The Trail Companion
Good Day, Sunshine: Staying Safe in the Sun
by Geoffrey Skinner
Many of us escape to
the outdoors whenever possible, especially in the
summer, when the weather invites hikes, rides, and
backpacking trips to the mountains, along with
visiting the beaches, swimming, etc. As a child, I
spent hours under the California sun with few clothes
on, let alone sun block, and was tanned a dark brown
every summer. These days, however, very few of us are
likely to spend long outside without some sort of sun
protection. News about the thinning ozone layer and
general warnings about skin damage from the sun's
rays abound. The "healthy" tan no longer has appeal
it once did; even Doonesbury's Zonker long ago left
the world of tanning competitions. With that in mind,
I don't wish to simply admonish against going out in
the sun, but explore the options and the science of
Why UV radiation is a concern
radiation from the sun comes in three flavors: UVA,
UVB and UVC, all of which are harmful to unprotected
skin. UVA has a wavelength just slightly shorter than
visible violet light (320-400 nanometers) and is not
blocked by the ozone layer. UVA has the potential to
penetrate the most deeply into the skin. UVB is the
next shorter wavelength (280-320 nm) and is partially
blocked by the ozone layer. UVB is the most dangerous
for humans (and other organisms) and can cause DNA
damage and skin cancers. UVC has the shortest
wavelength (shorter than 280 nm) and is also harmful,
but fortunately, UVC is completely absorbed by the
ozone layer and ordinary oxygen. Altogether, the
ozone layer and stratospheric oxygen absorb 97-99% of
UV radiation shorter than 300 nm.
light-skinned people, reducing and preventing
exposure to UVB radiation is important for long-term
health, particularly as the ozone layer continues to
thin. A small increase in the amount of UVB radiation
will cause a large increase in the number of basal
and squamous-cell carcinomas; some researchers
estimate that 90% of skin carcinomas are attributable
to UVB exposure. Fortunately, most are easily
treatable and rarely fatal if detected early.
Melanoma growth appears to be correlated to brief,
high-intensity exposure (as long as 10-20 yr. before
its appearance!) and the link is indisputable between
UV exposure of all varieties and premature aging of
the skin. Even mild tanning alters the skin DNA and
damages the connective tissues. There is no such
thing as a safe tan!
In addition to skin
damage, UV light can damage the eyes, particularly
the cornea, which is a good UV absorber. High doses
can cause temporary clouding of the corneas, which is
the cause of "snow-blindness." Even more insidiously,
ultraviolet radiation can suppress the immune system,
which plays a part in skin cancer growth, but may
also be a factor in the body's ability to fight off
How much UVB you
absorb depends on several factors, including latitude
and elevation, cloud cover and proximity to an
industrial area. The higher the elevation, the
thinner the atmosphere above you, and so the more UVB
will strike you. The closer you are to the equator
(or to the summer solstice), the more direct the
sun's rays, likewise increasing exposure. Cloudy
skies will absorb a significant portion of UVB - as
much as 50% or more on rainy or substantially
overcast days (partially or variably cloudy days do
little to reduce exposure). Photochemical smog
containing ozone also reduces the amount of UV
radiation, which may help explain why the great ozone
losses over the southern hemisphere have not been
mirrored in the northern one.
If we didn't all
enjoy the outdoors, staying out of the sun might seem
a reasonable solution, but for many of us, including
me, an all-day jaunt in the mountains or a trip to
the beach are pleasures which we would be loath to
forgo entirely. Fortunately, a number of simple steps
are available to allow us to continue our days
outdoors in relative safety.
- Wear sun-protective clothing.
Any clothing will help protect against the sun, but
the tighter the weave, the better. One rule of
thumb is to check the amount of light that you can
see through the fabric. Some clothing is marketed
as incorporating special sun-protective fabric with
an SPF (Sun Protection Factor) of 30 or more. In
general, minimize the amount of bare skin as much
as possible. A loose fit also helps by preventing
rays from passing directly through the fabric and
into your skin.
- Wear a hat. The neck, ears and
face and eyes are particularly vulnerable to sun
damage. Wide brimmed hats (3" or more) offer the
greatest protection. Baseball caps may be
comfortable, but don't shade very much of the head.
In Australia, where the periodic hole in the ozone
layer allows large amounts of UV radiation to hit
the earth, wide brimmed hats (and sunglasses) are
mandatory parts of school uniforms.
- Wear sunglasses. Make sure
that your sunglasses will block UV rays. Look for
peel-off labels stating the amount of blockage;
although any glasses (including ordinary glasses)
will block some UV, a rating of 100 is best.
Sunglasses lacking a label won't necessarily block
a significant portion.
- Use sunscreen on unprotected
skin. A sunscreen with an SPF at least 15
will block most UV, although it must be applied
liberally and reapplied every two hours if you are
working, exercising or playing outdoors. Even
waterproof sunscreen can be wiped off by toweling
after swimming. The effectiveness of sunscreen
greatly depends on your skin type.
- Avoid unnecessary exposure to UV
radiation. Stay away from tanning parlors
and sun lamps. There is no safe tanning. Pay
attention to the UV Index if it is available in
newspapers or on TV. This index developed by the
Environmental Protection Agency rates UV radiation
from 1-15, with anything 10 or higher considered as
extremely high. Also consider cloud cover and time
of year if the UV Index is not available.
- Finally, stay out of the sun at peak
hours. UV radiation is most intense in the
six hours closest to noon (or 1 p.m. during
daylight saving time). The amount of radiation at
10 a.m. and 4 p.m. is half that of 1 p.m. DST.
Schedule your outings for mornings or evenings - in
addition to reducing sun damage, you may be
rewarded by lower temperatures and more wildlife
sightings. Siestas have a lot going for them.
For more information
about protecting yourself from sun while still
enjoying the outdoors, you may wish to call or write
some of the following federal agencies which have
information on the effects of UV exposure, UV
protection and related issues. Public inquiry
telephone numbers are provided where available.
NOAA/National Weather Service National Meteorological Center
Washington, DC 20233
(for information on Experimental UV Index)
National Institute for Occupational Safety and Health (NIOSH)
EPA Stratospheric Ozone Information Hotline
Centers for Disease Control and Prevention
National Center for Chronic Disease Prevention and Health Promotion
Division of Cancer Prevention and Control
4770 Buford Highway NE,
Be Sun Wise! Program
401 M Street SW (6205J)
Washington DC 20460
Cancer Information Service
National Cancer Institute
dermatologist or local hospital/clinic should also be
able to provide you with more detailed information on
sun protection and preventing skin cancer.
The Experimental Ultraviolet Index factsheet.
Action steps for sun protection. EPA,
Ultraviolet radiation. NASA, 1999.
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