Global Climate Change PDF

Global Climate Change Greenhouse Effect The earth’s atmosphere constitutes several gases such as water vapor (H 2O), carbon dioxide (CO2), methane (CH4), and nitrous oxide (N2O) that absorb and release heat, thus warming the atmosphere. These gases, are called greenhouse gases, and allow mostly vis...

Global Climate Change Greenhouse Effect The earth’s atmosphere constitutes several gases such as water vapor (H 2O), carbon dioxide (CO2), methane (CH4), and nitrous oxide (N2O) that absorb and release heat, thus warming the atmosphere. These gases, are called greenhouse gases, and allow mostly visible light and a certain amount of infrared and ultraviolet (UV) radiation from the sun, to pass through the atmosphere. This is absorbed by the earth’s surface, which transforms it into longer-wavelength infrared radiation (heat), which then rises into the lower atmosphere. Some of this heat escapes into space, while the rest are absorbed by these greenhouse gases and emitted into the lower atmosphere as even longer- wavelength infrared radiation. This natural warming effect of the troposphere is called the natural greenhouse effect, and is essential in maintaining the temperature of the earth’s surface. Human activities such as burning fossil fuels, clearing forests and growing crops release carbon dioxide, methane and nitrogen oxide into the atmosphere in increasing amounts to such as extent that it has resulted in a significant increase in the average temperature of the earth. Global warming is defined as the human-enhanced warming of the atmosphere. Global Climate Change Climate change is the long-term shift in temperatures and weather patterns, that usually occur naturally over a period of time. But the last two hundred years have witnessed human activities to be the main cause of climate change, driven primarily by industrial activities. But a small change of even 1-2°C can cause potentially dangerous shifts in the weather and climate patterns. These real, observable changes are what we designate as climate change impacts. The effects of climate change on the different aspect of the environment are discussed below. 1. More Frequent and Severe Weather Warmer temperatures increase the frequency, intensity, and duration of heat waves, which can pose health risks, particularly for young children and the elderly. Warmer atmosphere can hold more moisture, which is eventually dumped back to the earth, resulting in extreme weather, including increasing number of droughts, intense storms, and floods. Drought conditions jeopardize access to clean drinking water, fuel wildfires, and result in dust storms, extreme heat events, and flash flooding. At the opposite end of the spectrum, heavier rains cause streams, rivers, and lakes to overflow, which damages life and property, contaminates drinking water, creates hazardous-material spills, promotes mold infestation and unhealthy air. A warmer, wetter world also promotes food-borne and waterborne illnesses and disease-carrying insects such as mosquitoes, fleas, and ticks. 1 2. Melting Ice Caps When solar radiation hits snow and ice, approximately 90% of it is reflected back out to space. As global warming causes more snow and ice to melt each summer, the ocean and land that were underneath the ice are exposed at the Earth’s surface. Because they are darker in color, the ocean and land absorb more incoming solar radiation, and then release the heat to the atmosphere. In this way, melting ice causes more warming and so more ice melts. 3. Melting Permafrost Releases Greenhouse Gases. Global warming is causing soils in the polar regions that have been frozen for as much as 40,000 years to thaw. As they thaw, carbon trapped within the soils is released into the atmosphere as carbon dioxide and methane. These gases, released to the atmosphere, cause more warming, which then thaws even more of the frozen soil 4. Higher Air Pollution Rising temperatures also worsen air pollution by increasing ground level ozone, which is created when pollution from cars, factories, and other sources react to sunlight and heat. Ground-level ozone is the main component of smog, and the hotter things get, the more of it we have. Dirtier air is linked to higher hospital admission rates and higher death rates for asthmatics. It worsens the health of people suffering from cardiac or pulmonary disease. And warmer temperatures also significantly increase airborne pollen, which is bad news for those who suffer from hay fever and other allergies. 5. More Acidic Oceans Oceans are becoming more acidic, due in large part to their absorption of some of our excess emissions. As this acidification accelerates, it poses a serious threat to underwater life, particularly creatures with calcium carbonate shells or skeletons, including molluscs, crabs, and corals. This can have a huge impact on shellfisheries and other industries that depend on the harvest of oysters, clams, and other shelled molluscs. 6. Rising Sea Levels Global sea level has risen by about 8 inches since the year 1880, at a rate of 1-2 mm each year. This is the result of added water from melting land ice and the expansion of seawater as it warms. Polar regions are particularly vulnerable to a warming atmosphere. Average temperatures in the Arctic are rising twice as fast as they are elsewhere on earth. And it has been estimated that by the year 2100, our oceans will be 1-8 feet higher. This increase threatens coastal systems and low-lying areas, including entire island nations, including Some of the world's largest cities, including New York, Los Angeles, Miami, Mumbai, 2 Sydney, and Rio de Janeiro. For example, for a low-lying island nation like the Maldives in the Indian Ocean, even a small rise in sea levels could spell disaster for of its people. About 80% of the 1,192 small islands making up this country lie less than 1 above sea level. Rising sea levels and higher storm surges during this century could flood most of these islands and their coral reefs. Next, let us talk about the increasing death rates due to climate change. 7. Higher Death Rates Today's scientists point to climate change as "the biggest global health threat of the 21st century." It's a threat that impacts all of us—especially children, the elderly, low-income communities, and minorities—in a variety of direct and indirect ways. As temperatures spike, so does the incidence of illness, emergency room visits, and death. Climate change also has impacts on the wildlife species, both terrestrial and aquatic. Climate change has resulted in higher wildlife extinction rates. 8. Higher Wildlife Extinction Rates As humans, we face a host of challenges, due to climate change, but we're certainly not the only ones catching the heat. As land and sea undergo rapid changes, the animals that inhabit them are doomed to disappear if they don't adapt quickly enough. Some will make it, and some won't. Many land, freshwater, and ocean species are shifting their geographic ranges to cooler climes or higher altitudes, in an attempt to escape climate warming. They're changing seasonal behaviours and traditional migration patterns as well. And yet, many face "increased extinction risk due to climate change." a 2015 study has revealed that vertebrate species—animals with backbones, like fish, birds, mammals, amphibians, and reptiles—are disappearing 114 times faster than they should be, a phenomenon that has been linked to climate change, pollution, and deforestation. Let us know understand the important factors that are responsible for these devastating climate change events. The first and foremost driver of climate change is the greenhouse effect, which is mostly driven by human activities. Causes of Global Climate Change 1. Human Vs Natural Causes Scientists have pieced together a record of the earth’s climate by analyzing a number of indirect measures of climate, such as ice cores, tree rings, glacier lengths, pollen remains, and ocean sediments, and by studying changes in the earth’s orbit around the sun. This record shows that the climate varies naturally over a wide range of time scales. but this variability does not explain the warming that’s been observed since the 1950s. it is extremely likely (> 95%) that human activities have been the dominant cause of this warming. CO2 produced by human activities is the largest contributor to global warming. Methane is a more powerful greenhouse gas than CO2, but has a shorter lifetime. Nitrous oxide is a long-lived greenhouse gas that accumulates in the atmosphere over decades to centuries. Currently, the CO2 levels are at a record high of 414.8 ppm, a concentration that has not been seen on Earth for millions of years. Some of these activities include: Burning coal, oil and gas, producing carbon dioxide and nitrous oxide. Cutting down forests (deforestation). Trees help regulate the climate by absorbing CO 2 from the atmosphere. When cut down, that beneficial effect is lost and the carbon stored in the trees is in turn released into the atmosphere, adding to the greenhouse effect. 3  Manufacturing and industry produce emissions, mostly from burning fossil fuels to produce energy for making things such as cement, iron, steel, electronics, plastics, clothes, and other goods. Mining and other industrial processes also release gases. Increasing livestock farming such as cows and sheep produce large amounts of methane when they digest their food. Fertilisers containing nitrogen produce nitrous oxide emissions. Fluorinated gases are emitted from equipment and products that use these gases. Such emissions have a very strong warming effect, up to 23,000 times greater than CO2. Let us look at certain natural events that can affect the earth’s surface temperature. The first factor is a change in the Reflectivity or Absorption of the Sun’s Energy. 2. Reflectivity or Absorption of the Sun’s Energy Activities such as agriculture, road construction, and deforestation can change the reflectivity of the earth's surface, leading to local warming or cooling. This effect is observed in the form of heat islands, which are urban centres that are warmer than their surroundings, less populated areas. One reason for these effects is that urban centres house more buildings, pavements, and roofs that tend to reflect less sunlight than natural surfaces. Dark objects and surfaces, like the ocean, forests, and soil, tend to absorb more sunlight. Light-coloured objects and surfaces, like snow and clouds, tend to reflect more sunlight. About 70% of the sunlight that reaches the earth is absorbed. Natural changes in the earth’s surface, like the melting of sea ice, have contributed to climate change in the past, often acting as feedbacks to other processes. 3. Changes in the Earth’s Orbit and Rotation Changes in the earth’s orbit and its axis of rotation have had a big impact on climate in the past. For example, the amount of summer sunshine on the Northern Hemisphere, which is affected by changes in the planet’s orbit, appears to be the primary cause of past cycles of ice ages, during which the earth has experienced long periods of cold temperatures (ice ages), as well as shorter interglacial periods (i.e., periods between ice ages) of relatively warmer temperatures. 4. Variations in Solar Activity Variations in the sun’s energy output can also affect the intensity of the light that reaches the earth’s surface. Satellites have been measuring the amount of energy that the earth receives from the sun since 1978. And These measurements show no net increase in the sun’s output, even as global surface temperatures have risen. 