Band 6 Science Form 1

8/11/2019 Band 6 Science Form 1

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What is air pollution?

Air pollution (say: po-loo-shun) occurs when gases, dust particles, fumes (orsmoke) or odour are introduced into the atmosphere in a way that makes it

harmful to humans, animals and plant. This is because the air becomes dirty(contaminated or unclean).

The Earth is surrounded by a blanket of air (made up of various gases) called theatmosphere. The atmosphere helps protect the Earth and allow life to exist. Without it,we would be burned by the intense heat of the sun during the day or frozen by the very

low temperatures at night.

Any additional gas, particles or odours that are introduced into the air (either by natureor human activity) to distort this natural balance and cause harm to living things can becalled air pollution.

Things that pollute the air are calledpollutants.Examples of pollutants includenitrogen oxides, carbon monoxides, hydrocarbons, sulphur oxides (usually fromfactories), sand or dust particles, and organic compounds that can evaporate and enterthe atmosphere.

There are two types of pollutants:Primary pollutantsare those gases or particles that are pumped into the air to makeit unclean. They include carbon monoxide from automobile (cars) exhausts and sulfurdioxide from the combustion of coal.

Secondary pollutants:When pollutants in the air mix up in a chemical reaction, they

form an even more dangerous chemical. Photochemical smog is an example of this, andis a secondary pollutant.


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What are the common air pollutants around?

Carbon Monoxide (CO)Fuel combustion from vehicles and engines.Reduces the amount of oxygen reaching the bodys organs and tissues; aggravates

heart disease, resulting in chest pain and other symptoms.

Ground-level Ozone (O3)

Secondary pollutant formed by chemical reaction of volatile organic compounds(VOCs) and NOx in the presence of sunlight.

Decreases lung function and causes respiratory symptoms, such as coughing and

shortness of breath, and also makes asthma and other lung diseases get worse.More

on Ground Level Ozone Here

Lead (Pb)Smelters (metal refineries) and other metal industries; combustion of leaded

gasoline in piston engine aircraft; waste incinerators (waste burners), and batterymanufacturing.

Damages the developing nervous system, resulting in IQ loss and impacts onlearning, memory, and behavior in children. Cardiovascular and renal effects in adultsand early effects related to anaemia.

Nitrogen Dioxide (NO2)Fuel combustion (electric utilities, big industrial boilers, vehicles) and wood burning.

Worsens lung diseases leading to respiratory symptoms, increased susceptibility torespiratory infection.

Particulate Matter (PM)This is formed through chemical reactions, fuel combustion (e.g., burning coal, wood,

diesel), industrial processes, farming (plowing, field burning), and unpaved roads orduring road constructions.

Short-term exposures can worsen heart or lung diseases and cause respiratory
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problems. Long-term exposures can cause heart or lung disease and sometimespremature deaths.

Sulfur Dioxide (SO2)

SO2 comes from fuel combustion (especially high-sulfur coal); electric utilities andindustrial processes as well as natural occurances like volcanoes.

Aggravates asthma and makes breathing difficult. It also contributes to particleformation with associated health effects.

What causes air pollution?

Air pollution can result from both human and natural actions. Natural events thatpollute the air include forest fires, volcanic eruptions, wind erosion, pollen dispersal,evaporation of organic compounds and natural radioactivity. Pollution from natural

occurrences are not very often.

Human activities that result in air pollution include:

1. Emissions from industries and manufacturing activities

Have you seen a manufacturing company before? You will notice that there are long

tubes (called chimneys) erected high into the air, with lots of smoke and fumes comingout of it. Waste incinerators, manufacturing industries and power plants emit highlevels of carbon monoxide, organic compounds, and chemicals into the air. This

happens almost everywhere that people live. Petroleum refineries also release lots ofhydrocarbons into the air.

2. Burning Fossil FuelsAfter the industrial age, transportation has become a key part of our lives. Cars andheavy duty trucks, trains, shipping vessels and airplanes all burn lots of fossil fuels towork. Emissions from automobile engines contain both primary and secondary

pollutants. This is a major cause of pollution, and one that is very difficult to manage.This is because humans rely heavily on vehicles and engines for transporting people,good and services.

Fumes from car exhauts contain dangerous gases such as carbon monoxide, oxides ofnitrogen, hydrocarbons and particulates. On their own, they cause great harm to people

who breath them. Additionally, they react with environmental gases to create furthertoxic gases.Click here to see the effects
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3. Household and Farming ChemicalsCrop dusting, fumigating homes, household cleaning products or painting supplies, overthe counter insect/pest killers, fertilizer dust emit harmful chemicals into the air andcause pollution. In many case, when we use these chemicals at home or offices with noor little ventilation, we may fall ill if we breathe them.

What are the effects of air pollution?

Acidification:Chemical reactions involving air pollutants can create acidic compounds which cancause harm to vegetation and buildings. Sometimes, when an air pollutant, such assulfuric acid combines with the water droplets that make up clouds, the water droplets

become acidic, forming acid rain. When acid rain falls over an area, it can kill trees andharm animals, fish, and other wildlife.

Acid rain destroys the leaves of plants.When acid rain infiltrates into soils, it changes the chemistry of the soil making it unfitfor many living things that rely on soil as a habitat or for nutrition. Acid rain alsochanges the chemistry of the lakes and streams that the rainwater flows into, harmingfish and other aquatic life.

Eutrophication:Rain can carry and deposit the Nitrogen in some pollutants on rivers and soils. This will

adversely affect the nutrients in the soil and water bodies. This can result in algaegrowth in lakes and water bodies, and make conditions for other living organismharmful.


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Ground-level ozone:Chemical reactions involving air pollutants create a poisonous gas ozone (O3). Gas

Ozone can affect peoples health and can damage vegetation types and some animallife too.

Particulate matter:

Air pollutants can be in the form of particulate matter which can be very harmful to ourhealth. The level of effect usually depends on the length of time of exposure, as wellthe kind and concentration of chemicals and particles exposed to. Short-termeffectsinclude irritation to the eyes, nose and throat, and upper respiratory infectionssuch as bronchitis and pneumonia. Others include headaches, nausea, and allergicreactions. Short-term air pollution can aggravate the medical conditions of individualswith asthma and emphysema. Long-term health effectscan include chronicrespiratory disease,lung cancer,heart disease, and even damage to the brain, nerves,liver, or kidneys. Continual exposure to air pollution affects the lungs of growingchildren and may aggravate or complicate medical conditions in the elderly.

Air pollution prevention, monitoring and solution.

