Scientists Warn Against Nasal Rinsing With Unboiled Tap Water

12:08 minutes

Nasal irrigation. A young girl uses the Neti Pot to treat her runny nose and colds. Nasal lavage, irrigation therapy.
Credit: Shutterstock

Researchers at the Centers For Disease Control and Prevention published a study Wednesday that examined 10 cases of life-threatening Acanthamoeba infections that occurred after people cleaned their sinuses with neti pots, squeeze bottles, or other nasal rinsing devices. In most of these cases, which occurred in immunocompromised individuals over the span of a few decades, individuals had used tap water for nasal rinsing.

Tap water, while generally safe to drink, is not sterile. Microorganisms and germs live in distribution systems and pipes that the water travels through, and Acanthamoeba amebae was the main link between the 10 cases, three of which resulted in death.

Although contracting the Acanthamoeba pathogen is extremely rare, many people are unaware of the unsterile nature of tap water and use it for their sinuses, according to a survey study published last year. A third of participants incorrectly believed U.S. tap water is sterile, and almost two-thirds assumed it was safe to rinse your sinuses with it.

The CDC and FDA recommend using distilled or sterile water for nasal rinsing. If you want to use tap water, they recommend boiling it for three to five minutes and allowing it to cool. While slightly more time consuming, it is an effective way to get sterile water.

Rachel Feltman, host of “The Weirdest Thing I Learned This Week,” joins Ira to talk about this story and other news in science this week, including a new study that links microplastics in the human body to increased risk of heart disease and death, why the U.S. maternal mortality rate might be inflated, and why cicadas produce high-speed jets of urine.

Segment Guests

Rachel Feltman

Rachel Feltman is author of Been There, Done That: A Rousing History of Sex, and is the host of “The Weirdest Thing I Learned This Week.”

Segment Transcript

IRA FLATOW: This is Science Friday. I’m Ira Flatow. Later in the hour, a look at how OB/GYNs are facing tough decisions about staying in abortion-restrictive states. Plus, a new book teaches the science of flavorful cooking. But first, in space news, reports of the death of Voyager 1 may be premature. NASA sent a signal to the faraway probe and was able to decipher meaningful information from it, keeping our fingers crossed as NASA wizards figure this one out and hoping this is nothing more than the aging spacecraft forgetting where it left the car keys.

There is concerning news this week, though, about microplastics being found in our bodies and now in our arteries. Last week, scientists in the New England Journal of Medicine published a study that linked microplastic presence in arteries to higher risk of heart disease. Ooh. Here to explain that study and other science news from the week is Rachel Feltman, host of the podcast The Weirdest Thing I Learned This Week. Rachel is based in Jersey City, New Jersey. Hi, welcome back, Rachel.

RACHEL FELTMAN: Hi, thanks for having me, Ira.

IRA FLATOW: Let’s go right to this. Microplastics study, it sounds alarming.

RACHEL FELTMAN: Yeah, you know, it is alarming. We’ve been seeing for years now that microplastics are everywhere. They’re in freshly fallen antarctic snow. They’re in the Mariana Trench. They’re in the clouds above Mt. Fuji. And they’re in human blood, breast milk, lungs, and even placentas. But we know very little about how exactly they affect us.

And that’s where this new study comes in. They found microplastics within the plaque that clogs human arteries, and they linked its presence to heart disease and death. So we’re getting closer now to actually understanding what these really insidious particles do. Basically, researchers, they followed 257 patients who had fatty plaques removed from their carotid arteries. This was in 2019 and 2020.

And of those 257, 150 patients were found to have polyethylene inside their plaques, which is just really, really viscerally upsetting to me and I’m sure many other folks. The study says that electron microscopy showed visible jagged-edged plastic particles. But what’s really troubling is that in following the patients for about three years, the researchers found that the people with those microplastics in their plaque were nearly five times more likely to suffer heart attacks, have strokes, or die.

