IDA wants blue light from streetlamps restricted

TUCSON, AZ--A group called the International Dark-Sky Association (IDA) has issued a statement noting that “the rapidly expanding use of bluish-white outdoor lighting threatens visibility at night and jeopardizes the nocturnal environment worldwide.

Nov 15th, 2009

TUCSON, AZ--A group called the International Dark-Sky Association (IDA) has issued a statement noting that “the rapidly expanding use of bluish-white outdoor lighting threatens visibility at night and jeopardizes the nocturnal environment worldwide.” The statement specifically refers to LED-based outdoor lighting, and also includes induction lamps (which are either plasma or fluorescent lamps that are excited via an outside electromagnetic field instead of conventional electrodes).

The IDA defines blue light as any light with a wavelength shorter than 500 nm, and says that lamps emitting blue light increase glare and compromise human vision, especially in the aging eye. “Short-wavelength light also increases sky glow disproportionately,” says IDA. “In addition, blue light has a greater tendency to affect living organisms through disruption of their biological processes that rely upon natural cycles of daylight and darkness, such as the circadian rhythm.” The IDA also says that the blue portion of the color spectrum produces only a small percentage of light that is useful to the human eye.

The blues

Reducing light pollution at night has many beneficial effects: increasing the beauty of the night sky, making life easier for astronomers and pilots, and the more efficient use of lamplight. This in general is accomplished by aiming as much light downward as possible, which minimizes the light projected upward. The IDA actively supports this approach.

However, the IDA is going further in wanting to also restrict the allowable range of wavelengths. Such restrictions, if followed, would greatly change the way the LED industry would need to approach outdoor lighting. Outdoor LED lamps are being eyed with great interest for three reasons: their high (and ever-increasing) efficiency; their extremely long life; and their potential to provide true white light.

While blue-restricted LED lamps would still have high efficiency and long life, they would lose the pure-white appearance that many people instinctively find appealing (the highest-efficiency existing streetlamps are already blue-restricted: partially, in the case of high-pressure sodium lamps, which appear pinkish yellow; and completely, in the case of low-pressure sodium lamps, which emit pure yellow light).

The utilitarian and pleasure-giving aspects of actions taken by humans often must be balanced against their long-term effects on the environments; the IDA’s very existence is based on this fact as applied to lighting. However, the effects of blue-containing outdoor lighting are not yet fully quantified. The IDA does encourage government and other concerned parties to support additional scientific research on this subject, to help understand the impact and guide the evolution of lighting technology.

The first “white” LEDs produced a harsh bluish-white light that many find unappealing; the LED industry is actively developing very efficient pure-white LEDs that most people intuitively prefer to existing streetlamps of any sort. And it should be kept in mind that moonlight, with its blue-containing white-light spectrum, has been a part of the Earth’s environment for longer than life has been in existence.

Perhaps well-designed downward-aiming LED outdoor lighting can reduce light pollution to an adequate degree. It is true that Rayleigh scattering in the atmosphere is far worse for blue than for yellow light, giving sodium lamps an advantage here; but on the other hand, LEDs allow much more focused designs that can virtually eliminate any upward-emitted light. It is clear that what’s needed is additional research into the effects of blue light, along with continuing LED lamp innovation and a dash of common sense.

--John Wallace

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