Master Sayantan Mahapatra
Biology Project On Ultraviolrt Rays
2013- 2014
In the present 21st century world, one does not need to
say about ultra violet rays, it is the most ignited topic in
this era. From the common man to the Academicians, UV
rays hold an important place in their debate.
JNV,KAPASAREA,EAST MEDINIPUR
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BIOLOGY PROJECT ON ULTRAVIOLET
RAYS
SUBMITTED BY :
Master Sayantan Mahapatra
GUIDED BY :
Mr.R.K.Sahoo(PGT,Biology)
CLASS : XII PCMB
YEAR : 2013-2014
ROLL NO. : 12
SCHOOL : JAWAHAR NAVODAYA
VIDYALAYA ,KAPASAREA, EAST
MEDINIPUR,WEST BENGAL
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Certified to be the bonafide work done by
Master. Sayantan Mahapatra of class XII – A
in the Biology LAB during the year 2013-2014
Date _____________.
Submitted for JAWAHAR NAVODAYA
VIDYALAYA,KAPASAREA,EAST MEDINIPUR
Examination held in BIOLOGY LAB at JAWAHAR
NAVODAYA VIDYALAYA,KAPASAREA,EAST
MEDINIPUR
EXAMINER
DATE : ___________
SEAL
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Acknowledgement
I would like to express my sincere gratitude
to my biology mentor
Mr.R.K.Sahoo(PGT,Biology)
for his vital support, guidance and
encouragement – without which this project
would not have come forth. I would also like
to express my gratitude to my old bio teacher
Mr. Shubhendu Bagchi (PGT,Biology) for his
support during the making of this project
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INTRODUCTION
In the present 21st century world, one does not need to say about ultra
violet rays, it is the most ignited topic in this era. From the common
man to the Academicians, UV rays hold an important place in their
debate.
UV rays have been discussed for a long time all around the world
especially after the discovery of the hole in the ozone layer in
1990s.The hole meant the approaching slow death of our mother earth.
A host of studies on this topic has been undertaken by many people
and organizations such as the United Nations, Green Peace, etc.
At the United Nations Conference on Environment
and Development (UNCED) in 1992, it was declared under Agenda 21
that there should be activities on the effects of UV radiation. In
response to Agenda 21, WHO in collaboration with the United Nations
Environment Programme, the World Meteorological Organization, The
International Agency on Cancer Research and the International
Commission on Non-Ionizing Radiation Protection set up Intersun, The
Global UV Project.
Even when the whole world only speaks about this great calamity that
has befallen on our mother earth, it would surely be a great injustice
on part of the young generation as this slow killer is growing old with
the young generation and they are the one who should live on this
earth with this growing menace. Thus taking into consideration of
these points, this project has been taken up not only to know about UV
rays but also how it affects the bio diversity of our planet and how its
effect can be minimized.
Here, this project deals with the above mentioned points. Also the
project aims to give a comprehensive picture on the impending
disaster that would take place if we be ignorant on this issue.
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CONTENTS
1) ULTRAVIOLET RAYS
1.1) Sources of UV rays
1.2) UV-A, UV-B & UV-C
2) EFFECTS OF UV RADIATION ON NATURE
2.1) Damage to marine life
2.2) Degradation of polymers, pigments and dyes
3) HARMFUL EFFECTS ON HUMANS
3.1) Effects on Eye
3.2) Effects on Skin
3.3) Genetic effects
3.4) Effects on immune system
4) OZONE DEPLETION AND UV RADIATIONS
5) VULNERABILITIES DUE TO UV RADIAT1ONS
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ULTRAVIOLET
RAYS
In 1801, the German Physicist Johann Wilhelm Ritter, found that there
is existence of some invisible rays beyond the violet end of the visible
spectrum of the light. Those invisible rays darken silver chloride even
more efficiently than visible light. This spectra region between visible
light and X-rays was found to be more chemically active than visible
light, and was named as the ultraviolet region.
Ultraviolet (UV) light is electromagnetic radiation with a wavelength
shorter than that of visible light, but longer than x-rays, in the range of
10 nm to 400 nm, and energies from 3 eV to 124 eV.
