Does sunscreen cause cancer?
Like almost any topic in the field of health and wellness, it seems there is a tangled web of research and opinions when it comes to cancer, sun exposure and sunscreen ingredients. Should we wear SPF 50 sunscreen for our walk from the house to the mailbox, or should we shun all sunscreens in our quest to increase our Vitamin D levels as much as possible? Do we buy sun protective clothing to safeguard every inch of our skin from the damaging UV rays, or should the real cause of our cancer fears be the sunscreen ingredients themselves?
As usual, I’m going to seek the balance on this controversial topic and try to share with you some brief synopses of research on the issue. I am grateful for the direction EWG offers in their yearly Sunscreen Guides but realize that multiple sources are necessary, especially when I read articles like this one questioning EWG’s scientific validity. In spite of the rebuttal, I think EWG does a great job organizing a wealth of information.
The ultimate questions for any suncream is: Does it protect from both UVA (cancer causing) and UVB (skin damaging/burning) rays?
Look for terms like “broad spectrum” coverage for starters, and then you need to learn about UVA protection, which pretty much only comes from active ingredients avobenzone, zinc oxide and titanium dioxide. All sunscreens will protect from UVB rays because you’d notice if it wasn’t working – you’d be sunburned!
Notably, in 2011 the FDA banned the use of the term “sunblock” on sunscreen products.
How Chemical Sunscreen Works
“Sunscreens absorb UV energy and have to be absorbed into the upper layer of skin to really get up to full speed,” says Darrell Rigel, clinical professor of dermatology at New York University Langone Medical Center. (source)
A chemical reaction takes place between the sunscreen ingredients and the UV rays to “screen” your body from most of the effects of the sun. That’s why the instructions on the sunscreen bottles say to put it on 20 minutes before being exposed to the sun. It needs that time to sink in to your skin before its full SPF is realized. (1, 2, 3)
Because the active ingredients in chemical sunscreen don’t provide broad spectrum coverage alone, there must be a proper balance of multiple actives to offer balanced, safe coverage.
I use the term “safe” loosely there – safe from sunburn, but because the chemical constituents also degrade in the sunlight, they’re really not safe. More below…
How Mineral Sunscreen Works
Mineral active ingredients in sunscreen, on the other hand, are called a “physical” block rather than chemical. They sit on the surface of your skin rather than being absorbed into it. Most sources say that sunblocks “reflect and scatter UV light.” (1, 2, 3, 4 and many more)
On the other hand, the founder of Kabana, a biochemist from Stanford, disagrees with that explanation and claims instead:
“Zinc oxide has a broader UV absorption profile than titanium dioxide, which is noteworthy, because much misinformation populates the media about how these chemicals protect us – they do NOT reflect and scatter in the UV spectrum – rather zinc oxide absorbs UV and does so very effectively. The media (and ‘experts’ alike) need to investigate the physical chemistry of these compounds, rather than assume they reflect UV light because they look white in the visible spectrum. They do reflect in the visible, but would look black in the UV.” (source)
Either way, sunscreens use minerals that sit on the surface of the skin (usually zinc oxide and titanium dioxide) rather than chemicals that sink into the skin to protect one from the sun. Mineral sunscreens begin working right away on both UVA and UVB rays, so there’s no need to apply 20 minutes before sun exposure.
UPDATE: Here’s a GREAT interview with Erik Kreider, founder of Kabana. He covers all the science geek information and research about sun safety and the hazards of petrochemical sunscreens. I learned a lot!!
What is a Sunburn?
What exactly are we trying to protect ourselves from when we use sunscreen, anyway?
According to this source from a dermatologist: Ultraviolet rays of sun penetrate the skin and cause damage to the skin.
Inflammation and redness is a first level sunburn. Blistering means deeper damage to the skin. Tanned skin is superficially damaged skin. Tanning is the skin’s way of trying to protect the skin from damage.
What Does SPF Mean?
Every person’s skin has a certain tolerance for sun, and SPF (Sun Protection Factor) multiplies that tolerance. If you could spend 15 minutes in the sun without getting burned, applying the appropriate amount of an SPF 15 product would allow you spend 15 times 15 minutes in the sun.
Another way of describing SPF is to say that the sunscreen absorbs UV rays at a percentage based on the SPF. For example, that SPF 15 sunscreen would allow your skin to absorb 1/15 th of the UV rays that it would if you weren’t wearing any protection. That’s about 6.7% of the rays coming through your sunscreen.
Here’s where it gets interesting. Using that formula, an SPF of 45 allows your skin to absorb 2.2% of the UV rays. Increasing the SPF three times only increased the protection by 4.5%. (1, 2) Some use that data to claim that SPF 15 is really all you’ll need, since higher SPFs don’t add much protection at all. This doc at WebMD says anything over SPF 45 is “silly” and recommends SPF 30 to patients.
