How can mosquitos smell you? (new research!)

How can mosquitoes sense us? And do they prefer some people over others? This is a question we've pursued across several episodes of the podcast in the past, but now there's some brand new research that addresses this question! Let's check it out together.
Melissa:

Hey. Hey. I'm Melissa.

Jam:

I'm Jam.

Melissa:

And I'm a chemist.

Jam:

And I'm not.

Melissa:

And welcome to chemistry for your life.

Jam:

The podcast helps you understand the chemistry of your everyday life.

Melissa:

Okay. So before we get started on today's episode, I wanna take a minute to shout out 2 of our new patrons. Yay.

Jam:

That's right. We had 2 people join our super cool community of patrons since we recorded last. Those people are Suzanne s And Jacob t.

Melissa:

Yay. And they joined at the dispersionaries level, so they're the dispersion forces.

Jam:

Nice.

Melissa:

Which, you know, that's what

Jam:

atpatreon.com/chem for your life.

Melissa:

And, for those of you who have already joined, Jim and I are working on writing on our thank you notes and sending those out this week. But now let's switch gears, and we're gonna talk about today's episode. So this episode is a little bit different. We're gonna be talking about just 1 research study or 1 paper that came out recently about mosquitoes. And this is a study that was sent to us by a listener, mister Hollis.

Melissa:

Nice. And, we we visited his class before. Yeah. He's a high school chemistry teacher. He gets really excited about everyday life applications.

Melissa:

He was one of 1st teachers we'd heard from.

Jam:

Yeah. That's true.

Melissa:

And so we're just gonna highlight this 1 paper. And I don't know that we've done that before where we just choose 1 paper.

Jam:

I don't know if we have it either. I feel like

Melissa:

One research study.

Jam:

There have been episodes where you specifically just focus on research you found

Melissa:

Yes.

Jam:

That is kind of new or whatever, but We have not, I don't think, just focused on one new thing.

Melissa:

Yes. So this is the latest installment in our mosquito saga. And I thought we only did 3 episodes, but you were looking back in actually, I guess we did 4. Yeah.

Jam:

Yeah. We spent some time in Mosquito Land, I guess.

Melissa:

I totally forgot about that. So we did the original why do they bite people, which we rebroadcasted last week.

Jam:

Uh-huh. Mhmm.

Melissa:

And then Why do they bite some people more than others?

Jam:

Mhmm.

Melissa:

And then we did what about mosquito repellent? So what's the what Yes. How do these things work? And then we did what are new ideas for mosquito repellents.

Jam:

Right. And that was, like, a a little bit similar sense that you were looking at What research is happening right now, but as a few different sources and

Melissa:

That was the one I had forgotten about. Yeah. Sorry, folks.

Jam:

We've I mean, it's rare for us to have done that many of something. You know? Like, most of our series are like, oh, we did 2 episodes or 3 episodes on this

Melissa:

or whatever. Maybe only recycling is as close, I think.

Jam:

Right. Right.

Melissa:

Oh, that was a saga too.

Jam:

Yeah.

Melissa:

It was really heartbreaking. They were cycling. The mosquitoes, what I remember learning, how much Indigenous knowledge had already been working to repel its mosquito repellent, and then we just kinda were throwing things at a wall. Yeah. How funny it was to me that that the science was kind of they were like, we don't know why, but it works.

Melissa:

Yeah. Yeah. I remember being, really enjoying that part of that episode. Okay. So this episode is going to be going through 1 journal article article or study.

Melissa:

So when I say a paper like that, usually what I mean is when scientists do work, we'll write all of our work up, And then we submit it to a journal to publish. And usually what will happen is there will be 2 to 3 peers who work in the similar field or the same field who review that paper and decide or, like, that's been submitted and decide, is this sound solid science with novel findings? And if so, then usually, maybe it'll have a few edits or round of edits, and then it'll go on to be published in a journal. And that's what I like to call a paper. Okay.

Melissa:

So when I say that, a paper is really summarizing 1 or a series of research studies, and it's published in a peer reviewed journal article.

Jam:

Okay.

Melissa:

So what the structure of this episode is gonna be, I'm gonna do a quick revisit of last week's episode very quick. If you want the more in-depth, go back and listen to that rebroadcast.

Jam:

K.

Melissa:

Then I'm gonna summarize the study, and then we're gonna kinda take a little break, and we're gonna do some chemistry lessons.

Jam:

Okay.

Melissa:

So and then kind of wrap up the study. So those chemistry lessons, though, most of them we have done before. So it's more like a chemistry review.

Jam:

Okay.

Melissa:

But still, we'll relate it back to the chemistry that we know and have talked about a lot. And if this is your 1st time listening, then, You know, you'll get an overview of those concepts as well. Okay. Okay. So to revisit last week's episode Actually, do you remember, Jim, you had to answer a question about this in our 1 hundredth episode?

Melissa:

Uh-huh. I thought We maybe I could quiz you on it again. Do you remember the 3 things that mosquitoes look for humans based on?

Jam:

Body temperature?

Melissa:

Temp body temperature. Yep.

Jam:

C o two

Melissa:

Yes.

Jam:

That we breathe out? Yep. And, like, just Odors

Melissa:

Yes.

Jam:

That humans give off?

Melissa:

Uh-huh. Skin odor. So body temperature and c o two, most mammals have those. Likely the thing that indicates to the mosquitoes that they want humans and not some other prey.

Jam:

Okay.

Melissa:

And when we say volatile organic compounds or volatile organic what we mean is if you have some molecules on your skin that are easily turned into vapor that we can smell, that's the volatile part.

Jam:

Okay.

Melissa:

I think sometimes we think of volatile as explosive. But in organic chemistry or in chemistry in general, volatile means it can be turned into a gas.

Jam:

Oh, okay.

Melissa:

So then you can smell it. It'll hit those odor receptors. And when we say organic molecules, those I mean, I think, technically, to be an organic molecule, you just have to have one present. Okay. But a lot of these have a carbon backbone.

Melissa:

Like, lots of carbons make up the base, and then they have little attachments on them.

Jam:

Okay.

Melissa:

So that's the background of why mosquitoes seem to be attracted to humans.

Jam:

Okay.

