Sun
Protection in the Tropics
The sun just
doesn't seem stronger in the tropics - it is! And sun protection is vitally important -
especially for children and young adults.
Fortunately, sun protection can be obtained in a number of different ways - clothing,
chemical sunscreens (and sunblocks), and simply staying out of the sun. For most
people (including children), a combination of all three works best in the tropics.
Ultraviolet Radiation: The
sun produces ultraviolet radiation (UVR) that gives us light to see, warmth, and fuel for
the growth of plants.
UVR has 3 different
bands - UVA, UVB and UVC. Very little UVC reaches the earth's atmosphere. UVB is the
strongest band and causes most sunburns. UVA is weaker than UVB, but about 100 times more
UVA than UVB rays reach the earth's surface, meaning UVA protection is still important.
Skin cancers,
cataracts and 90% of visible aging (wrinkles) are caused primarily by UVB and UVA rays.
Sunburn is caused primarily by UVB rays.
The risk of skin
cancer is believed to double for people who receive just one or two severe sunburns during
childhood. In fact, researchers believe that 80-90% of the skin damage that causes
wrinkles and skin cancer is received before the age of 18.
Sunburn shows
damage to the skin caused by UVB rays. However, just because the skins shows no visible
signs of a burn does not mean it is not being damaged by the sun.
SPF Ratings: The SPF (or sun
protection factor) measures the amount of sun protection provided against UVB rays ONLY.
SPF does NOT measure the amount of protection provided against UVA rays. The SPF rating
indicates how much longer it takes to get a sunburn using the sunscreen than it would
without using the sunscreen. For example, an SPF rating of "2" means it takes
twice as long to get a sunburn, a rating of 10 means it takes 10 times as long.
The Ozone Layer: Ozone is the gas that filters
UVB rays from the atmosphere (ozone does not filter UVA rays). The size of the ozone layer
(and the protection it provides from UVB varies based on the time of day, location, season
and altitude).
The ozone layer is at its thinnest
in the tropics (UVR levels are 1,000 times higher at the equator than at the North or
South Poles).
The ozone layer is also thinner
during the summer and fall, and from 10 a.m. to 2 p.m.
Sand increases the intensity of
UVRs by reflecting back most of the UVRs that reach the earth's surface - intensity can be
increased by as much as 80%.
Surprisingly, water reflects very
little UVR and cloud cover reduces UVR that reaches the earth's surface - but the amount
of protection is determined by the density of the cloud cover.
The ozone layer provides much less
protection for UVR at high altitudes
Clothing:
As with sunscreens, sun protection from UVB rays provided by clothing
and fabrics is expressed in terms of an SPF rating.
Research on clothing and UVR
protection has found that:
- One hundred percent (100%) polyester has the
highest SPF of all fabrics, providing 2 to 3 times more sun protection that any other
fabric.
- Darker colored clothing has a much higher SPF than
light colored clothing (black clothing provides 5 times more protection than white
clothing - a white T-shirt has only a 5 SPF rating).
- Knits have a higher SPF than woven fabrics, and
nylon spandex knits have a very high SPF, regardless of color.
- The heavier the weight of the fabric, the higher
its SPF. A double layer of fabric almost doubles the SPF of clothing. This is true
regardless of fabric type (the same for cotton, silk and polyester, for example).
- More tightly woven fabrics help reduce UVR
transmission to the skin, but not as effectivley as heavier-weight fabrics.
- Wet fabrics INCREASE the amount of UVR that reaches
the skins - by as much as one-third.
What does this all mean for clothing in the
tropics?
1. In very hot weather, wear
loose fitting, tightly woven clothing. The folds of loose fitting clothing provides
sort of a "double layer" of fabric, thereby doubling the SPF of the clothing.
The tight weave helps reduce UVR transmission when it's too hot for more effective
heavier-weight fabrics.
2. When snorkeling or
swimming for long periods, wear a dark-colored t-shirt for extra sun protection.
Not only does a light-colored t-shirt offer limited SPF protection, the fact that it's wet
INCREASES the UVR that reaches the skin, rather than DECREASING it.
3. Put on dry clothes (or at
least cover-up) after swimming and snorkeling.
4. Wear a cover-up on the
beach since UVR rays are intensified by the sand.