IRA FLATOW: Oh, my goodness.

RACHEL FELTMAN: Yeah. And of course, they are quick to say this is a correlation. They didn’t show the exact mechanism. But you have to assume microplastics can’t help when you have plaque in your arteries. And the thought is that it could be driving increased inflammation, which, of course, we know is bad for you for many reasons. So yeah, I hope that we see a lot more research like this, even though I dread seeing it.

IRA FLATOW: Yeah, yeah. Well, speaking of something to dread seeing is another story in a new CDC study on neti pots and tap water. Tell me about that.

RACHEL FELTMAN: Yeah, always bringing you good news, Ira.


RACHEL FELTMAN: So more than a decade ago, health officials in the US linked deaths from brain-eating amoebas to the use of sinus irrigation tools like neti pots. But a new study from the CDC looked at 10 deaths over the last three decades from another amoeba that they now say was likely also transmitted via sinus rinse. So this was a thing we already knew could happen, but it’s a good reminder because while these infections are rare, what’s really worrying is that a lot of people don’t seem to realize that they’re putting themselves at risk–

IRA FLATOW: By using their tap water.

RACHEL FELTMAN: Yes, exactly. So a recent survey found that a third of people believe that US tap water is sterile, which is not true. It is treated to get rid of lots of microbes, but there’s lots of stuff living in pipes. There’s lots of biofilms in our plumbing, so definitely not sterile. And 62% of people in that survey thought it was safe to use tap water for rinsing your sinuses. 50% thought it was OK for rinsing contact lenses.

While tap water is generally safe to drink unless something has gone wrong, lots of those microorganisms that are in there that are safe to ingest are not safe to come into contact with your eyes, your sinuses, or your lungs. So if you are using a CPAP machine, if you’re using a sinus rinser, if you have contacts, you should always be using distilled water or boiling tap water for at least a minute, three minutes if you’re at high elevation, and then, of course, letting it cool. So it’s rare, but you really don’t want to be in that small percentage of people who get a brain-eating amoeba.

IRA FLATOW: I hate when that happens.


IRA FLATOW: And speaking of the CDC, they also have new travel guidance, right? about the measles vaccine?

RACHEL FELTMAN: Yeah, measles cases are going up in 17 states. And so now, the CDC says if you are traveling abroad, you should go see your doctor at least six weeks before to make sure that you are up to date on your vaccines. Because we are seeing cases of people who are eligible to be vaccinated but who are not going abroad, getting measles, and bringing it back and that leading to outbreaks in the US. There’s a 30-fold increase in measles cases in Europe. And the solution is really simple. Get vaccinated, make sure you’re up to date. If you’re at least six months old, you should be vaccinated against measles.

IRA FLATOW: Hm. Let’s turn to some welcome news about death if that’s possible. It turns out the maternal mortality rate may not be as high as the CDC reports?

RACHEL FELTMAN: Yeah, this is really interesting. Because it turns out while there’s still reason to be concerned about maternal mortality in the US, a clerical error may have been skewing data. So the most recent reports from the CDC said that there were 32.9 deaths per 100,000 births in the US, which was really a shocking outlier. For example, in 2020, the maternal mortality rate of all high-income countries was at 12 deaths per 100,000. So we were looking at close to three times as many in the US.

It turns out that the real number may be closer to what you would expect, something around 10.4 deaths per 100,000. Researchers decided to look into this pregnancy checkbox that’s on the national death certificate. It was added about 20 years ago, and it’s apparently been known for some time that this leads to some clerical errors, where, really, any time the box is checked, something tends to get registered as maternal mortality, even when the pregnancy had nothing to do with the death.

And in fact, sometimes people who weren’t pregnant at all, this box gets checked accidentally. So researchers just dug into the data to try to pull out those false positives, and they ended up with a number much closer to what we would expect. But the really important thing to note here is that even with this clerical error fixed, the racial disparities we see in US maternal mortality rates persist. Black pregnant patients are still three times more likely to die than white patients, and most of these deaths are preventable. So it’s not that this isn’t a problem, but we always want to have the correct data when we’re tackling something like that.

