08/02/2019

Is Chemical Sunscreen Safe? Scientists Aren’t Sure

16:46 minutes

three women sitting lined up putting sunscreen on each other's backs
Credit: Shutterstock

Sunscreen has been on the shelves of drugstores since the mid-1940s. And while new kinds of sunscreens have come out, some of the active ingredients in them have yet to be determined as safe and effective. A recent study conducted by the FDA showed that the active ingredients of four commercially available sunscreens were absorbed into the bloodstream—even days after a person stops using it.

Ira talks to Kanade Shinkai, a professor of dermatology at UCSF and editor in chief of the Journal of the American Medical Association Dermatology, about what the next steps are for sunscreen testing and what consumers should do in the meantime.

We asked Shinkai to explain the difference between the two major sunblock options—and what has been tested and not tested. Her responses have been lightly edited.

What are the two major sunblock options?
There are two types of sunscreen: Mineral sunscreen (like zinc oxide, which doesn’t absorb into your skin)—and chemical sunscreen (the common lotion kind which your skin does absorb).

How does mineral sunscreen work—and is it safe?
Mineral sunscreens reflect photons of ultraviolet light from the skin. There are two commonly used forms: zinc oxide and titanium dioxide. When they are used together in a sunscreen formulation, they provide excellent protection of the skin, covering most of the UV A and UV B spectrum. Their ingredients are not absorbed through the skin and they have been tested and deemed safe, or GRASE (Generally Regarded As Safe and Effective) by the FDA.

And what about skin-absorptive chemical sunscreens?
Chemical sunscreens include chemical molecules that absorb UV A, UV B, or both. Examples include oxybenzone, avobenzone, octocrylene, and ecamsule—the four sunscreen ingredients studied in the JAMA research study (and are common in most sunscreens). Because these sun-filtering chemicals often only cover small portions of the UV spectrum, manufacturers use a combination of the different chemicals to provide broad spectrum UV coverage needed to protect skin.

The FDA recently announced that there is insufficient evidence available to designate these four chemicals and eight others as GRASE.

Does chemical sunscreen use impact health?
What we know right now is that these four sunscreen chemicals are absorbed into the bloodstream, [at more than the accepted limit, so they are required] to undergo safety testing, specifically to look at cancer risk and whether that medication has any impact on reproduction and other biological functions. What we don’t know, and this is so important for listeners to understand, is if they have any human harm in terms of health impacts. So, the first important issue is that we need to do these studies. Either the sunscreen industry needs to do them or medicine needs to do them. That’s really the first and foremost point I wanted to make. 

Why has sunscreen not been tested for health impacts yet?
Sunscreen isn’t just a cosmetic here in the U.S., it’s a medication. Sunscreens were initially approved as medications many, many decades ago, before a lot of modern-era drug regulations really took place. It’s really now, in more recent years, that we have clear standards for how all over-the-counter medications are tested. But that retesting [for chemical sunscreen] never happened.

So are sunscreen manufacturers required to go out and do these tests?
That’s correct. There’s a proposal that’s been put forth by the FDA that they would like this to happen before November of 2019. However, this conversation has been going on for decades. The FDA has regulated sunscreens since the 1970s. And in the late 1990s, the FDA asked sunscreen manufacturers to provide the safety data about systemic absorption. And for many years, they’ve gone back and forth, and for various reasons, they have not seen the results yet. 

What are some sunscreen alternatives?
[I] love the idea of covering up. It’s very important for people to wear protective clothing. That includes hats, sunglasses, long-sleeved shirts, long pants when outdoors, and then to use sunscreen on the areas that are exposed. People have a lot of control over when they do their exercise, for example, avoiding direct sun during the peak hours of the sun, which are defined as 10:00 AM to 2:00 PM, and seeking shade when possible. 

There still are sunscreens that we know are safe. These are the mineral sunscreens that I mentioned earlier, the titanium dioxide and zinc oxide. Those are widely available throughout the U.S. and have been tested and deemed safe. So, those are a great option for people who have any concerns about chemical sunscreens. 

