If you’ve been shopping for eco-conscious or reef safe sunscreen lately, you’ve probably been amazed at the growing selection of products – and the alphabet soup of confusing acronyms that define them.

Although it usually gets the most attention, SPF may be the least important of that alphabet soup. It stands for Sun Protection Factor and can range from 10 to 100. Several stories over the past few weeks have focused on “the significant difference” between SPF 50 and SPF 100 – without mentioning that researchers have found that the higher SPF is marginally better only because people don’t follow directions to reapply on the label.

SPF is a factor of time not level of protection.  If someone can spend 30 minutes in the sun without burning, applying an SPF 30 should give them 900 minutes – that’s about 15 hours – in the sun without burning.  

But since all guidelines recommend reapplication after 80 minutes, what is the added benefit of a higher SPF?

And even then, the higher SPFs are highly misleading. It makes sense that an SPF 50 would nearly double the protection of an SPF 30, but in reality:

  • An SPF of 30 protects from 97.2% of UV rays for 80 minutes
  • An SPF of 50 protects from 97.7% of UV rays for the same 80 minutes.
  • Anything beyond a 50 SPF only increases the percentage in tenths of a percent.

And even worse — it requires far more UV inhibitors to achieve protection levels of more than about 30 SPF. The science on damage that endocrine-disrupting chemical UV inhibitors cause to human beings is still not 100% clear. However, there is no doubt that the most commonly used sunscreen ingredients – oxybenzone and octinoxate – are lethal to coral larva and increase the potential for coral bleaching.

Much more important than SPF – if you follow the directions and apply every 80 minutes – are the acronyms UVA and UVB that refer to different wavelengths of sunlight. An SPF only applies to UVB, because those are the rays of the sun that cause burning. That’s important if you want to enjoy your vacation, but UVA rays are more important over the long term.

UVA rays account for up to 95 percent of UV radiation – and they’re relatively equal during all daylight hours and easily penetrate clouds and glass. They also penetrate the skin more deeply than UVB rays and play a major role in aging and wrinkling. New studies also show that UVA damages skin cells in the basal layer of the epidermis, where most skin cancers occur.

Since UVA is the dominant tanning ray and they are used in most tanning salons, that may be the reason that younger women who use tanning booths have significantly higher levels of skin cancer — 2.5 times more squamous cell carcinoma and 1.5 times basal cell carcinoma than women who don’t.

To protect yourself over the long term, you need to make sure you buy “broad-spectrum” sunscreen, even though the government has not defined an SPF for UVA rays. From a chemical sunscreen perspective, that means multiple chemicals protecting against different wavelengths of light, so you end up with a bunch of ingredients each doing a little bit of the job.

That’s the biggest difference between chemical sunscreens and those made with minerals. Chemical sunscreens are absorbed into your skin where they absorb the damaging rays and then break down over time, releasing free radicals in the process. They also begin to degrade as soon as they are exposed to UV radiation.  That’s why re-application every 80 minutes is so important.

Mineral sunscreens, on the other hand, sit on top of your skin and reflect the sun’s rays away from you. Of course they can be washed off, but they don’t break down as quickly and don’t release free radicals.  Properly formulated mineral sunscreens with zinc oxide or titanium dioxide can effectively protect against a broad spectrum of UVA and UVB rays, without using harmful chemicals.

The most important thing to remember about sunscreen is to follow the directions. Apply generously – click here for suggestions on using mineral-based sunscreens like Stream2Sea – and remember to re-apply after swimming and toweling off.

Blog author, Autumn Blum, is an award-winning cosmetic chemist and avid diver who formulated Stream2Sea sunscreen and personal care products. Stream2Sea products are the only mineral-based sunscreens proven to be safe in an aquatic environment and contain no ingredients known to harm people.

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