Solution efforts on pollution is always a big problem. This is why preventioninterventions are always a better way of controlling air pollution. These preventionmethods can either come from government (laws) or by individual actions. In many bigcities, monitoring equipment have been installed at many points in the city. Authoritiesread them regularly to check the quality of air. Let's see more below:

Government (or community) level preventionGovernments throughout the world have already taken action against air pollution

by introducing green energy. Some governments are investing inwind energyandsolarenergy,as well as otherrenewable energy,to minimize burning of fossil fuels, which

cause heavy air pollution.

Governments are also forcing companies to be more responsible with theirmanufacturing activities, so that even though they still cause pollution, they are a lot

controlled.

Companies are also building more energy efficient cars, which pollute less than

before.

Individual Level PreventionEncourage your family to use the bus, train or bike when commuting. If we all do

this, there will be less cars on road and less fumes.
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Use energy (light, water, boiler, kettle and fire woods) wisely. This is because lots offossil fuels are burned to generate electricity, and so if we can cut down the use, we willalso cut down the amount of pollution we create.

Recycle and re-use things. This will minimize the dependence of producing newthings. Remember manufacturing industries create a lot of pollution, so if we can re-usethings like shopping plastic bags, clothing, paper and bottles, it can help.

Human activities causes air pollution and raising the following problems:

(a)Acid rain

(b)Greenhouse effect

(c)

Depletion of ozone layer


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What Causes Acid Rains?

Acid rain is caused by a chemical reaction that begins whencompounds like sulfur

dioxide and nitrogen oxides are released into the air. These substances can rise

very high into the atmosphere, where they mix and react with water, oxygen, and

other chemicals to form moreacidic pollutants,known as acid rain. Sulfur dioxide

and nitrogen oxides dissolve very easily in water and can be carried very far by the

wind. As a result, the two compounds can travel long distances where they becomepart of the rain, sleet, snow, and fog that we experience on certain days.

Human activities are the main cause of acid rain. Over the past few decades,

humans have released so many different chemicals into the air that they have

changed the mix of gases in the atmosphere. Power plants release the majority of

sulfur dioxide and much of the nitrogen oxides when they burnfossil fuels,such as

coal, to produce electricity. In addition, theexhaust from cars, trucks, and buses

releases nitrogen oxides and sulfur dioxide into the air. These pollutants cause

acid rain.

Nature depends on balance, and although some rain is naturally acidic, with

apH level of around 5.0, human activities have made it worse. Normal

precipitationsuch as rain, sleet, or snowreacts withalkaline chemicals,or non-

acidic materials, that can be found in air, soils, bedrock, lakes, and streams. These

reactions usuallyneutralize natural acids. However, if precipitation becomes too

acidic, these materials may not be able to neutralize all of the acids. Over time,

these neutralizing materials can be washed away by acid rain. Damage to crops,

trees, lakes, rivers, and animals can result.
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Effect to living thing and environment

(i) Acid Rain Can Cause Health Problems in People

Air pollution like sulfur dioxide and nitrogen oxides can cause respiratory

diseases, or can make these diseases worse. Respiratory diseases

likeasthma or chronicbronchitis make it hard for people to breathe. The

pollution that causes acid rain can also create tiny particles. When these

particles get into peoples lungs, they can cause health problems, or can makeexisting health problems worse. Also, nitrogen oxides cause ground-

levelozone.This ground-level ozone causes respiratory problems,

likepneumonia andbronchitis,and can even cause permanent lung damage.

The health effects that people have to worry about are not caused by the

acid rain, but are caused when people breathe in these tiny particles or

ozone. Swimming in an acidic lake or walking in an acidic puddle is no more

harmful to people than swimming or walking in clean water.

(ii) Acid Rain Harms Forests

Acid rain can be extremely harmful to forests. Acid rain that seeps into the

ground can dissolve nutrients, such as magnesium and calcium,hat trees need

to be healthy. Acid rain also causesaluminum to be released into the soil,

which makes it difficult for trees to take up water. Trees that are located

in mountainous regions at higher elevations, such as spruce or fir trees, are

at greater risk because they are exposed to acidic clouds and fog, which

contain greater amounts of acid than rain or snow. The acidic clouds and fogstrip important nutrients from their leaves and needles. This loss of

nutrients makes it easier for infections, insects, and cold weather to damage

trees and forests.
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(iii) Acid Rain Damages Lakes and Streams

Without pollution or acid rain, most lakes and streams would have a pH level

near 6.5. Acid rain, however, has caused many lakes and streams in the

northeast United States and certain other places to have much lower pH

levels. In addition, aluminum that is released into the soil eventually ends up

in lakes and streams. Unfortunately, this increase in acidity and aluminum

levels can be deadly to aquatic wildlife, includingphytoplankton,mayflies,

rainbow trout, small mouth bass, frogs, spotted salamanders, crayfish, and

other creatures that are part of the food web. This problem can become

much worse during heavy downpours of rain or when the snow begins to melt

in the spring. These types of events are known asepisodic acidification.

(iv) Acid Rain Affects a Food Web

A food web is a diagram that explains the feeding relationships between

different plants and animals in an ecosystem. An animal that is at the top of

a food web eats the various plants and animals that are listed below it.Therefore, the animals at the top are predators, and the animals and plants

listed below them are prey. Some animals have many different sources of

food, while others are more limited in what they eat.
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Acid rain can cause serious problems for many different animals and plants.

As a result, the entire food web is affected. For example, acid rain can

causephytoplankton in lakes to die. Insects, which rely on phytoplankton for

food, now have less food to eat, and they begin to die as a result. These

insects are a source of food for many other animals, such as fish, birds,

frogs, and salamanders. As the insects die, there is now less food for these

animals. This process continues up the entire food web. So, although acid

rain may not directly affect a certain species of plant or animal, it can

affect the entire food web by limiting the amount of food available.

(v) Acid Rain Damages Buildings and Objects

Acid rain can also have a damaging effect on many objects, including

buildings, statues, monuments, and cars. The chemicals found in acid rain can

cause paint to peel and stone statues to begin to appear old and worn down,

which reduces their value and beauty.

Ways to overcome

What Is Being Done?

Now that you knowwhy acid rain is a problem,you might be wondering whats being

done to control it. Regulations and new technologies are helping reduce acid rain.

(i) EPAs Acid Rain Program

Power plants generate the electricity we use every day. Unfortunately,

power plants also produce large amounts of nitrogen oxides and sulfur

dioxidethe pollutants that cause acid rainwhen they burn fossil fuels,

especially coal, to produce energy. Congress passed a law called theCleanAir Act Amendments of 1990,and this law said that EPA should start

theAcid Rain Program.The program limits, or puts acap on, the amount

of sulfur dioxide that power plants can release into the air and

issuesallowances to the power plants to cover their sulfur dioxide
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emissions. It also reduces the amount of nitrogen oxides that power

plants can release.