5. Volcanic Activity Explosive volcano eruptions can throw particles (e.g., SO2) into the upper atmosphere, where they can reflect enough sunlight back to space to cool the surface of the planet for several years. These particles are an example of cooling aerosols, which reflect the sunlight away from the 4 earth’s surface. Volcanic particles from a single eruption do not produce long-term climate change because they remain in the atmosphere for a much shorter time than greenhouse gases. 6. Changes in Naturally Occurring Carbon Dioxide Concentrations Over the last several hundred thousand years, carbon dioxide levels have varied in tandem with the glacial cycles. During warm interglacial periods, carbon dioxide levels were higher. During cool glacial periods, carbon dioxide levels were lower. These changing concentrations have acted as a positive climate feedback, amplifying the temperature changes caused by long-term shifts in the earth’s orbit. 5  Kyoto Protocol & Paris Agreement Global Climate Action in the form of Treaties & Conferences In this section, we will discuss some of the measures taken in the form of conferences and treaties that were formulated to mitigate the anthropogenic effects of global climate change. The earliest among these efforts was the treaty known as the United Nations Framework Convention on Climate Change (UNFCCC), followed by the Kyoto protocol, the annually conducted Conference of parties. United Nations Framework Convention on Climate Change (UNFCCC) The UNFCCC is an international treaty that was established to combat “dangerous human interference with the climate system". The UNFCCC was informally known as the Earth summit, and was held at Rio de Janeiro from 3-14 June 1992. Its main objectives were to Stabilize greenhouse gas concentrations in the atmosphere at a level that would prevent dangerous anthropogenic interference with the climate system Set non-binding limits on greenhouse gas emissions for individual countries. It did not contain any enforcement mechanisms, due to which it was deemed unsatisfactory in reaching the required emission reduction goals. Conference of the Parties (COP) Conference of the Parties (COP) is the supreme decision-making body of the UNFCCC, which meets annually to assess progress in dealing with climate change. The first COP meeting was held in Berlin, Germany in March 1995. Usually, COP meets in Bonn, which is the seat of the secretariat, unless any member country offers to host the session. The latest COP was its 26th meeting, held from 31 October-12 November 2021. At COP-26, India pledged to become a net-zero carbon emitter by 2070 and announced enhanced targets for renewable energy deployment and reduction in carbon emissions. The Kyoto Protocol Kyoto Protocol is an international treaty that was signed in 1997. it was the first implementation of measures formulated under the UNFCCC. It ran from the year 2005-2020. It was first adopted in Kyoto, Japan on the 11 December 1997 and entered into force on 16 Feb 2005; currently, there are 192 parties in the protocol. The Kyoto Protocol had two commitment periods, the first of which lasted from 2008 to 2012. It was amended again in 2012 to include the Doha amendment for the period 2013-2020. Salient points of the Kyoto Protocol The Kyoto Protocol established three categories of signatory states, namely developed countries, developed countries with special financial responsibilities, and the third, developing countries. The developed countries, also called Annex 1 countries, originally consisted of 38 states, 13 of which were Eastern European states in transition to democracy and market economies, and the European Union. 1  Annex II countries consisted of Developed countries with special financial responsibilities. E.g., Russia, Baltic states, Central and Eastern European states. Those countries not categorized under the Annex I and II countries were categorized as developing countries, including India and China, for example. The protocol was based on the principle of common but differentiated responsibilities: it acknowledged that individual countries have different capabilities in combating climate change, based on their economic development, and therefore placed the obligation to reduce current emissions on to developed countries on the basis that they are historically responsible for the current levels of greenhouse gases in the atmosphere. This included the Annex-I countries that were legally bound to lower their GHG emissions to 1990 levels. They were called upon to adopt national policies and take appropriate measures to mitigate climate change. Goals of the Kyoto Protocol The Kyoto Protocol applied to the seven greenhouse gases listed in carbon dioxide (CO 2), Methane (CH4), nitrous oxide (N2O), hydrofluorocarbons (HFCs), perfluorocarbons (PFCs), sulfur hexafluoride (SF6), nitrogen trifluoride (NF3), which was added during the Doha amendment. Emission reduction targets were assigned for different countries, expressed as levels of assigned amount units (AAUs). The Kyoto protocol was legally binding, and any Annex-I or II country failing to meet targets were penalized. The US did not ratify the Kyoto Protocol, while Canada denounced it in 2012. The Kyoto Protocol was ratified by all the other Annex I Parties. All countries that remained parties to the Kyoto Protocol met their first commitment period targets. developing countries were required to only report their emissions to the UNFCCC. Flexibility mechanisms were established to help countries achieve their emission targets. Flexibility Mechanisms of the Kyoto Protocol The Protocol defines three "flexibility mechanisms" that can be used by the Annex I Parties in meeting their emission limitation commitments. These mechanisms aimed to lower the overall cost of achieving emission targets. The three mechanisms are: International Emissions Trading (IET) The Clean Development Mechanism (CDM) Joint Implementation (JI). 2 International Emissions Trading (IET) International Emissions Trading (IET) allowed countries to trade unused emissions to other countries that exceeded their targets. For example, Country A has 100 emission units, of which it has used only 70. It can trade the remaining 30 units to another country B that has exceeded their permissible emission units. Thus, a new commodity was created in the form of emission reductions. Since CO2 is the principle GHG, it is also referred to as carbon trading. Countries under the Kyoto protocol that were assigned targets for reducing their GHG emissions were expressed as levels of allowed emissions, or assigned amount units (AAUs). Emission trading currently operates across 35 countries in 4 continents. Clean Development Mechanism (CDM) Clean Development Mechanism (CDM) is a United Nations-run scheme that allows countries to fund GHG- reducing projects in other countries and claim the saved emissions as part of their own efforts to meet international emissions targets. These projects were also aimed at assisting developing countries achieve sustainable development and reduce their own carbon footprint. Here, let me introduce you to another form of carbon trading, known as Certified Emission Reductions (CER) units, also called as a carbon credit. Carbon Trading CER is a type of emission unit issued under the Clean Development mechanism to Annex-1 countries to help them comply with their emission reduction targets. CERs can be purchased either from a primary market (i.e., the country that makes the reduction) or from a secondary market (resold from a marketplace). CERs give the owner/country the right to emit 1 metric tonne of CO2 or other equivalent GHG. CERs can be gained by developing projects that reduce GHG emissions. Joint Implementation (JI) scheme Under the Joint Implementation (JI) scheme, any Annex-I country could invest in a project to reduce GHG in any other Annex-I country as an alternative to reducing them domestically. This was introduced to lower the cost of reducing GHGs, as it may be expensive to do so in certain countries and cheaper in others. Under the JI scheme, another form of 3 carbon trading, known as the Emission Reduction Unit (ERU) was introduced. 1 ERU represents the reduction of 1 tonne of CO2. Paris Agreement The Paris agreement, or the Paris Climate Accords is an international treaty on climate change that was adopted in 2015. It covers climate change mitigation, adaptation and finance. The agreement was negotiated by 196 parties at the 2015 UNFCCC near Paris, France. It opened for signature on 22 April 2016 (Earth Day), and entered into force on 4 November 2016. As of November 2021, 193 members of the UNFCCC ratified the Paris agreement, and only 4 countries have not ratified, of which Iran is the major emitter. USA withdrew from the agreement in 2020, but re-joined in 2021. The long-term goal of the Paris agreement was to restrict the rise in mean global temperature to 95% of hydrogen is produced from steam reforming of natural gases. But there is disadvantages associated with this process 1. natural gas is already rapidly becoming limited source and more expensive one. 2. It is also a fossil fuel so the carbon dioxide which is released in the reformation process increase the greenhouse effect and global warming. Photo courtesy wikipedia Let’s move to the second method of Hydrogen Production That is Thermochemical Water Splitting Thermochemical water splitting uses high temperatures nearly 500°–2000°C which may be comes from concentrated solar power or from the waste heat from the nuclear power stations. In this process chemical reactions would takes place and then produce hydrogen and oxygen from water. The chemicals such as cerium oxide or copper chloride can be used in the processes. Usually these chemicals are reused within each cycle and consumes only water and produces hydrogen and oxygen. Solar- or nuclear-driven high-temperature thermochemical water-splitting cycles produce hydrogen with near-zero greenhouse gas emissions using water and sunlight or nuclear energy. Photo courtesy Wikipedia Let’s move to the third method of Hydrogen Production ELECTROLYTIC PROCESSES. Water can be splitted into oxygen and hydrogen through a process called electrolysis. Electrolysis is the process of using electricity to split water into hydrogen and oxygen. Electrolysis is a promising option for carbon-free hydrogen production from renewable and nuclear resources. Electrolytic processes take place in an electrolyzer. An electrolyzer creates hydrogen from water molecules. Electrolyzers can range from small-scale hydrogen production to large-scale production facilities that is well-suited for non-greenhouse-gas-emitting electricity production. Electrolyzers consist of an anode and a cathode which is separated by an electrolyte. Different electrolyzers function in different ways mainly due to the different type of electrolyte material involved and the ionic species it conducts. First Water reacts at the anode to form oxygen and positively charged hydrogen ions and electrons. The electrons flow through an external circuit and the protons selectively moves across the polymer electrolyte membrane (PEM) to the cathode. At the cathode hydrogen ions or protons combine with electrons from the external circuit to form hydrogen gas. Anode Reaction is 2H2O reacts and form O2 + 4H+ + 4e- Cathode Reaction is 4H+ + 4e- → 2H2 Hydrogen produced via electrolysis can result in virtually zero greenhouse gas emissions depending on the source of the electricity used. however the production cost needs to be reduced in the future. Photo courtesy Wikipedia Photo courtesy https://commons.wikimedia.org/ Let’s move to the fourth method of Hydrogen Production SOLAR-DRIVEN PROCESSES Solar-driven processes use light as the agent for hydrogen production. A typical Solar–hydrogen energy cycle consist of three components. First one is electrolyzer. Second one is hydrogen storage tank and third one is hydrogen fuel cell. In a solar–hydrogen energy cycle a solar powered electrolyzer is used to convert water into hydrogen and oxygen. Hydrogen