New dimmable LED lights are seen in mid brightness in Pittsburgh, Pennsylvania. After passing a dark-sky ordinance to curb light pollution and save energy, Pittsburgh is installing adjustable streetlights. Photo / Danielle Amy, the New York Times
One recent night in July, Denny Robinson, a project manager for the city of Pittsburgh, stood on a street corner on the North Side, lit up by newly installed streetlights, fiddling with his phone.
“Let’s dim it down to 24%,” Robinson said, sliding his thumb across the phone’s screen.
Four nearby streetlights softened to a gentle glow, eliciting oohs and aahs from a small group of onlookers gathered to behold the wonders of municipal mood lighting.
Pittsburgh in the United States is replacing most of its streetlights — more than 33,000 inefficient high-pressure sodium lamps — with LED versions that are projected to save about US$942,000 a year in energy costs while tackling light pollution.
The old lights cast an orange glow that bathed the heavens and anything nearby in what Flore Marion, the city’s assistant director of sustainability and resilience, described as “horror movie” lighting.
The new lights are directed downward and emit warmer light than many LEDs.
Compared with the old orange lights, the new lights appear brighter when fully turned up, but shields can be added to the fixtures to curb what is known as “light trespass”.
Robinson said he also plans to dim the new lights between 11pm and 4am, which will save energy and money, and, according to the city, cause less harm to migratory birds, urban wildlife, and humans.
Thanks to urbanisation and electrification, light pollution is growing globally by nearly 10% a year, according to a 2023 study.
Many areas are over-lit, which wastes energy, obfuscates starry skies and messes with the circadian rhythms of plants, wildlife, and people.
Pittsburgh officials had long planned to swap out the city’s old streetlights, but for years they didn’t have the budget to adopt the types of LED streetlights that other cities were beginning to install.
That turned out to be a good thing. The first generation of LED streetlights led to lower costs and energy savings but also heightened exposure to glare and harmful blue light.
In 2016, the American Medical Association warned that blue-rich LED streetlights suppressed melatonin and contributed to sleeplessness, poor daytime functioning and obesity, while also disorienting birds, insects, turtles and fish species that need darkness at night.
Some research suggests that bright city lights worsen air pollution by hindering night-time chemical reactions that clean the air.
The city of Pittsburgh included new streetlights in its 2021 budget and not long afterwards passed an ordinance that follows guidelines from DarkSky International, a non-profit organisation focused on fighting light pollution.
One feature of the new lights that complies with DarkSky International’s recommendations is a relatively warmer hue.
Night-time LED lighting around warehouses and in prison yards often emits bright, cold blue-rich light that can have a colour temperature of 5500 kelvins and up.
DarkSky International recommends streetlights with warmer tones and a maximum colour temperature of 3000 kelvins. Pittsburgh’s new lights are 2700 on the Kelvin scale.
“We leapfrogged the LED blue-light phase,” Marion said.
According to the city, the new lights will last at least four times longer than the ones they’re replacing, saving the city nearly US$500,000 in maintenance costs annually.
Because it’s using less electricity to run the lights, the city estimates it will prevent 12,000 tonnes of carbon dioxide emissions each year.
“It’s practical and pragmatic because of its simplicity and its impact,” said Grant Ervin, Pittsburgh’s former chief resilience officer.
One of the biggest proponents of Pittsburgh’s dark-sky lighting ordinance is Diane Turnshek, who teaches astronomy at Carnegie Mellon University and the University of Pittsburgh.
Turnshek, 70, who grew up in New England, remembers easily seeing the Milky Way as a child.
Over time, she grew dismayed by the fact that her astronomy students couldn’t readily see dazzling starry skies and that light pollution often wasn’t considered an environmental concern.
She was determined to raise awareness about the problem and ways to address it and worked with the city of Pittsburgh to pass the ordinance.
“It’s such an easy fix,” Turnshek said. “You turn them off. You use them appropriately. You don’t use them when you don’t need them. Change is instantaneous and saves you money.”
The prospect of dimmer streetlights is often met with public resistance because of the belief that artificial lights increase night-time safety.
While people may feel safer with more light at night, that doesn’t necessarily correlate with crime statistics, said John Barentine, a consultant and former director of public policy for DarkSky International.
US cities and towns often vastly exceed recommended levels of illumination, creating glare that can be blinding, he said.
Lower-income neighbourhoods with more people of colour often had brighter lights than more affluent, white neighbourhoods, he said.
“We’re arguing in favour of public safety by preserving and enhancing night-time visibility through better lighting design,” Barentine said.
“We’re actually doing people a favour by bringing the light levels down, because we’re helping the eye to operate most efficiently under night-time conditions. We’re aiding vision, rather than taking something away.”
Still, there are limits to the benefits.
Avalon Owens, a research fellow at the Rowland Institute at Harvard University, said that even warm, dim artificial light is usually too bright for most nocturnal insects, which have eyes that are thousands of times more sensitive than those of humans and are most active a few hours after dusk. Motion-activated lighting is also preferable, she said.
But shielding lights from natural areas does reduce some negative impacts on insects and the species that rely on them, Owens said. LEDs also use less power, generating fewer greenhouse-gas emissions, and climate change is one of the biggest threats to biodiversity.
“It’s a matter of minimising harm,” Owens said.
Pittsburgh also has about 3450 LED streetlights with colour temperatures of 4000 kelvins that will be swapped out for the new, warmer versions. The US$15 million project is expected to be completed in 2027.
This article originally appeared in The New York Times.
Written by: Cara Buckley
Photographs by: Danielle Amy
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