(ii) Reducing Pollution

Scientists have found different ways to reduce the amount of sulfur

dioxide released from coal-burning power plants. One option is to use coal

that contains less sulfur. Another option is to wash the coal to remove

some of the sulfur. The power plant can also install equipment called

scrubbers, which remove the sulfur dioxide from gases leaving the

smokestack. Because nitrogen oxides are created in the process of

burning coal and other fossil fuels, some power plants are changing the

way they burn coal.

(iii) Other Sources of Energy

A great way to reduce acid rain is to produce energy without using fossil

fuels. Instead, people can use renewable energy sources, such as solar

and wind power. Renewable energy sources help reduce acid rain because

they produce much less pollution. These energy sources can be used to

power machinery and produce electricity.

(iv) Cleaner Cars

Cars and trucks are major sources of the pollutants that cause acid rain.

While one car alone does not produce much pollution, all the cars on the

road added together create lots of pollution. Therefore, car

manufacturers are required to reduce the amount of nitrogen oxides and

other pollutants released by new cars. One type of technology used in

cars is called a catalytic converter. This piece of equipment has been

used for over 20 years to reduce the amount of nitrogen oxides released

by cars. Some new cars can also use cleaner fuels, such as natural gas.

Cars that produce less pollution and are better for the environment are

often labeled as low emissions vehicles. You can find out which vehicles

are low emissions vehicles by looking atEPAs Green Vehicle Guide.

What Can You Do ?
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Government agencies and scientists are not the only ones that can take

action to stop acid rain. You can become part of the solution, too!

(i) Understand the Problem

The first step you can take to help control acid rain is to understand the

problem and its solutions. Now that you have learned about this

environmental issue, you can tell others about it. By telling your

classmates, parents, and teachers about what you learned on this site,

you can help educate them about the problem of acid rain. You CAN make

a difference!

(ii) Conserve Energy

Since energy production creates large amounts of the pollutants that

cause acid rain, one important step you can take is to conserve energy.

You can do this in a number of ways:

Turn off lights, computers, televisions, video games, and other electrical

equipment when you're not using them.

Encourage your parents to buy equipment that uses less electricity, including

lights, air conditioners, heaters, refrigerators, and washing machines. Such

equipment might have theEnergy Star label.

Try to limit the use of air conditioning.

Ask your parents to adjust the thermostat (the device used to control the

temperature in your home) when you go on vacation.

(iii) Minimize the Miles

Driving cars and trucks also produces large amounts of nitrogen oxides,

which cause acid rain. To help cut down on air pollution from cars, you can

carpool or take public transportation, such as buses and trains. Also, ask

your parents to walk or bike with you to a

nearby store or friends house instead of

driving.
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Rain is very important for life. All living things need water to live,

even people.

Rain brings us the water we need. But in many places in the world

even where you live, rain has become a menace.

Because of pollution in the air, acid gases from factories, cars and

homes, the rain is becoming dangerous for the life of every living

creature.

This rain is known as 'acid rain'.


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WHAT IS ACID RAIN?

Acid gases are produced when fossil fuels like coal and oil areburned in power stations, factories and in our own homes.

Most of these acid gases are blown into the sky, and when

they mix with the clouds it can cause rain - or snow, sleet,

fog, mist or hail - to become more acidic.

The opposites of acid are alkalis; for example, toothpaste and

baking powder are both alkalis. Strong alkalis can also be dangerous, such as ammonia

and bleach.

Lemon juice, vinegar and cola are all acidic. Rain is naturally

acidic, but acid gases make it even more acidic, sometimes as

acid as lemon!

Nature can also produce acid gases,

such as volcanoes. When they erupt,

the smoke that comes out of the

crater is also full of acid gases.


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HOW DO WE MEASURE ACIDITY?

There is a special scale called the pH scale thatmeasures the strength of acids and alkalis. A low pH

number means something is acid. A high number means

something is alkali. And something in the middle is

called neutral.

Acidity can be tested using litmus paper.

Usually rain is a little acidic, and has pH of about 5.5, if

the pH of rainfall is less than 5.5, then the rain is probably polluted by

acid gases.

Acids turn litmus paper red, and alkalis turn it blue. With a special paper

called universal indicator, you can test levels of acidity.

WHAT ARE THE MAIN GASES THAT CAUSE ACID RAIN?

When we burn fuels, chemicals called 'sulphur' and 'nitrogen'

are released into the air. Once in the air, they mix with water

in the air - rain, snow, etc - and are transformed into different

chemicals called 'sulphur dioxide' and 'nitrogen oxides', which

can be very dangerous for plants, animals and people. Most of

the 'sulphur' comes from power stations, which make

electricity, and also from volcanoes. Most of the 'nitrogen

oxides' come from car and truck exhausts.

We call 'air pollution' the bad gases that we produce and release in the air.

'Sulphur dioxide' and 'nitrogen oxides' are the most important causes of acid

rain.


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A PROBLEM ALL OVER THE WORLD

Air pollution can be carried over long distances. When acid

gases are released, they go high up in the sky, and then

they are pushed by strong windstowards other countries.

The acid rain in Sweden is caused by air pollution in Britain

and other countries of Europe. The pollution produced in

Britain ends up mostly in Scandinavia - countries in northern

Europe including Sweden, Norway and Denmark.

In the USA, the winds blow the air pollution to certain areas in Canada.

HOW BAD IS ACID RAIN?

When rain is acidic, it affects what it falls on: trees, lakes,

buildings and farmland. Sometimes rain is not very acidic and

does not cause a lot of problems, but when it is acidic, it can

be very harmful to the environment.

TREES AND PLANTS

Acid rain can have terrible effects on a forest. The acid takes

away important minerals from the leaves and the soil.

Minerals are like vitamins for trees and plants. Without them,

trees and plants cannot grow properly. They lose their leaves and

become very weak. They are no longer strong enough to fightagainst illnesses and frost. They become very ill and can even die.

Some soils are alkaline, when acid rain falls on them the acid becomes neutral. Plants

and trees living on these soils are not in any big danger..


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LAKES AND WATER LIFE

Acid rain has a terrible effect on water life. Even if the acid

rain does not fall straight into the lake, for example, it may

enter from rivers and streams. Some of the life in the lakesuch as fish and plants may end up dying, because they

cannot survive in acidic lakes.