The name Ultra Violet means “beyond violet” (from Latin ultra, =
“beyond”). Violet, being the colour of the shortest wavelengths of
visible light, UV light has even shorter wavelength than that of the
violet light. The electromagnetic spectrum of ultraviolet light can be
subdivided in a number of ways. The draft ISO standard on determining
solar radiances (ISO-DIS-21348) describes the following ranges:
Name
Abbreviation
Wavelength range in Energy per
nanometers
photon
Ultraviolet A, long
wave, or black light
UVA
400 nm–320 nm
3.10–3.94
eV
Near
NUV
400 nm–300 nm
3.10–4.13
eV
Ultraviolet B or
medium wave
UVB
320 nm–280 nm
3.94–4.43
eV
Middle
MUV
300 nm–200 nm
4.13–6.20
eV
Ultraviolet C, short
wave, or germicidal
UVC
280 nm–100 nm
4.43–12.4
eV
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Far
FUV
200 nm–122 nm
6.20–10.2
eV
Vacuum
VUV
200 nm–10 nm
6.20–124 eV
Extreme
EUV
121 nm–10 nm
10.2–124 eV
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 SOURCES OF UV RAYS
The Sun emits ultraviolet radiation in UV-A, UV-B, and UV-C bands. The
Earth’s ozone layer blocks 98.7% of this UV radiation from penetrating
through the Earth’s atmosphere. 98.7% of the ultraviolet radiation that
reaches the Earth’s surface is UVA.
Other sources: There are also several artificial methods to produce
UV rays such as from black light (Wood’s light), Ultraviolet fluorescent
lamps, Ultraviolet LEDs, Ultraviolet lasers, synchrotron radiation
sources, Argon and deuterium discharge lamps etc.
UV-A, UV-B & UV-C
Among the different types of UV rays, we consider the main subdivisions as
UV-A, UV-B & UV-C.
UV-A (320-400 nm):Ultraviolet light,
type A. These are rays of light from the sun which are not visible but can
cause damage to the skin.
UV-B (280-320 nm):Ultraviolet light, type B.
These are rays of light from the sun which are not visible but can cause
damage to the skin.
The amount of UV-B light received by a location is strongly dependent on:-
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
Latitude and elevation of the location: -
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At high-latitude Polar Regions, the sun is always low in the sky. So the
sunlight passes through atmosphere and most of the UV-B rays are
absorbed. For this reason, average UV-B exposure at the poles is over
a thousand times lower than at the equator.
Cloud Cover: -
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The reduction in UV-B exposure depends on the thickness of cloud
cover.
Proximity to an industrial area: Due to the protection offered by photochemical smog, industrial
processes produce ozone, one of the most irritating components of
smog. So it absorbs UV-B. This is thought to be one of the main
reasons of ozone losses in the southern hemisphere. The loss has not
been mirrored in the northern hemisphere.
UV-C (100-280 nm): UV-C rays are
highest energetic and most dangerous type of ultraviolet light. Exposure to it
can even lead to death. Little attention has been given to UV-C rays in the
past since they are filtered out by the atmosphere. However, their use in
equipment such as pond sterilization units may pose an exposure risk, if the
lamp is switched on outside of its enclosed pond sterilization unit.
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EFFECTS OF UV RADIATION ON NATURE
The effects of UV radiation on earth’s ecosystems are not completely
understood. Even isolating the effects of UV-A versus UV-B is
somewhat arbitrary. Studies have shown that increased UV radiation
can cause significant damage, particularly to small animals and
plants. Phytoplankton, fish eggs, and young plants with developing
leaves are particularly susceptible to damage from over exposure to
UV.
Solar UV
radiation levels are highest during the middle of the day. In total,
almost half the daytime the total UV radiation is received during the
few hours around noontime. The sunlight reaching us consists of
approximately 0.5% of UV-B radiation in terms of radiant energy.
Clouds, as well as ozone have a tremendous affect on UV radiation
levels. However, cloudy skies generally do not offer significant
protection from UV. Thin or scattered clouds can have minor impacts
on UV and even, for a short time increase in UV, it would be on a blue
sky day by further scattering the radiation and increasing the levels
that reach the surface.
