IRA FLATOW: This is Science Friday. I’m Ira Flatow.

KATHLEEN DAVIS: And I’m Kathleen Davis. Later in the hour, the role of glial cells in the brain and the gut. And we’ll head to Colorado to hear how beekeepers are trying to protect their hives against a parasitic mite.

But first, this week, the EPA unveiled national limits for the level of PFAS chemicals that are acceptable in drinking water supplies. Those are the so-called forever chemicals that have commonly been used for things like fire retardants and also oil- and water-repellent coatings and now are found just about everywhere. Water treatment plants will now have to test and treat for several varieties of the chemicals. Here to explain that and other science stories of the week is Sophie Bushwick, senior news editor at New Scientist. Welcome back, Sophie.

SOPHIE BUSHWICK: Thanks for having me.

KATHLEEN DAVIS: So tell me about these PFAS chemicals. What are they? And why is this such a big deal?

SOPHIE BUSHWICK: You’ve probably heard of PFAS chemicals or at least the nickname, forever chemicals. These are substances that are really, really hard to destroy. And they’ve been associated with health issues, a higher risk of certain cancers, reproductive issues. There are things that the EPA really wants to get out of the drinking water. And that’s exactly what they’ve done with this restriction.

They’ve restricted the levels of six different PFAS. The problem is that there’s 12,000 different kinds of PFAS. And when you realize there’s an issue with one, a lot of the companies who are using it will replace it with a substance that’s actually pretty similar chemically.

So there’s the risk that these companies will say, look, we’re responding to this restriction. We’re going to phase out this chemical. But they’ll just replace it with something that’s quite similar.

KATHLEEN DAVIS: So the EPA is limiting the amount of these chemicals that’s being found?

SOPHIE BUSHWICK: The EPA has set these limits for how much is allowable in drinking water. So the point where the restriction is is with the water companies. Previously, there’s been cases where one company sued a manufacturer of PFAS because the manufacturer had made it. That’s how it had gotten into the drinking water supply in the first place.

And so they thought that they should be the ones helping to pay for filtering it out of the water. And they actually won that suit. So it’s possible that there will be sort of a ripple effect from the EPA’s restriction on drinking water, which will affect directly the people who manufacture these plastics.

KATHLEEN DAVIS: And do water companies know how to go about removing these chemicals?

SOPHIE BUSHWICK: They do. You can use a certain kind of charcoal filter. You can use known techniques, like reverse osmosis. They kind of know what to do. The issue is that just any of these technologies requires financial support. And so the EPA has given them a few years to make sure that they’re hitting those limits.

KATHLEEN DAVIS: Yeah. I mean, this sounds like a huge effort. And I assume it’s going to be expensive. So is the government providing any support for doing this? Is there money to help?

SOPHIE BUSHWICK: There actually is. So as part of the infrastructure bill that passed a few years ago, there’s about $1 billion in funding available for states and territories that want to start testing and treating water for PFAS. And they also have some of that funding for people who own private wells as well as for those bigger public water systems.

KATHLEEN DAVIS: So let’s move on to another health story, which is quite different. This is a story about a possible new vaccine for urinary tract infections.

SOPHIE BUSHWICK: That’s right. So urinary tract infections are the most common bladder infections. They disproportionately affect women. And about half of women will experience a UTI at least once over her lifetime.

So we know how to treat them. We treat them with antibiotics. But antibiotics are kind of a harsh chemical. They kill all bacteria, not just the ones that you’re aiming to kill. And they also can lead to issues, such as antibiotic resistance.

So there’s been a couple different studies looking at, could we try to vaccinate people against UTIs instead of just waiting for people to get sick and then treating them? And in this particular case, they wanted a vaccine that would be easy to take, that wouldn’t have a risk of someone choking, and that would be pleasant. So they’ve developed an oral spray that is pineapple flavored that’s sprayed under the tongue.