Melissa:

And then we also talked about why some humans are more attractive to mosquitoes than others based on, like, That person sometimes are more attracted to other times. Do you remember what things those were?

Jam:

I feel like I remember The body temperature thing can vary based on people, including, like, Pregnant women?

Melissa:

Yes. But not necessarily body temperature. That could be part of it, but also they could their Breath volume doubles.

Jam:

Right. Right.

Melissa:

So we don't know which one of the factors makes pregnant people more attractive Right. I don't think. And I

Jam:

guess you could You could make that same case about people who are just smaller and have more lung capacity from like that than people who are bigger. Like

Melissa:

Yeah. We don't know.

Jam:

If you could see through the eyes of a mosquito, there'd probably be people who just are a bunch more c o two coming out Yeah. And people who have a little less. And if you're trying to make a choice, And one looks better than the other one.

Melissa:

Right. I feel

Jam:

like did we talk about that the volatile organic molecules does just also vary from person to person quite a bit?

Melissa:

They can vary from person to person. So what, I probably asked the question badly, but I know they did a study where they had several women in These huts with a mosquito net, and they tried to see which hut had more mosquitoes at the end of the night, and they followed them overnight. And then also the thing they talked about was alcohol consumption. Oh. So the same person before and after drinking alcohol.

Melissa:

And we didn't know, did that Change of volatile organic compounds, does that change the body temperature? Does that change the c o two? Not sure about that. I also found a study recently that says if they have malaria, there's a point within the malaria infection where they're more attractive to mosquitoes, which seems Terrible because that means mosquitoes are eating the malaria blood and then spreading.

Jam:

Yeah. That's right.

Melissa:

Maybe is the point of malaria. I don't know. Yeah.

Jam:

Or maybe just explains its yeah.

Melissa:

Prevalence and association from mosquitoes. Yeah. Something like that. So we know that some humans may be more attractive to others based on if they're pregnant or not. Maybe the same human could be more attractive if it has alcohol consumption.

Melissa:

And then it seemed like there were some studies that indicated That this some people were just in general more attractive to others, but there wasn't a lot of evidence for why. Mhmm. So that's what this new study addresses.

Jam:

One thing I think I'm a rest talking about

Melissa:

Mhmm.

Jam:

That's a common theory, but doesn't seem like it has been proven at all. It's just the blood types thing. Yes. People seem to be out there in the world just convinced that blood types makes a huge difference.

Melissa:

Does not.

Jam:

But it doesn't. And but other things definitely do

Melissa:

Yes.

Jam:

Which we did talk about.

Melissa:

Yes. So blood type seems to be, yeah, a very common you know, I don't know why, but a very common misconception. So I'm glad you reminded me of that because then we even after the episode, somebody asked about that as well in a q and r, I think.

Jam:

All the times I think almost maybe say 9 out of 10 times that I've Brought this episode up to people in real life, it's because they'll say something like that to me.

Melissa:

Oh, really?

Jam:

The bot type say is very prevalent. I'm surprised. But the other day, it was maybe, like, don't know. 2, 3 weeks ago, a friend of ours was like, I always get bit more frequently. I mean, I do have type, you know, whatever blood and blah, and I was like, Actually, like, you you may still get bit more than everybody else, but don't worry about your blood type.

Melissa:

Well and I will say that, I guess, what I'm about to tell you, there's the correlation idea, but not causation. So Right. With this study we're about to talk about, they find something that consistently correlates to people who are more attractive, but we don't know. I mean, I guess it Could be blood type. There's no evidence that there is, but there's also no evidence that there isn't.

Melissa:

Right?

Jam:

It's like it's been completely disproven.

Melissa:

Right. Forever and ever. It could be that it turns out that somebody with this blood type does have this thing that makes them more attractive. We just don't know that yet.

Jam:

Right.

Melissa:

Right. People talk about it. Like, we do know it yet, but we don't know it yet. So it that could be. It might not be.

Melissa:

We don't know. Science hasn't Science hasn't gotten around to addressing that that I've seen. Yeah. But it's definitely not in the initial attractor, which is the c o two, the temperature, and the skin odor, Unless your blood type does something to those 3 things. Yeah.

Melissa:

That's the only way I could see blood type being a deciding factor.

Jam:

Yeah. And we haven't, like, completely disproven the possibility that people with certain blood types just smell worse.

Melissa:

Yeah. You know? Maybe so. And mosquitoes

Jam:

like that.

Melissa:

So Yeah. Mosquitoes like that. Yeah.

Jam:

I love the idea that you could basically say science has not disproven blah blah blah.

Melissa:

Yes.

Jam:

And then you can say any nonsense you want to.

Melissa:

And it

Jam:

just sort of sounds a little bit smarter because you said science Has not disproven? Right.

Melissa:

It was It's almost like you had to go look that up and make sure.

Jam:

Yeah. Yeah.

Melissa:

But but it might be that science just never tried to because it Just silly?

Jam:

Yeah. Silly at

Melissa:

night. Has not disproven that people who drink coffee black are better. But

Jam:

Yeah.

Melissa:

I mean, we just don't know that Yeah.

Jam:

We don't know that yet. But don't go out and do that unless you're it's obviously you're kidding because

Melissa:

Just kidding.

Jam:

Then it's funny and it's great, but it otherwise, it's

Melissa:

That

Jam:

is what we call the Internet.

Melissa:

That is what we call the Internet. And, also, I don't drink coffee black, so I'm not in favor of that interpretation.

Jam:

Right. Right. I'll send you some I'll send you some articles. Journal articles.

Melissa:

Okay. So that's what this study is all about today is about Why are some people more attractive than others? And, also, are they even consistently more attractive than others, or is this just sort of like like a Confirmation bias type situation.

Jam:

Right.

Melissa:

And I remember both you and I talking about how we don't really experience a lot of Mosquito oh, like, we'll be with other people, and they'll complain, and we're like, what? That didn't happen to us. Yeah. So well, it turns out that is scientifically Probably likely that we do consistently attract mosquitoes less than other people. Okay.

Melissa:

So that's what this whole study is about is addressing this idea that are some people more attractive to mosquitoes than others. And I'm gonna say this a lot in this episode, the word attractive. And when I say that, I mean, attractive to mosquitoes. So Jan just called me out, and we had to stop and rerecord because I said attractive multiple times. And it sounded like I just met people who look better.

