Sunscreen safety and efficacy

Listen: Sunscreen safety and efficacy

Sunscreens have become a staple tool in our fight against skin cancer.  In spite of the great progress made in educating the public about the value of sunscreens, there remain many doubters about the safety and efficacy of these chemicals. Darrell Rigel, M.D., clinical professor of dermatology at New York University, will help to set the record straight on these agents.

Dr. Norman Levine: First, I’d like to boil it down to one most important question: On balance, are sunscreens good or not good for patients?

Dr. Darrell S. Rigel: On balance, I think the data is very clear, sunscreens are good for patients. It takes a while to get that answer, because you need to have studies with follow-up to show it, but it is very clear that for melanoma and non-melanoma skin cancer, regular use of sunscreens lowers a person’s risk for developing the disease.

Dr. Norman Levine: Are sunscreens good for patients no matter what age one starts using them?

Dr. Darrell S. Rigel: The earlier you start protecting yourself, the better; whether we’re talking about sunscreens, protective clothing, or avoiding the midday sun. I describe skin’s sun exposure as being like a meter in a taxicab, because I am from New York City. The cab’s meter only goes forward; similarly the effects of the sun on your skin may occur faster or slower depending on the amount of the sun exposure you have. But the reality is that if you protect yourself, you are slowing down the aging process and your risk of skin cancer later in life.

NEXT: Chemicals in sunscreens

Dr. Norman Levine: The other issue often raised involves chemicals in sunscreens. Please describe any issues regarding specific chemicals and their harm to the patient.

Dr. Darrell S. Rigel: I always get a laugh when I see sunscreens claiming to be “chemical-free,” because there are chemicals in everything. There is no such thing as a chemical-free sunscreen. With several of the sunscreen agents that are comprised of all chemicals, some studies have suggested there might be potential problems.

One chemical that always rises to the top is oxybenzone, or all of the benzophenones. There was a study done in rats where they fed female rats high levels of benzophenones. What they found was that some of the rats had uterotrophic effects from the ingestion of the benzophenones.

Further research on this showed that for humans to get the same levels of benzophenones as the rats would equate to applying the sunscreen on the entire body every day at the amount rated by the FDA, which is 2 mg/sq cm. Nobody uses sunscreen at that concentration, but if you were to, it would take 34 years of daily application to get as much benzophenone as those rats were given in that period of time.

If you just use sunscreen in the way people normally use it on a regular basis - on the face or head and neck or the back of the hands - it would take over 200 years to get the dose that those rats received. So obviously, anything in extreme is bad. Although several sunscreen agents have been implicated at least in some studies, overall when researchers looked at them in more depth or did more studies, the sunscreen agents were shown to be safe.

NEXT: Sunscreens getting in water supply or polluting rivers?

Dr. Norman Levine: Is there any legitimate concern with sunscreens getting in the water supply or polluting rivers?

Dr. Darrell S. Rigel: Again, these agents are made of chemicals. When you look at hypothetical risks that have been raised by people with the exposure to these chemicals, there may be legitimacy in theory. However, the flip side of this is, tens of millions of Americans use these agents with these chemicals every weekend all summer, and we are not seeing anything close to what’s been suggested might happen with these hypotheses. So in a sense, we are doing the experiment indirectly and unintentionally, but we are not seeing some of the things you’d expect to be potentially problematic.

Dr. Norman Levine: Would you clarify the relationship between vitamin D deficiency and sunscreen use?

Dr. Darrell S. Rigel: Vitamin D deficiency and sunscreen use has been pretty much refuted. Clearly, if you regularly use high-intensity sunscreens and you minimize your sun exposure, you are going to have a lower vitamin D level than somebody who does not. But, the way vitamin D is converted in your skin through its usual form, you get about one-third of an MED of exposure, and then the system is overloaded, so you don’t get more beyond that one-third of the MED. So you are not just getting anything extra from the extra exposure, and if you are worried about your vitamin D level being low because you protect yourself so much in the sun, what you can do is take vitamin D supplements. They are inexpensive, they are effective, and they have been pre-converted for you.

