Ozone depletion, Acid Rain, Greenhouse effect and UV Radiation

Environmental Issues-Ozone depletion, Acid Rain, Greenhouse effect and UV Radiation (Definition, Cause/Source, Effects, Preventive Measures)

1. Kalsang Chodon , 2156 Surati , 47 B. SC zoology ( Hons ) GE- Botany Delh i University BOTANY ASSISSGMENT Environmental Issues

2. Humans impact the environment in several ways. Common effects include decreased water quality, increased pollution and greenhouse gas emissions, depletion of natural resources and contribution to global climate change. Some of these are the direct result of human activities, whereas others are secondary effects that are part of a series of actions and reactions. Environmental issues

3. Ozone depletion

4. What is the Ozone Layer ? T he Ozone layer is a deep blanket in the stratosphere made up of comparatively high concentration of the ozone. As a result of its chemical composition, ozone is regarded as a special type of oxygen as it contains three oxygen molecules (O 3 ) as opposed to the usual two oxygen molecules (O 2 ). The ozone layer encircles the earth and occurs naturally. It is mainly found in the lower part of the stratosphere, approximately 15 to 30 kilometers (9 to 18 miles) above the earth. The ozone is an extremely reactive layer and it acts as a shield from the harmful ultraviolet B rays discharged from the sun. The ozone layer is continually being generated and broken down owing to several atmospheric processes and chemical reactions. This makes the thickness of the ozone layer to vary geographically and seasonally.

5. Ozone Destruction Mechanism Substances such as CFCs, and others that are cited, that lower the ozone layer do not directly destroy ozone. First they undergo photolysis, forming hydrogen chloride (HCl) or chlorine nitrate (ClONO2), molecules that do not react with ozone directly, but slowly decompose, giving, among other things, a small number of chlorine atoms (Cl) and Of chlorine monoxide (ClO) molecules that catalyze the destruction of ozone. The reactions involved in the processes of destruction are more than 100, but can be simplified in the following: Cl + O 3 —–> ClO + O 2 ClO + O —–> Cl + O 2 Net effect: O 3 + O —–> 2 O 2 The chlorine atom acts as a catalyst, i.e. it is not consumed in the reaction, so it destroys thousands of ozone molecules before disappearing. The bromine atom is even more destructive than chlorine (about 10 or 100 times more). On the other hand, along with this, the chlorine concentrations are very low in the stratosphere and the bromine concentrations are even lower.

6. Advantages of the Ozone Layer Protection against cancer and cataracts Ozone is very efficient at absorbing the sun’s ultraviolet (UV) radiation even in very small amounts. For this reason, the ozone layer protects the earth by blocking the harmful ultraviolet (UV) radiation that can cause skin cancer and cataracts in humans . Protection of the environment and ecosystems The ultraviolet (UV) radiation from the sun is very harmful and can be destructive to our natural ecosystems and the environment. UV radiation has an effect upon the fertility of some animals and affects the survival of their offspring. Plants are as well affected by UV radiation as it negatively impacts their ability to develop and grow properly. Furthermore, UV radiation determines chemical reaction and breakdown of various atmospheric processes which can contribute to disastrous changes in the aquatic environments and other earth’s ecosystems in general. For instance, changes in UV levels affect the growth and development of phytoplankton. The ozone layer thus plays an important role by preventing the harmful UV radiations from penetrating into the earth’s lower atmosphere (the troposphere).

7. Causes of Ozone Layer Depletion There have been several concerns about ozone depletion. The problems and causes associated with ozone depletion arise from human activities. Unlike pollution which has several causes, there is one specific chemical compound that is responsible for the breakdown of the ozone layer . These chemical compounds are present in many industrial manufactured products and aerosols. Nonetheless, since the discovery of ozone depletion, the Montreal Protocol was established to regulate the manufacture and use of these chemical compounds. Below is the detailed account of the chemicals responsible for the ozone layer depletion : Chlorofluorocarbons (CFCs) The ODS Other chemicals