Melissa:

Yeah. And, also, when I was telling Mason about this episode, sometimes I test them out on him. You know? I did the same thing, and he goes, oh, so people who are hotter? So yes.

Jam:

Said yes, body temperature wise.

Melissa:

Yes. Exactly. No. Not body temperature. That's not what we're finding.

Melissa:

Don't make any assumptions, Jim.

Jam:

Okay. Sorry.

Melissa:

So when I say tractive in this episode. I mean, attractive to mosquitoes. And that way, I don't have to say it every single time.

Jam:

Yeah. That's a it has a little bit, like, cumbersome to say each time Yes. Close you down. That makes sense.

Melissa:

That's the let's just all agree that that's what I mean. But you could And don't do this. You could cut me saying just attractive at one point and then post it on the Internet and spread misinformation. So I could do that. Don't be that guy.

Jam:

That's just why that's why Melissa doesn't cross me. It's like, there's always that could do.

Melissa:

There is. Yeah. Jam has lots of recordings of me Saying things that I probably wouldn't want on the Internet, like curse words or who knows what. Okay.

Jam:

And, I mean, likewise, I have just as many, Like, incriminating things recorded of me. But But

Melissa:

I don't have access to those. That's right. Okay. So this new study came out, and it was done in the lab of doctor Leslie Vassall, I think, is the way you pronounce it. She seemed to be the the principal investigator of the lab, so this is a fun chance to talk how labs work.

Melissa:

Usually in research groups or research labs, there's a what they call a PI, a primary investigator, principal investigator, And that person is the person who has the PhD and works at that university, and they usually get funding by writing grants. And they so they have money to fund their projects. So they write grants to foundations that award money, And that's if they have enough money to buy molecules or whatever they need to buy. Yeah. But for organic lab, it was by the the specific molecules we might need, by, equipment we might need, and then they also might pay your salary or something like that.

Jam:

Okay.

Melissa:

So when I was in grad school, my boss, my primary investigator, that's the person who did who ran our lab, who Started it, had the research ideas, all of that. Uh-huh. Now my new place where I have a postdoc is a principal investigator, a primary investigator, the PI. That's my boss. And then I, as a postdoc, work for him, and I sort of am, like, in between a grad student and him.

Melissa:

Right? So I have my PhD. I've learned about what Some of the basics of our field are I've conducted independent research with a little bit of mentorship, and now I'm in a place where I can do that a little bit more independently, less hands on Help needed than a grad student maybe.

Jam:

Right.

Melissa:

And I can also serve to help out the grad students.

Jam:

Right. Right.

Melissa:

And so a lot of times, When a postdoc comes to a lab, they'll get a specific project or they get to design a project that they're interested in.

Jam:

Okay.

Melissa:

So this project that we're gonna talk about seems to be, based on the paper, the primary project of doctor Maria Elena dei Obaldia. So she is a postdoc just like me, and, she also has a Twitter where she tweeted about this paper.

Jam:

Nice.

Melissa:

So we'll retweet that when this episode comes out, and you can go follow her because I'm sure she's gonna keep doing a lot of really cool work

Jam:

there.

Melissa:

So In the paper, they stated I'm gonna say they because it's the authors. Because usually, there's the main person who works on the paper or the project, and then there are other people who help. In this case, the postdoc probably headed up this project to a degree, and then it seemed like she had grad students that were working with her on it and maybe even some undergrad researchers. So when I say they, I mean, all the people listed as authors on the paper who contributed to the study.

Jam:

Okay.

Melissa:

So they stated that throughout this study, which lasted more than 3 years, they conducted More than 2,300 behavioral trials on these mosquitoes.

Jam:

Oh my gosh.

Melissa:

I know. That's so many.

Jam:

Seriously, I can't even comprehend that.

Melissa:

I know. Isn't that wild? And that's part of why I wanted to share about this work. It shows so much about much work goes into just 1 paper published and how much those scientists really have worked with this material oftentimes to come to the conclusions that they've come to.

Jam:

Yeah.

Melissa:

And so, also, I think sometimes people will be more, like, in admiration of people who have a lot of papers publish. But this paper has so much work put into it, but it's only 1 paper for 3 years of work. Right? So the number of papers published isn't everything. Sometimes it's the quality.

Jam:

Yeah.

Melissa:

And this paper was highlighted in Nature, which is not where it was published, but Nature Highlighted it and so did chemistry and engineering news. So it's a big deal that you know, it's a long term study, and people are really excited about it. Yeah. Yeah. So it focused on what, if any, odors could be making it to where mosquitoes were consistently attracted to some people more than others.

Jam:

Okay.

Melissa:

So they didn't look at body temperature. They didn't look at CO 2. They only looked at odors because they found that if you suppress the CO two Detection, right, that people still were being attractive to mosquitoes. So there's Yeah. More than just the c o two.

Melissa:

And they did have 2 a 2 part approach where they looked at some genetics where they were suppressing some genes, some sensors that the mosquitoes had, And then they did this other part that I'm gonna talk about more. That genetics part, very genetics heavy, a little bit over my head. I got the general idea. They basically breed some mosquitoes to not have genes which detect the molecules they suspected of, like, being the thing that drew them too. And although I think it was a weaker ability to detect, they were still able to tell which human should have been more attractive.

Melissa:

So it seemed like, basically, they found there's a lot of fail safes in their genetic code to be able to find the more attractive humans.

Jam:

Yeah. They find a way.

Melissa:

They find a way. What's the what's the Jurassic Park quote? Nature finds a way?

Jam:

I think it or life finds a way.

Melissa:

Life finds a way, something like that. Yeah. So, that was interesting, but a little bit more focused on the genetics.

Jam:

Okay.

Melissa:

So the other part was about identifying to mosquitoes, and they try to develop, like, an score to see how some people are attracted versus others.

Jam:

Okay.

Melissa:

And it has several parts. But first, they did a pilot study to compare the odor of 3 humans

Jam:

K.

Melissa:

Who maybe had varying level of mosquito attractiveness throughout these trials. So and I looked up how they did this because I was like, are they just letting these We'll get bit by a mosquito. That seems rude. But it seems like they and these people would have had to agree to participate in the study. So you know?

