Replacing sodium light fixtures with LED streetlights (light-emitting diodes) in the streets of Montreal has had a positive effect on reducing light pollution in the city’s residential sectors, noted a researcher from the Planétarium Rio Tinto Alcan. However, he is concerned about the ever-increasing intensity of industrial or commercial lighting, which could destroy the City’s efforts.
To measure the effect on light pollution of the new LED streetlights, which the City of Montreal began deploying in 2017, Jonathan Gagné, scientific advisor at the Planétarium Rio Tinto Alcan, examined the images provided by a camera installed on board the satellite Suomi NPP between 2012 and 2020 — when 68% of new streetlights were installed.
The researcher also studied photos taken in February 2021 from the International Space Station. One of the photos shows the Saint-Sulpice district, where the LED streetlights were installed, and the neighboring area, André-Grasset, where the old lights are still in place. From the sky, the LED-lit district appears darker than the neighboring orange-hued district, a sign that the light pollution there is less intense.
Elsewhere, however, the photos show strong concentrations of bluish light, notably in the Anjou industrial park and in downtown Montreal, testifying to high color temperature LED lighting.
For the purposes of his study, however, Jonathan Gagné focused his observations on the sectors where the LED streetlights were installed by the City in order to see if the effect was noticeable. But he had to do a lot of calculations, because the satellite camera barely perceives the blue light contained in the LEDs, whereas the human eye is much more sensitive to it. Other elements had to be considered, such as seasonal variations and atmospheric diffusion.
Catastrophe averted
However, Jonathan Gagné has come to the conclusion that, until now, LED streetlights have reduced the light pollution perceived by the human eye in total darkness by about 5%. This reduction could exceed 10% when the installation of the new streetlights is completed. In his study, the researcher even mentions a reduction of up to 29% once all the streetlights are installed, but in the interview, he remains cautious. Not only are other light sources plentiful, but forecasts can vary depending on brighter or darker ambient light conditions.
The researcher insists: certain conditions are essential in the installation of LED streetlights to limit light pollution.
“In the transition to LEDs, Montreal avoided disaster by making the right decisions,” he says. When it launched the project in 2014, the City opted for 4000 Kelvin (K) LED luminaires, before finally choosing 3000 K luminaires, which are less dazzling. “It would have been much more dramatic if we had used 4000 Kelvin,” he says. “Between 3000 K and 4000 K, there is a big difference. »
The City has also taken care to use streetlights that direct the light towards the ground. She also reduced the intensity of the lighting to 30% below the established standard. This decision was made by a city engineer who realized that at the same intensity, LEDs offered better visibility than sodium lamps. “If he hadn’t done that, the situation would have gotten worse,” explains Jonathan Gagné. “It’s really a happy coincidence that he realized that. »
According to Jonathan Gagné, it is essential for cities to respect these three “crucial” conditions by converting to LED streetlights, otherwise light pollution could double or even triple.
Fears of setbacks
Less energy intensive than sodium fixtures, LEDs have a bluish light and are suspected of disrupting the sleep cycle, which can affect health.
Jonathan Gagné fears, however, that light pollution will worsen in Montreal despite the advances made possible by the new LED lighting due to the lack of regulations to regulate lighting from industrial or commercial sources. “When you look at pictures taken from the International Space Station in 2013, you see a lot of very bright white dots that weren’t there in 2008. These are businesses, probably car dealerships, factories, highways” , he explains. “And in 2021, it’s even worse: we see an extreme multiplication of fluorescent blue dots. Meanwhile, residential neighborhoods are improving. »
No lighting regulations apply throughout Montreal and on Thursday, the City was unable to specify whether rules applied in the boroughs.
As of December 2021, the City has installed 110,087 of the planned 132,000 LED streetlights.
Jonathan Gagné will present the results of his research on Friday evening during a virtual conference presented in collaboration with the Astronomical Society of the Planetarium of Montreal.