8. Chlorofluorocarbons (CFCs) Chlorofluorocarbons (CFCs) are the primary cause for the ozone layer depletion. Industrial products including solvents, soaps, spray aerosols, insulating foams, ‘take-away’ containers and cooling utilities such as refrigerators and air conditioners use chlorofluorocarbons (CFCs). Over time, these substances accumulate in the atmosphere are carried by wind action into the stratosphere. Once the chlorofluorocarbons (CFCs) are in the stratosphere, their molecules are broken up by the ultraviolet radiation from the sun which releases Chlorine atoms. The Chlorine atoms react with the Ozone, setting out a chemical cycle that destroys the good ozone. The U.S. Environmental Protection Agency (EPA) estimates that once Chlorine atom can break up more than 100,000 ozone molecules . The ODS There are also other chemical substances that are generally grouped as Ozone Depleting Substances (ODS). Examples are methyl bromide use in pesticides, methyl chloroform used on making industrial solvents, and halons used in fire extinguishers. Just like the chlorofluorocarbons (CFCs), these substances also chemically react with the ozone which starts a chemical cycle that break up the good ozone .

9. Other chemicals Other chemicals that naturally present similar reactions with the good ozone include Clx, Hox and Noy which belong to the Chlorine, Hydrogen and Nitrogen families respectively.

10. Effects of Ozone Layer Depletion Ozone layer depletion can have some serious consequences on effects of human health, plants, marine ecosystems, biogeochemical cycles and earth’s environment. Let us see each one of these in detail . Effect on biogeochemical cycles Increases in UV radiation alters both sources and sinks of greenhouse gasses in the biosphere e.g.: e.g., carbon dioxide, carbon monoxide, carbonyl sulfide, ozone, and possibly other gases. Changes in UV levels would contribute to biosphere-atmosphere feedbacks that mitigate or amplify the atmospheric concentrations of these gases . Effect on plants Plants become another casualty by radiation effects of UV rays. The physiological and developmental processes of plants are also severely affected apart from the growth. Some other changes that are caused by UV inlcude the way plants form, timing of development and growth, how nutrients are distributied within the plant and metabolism, etc .

11. Effect on health of humans With depletion in ozone’s layer, we humans are more prone to UV rays that reaches the Earth’s surface. Studies suggests that high levels of UV Rays cause non-melanoma skin cancer and plays a major role in malignant melanoma development. Direct exposure to UV rays can lead to development of cataracts which clouds the eye’s lens. Permanent exposure to UV rays can also lead to weakening of the response of immune system and even permanent damage to immune system in some cases. Aging of skin is yet another problem that will make you look older than what you really are. Extensive exposure to UV rays can lead to acceleration of the aging process of your skin. Effect on marine ecosystems UV rays also have adverse effect on the marine ecosystems. It badly affects the planktons that form the foundation of aquatic food webs. Phytoplankton grow close to the surface of the water and plays vital role in the food chain and oceanic carbon cycle. Changes in UV levels is know to affect both orientation and motility in phytoplankton. This reduces the survival and growth rate of these organisms. UV rays are also known to affect the development stages of fish, shrimp, crab, amphibians, and other marine animals. When this happens it affects whole marine food chain as animals  in the upper food chain that feed on these fishes are also affected.

12. Replace halon-based fire extinguishers with others using foam . Check on the label of the products, which we buy at the supermarket, to report that they do not damage the ozone layer . Use your car only when necessary. The less we use our cars, the less pollutants we will emit into the atmosphere. Remember that burning fossil fuels breeds many substances that damage the ozone layer . Do not buy refrigerators or air conditioner equipment that use CFCs as refrigerant. Look for this information in the labels, or ask the supplier of the product directly . Do not use cleaning solvents containing CFCs or ammonia . Do not use sprays, and do not buy objects made of plastic foam (dry ice or freezer). If you receive these products as a fill of your mail packages, return them immediately to the sender. Low consumption of these products will discourage plastic foam manufacturers . Make yourself heard. Please show this page to your children, relatives, friends and neighbors. Ways to prevent Ozone Depletion

13. Precipitation that has a p H of less than that of natural rainwater{which is 5.6 due to dissolved carbon dioxide} It is formed when SO2 and NO as gases or fine particles in the atmosphere combine with water vapor and precipitate as sulphuric acid and nitric acid in rain snow and fog. What is acidity? Acidic and basic are two ways that we describe chemical compounds . Acidity is measured using a pH scale. A pH scale runs from zero (the most acidic) to 14 (the most basic or alkaline). A substance that is neither basic or acidic is called "neutral", and this has a pH of 7. What is acid rain?