Melissa:

And it's Approved most likely by anytime you have human subjects, it has to be approved by this, internal review board that makes sure that you're not harming humans.

Jam:

Yeah. Yeah.

Melissa:

So what they did was have a fan, it seemed like, or some way to generate wind that blew the odors to a to an area where the mosquitoes were attracted to, not to the people themselves.

Jam:

Got it. Got it.

Melissa:

That's That was what I got from the paper.

Jam:

Okay. That's so funny, because imagine, like, those things were in place, and it was like, okay. These scientists, If camped out across the street from, you know, this coffee shop, something like that, they're releasing those mosquitoes, and they just have, like, these, like, binoculars and stuff. They're watching what she and then all these humans that are just drinking their coffee and eating their brunch are like, what? What's going on?

Melissa:

Well, actually, there are some trials. There are some experiments like That that don't have to be approved by IRB. It's not when you mess with the environment though. You're allowed to be in an environment and observe people in a public study and In the public setting and study them.

Jam:

Okay. Okay.

Melissa:

But if you're releasing the mosquitoes, then now you're doing something bad. Yeah. Yeah.

Jam:

You've genetically modified some mosquitoes, some mosquitoes and you're releasing them into the public.

Melissa:

Yeah. You can't do that.

Jam:

Yeah. For a good reason.

Melissa:

And that's more like observing humans. That's more like psychology research than it would be, like, about about mosquitoes. So

Jam:

Right.

Melissa:

But I imagine, like, people sticking because I kept about the arms. So I imagine people sticking their arms in a in, like, a plastic box and then the mosquitoes who were, like, being released. And I was like, that seems Unethical. Yeah. Yeah.

Melissa:

So then I found out that they I looked for that specifically and realized they were talking about, like, passing wind over the skin to, like, put the odors at a specific Place.

Jam:

Got it.

Melissa:

Okay. So that was kind of the first part. They did this pilot study with the actual human's arms, but not letting the mosquitoes bite the arms

Jam:

Yes.

Melissa:

And saw where the mosquitoes are more attractive, and they found that or where they're more attracted to, I guess, I should say.

Jam:

Uh-huh.

Melissa:

And they found that those 3 humans did seem to have varying levels of mosquito attractiveness throughout the trials. So that's great. So they now have confirmed this idea that these humans seem to have different levels of mosquito attractiveness.

Jam:

Okay.

Melissa:

So and they they sort of had them compete against each other. Uh-huh. I imagine like a I don't know what the vibe of the lab was like throughout this study, but Every time they talked about the competitions, I imagine, like, a March Madness bracket situation where people are, like, rooting for 1 over the other. Like, I don't know. I don't know the vibe of their lab, but that was, like, a funny thing to imagine.

Melissa:

Yeah. But so they had them compete against other, and they found, you know, someone who is strongly attractive, medium attractive, and weakly attractive to mosquitoes. Okay.

Jam:

So they're doing this as the person is naturally in their natural state.

Melissa:

In their natural state. So then they kind of Wanted to see if they could get the odor of human skin away from the humans themselves so that they had more freedom to do a lot of trials. Mhmm. And so they did this by having them wear nylons on their skin

Jam:

Okay.

Melissa:

For, 6 hours. So they, like, put Basically, pantyhose is what we call them or, like, an they're sometimes called nylons. That's what they're made out of.

Jam:

Right.

Melissa:

On their arms or tie. Sometimes they're tights. What I feel like tights have also taken on a new meeting lately.

Jam:

Yeah. Yeah.

Melissa:

So whatever you call those, the things you have to wear on your legs Going to church when you're a little kid is what I thought of.

Jam:

Yeah. Yeah. Same. Same.

Melissa:

Yeah. Definitely. Kidding. So they would wear those on their arms for, 6 hours, and then they would compare, you know, the actual human arm to the nylon and see if they were roughly equally attractive, statistically the same. Okay.

Melissa:

And they found that they were. Okay. So that way the humans didn't have to be there. Right. Right.

Melissa:

Opens up a whole new set of experiments that they can do a lot Right. Where there are not humans present, you know, that they can Test a lot of different things.

Jam:

Yeah. And not have to worry about, like, the mosquitoes actually biting or not or whatever. Yeah. But suddenly, you don't have to try to get Keter's oftentimes or something like that.

Melissa:

Yeah. Whatever the whatever the issue is.

Jam:

Yeah.

Melissa:

So they, they did a lot of controls 2. They compared the worn nylons, the actual human odor. They compared 2 worn nylons from the same person to each other to make there wasn't a difference for any reason. They compared a worn nylon to a nonworn nylon. You know, they did all the tests to sort of make sure that the mosquitoes were being attracted to the odor that got imbued into the nylon while the person was wearing it.

Jam:

Got it.

Melissa:

And they Found, yes. These are a good substitute for actual human skin.

Jam:

Nice. And then

Melissa:

we don't have to worry about c o two or body temperature. We're just able to look at only the odors. Right.

Jam:

You literally eliminate those 2, not just, like, by genetically modifying mosquitoes and not seek those things, but just by not having them present.

Melissa:

Yes.

Jam:

Nice.

Melissa:

So that's cool.

Jam:

That's really cool.

Melissa:

So they did all these tests to make sure this would work, and it did. And so then they began the trials. I said, Let the games begin. Yeah. So they had originally just 8 people wear the nylons and did, These tests to see which people are more attractive to mosquitoes and which ones were less attractive.

Jam:

Mhmm.

Melissa:

And then they found those people who are Consistently more attractive, and they pitted them all against each other to see if they consistently one was outperforming everyone. You know? There's a all these Graphs, all these statistics that I'm sure the visuals were really fun to make, where they're showing how they were all competing. You know? Like, oh, these 2 compared, and these compared to these 2 compared to the 2 that were the same, how they compared to each other to make sure the mosquitoes weren't going, you know, to Right.

Melissa:

One over the other, all this stuff. Yeah. Lots of graphs, lots of statistics. This was a dense paper.

Jam:

Mhmm.

Melissa:

I was like, wow. They did so much work for this 1 paper. Okay. So here's your chemistry lesson. K.