Remember vitamin D is not made in the skin; it’s converted through its usable form in the skin. So if you take vitamin D pills and they are pre-converted, you do not need any kind of UV exposure. You can get high vitamin D levels without having to get any of the risks of UV exposure.

NEXT: Pulses and minuses of sunblocks versus sunscreens

Dr. Norman Levine: Would you discuss some of the pluses and minuses of the so-called sunblocks versus sunscreens?

Dr. Darrell S. Rigel: The terms sunblock and sunscreen are rather passé now. They are now called organic and inorganic sunscreens. What we now view as organic sunscreens would be the so-called sunscreens from the past. Basically these are agents that primarily absorb the ultraviolet radiation and convert it to a different type of radiation.

Most sunscreens absorb the UV radiation and convert it to a red light wavelength. You do not see that because you’re outdoors and it is bright, but it actually converts it into a little bit of red light, which is not harmful. The so-called sunblocks, like zinc oxide or titanium dioxide, are basically reflectants. So they are just reflecting the waves off the surface but not really changing the energy itself. They both have advantages and disadvantages.

The sunscreen, or what we now call the organic sunscreen, basically absorbs the energy. Additionally, the elements themselves are absorbed into the skin a little bit, which is a bit of concern. There is some absorption of chemicals. If you look at oxybenzone, in fact, it entails a little bit of systemic absorption; however by mixing these chemicals, you can get a much broader and better protection because each of these sunscreen agents have slightly different absorption characteristics.

The inorganic sunscreens, or so-called sunblocks, basically have the same amount of protection across the entire spectrum because they are just reflecting, but you cannot get them to the level of protection that you get with the organic agents.

Although they supposedly are not absorbed, there was one study conducted in Australia, where they applied zinc oxide on the forearm daily for six consecutive weeks and then did a punch biopsy. It turns out you could find micronized zinc in the dermis even after that six weeks of application. Nobody knows if that is good or bad, but it does occur. The best sunscreen has a combination of the two, because then you get the pluses of each one. You get the reflectance as well as the higher intensity in broader spectrum. They are synergistic when you have that mix.

NEXT: Inorganic sunscreens tend to be less substantive...is that an issue?

Dr. Norman Levine: My understanding is that inorganic sunscreens tend to be less substantive, and they actually break down in the sun. Is that an issue with these kinds of products?

Dr. Darrell S. Rigel: Actually, sunblocks and sunscreens both break down. The sunscreens or the organic ones are catalysts effectively; so they will go on and on and continue to break down until at some point they are broken down themselves. So typically in about two hours, most of the sunscreens - the organic sunscreens - are broken down. How long they last is called substantivity.

With the sunblocks, what will happen is that they will clump on the skin over time. So instead of having a nice uniform spread, you begin to see the areas where the sun can just get through.

Dr. Norman Levine: Is the vehicle into which the sunscreen or sunblock is incorporated an important issue? When I see people spraying the sunscreen on their kids because the kids like the sprays, it seems intuitively that they are not getting the same degree of protection. What are your thoughts?

Dr. Darrell S. Rigel: The vehicle does make a difference. I look at it differently. I want people to use what they like the best, because if they don’t like it, they are not going to use it. So, if you have a gooey, yucky vehicle, it could be the best sunscreen in the world, but nobody would use it. Each of the vehicles has advantages and disadvantages. The gels tend to wash off a little easier than something heavier. Believe it or not, sprays are now the number one formulation sold in the United States.

One note about the spray is that it is very important to spray on two coats, because with the spray, you often do not know where you have missed. With the cream, you typically know where you apply it in most cases. So what is really important is making sure that people do cover themselves uniformly.

NEXT: Should everybody be wearing sunscreen? 

Dr. Norman Levine: Here’s a provocative question for you. Should everybody be wearing sunscreen? If you live in Northern Minnesota, do you need to be wearing sunscreen?

