Biology Project on Ozone

7/29/2019 Biology Project on Ozone

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OZONE DEPLETION

Submitted by :- Yash Singh

Class- XII-A


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CERTIFICATE

TO WHOMSOEVER IT MAY CONCERN:-

This is to certify that Yash Singh, student of class XII-A, Delhi Public

School, Kalyanpur, have successfully completed his project on OZONE

DEPLETION, under my guidance. While doing the report they got

exposure of the latest environmental problems that are surfacing, majorly

ozone depletion and the aftermath. He acquired good knowledge of

concepts, sense of responsibility, professional judgment and decision

making ability.

Mrs. Rupali Tyagi

( Mentor)


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CONTENTS

Introduction

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

ULTRAVIOLET RAYS

Bibliography


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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 thisgrowing 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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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 AbbreviationWavelength range in

nanometers

Energy per

photon

Ultraviolet A, long

wave, or black lightUVA 400 nm320 nm 3.103.94 eV

Near NUV 400 nm300 nm 3.104.13 eV

Ultraviolet B or medium

waveUVB 320 nm280 nm 3.944.43 eV

Middle MUV 300 nm200 nm 4.136.20 eV

Ultraviolet C, short

wave, or germicidalUVC 280 nm100 nm 4.4312.4 eV

Far FUV 200 nm122 nm 6.2010.2 eV

Vacuum VUV 200 nm10 nm 6.20124 eV

Extreme EUV 121 nm10 nm 10.2124 eV

SOURCES OF UV RAYS


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The Sun emits ultraviolet radiation in UV-A, UV-B, and UV-C bands.

The Earths ozone layer blocks 98.7% of this UV radiation from

penetrating through the Earths atmosphere. 98.7% of the ultraviolet

radiation that reaches the Earths surface is UVA.

Other sources: There are also several artificial methods to produce UV

rays such as from black light (Woods 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:- Latitude and elevation of the location: - 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: - The reduction in UV-B exposure depends on the

thickness of cloud cover.


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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.

EFFECTS OF UV RADIATION ON NATURE

The effects of UV radiation on earths 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


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increase in UV, it would be on a blue sky day by further scattering the

radiation and increasing the levels that reach the surface.

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.

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. Therate 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


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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 10-12weeks, this translates into a 2-4%

loss overall, a measurable but not yet a catastrophic loss.

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.

An increase in UV-B will cause in production of Ozone at lower

levels in the atmosphere. While some have hailed the protectionoffered by this pollution-shield. Many plants have shown

themselves to be very sensitive to photochemical smog.

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


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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.

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 cells 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 abulge, and the distorted DNA molecule does not function properly.

EFFECTS ON SKIN


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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 occur is dependent mostly on the

relative amounts of UV rays that are hitting the skin and on a personsskin 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 dont have it quite so easy as

burning can occur within a relatively short amount of time.

2. Sun tan: As a defence against UV radiation, the amount of the brownpigment 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

Ultraviolet (UV) radiation present in sunlight is an

environmental human carcinogen. The toxic effects of UV from

natural sunlight and therapeutic artificial lamps are a major

concern for human health. The major acute effects of UV

irradiation on normal human skin comprise sunburn,

inflammation, erythema, tanning and local or systemic

immune-suppression.


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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.

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: 9 0% of the skin carcinomas are attributed to UV-Bexposure [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


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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 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


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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 welders 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 as chromophores, which arepresent 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


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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.

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.

VULNERABILITIES DUE TO UV RADIATIONSA diagram produced by WHO based on global burden of diseases from

solar ultraviolet radiation in the year 2006.

CONCLUSION


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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. Its 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

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. Its 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 beaware 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

http://www.google.com

http://www.wikipedia.org

www.epa.gov/ozone

environment.nationalgeographic.com/.../ozone-depletion-

overview

ozonewatch.gsfc.nasa.gov
http://www.google.com/http://www.wikipedia.org/http://www.epa.gov/ozonehttp://www.google.com/http://www.wikipedia.org/http://www.epa.gov/ozone

Biology Project on Ozone

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