Often studies show that those who use a higher SPF are more likely to get melanoma (skin cancer), possibly because they’re tricked into thinking they’re safe from the sun and stay out longer. In 2011 the FDA was considering banning SPFs over 50 because they can feel so misleading, but they didn’t go through with it.
All Sunscreens Release Free Radicals
The sun is said to cause cancer because it forms free radicals in the skin. Sunscreens help protect our skin (to an extent) from that radiation, but in the process they also form free radicals, because all the energy from the sun has to go somewhere.
The trick is to block more free radicals than the sun cream creates. Many sunscreens include natural antioxidants like Vitamin E or green tea to combat the formation of free radicals in the skin.
The Risks of Chemical Sunscreens
Since chemically-based sunscreens have to be absorbed into your skin just to start working, they have one strike against them already just for entering your system instead of sitting on the surface. Some of the potential health risks of chemical sunscreens include:
- Hormone disruption; mimics estrogen and raises risk of breast cancer (theoretical but frightening) 1, 2
- Allergic reactions
- Bioaccumulation in tissue and organs (found in 97% of Americans’ bloodstreams!)2
- Also found in mother’s milk, demonstrating its reach even to the unborn
- Oxybenzone is pegged for lowering thyroid hormone (source)
- Shaving may increase the absorption of the chemicals (source)
- Failure to biodegrade in the environment 3
Oxybenzone is the chemical ingredient with the most fingers pointing at it; that’s the one found in 97% of Americans. If I was only avoiding one ingredient, Oxybenzone would probably be the winner, especially for children, whose small bodies make them especially susceptible to endocrine disruptors.
Those free radicals that form when the sun’s rays touch the sunscreen are ironic, don’t you think, since you can’t exactly avoid that situation, or you wouldn’t need sunscreen in the first place. Free radicals are cancer-causing, but here’s the catch: It’s thought that both the sunscreen and the sun must penetrate deeper into the skin in order for the problems to happen.
If you reapply, the new sunscreen will, in theory, block the sun afresh and stop its path to the already well-absorbed sunscreen. If you don’t reapply, you may just be inviting skin cancer to roost in your skin. Applying a chemical sunscreen one time, particularly one with oxybenzone, and forgetting to reapply when still in the sun may have worse consequences than not applying any sun protection at all.
Are There Safer Chemical Sunscreens?
Perhaps you don’t like the ghostly pallor of folks using zinc-based sunscreens, which are opaque white and notoriously hard to rub in well (see tomorrow’s natural sunscreen review for more info). Perhaps you’ve tried them and burned. If you are still hooked on using a chemical sunscreen for whatever reason, there are safer choices. Remember this:
- Always avoid oxybenzone (B for “bad”) rated 9 at EWG
- Usually avoid anything with “methoxycinnamate” or octinoxate in the name (no “cinn”amon or “ox”es in sunscreen) rated 6 at EWG
- Usually avoid Padimate O/PABA (PaBa = pretty bad, allergies, allergies!) rated 6 at EWG
- Homosalate is okay (homosalate for homosapiens) rated 4 at EWG
- Octocrylene is okay (octoCrylene gets a “C” grade) rated 3 at EWG
- Choose Octisalate (octiSalate is Safe) rated 3-4 at EWG
- Choose Avobenzone (A for “A plus” rating) rated 2 at EWG (Avobenzone is also the ingredient that screens for the UVA rays, so it’s important to have this one or one of the minerals titanium dioxide or zinc oxide to get broad spectrum coverage.)
Mineral Sunblocks: Nano vs. Micronized Particles
As soon as you learn to look for words like “zinc oxide” and “titanium dioxide” on your sunscreen (sunblock!) bottles, another layer reveals itself. Apparently smaller sized pieces of the minerals rub in more effectively (but also change the way the UVA and UVB radiation is screened out). For aesthetic reasons, many sunscreens therefore use “nano particles” of both zinc oxide and titanium dioxide.
The smaller the particle, unfortunately, the more likely it is that it is absorbed into the skin, where it could cause unknown problems, including…what else? Cancer. 1, 2, 3 The nano particles may also be more hazardous to the environment and even if swallowed inadvertently while swimming.
This review of sunscreening agents from the Journal of Clinical and Aesthetic Dermatology states:
“Studies have shown that nanoparticles of these two compounds [zinc oxide and titanium dioxide] cause cytotoxicity, genotoxicity, and potential photocarcinogenecity.”
That article is a great overall scholarly summary of a ton of sunscreen information and research, if your science geek brain wants to go deeper.
You might also see the term “micronized” on a sunblock using zinc oxide or titanium dioxide. This is a smaller form of the minerals, but not as small as “nano”. If the ingredients weren’t “micronized” – simply the process of grinding them smaller – they would be gritty like sand, rather ineffective at protecting your skin, and pure opaque white if it was possible to apply correctly. Micronized minerals are not small enough to get through the cell walls and are nothing to worry about.
