IRA FLATOW: Utah is known for its Great Salt Lake, as we’ve been saying. It’s also known for its dinosaurs. We’ll talk about that a bit later in the show.

But it’s also known for having some of the darkest skies. I can’t wait to get out there when I go on my trip through Utah to see the dark skies. It’s famous to astronomers from more than 50 years ago, started the dark skies movement to try to preserve the night sky as a natural resource.

But a dark sky is more than just a backdrop for star gazing. More studies are showing that light pollution is harmful to bird migration, animal behavior, air quality, and even human health. Joining me to tell us more about the potential harm caused by light pollution is Jess Dwyer, biologist, educator, and founder of Dark Sky SLC. Welcome to Science Friday.

JESSICA DWYER: Thanks so much.

[APPLAUSE AND CHEERING]

IRA FLATOW: Now the video was talking about how life sort of stops our production of melatonin, right?

JESSICA DWYER: Yep.

IRA FLATOW: So that keeps us from going to sleep. When did we first realize how much of an effect light has on a lot of things in our health.

JESSICA DWYER: I think we first realized it when we started asking people to turn out the light when we wanted to sleep. We started having data. The biggest piece of evidence came from a massive study called the Nurses’ Study, that looked at over 200,000 nurses and found that nurses who do shift work were six times more likely to contract breast cancer than their non-nightworking peers.

And we didn’t really understand that. We thought, oh, maybe it’s something about staying up all night. And then in the same study, we were able to look at those nurses neighborhoods, analyze satellite imagery, and identify that even day sleeping nurses in more light polluted neighborhoods were at increased risk of breast cancer.

IRA FLATOW: Do we know what the mechanism is for the increases in cancer and other illnesses?

JESSICA DWYER: Yes and no. In that just this last year, the Nobel Prize in biology was awarded to the folks who found a mechanistic location of our circadian rhythm in our cells. So this is really new science.

That being said, the basics are that our optic nerve cruises into our brain right in the center of most of our hormonal control. So we can understand that there’s a relationship there. If we’re seeing a physical relationship and the impacts, now we just need to discover that mechanism.

IRA FLATOW: So what kind of other diseases are linked to not getting sleep or the light keeping us awake.

JESSICA DWYER: Most of them are ones that we can think of being liked with hormones. So referenced in the video, anything to do with serotonin or dopamine. So anxiety and depression. Anything helping us regulate our adrenaline, which then impacts our heart, we see increased risk of heart disease.

IRA FLATOW: Heart disease. You stopped that the big one.

JESSICA DWYER: That’s true.

IRA FLATOW: That’s important.

JESSICA DWYER: Yeah, and the tricksy thing about it is, it’s really hard to track, because the location and the way that light finds its way into our homes if we’re sleeping, or how long we look at our screens at night is tough to check on a person by person basis.

IRA FLATOW: Yeah, I was reading some of your research. And I noticed that your studies show that [INAUDIBLE] at night can actually make air quality worse.

JESSICA DWYER: Oh that was really important to hear, and your mic cut out, so I’m going to repeat it. Yeah, some research came out last year published in Nature, and indicates that there’s a scrubbing quality to dark skies. So photochemical smog, ozone, gnarly stuff comes out of our tailpipes. It goes through a couple of iterations with photons from the sun, and turns into ozone which is really good at tearing up our lung tissue.

So what we discovered in that Nature paper, was that with the addition of energy throughout the night, those precursors to ozone stayed at higher levels. So once the sun came up, we were one step closer to making ozone. So we used to make ozone at lower levels. Now it takes the same amount of energy to increase ozone production.

IRA FLATOW: That’s really interesting. You know all day we’ve been smelling smoke from the forest fires nearby here. And will the artificial light make it harder for that smoky haze here in Salt Lake? Harder to disperse it?

JESSICA DWYER: Yeah, we’re super lucky here. We get two kinds of air pollution to look out for. So the first kind, photochemical smog, the photons are a part of the story. Particulate matter is what we deal with during our inversions. And that’s what you’re tasting when you go outside right now with the smoke.

So not directly. Photons don’t increase that. But if we think about those light fixtures, they waste 60% of the light that they produce.

So nationwide that means we could save about $3 billion a year if we just stopped using 60% of that wasted light. If we think about the fossil fuels that go to make that light, and the way they’re increasing climate change, and the way climate change is increasing the frequency and severity of forest fires, then we can make a connection.