Melissa:

We have the molecules with different properties. We know organic molecules are present on our skin, the volatile organic compounds. We also know from previous work that and we mentioned this in one of the episodes, that we did before on mosquitoes. I think it was the very first one, maybe the second one, why mosquitoes bite some people more than others. Mhmm.

Melissa:

That that one of the volatile organic molecules was lactic acid.

Jam:

Oh, yeah.

Melissa:

And lactic acid has a functional group That is called a carboxylic acid. K. We talked about that all the way back then. But for those of you who maybe haven't listened to that episode, A carboxylic acid is a functional group, and a functional group is just this arrangement of atoms in a specific order that consistently interacts with other atoms in the same way.

Jam:

K.

Melissa:

So, if you're in an organic chemistry class, one of the very first things you do is learn these different functional groups and you have to memorize them. So or you have to submit them in your brain somehow that this is what a carboxylic acid looks like. This is what an amine looks like so that you can recognize these functional groups and how they'll likely interact with other atoms or other molecules when they are placed in a specific environment.

Jam:

Right.

Melissa:

So carboxylic acids was something that we already knew were likely a part of the volatile organic compounds that made up the odor of our skin that mosquitoes were attracted to based on previous studies.

Jam:

Okay.

Melissa:

So they were looking for what possibly could be on the skin, and they sort of specifically honed in on The carboxylic acids because they knew that was going to be probably important.

Jam:

Right.

Melissa:

So then what they did was this is amazing to me. So they took the order the odors of the the nylon, and they made They said they made a preparation. So they sort of went through some steps to make it easier to identify the molecules, basically. I think that's getting too in the weeds of this study. But they took the, essence of these people, and they did what's called chromatography.

Melissa:

They did gas chromatography. So while it was still in the odorous phase, they did a chromatography experiment. We've talked about chromatography before also. Uh-huh. My quintessential example is if you've ever done that experiment where you, like, take a black marker and you put it on a coffee filter and then dip that in water and let the water travel up, the colors will separate out.

Jam:

Right.

Melissa:

So organic molecules do the same thing based on their different properties. You have a bunch of organic molecules in the same place, you can separate them out based on their properties. So you Do the exact same thing you do with that coffee filter, and you can figure out all the different molecules that are present. Yeah. And sometimes they'll pair those chromatography experiments with, something else that can give you more information about the molecule.

Melissa:

So we have a gas chromatographer instrument that's separating out our molecules. And oftentimes, they'll put at the, quote, unquote end of that, another instrument that will give us more information.

Jam:

Uh-huh.

Melissa:

So in this case, they put a mass spectrometer. And what a mass spectrometer does is look at the mass of the molecule in different fragments. Like, it'll kinda break it up and look at all the different fragments, And you can interpret that data to get a good guess of what molecule likely you have there in that fragment.

Jam:

Okay.

Melissa:

So, Essentially, they took the odor of the people. They pre prepared it to put in the gas chromatographer. They injected it into the gas chromatographer. The gas chromatographer separated all the molecules out. And then at the end, the mass spectrometer looked at each of those molecules and try to identify what they likely were.

Jam:

Okay.

Melissa:

It's very complicated. But Mhmm. So the scientists also have to look at it and make their best guess about what it

Jam:

would be, like, with all the information they have. Okay.

Melissa:

So mass spectrometry is, very complicated. That was when I knew people who did it, and I was always impressed that they did that for their research because you just have to be really good at interpreting the data. And yeah. It's it's like a very I admire that a lot.

Jam:

Yeah. It sounds very hard. I mean, it all sounds hard to me,

Melissa:

but it

Jam:

definitely sounds really complicated.

Melissa:

Yes. Well, it it feels complicated to me. I bet people who do it are like, no. It's so simple, and they could explain it the way I explain organic chemistry things. You know?

Jam:

Right.

Melissa:

So, basically, what they did is they found they took these odors of humans and they compared the ones that were from the people who were more attractive to mosquitoes and less attractive to mosquitoes. Altogether, they found a 161 molecules present in the odors. Uh-huh. But when they they eliminated the ones that were present in the more more attractive versus less attractive groups, They found a list of 13 molecules that seem to be more present in the high attractive group than the low attractive

Jam:

Interesting.

Melissa:

And then because of the way the gas chromatography worked and the way that they use the mass spectrometer, They were only able to identify 3 of those. Okay. They were looking specifically at the carboxylic acids. So they were able to identify 3 different carboxylic acid molecules that were present in the high attractor group versus the low attractor group.

Jam:

Okay.

Melissa:

So they have now been able to narrow down and say, okay. These people have Thirteen molecules present in a higher abundance or maybe the other group doesn't have them at all than these low attractor Groups. Mhmm. So there are literally molecules in our skin or on our skin that become volatile organic compounds that are our odors that are present consistently in people who are more attractive to mosquitoes.

Jam:

Wow.

Melissa:

Yeah. Dang. And it's all about the acids.

Jam:

Wow.

Melissa:

Not the bass.

Jam:

Not about that bass.

Melissa:

Not about that bass, sadly. So isn't that cool?

Jam:

That is crazy.

Melissa:

So that's your little chemistry lesson is the background of the chromatography, the functional groups, what they're looking at.

Jam:

Okay.

Melissa:

And they find these 3 molecules that they were able to identify. The other 10 are very likely in the same family of molecules. Uh-huh. And they weren't able to, you know, for sure identify them based on the experiment.

Jam:

Okay.

Melissa:

So 13 molecules that are present on the people who are high attractive versus low attractive.

Jam:

Interesting.

Melissa:

But then they wanted to make sure that was right.

Jam:

Yeah.

Melissa:

So then they did another trial where they compared people round robin style.

Jam:

Uh-huh.

Melissa:

And they found the same findings, and that one, I think, had closer to, like, 50 different participants.

Jam:

Got it. Got it.

Melissa:

The other thing they found is the people who are high attractor In the initial study, stayed high attractor. And the people who are low attractors stayed low attractors. So it seems to indicate That if you are more attractive to mosquitoes barring some life event, you know, more or less attractive to mosquitoes, that's likely consistently true throughout your life or stays steadily true.

Jam:

Interesting.

Melissa:

Unless you're, you know, maybe you're drinking alcohol, you become more attractive, maybe you get pregnant, you more attractive or something like that.