Not all sunscreens disclose on the labels whether they use nano or micronized minerals. A good rule of thumb: If your zinc or titanium sunscreen goes on clear it is nanosized.
Here is some scholarly research worth reading if you really want to know more: A review of the scientific literature on the safety of nanoparticulate titanium dioxide or zinc oxide in sunscreens
Is Zinc Oxide Better Than Titanium Dioxide?
This study shows that zinc oxide is far better at blocking UVA than titanium dioxide, important for broad spectrum coverage, and The Skin Cancer Foundation discusses how both zinc and titanium dioxide are broad spectrum but zinc is more effective.
This study from 1997 demonstrated that microfine zinc oxide is broad spectrum and a safe and effective sunscreen.
Here are some studies that demonstrate that titanium dioxide does not penetrate the skin: 1, 2, 3 However, here’s a great interview with sunscreen expert Erik Kreider in which he explains (around the 25-minute mark) that titanium dioxide is still not as preferable as zinc oxide because:
- Zinc oxide has the best UV Absorption profile
- Zinc is a critical mineral nutrient and even in vitamins (whereas titanium dioxide is a heavy metal)
- Zinc oxide is the only active ingredient the FDA approves for babies – Zinc oxide is the active ingredient in many diaper rash crèmes, which is a pretty clear indication that it’s gentle and safe for even the most sensitive skin.
- Zinc oxide holds onto its electrons more tightly (and therefore should generate fewer free radicals when exposed to the radiation of the sun)
I am not opposed to or scared of titanium dioxide, but when I am looking at optimal ingredients, I prefer zinc only.
Zinc oxide is also the only active sunscreen ingredient approved by the FDA for infants under six months, which is a striking fact.
Zinc oxide is a better sunscreen ingredient, as it offers the best UVA protection of all current sunscreen chemicals, and titanium dioxide is second best. (source) I don’t know that I’d avoid titanium dioxide with as much vehemence as I avoid oxybenzone, for example, but pure zinc oxide sunblocks are probably the best choice.
The Dangers of Sunshine? Or One More Danger of Sunscreen?
The real question is whether or not we need protection from the sun at all.
It seems that it’s simply common knowledge, no source needed, that the UV radiation from the sun (both UVA and UVB) increase one’s risk of skin cancer, and that any time spent in the sun, and particularly any sunburns, are one of the root causes of skin cancer.
Sunscreen is often used as the first (only?) line of defense against the skin cancer monster. Unfortunately, both the EWG and the FDA warn that “sunscreens should not be the first choice for skin cancer prevention or used as the sole agent for protection against the sun.” The International Agency for Research on Cancer writes, “Sunscreens were never developed to prevent skin cancer. In fact, there is no evidence to recommend that sunscreens prevent skin cancer in humans.” (Zoe Diana Draelos, editor of Journal of Cosmetic Dermatology, 2010)
Some, like Dr. Michael Eades, a blogger with an M.D., and Dr. Michael Holick, who just wrote a book on how to get enough Vitamin D, would say the reason sunscreen use is linked to skin cancer is that the sun isn’t the problem at all. They point to the fact that there is little to no scientific research that the sun causes melanoma and plenty of data demonstrating that chronic sun exposure and vitamin D seem to prevent it. (source)
Skin Cancer: a Sun Issue?
Although it’s easy to accept “the sun causes skin cancer,” research shows that other options might include:
- skin tone/heredity
- sunscreens themselves
- vitamin A
Here is one example of a study from 2005 in the Journal of Public Health Nutrition that “aimed at examining the association between dietary constituents and risk of cutaneous melanoma.” In a small population segment in Italy, the researchers found two dietary factors that increased melanoma risk:
- high linoleic acid intake (that’s polyunsaturated fats, also known as industrial oils like soybean, corn, and vegetable oil)
- low soluble carbohydrate intake
There is anecdotal evidence from people who eradicate industrial polyunsaturates from their diet and suddenly have a high tolerance for the sun and rarely (if ever) burn. I don’t have any data, however, that demonstrate the link between sunburn and diet (not to say that it doesn’t exist).
Other evidence shows that “fair-skinned people really are at a higher risk for skin cancer, regardless of how much sun their country gets.” Still more research shows that chemical sunscreens cause “profound changes in sun behavior.” There can be more damage staying too long in the sun with a high SPF sunscreen than if bare skin were exposed to UV rays, particularly if you don’t reapply as I mentioned above.
Vitamin A, one of the antioxidants added to many sunscreens, was just pegged by an FDA study that showed that retinyl palmitate, a form of Vitamin A, may speed the development of skin tumors and lesions when exposed to sunlight. (source)
Vitamin D: The benefits of sunshine
If sun may not be the enemy, is it possible that it’s actually a healthy advantage? It seems to fly in the face of popular reason from a few years ago to say that we need sunshine, but it’s been hard to miss the trend toward healthy sun exposure vs. avoidance of the sun at all costs.