Thousands of lakes in Scandinavia have no more life in them.

They have received so much acid rain for so many years, because of the winds pushing

the acid gases, that nothing can survive.

You can recognise a lake dead from acid rain by its clean and crystal clear water. But

they look clean because there is very little living in them anymore. Tiny plants andanimals are mostly unable to survive..


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OUR HEALTH

Particulates - very small particles of debris found in some of the air pollution - are

one of the main causes of health problems. In towns and cities,

these are released mainly by diesel engines from cars and trucks.

When we breathe in air pollution, these very fine particulates can

easily enter our body, where they can cause breathing problems,

and over time even cause cancer.

Water we drink from taps can be contaminated by acid rain, which

can damage the brain..

BUILDINGS

Acid rain can also ruin buildings because the acid eats into metal

and stone. It also damages stained glass and plastics. Some

types of building materials are softer than others, and it is the

softer ones which are most affected by acid rain. Sandstone

and limestone are examples of stone which are fairly soft and

are damaged easily. Granite is an example of a harder stone

that can resist the effects of acid rain.

In many places in the world, ancient and famous buildings and monuments

are affected by acid rain. For example, the Statue of Liberty in New

York, USA, has had to be restored because of acid rain damage.

Buildings are naturally eroded by rain, wind, frost and the sun, but when

acidic gases are present, it speeds up the erosion.


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What Causes Greenhouse Effect?

Heat energy comes to the Earth as sunlight and leaves in the form of infrared

radiation, but greenhouses gases trap some of the radiation before it can

escape the atmosphere again, leading to the "greenhouse effect."This gives

the atmosphere a great deal of its ambient warmth. However, as greenhouse gases

have increased their presence in the environment, the temperature of the Earthhas risen as a result.

The term "greenhouse effect" comes from the idea that the Earth's atmosphere

works in much the same way as a man-made greenhouse. This structure is made

primarily of glass, permitting sunlight to come in but trapping the resulting heat

inside the structure. The "greenhouses gases" come from a number of sources but,

in general, they consist of nitrous oxide, methane, carbon dioxide and the gases

that go into aerosols.Since industrialization began around 1850, levels of greenhouse gases in the

environment have gone up approximately 25 percent. The arrival of fossil fuels and

the need for electricity meant that the consumption of energy would lead to

greater greenhouse gas emissions. The challenge for government planners is to find

a happy medium between development and environmental protection.

Before we dig deep into the causes of greenhouse effect, it is important for us to

know what isgreenhouse effect.You must have heard of greenhouse effect duringany debate on global warming. The light that we get from the sun helps to keep this

atmosphere warm. Of the 100% light that sun sends to earth, almost 70% sunlight

is reflected back into the sky. Only 30% of that sunlight is absorbed by us. The

sunlight absorbed is used for different purposes. It can be used to produce

solar energy, drying clothes, by plants in the process of photosynthesis and to

make this planet warm and comfortable for living.
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The 70% of the light that is reflected back into the space, also known as infrared

radiations, are absorbed by greenhouse gases before they are lost to space. The

absorption of these lights by greenhouse gases make it possible to keep this planet

warm for living beings as these gases acts like a mirror and reflect some of the

heat back to earth. Without Greenhouse effect, the temperature of this planet

would be lesser by 30 degree celsius and this would be too cold for us to survive.

The major greenhouse gases solely responsible for greenhouse effect are: carbon

dioxide, ozone, methane and water vapors. Although these gases comprise 1% of

our atmosphere, they act like a thick warm blanket outside that surrounds this

planet and regulate climate control. Greenhouse effect is not bad, in fact it is

needed to for all of us to survive on earth. In short, the greenhouse effect isnothing but a naturally occurring process designed by nature that aids in heating

earths surface and helps to maintain ecological balance.

Now some of that heat dissipates into space, some of it burns along the

atmosphere, and some of it penetrates the atmosphere and finds its way into the

lower atmosphere and the planet surface. This in turn raises the average

temperature of the Earth. This increases the greenhouse effect and is a partial

contributor to global warming

1. Burning of Fossil Fuels: Fossil fuels like coal, oil and natural gas have become

an integral part of our life. They are used on large basis to produce electricity and

for transportation. Pollution which gets emit from vehicles contains carbon dioixde,

which is one the main gas responsible for increase in greenhouse effect. Apart,
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from that, the production of electricity consume too much of coal which releases

large amount of these gases into the atmosphere.

2. Deforestation: Forests holds a major green area on this earth. Plants and trees

intake carbon dioxide and release oxygen, through the process of photosynthesis,for the survival of human beings. Large scale development have forced people to

look for alternate places for living which has resulted in cutting down of trees. The

wood that is produced, when burnt releases more carbon dioxide into the

atmosphere.

3. Increase in Population: Over the last few decades, there have been huge

increase in the population. Now, this has resulted in increased demand for food,

cloth and shelter. New manufacturing industries have come up release some

harmful gases into the atmosphere which increases the greenhouse effect. Also,

more people means more usage of fossil fuels which in turn has aggravated the

problem.

4. Farming: Nitrous oxide is one the greenhouse gas that is used in fertilizer and

contributes to greenhouse effect which in turn leads to global warming.

5. Industrial waste and landfills: Industries which are involved in cement

production, fertilizers, coal mining activities, oil extraction produce harmful

greenhouse gases. Also, landfills filled with garbage produce carbon dioxide and

methane gas contributing significantly to greenhouse effect.


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The Earth is wrapped in a blanket of air called the 'atmosphere', which is made up

of several layers of gases. The sun is much hotter than the Earth and it gives off

rays of heat (radiation) that travel through the atmosphere and reach the Earth.

The rays of the sun warm the Earth, and heat from the Earth then travels backinto the atmosphere. The gases in the atmosphere stop

some of the heat from escaping into space. These gases are

called greenhouse gases and the natural process between

the sun, the atmosphere and the Earth is called the

'Greenhouse Effect', because it works the same way as a

greenhouse. The windows of a greenhouse play the same role

as the gases in the atmosphere, keeping some of the heat

inside the greenhouse.


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THE NATURAL GREENHOUSE EFFECT

The atmosphere has a number of gases, often in tiny amounts,which trap the heat given out by the Earth.

To make sure that the Earth's temperature remains constant,

the balance of these gases in the atmosphere must not be

upset.


