Most people are now aware that excessive
exposure to the sun and sunburn can lead to skin problems, some as
serious as skin cancer. Sunburn should always be avoided and
especially so with children. Unfortunately many people assume that a
T-shirt is good enough for protecting their or their children's skin
from the sun, but sadly this is often not the case. Most clothing
offers some form of sun protection but this is generally not
adequate to provide sufficient protection against UV radiation. A
typical summer T-shirt would probably offer a UPF rating of
somewhere between 7 and 15 +, much less when wet ,significantly
below the minimum recommended levels. The sun's rays are strongest
between 10 a.m. and 4 p.m. Whenever possible, limit exposure to the
sun during these
hours.
Understanding the Jargon
What is UVR? UVR Stands for Ultraviolet Radiation and
is present in sunlight. UVR is classified as UVA, UVB and UVC. Over
exposure to solar radiation can cause skin damage and an increased risk of
developing skin cancer. The most obvious short term effect of
over-exposure to UVR is sunburn. Cumulative exposure to UVR particularly
during childhood increases the risk of cancer development as an adult
What is UVI? UVI stands for Ultraviolet Index and
measures the highest UVR level reached each day at a particular location.
The ozone layer shields the Earth from harmful UV radiation. Ozone
depletion, as well as seasonal and weather variations, cause different
amounts of UV radiation to reach the Earth at any given time. Developed by
the National Weather Service (NWS) and EPA, the UV Index predicts the next
day's ultraviolet radiation levels on a 1-11+ scale, helping people
determine appropriate sun-protective behaviors.
What makes a good sun protective
garment?
Composition of the
fabric Different fibres have different
natural UVR absorbing properties.
Weave Density
The tighter the weave the higher the
level of Sun Protection. The combination of high UVR absorbing
fibres and a tightly woven fabric creates a good sun protective
garment.
E.g.: Loosely woven light cotton T-shirt
will have a lower sun protection to a tightly woven lycra.
Tension Well fitting garments are very important.
Over stretching may decrease the UPF rating, in the same way
that a lycra suit that is too tight will degrade more quickly in
chlorine.
Moisture
Content Some fabrics have a lower rating
when wet. Dependent on the type of fabric and the amount of
moisture absorbed. E.g.: A cotton T-shirt will absorb a lot of
moisture vs a nylon/elastane sun top which does not absorb moisture
at all. The nylon/elastane will maintain it's UPF rating when
wet whilst a cotton T-shirt will not.
Design The more body coverage the greater the sun
protection.
Colour Whilst certain dyes can absorb more UVR, the
fibre content and weave density is more important. E.g.: A
White nylon/elastane shirt can have a much higher rating then a
Black cotton voile shirt.
Condition Old, worn, threadbare or faded garments may
have a low UPF rating.
UPF Scale
This is the maximum Ultraviolet Protection Factor
accorded to sun protection clothing by Australian, New Zealand and US
Government rating agencies. The UPF rating indicates how much Ultraviolet
Radiation is absorbed by the fabric. For example a fabric with a UPF
Rating of 50 only allows 1/50th of the hazardous ultraviolet radiation
falling on the surface of the fabric to pass through it - or expressed
another way, the fabric blocks 98% of the sun's harmful UV Rays. This
means that, where it is protected by the fabric, the fabric will reduce
your skin's exposure to ultraviolet radiation by twenty times. Not to be
confused with SPF which is applied to sunscreens to measure the amount of
protection provided against UVR.
The new UPF fabric rating also requires that
fabrics claiming to be sun protective must be prepared in the following
ways before testing:
Undergo 40 simulated launderings
Be exposed to 100 fading units of
simulated sunlight (equivalent to 2 years light exposure)
And, if intended for swim wear, exposure to
chlorinated water
SPF Scale
SPF stands for Sun Protection Factor.
The number is determined experimentally indoors by exposing humans to a
light spectrum meant to simulate midday sun. Some subjects wear sun cream
and others do not. The amount of light that induces redness in sun cream
protected skin, divided by the amount of light that causes redness in
unprotected skin is the SPF. It is mainly a measure of UVB protection and
ranges from 1 to 45 or above.
A sunscreen with an SPF of 15 filters 92% of the
UVB. Put another way, a sunscreen with an SPF of 15 will delay the onset
of a sunburn in a person who would otherwise burn in 10 minutes to burn in
150 minutes. The SPF 15 sunscreen allows a person to stay out in the sun
15 times longer.
There is currently no uniform measure of UVA
absorption. There are broad-spectrum sunscreens that protect against UVA
and UVB radiation although it is important to remember that the SPF does
not predict UVA protection. The UV Index is a public health education tool
reported by meteorologists. It offers a daily report of UV light levels on
a scale from 1-10+.
The "protectiveness" of clothing can also be
measured by SPF. The following are SPF's of various types of clothing:
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