Jam:

Right. I'm sure they're controlling for those things.

Melissa:

In this case. Yes. Case.

Jam:

Yeah. The, so They did some work to be able to get rid of the humans for a while by, like, you know, making sure that the odors from skin transferred to the nylons.

Melissa:

Right.

Jam:

They could do a bunch of tests. Mhmm. They found what they found with the, chromatography in the mass spectrometer.

Melissa:

Yes.

Jam:

Which Of these compounds, which of these molecules seem to be affecting this stuff? And then Right. Brought the same humans back in.

Melissa:

They brought the Same humans plus more and had them wear the nylons.

Jam:

Okay. So that they could see what we found In our nylons only, no humans testing, basically. No humans present testing.

Melissa:

Right.

Jam:

And if still being consistent, when we bring humans back in and see who the mosquitoes go toward.

Melissa:

So not quite. They still did the nylon test with a larger group of people because you can imagine how hard it would be to have, like, 50 humans trying to do trials all the time with them, how hard that'd be to schedule. So they had they brought their people back in that they did originally And more people is what I understood. Uh-huh. It's kind of scary to summarize someone else's work because I didn't do it.

Melissa:

This is what I understood from the paper. Right. So they brought the original people in plus had them wear Nylons again, did the testing again, and they found similar results in their, their analysis of the odor.

Jam:

Okay.

Melissa:

Of the high attractor people had these compounds that the low attractor people didn't have.

Jam:

Yeah.

Melissa:

But they also found that their original people kind of kept their positions of high attractor versus low attractor.

Jam:

Okay.

Melissa:

Got it. Found that there are there was a consistency in those people's, quote, unquote, attractiveness to mosquitoes.

Jam:

Right.

Melissa:

So they brought the people back and had them wear the nylons again and then did the same style of testing without the humans there to make sure that their findings were consistent. Sort of like, this is what we found. Now we're gonna bring a bigger study and see or a bigger group and see if that still holds True.

Jam:

Right. Right.

Melissa:

Just to, like, confirm what they found and make sure it's not just those few people that it it holds true even for a larger group of people. Okay.

Jam:

Cool.

Melissa:

So that was how they did the study. And so that's what they found. But Uh-huh. I wanna make sure that we talk about the correlation does not imply causation.

Jam:

Okay.

Melissa:

So we know that these acids are more present on the skin of people who Seem to be higher attractive to moly to mosquitoes. Uh-huh. So there are people who are high attracted to mosquitoes. So if you're one of those people, you probably have some of these molecules.

Jam:

Yeah.

Melissa:

And you and I, Jan, probably have less of them or Right. Very few of them.

Jam:

Right.

Melissa:

But there could be other factors at play in why those people are more attractive than others. Maybe those molecules show up for some third reason that we don't know about. Mhmm. So we don't wanna say, like, because you have more of these, you are more attracted to We don't know that for sure.

Jam:

Right.

Melissa:

The other thing is it's possible that, There may be some molecules present in our skin that's naturally repelling.

Jam:

Right.

Melissa:

And that's a lot more difficult To test what do we have something that's present that's repelling?

Jam:

Right.

Melissa:

We don't know. So that's hard to test, and it's really hard to recreate human odor because it's so complicated. I mean, they found a 161 molecules present. Yeah. On these people's odor.

Melissa:

Right? So Yeah. It's difficult to mimic that without using this kind of study.

Jam:

Yeah. Yeah. Seriously.

Melissa:

That I thought that was really interesting, and they even wrote about that. So in many papers, there'll be a section that they call limitations. Like, what are the limitations of this study? And in the limitations, they said it really is difficult to know if this is why they're high attracting or if there's something else going on, But it seems to have a really high correlation. Mhmm.

Melissa:

And, also, it's difficult to know if there's if there's something that's causing us to repel that other people don't have. Yeah. You can't mimic that synthetically. It's really complicated. So we can't draw definitive conclusions, but I was really excited because this means that there's fresh evidence that there is something that consistently makes people more attractive to mosquitoes or consistently correlates with people being more attractive to mosquitoes than being less attractive.

Melissa:

And

Jam:

Right.

Melissa:

Knowing that, we might be able to utilize that knowledge to develop new ways of repelling mosquitoes.

Jam:

Right. Right.

Melissa:

Is there something that could neutralize those odors? Or if there's something we can, you know, we could do to help with that specific finding, maybe There'll be new ways to repel mosquitoes.

Jam:

Yeah. Wow.

Melissa:

So I love this study. I know it's a little bit different than what we normally do, but I loved being able to share everything that goes into a research study and being able to share, You know, sort of we're on the journey with scientists as they're discovering things. Like, we've been on this journey all along. And this is a really big deal in the scientific community that not only have they, like, confirmed this consistency of attraction. Yeah.

Melissa:

But also there appears to be a class of molecules that's more highly present on some people's skin than others or in some people's odors than others, and those people are the ones who are consistently more attractive to mosquitoes.

Jam:

Yeah. Yeah. That is a big deal. That's like The kind of thing you could see them someone I mean, just me not knowing the first thing about how you'd even approach trying to figure this out.

Melissa:

Yeah.

Jam:

I could see trying for a long time to see I can prove something and coming up with You know what I mean? Yeah. It's like, okay. I did a bunch of stuff, and I still can't find some consistency.

Melissa:

That's different between these groups.

Jam:

Yep.

Melissa:

Right.

Jam:

Yeah. Or is it this person's different today and than, you know, one way or tomorrow.

Melissa:

Right. And that's what I was worried about. And it does seem like they that's why they brought their original people back in

Jam:

Yeah.

Melissa:

Is so that they can they could see okay. Was this sort of like a one off situation? But we'll bring the original people back into the final study.

Jam:

Yeah.

Melissa:

And we'll bring new people who who we don't know about for sure. So we'll see if this is consistent amongst a larger group. Is this But they call that is generalizable.

Jam:

Uh-huh.

Melissa:

Are these findings generalizable? Do they do these apply only to these 6 people that are or 8 people in this original study that are human beings to have these odors on this day? Or can we broaden this out and say, these people are consistently having this, and when we look at even more people, They're having this too.

Jam:

Right. Right.

Melissa:

So it's a big deal.

Jam:

Yeah. Seriously.

