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Aug

2009

Skin Deep - Confused by Sky-High SPFs? Take a Number - NYTimes.com

A sunscreen’s SPF, or sun protection factor, measures how much the product shields the sun’s shorter-wave ultraviolet B rays, known as UVB radiation, which can cause sunburn. It used to be that SPF topped out at 30. No more. These days, a race is on among sunscreen makers to create the highest SPF that R&D can buy.

If adequately applied, sunscreens with sky-high SPFs offer slightly better protection against lobster-red burns than an SPF 30. But they don’t necessarily offer stellar protection against the more deeply penetrating ultraviolet A radiation, or so-called aging rays.