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The GREENHOUSE GASESare very important and are mainly:

water vapour

occurs naturally in the atmosphere.

carbon dioxide

produced naturally when people and animals breathe. Plants and trees absorb

carbon dioxide to live. Volcanoes also produce this gas. Carbon dioxide is not the

same as carbon monoxide .

methane

comes from cattle as they digest their food. The gas also comes from fieldswhere rice is grown in paddy fields.

nitrous oxide

when plants die and rot, nitrous oxide is produced.

ozone

occurs naturally in the atmosphere.

THE ENHANCED GREENHOUSE EFFECT

Some of the activities of man also produce greenhouse gases. These gases keep

increasing in the atmosphere. The balance of the greenhouse gases changes and

this has effects on the whole of the planet.

Burning fossil fuels - coal, oil and natural gas - releases

carbon dioxide into the atmosphere. Cutting down and

burning trees also produces a lot of

carbon dioxide.

A group of greenhouse gases called


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the chlorofluorocarbons, - which are usually called CFCs, because the other word is

much too long! - have been used in aerosols, such as hairspray cans, fridges and in

making foam plastics. They are found in small amounts in the atmosphere. They are

dangerous greenhouse gases because small amounts can trap

large amounts of heat.

Because there are more and more greenhouse gases in the

atmosphere, more heat is trapped which makes the Earth

warmer. This is known as GLOBAL

WARMING.

A lot of scientists agree that man's

activities are making the natural greenhouse effect stronger. If

we carry on polluting the atmosphere with greenhouse gases, it willhave very dangerous effects on the Earth.

THE EFFECTS

With more heat trapped on Earth, the planet will become

warmer, which means the weather all over Earth will change.

For example, summers will get hotter, and winters too. Thismay seem a good idea, but the conditions we are living in are

perfect for life, and a large rise in temperature could be

terrible for us and for any other living thing on Earth.

At the moment, it is difficult for scientists to say how big the

changes will be and where the worse effects will occur.

The Weather

In Britain, winter and summer temperatures will increase

and the weather will be warmer. In winter it may also rain

more but in summer it may become drier.


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In other parts of the world, the effects will be different,

some places will become drier and others will be wetter.

Although most areas will be warmer, some areas will

become cooler. There may be many storms, floods and

drought, but we do not know which areas of the world will

be affected.

All over the world, these weather changes will affect the kind

of crop that can be grown. Plants, animals and even people may

find it difficult to survive in different conditions.

Sea Levels

Higher temperatures will make the water of the seas and

oceans expand. Ice melting in the Antarctic and Greenland

will flow into the sea.

All over the world, sea levels may rise, perhaps by as much

as 20 to 40 cm, by the beginning of the next century.

Higher sea levels will threaten the low-lying coastal areasof the world, such as the Netherlands and Bangladesh.

Throughout the world, millions of people and areas of land

will be at danger from flooding. Many people will have to

leave their homes and large areas of farmland will be ruined because of floods. In

Britain, East Anglia and the Thames estuary will be at risk from the rising sea.

Farming

The changes in the weather will affect the types of crops

grown in different parts of the world. Some crops, such as

wheat and rice grow better in higher temperatures, but

other plants, such as maize and sugarcane do not. Changes in

the amount of rainfall will also affect how many plants grow.


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People

The changes in climate will affect everyone, but some

populations will be at greater risk. For example, countries

whose coastal regions have a largepopulation, such as Egypt and China, may

see whole populations move inland to avoid

flood risk areas. The effect on people will

depend on how well we can adapt to the

changes and how much we can do to reduce climate change in

the world.


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The Greenhouse Effect and Greenhouse Gasses

Have you ever been inside a greenhouse on a cold winter day? It might be cold

outside, but inside the greenhouse lush green plants flourish in the warmth and

sunshine. Greenhouses are made of glass and are designed to hold heat inside. Ourplanet's atmosphere traps energy just like a greenhouse. Energy from the Sun can

enter the Earths atmosphere, but not all of it can easily find its way out again.

What blocks the Suns energy from escaping from the Earth? Unlike a greenhouse,

the Earth does not have a layer of glass over it! Instead, molecules in our

atmosphere called greenhouse gasses absorb the heat. Greenhouse gasses include

water vapor, methane, ozone, nitrous oxide, and carbon dioxide. There may not be

much of some of these gasses in our atmosphere, but they can have a big impact.

Each greenhouse gas molecule is made of three or more atoms that are bonded

loosely together. These molecules are able to absorb heat, which makes themvibrate. They eventually release the heat energy and it is often absorbed by

another greenhouse gas molecule.

The greenhouse effect is useful because trapping some energy keeps the

temperatures on our planet mild and suitable for living things. Without its

atmosphere and the greenhouse effect, the average temperature at the surface of

the Earth would be zero degrees Fahrenheit. However, too many greenhouse gases

can cause the temperature to increase out of control. Such is the case on Venus

where greenhouse gases are abundant and the average temperature at the surfaceis more than 855 degrees Fahrenheit (457 degrees Celsius).

You might hear people talking about the greenhouse effect as if it is a bad thing.

It is not a bad thing, but people are concerned because Earths greenhouse is

warming up very rapidly. This is happening because we are currently adding more

greenhouse gases to our atmosphere, causing an increased greenhouse effect. The

increased Greenhouse Effect is causing changes in our planet that can affect our

lives.


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The Earth is wrapped in a blanket of air called the

'atmosphere', which is made up of several layers. About 19-

30 kilometres above the Earth is a layer of gas called ozone,

which is a form of oxygen. Ozone is produced naturally in

the atmosphere.

WHY DO WE HAVE AN OZONE LAYER?

The ozone layer is very important because it stops too many of the

sun's 'ultra-violet rays' (UV rays) getting through to the Earth -

these are the rays that cause our skin to tan. Too much UV can

cause skin cancer and will also harm all plants and animals. Life on

Earth could not exist without the protective shield of the ozone

layer.

WHAT IS THE OZONE HOLE?

Every spring, a hole as big as the USA develops in the ozone

layer over Antarctica, in the South Pole. A smaller hole

develops each year over the Arctic, at the North Pole. And

there are signs that the ozone layer is

getting thinner all over the planet.

Scientists have discovered that the ozonehole over Antarctica started in 1979, and that the ozone layer

generally started to get thin in the early 1980s.

The loss of the ozone layer occurs when more ozone is being

destroyed than nature is creating.


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WHAT CAUSES THE OZONE HOLE?

One group of gases is particularly likely to damage the

ozone layer. These gases are called CFCs, Chloro-Fluoro-

Carbons.

CFCs are used in some spray cans to force the

contents out of the can.

They are also used in refrigerators, air conditioning

systems and some fire extinguishers. They are used

because they are not poisonous and do not catch fire.

