According to Energy.gov:
The potential effects of LED street lighting on health and the environment have been a hot topic of discussion over the last year. As this conversation has evolved, so too have many misperceptions and mischaracterizations of the facts on LEDs. We’ve assembled an array of helpful resources on the topic to help shed some light and are clarify some of the most common myths on LED streetlights.
Myth: LED streetlights are more harmful to humans and animals than other kinds of streetlights.
LED streetlights are no more harmful to humans and animals than other kinds of streetlights. The concern is not the type of light source, but the amount of emitted light that falls in the short-wavelength, often referred to as the “blue” part of the spectrum. And, unlike other types of streetlights, LED streetlights actually offer the potential to control the amount of short-wavelength light that they emit.
Myth: All short-wavelength light is harmful to humans and animals.
On the contrary, short-wavelength light is a fundamental component of the natural world. It’s present in sunlight and has been shown to play an important role in a number of physiological processes, such as affecting circadian rhythm (our 24-hour “biological clock” that controls sleep/wake cycles). The concern is that too much nighttime exposure to short-wavelength light may disrupt sleep patterns and have other undesirable effects.
Myth: LED lighting emits more short-wavelength light than do other lighting technologies.
It’s true that early LED lighting products tended to have greater levels of short-wavelength content because the technology was still in its initial stages of development. Tremendous advances since then, however, mean that today’s LEDs can be designed to emit as little, or as much, short-wavelength light as desired, without excessive drop-off in efficiency or other aspects of performance. LEDs also offer much greater control over where the light falls. This means they can often meet the same illumination requirements as conventional streetlights while emitting much less light – thus reducing even further any short-wavelength content.
Myth: Street lighting should never emit any short-wavelength light.
Most street lighting situations benefit from having at least some amount of short-wavelength content. Short wavelengths are a key component of the visible light spectrum, with benefits ranging from aesthetics to safety. White light sources that contain short wavelengths, for example, can show the colors of objects more naturally, aid in identification of people and objects, improve the contrast between an object and its background, and enhance peripheral vision at the low levels of illuminance that typically characterize street lighting.
Myth: Communities are better off with conventional street lighting.
For the last several decades, most street lighting in the United States has used high-pressure sodium (HPS) technology, which emits orange-yellowish light. HPS street lighting is being replaced by street lighting technologies that emit “white” light – primarily LED, due to its higher efficiency and longer life. All white-light technologies – including LED – emit more short-wavelength light than HPS. In addition to lasting longer and being more efficient – which by the way provide substantial energy and cost savings – LED street lighting also offers other potential benefits. For example, unlike other types of street lighting, LED systems can be adjusted to provide only the level of illumination needed at any given time, and can also offer a high degree of control over the direction in which light is emitted. This makes it much easier to reduce glare, light trespass (the spillover of light into areas where it’s not wanted), and uplight (which contributes to the phenomenon of “sky glow” that reduces visibility of stars in the night sky).
LED street lighting can play a critical role in avoiding unintended consequences to humans and wildlife – as long as care is taken to make sure the light is directed only where it is needed, with minimal glare, and that it emits a spectrum that supports visibility, safety, and health.
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