What does SPF mean and what’s a good number to aim for?
If you’re likely to burn within a certain amount of time, SPF 2 would allow you to be under direct sun exposure for twice the length of your normal burn rate. Obviously, that’s going to be different for every individual who uses sunscreen. But the recommendation is that SPF 30 is a good thing to shoot for when you’re purchasing sunscreen because that works for most people and essentially blocks almost 95% to 97% of all the UV that you’re being exposed to. 

How thickly should I apply sunscreen?
We do know from many scientific studies that in real-world use, many users don’t apply sunscreen thick enough. And if you don’t apply sunscreen adequately, you’re actually getting less SPF protection because you’re just dosing yourself with less of the medication. So one of the purposes of [getting] an SPF that’s 50 or higher can be that if you use half the amount, you’re essentially getting the right amount, right? 

For the average-sized adult, the recommendation is to use one ounce, or a shot glass, if that helps [you] visualize how much sunscreen that would be. And most sunscreens that we purchase in a store would be about four ounces. 

So if you can imagine an adult going out to the beach, and they’re going to apply the medication to their entire body, and they’re going to put it on four times a day, which is what it says on the sunscreen label, that bottle is going to go pretty quickly. It’s going to be pretty much used up within a day or two. And as we probably all would admit, that usually doesn’t happen. So all of us are probably not using enough. 


Plus, listen to what Science Friday listeners had to say about what they’ve heard about sunscreen recommendations. You can join the conversation on the Science Friday Voxpop app, available for Android and iPhone.

Transcript: Richard: I’ve been told by dermatologist to use it, use it, use it. I try to use it but I don’t use it that often. I try to just stay covered up as much as I can. Andrew: Recently, I read an article suggesting that sunscreen doesn’t actually block the cancer-causing UV but it does block the UV that causes you to get sunburned. Bill: My understanding is that you need both UV A and UV B protection, probably at least SPF 30 or greater. Although, I’ve been told that anything above that probably doesn’t offer you that much more protection, it’s just hype.


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Segment Guests

Kanade Shinkai

Kanade Shinkai is a professor of Dermatology at the University of California San Francisco and the Editor in Chief of JAMA Dermatology, in San Francisco, California.

Segment Transcript

IRA FLATOW: This is Science Friday. I’m Ira Flatow. It is summertime. It is a time when doctors have been telling us to wear sunscreen. They’ve been telling us to do this for decades now, right? 

And for good reason, melanoma is one of the most dangerous forms of cancer. And while some of us might slather or spray it on before a day at the beach, others are even more diligent and use a little bit of sunscreen every day. We asked you to tell us on the Science Friday VoxPop app what you’ve been told about sunscreen and how you use it. 

RICHARD: I’ve been told by my dermatologist to use it, use it, use it. I’ve tried to use it, but I don’t use it that often. I try and just stay covered up as much as I can. 

ANDREW: Recently, I read an article suggesting that sunscreen doesn’t actually block the cancer-causing UV, but it does block the UV that causes you to get sunburned. 

BILL: My understanding is that you need both UVA and UVB protection, probably at least SPF 30 or greater, although I’ve been told that anything above that probably doesn’t offer you that much more protection, it’s just hype. 

IRA FLATOW: Well, we’re going to talk about that. And those were listeners, Richard in Wisconsin, Andrew in New Zealand, Bill in Oregon on the Science Friday VoxPop app. So I’m asking you, now again, what have you been told about sunscreen? Do you use it? 

Download the Science Friday VoxPop app and leave us a little voice message there, like they did, to let us know. And also, you can call us now at 844-724-8255. 844-724-(SCI)-TALK. Or, of course, you can tweet us @scifri. 

One thing that we’re probably all been told is that sunscreen can prevent sunburn, even skin cancer. But listen to this, a recent study conducted by the FDA put sunscreen safety in question. My next guest was not part of the FDA study, but is here to discuss what we need to know in light of it. 

Kanade Shinkai is a professor of dermatology and the editor-in-chief of the Journal of the American Medical Association Dermatology. Just to note, we did reach out to the FDA for this segment, but they said no one was available to join us today. Welcome to Science Friday, Dr. Shinkai. 

KANADE SHINKAI: Thank you so much for having me on the show. 

IRA FLATOW: That’s great. We know that we should use sunscreen, but exactly how does it protect our skin from the sun? 