Most countries have now stopped using new CFCsthat can be released into the atmosphere, but many

scientists believe we must stop using old ones as well.

THE OZONE HOLE AND OUR HEALTH

The ozone layer is like a sunscreen, and a thinning of it would

mean that more ultra-violet rays would be reaching

us.

Too many UV rays would cause more sunburn, and

because sunburn causes skin cancer, this too would

increase deaths.

These UV rays are also dangerous for our eyes and could cause an

increase in people becoming blind. That is why sun cream and sunglasses are very

important.


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THE OZONE HOLE ON ANIMALS AND PLANTS

UV rays can go through water and end up killing small water

animals or plants, called 'plankton' which form the base ofthe food chain in oceans and seas. Whales and other fishes

have plankton as their main food, and if

plankton die because of these UV rays,

whales will start dying too, because they

will not have anything to eat. Large amounts of UV rays could

damage all green plants. If the ozone layer keeps getting

thinner, there could be fewer and fewer plants on Earth, then

there would be less food in the whole world.

THE TWO-FACED OZONE GAS

Ozone found between 19 and 30 kilometres high in the

atmosphere is one of the reasons why we are alive on Earth.

But when the gas ozone is found lower down where we can

breathe it in, it becomes very dangerous for our health.

This ozone is caused by a reaction between air pollutionand sunlight and can cause modern-day smog. This is

different to the smog that formed in the early 20th

century from smoke and fog.


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What can you do:

There are many things we can do to help reduce air pollution and

global warming.

Use buses and trains instead of cars, as they can carry

a lot more people in one journey. This cuts down theamount of pollution produced.

Walking or cycling whenever you can will be even

better, as it does not create any pollution. It will

also be good for your body, as regular exercise will keep you

fit and healthy.

If your parents must use the car, ask them to

avoid using it for very short journeys ifpossible, as this creates unnecessary

pollution. Try to encourage them to share

their journeys with other people, for

example when they go to work or go

shopping. Also encourage them to drive more slowly as this produces less pollution

and less carbon dioxide.


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Energy is produced to generate electricity and

to keep us warm. Most energy is produced by

the burning of fossil fuels, like coal, oil and gas,

which release carbon dioxide, a greenhouse gas.

Fuel burnt in our cars also releases carbondioxide. As an individual, you do not have a lot

of control on how your energy is produced.

However, you can control the way in which you use that energy.

Using less energy means less of it needs to be produced. So less carbon dioxide is

released into the atmosphere.

We can also help prevent pollution from our own homes

which may contribute to acid rain and poor air quality, and

increases emissions of carbon dioxide in the atmosphere.

Turning off lights when they are not needed and not

wasting electricity will reduce the demand for energy. Less

electricity will need to be produced and so less coal, oil and

gas will have to be burnt in power stations, which means

less air pollution and less carbon dioxide!

Pollution formed indoors can be reduced by ensuring

that all gas appliances are working correctly. Goodventilation will improve indoor air quality by dispersing

biological pollutants like dust mite, and other pollutants

such as cigarette smoke.

Most of the rubbish we throw away can be recycled, such as

glass bottles and jars, steel and aluminium cans, plastic

bottles and waste paper.

Recycling used materials uses less

energy than making new ones.

Composting fruit and vegetable waste reduces the amount of

rubbish buried at rubbish dumps.


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What are the Governments doing?

Governments throughout the world have already taken action

for these different environmental problems (i.e. Acid Rain, Air

Quality, Ozone Hole, Global Warming). In their plans they hopeto reduce the amount of emissions of greenhouse gases

produced by man.

About half of the greenhouse effect is caused by

our use of energy, especially from fossil

fuels. Other sources of energy could be used which

do not emit carbon dioxide, e.g. wind

power, solar(sun power) and wave power. In the

home and at school, we must learn to use energyefficiently and not waste it.


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Ozone Depletion: An Introduction

Planet Earth has its own natural sunscreen that shields us from the sun's damaging

ultraviolet radiation. It's called the ozone layer: a fragile band of gases beginning

15 kilometres above our planet, and reaching up to the 40-kilometre level. Humanactivities have caused a substantial thinning of this protective covering not only

over the North and South Poles, but right over our heads.

Stopping ozone layer depletion is one of the major challenges facing the world

today. The stakes are incredibly high. For the ozone layer is truly a "conserver of

life," essential to the survival of all living things.

The Stratospheric Ozone Layer

The ozone layer lies in the stratosphere, in the upper level of our atmosphere. Theozone in it is spread very sparsely. In fact, if you could squish the ozone layer to

the same air pressure we have at sea level, it would be only about as thick as the

sole of your shoe.

Stratospheric ozone filters out most of the sun's potentially harmful shortwave

ultraviolet (UV) radiation. This ozone has become depleted, due to the release of

such ozone-depleting substances as chlorofluorocarbons (CFCs). When

stratospheric ozone is depleted, more UV rays reach the earth. Exposure to higheramounts of UV radiation could have serious impacts on human beings, animals and

plants (seeThe Impacts of Ozone Depletion).

The stratospheric ozone layer sometimes gets confused with the ozone lying near

the earth's surface, known as "ground-level ozone." Although some ground-level

ozone occurs naturally, most is produced by the reaction of sunlight with chemicalsfound mainly in automobile exhaust and gasoline vapours. This human-caused ozone

is a key, unhealthy ingredient of smog. Ironically, we have too much ozone at

ground level and not enough in the stratosphere.

Depletion of the Stratospheric Ozone Layer (Ozone Depletion)

In 1985, a group of scientists made an unsettling discovery: a marked decrease in

stratospheric ozone over the South Pole, in the Antarctic. The depletion appeared

during the southern hemisphere's spring (October and November) and then filled
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in. Soon after the Antarctic hole was found, Canadian scientists discovered that

the ozone layer above the Arctic is also thinning significantly.

The highest latitudes the north and south poles experience the greatest

amount of ozone loss, during their spring. Ozone depletion is most pronounced inthe Antarctic. But ozone depletion, to a lesser degree, now occurs in the mid-

latitudes. For example, the amount of stratospheric ozone over the northernhemisphere has been dropping by 4% per decade.

What does this mean for life on earth? Even the smallest reduction in

stratospheric ozone can have a noticeable impact by increasing the amount of UV

radiation that reaches the planet. Studies show, for example, that a decrease in

stratospheric ozone could cause additional deaths from skin cancer. Even a 1%

global reduction in ozone is expected to cause a significant drop in crop yields, in aworld that is already struggling to feed itself.