and oxygen produced thus are stored in containers for later use. The stored hydrogen can be used by a fuel cell to produce electricity when no sunlight is available. Solar–hydrogen energy cycle is also called as Solar-hydrogen revolution There are a few solar-driven processes including 1. Photobiological processes 2. Photoelectrochemical processes and 3. solar thermochemical processes. Photobiological hydrogen production processes use the natural photosynthetic activity of bacteria and green algae to produce hydrogen. The photobiological process uses microorganisms and sunlight to turn organic matter into hydrogen. Photoelectrochemical processes use specialized semiconductors to split water into hydrogen and oxygen. Solar thermochemical hydrogen production uses concentrated solar power to drive water splitting reactions often with the help of reagents such as metal oxides. Photo courtesy Ali, Suhaib. (2022). SOLAR-HYDROGEN SYSTEMS FOR REMOTE AREA POWER SUPPLY. THE LAST METHOD OF HYDROGEN PRODUCTION BIOLOGICAL PROCESSES Biological processes use microbes such as bacteria and microalgae and can produce hydrogen through biological reactions. In microbial biomass conversion the microbes break down organic matter like biomass or wastewater to produce hydrogen Photo courtesy https://commons.wikimedia.org/ Let me explain how to utilize hydrogen for generating heat or electricity Typically Hydrogen Fuel cells are used to generate electricity Let’s discuss what is meant by Hydrogen Fuel Cell? To know about hydrogen fuel cell at first you should know what a fuel cell is? A fuel cell is a device that can convert the chemical energy into electrical energy. Thus often this fuel cell is compared to batteries. Both fuel cells and batteries produce energy via chemical reactions and transfer that energy into usable electric power. In a typical fuel cell hydrogen gas is supplied to anode. At anode these hydrogen molecules divide into protons and electrons. The produced electrons flow through wires and generate electricity while the protons pass through a membrane and combine with oxygen gas at cathode to form water vapor. Overall Hydrogen fuel cells produce electricity by combining hydrogen and oxygen atoms. Due to the applications of hydrogen fuel cells these two elements react and produce a huge amount of energy. In fuel cells three product we can harvest heat electricity and water. Different types of fuel cells are available for a wide range of applications. Small fuel cells can power laptop and computers and even cell phones. Large fuel cells can supply electricity to electric power grids and supply emergency power in buildings and supply electricity in places that are not connected to electric power grids. Electric current Fuel in e− Air in − e e− + e− H H2 O2 H+ Unused Excess air, water, H2O and heat fuel out Anode Cathode Electrolyte Photo courtesy https://commons.wikimedia.org/ In this module we should learn another important terminology that is Hydrogen Economy The term “hydrogen economy” refers to the vision of using hydrogen as a low or zero carbon energy sources. For example replacing natural gas as a heating fuel or replacing gasoline as a transport fuel. It is expected that in a near future hydrogen is produced from a variety of energy sources stored for later use transported to where it is needed and then converted into heat and electricity. Photo courtesy https://commons.wikimedia.org/ Let me explain various applications of hydrogen fuel cells hydrogen fuel cells would eliminate most of the air pollution problems we face today. It would also greatly reduce the threats of global warming and climate change because using it emits no carbon dioxides. Hydrogen also provides more energy per gram than does any other fuel making hydrogen the ideal aviation fuel. Hydrogen is considered as an alternative vehicle fuel. A fuel cell may be. two to three times more efficient than an internal combustion engine running on gasoline. Today hydrogen is used mostly in oil refining industries and fertilisers industries. Another promising application is in homes where a fuel-cell stack. about the size of a refrigerator could provide heat hot water and electricity. Honda company has developed a home unit hydrogen generator that produces hydrogen from the methane. Many Japanese homeowners using such units to produce their electricity and hot water Finally we can discuss now Advantages and disadvantages of hydrogen energy Advantages: Hydrogen can be produced from ample water. It has low environmental impact. It is considered as renewable energy if hydrogen is produced from the renewable energy for example as indicated in solar hydrogen cycle. It is a good substitute for oil. It is easier to store than the electricity and safer than gasoline and natural gas. Today many high efficiency hydrogen fuel cells are commercially available and are in developmental stages. Disadvantages: Hydrogen is not found in nature as H2 molecule. hydrogen is chemically locked-up in water and in organic molecules such as methane and gasoline. Hence we need to spend an energy to produce hydrogen from these compounds. Therefore net energy is negative. It is difficult to store hydrogen in fuel tank which is the main problem of using hydrogen fuel cell in cars. Fuel cells are the best way to use hydrogen to produce electricity to operate vehicles but current versions of hydrogen fuel cells are expensive.  Electric and CNG vehicles We are going to learn about Electric and CNG vehicles which is the future in transportation sector Let’s begin with What are Electric Vehicles? An Electric Vehicle is a vehicle that operates on an electric motor and uses electrical energy stored in batteries instead of an internal combustion engine that generates power by burning a mixture of fuel and gases. Unlike vehicles with combustion engines electric vehicles do not produce exhaust gases during operation. This makes electric vehicles more environmentally friendly than the vehicles with conventional technology. Electric vehicle is considered as a possible replacement for the current-generation automobiles in the near future to address environmental challenges. Photo courtesy https://commons.wikimedia.org/ Let see how does Electric Vehicles work? Electric Vehicles needs 3 important components 1. Controllers 2. Battery 3. Electric motor When the pedal is pushed the controller gathers energy from the battery Then Controller delivers the appropriate amount of electrical energy to the motor Thus, this delivered electric energy transforms to mechanical energy therefore Wheels turn vehicles move. Photo courtesy https://commons.wikimedia.org/ Electric Vehicles are not an new concept. In 1830 - first electric carriage was built. In 1891 the first electric automobile was built in the USA. Let’s discuss Types of electric vehicles Four types of electric vehicles on the toad today 1. BEV that is Battery electric vehicles 2. PHEV that is Plug-in hybrid electric vehicle 3. HEV that is hybrid electric vehicle 4. Finally, FCEV that is Fuel-cell electric vehicle Let’s discuss each one of them one by one What is BEV: Battery electric vehicles. Another name for Battery electric vehicles is All-Electric Vehicle (AEV) A Battery electric vehicle runs entirely on a battery and without a need of an internal combustion engine. It is powered by electricity from an external source usually the public power grid. This electricity is stored in onboard batteries that turn the vehicles wheels using one or more electric motors. BEVs can be charged at home overnight providing enough range for average journeys. However longer journeys or those who require a lot of hill climbs may require charging multiple times before you reach your destination. The typical charging time for an electric car can range from 30 minutes and up to more than 12 hours. This all depends on the speed of the charging station and the size of the battery. In the real world range is one of the biggest concerns for electric vehicles but is something that is being addressed by Research and Development and industry. Photo courtesy https://commons.wikimedia.org/ EV batteries are charged by plugging the vehicle into an electric power source. EVs are far more efficient than conventional vehicles and produce no tailpipe emissions. They also typically require less maintenance because the battery motor and associated electronics require little to no regular maintenance. Further electric vehicles experience less brake wear thanks to regenerative braking systems. Electric vehicles have fewer moving parts relative to conventional vehicles. Electric vehicles do not contain the typical liquid fuel components such as a fuel pump fuel line or. fuel tank. Next, we can discuss PHEV- Plug-in hybrid electric vehicle Plug-in hybrid electric vehicle runs mostly on a battery that is recharged by plugging into the power grid. It is also equipped with an internal combustion engine which run on a gasoline or diesel fuel that can recharge the battery and/or to replace the electrical inverter when the battery is low and when more power is required This makes them better for travelling long distances as you can switch to traditional fuels rather than having to find charge points to top up the battery. PHEVs have smaller battery packs which means it can be used for medium range distances. Of course, the same disadvantages that apply to combustion engine vehicles also apply to PHEVs such as the need for more maintenance engine noise emissions and the cost of petrol. Photo courtesy https://commons.wikimedia.org/ Next, we can discuss HEV Hybrid electric vehicle An HEV has two complementary drive systems first one is a gasoline engine and fuel tank and the second one is an electric motor battery and controls. The engine and the motor can simultaneously turn the transmission which powers the wheels. The main difference between already discussed electric vehicles is HEV cannot be recharged from the power grid. Their energy comes entirely from gasoline and regenerative braking systems. Photo courtesy https://commons.wikimedia.org/ Next, we can discuss FCEV - Fuel-cell electric vehicle more often it is called as hydrogen fuel cell electric vehicle. A FCEV creates electricity from hydrogen and oxygen instead of storing and releasing energy like a rechargeable battery. Because of vehicles efficiency and water-only emission most of the experts consider these cars to be the best electric vehicles even though they are still in development phases. Let’s discuss about the Advantages and disadvantages of Electric vehicles Electric vehicles have low running costs as they have fewer moving parts for maintaining Electric vehicles and also environmentally friendly as they use little or no fossil fuels like petrol or diesel. Compared to an internal combustion engine battery powered electric vehicles have approximately 99% fewer moving parts that need maintenance. Also, there is no need to lubricate the engines. Electric vehicles create very little noise. Electric cars put a control on noise pollution as they are much quieter. In electric vehicles there is no exhaust no spark plugs no clutch or gears. Finally, it is Easy Driving – you can operate an electric car with just the accelerator pedal brake pedal and steering wheel. Electric vehicles don’t burn fossil fuels instead uses rechargeable batteries. Electric vehicles are energy efficient For examples in electric vehicles batteries convert 59 to 62 percent of energy into vehicle movement while gas powered vehicles only convert between 17 and 21 percent. Electric cars reduce emission. Electric cars are 100 percent eco-friendly as they run on electrically powered engines. Emission reduction including reduced usage of fuel is another advantage for all-electric vehicles. Because they rely on a rechargeable battery Electric cars are high