20 Nov 2014

LEDs and light pollution

Iris G writes:*

As the world demand for energy grows, research into more efficient and sustainable ways of using energy is booming. This is especially noticeably in the field of lighting, which is experiencing nothing short of a revolution. Just last month, it was announced that this years Nobel Prize in Physics has been awarded to three scientists for their work on light-emitting diodes, commonly known as LEDs. In the past decades industrial and domestic lighting transitioned from the traditional incandescent bulbs to CFLs and now moved on to LEDs, which are used for a variety of applications ranging from domestic lighting to cellphone screens to Christmas lights.

The improvement in energy-saving is significant: LEDs are much more efficient at generating visible light compared to an incandescent light bulb, their lifespan is over 40 years longer than that of a traditional bulb, and due to recent improvements in lighting technology LEDs have also become much cheaper. Many types of LEDs, however, also have one major downside: they can contribute severely to light pollution.

The phenomenon of light pollution has been recognized for some time and appears to be an almost inevitable consequence of development. It is virtually omnipresent in the urban areas of the United States and Western Europe, where it is estimated that around two-thirds of the population can no longer view the Milky Way with the naked eye [1]. In recent years it has become increasingly clear that light pollution can be very detrimental to the environment and human health, and many of its effects are not yet well understood. High levels of pollution are linked to weight and mood problems as well as breast cancer in humans, and generally impact the biorhythm and behavior of wildlife, especially nocturnal animals [2].

Although any light above pollution thresholds can have an effect on health and nature, the blue-white light (wavelengths below 500nm) emitted by LEDs may be especially detrimental. This type of lighting could cause two to five times as much light pollution if it replaced all of the current lighting, due to the greater scattering of blue light compared to green or red light (this is also why the sky is blue and no other color)[3]. Warmer hues of LEDs are being developed, but are currently not as effective and competitive as their blue light counterparts.

This is not to say that LEDs should not be used and celebrated - on the contrary. Rather, it should be recognized that while they are a major breakthrough in lighting, LEDs form only part of the solution to more efficient and sustainable lighting. Businesses and industries should still look critically at their use of lighting even when they implement LEDs, and shield their light emissions where possible. In urban areas, local municipalities should carefully consider where and in which way LEDs can be used efficiently without exposing citizens to detrimental effects from light pollution. Individuals could cut down significantly on their energy use by transitioning to LEDs in their home. Finally, it is important to remember that even when lighting becomes cheaper, it can't hurt to turn the light off every now and then.

Bottom line: LEDs are a great new money- and energy saving source of lighting, but we have to be careful about when and where to implement them as they are not without downsides.

* Please comment on these posts from my environmental economics students, to help them with unclear analysis, other perspectives, data sources, etc.

  1. Pierantonio Cinzano, Fabio Falchi, Christopher D. Elvidge. 2001 Monthly Notices of the Royal Astron. Society 328, 689–707
  2. Ron Chepesiuk. 2009. “Missing the Dark: Health Effects of Light Pollution.” Environmental Health Perspectives 117:1: A20-A27. Accessed at: http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2627884/
  3. Fabio Falchi, Pierantonio Cinzano, Christopher D. Elvidge, David M. Keith, and Abraham Haim. 2011. “Limiting the impact of light pollution on human health, environment and stellar visibility.” Journal of Environmental Management 92: 2714-2722. doi:10.1016/j.jenvman.2011.06.029