14. Formation of acid rain

15. Causes of acid rain!!

16. Natural Cause: Acid rain is caused by a chemical reaction that begins when compounds 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 more acidic 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 become part of the rain, sleet, snow, and fog that we experience on certain days . Anthropogenic Cause: 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 burn fossil fuels, such as coal, to produce electricity. In addition, the exhaust from cars, trucks, and buses releases nitrogen oxides and sulfur dioxide into the air. These pollutants cause acid rain.

17. Effects of Acid Ra i n

18. Effect on Soil:   Acid rain highly impacts on soil chemistry and biology. It means, soil microbes and biological activity as well as soil chemical compositions such as soil pH are damaged or reversed due to the effects of acid rain. The soil needs to maintain an optimum pH level for the continuity of biological activity. When acid rains seep into the soil, it means higher soil pH, which damages or reverses soil biological and chemical activities. Hence, sensitive soil microorganisms that cannot adapt to changes in pH are killed. High soil acidity also denatures enzymes for the soil microbes. On the same breadth, hydrogen ions of acid rain leach away vital minerals and nutrients such as calcium and magnesium.

19. Effect on Aquatic Environment:   Acid rain either falls directly on aquatic bodies or gets run off the forests, roads and fields to flow into streams, rivers and lakes. Over a period of time, acids get accumulated in the water and lower the overall pH of the water body. The aquatic plants and animals need a particular pH level of about 4.8 to survive. If the pH level falls below that the conditions become hostile for the survival of aquatic life. Acid rain tendency of altering pH and aluminum concentrations greatly affects pH concentration levels in surface water, thereby affecting fish as well as other aquatic life-forms. At pH levels below 5, most fish eggs cannot hatch. Lower pHs can also kill adult fish. Acid rain runoff from catchment areas into rivers and lakes has also reduced biodiversity as rivers and lakes become more acidic. Species including fish, plant and insect types in some lakes, rivers and brooks have been reduced and some even completely eliminated owing to excess acid rain flowing into the waters.

20. Effect on Architecture and Buildings : Acid rain on buildings, especially those constructed with limestone, react with the minerals and corrode them away. This leaves the building weak and susceptible to decay. Modern buildings, cars, airplanes, steel bridges and pipes are all affected by acid rain. Irreplaceable damage can be caused to the old heritage buildings .

21. Vegetation Cover and Plantations:   The damaging effects of acid rain on soil and high levels of dry depositions have endlessly damaged high altitude forests and vegetation cover since they are mostly encircled by acidic fogs and clouds. Besides, the widespread effects of acid rain on ecological harmony have lead to stunted growth and even death of some forests and vegetation cover.

22. Effect on Forests:   It makes trees vulnerable to disease, extreme weather, and insects by destroying their leaves, damaging the bark and arresting their growth. Forest damage due to acid rain is most evident in Eastern Europe – especially Germany, Poland and Switzerland.

23. Effect on Public Health:   When in atmosphere, sulfur dioxide and nitrogen oxide gases and their particulate matter derivatives like sulfates and nitrates, degrades visibility and can cause accidents, leading to injuries and deaths. Human health is not directly affected by acid rain because acid rain water is too dilute to cause serious health problems. However, the dry depositions also known as gaseous particulates in the air which in this case are nitrogen oxides and sulfur dioxide can cause serious health problems when inhaled. Intensified levels of acid depositions in dry form in the air can cause lung and heart problems such as bronchitis and asthma.

24. Other Effects:   Acid rain leads to weathering of buildings, corrosion of metals, and peeling of paints on surfaces. Buildings and structures made of marble and limestone are the ones especially damaged by acid rain due to the reactivity of the acids in the rain and the calcium compounds in the structures. The effects are commonly seen on statues, old grave stones, historic monuments, and damaged buildings. Acid rain also corrodes metals like steel, bronze, copper, and iron.

25. Now that you know why acid rain is a problem, you might be wondering what’s being done to control it. Regulations and new technologies are helping reduce acid rain. EPA’s Acid Rain Program Power plants generate the electricity we use every day. Unfortunately, power plants also produce large amounts of nitrogen oxides and sulfur dioxide—the pollutants that cause acid rain—when they burn fossil fuels, especially coal, to produce energy. Congress passed a law called the Clean Air Act Amendments of 1990, and this law said that EPA should start the Acid Rain Program. The program limits, or puts a cap on, the amount of sulfur dioxide that power plants can release into the air and issues allowances to the power plants to cover their sulfur dioxide emissions. It also reduces the amount of nitrogen oxides that power plants can release Regulations And Measures

26. R educing 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. 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 at EPA’s Green Vehicles Guide.