The Causes of Ozone Depletion

Scientific evidence indicates that stratospheric ozone is being destroyed by a

group of manufactured chemicals, containing chlorine and/or bromine. These

chemicals are called "ozone-depleting substances" (ODS).

ODS are very stable, nontoxic and environmentally safe in the lower atmosphere,

which is why they became so popular in the first place. However, their very

stability allows them to float up, intact, to the stratosphere. Once there, they are

broken apart by the intense ultraviolet light, releasing chlorine and bromine.Chlorine and bromine demolish ozone at an alarming rate, by stripping an atom from

the ozone molecule. A single molecule of chlorine can break apart thousands of

molecules of ozone.

What's more, ODS have a long lifetime in our atmosphere up to several

centuries. This means most of the ODS we've released over the last 80 years are

still making their way to the stratosphere, where they will add to the ozone

destruction.

The main ODS are chlorofluorocarbons (CFCs), hydrochlorofluorcarbons (HCFCs),

carbon tetrachloride and methyl chloroform. Halons (brominated fluorocarbons)

also play a large role. Their application is quite limited: they're used in specialized


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fire extinguishers. But the problem with halons is they can destroy up to 10 times

as much ozone as CFCs can. For this reason, halons are the most serious ozone-

depleting group of chemicals emitted in British Columbia.

Hydrofluorocarbons (HFCs) are being developed to replace CFCs and HCFCs, foruses such as vehicle air conditioning. HFCs do not deplete ozone, but they are

strong greenhouse gases. CFCs are even more powerful contributors to global

climate change, though, so HFCs are still the better option until even safersubstitutes are discovered.

The Main Ozone-Depleting Substances (ODS)

Chlorofluorocarbons (CFCs)

The most widely used ODS, accounting for over 80% of totalstratospheric ozone depletion.

Used as coolants in refrigerators, freezers and air conditioners in buildings

and cars manufactured before 1995.

Found in industrial solvents, dry-cleaning agents and hospital sterilants.

Also used in foam products such as soft-foam padding (e.g. cushions and

mattresses) and rigid foam (e.g. home insulation).

Halons

Used in some fire extinguishers, in cases where materials and equipment

would be destroyed by water or other fire extinguisher chemicals. In B.C.,halons cause greater damage to the ozone layer than do CFCs from

automobile air conditioners.

Methyl Chloroform

Used mainly in industry for vapour degreasing, some aerosols, cold

cleaning, adhesives and chemical processing.

Carbon Tetrachloride

Used in solvents and some fire extinguishers.

Hydrofluorocarbons (HCFCs)

HCFCs have become major, transitional substitutes for CFCs. They are

much less harmful to stratospheric ozone than CFCs are. But HCFCs they

still cause some ozone destruction and are potent greenhouse gases.


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he Impacts of Ozone Depletion

Stratospheric ozone filters out most of the sun's potentially harmful shortwave

ultraviolet (UV) radiation. If this ozone becomes depleted, then more UV rays will

reach the earth. Exposure to higher amounts of UV radiation could have seriousimpacts on human beings, animals and plants, such as the following:

Harm to human health:

More skin cancers, sunburns and premature aging of the skin.

More cataracts, blindness and other eye diseases: UV radiation can

damage several parts of the eye, including the lens, cornea, retina and

conjunctiva.

Cataracts (a clouding of the lens) are the major cause of blindness in the

world. A sustained 10% thinning of the ozone layer is expected to resultin almost two million new cases of cataracts per year, globally

(Environment Canada, 1993).

Weakening of the human immune system (immunosuppression). Early

findings suggest that too much UV radiation can suppress the human

immune system, which may play a role in the development of skin cancer.

Adverse impacts on agriculture, forestry and natural ecosystems:

Several of the world's major crop species are particularly vulnerable to

increased UV, resulting in reduced growth, photosynthesis and flowering.These species include wheat, rice, barley, oats, corn, soybeans, peas,

tomatoes, cucumbers, cauliflower, broccoli and carrots.

The effect of ozone depletion on the Canadian agricultural sector could

be significant.

Only a few commercially important trees have been tested for UV (UV-B)

sensitivity, but early results suggest that plant growth, especially in

seedlings, is harmed by more intense UV radiation.

Damage to marine life:

In particular, plankton (tiny organisms in the surface layer of oceans) are

threatened by increased UV radiation. Plankton are the first vital step in

aquatic food chains.

Decreases in plankton could disrupt the fresh and saltwater food chains,

and lead to a species shift in Canadian waters.


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Loss of biodiversity in our oceans, rivers and lakes could reduce fish yields

for commercial and sport fisheries.

Animals:

In domestic animals, UV overexposure may cause eye and skin cancers.Species of marine animals in their developmental stage (e.g. young fish,

shrimp larvae and crab larvae) have been threatened in recent years by

the increased UV radiation under the Antarctic ozone hole.

Materials:

Wood, plastic, rubber, fabrics and many construction materials are

degraded by UV radiation.

The economic impact of replacing and/or protecting materials could be

significant.

What Governments are Doing about Ozone Depletion

194 nations, including Canada, have signed an international agreement to end the

production ofchlorofluorocarbons(CFCs),halonsand otherozone-depleting

substances(ODS). The agreement is called theMontreal Protocol on Substances

that Deplete the Ozone Layer(1987). The protocol has been amended several

times, to speed up ODS phaseout dates and to include more types of ODS.

The federal and provincial/territorial governments share responsibility for

protecting the ozone layer. Under the Montreal Protocol, the federal government

is responsible for controlling the import, manufacture, use, sale and export of

ODS. To meet these requirements, Canada has established:

regulations;

an ODS-phaseout program:Canadas Strategy to Accelerate the Phase-Out of

CFC and Halon Uses and to Dispose of the Surplus Stocks(PDF: 211 KB/27

pages); and theNational Action Plan for the Environmental Control of Ozone-Depleting

Substances and their Halocarbon Alternatives(PDF: 117KB/42 pages).

For more information, see Environment Canada'sStratospheric Ozonewebsite.
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The provincial/territorial governments manage the use and handling of ODS. The

B.C. Government passed the Ozone Depleting Substances Regulation in 1993 to

control ODS stored in products and equipment, and encourage consumers and

industry to use more environmentally safe alternatives.

In Schedule A of the regulation, Class I lists all CFCs and halons, as well asmethyl

chloroformandcarbon tetrachloride.Class I substances are considered to have

the most significant impact on ozone layer depletion. Class II of Schedule A listsallhydrochlorofluorocarbons(HCFCs), which are considered the transitional

substances or alternatives to Class I substances. Both Class I and Class II are

ozone-depleting substances.