Vitamin D is essential for good health. Sure, it’s synthesized and added to milk, but the best and most natural way to get your daily dose of Vitamin D is to spend some time in the sun. (gasp!) Yes, that’s right – time in the sun is healthy for you. In fact, the American Medical Association recommends Vitamin D in the form of 10 to 15 minutes of direct sun (without sunscreen) several times a week. Dermatologists disagree, citing the skin cancer risk.
Want a fact? Over twice as many people will be struck with a health issue because of Vitamin D deficiency as will be affected by overexposure to the sun.
Vitamin D is necessary for:
- Healthy bones
- Strong immune system
- Protection from cancer
- Cardiovascular health
Lack of vitamin D increases your risk of (source):
- Heart attack
- Colon cancer
- Breast cancer risk
- And possibly: skin cancer, high blood pressure, depression, dementia, prostate cancer, erectile disfunction, schizophrenia, , and dozens more (source)
Many scientists and organizations recommend MORE Vitamin D in this editorial request from The American Journal of Clinical Nutrition:
Human diets do not provide sufficient vitamin D; if they did,the above mentioned associations between health and serum 25(OH)D concentrations would not be so routinely observed. The vitamin D provided by foods and supplements is overwhelmed by the effect of skin exposure to ultraviolet B light. Geography, season,skin color, and sun-related behavior are the main predictors of vitamin D nutritional status. Correction of low 25(OH)D concentrations can happen only if some or all of the following are implemented: the encouragement of safe, moderate exposure of skin to ultraviolet light; appropriate increases in food fortification with vitamin D; and the provision of higher doses of vitamin D in supplements for adults.
I remain fascinated by this article on Vitamin D and sun exposure by Dr. Michael Eades. Here are a few notable points:
- An SPF 8 reduces vitamin D synthesis by 90 percent. Just putting on basic sunscreen and going out in the sun makes it so that you’re not getting much Vitamin D. I think about the days when I stuck sunscreen on my toddler first thing in the morning when I read that kind of statistic.
- When you are exposed to sunlight, you make not only vitamin D but also at least five and up to ten additional photoproducts that you would never get from dietary sources.
- “8,700 people died last year from melanoma. We know that sun exposure and vitamin D (along with maybe the other 5-10 photoproducts we synthesize from sun exposure) help prevent breast, colon and prostate cancer. Last year 40,230 people died from breast cancer, 32,050 from prostate cancer and 51,370 from colon cancer. So, on the one hand, we have 8,700 people die of a disease that probably isn’t related to sun exposure while on the other we have 123,650 who died from cancers known to be related to lack of sun exposure.” I realize you can twist statistics to demonstrate just about anything, but these are striking to me!
How Much Sun is Enough?
How do we synthesize all this information and apply it to what we’re going to do the next time we walk out the door into the sunshine? Here’s how I break it down so I can digest the facts in one bite:
- The sun may or may not cause skin cancer, which can be treatable or deadly.
- The sun DOES cause sunburns, which just plain hurt (among other possible negative side effects).
- Chemical sunscreens may or may not cause skin cancer, and there are other health and environmental risks linked to oxybenzone and other active ingredients.
- Mineral sunscreens have a slight chance of causing skin cancer, too, but are much safer otherwise than the chemical kinds. Zinc oxide is always broad spectrum, so it protects your skin from all the radiation from the sun, not just the burning rays.
- We need Vitamin D – from the sun – for optimal health.
- Sunscreen also inhibits Vitamin D.
- Therefore we need some time in the sun, unprotected.
- Nobody wants a sunburn, so….
…the bottom line is that we need some sunshine every day, unprotected, for Vitamin D, but we have to balance that time in the sun with the risk of sunburn for our particular skin type. If your sun exposure needs to be at 8:00 a.m. in order for you not to burn, and then you use the safest natural sunblock you can find, I’d say that’s a pretty good application of the information.
For our family, I’m determined to have some options for safe sunscreen for those times when we’re in the sun in the middle of day and can’t seek shade. I’m also determined to only use sunscreen when necessary and try to balance sun and shade, sun protective hats with basking in the Vitamin-D enriched rays. We’re fortunate enough to have a rather shady yard, so I am in control of our sun exposure most of the time.
I like Sara Van Anrooy, MD’s tip to get 10-15 minutes of sun before applying sunscreen to soak up that Vitamin D (here).
Our family has personally tested out over 80 brands of (mostly) natural sunscreens, those rated 0-3 (safe) at the EWG Cosmetic Safety Database, along with sun protective clothing from five companies. Here is my massive natural sunscreen review to help you at the store!
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