27. 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.

28. Ways to Prevent Acid Rain Reducing emissions from factories and mines. People can help by using less electricity and mined resources. Reducing the use of too much oil on oars. People can help by buying less oil and its ingredients. R educing the use of carbon dioxide and nitrogen oxides and the burning of coal and wood. Reducing the use of air conditioning by using fans and single energy refrigerator. Close the doors when the air condition is on. Reducing the use of sulphur by recycling paper. People can help by reading newspaper online rather than buying them. R educing the use of oars powered by gasoline. People can help by using cycles are walking for short trip. Reducing the waist of energy by turning off the lights when they aren’t needed, by shutting down utilities when you go on vacations and using solar energy. Producing the use of manufactured material people can help by producing new biodegradable material

29. What i s Greenhouse effect? What are the causes? What are the effects of Greenhouse gases? What can be done? What we can do? GREENHOUSE EFFECT

30. What is Greenhouse effect? The greenhouse effect is the process by which radiation from a planet's atmosphere warms the planet's surface to a temperature above what it would be without its atmosphere. One  is the natural greenhouse effect that keeps our earth climate normal and comfortable on the other hand there is a man made greenhouse effect which is an enhancement of natural greenhouse made from the burning fossil fuels, petroleum, coal and natural gas.

31. Greenhouse effect is important for existence of life on the earth’s surface. Most of the greenhouses looks like the small green houses used to grow plants in winter and colder regions. Greenhouse works by tapping heat from the sun. The greenhouse let in light but doesn’t allow heat from escaping thus making it possible to grow plants in far most colder regions. The same type of greenhouse effect takes place in the car when you park under the sunlight. The greenhouse effect is important. Without the greenhouse effect, the Earth would not be warm enough for humans to live. But if the greenhouse effect becomes stronger, it could make the Earth warmer than usual. Even a little extra warming can  cause problems for humans, plants, and animals. Importance of Greenhouse effect

32. Natural Greenhouse Effect Natural greenhouse effect is made from the heat energy radiated from the sun. Greenhouse gases are naturally due to the presence in the atmosphere. Sunlight goes to the atmosphere warming earth in a cycle. The cycle continuous through the atmosphere as the gases absorb energy at the same time while the leftovers go to the space. Some energy trapped in earth makes it much warmer and comfortable. Enhanced Greenhouse Effect Activities made by humans result in production of greenhouse gases. While the amounts of gas increases in the atmosphere the stability of the greenhouse gases change causing effects on the whole world. Greenhouse effects caused by burning fossil fuels, coal, natural gases, cutting and burning of trees producing carbon dioxide. Greenhouse gases trap heat making the earth warmer and causing global warming.

33. Greenhouse Gases Greenhouse gases and gas that accumulates low-energy infrared radiation these gases consists of : Water vapour Carbon dioxide Methane Ozone Nitrous oxide. ‎

34. Water vapour Produced by the sun's heat emission Makes up a maximum of 47% of the air Causes about two third of the greenhouse effect Higher temperature is equal to more water vapour Carbon dioxide Both man made and natural produced Accounts for 385 PPM of the atmosphere Responsible for about a 25% of the natural greenhouse effect on the earth Carbon sinks help remove CO2 emission from the air Ozone Exist naturally Creates the layer protecting the earth from the sun's high energy UV radiation rays Acts as a Greenhouse gas in the troposphere Methane Produced both by human sources and naturally Less quantity of Methane in the atmosphere than carbon dioxide Methane molecules are more capable of absorbing thermal energy than CO2 molecules

35. Nitrous oxide Produced naturally and by human resources Lower density in atmosphere than carbon dioxide Molecule 300 times more effective as a Greenhouse gas than the CO2 molecule Fluorinated gases Synthetic, powerful greenhouse gases like hydrofluorocarbons , perfluorocarbons, sulfur hexafluoride, and nitrogen trifluoride. E mitted by industrial processes. Fluorinated gases are sometimes used as substitutes for stratospheric ozone-depleting substances (e.g., chlorofluorocarbons, hydrochlorofluorocarbons, and halons). These gases are typically emitted in smaller quantities, but because they are potent greenhouse gases, they are sometimes referred to as High Global Warming Potential  gases.