The regulation was amended in November 1999, mainly to include other halocarbons

as Class III substances e.g.,hydrofluorocarbons(HFCs)andperfluorocarbons(PFCs). The Class III substances do not contain chlorine or

bromine atoms, so they don't deplete the ozone layer. However, they areconsidered potent greenhouse gases and have a significantglobal warming

potential(GWP).

The amendments in 1999 also strengthened certain requirements, and the

regulation was renamed theOzone Depleting Substances and Other Halocarbons

Regulation.The regulation was amended again in 2004, largely to implement

Canadas National Action Plan, which includes phaseout dates for Class I substances(Section 27 of the regulation).

These amendments also included additional CFC-refill restrictions for the mobile

and commercial refrigeration sectors, refill restrictions for halon fire

extinguishers and revised seller take-back provisions for surplus CFC refrigerators.

For more information and to download a copy of the regulation, seeAmendments to

the Ozone Depleting Substances and Other Halocarbons Regulation.

To make sure ODS are recovered correctly, technicians working with thesechemicals must be an approved person as defined in the regulation. This includes

having successfully completed an ODS environmental-awareness course approved

by Environment Canada and the ministry. Technicians must also follow the

procedures detailed in Environment CanadasEnvironmental Code of Practice for

Elimination of Fluorocarbon Emissions from Refrigeration and Air Conditioning

Systems(PDF: 61 pages) and theEnvironmental Code of Practice for Halons.
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B.C. no longer allows the recharging of a motor vehicle air conditioner (MVAC) with

any Class I substance, e.g., CFC-12, the common refrigerant in older air

conditioners. When vehicles are scrapped or their air conditioners are repaired,

the ODS must be recovered safely, with no leaks. A Class II, III or other

alternative substance must be used as the replacement refrigerant. Anyoneservicing an MVAC system must have successfully completed an MVAC servicing-

and-retrofitting course approved by the Ministry of Environment.

What You Can Do about Ozone Depletion

Help Prevent Further Ozone Depletion

The nations of the world have taken a crucial step in joining together to halt theproduction and use of ozone-destroying chemicals. But the work can't stop there.

Here's what you can do:

Know the rules: It is illegal to recharge refrigerators, freezers and

home/vehicle air conditioners with CFCs.

If you have an older vehicle with an air conditioner*, have it serviced by a

qualified technician, and make sure the CFC is recaptured and recycled by

technician who is specifically certified to do this work. If you don't use your

air conditioner or if the vehicle is about to be scrapped make sure aqualified technician recaptures and recycles the CFC.*Vehicles of model year 1995 or newer do not use CFCs.

The same rules apply to older refrigerators freezers and home air

conditioners, which may contain CFCs.

Don't buy or use portable fire extinguishers that contain halons.

Protect Yourself from Ultraviolet (UV) Radiation

Someultraviolet (UV) radiationfrom the sun has always reached the earth, but

most of it has been screened out by the ozone layer. There has always been areason for people to avoid too much of the sun's damaging rays. But this is true

now more than ever, due to ozone depletion. Be sun safe. Follow these tips:

There's no such thing as a "healthy" tan. Tanning isn't good for you, especially

when the ozone layer is depleted. Fair-skinned people are particularly
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vulnerable to UV radiation, as are infants and children but everyone should

be careful.

Be aware that UV radiation is most intense during the summer, so take extra

precautions. Don't overlook all the "innocent" minutes throughout the year

when you're outside briefly. They can add up to a lot of radiation. Sit in the shade, and avoid prolonged exposure when the sun is high: between

10 a.m. and 4 p.m.

Wear protective clothing and a broad-brimmed sunhat. Sunglasses with 100%

UV protection are also important.

Use a good sunscreen and apply it liberally. It should have a sun-protection

factor (SPF) of 30 or higher, and screen bothUV-A and UV-B rays.

Reapply sunscreen after you've been swimming or perspiring a lot.

Check Environment Canada'sUV Index:It helps Canadians protect themselves

from overexposure to UV radiation, by providing twice-daily forecasts of theamount of radiation expected for different areas of the country.

Taking a holiday in your favourite tropical isle? Have fun, but be very cautious

about those UV rays. Though ozone depletion is not as pronounced near the

equator, the ultraviolet radiation is extremely intense, mainly due to the angle

of the sun.

Keep in mind that you can still get a lot of sun in the winter. Be especially

careful when you're doing outdoor sports, such as skiing. Reflection off freshsnow nearly doubles UV radiation.
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Greenhouse Gases

Greenhouse gases trap heat in the atmosphere, which makes the Earth warmer.

People are adding several types of greenhouse gases to the atmosphere, and each

gas's effect on climate change depends on three main factors:

How much?

How long?

How powerful?

People produce larger amounts of some greenhouse gases than others. Carbon

dioxide is the greenhouse gas you hear people talk about the most. That's because

we produce more carbon dioxide than any other greenhouse gas, and it's

responsible for most of the warming.

Carbon dioxide is the most important greenhouse gas emitted by humans, but

several other gases contribute to climate change, too.Learn more about the major

greenhouse gases by selecting pieces of the pie chart below.
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Water Vapor: It's a Gas!

Water can take the form of an invisible gas called water vapor. Water vapor is

naturally present in the atmosphere and has a strong effect on

weather

and climate.

As the planet gets warmer, more water evaporates from the Earth's surface and

becomes vapor in the atmosphere. Water vapor is a greenhouse gas, so more water

vapor in the atmosphere leads to even more warming. This is an example of

apositive feedback loop, which happens when warming causes changes that lead toeven more warming.

The size of each piece of the pie represents the amount of warming that each gas

is currently causing in the atmosphere as a result of emissions from people's


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activities. Source:Intergovernmental Panel on Climate Change, Fourth Assessment

Report (2007).

Source:EPA's Inventory of U.S. Greenhouse Gas Emissions and Sinks (2014).

Greenhouse gases come from all sorts of everyday activities, such as using

electricity, heating our homes, and driving around town. The graph to the right

shows which activities produce the most greenhouse gases in the United States.

These greenhouse gases don't just stay in one place after they're added to the

atmosphere. As air moves around the world, greenhouse gases become globally

mixed, which means the concentration of a greenhouse gas like carbon dioxide is

roughly the same no matter where you measure it. Even though some countries

produce more greenhouse gases than others, emissions from everycountry

contribute to the problem. That's one reason why climate change requires global
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action. The graph below shows how the world's total greenhouse gas emissions are

continuing to increase every year.

Source:EPA's Climate Change Indicators (2012).
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Band 6 Science Form 1