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DAMAGE TO MARINE LIFE
The penetration of increased amounts of UV-B light has caused great
concern over the health of marine plankton that densely populates the
top 2 meters of ocean water. The natural protective response of most
chlorophyll containing cells to increased light-radiation is to produce
more light-absorbing pigments but this protective response is not
triggered by UV-B light. Another possible response of plankton is to
sink deeper into the water but this reduces the amount of visible light
that they need for photosynthesis, and thereby reduces their growth
and reproduction rate. In other words, the amount of food and oxygen
produced by plankton could be reduced by UV exposure without killing
individual organisms
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DEGRADATION OF PIGMENTS, POLYMERS AND DYES
Many polymers used in consumer products are degraded by UV light.
The problem appears as discoloration or fading, cracking and
sometimes disintegration of total product, if cracking has proceeded
sufficiently. The rate of attack increases with exposure time and
sunlight intensity. It is known as UV degradation, and is one form of
polymer degradation. Sensitive polymers include thermoplastics, such
as polypropylene and polyethylene as well as special fibres like
Aramids.
There are several other considerations:

Ultraviolet levels are over 1,000 times higher at the equator than
at the Polar Regions so it is presumed that marine life at the
equator is much better adapted to the higher environmental UV
light radiation than organisms in the Polar Regions. The current
concern of marine biologists is mostly over the more sensitive
Antarctic phytoplankton which normally would receive very low
doses of UV. Only one large-scale field survey of Antarctic
phytoplankton has been carried out so far [Smith et.al
_Science_1992]; they found a 6-12% drop in phytoplankton
productivity in Antarctica. Since the hole only lasts from 1012weeks, this translates into a 2-4% loss overall, a measurable
but not yet a catastrophic loss.
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Both plants and phytoplankton vary widely in their sensitivity to
UV-B. When over 200 agricultural plants were tested, more than
half of them showed sensitivity to UV-B light. Other plants
showed a small increase in vigor or even negligible effects. Even
within a species there were marked of differences. For example,
one variety of soybeans showed a 16% decrease in growth while
another variety of the same soybean showed no effect [R.
Parson]. An increase in UV-B could cause a shift in population
rather than a large die-off of plants.
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
An increase in UV-B will cause in production of Ozone at lower
levels in the atmosphere. While some have hailed the protection
offered by this ‘pollution-shield’. Many plants have shown
themselves to be very sensitive to photochemical smog.
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HARMFUL EFFECTS ON HUMANS
Being the one which commonly affects our health, we usually discuss
the harmful effects of UV-B. The consequences of increased exposure
of the human body to UV-B radiation will in the first instance be
characterized by the physical properties of this type of radiation. UV-B
radiation does not penetrate far into the body as most of it is absorbed
in the superficial tissue layers of 0.1 mm depth. This limits the primary
effects to the skin and the eyes. However, there are also systemic
effects. These start with a primary reaction in the superficial layers,
but have consequences throughout the body. It is the main cause of
sunburn and tanning and it has some influences on the immune system
too. UV-B radiation is also the main cause of snow blindness and an
important factor in the induction of cataracts. UV-B radiation
contributes significantly to the ageing of the skin and eyes and it is
the UV-B range that is most effective in causing skin cancer.
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 GENETIC
Ultraviolet photons harm the DNA molecules of living organisms in
different ways. DNA absorbs UV-B light and the absorbed energy can
break bonds in the DNA. Most of the DNA breakages are repaired by
proteins present in the cell’s nucleus. These may mend the damage or
part of the damage. The repair systems may, however, themselves be
damaged by increased UV-B exposure. But unrepaired genetic damage
of the DNA can lead to skin cancers. In one common damage event,
adjacent thymine bases bond with each other, instead of across the
“ladder”. This makes a bulge, and the distorted DNA molecule does not
function properly.
 EFFECTS ON SKIN
1.
Sunburn:
One of the most common
effects of UV exposure is
“erythema” also known as sunburn. Sunburn occurs when skin cells
are damaged by the absorption of energy from UV rays. To
compensate for this injury, the skin sends extra blood to the damaged
skin in an attempt to repair it. Thus, accounting for the redness that is
associated with sunburn, the amount of time it takes for sunburn to
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occur is dependent mostly on the relative amounts of UV rays that are
hitting the skin and on a person’s skin type. People with naturally dark
skin already have inherently high levels of melanin, and so are able to
spend a longer amount of time in the sun before burning. Fair-skinned
people don’t have it quite so easy as burning can occur within a
relatively short amount of time.
2.
