Beach shades will not keep off the sun’s
deadly rays, the Daily Mail warned. The
newspaper said that a third of cancer-causing UV rays still reach
the skin even when people are in the shade.
This experimental research conducted in Spain involved placing a
UV sensor beneath a large beach umbrella. Although the umbrella
absorbed most of the direct UV radiation from the sun only 4
passed through, about 34 of the
diffuse radiation
reflected off surfaces or scattered by air molecules from around
the umbrella reached the area beneath it.
It should be pointed out that the research relied on complex
mathematical formulae, and the findings may be restricted to the
environmental circumstances, and the dimensions and material of the
umbrella used. In addition, no humans were actually involved in the
experiments, so direct damage to the skin was not demonstrated.
However, the researchers conclusions seem
appropriate: that an umbrella on its own does not offer total
protection from the sun. As such, it should be considered as an
additional physical barrier, and appropriate sunscreens with an
adequate SPF should also be used.
Where did the story come from?
The study was carried out by researchers from Universidad de
Valencia in Spain and the University of Tasmania in Australia.
Funding was provided by the Ministerio de Ciencia e
Innovacin, Spain. The study was published in
thepeer-reviewed
scientific journal Photochemistry and Photobiology.
The Daily Mail has clearly and accurately reported this
research.
What kind of research was this?
This experimental research was set up to develop a mathematical
model that could estimate a persons level of
exposure to ultraviolet light UV when they are under partial
cover for example, an umbrella. The researchers tested their
model by investigating how much UV penetrated a beach umbrella.
They measured both direct UV rays from the sun and diffuse UV,
which is reflected off surfaces or scattered by air molecules.
Excessive UV exposure is known to have several detrimental
effects on human health, damaging the skin and eyes, and increasing
the risk of skin cancers and cataracts. The main methods of UV
protection are physical barriers including manmade barriers such
as beach umbrellas, and natural barriers such as the atmosphere or
trees, and chemical and biological agents creams, sprays and
lotions.
What did the research involve?
The experiments were conducted throughout the midday hours, when
the sun was at its peak, in December, under cloudless skies in
Spain. For the physical test of their model, the researchers used a
white and blue coloured beach umbrella that was about five feet
wide 80cm radius and five feet high 150cm.
The researchers called their new mathematical model the
sky view factor model. The
calculations are complex but, essentially, the model mimics the
amount of UV a human body might receive when stretched out
underneath the centre of a beach umbrella.
The model was tested using the white and blue umbrella. The
amount of diffuse radiation that penetrated the shade of the
umbrella was measured using a device called a
shadowband, which blocked
all direct sunlight and only measured the UV from other sources. A
light sensor positioned under the middle of the umbrella also
measured how much UV could pass directly through the umbrella. They
measured the level of erythemal UV
radiation, the spectrum of UV radiation that
will cause redness to the skin.
Their experiments took into account the elevation of the test
site and the transmission of radiation reflected from the
ground.
What were the basic results?
The researchers say that their mathematical model agreed with
the measurements conducted with and without the beach umbrella.
They also say that the umbrella absorbed most of the direct
radiation, letting only 5 of it through.
However, the sensors at the bottom of the umbrella detected that
34 of the diffuse radiation from the
umbrellas surroundings penetrated the area
under the umbrella.
How did the researchers interpret the results?
The researchers say that the beach umbrella effectively blocked
direct radiation from the sun. However, diffuse radiation from the
surroundings, which accounts for about 60 of the UV involved in
causing damage to the skin, still reached the sensor under the
umbrella.
This model may help to determine the UV exposure to humans in
complex environments, and also how the physical characteristics of
the environment contribute to these loads.
Conclusion
The researchers conducting this study formulated a complex
mathematical model aimed at seeing how much UV light penetrates a
typical beach umbrella. Though the umbrella was found to absorb
most of the direct UV light that hit it, some radiation penetrated
the area under the sunshade from the surroundings.
Points to note:
The experiments rely on assumptions and mathematical formulae
that may have some degree of error.
These findings give some indication of how much UV radiation
may be able to penetrate a physical barrier, but this experiment
only tested a particular beach umbrella, and the accuracy of the
model may vary when applied to other physical obstructions. The
colour of the material, size of the protective shade and position
of the person beneath the shade may all have an effect. The
findings may also not be applicable to all materials, some of which
may be specially designed to have a higher level of UV protection
for example, certain swimsuits and sun-suits for babies and
children.
There are many complexities in the environment, including cloud
cover, pollution and the surface the umbrellas
erected on. The findings from this study may only apply to quite
specific settings.
These findings give no indication of how much actual UV damage
to the skin would be caused in different scenarios, for example if
a person also used sunscreen, as the experiment was not tested
directly in humans.
The conclusions made by the researchers seem appropriate: that
an umbrella on its own does not offer total sun protection. As
such,an umbrellashould be considered as
an additional physical barrier, and appropriate sunscreens should
still be used. These findings are of particular importance for
babies and young children, who are often sheltered under an
umbrella on a pushchair or pram, during which time they should be
doubly protected by a suitable sunscreen lotion.
Links To The Headlines
Peril under a parasol: Beach shades will not keep off the sun’s
deadly rays.Daily Mail, July 21 2010
Links To Science
Utrillas MP, Martnez-Lozano JA and
Nuez M.Ultraviolet
Radiation Protection by a Beach Umbrella. Photochemistry
and Photobiology 2010 86: 449-456