performance and low maintenance The driving experience can also be fun because AEV motors react quickly making them responsive with good torque. AEVs are digitally connected with charging stations providing the option to control charging from an even a mobile app. Finally electrical vehicles are Safe to Drive. - An electric car is safer to use given their lower center of gravity which makes them much more stable on the road in case of a collision. Disadvantages of electric vehicles The Initial Investment on electric vehicles is Expensive. Keep in mind Electricity isn’t Free. Electric cars can travel only less distances. AEVs on average have a shorter range than gas- powered cars. Most models ranging between 100 and 200 km per charge and some luxury models reaching ranges of 300 miles per charge. This may be an issue when looking at AEVs if you frequently take long trips. Availability of charging stations can make AEVs less suitable for activities like road trips. Electric cars take longer to “refuel”. Fueling an all-electric car can also be an issue. Recharge Points or Electric fueling stations are still in the development stages. Fully recharging the battery pack can take up to 8 hours and even fast charging stations take 30 minutes to charge. Thus, Electric car drivers have to plan more carefully because running out of power can’t be solved by a quick stop at the charging stations. Electric cars are more expensive and battery packs may need to be replaced. Depending on the type and usage of battery batteries of almost all electric cars are required to be replaced every 3-10 years. The battery packs within an electric car are expensive and may need to be replaced more than once over the lifetime of the car. These All-electric vehicles are more expensive than gas- powered cars. Overall all-electric vehicles like any vehicle must be assessed based on personal needs and vehicle usage. There are many pros to owning an electric vehicle such as fuel savings and reduced emissions, but this can come at the cost of relying on battery charging and higher costs. Electric vehicles create very little noise. Silence can be a bit disadvantage as people like to hear the noise if they are coming from behind them. Therefore, it can lead to accidents in some cases. There are still challenges with electric vehicle batteries as they can experience thermal runaway which have for example caused fires or explosions. Let’s move to the second topic CNG operated vehicles What is CNG? CNG also known as compressed natural gas It is an eco-friendly alternative to gasoline. CNGs are made by compressing natural gas for example methane down to less than 1% of its volume at standard atmospheric pressure or compressed to 3000 - 3600 psi. CNG fuel is safer than gasoline and diesel because it is non-toxic. This natural gas is the same gas that you use daily to cook on the stove. The use of CNG fuel is becoming more popular with both commercial and non-commercial vehicles. Compressed natural gas is under more pressure and thus takes up a smaller volume than ordinary natural gas. Compressed Natural Gas is colorless non-carcinogenic and non-toxic. CNG is inflammable and lighter than air. CNG is superior to petrol it operates at one-third the cost of conventional fuel and hence increasingly becoming popular with automobile owners. Commonly referred to as the green fuel because of its lead free characteristic and it reduces harmful emissions and is non- corrosive. CNG is comprised of mostly methane gas. When CNG reaches the combustion chamber it mixes with air will be ignited by a spark and generates energy which moves the vehicle. Please remember it is not a liquid fuel and is not the same as LPG Liquified Petroleum Gas which consists of propane and butane in liquid form. Also, CNG is not to be confused with liquefied natural gas. Photo courtesy https://commons.wikimedia.org/ Why CNG is better than traditional petrol? CNG is one of the most viable alternatives to traditional liquid fuels for vehicles. CNG is one fifth the price of gasoline resulting in substantial savings in fuel costs. CNG reduces maintenance costs since it contains no additives and burns cleanly leaving no by- products of combustion to contaminate your spark plugs and engine oil. The engine oil also remains clean which minimizes engine wear and requires less frequent changes. CNG is more environment friendly and CNG engines are much quieter due to the higher octane rating over gasoline. CNG produces less exhaust emissions and as a result harmful emissions such as carbon monoxide carbon dioxide and nitrous oxide are generally reduced by as much as 95% when compared to gasoline powered vehicles. Disadvantages of CNG: CNG Gas stations have limited availability. In India some states have high number of CNG fuel stations. CNG tank requires large space, and it is heavy. So, it affects reliability and vehicle performance. Another issue with CNG vehicles is a longer breaking distance due to the added weight of the fuel storage system. Further the composition of natural gas itself can be an issue. CNG is mainly comprises of methane which is a greenhouse gas which could contribute to climate change if a leak existed.  Introduction; Solar energy-thermal and photovoltaic What is energy? What is the need for energy resources? The term energy is derived from the Greek word en-ergon meaning that in-work To perform any work in this world we require energy. Let’s take an example To cook our food, we need energy. To travel from one place to another place we need energy. To keep vegetables and fruits afresh inside the refrigerator we need energy To heat our house, we need energy To cool down our rooms we need energy To work with our mobile phones and laptop we need energy. We are using some source of energy for a variety of applications. If you take the history humans started using firewood and plant materials for cooking their foods. Humans used animals for transportation such as a horse for riding During the last century breakthroughs have happened. That is Benjamin Franklin discovered the electricity. Followed by him Michael Faraday invented the electric dynamo the machine which converts mechanical energy into electricity in the year 1831 Thomas Alva Edison invented the light bulb which will glow when electricity passes Nikola Tesla discovered the AC current motor which would convert electrical energy into mechanical energy. We can’t even imagine life without fuel or electricity, right? The energy consumption of a country is usually considered as a sign of its development. Let’s discuss about Types of Energy Resources Energy resources are broadly classified into renewable or non-renewable energy resources. Non-renewable energy resources are exhaustible and cannot be renewed. It can be available only for a limited period of time. Once they are consumed soon, they will run out. On the other hand, Renewable energy resources are inexhaustible and they can be renewed. They are replaced as fast as they are used. Can you say some renewable and non-renewable energy resources? Photo courtesy https://commons.wikimedia.org/ Non-renewable Energy Resources are Fossil fuels such as oil petroleum diesel coal and natural gas. The drawback with fossil fuels is if fossil fuels are burned to generate energy, they may release pollutants or carbon dioxide or other greenhouse gases into the atmosphere which will lead to global temperatures rising. It is called global warming. Next Renewable Energy Resources Examples of renewable energy resources are solar energy geothermal energy wind energy biomass hydroelectric power and tidal energy. These energy resources are inexhaustible and can be renewed or replaced faster than we can use them. Important Things to Consider about Energy Resources Whether renewable or non-renewable energy resources two important things must be considered. The first one is successfully making a useful form of energy from the energy resource. For example, how to harvest electricity from the sun. Another one is Net Energy Net energy is the amount of high-quality energy produced from an energy resource minus the amount of energy required to develop it. Let’s discuss this by taking one example if we get much less energy as output by burning fuel than the input energy to produce it. Then That particular fuel is probably not a practical energy resource. For example, nuclear power. In order to produce nuclear energy, we need to spend a lot of energy on mining and extraction of uranium isotopes and enrichment of uranium fuels and fuel rod fabrications. Further after electricity is generated from uranium, we need to spend a lot of money on the storage of used fuel rods safely. Thus, net energy will be low On the other hand, for another fuel net energy is high but if it creates large amounts of pollution that particular fuel also may not be the best choice for an energy resource. For example, a coal-based thermal power plant produces a lot of energy. Net energy will be higher than the nuclear energy. However, if you consider the amount of CO2 release or greenhouse gas emission is very high in coal-based power plants. Thus, even though net energy is high in coal-based thermal energy this is not an eco-friendly energy resource. In this module we are going to learn more about renewable energy recourses First, we can start with SOLAR ENERGY. Sun is an abundant source of energy, and it is inexhaustible. Solar energy actually supports all life on earth Thus, directly or indirectly the sun is the source of all the energy available on earth. Solar energy applications can be classified into two categories one is direct solar energy and another one is indirect solar energy. Photo courtesy https://commons.wikimedia.org/ Plants need sunlight to grow. Animals and humans were dependent on plants for their food and for oxygen. Once plants and animals die, they will reach underground. After millions of years later these dead plants and animals turn into fossil fuels such as coal and oil. Hence coal and oil are regarded as indirect solar energy. Solar energy causes pressure differences in the atmosphere and this causes the movement of air that is wind. So, wind energy is actually a byproduct of solar energy. Let’s take the water cycle Water evaporates because of heat condenses to form clouds and precipitates back to earth in the form of rain and snow. This water can be stored in dams to produce hydroelectricity. Hence hydroelectricity is an indirect form of solar energy. Now we came to an important discussion that is Direct solar energy usage Direct solar energy can be obtained using two methods. The first one is Thermal example is Solar radiation can be absorbed in solar collectors to provide hot water. The second one is Photovoltaic. For example, solar energy can be converted directly into electricity using photovoltaic panels which are normally mounted on roofs. Let me explain Direct solar energy applications Solar energy is abundant found everywhere and has no political barrier everlasting and available for free of cost Solar energy is one of the cleanest and most easily accessible sources of energy. Direct solar energy can be harvested in various ways; there are three ways to harness solar energy First one is passive solar energy system Second one is active solar energy system Third one is photovoltaic. First, we can discuss about how we can utilize Solar thermal heat for various applications It is not a new concept Solar thermal heat was used to evaporate seawater to produce salt Solar thermal heat was used to dry our food Solar thermal heat was used to dry our clothes These are a few examples of passive solar energy applications. Photo courtesy https://commons.wikimedia.org/ The best example of a passive solar energy system is a solar cooker which is a device that uses sunlight to cook food. Solar cookers