The idea is you actually would get this spray treatment for three months every day, getting the spray under the tongue. And then after that three-month period, you would be considered vaccinated. And then they tested. They did a clinical trial. How many of the people who received this treatment remained UTI-free?

The test period was about nine years. A little more than half of people who received the treatment avoided UTIs for that whole period. And most people in the study avoided them for an average of about 4 and 1/2 years.

KATHLEEN DAVIS: So would this be a vaccine in theory that everyone would get or just if you’ve been really susceptible to UTIs?

SOPHIE BUSHWICK: Yeah. This might be something that people who have suffered from recurrent UTIs would be interested in. One in four people who get UTIs are prone to these repeat infections, which can be really rough, especially if you’ve got to take a bunch of antibiotics each time you get it.

KATHLEEN DAVIS: OK. I’m still kind of stuck on the pineapple thing. I assume that’s just so that it tastes good enough that people are like, ooh, I’m going to take my vaccine.

SOPHIE BUSHWICK: Exactly. Yeah. The idea is that– what’s something that people would actually want to take every day? Because that treatment period’s so long, it’s not as much fun to take a pill every day as it is to get a little pineapple spritz.

KATHLEEN DAVIS: OK. Speaking of delicious medicine, we have another story. New York City is launching a new tactic in its war against rats. And that is birth control.

SOPHIE BUSHWICK: Delicious birth control, to be exact. They are these pellets that are packed with fat and salt and also with contraceptives. And the idea is they’ve just started a pilot to try to distribute these pellets and see if this can contribute to getting rid of rats.

The idea isn’t that this is a standalone solution. But this is just one mitigation measure, along with New York’s attempt to instead of putting garbage in loose, smelly bags on the sidewalk, to start putting them in containers like most other cities do. That is another big step towards reducing the buffet for rats.

KATHLEEN DAVIS: Mm-hmm. Why is this better than the methods that have traditionally been used in the city against rats?

SOPHIE BUSHWICK: What’s happened before is they’ve tried to put out rodenticide, poisons to poison rats and to keep the population down. But the problem is other animals eat rats. So this was most famously the eagle-owl, Flaco. This celebrity bird died in part because it had been consuming rats. It had this poison in its system, not from taking it itself, but from eating animals that had eaten poison.

So the idea is that by feeding the rats contraceptives instead of poison, you’re avoiding that problem of the damage going up the food chain. But I mean, there have been other attempts to give rats contraceptives in the past that have not been successful. It seems like this is a different type of contraceptive, these fatty, salty pellets. But there’s not a strong history of this working. So we’ll see how the pilot pans out.

KATHLEEN DAVIS: All right. Well, we’ll see if it’s as delicious as pineapples.

[LAUGHTER]

But moving on, there is yet another new use for AI in the news. And this time, we’re looking at stool samples. Tell me about this.

SOPHIE BUSHWICK: That’s right. So about one in four people in the whole world end up suffering from intestinal parasites. It’s a big problem. It can cause malnutrition. It can cause– for children, it can cause problems with their cognitive development.

And there’s only a limited number of people who are trained to detect these parasites in stool samples. So why not outsource this particular issue to AI? And that’s what a new study just did. They trained an AI on these images of stool samples. And it was able to detect infections almost as often as a human technologist. And in some cases, it caught infections that the human didn’t.

KATHLEEN DAVIS: Well, great. Hopefully, it is successful. Let’s move on to some physics news. I know that you are a big physics person, Sophie. So–

SOPHIE BUSHWICK: I am.

KATHLEEN DAVIS: Let’s talk about the multiverse.

SOPHIE BUSHWICK: Yes.

KATHLEEN DAVIS: First of all, what is the multiverse?

SOPHIE BUSHWICK: So you’ve probably heard about the thought experiment of Schrodinger’s cat. There’s this cat in a box with a vial of poison. And whether or not the poison breaks depends on the decay of a particle.

And so the idea is you don’t know until you look in the box whether that cat is alive or dead. It sort of exists in both states. But once you open the box, the states collapse into the single either alive or dead state.

