Shedding light on sunscreens
The sun protection factor (SPF) you see on the label of sunscreens
is misleading. It’s not a measure of total sun protection but
of protection against sunburn from UVB light. The longer light waves
in the ultraviolet A (UVA) part of the spectrum actually penetrate
deeper into the skin and may even cause more harm than sunburn-producing
UVB. Moreover, the main part of the UVA spectrum passes through glass,
and UVB doesn’t, so you may be exposed to UVA in a car and indoors.
Sunscreens that claim to block both UVA and UVB light are increasingly
popular. But currently there’s little FDA regulation of those claims.
If companies can show their lotions absorb or block even just a little
bit of UVA light (and they are free to design the tests) they’re
allowed to label them as “broad spectrum” sunscreens and
even as sunblocks. Some dermatologists reserve the term sunblock for
lotions with ingredients that physically block light from penetrating
the skin, such as zinc oxide or titanium dioxide. The FDA has proposed
regulations that would go further and ban the term altogether. But those
regulations have languished in the proposal stage for six years, and
there’s no immediate prospect of them becoming law soon.
So if you’re looking for UVA and UVB protection, don’t pay
too much attention to the front of the bottle. Inspect the fine print
on the back. The active ingredients with the best reputation for fending
off UVA light are avobenzone (Parsol 1789), titanium dioxide, and zinc
But it’s not quite that simple. Some researchers see a problem
with avobenzone. In experimental situations it breaks down in sunlight — not
a good attribute for a sunscreen ingredient.
Therefore, the lotions containing zinc oxide and titanium dioxide may
be the best bet. The particles are very fine, so they’re not like
the white zinc oxide that lifeguards paint their noses with. Still, some
find these lotions gritty.
Regardless of which sunscreen you use, slather the stuff on. People
rarely use enough to get the lotion’s full protection.
July 2005 Update
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