KANADE SHINKAI: Well, sunscreen is used for two purposes. The first is to prevent sunburn. And the second is to prevent skin cancer when you are exposed. There’s really two types of sunscreens. And I think consumers have noticed this when they go shopping to look for purchasing a sunscreen. 

The first type is mineral sunscreen. These are literally minerals, things like titanium dioxide and zinc oxide. They coat the skin, and that causes reflection or refraction of ultraviolet rays, so they literally bounce off the skin surface and are blocked from entering the skin. 

The second type are chemical sunscreens. These are chemical filters that are used typically in combination with each other to provide a broad spectrum, or meaning coverage over the UVA and UVA spectrum. And these absorb ultraviolet light. 

IRA FLATOW: Now, the FDA tested four chemical sunscreens that are sold in stores today. Now, what did they see? 

KANADE SHINKAI: Well, they used four commercially available formulations of sunscreen and applied them on a small number of human subjects. There were four groups of six in the study. And these are subjects that were kept in a climate-controlled environment and were asked to apply the medication four times a day to 75% of body surface area, so akin to what you would do if you followed the sunscreen label and perhaps were at the beach. So you’re basically covering all the exposed areas of skin. 

And then what they proceeded to do was to measure the blood levels of the specific sunscreen ingredients. They looked at four ingredients– oxybenzone, octocrylene, ecamsule, and avobenzone– and looked at how the body absorbed these sunscreens over time. 

And the medications were applied four times a day for four days. And what was striking about the study was they saw systemic absorption as early as day one. And they saw absorption that persisted into day seven, so three days after the sunscreen application had stopped, for all of the four sunscreens that were tested. 

IRA FLATOW: And those are the chemical sunscreens, right, not the mineral sunscreens? 

KANADE SHINKAI: That’s correct. These are all four chemical sunscreens. 

IRA FLATOW: Do the mineral ones work differently? I mean, do they get absorbed into the bloodstream like the chemical ones? 

KANADE SHINKAI: That has been tested, and the answer is clearly no. So titanium dioxide and zinc oxide are not absorbed into the bloodstream. 

IRA FLATOW: Now, did the FDA say there was any reason to give up sunscreens, these chemical ones, after they were found in increasing levels in the bloodstream and above FDA limits, correct? 

KANADE SHINKAI: That’s right. So what’s striking about the study is that the levels of sunscreen that were detected in the subjects’ bloodstreams exceeds a level that has been set by the Food and Drug Administration to be a threshold for testing, and that testing is 0.5 nanograms per milliliter of blood. 

And what that threshold is is that any medication that’s sold in the US, an over-the-counter medication, no matter how it’s ingested or taken, if it exceeds that threshold, it needs to undergo a safety testing, specifically to look at cancer risk and whether that medication has any impact on reproduction and other biological functions. 

IRA FLATOW: Well, now that it has exceeded that threshold, is the FDA going to test these substances? 

KANADE SHINKAI: Well, it’s important to recognize the Food and Drug Administration is not a testing agency. They’re a regulatory agency. So their role, in human medicine or in health, is to really set the standard for how things should be examined. 

It’s really up to the drug makers to provide the evidence that all of these tests have been done. So the first test is whether or not it’s absorbed and whether it exceeds that threshold that we just talked about. And then the second, if it is absorbed, the drug manufacturers are obligated to provide standard testing results, things like the cancer risk and reproductive harm. 

IRA FLATOW: So are they required now to go out and do these tests? 

KANADE SHINKAI: That’s correct. And in fact, there’s a proposal that’s been put forth by the Food and Drug Administration that they would like this to happen before November of 2019, so that’s soon, in just a couple of months. However, this conversation has been going on for decades. 

So the Food and Drug Administration has regulated sunscreens since the 1970s. And in the late 1990s, the Food and Drug Administration asked sunscreen manufacturers to provide the safety data about systemic absorption. And for many years, they’ve gone back and forth, and for various reasons, they have not seen the results yet. 

IRA FLATOW: So this has been a dance that’s going on for decades? 

KANADE SHINKAI: That’s right. It really has to do with, really, it gets at the heart of how over-the-counter medications are regulated in the US. I’m not an FDA member. I’m not a drug regulatory expert. But my understanding is that all over-the-counter medications are regulated by the Food and Drug Administration, so that’s important to recognize. 