Dr. Darrell S. Rigel: It always pays to protect yourself, but you have to use common sense. If it is a December day in Minnesota and it’s cloudy, you don’t need to use sunscreen. The amount of UV that you are getting is so little that it does not make any sense. If it’s a June day in Southern Arizona, of course you want to protect yourself, because the sun’s intensity would be remarkably strong there.

Again, if it’s an area where you are not going to be outdoors very much and it’s a cold time of year, then you don’t need to put it on every day.

On the other hand, do daily products such as moisturizers that have some sunscreen component to them help those who use them regularly? Probably, because it’s not just the UVB that’s protective in sunscreen, which is much more variable by latitude and by time of year, but UVA, of which, there is certainly more in the summer, and more in the South, but the variance is not as great. If you can protect yourself from that in the long run, that pays dividends too.

Dr. Norman Levine: Do people of color need to wear sunscreen?

Dr. Darrell S. Rigel: Anybody can get skin cancer, as you know. Certainly the fairer you are, the more easily you sunburn, the more poorly you tan, and the greater your risk in general, but everybody can get skin cancer.

In terms of aging, people of color have natural protection and a better protection from UV damage, but they still can age. If you look at anybody who regularly protects himself from UV damage, they tend to age much better. So the answer is, if it makes sense for you, I don’t think you need as high an intensity of a sunscreen if you are a darker skinned individual, but it does pay off in the long run to use it.

NEXT: Proposed new regulations for sunscreen manufacturers

Dr. Norman Levine: Finally would you discuss the proposed new regulations for sunscreen manufacturers and how they are going to impact us in dermatology?

Dr. Darrell S. Rigel: As you know, these regulations have been in flux since 1979, which is amazing that it would take that long for sunscreen labeling and regulations, and they are still not totally decided. I can speak to what is going on now, what has been changed, and some of the ways the sunscreen bottles are being labelled.

Basically the word broad-spectrum has meaning now. In the past, it was just a marketing term. So broad-spectrum applies to at least SPF 15, and it has a proportional level of UVA protection. SPF only measures UVB protection. Also, there is no such thing as waterproof anymore, there is water resistant 40 minutes or water resistant 80 minutes; again you have some idea of at least the water resistance in terms of the sunscreen.

What I think is so important with this is that you can now tell your patients you want them to use SPF 30 or higher, something that says broad spectrum, and something that says waterproof 80 minutes. So independent of product, at least you give people an idea of what to do.

What’s also happening that’s really important is that the new agents - those that are available in Europe which have not been available here in the United States, hopefully will now become available within the next year or so.

It doesn’t mean that the sunscreen agents we have in the United States are bad, but we’ll just have the ability to have more components to potentially make a better sunscreen. What I care about is that I want my patients to have the best sunscreen possible, and by having more components, theoretically, a better sunscreen can be made.

Whether there is going to be a cap on SPFs of 50+ or more is still up in the air. When the rules came out in 2011, they were going to make a decision, but they haven’t made the decision yet. I am personally opposed to a cap, because I think that it is little bit misleading. If it is a 50+, is it a 51 or is it a 100? In some places that will matter, but if you are a blonde or redhead in Southern Arizona, basically you might want to have something more than 50 to give you some extra protection. You won’t get that from the labelling.

Similarly the higher SPF sunscreens have an advantage because people under-apply sunscreen. Sunscreens are tested, as I mentioned earlier, at 2 mg/sq cm; nobody applies that density. So these higher SPF sunscreens, when used at real-world concentrations, are more forgiving. So if you have SPF 80, but you are applying ¼ of it, you are still getting a protection of 20. That’s the kind of thing that with a lower SPF, you just don’t get that additional window of protection or redundancy.

And finally if you put a cap on, there will be no incentive for people to make a better sunscreen, and they won’t get credit for it - that is a practical reason. But for all those reasons, I hope it’s not capped. It’s still up in the air, but about half the countries in the world do have a cap, so we will see what happens.