I’m very excited about this post for two reasons. One: it’s the first time I’ve recruited a guest blogger to write for It’s MomSense. This is cool to me because it means someone thinks my blog is influential enough to take their own (unpaid!) time to research and help us parents wade through the misinformation running rampant in parenting circles. The second reason is that this is a topic that I have meant to look into for some time. I am very fair skinned and burn easily and I’ve managed to pass this trait on to my red-headed son. I feel like I’ve spent every summer since he was born running around after him with a tube of sunscreen and a hat. Every once in a while there’s a small voice in the back of my mind asking if I’m actually doing him a disservice by routinely rubbing chemicals into the skin on the back of his neck. As a result, a while ago I added “sunscreen ingredients” to my running list of things to research and blog about. Now that summer is in full swing and the sunscreen and I are best buds again, I’m glad to check this one off my list.
Because this topic is pretty involved, we decided to split it into two posts. So today and next week you’ll be hearing from Jen Phillips instead of me! Jen is the mom of two kids (one teen, one darn close) who has a PhD in biology. She is a Senior Research Associate at Westerfield Laboratory Institute of Neuroscience at the University of Oregon. There she uses zebrafish to study the molecular genetics of human diseases. When she’s not hunkered down in a dark microscopy lab, she likes to romp in the sunshine with her family and dog. Jen plans to start her own blog at some point this year under the name Clutch Science. For now, you can follow her on twitter @ClutchScience. Here’s Jen to shed some light on sunscreen ingredients. Hope you enjoy. -Sara
Part 1: The dark side of our closest star
Confession time: I love the sun. Swimming, running, working, reading, eating, lounging, it’s all better done outdoors, as far as I’m concerned. But, as a fair-skinned woman, and mother of two lightly pigmented kids, I’d be foolish to ignore the risk involved, or to fail to take preventative steps to keep us healthy. I am a stickler for sunscreen use, and, much to the chagrin of my children, I will not hesitate to halt a fun outdoor activity if it’s time to reapply.
It’s not news that sun protection is an important part of preventative health. Ultraviolet radiation damages skin in a number of ways, the most serious of which can lead to cancer. Recently, though, concerns about sunscreen ingredients have made headlines, raising questions about whether sunscreens are effective at skin cancer prevention and even whether the use of sunscreen carries inherent health risks. **Spoiler alert: sunscreen is safe and effective and you should use it with confidence. If you’re interested in knowing more about the basis for the concerns and why you don’t need to worry, though, please read on!**
In the first of this two-part series, I’ll outline a bit of the biology and strategic chemistry behind the interactions with our closest star, in order to set the stage for discussing the most popular current controversies in Part II.
UV radiation: what’s in a wavelength?
UV radiation occupies the electromagnetic spectrum between visible light and x-rays. The UV portion of the spectrum can be divided into quite a few subcategories, but the two that we’re most concerned about in sun exposure are known as UVA and UVB rays. UVB rays (also known as “burning rays”) can’t penetrate beyond our epidermis, or outer skin layer. In addition to causing sunburn, DNA damage to epidermal cells by UVB rays is a driving factor in the development of skin cancer in light skinned people. Until recently, UVA rays were alternatively called “Tanning rays” or “Ageing rays” depending on what product was being marketed. In contrast to UVB rays, UVA rays penetrate more deeply, through the epidermis to the dermis below. UVA rays cause inflammation and damage to structural proteins in the dermal layer, which have historically been associated with wrinkles and saggy skin. More recently, UVA radiation has also been implicated in DNA damage that can lead to skin cancers. This reclassification led the FDA to upgrade its caution on the use of tanning beds, by the way, which use primarily UVA wavelengths and were often advertised as a ‘safe’ form of tanning before the carcinogenic potential of UVA rays were better understood. Now that we know better, let’s talk about skin cancer.
Your epidermis is showing
Cancer of any type arises through DNA mutations that alter cellular behavior. UV radiation has been used in laboratories to induce mutations in cells for nearly a century. Our skin is exposed to UV radiation on a regular basis, and while the pigments in darker skin offer protection against cell damage, those of us with fair skin have an increased risk of skin cancers as a result of sun exposure.