Sun tan:
As a defense against UV radiation, the amount of the brown pigment
melanin in the skin increases when exposed to moderate (depending
on skin type) levels of radiation. This is commonly known as sun tan.
The purpose of melanin is to absorb UV radiation and dissipate the
energy as harmless heat, blocking the UV from damaging skin tissue.
UV-A gives a quick tan that lasts for days by oxidizing melanin that
was already present and triggers the release of the melanin from
melanocytes. UV-B yields a tan that takes roughly 2 days to develop
because it stimulates the body to produce more melanin. The
photochemical properties of melanin make it an excellent
photoprotectant.
Photodermatoses:
Photodermatoses are skin diseases where the skin lesions are caused
by light. Such lesions may be itching papules, whaling of the skin,
fierce reddening and peeling etc. The more sensitive patients cannot
even stand one minute of outdoor daylight. In these diseases the UV-B
radiation in sunlight is the predominant causative agent. Loss of
adaptation of the skin to light appears to be a predominant factor for
these diseases.
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4. Premature Ageing of Skin:
Another effect of ultraviolet rays on the skin is premature ageing of
the skin. Recent studies have shown that many of the symptoms
commonly associated with mere ageing (i.e. wrinkles, loosening of
the skin) may instead be related to UV exposure. Even careful
tanning kills skin cells, damages DNA and causes permanent
changes in skin connective tissues which lead to wrinkle formation
in later life. UV-A, UV-B and UV-C, all these can damage collagen
fibers and thereby accelerate aging of the skin. Both UV-A and UV-B
destroy vitamin A in skin which may cause further damage.
5.Skin Cancer:
90% of the skin carcinomas are attributed to UV-B exposure [Wayne]
and the chemical mechanism by which it causes skin cancer has been
identified [Tevini]. The above named carcinomas are relatively easy to
treat, if detected in time, and are rarely fatal.
There are various types of skin cancer. One main class is formed by
the coetaneous melanomas, the cancers of the pigment cells. This
appears to be a correlation between brief and high intensity exposures
to UV and eventual appearance (as long as 10-20yrs) of melanoma.
The other main types are basal cell carcinomas and squamous cell
carcinomas, cancers of the epithelial cells. These carcinomas of the
skin are sometimes, collectively, called “non-melanoma skin cancers”.
For the present example we will deal with these non-melanoma skin
cancers. In white Caucasians, the incidence of these cancers ranks
high among the various types of cancer. In some populations it is in
fact the highest of all. The incidence is lower in more pigmented
populations, typically by a factor of 10 or even 100. The mortality rate
is low in comparison with that for other types of cancer approximately
1% in areas with good medical care.
The non-melanoma skin cancers are clearly correlated to sunlight.
They occur mostly in light-skinned people and then predominantly on
skin areas which are most exposed to sunlight, such as the face. In
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people of comparable genetic background, the incidences are higher
in the sunnier geographical areas.
Early experiments showed that white rats exposed to sunlight
developed skin cancers, but similar rats exposed to sunlight filtered
through window glass did not. As the window glass absorbed mainly
UV-B radiation, this result indicated that the carcinogenic effect to a
large extent due to the UV-B radiation in sunlight.
In technical terms, carcinogenic effectiveness was defined as the
reciprocal value of the daily dose of radiation at a certain wavelength
required for the induction of tumors of 1 mm diameter in 50% of a
group of mice in 300 days. The tumors in these mice were
predominantly squamous cell carcinomas.
 DNA DAMAGE
UV-B light can cause direct DNA damage. The radiation excites DNA
molecules in skin cells, causing aberrant covalent bonds to form
between adjacent cytosine bases, producing a dimer. When DNA
polymerase comes along to replicate this strand of DNA, it reads the
dimer as “AA” and not the original “CC”. This causes the DNA
replication mechanism to add a “TT” on the growing strand. This is a
mutation, which can result in cancerous growths and is known as a
“classical C-T mutation”. The mutations that are caused by the direct
DNA damage carry a UV signature mutation that is commonly seen in
skin cancers.
