Keep Out Of The Sun

It is the ultraviolet B component of sunlight that is the most harmful, particularly in the causation of sunburn and skin cancer. Usually UVB is principally found in the midday summer sun, and hence protection from the sun is advised between the hours of 10 a.m. and 2 p.m., or 11 a.m. and 3 p.m. with daylight saving. You should observe a `solar curfew' at this time, if possible. Maximal amounts of UVB occur in mid summer.

The factors which influence the amount of UVB reaching the earth include:

(i) altitude

(ii) scattering by atmospheric water droplets (clouds)

(iii) reflection from surfaces such as snow, sand and water. In high altitudes there will be an increasing amount of ultraviolet light, with a 20 per cent increase at 1500 m. Skiers are well aware of the increased possibility of sunburn. Especially on clear sunny days!

Atmospheric particles will influence the amount of ultraviolet light but it is important to recognise that significant amounts of UVB can still occur even when there is some cloud cover or on hazy days.

Reflection is especially important from surfaces like sand and water. This is most apparent when people protect themselves from direct sunlight with the use of hats or beach umbrellas, but still burn because of reflected ultraviolet light.

Note that temperature is not mentioned. Ultraviolet light is neither hot nor cold. Days of 20∞C can be associated with as much UVB exposure as days of 35∞C. This fact is easils appreciated by observing charts of UVB measurement,which are included on the weather reports in summer in Australia. Irrespective of the daily temperature there is an increase in UVB in the middle of the day,although there is some variation in the absolute level reached. In the past, people used the term windburn to denote sunburn occurring on cool or cloudy days. In fact there is no such thing as windburn. It is just sunburn.

The principles of sun protection are as follows:

1)Avoid - unnecessary sun exposure between 10 a.m. and 3 p.m.
2)Block - effects of sunlight with protective clothing, widebrimmed hats, and sunglasses
3)Cover - up with sunscreens
4)Educate - children