Important: Never use sunscreens of any kind on babies less than 6 months old. Test
sunscreens for allergic reactions in children by applying the sunscreen to a patch of
skin. Baby oil does NOT contain sunscreen.
Sunscreens are either
"organic" or "inorganic" (inorganic sunscreens are also called
"physical" sunscreens). "Organic" does NOT mean the sunscreens are
naturally produced. Rather, an "organic" sunscreen is one which is composed of
carbon and hydrogen (among other things).
Organic sunscreens are absorbed into the skin to
some extent. PABA (para amino benzoic acid) is the most famous sunscreen because of the
allergic reaction it causes in so many people. Many people are also allergic to the common
organic sunscreen Benzophenone (Oxybenzone).
Most organic sunscreens block only UVB rays. For
UVB protection, SPF 15 is adequate for most skin types since an SPF 15 sunscreen blocks
95% of UVB rays while an SPF 30 sunscreen stops only about 2% more (97%).
Inorganic or physical suncreens are really
microscopic solid pieces of sunscreen - the most common being zinc oxide and titanium
dioxide. Most physical sunscreens are now microfine and with particles so small they
cannot be seen (unlike the thick white paste of past lifeguard movie fame). Zinc oxide is
generally considered very safe and causes very few allergic reactions.
Titanium dioxide blocks some UVA and zinc oxide
blocks more UVR than any other single ingredient. No sunscreen will completely block UVA
rays.
Tips on Choosing a Sunscreen:
- Don't rely simply on statements of
"protection" against UVA since some researchers believe many of these sunscreens
only offer an SPF of 3 or 4 for UVA rays, even if the SPF is much higher for UVB rays.
Instead, look for a sunscreen labeled "broad sprectrum" that contains zinc oxide
and has a minimum SPF rating of 15.
- Apply sunscreen about 20 minutes before sun
exposure to allow it time to "set up" on the skin. Reapply every two hours when
swimming or sweating.
- Use at least 1 full ounce of sunscreen per adult
per application (SPF ratings are based on this amount). Using a smaller amount of SPF 30
does NOT equal a greater amount of SPF 15!
- SPF Sunscreen Recommendations based on skin type:
- Type 1 (always burns, never tans): 30 SPF
- Type 2 (usually burns, tans with difficulty): 20
SPF
- Type 3 (sometimes burns, sometimes tans): 15-20 SPF
- Type 4 (burn minimally, always tans): 15 SPF
- Type 5 (rarely burns, tans profusely): 15 SPF
- Type 6 (never burns, deeply tans): 15 SPF
- Other sunscreen tips:
- Pay special attention when applying sunscreen to
your ears, nose, shoulders and tops of feet.
- When snorkeling, pay particular attention to the
back of the calves and thighs.
Hats: Hats
should have at least a 3" brim all the way around. Baseball caps or visors offer
limited protection to the neck and ears. However, a baseball cap brim will shelter the
eyes from about 50% of the sun's rays.
Sunglasses: Sunglasses are manufactured in accordance with ANSI (American
National Standards Institute) standards and fall within the following 3 categories:
1. Cosmetic use: blocks at least 70% UVB, 60% UVA
2. General use: blocks 95% UVB, 60% UVA
3. Special Purpose Intense Sunlight: blocks 99%
UVB, 98% UVA
For tropical use, only buy sunglasses rated
"Special Purpose Intense Sunlight." If the glasses aren't labeled, don't buy
them. Sunglasses should fit tightly to block UVR from the sides and have lenses large
enough to cover the entire eye area, including eye lids.
Color is irrelevant in terms of UV ratings (UV
coating is clear, and doesn't affect the color of the sunglasses).
Polarized sunglasses cut down glare, but don't
block UV rays. Always look for the ANSI rating - even on polarized sunglasses.
At present, UV aborbing contact lenses do not have
enough UV protection.
When possible, avoid the sun from 10 a.m to 2 p.m.
when the ozone layer is weakest - and UVR the strongest.
Avoiding the sun doesn't necessarily mean staying
indoors, however. If on a boat, use the bimini top. Seek out shade on the beach (to avoid
the intensification of UVR by the sun's reflection off the sand).
Take a break and have lunch in a shady spot or an
air-conditioned restaurant.
Commons 