All skin cancers originate in the epidermis, which is composed of a tightly packed basal cell layer and a more mobile layer of cells known as squamous cells. Our skin sheds and renews itself regularly, so the epidermis is constantly cranking out new cells that progressively travel from deep in the epidermis up toward the surface, changing shape as they go.
Skin cancers are classified into three broad categories according to the cell type affected: Basal cell carcinoma, Squamous cell carcinoma, and Melanoma. Genetics and environment influence susceptibility, but in light-skinned people, sun exposure is a major risk factor for all three types.
Basal cell carcinoma (BCC) is the most common form of skin cancer in people of European and Hispanic descent, with nearly 3 million cases diagnosed each year. It is also the most benign, as it rarely spreads to other cells beyond the original tumor site.
Squamous cell carcinoma (SCC) Is the most common form of skin cancer in dark-skinned people (who have a lower incidence of skin cancer overall because of the protection of higher melanin levels in their skin) and the second most common form in light-skinned individuals. About 700,000 cases are reported each year. SCC can be disfiguring if left untreated, and can, more rarely, spread to other regions of the body.
Melanoma, a cancerous overgrowth of melanocytes, accounts for only 2% of all skin cancers overall, but has the highest death rate of them all. Melanocytes, which produce skin pigment, are found in the basal cell layer of the epidermis, but their developmental origins and cell biology are distinct from the other cells in this layer. These differences, which amount to different gene regulation for things like cell division and migration, contribute to the uniquely aggressive nature of malignant melanomas.
Considering the varied ways that things can go wrong in living skin cells, it’s important to understand what preventative steps we can take. Limiting sun exposure during the peak hours is always a wise recommendation, as is the use of hats and clothing to cover the most exposed areas. But as lots of outdoor activities aren’t compatible with those guidelines, protection that can be applied directly to the skin is a great advantage.
How does sunscreen work?
All available sunscreen products contain UV filters that absorb, reflect, or diffuse UV radiation. Ingredients with these properties are classified as either organic (carbon-based), or inorganic (based on other elements).
Lots of chemistry goes into choosing compounds that make the best sunscreen ingredients. Compounds are tested for the particular range of UV wavelengths they can intercept and for durability. The best compounds will block a wide swath of the UVB spectrum without being easily degraded. No one wants to wear sunscreen that has to be reapplied every 15 minutes, right? These qualities must then be weighed against the utility of the ingredient in a product designed to be applied to human skin: Does it stink? Does it have a texture or color? Does it irritate skin or cause allergies? Are there other safety or toxicity concerns? FDA approval is required for all sunscreen ingredients, and their standards for safety testing are quite rigorous. In fact, a number of organic sunscreen ingredients approved for use in Europe haven’t made the grade as far as the FDA is concerned.
What about SPF?
Sun Protection Factor of a product, or SPF, is usually framed for marketing purposes as the amount of time you can spend in the sun before burning when using the product versus time spent in the sun without it. More specifically, the SPF value is the quantifiable effectiveness of the UVB filtering capacity of any given ingredient—or combination of ingredients. This is a non-linear numerical scale. An SPF of 15 corresponds to blocking about 94% of UVB rays, while an SFP of 30 increases blocking capacity to 97%.
Note that SPF rates the product’s effectiveness of blocking only UVB rays. Since learning more about the damage that UVA rays can create, Sunscreen formulas have expanded to include UVA filtering alongside UVB (SPF-rated) protection. Again, there’s a bit of a difference between how we do things in the US vs. abroad. Other countries have a rating system (out of 5 stars) to indicate the strength of the UVA blocking compounds. The FDA hasn’t implemented any such system yet. The presence of UVA filters added to the SPF-rated UVB compounds in US products isn’t quantified, and only the words “broad spectrum” let you know that your sunscreen contains both UVA and UVB blocking ingredients.
To sum up this overview of the science behind sunscreen, both UVA and UVB rays can have detrimental effects on the health of your skin, so in addition to limiting exposure in as many ways as are practical, having a good sunscreen product on board is essential.
However, for the past several years a number of controversial warnings about the safety and effectiveness of sunscreen products have emerged. In Part II of this series, I’ll examine those claims one by one to determine if there is really cause for concern.