Sunscreen isn’t just a cosmetic here in the US, it’s a medication. And that’s different. In other countries, sunscreen is sold as a cosmetic agent, so it does undergo different testing outside of the US. But in the US, it’s considered a medication and, therefore, it does have to fall under all the same regulations that other medications that we take do here in the US. 

But that retesting has never happened. And it has a lot to do with the fact that sunscreens were initially approved as medications many, many decades ago, before a lot of this modern era of drug regulation really took place. It’s really now, in more recent years, that we have clear standards for how all over-the-counter medications are tested. 

IRA FLATOW: I’m just going to assume that we should assume that what is past is also going to be happening in the future, that we’re not going to get these tests. Why suddenly should we be getting these tests? And if we’re not getting these tests, what do you, as a dermatologist, recommend that people do about themselves and their kids? 

KANADE SHINKAI: Well, what we know right now is that these four, at least these four chemical sunscreens that were studied in this particular research article, are absorbed into the bloodstream. What we don’t know, and this is so important for listeners to understand, is that we don’t know if they have any human harm in terms of health impacts or health effects. 

So the first really important issue is that we need to do these studies. Either the sunscreen industry needs to do them or medicine needs to do them. And that’s really the first and foremost point I wanted to make. 

The second is for listeners to recognize that there’s many different forms of what we call sun protection, or many different steps of how we protect ourselves from the sun, and sunscreen is just one of them. It’s very important for people to wear protective clothing. That includes hats, sunglasses, long-sleeved shirts, long pants when we’re outdoors when possible, and then to use sunscreen on the areas that are exposed. 

People have a lot of control over when they do their exercise, for example, avoiding direct sun during the peak hours of the sun, which are defined as 10:00 AM to 2:00 PM in the afternoon, and seeking shade when possible. So these are all parts of a sun protection regimen that people can participate in. 

The other is that there still are sunscreens that we know are safe. These are the mineral sunscreens that I mentioned earlier, the titanium dioxide and the zinc oxide. Those are widely available throughout the US and make up a good portion of the sunscreens that are available here in the US and have been tested and deemed safe. So those are a great option for people who have any concerns about the chemical sunscreens. 

IRA FLATOW: What about bringing in sunscreens from other countries? If you’re in Great Britain or wherever, you, can you just go into Boots or someplace and stock up on them? 

KANADE SHINKAI: That’s absolutely right. For those who are lucky enough to travel outside the US, they’ve probably noticed that when they try to purchase sunscreen in a different country that the sunscreen agents that are available there are very different from those that are available here in the US. We’ve really had kind of a standstill in terms of new sunscreen filters being approved by the Food and Drug Administration in the US. 

And it wasn’t until 2014, under President Obama, that there was a Sunscreen Innovation Act, which really put forth a roadmap for how new sunscreen ingredients would be approved into the US while being regulated. There are many different agents out there in sunscreen ingredients that are available worldwide. That is definitely one option. 

We also don’t know a lot about the testing on those because, as I mentioned before, they are regulated as cosmetics elsewhere. So I think it’s really going to set forth a big self-reflection of the sunscreen industry in terms of thinking about how we should be testing these things, how we should be regulating them. And these are all really important questions that have been raised by the current study. 

IRA FLATOW: See if we can get a few phone calls in because, of course, everybody’s concerned. Michael, in Fayetteville, Arkansas. Hi. 

MICHAEL: Hello. 

IRA FLATOW: Go for it. 

MICHAEL: Hey, yeah. About 10 years ago, I got a sunspot on my neck. I think it came back twice. The doctor told me definitely wear sunscreen. I work outside. I wear sunscreen. I put it on at least three times a day. I mean, I lather it on like crazy. 

I’m concerned that that’s not enough. The guest there kind of answered my question. But if it’s just a sunscreen and not going to protect me from cancer, should I be– it’s hot down here in Arkansas, but I’ve considered wearing long sleeves and just completely covering my body– is that the best option if I do have concerns about cancer? I do have a father and grandmother that have had cancer spots removed from their forehead and neck. 

