[pct-l] sun protection

[edmond at mydogmeg.net (Edmond Meinfelder)]

At 04:54 PM 1/27/2004 -0500, Christopher Willett wrote:
>I haven't had any problems with the reflected light of a white shirt, and
>my face was still pale when I got to KM.  I wore a big sun hat.  I didn't
>have to use sunscreen
>in SoCal but with all the snow in the Sierras,

I agree the sun in the Sierra in June or earlier is harsh. First, you are 
at elevation, making the sun's more intense (passing through less 
atmosphere) and second the snow, ice, granite and water act like mirrors.

Sand typically reflects only 1/3 of UVB (ultraviolet beta radiation which 
is associated with skin cancer) while snow, water and ice can reflect up to 
100%. Also UVB rays increase roughly 3% for every 1,000 feet in elevation. 
Therefore at Forester Pass, you're getting roughly 39.6% more UVB than you 
would be at the beach.

>I've been told that a regular, cotton T-shirt is about SPF 15.

The SPF of clothing varies with the shirt's fiber, weave, thread, color and 
water content. Typically cotton t-shirts are well under 10; 15 is not 
impossible, but typically this is not the case. The American cancer Society 
pegs cotton t-shirts  as having an SPF of 5:

http://www.cancer.org/docroot/SPC/content/SPC_1_Sun_Protection_Ratings_For_Summer_Clothes_and_Fabrics.asp

>heard a normal number for a polyester shirt, but I would suppose that it
>would be about the same.  Unless you are hypersensitive to the sun, I
>would guess that SPF 15 would be fine.

Different fabrics have different properties. Generic polyester has a much 
better SPF than cotton. A polyester shirt of a similar weave to a typical 
cotton shirt (SPF 6), will likely have an SPF higher than 20. Though 
treated fabrics are much higher, like 50.

Back to shirts, I am partial to the RailRiders Eco-Mesh shirt:

http://www.railriders.com/store/Men_s___ShirtsECM?

It's supplex nylon and the company claims it's SPF equivalent is around 30.

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