 EFFECTS ON EYES
High intensities of UV-B light are hazardous to the eyes and exposure
can cause welder’s flash (photokeratitis or arc eye) and may lead to
cataracts, pterygium, and pinguecula formation. Another possible eye
damage that can result from high doses of UV light is particularly to
the cornea which is a good absorber of UV light. High doses of UV light
can cause a temporary clouding of the cornea called ‘snow-blindness’
and chronic doses has been tentatively linked to the formation of
cataracts. High incidences of cataracts are found at high elevations,
Tibet and Bolivia and higher incidences are seen at lower latitudes
(approaching the equator). UV light is absorbed by molecules known
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as chromophores, which are present in the eye cells and tissues.
Chromophores absorb light energy from the various wavelengths at
different rates – a pattern known as absorption spectrum. If too much
UV light is absorbed, eye structures such as the cornea, the lens and
the retina can be damaged.
 EFFECTS ON IMMUNE SYSTEM
Prolonged exposure can damage the human immune system. Cells or
tissue components which are altered by the radiation may be
recognized as foreign material by the immune system and are
removed. Certain functions of the immune system are however,
suppressed by exposure to UV-B radiation. When skin is exposed to
more UV-B radiation then it is accustomed to its ability to adapt.
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OZONE DEPLETION AND UV RADIATIONS
Ozone depletion results in an increase of UV-B radiation, but the
shorter the wavelength, the stronger the increase within the UV-B
range. 1% decrease in the ozone layer will cause an estimated 2%
increase in UV-B irradiation; it is estimated that this will lead to a 4%
increase in basal carcinomas and 6% increase in squamous-cell
carcinomas [Graedel & Crutzen]. Many scientists today believe that
this life-protecting stratospheric ozone layer is being reduced by the
chlorofluorocarbon (CFCs) gases released into the atmosphere by
different sources on the earth. Many environment groups are
vehemently protesting against the use of these gases and their use in
many places in the world has been banned. Pollution on the earth has
already caused a hole in the ozone layer above the Antarctic.
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VULNERABILITIES DUE TO UV RADIATIONS
A diagram produced by WHO based on ‘global burden of diseases from
solar ultraviolet radiation’ in the year 2006.
CONCLUSION
Thus we can conclude that UV rays have a disastrous impact on our
planet. It will lead to many dangers which would affect not only us but
also the entire living community on this earth. UV rays can lead to
many unforeseen disasters which can signal the end of life on this
beautiful planet.
All the dangers attributed to UV rays reaching our earth reside only on
man. Man by his reckless actions has dug graves not only for himself
but also for the earth too. It’s his only responsibility to restore the
earth back to its healthy mode.
Thus, a concerted effort is needed on the side of mankind to quickly
address this danger. Steps have to be taken from individual to the
international level to protect our earth. From abandoning plastics to
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decrease the dependence on automobiles, man has to be careful to
ensure that he does not push earth to its death. We also need to
ensure that we do not create UV rays by machines and their usage
must be strongly restricted only to the academic field. Also we need to
create awareness among ourselves on the need of the hour to protect
life. It’s a pity that we try to blame domestic animals for increasing the
levels of methane in the atmosphere. What we need to understand is
that their methane levels are nothing as compared to our creation of a
hole on the ozone layer. Their actions are too small to be compared to
our sins.
Being a part of future generation, the student community also needs to
be aware about the topic which is a prime reason for me selecting this
project. We too should take care not to harm our earth in any way.
Always we should remember that “we have not inherited the earth
from our fathers but have leased it from our future generations”. This
alone will make us responsible and be steadfast in our Endeavour to
combat the penetration of UV rays.
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BIBLIOGRAPHY
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R.Parson, FAQ 111, UV and biological effects of UV.
FDA Consumer Magazine and publications: FDA#87-8272, #818149 and #92-1146.
M.Tevini, UV-B Radiation and Ozone Depletion: Effects on
humans, animals, plants, microorganisms and materials Lewis
Pub. Boca Raton, 1993.
R.P.Wayne, Chemistry of the Atmospheres 2nd ed. Oxford 1991.
R.Smith, “Ozone depletion: Ultraviolet radiation and
phytoplankton biology in Antarctic waters”‘Science, 255, 952.
(1992).
Brien Sparling, UV Radiation.
Sun Smart publications, UV Rays.
Jan C. van der Leun and Frank R. de Gruijl, Influences of Ozone
Depletion on Human and Animal Health.
IMAGES DOWN HERE
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Thank You
Master Sayantan Mahapatra
Class-xii,12
Session- 2013-2014