36. Sources of Greenhouse effect     Electrical Appliances Electrical appliances are amongst the major contributors to the green house effect. Refrigerators, air conditions or some other electric appliances emit gases, known as Chlorofluorocarbons (CFCs), which have added to the greenhouse effect.   Industries Most of the industries today add to the pollution levels and in turn, lead to the greenhouse effect. Aerosol cans, some foaming agents used in the packaging industry, fire extinguisher chemicals and cleaners used in the electronic industry contribute to this. Even some processes of the cement manufacturing industries can be counted amongst the culprits.  

37. Deforestation One of the major reasons for the greenhouse effect is deforestation. With the increase in population, more and more forests are being cut to provide accommodation and other amenities to people. This has led to an increase in the amount of carbon di-oxide in the atmosphere. Add to this, burning of forests, for the purpose of deforestation, and we know why the carbon di-oxide has increased to such enormous levels. Burning of Fossil Fuels We all know that burning of fossil fuels, like petroleum and oil, wood and gas results in release of pollutants into the atmosphere. With time, the consumption of fossil fuels, be it for industrial purposes or consumer purposes, has increased and with it, the pollution levels in the world.

38. Automobiles Automobiles, whether they run on petrol or diesel, create pollution and release harmful gases into the atmosphere. These gases, in turn, create the greenhouse effect in the atmosphere. The forever-increasing use of automobiles has only added to the problem.   Population Growth The high rate of population growth has been indirectly responsible for the greenhouse effect. With the increase in the number of people, the need for things like accommodation, clothes, cars, ACs, etc. has increased. The result is more industries, more cars, more deforestation, and so on.  The ultimate consequence is greenhouse effect.

39. Effects of Greenhouse gases On sea level ‎ Rising temperatures cause water of the oceans along with the sea to increase. Increasing temperature melts ice as it starts to flow into the seas of Antarctic and Greenland . Sea level rise by 20-40 cm causing floods in areas with low coastal area e.g.Bangladesh and Netherland Flood in many area causes danger for living things. On farming Change in the weather affect the growing crops around the world. Crops of wheat and rice grow well in high temperatures. Sugarcane and Maize don't survive in high temperature and end up dying. For the more change in the amount of rainfall affect the growth leading to shortage of food. South Eastern part of the world will be affected as people will suffer without food.

40. On water Countries all over the world will be affected. Britain and Southeast will have a risk of droughts. Africa won't have enough water. On Weather Increasing in greenhouse gases will change weather around the world. North Eastern countries have an increase of temperature. Summers and winters much hotter. Some places will become hotter and wetter while some will be dry and cooler. The world will change with droughts storms and floods. On people and animal Changes make it hard for humans to adjust and adapt to climate. A voiding all the disasters moving from one place to another will be hard. While weather and temperature changes the home of plants and animal will be affected. Moving oceans animal like fishes will be hard. New homes for animals may not be safe causing loss in animal population.

41. Burning fossil fuels such as natural gas, coal, oil and gasoline raises the level of carbon dioxide in the atmosphere, and carbon dioxide is a major contributor to the greenhouse effect and global warming. You can help to reduce the demand for fossil fuels, which in turn reduces global warming, by using energy more wisely.  The following is a list of 10 steps YOU can take to reduce greenhouse gas emissions : Ways to reduce Greenhouse effect Reduce, Reuse, Recycle Buying products with minimal packaging will help to reduce waste. By recycling half of your household waste, you can save 2,400 pounds of carbon dioxide annually.

42. Buy Energy-Efficient Products Home appliances now come in a range of energy-efficient models, and compact florescent bulbs are designed to provide more natural-looking light while using far less energy than standard light bulbs . Use Less Heat and Air Conditioning Adding insulation to your walls and installing weather stripping or caulking around doors and windows can lower your heating costs more than 25 percent, by reducing the amount of energy you need to heat and cool your home. Turn down the heat while you’re sleeping at night or away during the day, and keep temperatures moderate at all times. Install a programmable thermostat because setting it just 2 degrees lower in winter and higher in summer could save about 2,000 pounds of carbon dioxide each year . Get a Report Card from Your Utility Company Many utility companies provide free home energy audits to help consumers identify areas in their homes that may not be energy efficient. In addition, many utility companies offer rebate programs to help pay for the cost of energy-efficient upgrades.

