Q&A: New LED street lights may disrupt sleep, increase light pollution

Ottawa has converted 700 streetlights on Carling Avenue to LED (light-emitting diode) technology, changing the look of the street at night, dimming views of the stars and perhaps even disrupting your sleep.

We spoke to Robert Dick, University of Ottawa physicist and author of the protocol that governs lighting in Canada’s national parks. He’s a longtime advocate for darker skies

Q. Are Ottawa’s new LED streetlights going to cause more or less light pollution?

A. More, Dick says. He says the LED technology is a cold, harsh light with more glare than the previous technology, and the streetlights are now very bright. As well, “white is actually a very bad colour to use. The blue part, the short wavelength part of the spectrum (part of white light) scatters a lot more,” which makes light go where it’s not wanted — up.

Q. But the sky looks darker with LED lights. Doesn’t that mean less light pollution?

A. “The reason why the sky looks darker is because of the glare from the (new LED) lights. In principle, they don’t allow any light upward. But those LEDs are intensely bright on your retina and your eye responds by closing down the iris and that makes the sky look dark. It looks as though you have a nice dark sky but you’ll also (realize) you don’t see any stars. That’s because your eye isn’t as sensitive” with a smaller pupil.

Q. Does this matter to my everyday life?

A. Yes. LED lights marketed today are a very white light. They contain more blue light than “softer” traditional lights. “The white light, or the blue part of it, affects your circadian rhythm,” he says — the body’s cycle of being awake and sleeping. Scientists at a symposium on sleep disorders at the Royal Ottawa Mental Health Centre in 2012 described how blue-white light (also found in computers and cellphones) tricks the brain into thinking it’s daytime, and interferes with the ability to sleep. The warmer colours we see in candles and firelight don’t cause this reaction.
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Q. What lighting technology do you like?

A. The old streetlights were high-pressure sodium, “and very good ones, but they were getting old.” He argues new sodium lights are kind to the eyes and are now competitive with LED in energy use. “They produce the same amount of light per watt.”

He says LED lights can also use a light that’s more amber than white, but it’s not sold commercially.

Q. What does city hall say?

A. It strongly disputes Dick’s views. A memo calls them “dark skies friendly” because they have less “trespass” light — light that escapes sideways or upward. It also says the LED lights will save as much as $5.3 million a year million in energy and maintenance.

There’s a tentative plan to convert 67,000 streetlights to LED in years to come. The next council would have to approve it.