work without any large complex systems of lenses or mirrors We all know that when sunshine falls on a dark surface or black colored surface it absorbs solar energy, and it heats up. The solar cooker uses the same principle. Inside a solar cooker a glass-covered chamber is painted black, and the entire unit will be insulated. When we keep the solar cooker in sunlight it absorbs solar energy and heats up the surrounding air. This warm air circulates throughout the box and cannot escape. Because of this sometimes the inside temperature would reach more than 100 oC which is sufficient to cook our food. Photo courtesy flickr.com However Solar cooker takes longer times to cook food. This is the best example of a passive solar energy system In most parts of India where solar radiation is relatively abundant; thus, we can use solar box cooker to prepare food more sustainable way In India we have the largest solar steam cooking system. More importantly it is still working from the 90s in Brahmakumaris Ashram at Mount Abu in Rajasthan. They have 84 shining parabolic concentrators on the roofs; each one looking like a huge dish made of reflecting concave mirrors. The sunlight from the concentrators heats up the receiver and converts water into steam. This system can cook for more than 38000 people. The next example of Passive use of solar energy is daylighting Today many buildings are designed to take advantage of natural solar energy for daylighting. Daylighting is simply the use of natural sunlight to light up a building’s interior. The south side of a building mostly receives the highest sunlight Therefore buildings are designed south facing for passive solar daylighting. Usually, the building is designed with large south-facing windows. This kind of design will allow the entry of maximum sunlight into the building’s interior. Passive solar systems are maintenance-free. There are no operating costs. We can substantially reduce the electric bills. There is no need for devices such as external pumps fans or electricity. The only major problem is passive solar heating or passive solar lighting systems depend on the climate. In a cloudy and dark climate, it will not operate. Photo courtesy flickr.com The second method of solar energy application is Active solar energy utilization Active solar energy utilization means capturing and storing of solar energy for future use. In active solar heating systems solar energy will be used to heat up fluid or air and then the fluid is moved with the help of external pumps to the storage system and then the captured heat will be transferred directly for later use. Usually, active solar heating and solar cooling systems require solar collectors which are usually mounted on roofs. Such systems also require pumps and motors to move the heated fluids to the storage system in order to deliver the captured heat. Solar water heaters are the best example of active solar energy utilization. Typical solar water heaters consist of two parts one is solar collector and the second one is storage tank. First, we can discuss about Solar Collectors. A typical water heater is composed of solar flat plate collectors. Solar radiation is absorbed by the collector and converts the incident solar radiation into thermal energy by absorbing heat. The heat gathered is transferred to the storage unit. The solar collectors are usually placed on the roof of the building facing south and at an inclination of 30-60 degrees with respect to the horizontal plane. Solar collectors are classified into two categories. The first one is Non concentrating collectors and the second one is Concentrating collectors. Let me explain what Non concentrating collectors is Non concentrating collectors means the area that intercepts the sunlight is the same as the area absorbing the solar energy Flat-plate collectors are the most common example of non-concentrating collectors which are used widely for water heating. These collectors are simply metal boxes that have a transparent glass cover on top of a dark or black-colored absorber plate The rest of the faces of the box are insulated to prevent heat losses. These boxes consist of copper pipes running in parallel. The fluid typically water flows through these copper pipes. Solar radiation passes through the transparent glass material and absorbs the radiation from the sun. The circulating water inside copper pipes heats up and transfers the heat to water in a storage vessel. This can be used for domestic purposes as a water heater or heating the water in the swimming pools in warm climates. Next, I will explain about Concentrating Collectors In Concentrating collectors, the area intercepting solar radiation is greater than the absorber area. Solar Furnace and Solar thermal power plants use concentrating solar collector systems. A solar furnace is an optical system that uses concentrated solar power to produce high temperatures. The solar furnace technique is based on reflecting solar radiation from Parabolic mirrors or heliostats and concentrating it onto a focal point. The largest solar furnace was installed at Mont-Louis in France. it has been operational since 1970. Nearly 20000 mirrors were used to concentrate sunlight to create more than 3500 °C Temperature at the focal point of this solar furnace Photo courtesy flickr.com Next example for active solar energy utilization is Solar energy to produce electricity Solar energy is used to generate electricity. Solar collectors in sunny deserts can produce high-temperature heat which drives a heat engine nothing but a steam turbine which is connected to an electrical power generator for producing electricity. The advanced computer-connected solar collectors usually move by tracking the sun to maintain a high degree of concentration on a central heat collection unit and transform solar energy received from the sun into high-temperature heat energy which can be used to convert heat energy into electricity. Next, we can see Solar energy for cooling applications The principle behind the solar cooling or solar refrigeration is like conventional refrigeration. But the difference is Solar thermal energy is used instead of electrical power to operate a heat engine. The heat engine compresses a special vapor into a liquid refrigerant. The re-evaporation of this liquid refrigerant absorbs the heat out of the surroundings and in turn cools its surroundings. Final topic I want to discuss is Solar cells or photovoltaic technology Modern solar power systems use photovoltaic cells to collect solar energy. “Photo” means “produced by light” and “voltaic” is “electricity produced by a chemical reaction.” Simply the process of converting photons into electricity. A single PV device is commonly called as a solar cell. The photovoltaic cell contains a semiconductor most commonly silicon with a small number of impurities such as boron or phosphorus. Recently PV cells are made up of cadmium telluride or copper indium gallium diselenide. Arsenic and antimony have also been used in solar cells. New photovoltaic technologies are coming up such as solar cells made up of organic materials or quantum dots or made up of hybrid organic-inorganic materials perov- skites materials such as calcium titanate. A typical solar cell contains a very thin semiconductor and is often less than the thickness of human hairs. Photo courtesy https://commons.wikimedia.org/ Photo courtesy rawpixel.com Each cell is connected by a circuit and designed into modules or panels. Several panels can be connected to form arrays. One or more arrays are then connected to the electrical grid. When sunlight falls on the silicon layer it causes electrons to eject. And these ejected electrons move quickly into the circuit and generate electricity. Commercial or domestic PV panels produce an average current from 10 watts to 300 watts in a direct current. PV panels require an inverter to change the DC electricity into AC current in order to be compatible with electrical devices and the electric grid. PV panels can also be used to create large-scale power plants. Bhadla Solar Park is the world’s largest solar park which is located in Rajasthan India. It is spread over a total area of 14000 acres and generates 2250 Mega Watts of electricity PV cells can be used to power space satellites Solar cells can be used. to provide electricity to remote villages street lighting applications. in the desalination of salt water and water pumping and so on. PV cells are used Powering remote telecommunication devices and railway signals. Also powering of smaller items such as calculators and watches.  Environmental hazard: definition; Types, causes and solutions, biological hazards (COVID-19) Environmental hazard An environmental hazard is a substance, state or event which has the potential to threaten the surrounding natural environment or adversely affect people's health, including pollution and natural disasters such as storms and earthquakes. It can include any single or combination of toxic chemical, biological, or physical agents in the environment, resulting from human activities or natural processes, that may impact the health of exposed subjects, including pollutants such as heavy metals, pesticides, biological contaminants, toxic waste, industrial and home chemicals. Hazards can be categorized in three types: Chemical Biological Nuclear This section deals with biological hazards, its causes, ways of encountering them and preventive measures that we can undertake for avoid or minimize the hazards. With this regard, we need to identify the hazard and assess the environment for the presence of hazards. This step is called environmental hazard identification. Environmental hazard identification is the first step in risk assessment, which is the process of assessing the likelihood, or risk, of adverse effects resulting from a given hazard. Risk In simplest of terms, risk is the possibility of something bad happening. Risk is the uncertainty about the occurrence of a certain event such as injury, disease, death, economic loss, or damage. It is usually expressed as a mathematical statement about the likelihood of the occurrence of the event, or in other words, it is expressed in terms of mathematical probabilities. Biological hazards Biological hazards, also known as biohazards, refer to biological substances that pose a threat to the health of living organisms, primarily that of humans. This can include medical waste or samples of a microorganism, viruses, or toxins (from a biological source) that can affect human health. Biological health hazards include bacteria, viruses, parasites and moulds or fungi. They can pose a threat to human health when they are inhaled, eaten or come in contact with skin. They can cause illness such as food poisoning, tetanus, respiratory infections or parasite infection. 1  Image showing A) Bacteria, B) Mold/yeast, and C) Viruses The main source of biological hazards is due to diseases caused by various factors. These diseases can be classified into transmissible and non-transmissible diseases. Non-transmissible diseases (NCD) A non-communicable disease (NCD) is a disease that is not transmissible directly from one person to another. NCDs include Parkinson's disease, autoimmune diseases, strokes, most heart diseases, most cancers, diabetes, chronic kidney disease, osteoarthritis, osteoporosis, Alzheimer's disease, cataracts, and others. NCDs may be chronic or acute. Most are non- infectious, although there are some non-communicable infectious diseases, such as parasitic diseases in which the parasite's life cycle does not include direct host-to-host transmission. NCDs are the leading cause of death globally. In 2012, they caused 68% of all deaths (38 million) up from 60% in 2000. Transmissible/Communicable diseases Communicable diseases, also known as infectious diseases or transmissible diseases, are illnesses that result from the infection, presence and growth of pathogenic (capable of causing disease) biologic agents in an individual human or other animal host. These diseases spread from one person to another through a variety of ways that include: contact with blood and bodily fluids; breathing in an airborne virus; or by being bitten by an insect. Some examples of the reportable communicable diseases include Hepatitis A, B & C, influenza, measles, and salmonella, tuberculosis, COVID-19, Ebola and several others. 