humans and wildlife. The Local Solar System Foundation recommends using lighting that has a color temperature of no more than 3000 Kelvins.

Lighting with lower-color temperatures has less blue in its spectrum and is referred to as “warm.” Higher-color-temperature sources of light are rich in blue light. The Local Solar System Foundation recommends that only warm light sources be used for outdoor lighting. This includes LPS, HPS and low-color-temperature LEDs. In some areas, the white light of even a low-color-temperature LED can be a threat to the local nighttime environment. In those cases, LPS or narrow-spectrum LEDs are preferred choices.

The Importance of the Color Spectrum

Health Risks of Artificial Lighting

Mammals evolved to adapt to the cycles of the natural light-dark rotations of day and night. The spread of artificial lighting means that most of us no longer experience truly dark nights.

Research suggests that artificial light at night can negatively affect human health, increasing the risk of depression, sleep disorders, eating disorders and related sicknesses, such as diabetes, breast cancer and more.

Like most life on Earth, humans adhere to a circadian rhythm – in other words, our biological clock. This pattern is governed by the day-night cycle. Artificial light at night can disrupt that cycle.

Our bodies produce the hormone melatonin in response to our circadian rhythm. Melatonin helps keep us healthy. It has antioxidant properties and induces sleep, which boosts the immune system, lowers cholesterol, and helps the functioning of the thyroid, pancreas, ovaries, testes and adrenal glands. Nighttime exposure to artificial light suppresses melatonin production and is harmful to your health.

Blue Light

Exposure to blue light at night is particularly harmful. Unfortunately, most LEDs that are used commercially for lighting make use of abundant blue light. The same is true of most consumer electronics, such as computer monitors and screens, TVs, and other electronic devices.

To minimize harm from blue light in your home or office, choose the right light fixtures. The Local Solar System Foundation recommends downloading a color temperature measuring app that adapts your electronic screen to the time of day, with cool light during the day and warm light at night.

Choosing the Right Light Bulbs

In the picture, the bulb on the left is rich in high-color-temperature blue light, while the one on the right isn’t.

Use low-color-temperature light sources for interior and exterior light. Their light is less harsh and less harmful to human health and the environment. Look for warm white sources with a color temperature of 3000K or lower.

The Kelvin temperature chart below shows you what the numbers mean.

Higher color temperatures mean bluer light, which is the kind that you should avoid after dusk.

Glare Dangers

Studies show that glare at night increases stress and induces sleeping disorders. In addition, glare from poorly shielded lighting fixtures is harmful to your health because it decreases your vision, while reducing contrast. This limits your ability to see potential dangers at night. Aging eyes are especially affected.