When Thomas Edison invented the first successful lightbulb, could he have foreseen a world literally glowing in space? Maybe he did. One thing is certain, that vision is certainly a reality today. According to a global light pollution study by the Royal Astronomical Society
, "More than two thirds of the US population, about half the EU population and one fifth of the world's population live where they no longer have the possibility of seeing the Milky Way with the naked eye."
Much of the lighting stock polluting the night sky is now being replaced by light emitting diodes, or LEDs. In New York alone, over 250,000 streetlights will be replaced with LEDs by 2017. But are LEDs actually helping to ameliorate light pollution, or could their very efficiency and brightness be harming our health and the natural world even more than the lights they replace?
The Optical Society, a century-old professional association for advancements optics and photonics, highlighted the benefits of new LED street-lighting design in its recent report, "High-Performance LED Street Lighting Using Microlens Arrays." This new LED system has a high "optical utilization factor (OUF)… the number that describes the relationship between the flow rate of light at the target and the flow rate of light coming directly out of the LEDs." This means the average illumination at road level is uniform and high.
(Source: The Optical Society (www.osa.org))
The report claims that new LED streetlights will simultaneously reduce light pollution to 2% of traditional street lamp levels, because light is directed at the road and not leaked to the sky. Yet this does not convince critics. Bob King, a writer on astronomer at Universe Today, agrees that new LED installations have good shielding devices, so that "light spill and glare are relatively well-controlled," but also warns that "light reflected from the ground also goes up into space to light the sky."
Claims that LED streetlights reduce light pollution are also contested by other studies. Research published by the Journal of Environmental Management suggests that, when it comes to light pollution, the more environmentally friendly street lamps are "low pressure sodium, followed by high pressure sodium," while the most light-pollutant were "lamps with a strong blue emission, like Metal Halide and white LEDs." This implies that older lighting systems are actually more environmentally friendly than newer ones.
The research also suggests that LEDs in general are bad news for us urbanites, who need our sleep more than ever:
Migration from the now widely used sodium lamps to white lamps… would produce an increase of pollution in the scotopic and melatonin suppression bands of more than five times the present levels, supposing the same photopic installed flux.
In simple terms, the light sources that will cause the most light pollution (and harm to human health) are in fact LEDs, regardless of their efficiency. This is because the "blue-rich" color temperature disrupts our sleep by suppressing melatonin production, vital to health and mood.
Research by the Oregon Health and Science University reports that "low-dose melatonin taken in the afternoon helps most winter depressives whose physiological clocks are off kilter due to the later winter sunrise" -- thereby linking melatonin production to mental and physical health.
Richard Stevens, a professor and cancer epidemiologist at the University of Connecticut Health Center confirms this, stating that in artificially lit urban areas "there is much more opportunity for exposure of the retina to photons that might disrupt circadian rhythm." So it seems light, or the lack of it, is crucial to our health. Our exposure to "blue-rich" light from street level, our smart-phones, and other devices is not doing us any good as we prepare to sleep.
But it's not just humans that have been affected by our eternal daylight. A study by the British Trust for Ornithology found that "urban birds get up later than their country counterparts." The lack of light contrast between night and day could be effecting how birds respond to changes in natural light, which could in turn affect important mating and feeding rituals.
Last year, France's Environment Ministry enacted a pioneering lighting ordinance that aims to tackle light pollution and its effect on nature. "From 1:00 a.m. to 7:00 a.m., shop lights are being turned off, and lights inside office buildings must be extinguished within an hour of workers leaving the premises. The lighting on France's building facades cannot be turned on before sunset."
This saves money, reduces CO2 emissions, and enables wildlife (not to mention human beings) to function more naturally at night. It would seem that even with new LED street lights, and intelligent lighting design, there is no substitute for simply turning off lights when it comes to tackling light pollution.