recovery that scientists credit to the 1987 landmark agreement
known as the Montreal Protocol on Substances That Deplete
United Nations member countries, led to the phasing out of
substances linked to ozone depletion.
What is SPF? When shopping for sunscreens, consumers
will no doubt notice each bottle lists its SPF number. Numbers
tend to be as low as 4 or as high as 100. But what is SPF?
And what does it have to do with protecting the skin from the
sun’s harmful rays? According to the Skin Cancer Foundation,
SPF, which stands for sun protection factor, is a measure
of a sunscreen’s ability to prevent the skin against ultraviolet
B, or UVB, rays from the sun. The Skin Cancer Foundation
notes that SPF works in a way that might surprise even the
most devoted of sun worshippers. If it takes 20 minutes for
unprotected skin to start redding, then a sunscreen with an
SPF of 15 will theoretically prevent redding for 15 times lon-
the Skin Cancer Foundation notes that the SPF model does
spark some concern. For example, no SPF sunscreen, regardless
of its number, should be expected to remain effective for
longer than two hours without reapplication. In addition,
reddening of the skin is a reaction to UVB rays alone and indicates
little about any damage caused by ultraviolet A, or
UVA, rays. To protect themselves against both UVB and UVA
rays, the Skin Cancer Foundation recommends consumers use
only broad-spectrum sunscreens with an SPF of 15 or higher.
Wearing protective clothing, staying out of the sun between
the hours of 10 a.m. and 4 p.m. and reapplying sunscreen after
sweating or going into the water are other ways to protect
the skin from the sun’s harmful rays.
Did you know?
Various ingredients in many popular sunscreen can
enter the bloodstream after just one day of use, according
to a recent study published in the medical journal JAMA.
The study conducted by the Center for Drug Evaluation
and Research examined 24 healthy volunteers who
were randomly assigned to a spray or lotion sunscreen
that contained avobenzone, oxybenzone or octocrylene
or a cream sunscreen that contained the chemical ecamsule.
Volunteers applied their sunscreen to 75 percent of
cream had levels of ecamsule in their blood that are con-
sunscreen, especially those who used products that con-
benzone has been shown to be a common cause of contact
allergies. Oxybenzone is also being studied for its
potential connection to other conditions, including lower
testosterone levels in adolescent boys and shorter pregnancies
and disrupted birth weights in babies. However,
scientists who responded to the study warned that it
should not prevent people from applying sunscreen, as
the Skin Cancer Foundation notes that more Americans
are diagnosed with skin cancer each year than all other
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