With the damaging effect of CFCs and other gases on the ozone layer it is really important that we protect ourselves from the increased amount of ultra violet radiation that reaches the surface of the Earth.
You have to be careful not only of direct
ultra violet light but also that reflected onto you. For example, snow reflects 90% of the UV
light that falls on it. That is why you can get snow blindness and severe sunburns from skiing
on a sunny day. Sunbathing on a beach can also give you extra UV exposure because sand
can reflect up to 20% of UVB that hits it.
Many types of glass are good absorbers of
UV – you can't get a suntan if you are in a glass greenhouse although you may get very
hot!
To stay safe in sunlight it is sensible to put on a sunscreen – either a cream or a lotion. Sunscreens are designed to
reduce the amount of UV hitting your body by absorbing, reflecting or scattering the incoming
radiation. Clothes will also block ultra violet radiation although thin white shirts will allow
some of the UV through. Most sunscreens use chemicals that have the same UV absorbing
properties.
Sunscreens are labelled with a sun protection
factor (SPF) number. This number only applies to the UVB (screening) action of
the sunscreen. If you are a normal pale skinned person using a sunscreen with a SPF15 you
can spend fifteen times longer in the sun before becoming sunburnt than you would without
the sunscreen.
Remember that the SPF does not apply to UVA sunscreens so even
a sunscreen with a SPF25 but with no UVA screen will less effective than a sunscreen with a
lower SPF but with a UVA screen as well. When choosing a sunscreen it is best to use one
that has a high SPF factor and both a UVA and UVB block. This is called a broad-spectrum sunscreen. You should also apply the sunscreen
half an hour before going out in the sun and put more on regularly especially if you are going
to swim, when some of the it may wash off. The effects of UV are more damaging at altitude
so wear sunscreen in the mountains even on days where there is thin cloud. A typical white
T-shirt has an SPF of about 3 but if treated with colourless dyes this can be increased to
about 30.
A sunblock is considered to be any
sunscreen with an SPF of 15 or more. In theory, an SPF 15 sunscreen may absorb more
than 92 percent of incident UV radiation. Sunblock with an SPF of 30 blocks 97% of sun-
burning rays, while an SPF of 2 blocks 50%.
Stay in the shade between 11am and 3pm
Use a sunscreen with
an SPF of 15 or more
Don't rely on sunscreen alone
Wear a wide-brimmed hat and
tight woven clothes that cover your arms and legs
Wear sunglasses that block UV light
to protect your eyes
Reapply the sunscreen every hour or so
Remember that
rubbing your face will rub off some of the sunscreen
If on the beach, wear sun-protective
clothing, including swimsuits and wetsuits
Remember to take extra care with children
and people with fair skin
Try never to get sunburnt as sunburn causes permanent
damage
Ultraviolet light stimulates the production melanin in the skin which gives it
its tanned colour but if you are in the sun too long this can turn into a sunburn. Sunscreens are
made of zinc oxide (which blocks both UVA and UVB) or PABA (para-aminobenzoic acid) which
absorbs only UVB.