[APPLAUSE AND CHEERING]

IRA FLATOW: OK, but what do you say to people who say, you know, I want to feel safe outside at night? I don’t want you to take all my streetlights away.

JESSICA DWYER: Yeah, I was one of those people. My friends call me Safety Jess. I have a CPR mask on my key chain just in case.

I text folks like when I’m going to the bathroom just so they know where I am. So I wasn’t sold on the safety thing either until I saw some really robust studies. Chicago was concerned about this in the early aughts, and they compared a really rough neighborhood. And they split, so they watched for a year, took some crime stats, and then in every alley installed increased lighting. In every type of crime they saw an increase with an increase in lighted spaces at night.

We’ve seen that replicated across 62 cities across the world. And we think that it has to do with the way that glare impacts our eye. So in a lit alley there are actually darker spaces for potential assailants to hide, because our eyes calibrate to the brightest thing. We’re actually removing our eyes natural ability to adjust to darkness.

IRA FLATOW: Is there a way that we can change the lighting fixtures on the street so that maybe it doesn’t pollute the neighborhood for everybody else trying to sleep

JESSICA DWYER: There’s so many ways. That the best thing about working with light pollution is it’s win, win, win. We can save money. We can feel better. And we can get access to the cosmos again.

So the first thing is just off when you don’t need it. And then we want to make sure that the bulb is fully shielded. And then, oddly, we’re going to make sure that our color looks an amber orange, but has a color temperature of 2,700 Kelvin or below.

IRA FLATOW: What’s that? So repeat that again.

JESSICA DWYER: Yeah, a color temperature is a way that we measure the amount of energy coming out of a light bulb, or any light emitting source. We measure it in Kelvin. So we want our light at a color temperature of 27,000 Kelvin or lower.

IRA FLATOW: 2,700?

JESSICA DWYER: Oh sorry. Good catch. 2,700.

IRA FLATOW: 2,700. That’s like an incandescent, yellowish color, right?

JESSICA DWYER: So actually the lights in here are a nice amber color. And we can usually see it.

IRA FLATOW: Yeah.

JESSICA DWYER: If it feels cozy to look at. If it reminds us faintly of a camp fire, that’s a nice color to keep around. The bluer it looks, the bright, whiter it looks, the more it’s going to trick our brain into thinking that it’s daylight.

IRA FLATOW: With all the new bulbs being LEDs it should be easier for us to pick and choose a color, right? With the color temperature that you’re–

JESSICA DWYER: Yeah, the LED revolution was such a wonderful thing for energy savings and no one knew yet to look at color temperature. So we brought in a ton of very blue LEDs. What’s beautiful about it is that we’re learning how to change those color temperatures. And as the promise of an LED lifespan isn’t quite as long as we were promised, communities are now taking what we call a commitment clause to say that once those lights are ready to be replaced, they’re going to replace with Ember and 2,700 Kelvin light.

IRA FLATOW: Now I know you got into this movement because you’re a biologist, and because light at night actually affects bird migration. Explain how you put that together to what you’re doing now.

JESSICA DWYER: Yeah, unfortunately I didn’t put it together. The good folks at the Fatal Light Awareness Program in Toronto put this together when they walked around downtown during migration season and started collecting the bodies of birds that had collided with buildings. In North America, every year we lose one billion birds a year to bird collisions. One billion birds a year.

Passerines, songbirds, 2/3 of those kiddos migrate at night. And they do so because they’re tiny, and they want the cooler air temps, and they want the calmer winds. They’d like to avoid predation. And we see that they migrate using star-flight as they have for millennia.

And they get thrown off when they get into cities. Sometimes they die from exhaustion, and sometimes they actually die from collisions. So in Salt Lake Tracy Aviary, we’ve actually started our own campaign. It’s called the Salt Lake Avian Collision Survey. And you can volunteer as a citizen science and help us walk around downtown during migration, and see what we find. Sometimes it’s heartbreaking, but the data has really helped us to show that this is something that we need to be concerned with in the valley.

IRA FLATOW: Jess, thank you very much for taking the time to be with us today.

JESSICA DWYER: Thanks so much, Ira. It’s great to be here.

IRA FLATOW: Jess Dwyer, biologist, educator, and founder of Dark Sky SLC.

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