2 Certain communicable diseases can spread at different rates and to varying geographical locations, resulting in either an endemic, epidemic or a pandemic disease. Endemic disease An endemic disease is consistently present but limited to a particular region. This makes the disease spread and rates predictable. Malaria, for example, is considered endemic in certain countries and regions. Epidemic disease An epidemic is the rapid spread of disease to a large number of patients among a given population within an area in a short period of time. Yellow fever, smallpox, measles, and polio are prime examples of epidemics. An epidemic disease doesn't necessarily have to be contagious. Pandemic disease A pandemic is an epidemic of an infectious disease that has spread across a large region, for instance multiple continents or worldwide, affecting a substantial number of individuals. Recent pandemics include tuberculosis, Russian flu, Spanish flu, Asian flu, cholera, Hong Kong flu, HIV/AIDS, and COVID-19. COVID-19 Coronavirus disease (COVID-19) is an infectious disease caused by the SARS-CoV-2 virus. The first known case was identified in Wuhan, China, in December 2019. The disease quickly spread worldwide, resulting in the COVID-19 pandemic. Symptoms Symptoms of COVID‑19 are variable, but often include fever, cough, headache, fatigue, breathing difficulties, loss of smell, and loss of taste. Symptoms may begin one to fourteen days after exposure to the virus. At least a third of people who are infected do not develop noticeable symptoms. Of those people who develop symptoms noticeable enough to be classed as patients, most (81%) develop mild to moderate symptoms (up to mild pneumonia), while 14% develop severe symptoms (dyspnea, hypoxia, or more than 50% lung involvement on imaging), and 5% develop critical symptoms (respiratory failure, shock, or multiorgan dysfunction). Older people are at a higher risk of developing severe symptoms. Some people continue to experience a range of effects (long COVID) for months after recovery, and damage to organs has been observed. 3 Transmission COVID-19 is mainly transmitted when people breathe in air contaminated by droplets/aerosols and small airborne particles containing the virus. Infectious particles range in size from aerosols that remain suspended in the air for long periods of time to larger droplets that remain airborne briefly or fall to the ground. Infected people exhale those particles as they breathe, talk, cough, sneeze, or sing. Transmission is more likely the more physically close people are. However, infection can occur over longer distances, particularly indoors. SARS-CoV-2 Variants As of December 2021, there are five dominant variants of SARS-CoV-2 spreading among global populations: 4  Alpha variant (B.1.1.7, formerly called the UK variant) Beta variant (B.1.351, formerly called the South Africa variant) Gamma variant (P.1, formerly called the Brazil variant) Delta variant (B.1.617.2, formerly called the India variant) Omicron variant (B.1.1.529) Treatment Most people who become sick with COVID-19 will only have mild illness and can get better at home. Symptoms might last a few days. People who have the virus might feel better in about a week. Several treatment options are available to people with coronavirus (COVID-19) who are at the highest risk of becoming seriously ill. The treatments available are: Nirmatrelvir And Ritonavir (Paxlovid) Sotrovimab (Xevudy) Remdesivir (Veklury) Molnupiravir (Lagevrio) Vaccines for COVID-19 A COVID‑19 vaccine is a vaccine intended to provide acquired immunity against severe acute respiratory syndrome coronavirus 2 (SARS‑CoV‑2), the virus that causes coronavirus disease 2019 (COVID‑19). Mass vaccination programmes have been established by WHO, and nine vaccines have been approved for emergency or full use by at least one stringent regulatory authority recognized by the World Health Organization (WHO): Pfizer–BioNTech, Oxford–AstraZeneca, Sinopharm BIBP, Moderna, Janssen, CoronaVac, Covaxin, Novavax, and Convidecia. Each of these vaccines causes the immune system to create antibodies for fight COVID-19 using a harmless version of a spike-like structure on the surface of the COVID-19 virus. These vaccines act by different mechanisms, a few of which are explained below. The different types of vaccines include: Viral vector vaccines mRNA vaccines Whole virus vaccines Protein sub-unit vaccines Viral vector vaccine In this type of vaccine, genetic material from the COVID-19 virus is placed in a modified version of a different virus (viral vector). When the viral vector gets into your cells, it delivers genetic material from the COVID-19 virus that gives your cells instructions to make copies of the S protein. Once your cells display the S proteins on their surfaces, your immune system responds by creating antibodies and defensive white blood cells. If you later become infected with the COVID-19 virus, the antibodies will fight the virus. The Janssen/Johnson & Johnson COVID-19 vaccine is a vector vaccine. AstraZeneca and Covaxin vaccines work on this principle. 5  Schematic representation for the mechanism of action of the viral vector vaccine of COVID-19 mRNA vaccines This type of vaccine uses genetically engineered mRNA to give your cells instructions for how to make the S protein found on the surface of the COVID-19 virus. After vaccination, your muscle cells begin making the S protein pieces and displaying them on cell surfaces. This causes your body to create antibodies. If you later become infected with the COVID-19 virus, these antibodies will fight the virus. Both the Pfizer-BioNTech and the Moderna COVID-19 vaccines use mRNA. Schematic representation for the mechanism of action of mRNA vaccine of COVID-19 Whole virus vaccines 6 Whole virus vaccines use a weakened (attenuated) or deactivated form of the pathogen that causes a disease to trigger protective immunity to it. the advantages of an inactivated whole virus vaccine include the fact its technology is well established, it is suitable for people with compromised immune systems, and it’s relatively simple to manufacture. Schematic representation for the mechanism of action of the whole virus vaccine of COVID-19 Protein subunit vaccine Subunit vaccines include only the parts of a virus that best stimulate your immune system. This type of COVID-19 vaccine contains harmless S proteins. Once your immune system recognizes the S proteins, it creates antibodies and defensive white blood cells. If you later become infected with the COVID-19 virus, the antibodies will fight the virus. Novavax is working on a protein subunit COVID-19 vaccine. Covishield is one such vaccine prepared according to this method. Schematic representation for the mechanism of action of the protein subunit vaccine of COVID- 19 7  Chemical Hazards: Bisphenol-A, Mercury Chemical hazard A chemical hazard is any non-biological substance that has the potential to cause harm to life or health. It can include any single or combination of toxic chemical, biological, or physical agents in the environment, resulting from human activities or natural processes, that may impact the health of exposed subjects. This can include pollutants such as heavy metals, pesticides, biological contaminants, toxic waste, industrial and home chemicals. Chemical hazards and toxic substances pose a wide range of health hazards (such as irritation, sensitization, and carcinogenicity) and physical hazards (such as flammability, corrosion, and explosibility). In this section, we will look at bisphenol A and problems associated with its poisoning in the human body. We will also look at contamination due to heavy metals, specifically mercury. Bisphenol A Bisphenol A (BPA) is a chemical compound primarily used in the manufacturing of various plastics. It is a colourless solid which is soluble in most common organic solvents but has very poor solubility in water. BPA's largest single application is as a co- monomer in the production of polycarbonates, which accounts for 65-70% of all BPA production. The manufacturing of epoxy resins and vinyl ester resins account for 25-30% of BPA use. Products containing Bisphenol A BPA is found in polycarbonate plastics and epoxy resins. Polycarbonate plastics are often used in containers that store food and beverages, such as water bottles. Epoxy resins are used to coat the inside of metal products, such as food cans, bottle tops and water supply lines. Common products that may contain BPA include: Items packaged in plastic containers Baby bottles Canned foods Toiletries Menstrual products Thermal printer receipts CDs and DVDs Household electronics Eyeglass lenses Sports equipment Dental filling sealants Mechanism of action of BPA in the human body 1 BPA binds to both nuclear estrogen receptors (ERs), ERα and ERβ, activating them. It can mimic as well as antagonize estrogen, indicating that it is a selective estrogen receptor modulator (SERM) or partial agonist. It also acts as an antagonist of the androgen receptor (AR) at high concentrations. Schematic representation of the mechanism of action of BPA in the human body Health problems associated with BPA BPA has been linked to causing reproductive, immunity, and neurological problems, as well as an increased likelihood of Alzheimer’s, childhood asthma, metabolic disease, type 2 diabetes, and cardiovascular disease. Several neurological health issues have been observed during pregnancy and development, like reduced lung capacity, wheezing and asthma after birth, leading to ban in the use of BPA in baby bottles. Studies have linked BPA and obesity; BPA exposure modifies insulin sensitivity and insulin release without affecting weight. Other endocrine-related disorders include infertility, polycystic ovarian syndrome (PCOS) and precocious puberty. BPA also disrupts thyroid function, binding to thyroid hormone receptor, and studies have linked BPA with increased TSH (Thyroid stimulating hormone). BPA exposure can lead to prostate cancer in men. 2  Summary of some health problems associated with BPA poisoning in the human body Sources of BPA contamination BPA can get in our body through eating or drinking foods heated in plastics; eating or drinking foods stored in metal cans (canned foods) or plastics (take-out containers); and touching cash register receipts. The major points of entry of bisphenol A into our body are summarized below. Major human exposure to BPA is diet, via ingestion of contaminated food and water. Plastics leach BPA when cleaned with harsh detergents, or when they contain acidic or high-temperature liquids. BPA-based resin coatings in older water pipes can leach BPA. Several uses of BPA in digital media, electrical and electronic equipment, sports safety equipment, electrical laminates in printed circuit boards, composites, paints and adhesives can also lead to exposure. Bioaccumulation in water bodies, aquatic plants and organisms can result in toxicity. BPA is also found in high concentrations in thermal and carbonless copy paper, used for printing receipts, airline tickets etc., and can be absorbed into body through skin. Environmental effects of BPA Even though BPA has a short half-life (4.5 days in soil and water, < 1 day in air), its ubiquity makes it an important pollutant. It has