IRA FLATOW: That’s right. And let me follow up that story with another one, which for some reason on this show, we’re always coming up with a story about bodily functions if you know what I mean, right?


IRA FLATOW: I know you do. Because this week comes news that cicadas have a bodily function that’s more similar to larger animals than insects their own size. I know it’s your story, so tell us about it.

RACHEL FELTMAN: Yeah, so luckily for all of us, there are scientists who study the fluid dynamics of pee. Thank goodness. And one thing that is generally true is that most large animals, like us, produce steady streams of urine while smaller creatures make droplets. As an aside, producing little pee droplets doesn’t mean that pee is short range. Last year, there was a study from these same researchers, actually–

IRA FLATOW: I remember.

RACHEL FELTMAN: Yeah, the glassy-winged sharpshooter. It uses this phenomenon called super propulsion to launch its little urine beads off its butt at ballistic speeds. But anyway, these same researchers have now turned to cicadas, which, I guess, just like have to be the most aesthetically unpleasant insects in the world because they apparently break the mold, and they produce urine in high-speed jets, the strongest stream of pee relative to their body size of any animal ever studied, so good for them.

IRA FLATOW: Wow. And this– I’m just– my mind, if you could see my brain–


And this is especially relevant now because we’re expecting a double-brood season this spring in the US, right?

RACHEL FELTMAN: We are. We are having a dual emergence. A 13- and 17-year brood are overlapping in the same part of the country. The good news is that the overlap is very minimal. So while it’s true that the country, as a whole, is going to see trillions of cicadas this year, most folks will see a normal number for an emergence year.


RACHEL FELTMAN: The broods are most likely to come into contact with each other around Springfield, Illinois. But even there, the overlap is likely to be pretty incidental in a few wooded areas. But if it seems like they’re a little more obtrusive than usual, you can blame the double emergence. I don’t think anyone’s going to fact check that.

IRA FLATOW: Yeah. But now, we know a little bit more about them, so they’re a little more interesting.

RACHEL FELTMAN: Yeah, and maybe wear a hat when you’re outside.

IRA FLATOW: [LAUGHS] All right, last story, closer to home. It turns out that Mars’s gravity might be influencing our oceans. Tell me about that.

RACHEL FELTMAN: Yeah, it’s so wild. Basically, researchers, they dug a bunch of sediment from the deep sea to try to track how ocean currents have changed, deep-sea ocean currents, over the last 65 million years. And they found this cycle where currents were getting stronger or weaker every 2.4 million years, and they say the only way to explain the interval is our planet’s resonance with Mars or how our planet’s gravity fields interfere with each other, which changes the eccentricity of their orbits. Basically, Mars pulls Earth slightly closer to the sun sometimes, which exposes us to more solar radiation. And that strengthens deep-ocean currents.

IRA FLATOW: Wow, so it’s not just climate change that’s changing the ocean currents?

RACHEL FELTMAN: Yes. And of course, the researchers were quick to say, yes, we get exposed to more solar radiation when Mars pulls us closer to the sun. No, this cannot explain away climate change. That is definitely still a thing that’s happening because of greenhouse gases. But this is another phenomenon. And in fact, it might actually, they say, mean that ocean currents can like keep up some of their circulation once climate change has deadened the water mixing that we rely on. It’s a small constellation, but you know.

IRA FLATOW: Yeah, cue the theremin martian music– [IMITATES MARTIAN MUSIC]


IRA FLATOW: Wow. [LAUGHS] Wow. Thank you, Rachel. Always great stuff. Always good to hear from you.


IRA FLATOW: Rachel Feltman, host of the podcast The Weirdest Thing I Learned This Week. Rachel is based in Jersey City, New Jersey.

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