Melissa:

I'm really excited about it. So I don't know how you wanna try to explain that one back to me because it's a little bit more complicated.

Jam:

Yeah.

Melissa:

And I just summarized a whole 3 years of research in, you know, 20 minutes.

Jam:

Yeah.

Melissa:

But whatever your thoughts are on how Ought to sort of give a quick review. I'd love to hear it.

Jam:

Okay. So here's my thought.

Melissa:

Okay.

Jam:

I immediately thought about the fact that This has come up a bunch as I've just been a human living out in the world in conversation. Lots of these Topics that we that you pick to, like, for us to delve into, do that anyway because that's the whole point.

Melissa:

To pick

Jam:

every new life topics. But this one comes up so much, and I feel like There's a bunch of it's one of the several that I find myself having to try to recap people in real life. Yes. Sometimes I'd be like, just close the episode, dude, but You can tell, like, okay. Are they really going to?

Jam:

Maybe I'll give them the 5 minute version real quick. Whatever. So here's my thought. What if I try to give the Pedestrian walking around trying to correct someone's thinking or at least tell them about this new research.

Melissa:

Yeah.

Jam:

Real quickly, In a bite sized way that just gives them what they need to know that they can comprehend for a second before they tune me out because they're like, why are you Talking my ear off. Why are you penalizing me because I thought that it was

Melissa:

my blood type? You know? Just a quick I call that the elevator pitch. Nice. Like, I an elevator pitch of my research.

Melissa:

What can I tell you about my research and the timer on the elevator?

Jam:

Yeah. So so I think I'd start by just saying It's been known for a long time that there are several factors Mhmm. That attract mosquitoes to humans in the 1st place.

Melissa:

Yes.

Jam:

And any of those could maybe vary from person to person.

Melissa:

Yes.

Jam:

But there's a new study. They specifically honed in on the odors on our skin, Trying to figure out if there's differences from human to human

Melissa:

Yes.

Jam:

That could attract mosquitoes more or less, And if those differences between human to human wouldn't just be, like, in one specific situation, but consistent over time

Melissa:

Yes.

Jam:

With that specific human. And this new study was basically able to find that there are some specific, molecules Yep. Specific acids

Melissa:

Mhmm.

Jam:

In the odor of our skin, in the complex makeup of lots of different things in our Yeah. The odors of our skin, there were three things. Right? 3?

Melissa:

Well, it was 13, but they could only name for sure 3. They they think that there are probably others

Jam:

Right.

Melissa:

That are very similar. Like, they have a Suspicions about what they are, but I didn't wanna get into that.

Jam:

Yeah. So several. 3 they can name, but quite a few that seem to Attract mosquitoes more Yes. That are present in some people's skin odors Mhmm. That are not present or at least maybe less so in other people's Skin odor.

Melissa:

Yes.

Jam:

And they're able to do it and confirm it a few different ways and also find that Those the kinda makeup of people's skin odor does seem to stay similar

Melissa:

Yes. Across time. And I forgot to say, I went back and and reviewed something real quick, and I realized not only did they bring the original people back into the new round robin, but the new round robin, like, the 50 or See people that they had, they submitted their skin odors multiple times, like several times spread a week apart.

Jam:

Got it.

Melissa:

So they consistently saw that the high attractors were high attractors, and the low attractors were low attractors. So It does seem consistent. So the fact that we've consistently experienced other people getting bitten more than us Yes.

Jam:

Yep.

Melissa:

That's anecdotal, but this study backs that up.

Jam:

Yeah. Backs up that it is possible For any of us to have consistent level of attractiveness to mosquitoes

Melissa:

Right.

Jam:

Across our our life or whatever.

Melissa:

Yes.

Jam:

And Then I would so I'm still talking to some person who has given me the time of day. And So then what I would say too, because this is, like, the highlight of the whole thing, not just scientists discovered a cool thing or whatever, but it could be used As research continues to figure out new approaches to Repelling mosquitoes or neutralizing certain odors to make all people, especially people who have a high presence of those odors, be less attractive to mosquitoes than they currently are.

Melissa:

Yep.

Jam:

And it could really just inform a bunch of stuff going forward.

Melissa:

Yes.

Jam:

And it's one important building block in the Ever continuing fighting against mosquitoes.

Melissa:

Right. It's fun. I just think it's fun that, like, we've gotten to see the buildings Building blocks grow. Mhmm. You know?

Melissa:

I think that's really very cool. So

Jam:

The reason I thought about approaching it that way is because I was thinking, like, it on the chemistry lesson side, The chromatography and mass spectroscopy, obviously, important chemistry lessons, but things that, 1, I get less confident about explaining the further away from lesson we

Melissa:

get. Yeah.

Jam:

And 2, that the average person I'm talking to about it, Same with you, I'm sure.

Melissa:

Right.

Jam:

Is, like, that's the stuff that is a lot to figure out. Yes. And if you try to give them the couple minute version Yes. Easy to skip it and just say, Sciences did important things that is that helped them figure this out.

Melissa:

Yes. Yeah. Another thing you'll take with you is the scientific process behind this. So that was kinda more of why I wanted to do this study. I also, of course, love the opportunity to talk about chemistry.

Melissa:

And these are molecules, and so it's all chemistry, but we haven't talked a lot about literally how does science happen. And so this seemed like a good opportunity connected to something a lot of people care about that we've talked about before that we get a new update. I mean, this literally just came out in The I think it was October of 2022. Let's see. Yes.

Melissa:

October 18, 2022 is when the chemistry and engineering news did an article on it, and Nature did an an article on it, and, actually, even the article itself was published in October of 2022. So this is, like, Hot off the press.

Jam:

Yeah. So you're saying

Melissa:

information that we're getting while we've been on this saga for how mosquitoes Like some people more

Jam:

than me. Dang.

Melissa:

Very exciting.

Jam:

Seriously. Yeah. That's it's weird because, obviously, there's a lot of things that you've referenced that are relatively recent. And even sometimes it's like, oh, this is this study is, like, maybe 10 years old. There's nothing new newer that has a different take.

Jam:

Yeah. So it's like, this is still accepted. Like, this is still the most recent good stuff about this or whatever.

Melissa:

But this is last month.

Jam:

Yeah. That's insane.