43. Use Less Hot Water Set your water heater at 120 degrees to save energy, and wrap it in an insulating blanket if it is more than 15 years old. Buy low-flow showerheads to save hot water and about 350 pounds of carbon dioxide yearly. Wash your clothes in warm or cold water to reduce your use of hot water and the energy required to produce it. That change alone can save at least 500 pounds of carbon dioxide annually in most households. Plant a Tree             If you have the means to plant a tree, start digging. Trees absorb carbon dioxide and give off oxygen. A single tree will absorb approximately one ton of carbon dioxide during its lifetime.

44. Encourage Others to Conserve Share information about recycling and energy conservation with your friends, neighbors and co-workers, and take opportunities to encourage public officials to establish programs and policies that are good for the environment. These 10 steps will take you a long way toward reducing your energy use and saving you money. Less energy use means less dependence on the fossil fuels that create greenhouse gases and contribute to global warming. Use the "Off" Switch Save electricity and reduce global warming by turning off lights when you leave a room, and using only as much light as you need. And remember to turn off your television, stereo and computer when you're not using them. It’s also a good idea to turn off the water when you’re not using it. While brushing your teeth, shampooing the dog or washing your car, turn off the water until you actually need it for rinsing . Drive Less and Drive Smart Less driving means fewer emissions. Besides saving gasoline, walking and biking are great forms of exercise. Explore the York Region Transit system and check out options for carpooling to work or school.  When you do drive, make sure your car is running efficiently. For example, keeping your tires properly inflated can improve your gas mileage by more than 3 percent. Every gallon of gas you save not only helps your budget, it also keeps 20 pounds of carbon dioxide out of the atmosphere.

45. Replace Your Light Bulbs Wherever practical, replace regular light bulbs with compact florescent light (CFL) bulbs. Replacing just one 60-watt incandescent light bulb with a CFL will save you $30 over the life of the bulb. CFLs also last 10 times longer than incandescent bulbs, use two-thirds less energy, and give off 70 percent less heat. If every Canadian family replaced one regular light bulb with a CFL, it would eliminate 90 billion pounds of greenhouse gases, the same as taking 7.5 million cars off the road.

46. UV Radiation

47. What are UV radiations??? UV {ultra violet}radiations are all the energies that that move at speed of light of light are collectively referred as electro magnetic radiation or light. Pigments inside our retina of our eyes can absorb wavelength of light between 400-700 nm. Collectively referred as visible lights. Stratosphere O and ozone molecules absorbs 77-99%of sums high frequency UV light with wavelength between 150 and 300nm. UVB is a section of UV spectrum with wavelength between 270-320 nm Amount of UVB light received by a location is strongly dependent on latitude and elevation of location. At a high latitude in polar region sun is always low in sky.

48. Positive effects of UVB Triggers vitamin D – UV from the Sun is needed by our bodies to produce vitamin D. Vitamin D helps strengthen bones, muscles and the body’s immune system. It may also lower the risk of getting some kinds of cancers such as colon cancer. Helps some skin conditions – UV is used in the treatment of skin conditions such as psoriasis. This is a condition where the skin sheds its cells too quickly and develops itchy, scaly patches. Exposure to UV slows the growth of the skin cells and relieves the symptoms. Helps some animals’ vision – Some animals (including birds, bees and reptiles) are able to see into the near UV light to locate many ripe fruits, flowers and seeds that stand out more strongly from the background. The fruits, flowers and seeds often appear quite different from how humans see them. For example, when seen in UV light, some flowers have different line markings, which may help direct bees and birds to the nectar . Aids some insects’ navigation – Many insects use UV emissions from celestial objects as references for navigating in flight. This is why a light sometimes attracts flying insects by disrupting their navigation process.

