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You're listening to Shortwave from NPR. Hey, Shortwaver.
Yes, you. Did you get enough sleep last night?
Have you had enough water this morning? And very importantly, did you put on your sunscreen?
This is the checklist that runs through my mind every morning. every day I put on sunscreen on my face if I'm planning to leave the house at all.
Michelle Wong has a PhD in chemistry, and for her, sunscreen is non-negotiable.
She has a YouTube channel, Lab Muffin Beauty Science, where she explains the science behind beauty products, which in her book includes sunscreens.
SPF stands for Sun Protection Factor Write down the reasons why you may or may not need a sunscreen indoors from a scientific perspective Sunburn starts when the DNA inside your skin cells absorb UV radiation.
And what I've learned from Michelle is that UV radiation comes in two flavors.
UVA and UVB, both of which you need to protect your skin from.
B is shorter wavelength, higher energy. UVA is longer wavelength, lower energy.
It goes a little bit deeper into skin. UVB is more superficial and it's more linked to burning, but both of them are linked to increased skin cancer and increased premature skin ageing.
But the science didn't always indicate that UVA was bad for us.
But in the last decade or so, that's changed.
And in a lot of the world, sunscreen formulas have been updated to reflect that.
Places like the EU now make broad-spectrum sunscreens that protect against UVB and UVA.
But in the US, UVA protection is limited.
The US has a more limited set of UV filters available.
It has been over 20 years since there was a new sunscreen ingredient approved in the US.
Today on the show, the U.S. sunscreen hangup.
Why sunscreens in the U.S. may not be offering as much sun protection as ones sold in other countries. even if they're labeled broad spectrum.
I'm Regina Barber, and you're listening to Shortwave, the science podcast from NPR.
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Okay, Michelle, so one big reason sunscreens differ so much in the U.S. compared to other countries has to do with like how we categorize the sunscreen.
So what is that difference? Yeah, so in most places, it's categorized as a cosmetic or a special cosmetic.
But in the US and Australia, it's a drug, which means that the way it's produced is going to be held to a high standard.
It's going to be more consistent. There's more rules on how it can be produced, what ingredients can go into it.
The ingredients need to be tested for things like safety and and you are getting a guaranteed efficacy.
So this means that it's going to take longer to change in the U.S. because it's going to go through those drug approvals and everything.
Yeah, exactly. So in the US with any new drug ingredient, there's a huge process that needs to be going through.
It's got to go through a whole bunch of safety approvals.
And in the US, there's also a requirement for animal testing for these approvals.
Okay. And that's generally the biggest sticking point.
But that process can change. So in Australia, sunscreen is also a drug and we get the newer sunscreen ingredients. pretty quickly after the rest of the world, even though it is still technically a drug.
And that's because drug approval processes aren't the same everywhere.
So like you said, okay, it's been decades since the US sunscreen has been updated.
They tend to focus on protecting against UVB rays, but...
Like since then, there has been research that maybe we should also be protected from UVA rays.
So why is that important? Yeah, so even though UVA is lower energy and... it does seem to cause less damage in pretty much every respect.
It does still cause damage. So there's research showing that it definitely contributes to melanoma.
There's a lot of research, especially on suntanning beds, which only put out UVA
Most of them put out only UVA. Some of them put out a combination of UVA and B.
And that's because in the past it was thought that UVA was less damaging and maybe not damaging at all.
And so people could get tanner without getting burnt and that associated skin damage.
But later on, it was found that tanning beds definitely contribute to melanoma.
There's a statistic which is tanning beds are more strongly connected to skin cancer than smoking is to lung cancer.
What? Oh my gosh. Wow. Okay, so let's talk about what broad spectrum... protection actually means then?
So like in the U S I use Olay like every, every day it says UVA and UVB, um, protection, but what does that actually mean?
Like you said, The regulation for calling something broad spectrum is very different in the U.S. versus other countries.
Yeah, so there's two criteria for calling a sunscreen broad spectrum.
One of them is... one tenth of the UV absorbed needs to be longer wavelength than 370 nanometers.
So that means the sunscreen needs to have a decent amount of protection at the really long UVA wavelengths that are so long they are almost violet.
Basically, this is just to make sure the sunscreen does give decent protection against a broad range of wavelengths and not just the shorter ones, which was what was traditionally protected against with a sunscreen, the ones that are more linked to sunburn.
Now, the second criteria is that the UVA protection needs to be at least one third of the SPF.
Really? Yeah. So in the US... They only need that 370 nanometer criteria.
That's called the critical wavelength. But in Australia, the EU, the rest of the world, you need that plus you need that one third SPF rating.
I remember reading after like SBF 30, you don't really need it.
What do you have to say about like the different levels?
Do they actually protect way more or is it negligible?
So in theory, if you do the calculation, an SPF 30, if you apply it properly at two milligrams per square centimeter on your skin, that's going to only let through one thirtieth of the UV coming in.
So if you have an SPF 60, then that's going to only let in 1 60th.
Now, Basically, SPF 30 will let in twice as much UV as SPF 60.
Now, if you convert that to a percentage, that's going to be really tiny, like 1 30th is 3%.
So it's like a tiny amount coming in, but that only works if you're applying it perfectly with a massive amount, which most people don't.
Got it. So the higher the SPF, the better it is if you don't apply enough.
If you apply perfectly, then... Pretty much SPF 30 and above, it's going to be pretty equal.
You're good to go. Okay. Let's dive into the chemistry.