a low rate of evaporation from water and soil, which creates problems despite its biodegradability. It interferes with nitrogen fixation at the roots of certain leguminous plants. BPA affects growth, reproduction and development in aquatic organisms, especially fish, with endocrine-related effects observed in fish and other aquatic 3 invertebrates, amphibians and reptiles. It also impacts reproduction in terrestrial animals and insects, impairing development and inducing genetic aberrations. Steps to limit BPA contamination Heavy metal poisoning Heavy metal poisoning refers to when excessive exposure to a heavy metal affects the normal function of the body. Examples of heavy metals that can cause toxicity include lead, mercury, arsenic, cadmium, and chromium. Exposure may occur through the diet, from medications, from the environment, or in the course of work or play. Heavy metals can enter the body through the skin, or by inhalation or ingestion. Toxicity can result from sudden, severe exposure, or from chronic exposure over time. Mercury Mercury is a heavy metal belonging to the transition element series in the periodic table. It exists in nature in three forms: elemental, organic and inorganic, each with its own profile of toxicity. It is a liquid at room temperature; it has high vapour pressure and is released into the environment as mercury vapour. Its most commonly occurring oxidation states are +1 +2. Methylmercury is the most frequently encountered organic compound found in the environment, formed as a result of methylation of inorganic mercuric forms of mercury by microorganisms found in soil and water. Mercury in the Environment Mercury is a widespread environmental toxicant and pollutant, inducing severe alterations in the body and a wide range of adverse health effects. It is ubiquitous in the environment, therefore, making it difficult for plants, animals and humans alike to avoid exposure. 4  Schematic representation of the different forms of mercury in the environment. [Source: https://webcam.srs.fs.fed.us/impacts/mercury/index.shtml] Uses of Mercury Electrical industry (switches, thermostats, batteries) Dental fillings Industrial processes (production of caustic soda) Nuclear reactors Anti-fungal agents for wood processing Solvent for reactive and precious metals Sources of Mercury Poisoning Major sources of exposure to mercury are through accidents, environmental pollution, food contamination, dental care, preventive medical practices, industrial and agricultural operations such as non-ferrous metal production, cement production etc. Major sources of chronic low level mercury exposure are through dental amalgams (50% elemental mercury) and fish consumption. Mercury exposure can also occur by inhaling contaminated air, and improper use/disposal of mercury-containing objects after spills or disposal of fluorescent lamps. Human activities that can result in Mercury release into environment: burning of coal (half of atm. mercury) and gold mining. 5  Mercury enters water either through Earth’s crust or through industrial pollution, which are methylated by algae and bacteria in the water, which then bioaccumulates in fish, and eventually into humans. Two most highly absorbed species: Hg(0) and methyl mercury. Mechanism of Mercury in the Human Body Elemental mercury vapour is highly lipophilic and effectively absorbed through lungs and tissues lining the mouth. After mercury enters the blood, it rapidly passes through cell membranes, including both the blood-brain-barrier (BBB) and placental barrier (PB). Within the cell, it is oxidized to its highly reactive +2 state. Methyl mercury, from fish, is readily absorbed in the gastrointestinal tract because of its lipid solubility, and can cross the BBB and PB. Once absorbed, mercury has a very low excretion rate, accumulating in kidneys, neurological tissues and liver, resulting in gastrointestinal toxicity, neuro and nephrotoxicity. Adverse Health Effects of Mercury Brain is the target organ for mercury, but it can also impair any organ leading to malfunctioning of nerves, kidney and muscles. Mechanism: mercury binds to free thiol groups (cysteine residues). Symptoms depend on the type, dose and duration of exposure, including peripheral neuropathy, skin discolouration (pink), swelling and desquamation (shedding or peeling of skin). Mercury is neurotoxic, responsible for microtubule destruction, mitochondrial damage, lipid peroxidation etc. High-levels of exposure to mercury: Minamata disease. Symptoms: acrodynia (pink disease) skin becomes pink and peels, kidney problems, decreased intelligence. Treatment and Prevention Mercury poisoning can be reduced by eliminating/reducing exposure to mercury and related compounds. Powdered sulfur may be applied in case of a spill, resulting in a solid compound that can be easily disposed off of. Treatment First step is decontamination, disposal of clothes, washing skin with soap and water, flushing eyes with saline as needed. Chelation therapy with DMSA and other sulfur-based compounds are effective for inorganic mercury poisoning. DMSA can be used against severe mercury poisoning. 6  Air Pollution Air Pollution Air pollution is contamination of the indoor or outdoor environment by any chemical, physical or biological agent that modifies the natural characteristics of the atmosphere. Household combustion devices, motor vehicles, industrial facilities and forest fires are common sources of air pollution. Pollutants of major public health concern include particulate matter, carbon monoxide, ozone, nitrogen dioxide and sulfur dioxide. Outdoor and indoor air pollution cause respiratory and other diseases and are important sources of morbidity and mortality. Sources of Air Pollution The sources of air pollution can be broadly classified into natural and anthropogenic. The natural sources include volcano, forest fire and pollens, organic compounds from plants, sea salt, suspended soils and dusts, etc. The anthropogenic sources include everything involving human activities such as: Anthropogenic sources of air pollution: 1) Burning of fossil fuels and motor vehicle exhausts: These can include gases emitted by the burning of fossil fuels and vehicle exhausts. This means that road traffic is one of the biggest sources of air pollution. Vehicles emit nitrogen oxides, carbon dioxide, carbon monoxide and particulate matter. Trains pollute a lot less than cars. But they also cause pollution, since they utilize a large amount of electricity produced by power stations, which produces large quantities of nitrogen oxides, carbon dioxides, sulfur dioxides and particulate matter. These pollutants may be categorised as primary or secondary pollutants. 2) Agriculture: Animals like cows and sheep release a massive amount of methane through belching and breaking wind. Methane is a colourless gas which is produced in their stomachs when bacteria break down the food that they eat. Across the whole world, livestock is the biggest source of methane. Methane is the second most important greenhouse gas which can cause climate change. 3) Waste disposal: Waste disposal from landfills is the largest producer of methane emitted after agriculture and livestock rearing. 1 Primary Pollutants Primary pollutants are directly emitted to the atmosphere, Air pollutants may have a natural, anthropogenic or mixed origin, depending on their sources or the sources of their precursors. Key primary air pollutants include particulate matter (PM), black carbon (BC), sulphur oxides (SO2), nitrogen oxides (NOX) (including nitrogen monoxide and nitrogen dioxide, NO2), ammonia (NH3), carbon monoxide (CO), methane (CH4), non-methane volatile organic compounds (NMVOCs), including benzene, and certain metals and polycyclic aromatic hydrocarbons, including benzo[a]pyrenes (BaP). Secondary Pollutants Secondary pollutants are formed in the atmosphere from precursor gases through chemical reactions and microphysical processes. Key secondary air pollutants are PM, ozone (O3), NO2 and several oxidised volatile organic compounds (VOCs). Key precursor gases for secondary PM are sulphur dioxide (SO2), NOX, NH3 and VOCs. These pollutants and their precursor gases can be of both natural and anthropogenic origin including: Burning of fossil fuels in electricity generation, transport, industry and households Industrial processes and solvent use, for example in the chemical and mining industries; Agriculture Waste treatment Natural sources, including volcanic eruptions, windblown dust, sea-salt spray and emissions of volatile organic compounds from plants Types of Air Pollutants The following pollutants form the major category of air pollutants. Carbon monoxide (CO): 2 Carbon monoxide (CO) is a colorless, odorless, and highly toxic gas that forms during the incomplete combustion of carbon-containing materials. Major sources are motor vehicle exhaust, burning of forests and grasslands, smokestacks of fossil fuel–burning power plants and industries, tobacco smoke, and open fires and inefficient stoves used for cooking. Carbon monoxide can combine with hemoglobin in red blood cells, which prevents the normal binding of oxygen with hemoglobin molecules. This in turn reduces the ability of blood to transport oxygen to body cells and tissues. Long-term exposure can trigger heart attacks and aggravate lung diseases such as asthma and emphysema. At high levels, CO can cause headache, nausea, drowsiness, confusion, collapse, coma, and death. Carbon dioxide: Carbon dioxide (CO2) is a colorless, odorless gas. About 93% of the CO2 in the atmosphere is the result of the natural carbon cycle. The rest comes from human activities, mostly the burning of fossil fuels and the clearing of CO2-absorbing forests and grasslands. CO2 is being added to the atmosphere faster than it is removed by the natural carbon cycle. This can contribute to human health problems such as heat exhaustion and to the reduction of food supplies in some areas, while causing water shortages, prolonged drought, or excessive flooding in other areas. Nitrogen oxides: Nitrogen oxides are emitted during fuel combustion from industrial facilities and the road transport sector. NOX is a group of gases comprising nitrogen monoxide (NO) and nitrogen dioxide (NO2). NO makes up the majority of NOX emissions. NOX contributes to the formation of ozone and particulate matter. Sulfur dioxide: Sulphur dioxide is formed and emitted by combustion of fossil fuels (mainly coal and oil) primarily for electricity generation. High concentrations of SO2 are associated with multiple health and environmental effects. The highest concentrations of SO2 have been recorded in the vicinity of large industrial facilities. SO2 emissions are an important environmental issue because they are a major precursor to ambient PM2.5 Ground-level ozone: Ground level ozone is created when sunlight reacts with, volatile organic compounds (VOCs) and nitrous oxides (NOx). When particles in the air combine with ozone, they create smog. Smog is a type of air pollution that looks like smoky fog and makes it difficult to see. These can be transported long distances by wind. Photochemical smog: Photochemical smog also results from interactions between different air pollutants. This smog has a brown haze and can be painful to the eyes, accounting for most of the smog we see today. Photochemical smog forms from interactions between particulates, nitrogen oxides, ozone, and other air pollutants, though primarily from VOCs and NOx since ozone comprises a large portion of this smog. 3 Suspended Particulate Matter (SPM): Particulate matter is a mixture of aerosol particles (solid and liquid) covering a wide range of sizes and chemical compositions. PM is either directly emitted as primary particles or it forms in the atmosphere from emissions of certain precursor pollutants