49. Negative effects of UVB Causes skin cancer – UV is an environmental human carcinogen. It’s the most prominent and universal cancer-causing agent in our environment. There is very strong evidence that each of the three main types of skin cancer (basal cell carcinoma, squamous cell carcinoma and melanoma) is caused by sun exposure. Research shows that as many as causes sunburn– UV burns the skin. Sunburn is a burn that occurs when skin cells are damaged. This damage to the skin is caused by the absorption of energy from UV rays. Extra blood flows to the damaged skin in an attempt to repair it, which is why your skin turns red when you are sunburnt. 90% of skin cancers are due to UV radiation . Fades colours – Many pigments (used for coloring food, cosmetics, fabric, plastic, paint, ink and other materials) and dyes absorb UV and change colour. Fabrics, furnishings and paintings need protection from UV (fluorescent lamps as well as sunlight) to prevent colour change or loss.

50. Damages immune system – Over-exposure to UV radiation has a harmful suppressing effect on the immune system. Scientists believe that sunburn can change the distribution and function of disease-fighting white blood cells in humans for up to 24 hours after exposure to the sun. Repeated over-exposure to UV radiation can cause even more damage to the body's immune system. The immune system defends the body against bacteria, microbes, viruses, toxins and parasites (disease and infection). You can see how effective the immune system is by looking at how quickly something decays when it dies and the immune system stops working . Damages eyes – Prolonged exposure to UV or high intensities of UV (for example, in sunbeds) damages the tissues of eyes and can cause a ‘burning’ of the eye surface, called ‘snow blindness’ or photokeratitis . The effects usually disappear within a couple of days, but may lead to further complications later in life. In 1998, the Journal of the American Medical Association reported that even low amounts of sunlight can increase the risk of developing eye damage such as cataracts (which, left untreated, will cause blindness), pterygium and pinguecula . UV damage to the eyes is cumulative, so it is never too late to start protecting the eyes.

51. Ages skin – UV speeds up the aging of skin, since the UV destroys collagen and connective tissue beneath the top layer of the skin. This causes wrinkles, brown ‘liver’ spots and loss of skin elasticity. The difference between skin tone, wrinkles, or pigmentation on the underside of a person's arm and the top side of the same arm illustrate the effects of sun exposure on skin. Usually, the top side of the arm has had more exposure to the sun and shows greater sun damage. Because photo-aging of the skin is cumulative, it is never too late for a person to start a sun protection programme. Otherwise, though a tan may look good now, you could be paying for it with wrinkly leathery skin or skin cancer later . Weakens plastics – Many polymers used in consumer items (including plastics, nylon and polystyrene) are broken down or lose strength due to exposure to UV light.

52. Protection from UVB rays People who get a lot of exposure to ultraviolet (UV) rays are at greater risk for skin cancer . Sunlight is the main source of UV rays, but you don’t have to avoid the sun completely. And it would be unwise to stay inside if it would keep you from being active, because physical activity is important for good health. But getting too much sun can be harmful. There are some steps you can take to limit your exposure to UV rays . Some people think about sun protection only when they spend a day at the lake, beach, or pool. But sun exposure adds up day after day, and it happens every time you are in the sun.

53. Protect your skin with clothing . Clothes provide different levels of UV protection. Long-sleeved shirts, long pants, or long skirts cover the most skin and are the most protective. Dark colors generally provide more protection than light colors. Be aware that covering up doesn’t block out all UV rays. If you can see light through a fabric, UV rays can get through, too. Use sunscreen Sunscreen is a product that you put on your skin to protect it from the sun’s UV rays. But it’s important to know that sunscreen is just a filter – it does not block all UV rays. Sunscreen should not be used as a way to prolong your time in the sun. Even with proper sunscreen use, some UV rays still get through. Because of this, sunscreen should not be thought of as your first line of defense. Consider sunscreen as one part of your skin cancer protection plan, especially if staying in the shade and wearing protective clothing aren’t available as your first options. Way to protect from UVB rays

54. Wear a hat A hat with at least a 2- to 3-inch brim all around is ideal because it protects areas that are often exposed to intense sun, such as the ears, eyes, forehead, nose, and scalp. A shade cap (which looks like a baseball cap with about 7 inches of fabric draping down the sides and back) also is good, and will provide more protection for the neck . Wear sunglasses that block UV rays UV-blocking sunglasses are important for protecting the delicate skin around the eyes, as well as the eyes themselves. Research has shown that long hours in the sun without protecting your eyes increase your chances of developing certain eye diseases. The ideal sunglasses should block 99% to 100% of UVA and UVB rays

55. Thank you