Let's dive into your expertise. What kind of ingredients are like... we talking about in non-US countries that are allowed in sunscreen versus like what we have here?
In the US, there's only about... I think, eight commonly used UV filters.
So there's two that are classified as, I guess, physical or mineral.
There's zinc oxide and titanium dioxide.
They're allowed pretty much everywhere around the world.
The other type are called chemical, I guess in quotation marks because everything is a chemical.
And these ones are carbon-based. They tend to be molecules that have lots and lots of benzene rings. so they can absorb UV.
The structures look very similar to what we see in, like, dyes, so dyes that dye clothes.
Oh, cool. Except... Dyes will be absorbing visible light.
These ones are tailored to absorb UV. And there are tons of these, but there's only a handful allowed in the US, which are a bit older, and they tend to absorb more of those shorter wavelengths against burning.
The newer ones tend to absorb more of the longer wavelengths going into UVA, getting closer to visible.
And yeah, those are the ones that aren't allowed in the US.
Yeah. So the FDA hasn't approved these new ingredients.
And when people hear that, maybe they think they aren't safe.
Can you talk about how researchers think about safe versus not safe? with these new filters?
Yeah. So these new ingredients are purposely designed so that they are meant to be inherently safer.
And what that means is they have a larger structure, they have particular chemical properties that make them less likely to go through skin. and cause any sort of systemic whole body effect.
The other way of testing safety is trying to see how much goes into the body, where it ends up interacting with the body, what sorts of effects it might have.
And there's a lot of ways of doing this.
The traditional way was by doing animal testing.
So you put a whole bunch of sunscreen on rats or on mice.
But there are newer methods where instead of just putting as much as you can on an animal until something happens, You can test on things like cells, receptors.
There are things like what are called organs on chips.
And from that, you can work out what's safe, kind of replacing these animal studies, which I mean, scientists are always trying to replace them because they're expensive and they're not as ethical as some other alternatives.
But at the moment, the FDA still requires the animal studies, which has been the big hurdle with getting these approved because... in places like Europe, animal testing is banned for cosmetics and because sunscreen happens to be a cosmetic in Europe,
That's been the big stumbling block. Do you have any idea when or hope when it might have an update to the list of new ingredients for sunscreens in the U.S.?
? I try to have hope, but at the same time, I have been hoping for this for the last 15 years or so.
And there's always been predictions about when it's going to happen.
Like it's going to be next year. It's going to be next year.
So in theory, it might be next year. But in reality, I guess we'll see.
Are there any ingredients that are bad or dangerous to look out for in any sunscreens in the world?
Not really. I guess the biggest risk is always with uncontrolled impurities, but in any well regulated marketplace, sunscreen should be one of the safest things that you can put on your skin.
I guess the other big thing is really looking at the instructions and making sure you follow the instructions.
I think most people generally do less than the instructions.
Most people put on less sunscreen than they should.
But as long as you're not putting on a ridiculous amount of sunscreen or eating it or inhaling a lot, then it's generally one of the best tested skincare ingredients you'll ever put on your skin.
Recently on social media, I've seen younger people have a lot of fear about sunscreen and like, question its effectiveness how do you as somebody who is on YouTube who is a science communicator how do you respond to that?
I'd say if you look at all the people freaking out about sunscreen safety, a lot of the time when they're talking to you, they're referring to animal studies.
But then if you look at the things that are positive about sunscreen, it's always in people.
Like there's been a clinical trial that's found that sunscreen has halved the risk of several types of skin cancers.
It completely halted skin aging for the period of the trial.
And then you see case studies like, you know, 92 year old woman has been wearing sunscreen for 60 years and her face looks really good, but her neck where she didn't apply sunscreen is a lot more aged.
So I think that really demonstrates that a lot of the risks of sunscreen, the safety issues, those are mostly theoretical and the advantages are actually... things that you see in humans.
There's never really been someone who's had a massive health effect because of sunscreen, apart from things like allergic reactions.
While we in the US are waiting for maybe sunscreen to be updated, how can people protect themselves?
I mean, the older sunscreen still work very well.
The main thing is not applying enough. The proper amount is you should be putting one teaspoon on each limb, one teaspoon for the front of your body, one teaspoon for the back of your body, and one teaspoon for your head plus neck plus ears.
For your face alone, it should be a quarter teaspoon.
You also want to reapply. Generally, the recommendation is every two hours.
And also after you go in the water or if you towel off after swimming, that's another big, big issue.
Also don't let it heat up massively. If it does, then you should probably buy a new sunscreen or if you leave it in the hot car.
Yeah, that's one of the biggest things. Mmm.
And the other thing, in terms of protecting your skin from the sun, sunscreen is one of the most fiddly, error-prone options. we just don't apply enough, we have to reapply.
You don't have to worry about that if you're putting on, let's say, a UV protective shirt or a hat.
I think at the end of the day, the best sunscreen you can wear is the one that you enjoy, one that you can apply a lot of regularly.
Michelle, thank you so much for talking to us today.
Thank you for having me. This episode was produced by Burleigh McCoy, edited by showrunner Rebecca Ramirez, and fact-checked by Tyler Jones.
Jay Ciz was the audio engineer. Beth Donovan is our senior director.
And Colin Campbell is our senior vice president of podcasting strategy.
I'm Regina Barber. Thank you for listening to Shortwave from NPR.
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And we will pull back the curtain on what they're thinking on Sources and Methods, NPR's new national security podcast.
Our team will help you understand America's shifting role in the world.
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