Thursday, June 20, 2013

Protection Factors: SPF and UPF

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There are two types of “protection factors” associated with the sun.  The first is the more common Sun Protection Factor, or SPF.  This is basically a measurement of the skin’s protection against UVB radiation, and it’s determined by measuring the ratio of time the skin would redden with sunscreen against the time it would burn without sunscreen.  Basically, if it takes you 15 minutes to burn, and SPF rating of 2 would allow you to stay in the sun for 30 minutes, or twice the amount before turning red.  Applying an SPF of 10 would theoretically allow you to sunbathe for 150 minutes…2 ½ hours!  So why in the heck would one need a sunscreen of SPF 30…after all, would you really want to stay outside under the hot sun for 450 minutes, or 7 ½ hours?

The truth is no sunscreen is going to stay effective that long.  First of all, your body will perspire under the sun, and sweat will degrade the lotion on your skin. Secondly, and most importantly, you probably don’t put anywhere near as much sunscreen on your skin as those laboratory folks do when rating SPF.  Most folks recommend that you apply about one shot glass of sunscreen to your body per application.  That’s really a lot of sunscreen!  In fact, applying that much sunscreen on your body each time would deplete a typical bottle of sunscreen in less than two days!  So again, why apply SPF 30?  Because one less-than-recommended application of SPF 30 is probably equivalent to a true laboratory coating of SPF 10 or less. 

That’s why you need to apply sunscreen every two hours.  You probably apply sunscreen when you first start your day in the sun, but fail to reapply later on.  Such lotions last about two hours, meaning when you start that round of golf at 10:00AM, you need to be adding it again before you make it to the back nine.  I’m sure many of you don’t.  But you need to.

Admittedly, sunscreen can be a real pain, but it’s important to get past that annoyance and make it part of your regular routine.  And by regular routine, I mean DAILY routine.  Sun damage is a cumulative thing….a little exposure here and a little there adds up.  Even walking the dog or engaging in a brief outdoor activity like lunch can add up over time, so it’s important to apply sunscreen every day…and every day of the year. 

The Skin Cancer Foundation recommends an SPF of 30 as I state above and make sure it’s a broad spectrum lotion.  The Sun Protection Factor only applies to UVB rays…you need the broad spectrum lotion to also protect against UVA rays which contributes to skin cancers and aging.  Even an SPF of 100 doesn’t protect you against UVA rays if it’s not broad spectrum.  Make sure to apply it 30 minutes before you head out to allow it to soak into the skin.  After that, apply it every 2 hours.

Speaking of soaking into the skin, you might have some worries about the effects of the chemicals within such lotions on your skin and health.  For the vast majority of products, sunscreens are safe.  In fact, sunscreens are regulated as a medical product by the FDA the same as topical pain killers, acne creams, etc.  In Europe, sunscreens are considered a cosmetic and fall under far less scrutiny for skin safety.  Titanium oxide and zinc oxide are two chemistries that have been used as effective blocking sunscreens for years.  However, recent technology has allowed these elements to become smaller and smaller.  There is a real concern that nanoparticles of either chemical could now penetrate the skin.  Studies thus far are inconclusive as to what the dangers might be, but some medical professionals advise against any sunscreens that include nanoparticles.  Make sure to check the label of your sunscreen and chose the best for your needs and comfort.  But by all means, wear some type of sunscreen!

There is also a second type of protection factor…this is the UV Protection Factor, or UPF.  This is a measurement usually associated with the ability of clothing to protect against UV exposure.  This is not measured by comparing burning skin to protected skin, but measured with UV detection equipment.  Basically, a known amount of UV rays are transmitted onto a surface, such as fabric.  On the other side of the fabric is a meter which detects UV rays.  For simplicity sake, let’s say 50 “rays” of UV was transmitted onto the fabric, and only 1 “ray” was detected to have gone through the fabric.  This ratio of 1/50 means that the fabric has an SPF rating of 50.  This also means that 49 out of 50 rays, or 98% of the rays were blocked.  This is an excellent rating.

A typical good UPF rating is 30, much like SPF.  This means that only 1 out of 30 rays penetrated the fabric, or that 29 out of 30, or about 97% of the rays were blocked!  So what is a good type of fabric that offers a good UPF rating?  There are three parameters to consider when seeking good UPF-rated clothing: material, weave or thickness, and color.

The best materials are nylon, wool, silk and polyester.  All of these materials are usually tightly woven.  Loosely woven attire of the same material obviously wouldn’t work as well.  It’s all about blocking the UV rays, and the more dense and thick the material, the better.  Color matters as well.  Darker colors such as black or navy blue are best.  Bleached material is generally thinner and thus allows more penetration.  So what’s the perfect summer shirt to block the rays?  A long-sleeved black wool sweater. 

Obviously not the most comfortable in hotter climates.

Luckily, lighter-weight apparel with a high UPF rating is more readily available.  Companies such as Coolibar, UVSkinz, Mott 50 and others specialize in such attire and are growing in popularity.  Additionally, discount stores such as Target and Walmart offer more selection of cooler nylon shirts with UPF ratings of 30 or higher.

Remember that regular clothing also offers UV protection even without having a specific UPF rating.  Wearing a t-shirt offers much better protection than no shirt at all.  However, be careful of wear and tear in older clothing.  Fabric that is stretched allows more rays to pass through, so chose a newer t-shirt over that old stretched out comfort shirt.  Also, make sure your shirt has been washed.  The act of washing and drying will shrink many fabrics, especially cotton, which causes the weave to become tighter. 

Did your mother ever put a shirt on you when you played under the sprinkler or visited the public pool?  Mine did, thinking that the shirt offered better and longer lasting protection that the sunscreen.  But guess what?  A wet t-shirt offers virtually NO protection from the sun.  It allows the fabric to stretch and spread out, thereby opening the way for a full onslaught of UV radiation.  Trust me; I had many a night smelling of Solarcaine after a day of wearing a t-shirt at the pool.

Finally, no sun protection, whether SPF or UPF, would be complete without a hat.  A ball cap might offer some protection to the face, but a full, wide-brimmed hat would be more preferred.  Many people simply forget to apply sunscreen to the back of their neck, so having that extra protection in the back adds an additional bit of sun protection security.

No matter your attire, be sun-safe and be aware.  Embrace your time in the sun; just stay protected when you do so.

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