such as SO2, NOx, NH3. SPM is emitted from many anthropogenic sources, including both combustion and non-combustion sources. Natural emissions of PM also occur, including from sea salt and windblown Saharan dust. Volatile Organic Compounds (VOCs) Volatile organic compounds (VOCs) are emitted as gases from certain solids or liquids. VOCs include a variety of chemicals, some of which may have short- and long-term adverse health effects. Management of Air Pollution Air pollution management aims at the elimination or reduction to acceptable levels, of airborne gaseous pollutants, suspended particulate matter and physical and, to a certain extent, biological agents whose presence in the atmosphere can cause adverse effects on human health, deleterious effects on animal or plant life, damage to materials of economic value to society and damage to the environment Health Effects of Air Pollution Our body has a number of natural defence mechanisms to help protect us against air pollution. But prolonged or acute exposure to air pollutants, including tobacco smoke can overload or break down these natural defenses. Years of smoking or breathing polluted air can lead to other lung ailments such as chronic bronchitis and emphysema, which leads to acute shortness of breath and usually to death. Inhalation of small, fine and ultra-fine particles added to the atmosphere by coal-burning power plants causes asthma attacks and other respiratory disorders. Steps to Reduce Air Pollution The best air quality management methods stress that the air pollutant emissions should be kept to a minimum. Some of the methods that can be used to reduce or minimize air pollution are: 4  Enforcement of the use of catalytic converters in vehicles or of emission standards in incinerators Shut-down of factories or reduction of traffic during unfavourable weather conditions Strict laws for emission of pollutants, which emphasize prevention of emission Stricter laws need to be enforced on coal-burning power plants and industrial facilities so that the harmful emissions of sulfur dioxides and nitrogen oxides can be controlled Use of air pollution control devices such as chemical scrubbers in emission towers that can capture most of the harmful chemicals that might be emitted in industries. E.g., SO 2 can be removed by use of a lime scrubber Control devices such as inertial separators for particular matter and wet collectors Safe disposal methods to reduce the effects of the harmful agents Tax each unit of pollutant produced We, as individuals can take a few steps to reduce consumption of energy and air pollution. They are summarized as follows. 1. Walk, bike or use public transportation to reduce air pollution 2. Minimize pollution from cars by prevention of idling 3. Save energy and make sure you use energy efficiently 4. Recycle and reuse 5. Consume less and choose sustainable products 6. Avoid/minimize plastic bags 7. Reduction of forest fires and smoking 8. Use of fans instead of Air conditioners 9. Use filters for chimneys 10. Avoid usage of crackers 11. Avoid using of products with chemicals 12. Implement Afforestation 5  Water Pollution Water Pollution Water pollution is the contamination of water sources by substances which make the water unusable for drinking, cooking, cleaning, swimming, and other activities. Pollutants include chemicals, trash, bacteria, and parasites. All forms of pollution eventually make their way to water. Water bodies include lakes, rivers, oceans, aquifers, reservoirs and groundwater. Water pollution results when contaminants are introduced into these water bodies. Water pollution can be attributed to one of four sources: sewage discharges, industrial activities, agricultural activities, and urban runoff including stormwater. Sources of Water Pollution Sources of water pollution are either point sources or non-point sources. 1) Point Sources Point sources have one identifiable cause, such as a storm drain, a wastewater treatment plant or an oil spill. Because point sources are located at specific places, they are fairly easy to identify, monitor, and regulate. 2) Non-point Sources Nonpoint sources are broad and diffuse areas, rather than points, from which pollutants enter bodies of surface water or air. Examples include runoff of chemicals and sediments from cropland, livestock feedlots, logged forests, urban streets, parking lots, lawns, and golf courses. Types of Water Pollution 1) Ground-water Pollution Groundwater gets polluted when contaminants— from pesticides and fertilizers to waste leached from landfills and septic systems—make their way into an aquifer, rendering it unsafe for human use. Ridding groundwater of contaminants can be difficult to impossible, as well as costly. Once polluted, an aquifer may be unusable for decades, or even thousands of years. Groundwater can also spread contamination far from the original polluting source as it seeps into streams, lakes, and oceans. Common sources of ground water pollution include septic tanks, industries like textile, chemical and tanneries, deep well injections, mining, etc. 1 2) Surface-water Pollution Covering about 70 percent of the earth, surface water constitutes our oceans, lakes, rivers, streams, etc. Major sources of surface water pollution are: 1. Sewage: emptying drains and sewers 2. Industrial effluents: industrial waste containing toxic chemicals, acids, alkalis, salts and radioactive waste 3. Synthetic detergents: in washing and cleaning 4. Agrochemicals: fertilizers, insecticides and pesticides 5. Oil: spillage into sea during drilling and shipment 6. Waste heat: from industrial discharges increases water temperature and affects the distribution and survival of sensitive species Types of Contaminants Water pollutants can be classified as organic pollutants, inorganic pollutants, pathogens, suspended solids, nutrients and agriculture pollutants, thermal, radioactive, and other pollutants. Organic and inorganic pollutants are mainly discharged from industrial effluents and sewage into the water bodies. 1) Organic Contaminants The following are the types of organic contaminants that are responsible for water pollution Detergents Food processing waste: fats, grease, oxygen demanding substances Insecticides and herbicides: organohalides Petroleum hydrocarbons: fuels, lubricants and fuel combustion products Volatile organic compounds: industrial solvents Chlorinated solvents (PCBs, trichloroethylene) Drug pollution Personal hygiene and cosmetic products 2) Nitrogen and Phosphorus Compounds Addition of compounds containing nitrogen and phosphorus helps in the growth of algae and other plants that consume DO after death. Foul smelling gases are produced under anaerobic conditions. Excess growth or decomposition of plant material changes CO2 concentrations, thereby affecting water pH. These changes in DO, oxygen and temperature change the physicochemical properties of water. 3) Inorganic Compounds The following inorganic contaminants are responsible for water pollution. They are Acidity caused by industrial discharge (SO2) Ammonia from food processing waste 2  Chemical waste Fertilizers containing nutrients (nitrates and phosphates) Heavy metals from moto vehicles and acid mine drainage Silt/sediment 4) Pathogens Wastewater sewage contain several pathogenic and non-pathogenic microorganisms and viruses that can cause water-borne diseases such as cholera, dysentery, typhoid, jaundice etc. Coliform bacteria do not cause an actual disease, but is used as a bacterial indicator of water pollution. High levels of pathogens may result from on-site sanitation systems (septic tanks, pit latrines) or inadequately treated sewage discharges. Combined sewers in certain cities discharge untreated sewage during rain storms that can result in contamination. Pathogen discharge can also be caused by poorly managed livestock operations. 5) Macroscopic Pollution They are large, visible items polluting water, also called floatables or marine debris found in open seas, including Trash/garbage: discarded by people, or washed by rainfall into storm drains and eventually reaching surface waters Nurdles: small ubiquitous waterborne plastic pellets Shipwrecks: large, derelict ships 6) Thermal Pollution Thermal pollution, sometimes called "thermal enrichment", is the degradation of water quality by any process that changes ambient water temperature. A common cause of thermal pollution is the use of water as a coolant by power plants and industrial manufacturers. Thermal pollution can also be caused by the release of very cold water from the base of reservoirs into warmer rivers. Fish and other organisms adapted to particular temperature range can be killed by an abrupt change in water temperature (either a rapid increase or decrease) known as "thermal shock". 7) Radioactive Substances Radioactive waste is any pollution that emits radiation beyond what is naturally released by the environment. It’s generated by uranium mining, nuclear power plants, and the production and testing of military weapons, as well as by universities and hospitals that use radioactive materials for research and medicine. Radioactive waste can persist in the environment for thousands of years, making disposal a major challenge. 3 Effects of Water Pollution Increase of oxygen demand: Demand of O2 increases with addition of biodegradable organic matter, expressed as biological oxygen demand (BOD) Diseases: In humans, drinking or consuming polluted water in any way has many disastrous effects on our health. It causes typhoid, cholera, hepatitis and various other diseases. Destruction of Ecosystems: Ecosystems are extremely dynamic and respond to even small changes in the environment. Water pollution can cause an entire ecosystem to collapse if left unchecked. Biomagnification: Non-biodegradable waste biomagnifies, causing toxic effects at various levels of the food chain. Several chemicals such as DDT are not water soluble, and tend to accumulate in body lipids, building up at successive levels of the food chain. Eutrophication: Chemicals in a water body, encourage the growth of algae. These algae form a layer on top of the pond or lake. Bacteria feed on these algae and this decreases the amount of oxygen in the water body, severely affecting the aquatic life there. Effects the food chain: Disruption in food chains happens when toxins and pollutants in the water are consumed by aquatic animals (fish, shellfish etc) which are then consumed by humans. Control of Water Pollution The best way to protect streams from pollution is to prevent it at the source. The following are some of the methods that can be implemented to control water pollution. Judicious use of pesticides and fertilizers Use of nitrogen-fixing plants Prevent manure run-off into surface water, instead divert them into basins for settlement that can be used later as fertilizer Separate drainage of sewage and rain water to prevent overflow and contamination Planting trees would reduce pollution by preventing runoff 4  Treatment of wastewater is essential to prevent pollution from point sources Parameters considered for water quality: BOD, chemical oxygen demand (COD), nitrates, phosphates, oil and grease, toxic metals Waste water should be treated properly by primary and secondary methods to reduce BOD, COD levels up to permissible levels for discharge 5  Soil Pollution Soil Pollution Soil contamination, soil pollution, or land pollution as a part of land degradation is caused by the presence of xenobiotic (human-made) chemicals or other alteration in the natural soil environment. It is typically caused by industrial activity, agricultural chemicals or improper disposal of waste. Contamination is correlated with the degree of industrialization and intensity of chemical substance. The concern over soil contamination stems primarily from health