IRA FLATOW: OK. Good question. Covering up, as you say, even though it’s hot– 

KANADE SHINKAI: That’s right– 

IRA FLATOW: –may be the better thing to do. 

KANADE SHINKAI: Well, covering up is definitely an option. And we’re lucky to have so many different ways of doing that. I think the fashion around it has also improved. There’s much more fashionable sun clothing available, and it’s widely available at really common stores, not just the sports stores. So I definitely encourage people to do that. 

You mentioned the spot on your neck, and there are things, they’re called neck buffs, they’re like scarves, but not made out of wool that we wear in the winter, but they’re made out of different types of lighter, breathable materials that can cover the neck and will really allow you to be able to work outside and under hot conditions. And I really liked what your caller said about reapplying. 

What we don’t know from this study, as I mentioned, the study showed people who were kept in a more climate-controlled environment, but what we don’t know is how much of sunscreen is absorbed in real-world conditions, for example, when we are working outside, when we’re sweating, when we’re swimming, doing exercise. 

We don’t know whether that systemic absorption would go up or down relative to those research subjects that were studied in this article. So definitely love the idea of covering up. I love the idea of reapplying the sunscreen, especially if you’re working and sweating. 

IRA FLATOW: I’m Ira Flatow. This is Science Friday from WNYC Studios, talking about sunscreens with Dr. Kanade Shinkai. Tell us about SPF factors. They go from what? 5 to 100. 

KANADE SHINKAI: Well, I remember growing up, we had sunscreen SPF 2, 4, 8, and maybe 15 was the highest it went. And now, I’ve seen sunscreens as high as 110 SPF. SPF is really a factor that allows us to measure how much protection we have in terms of time outdoors. 

If you’re likely to burn within a certain amount of time, SPF 2 would allow you to be outdoors or under direct sun exposure for twice the length of your normal burn rate. Obviously, that’s going to be different for every individual who uses sunscreen. But the recommendation is that SPF 30 is a good thing to shoot for when you’re out purchasing a sunscreen because that works for most people and essentially blocks almost 95% to 97% of all the UV that you’re being exposed to. 

IRA FLATOW: So you don’t have to go for 50 or 70, you’re saying, or anything above 30? 

KANADE SHINKAI: Well, that’s the party line. SPF 30 is definitely the party line. However, we do know from many scientific studies that in real-world use, many users don’t apply the sunscreen thick enough. And if you don’t apply the sunscreen adequately, you’re actually getting less SPF protection because you’re just dosing yourself with less of the medication. So one of the purposes of looking at an SPF that’s 50 or higher can be that if you use half the amount, you’re essentially getting the right amount, right? 

IRA FLATOW: Interesting. 

KANADE SHINKAI: However– yeah– and I think also, too, that it gives you a little bit more wiggle room in terms of some of the factors that we don’t have a lot of control over, for example, how much of your sunscreen gets rubbed off, or how much of it washes off when we’re swimming or sweating. 

IRA FLATOW: But if you do it the right way– and that’s an important thing that you brought up– you have to put enough of it on your skin. 

KANADE SHINKAI: That’s right. 

IRA FLATOW: Sometimes I think I don’t want to waste it, or I don’t want to use the whole tube up, so I put a thin layer on, right? 

KANADE SHINKAI: That’s right. Well, for the average-sized adult, the recommendation is to use one ounce, or a shot glass if that helps your listeners kind of visualize how much of that sunscreen would be. And most sunscreens that we purchase in a store, at least a regular-sized tube of sunscreen, would be about four ounces. 

So if you can imagine an adult going out to the beach, and they’re going to apply the medication to their entire body, and they’re going to put it on four times a day, which is what it says on the sunscreen label, that that bottle is going to go pretty quickly. It’s going to be pretty much used up within a day or two. And as we probably all would admit, that usually doesn’t happen. So it means to say that all of us are probably not using enough. 

IRA FLATOW: And of course, you want to put it on again as it wears off, so that bottle is not going to last, even all day. Yeah. This is really interesting stuff. I want to thank you for taking time to be with us today. 

KANADE SHINKAI: My pleasure. 

IRA FLATOW: Dr. Kanade Shinkai is a professor of dermatology and Editor-in-Chief of the Journal of the American Medical Association Dermatology section.

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