So the multiverse, the idea is that instead of them collapsing and one possibility vanishing, what really happens when you open the box and observe the cat is that there’s all of a sudden two different worlds. In one world, you’re looking at an alive cat. In another, you’re looking at a dead cat. So that’s the idea of the many-worlds theory, that every time you’ve got an observer looking at this quantum phenomenon, instead of just one possibility not being in existence anymore, the idea is you have multiple worlds in which all these possibilities exist.

KATHLEEN DAVIS: OK. So there’s new multiverse research out there. How do you go beyond different multiverses?

SOPHIE BUSHWICK: Sure. So the way you go beyond many-worlds theory is by having many-more-worlds theory, which is a great name. But the idea is basically the reason we’ve got all these thought experiments is researchers are trying to figure out, how do we go from this quantum phenomenon, this world that’s governed by the mathematical equations of quantum mechanics, which is the way the universe was right after the Big Bang, which is the way that we still observe very, very small objects, how does that then become the classical world in which larger objects, like you and I, function, that we’re instead governed by the rules of classical mechanics?

So one of the ways that they’re trying to figure that out is by having these different thought experiments. And one of them is the many-more-worlds interpretation. And the idea behind this is that there’s just a lot more worlds within each multiverse possibility.

One example you could think of is, let’s say you decide what to drink for breakfast. And let’s say that this is, in the multiverse, maybe in one world, you choose coffee. In another world, you choose tea. In another world, you choose orange juice, right?

Many more worlds says that within each of those worlds, there’s a ton of other realms. Within the orange juice world, there’s a multiverse in itself. And the idea behind this is they’re trying to get rid of the concept that you need an observer.

So with the Schrodinger’s cat example, you have to open that box and look inside it before you figure out whether the cat is alive or dead. But that requires you, the observer, to be there. And so what they’re trying to do with many-more-worlds interpretation is avoid that need, is to say, well, what about these quantum effects if we want to take the observer out of the equation?

KATHLEEN DAVIS: OK. You’re hurting my head a little bit, Sophie.

SOPHIE BUSHWICK: It hurts my head too.

KATHLEEN DAVIS: But presumably in a different multiverse, we’re still here doing this interview, but we’re still talking about the pineapple UTI vaccine because I cannot stop thinking about it.

SOPHIE BUSHWICK: In fact, I think there’s an infinite number of worlds in which we’re still talking about the pineapple spray.

KATHLEEN DAVIS: Great. All right. Well, finally, we’re almost out of time, but we wanted to remember the passing this week of one famous physicist, Peter Higgs. So tell me a little bit about Peter Higgs and why he was so impactful in physics.

SOPHIE BUSHWICK: Peter Higgs came up with this theory that explains essentially, what are the forces that hold the universe together? In particle theory, the idea is you have these particles that give rise to fields. But in order for these particles to stick together and form larger objects, like atoms, and then the atoms to form cells that form humans, you need to have mass.

So how do they get their mass? How do these particles have mass? And Higgs came up with this concept of a Higgs field, which is supported by a particle called a Higgs boson, which, essentially, when particles interact with it, they gain mass.

And at first, when he published this, it was not very well respected. But as the years went on, it became a foundational part of particle physics. And in fact, it was one of the reasons that the Large Hadron Collider at CERN– that experiment was developed in part to try to find the Higgs boson. And they eventually did in 2012, which was decades after Higgs’s original paper in the ’60s.

So he had this theory. He lived long enough to see it become foundational and to be proved. He won a Nobel for it. And then he died at home at age 94. So he really had an extraordinary life.

KATHLEEN DAVIS: Yeah. What a full and amazing life. Thank you so much, Sophie, for joining us as always.

SOPHIE BUSHWICK: Thanks. It’s always a pleasure to be here.

KATHLEEN DAVIS: Sophie Bushwick, senior news editor at New Scientist.

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