Melissa:

I'm very excited. And I I was really excited when I found that this person had a Twitter so that we could And she has a whole thread where she talked about her experience doing the study. So you can also go read it directly from her, the scientist who can Conducted the study from her view as well.

Jam:

Nice. Nice.

Melissa:

So that was fun. And speaking of fun things, Jam, do you have anything fun that you wanna share about this That happened to you in the last week or so?

Jam:

I do. I, well, sorry about this, but I had the fun opportunity to a wedding of a friend of ours Oh,

Melissa:

yeah.

Jam:

Who's also an avid chemistry for your life listener.

Melissa:

Who designed the Kim heads.

Jam:

Mhmm.

Melissa:

He is

Jam:

on the Kim heads and designed our exclusive tier 2 and 3 patron sticker?

Melissa:

Yeah. Oh, that we're gonna mail out soon.

Jam:

Mhmm. So, anyway, he's he's really cool. He's a good friend of mine. I've done him for, I think, almost, like, 9 Years or something like

Melissa:

that? Long time. Yeah.

Jam:

So that was really a fun experience. It was great to get to hang out with him, and I'm happy for them. And I'm, Obviously, just was on into it to be a little bit of a part of it. And and I got to go together, which was fun. I can't I don't think we've been able to go to a wedding together in maybe, like, a year Yeah.

Melissa:

Like that.

Jam:

So, anyway, that's my thing.

Melissa:

Oh, that's so exciting. He's so nice, so I'm really glad he is doing something that's making him happy and also that you got to be a part of it. Because, you did a great job officiating my I think

Jam:

so. Yeah. He joined the ranks of somewhat commission for your life connected Yeah. Wedding officiating Going on, which is a very niche group.

Melissa:

Yeah. A knee very niche group for sure. Too bad he didn't also get married on the same anniversary that you and I share.

Jam:

Yep. That's true.

Melissa:

Do people know that Oh, we should we have the same wedding anniversary. I wonder

Jam:

if you mentioned that or not. But yeah. So it's yeah. You guys got married, I guess, what was that? 7 years After Mhmm.

Jam:

Yeah.

Melissa:

Several years after.

Jam:

But the same day. Yeah.

Melissa:

Well, my fun thing is totally different. I, I, got to go visit where I work now. I'm a postdoc, but I work remotely. So I got to go to Auburn.

Jam:

Nice.

Melissa:

And it was so beautiful. There were so many trees, and it was really special to get to connect with the people I work with in that way.

Jam:

Yeah.

Melissa:

I mean, I love working remotely. I think that's definitely the best thing for me and my family. And I think there's definitely a trend of People who don't have to do in person work, like, for instrumentation or something specific like that, there's a trend that those people should be able to do their stock remotely because many people who have their PhDs are starting families who, like, are just finishing. They're starting families. Yeah.

Melissa:

They're married. Their partner has as a position, their partner's still in grad school. I mean, there's so many situations where it does not make sense to move your family for a 1 to 2 year position.

Jam:

Right. Right. Yeah.

Melissa:

But Not everybody has that opportunity, but I'm really thankful that my boss allowed me to do that. He's so he's really understanding of it because he was in a similar situation as well. But Uh-huh. It wasn't it's just different to get to, you know, share meals and to be able to turn around and ask a question in the lab, and and you just connect a different way. And so that was really special.

Melissa:

Yeah. And, I got to one of my the grad students that works with me, one of my coworkers, She, made me food from Ghana because that's where she's from. Uh-huh. And then another one of the grad students is from China, and so we went out to have Chinese food together. And then she sent me home with a bunch of hot pot because I love hot pot.

Melissa:

So all these spices to make the soup, so I'm really excited. We need to buy one of those little, like, hot pot

Jam:

Oh, yeah.

Melissa:

Plates. You know? Uh-huh. So I'm really excited to, get to do that. But, as I love sharing food with people because it feels like just a way to connect.

Melissa:

You know?

Jam:

Yes. Yes.

Melissa:

So it was a really great time. I really enjoyed it, and I think it really helps in, like, the ease of workflow and connecting with people. So Yeah. And it was folly there. It wasn't when I first got there, but when I left, the trees had started to turn.

Melissa:

Everyone who lived there was like, oh, yeah. We don't get fall, but The stark difference between there and here. When I landed here and drove home, there is no fall trees.

Jam:

Yeah. Yeah.

Melissa:

So even now, most of what I'm seeing outside Side of Jam's window is green.

Jam:

Yeah. That's true.

Melissa:

Very true. It was nice. It was a good trip.

Jam:

That's awesome. Very cool.

Melissa:

So thanks to my boss for letting me do that. That was a really special trip. Thanks also to mister Hall's for suggesting this episode and to the team of people who conducted this research at the Vassal Lab. And thanks to Jam and to all of our listeners for coming and learning about This most recent research about mosquitoes.

Jam:

And thank you, Melissa, for teaching us, for Diving into this new paper that mister Hollis sent us and for helping explain it so we can understand it. Wilson, I have a lot of ideas for topics of chemistry in everyday life, but we want to hear from you. So if you have question or ideas, you can reach out to us on our new website atchem for your life.com. That's chem, for your life.com to share your thoughts and ideas. If you'd like to help us keep our show going and contribute to cover the cost of making it, you can go to patreon.com Slash Kim for your life or tap the link in our show notes to join our super cool community of patrons.

Jam:

If you aren't able to do that, can help us by subscribing on your favorite podcast app and rating and writing our review on Apple Podcasts. That also helps us to share chemistry with even more people.

Melissa:

This episode of Chemistry For Your Life was created by Melissa Coleenie and Jam Robinson. Jam Robinson is our producer, And this episode was made possible by our financial supporters over on Patreon. It means so much to us that you want to help make chemistry accessible to even more people. Those supporters are Nicole c, Timothy p, Brie m, Chris and Claire s, Hunter r, Steven b, Avishai B, Chelsea B, Christina G, Emerson W, Shadow, Brian K, Suzanne S, and Jacob T. Thanks again for everything you do to make chemistry for your life happen.

Jam:

We also have to give a special thanks To a Calini who reviewed this episode. If you'd like to learn more about today's chemistry lesson, check out the references for this episode in our show notes or on our website.

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