Porch lights or streetlights in your area probably don’t come to mind when you think about pollution. But as the amount of artificial light increased over the years, its far-reaching effects became more evident. Around the world, both amateur and professional astronomers are shedding light on these implications, and some communities are taking action.
Since the ubiquitous use of light bulbs increased over a century ago, we are no longer guided solely by our planet’s built-in bedtime – a natural cue for our own circadian rhythms that also affects the way plants and animals live.
“Basically, we’ve changed that over the past 100 years because of the rapid and ever-increasing growth in artificial lighting at night,” said Ruskin Hartley, executive director of the International Dark Sky Association (IDA).
Light pollution has been on the rise for decades. In North America alone, from 1947 to 2000, light emissions grew by about 6 percent annually, according to a study published in 2003.
Animated by Megan McGrew / PBS NewsHour
Observed light emissions increased globally by at least 49 percent from 1992 to 2017, according to a study by the University of Exeter this year. He also stressed that due to measurement limitations, the actual increase is likely to be much higher, ranging from 270 to 400 percent depending on the region.
Light becomes pollution when it doesn’t serve a useful purpose, Hartley said, and that can waste energy, driving up the price and increasing the carbon footprint.
According to the IDA definition, light pollution can take several different forms. “Clutter” is an often misleading combination of many overly bright light sources such as Times Square or Las Vegas. “Dazzle” is when super-bright street lights or headlights bite your eyes or make you squint in discomfort. “Light intrusion” is when light shines where it shouldn’t, like a street lamp streaming through a bedroom window.
If you’ve ever bought blackout curtains to help you sleep better, you already know that excess lighting can have negative consequences for living things. People who are heavily exposed to artificial light during the dark may be more prone to insomnia. And artificial light can reflect plants and animals in a variety of ways, from disorienting birds and increasing the likelihood of their fatal collisions with buildings to massive declines in insect populations around the world.
In Pittsburgh, the city council recently passed the Dark Sky Ordinance after years of local propaganda that will pave the way for less wasteful, greener lighting for streetlights, parks, playgrounds, and city-wide buildings.
Astronomer Diane Ternschek of Carnegie Mellon University in Pittsburgh said it will be the first city to follow the latest IDA guidelines, but it is not the first city to tackle light pollution locally. Flagstaff, Arizona, was the first city to receive the International Dark Sky Place designation in 2001, but according to IDA it passed the street lighting ordinance back in 1958.
When Pittsburgh begins replacing its headlights early next year, it will replace new LED fixtures that emit softer, warmer light compared to the harder LED bulbs that are more commonly used today. The exchange will include some 40,000 existing light sources currently using either traditional LEDs or old high pressure sodium lamps, and the city also plans to add several thousand new street lights to improve lighting fairness – balanced distribution of artificial light – throughout the area. … town.
It remains to be seen whether these efforts will succeed in reducing light pollution in the city, but the switch to new lighting is expected to result in significant energy savings and long-term cost savings for Pittsburgh.
Grant Erwin, Chief Urban Resilience Officer, noted that many people in urban settings cannot see the stars where they live.
“Being able to see the night sky is pretty magical,” Erwin said. “And hopefully we are opening up this opportunity for Pittsburgh residents to take advantage of this advantage.”
Artificial light has changed a lot over the decades
The most efficient light bulbs on the market today are broad spectrum LEDs. They offer long-term economic and energy benefits – and require significantly less maintenance than other lamps – but they also pose several problems. First, the fact that they have a wide spectrum makes it much more difficult for amateurs and astronomers living in more urban areas like Pittsburgh to observe the night sky.
In the past, Turnschek said, conventional outdoor light sources, such as high-pressure sodium lamps, emitted a warmer amber light that covered a relatively smaller portion of the visible light spectrum. Astronomers could use a filter to block this light from their telescopes in order to see the sky correctly.
“V [visible] the spectrum ranges from the long waves, which are your reds, to the short ones, which are your shades of blue, ”said Stephen Quick, professor of architecture at Carnegie Mellon University. Both he and Ternschek helped develop the Pittsburgh Dark Sky Ordinance and spearheaded local efforts to raise awareness of light pollution.
“You can not [filter out] full spectrum light, because if you start filtering all colors, you have no light, ”Quick explained.
LEDs also emit more light in the shorter, bluer side of the visible spectrum than we get from our phones and laptops. This is why they tend to look cooler and sharper to our eyes when compared to other types of light. But newer bulbs may have coatings that filter out some of the light on that side of the spectrum, allowing warmer, redder light to shine, more comparable to old-school bulbs.
And yet, the only way to curb light pollution, advocates say, is to avoid lighting places that don’t need to be lit and to more specifically determine how much and what type of light is used in those that do.
Some critics may have raised safety concerns in response to the idea of dimming nighttime lighting. But advocates argue that excessive coverage suggests feeling safety is greater than actual protection, and this quantity is not necessarily equal to quality. For example, glare caused by excessive light can both irritate your eyes and interfere with your ability to see clearly while driving, which can jeopardize your own safety and that of others.
“There is a perception that light makes us safer, and because some light makes us safer, more light should make us safer,” Hartley said. “And the reality is that when you look at it, really good quality light can improve safety at night, and that really has to do with using it correctly.”
The effects of light pollution and how smarter lighting can help
Much more research is needed to study the health effects of light pollution and to determine how much exposure to light is potentially harmful. But we know that many medical problems can be caused by a disturbance in our circadian rhythm, our internal biological clock, which is largely regulated by light. A 2017 Harvard study found a correlation between breast cancer incidence and increased nighttime lighting, which was particularly strong among women working night shifts.
There is also evidence that the burden of exposure to light pollution is disproportionately borne by communities of color. A 2020 study by the University of Utah found that adjusted for population differences, Asians, Hispanics, and blacks in the United States, on average, were exposed to twice as much light in their neighborhoods as whites.
“It’s the same story that repeats itself over and over in terms of relationships with these disadvantaged, marginalized communities and a range of polluters,” Hartley said.
The most environmentally friendly light never comes on, Hartley says. When it comes to lighting design, he recommends starting “with natural darkness and [adding] light where you need it. “
Defenders stress that, compared to many other types of pollution that our planet suffers from, the solution to the problem of excessive lighting is relatively easy.
“This is not like pollution of soil, water or plastic in the ocean. This is easy to fix, ”Turnschek said. She said that part of understanding the negative effects of light pollution requires re-evaluating our own cultural association with light as inherently safe and positive, and dark as dangerous and intimidating.
Her own love for the night sky – along with teaching the constant stream of astronomer students who had never personally seen the Milky Way – prompted her to start spreading information about light pollution in the city many years ago. She claims there is a lot at stake when it comes to gradually losing sight of space.
“I think we are losing the fact that everyone is connected. We are all under the same sky, ”Turnschek said. “This planet is planet A, but planet B is not. We have to take care of her. “
And, according to Erwin, the new ordinance is another step towards bringing heaven back to Pittsburgh residents.