Pollution in our world effects two essential aspects of our planet: air and water. Although their pollutants are emitted in completely different ways, they both harm living organisms. Air pollution is predominately emitted though the exhaust of motor vehicles and the combustion of fossil fuels, whereas water pollution is the result of industrial waste and environmental accidents. Our society knows that pollution is harmful and a serious problem for Earth but generally people don?t care. Nevertheless everybody needs to contribute to prevention and pay attention to government control in the amount of material large industries can emit into the air and/or water. Industry gives off a good share of the waste that is polluting our planet, but it?s every person is contributes as well. Government involvement is key to regulating toxins, building waste systems and protecting air and waters.
The earth?s atmosphere is composed primarily of nitrogen, oxygen, argon and carbon dioxide (the major components) as well as neon, krypton, helium and methane (the most predominate of the minor components) it is these gases which make up the 5.6*1015 ton “shell” that surrounds our planet. However, humans, animals and vegetation in the Unites States alone emit 264 million tons of substances into the atmosphere each year. On a worldwide scale that turns out to be approximately 6.6 billion tons. These substances, which aren?t naturally part of the atmosphere, are called pollutants. Over ninety percent of all air pollutants can be divided up into five categories: carbon monoxide, nitrogen oxides, hydrocarbons, sulfur oxides and suspended particulate matter. Mass is only one way of categorizing pollutants. Substances can also be looked at from an effect stand point. For example, carbon monoxide (CO) comprises 56% of all air pollutants when looked at in terms of total mass. However, when looked at in terms of effect, CO makes up only 2.5% of the pollutants. In contrast, hydrocarbons make up 13% of all pollutants when look at in terms of mass but that number jumps to 71.5% when looked at from an effect point of view.Carbon Monoxide (CO) is a colorless, odorless, tasteless gas and is the most abundant and widely distributed air pollutant. Even though vast quantities of carbon monoxide enter the atmosphere each year (147 million tons in the US alone) the majority of the emissions are due to natural causes instead of anthropogenic, human causes. It is because of this that carbon monoxide is viewed as the least danger to living beings. The largest natural cause of CO is the oxidation of methane in the atmosphere. Methane, CH4, is produced on the surface of earth by the decay of organic matter. It then rises into the atmosphere in a gaseous state, and oxidizes to form methyl radicals (CH3) which react further to ultimately produce CO.
The category of Nitrogen Oxides is made up primarily of three different gases; nitrogen dioxide (NO2 ), nitrous oxide ( N2O), and nitric oxide, NO. Nitrous oxide is over four times more toxic than nitric oxide. Nitrogen dioxide is generally not considered a pollutant because it is not toxic and usually not produced by humans. On the basis of mass, the nitrogen oxides make up the smallest group of pollutants and have the second smallest effect on life, behind CO. As with carbon monoxide, nature emits greater amounts of these gases than humans do. The leading natural causes include the decomposition of soil, bacterial activity and lightning. Anthropogenic emissions are mostly due to the combustion of fuel. Natural air is composed of 78% nitrogen and 21% oxygen, which don?t react at normal temperatures, but can react if the temperature is hot enough (1300-2500° C). In these cases, the quantity of nitrogen oxides released varies depending on the temperature and the ratio of nitrogen to oxygen. The increasing use of nitrogenous fertilizers is among the reasons that emissions of N2O have been on the rise. Damage to plants by N2O has only been observed near nitric acid facilities and no evidence of NO damage has ever been seen outside the laboratory. It was concluded that the level of concentration of these gases is too low to cause significant problems at this time.
The category of Sulfur Oxides mostly consists of sulfur dioxide, SO2. Sulfur trioxide, SO3, does exist but it doesn?t stay in our atmosphere. Sulfur trioxide is very reactant with moisture (H2O) and forms sulfuric acid, H2SO4, one of the substances in acid rain. Unlike the two prior groups, the sulfur oxides are predominately emitted by humans. However, a fair amount of SO2 is produced in the atmosphere. Hydrogen Sulfide, H2S, is produced by the decay of organic matter, and then rises to the atmosphere where it oxidizes and forms sulfur dioxide. Around 80% of the sulfur oxides emitted by humans are due to the combustion of coal. Coal, which is formed from once-living organisms, contains some sulfur. When this combusts (fire results when a substance reacts with oxygen) sulfur oxides are formed. Although sulfur is an element necessary for life, too much or too little sulfur can harm organisms. The effect of sulfur oxides on plants varies with time of exposure and concentration. In general, too much exposure, either a short time with a high concentration or a long time with a low concentration, results in damage to the leaves. Unlike the two prior categories, the present level of sulfur oxides actually effects humans, generally through the respiratory system. In most cases the amount inhaled is not enough to give any serious results besides coughing, but if vast quantities are inhaled into the lungs it is possible to get a respiratory infection.
Hydrocarbons are the second largest category of air pollutants by mass, but they are by far the largest group of pollutants when considering their effect. There are thousands of different hydrocarbon compounds that are comprised solely of hydrogen and carbon. They can be found in a gaseous, liquid or solid states at room temperature. Most hydrocarbons are emitted by the bacterial decomposition of organic material. Methane, CH4, which was mentioned in the formation of carbon monoxide, is the simplest of the hydrocarbons. Petroleum is a complicated mixture of several simple hydrocarbons showing again transportation by motor vehicles is the leading cause of this category being emitted into the air. Their evaporation during the refining of petroleum is also important. Unlike the previous categories, the hydrocarbons are relatively harmless in their released state. It is in the atmosphere that they undergo chemical reactions and become hazardous. With this change the primary pollutants (substances within the five original categories) become secondary pollutants (new resultant substances).
O+ O2=O3 
These secondary pollutants, ozone ( O3, ) and peroxyacetyl nitrate ( PAN ), are known to cause damage to plants, especially citrus trees, salad crops and coniferous trees. However, even though hydrocarbons are extremely dangerous to plants, studies have revealed no direct effects on humans at the current level of concentration. As a matter of fact, the concentration would have to be a hundred to a thousand times larger in order to see any direct effects.
The final category of pollutants is the suspended particulate matter, or particulates for short. Unlike the other four categories particulates are not gases, they are small solid or liquid particles such as smoke, mist, or dust that measure between .0002m m to 5000m m (m m being a micrometer or one millionth, 10-6 meters). Particulates are formed in two ways, the clumping together of microscopic fragments or the breaking up of larger particles. Nature emits particulates in a variety of ways. Similar to hydrocarbons, various gases react in the atmosphere and form particulates. Blowing dust can be categorized as particulates, but the largest natural cause of particles is the bursting of tiny air bubbles at the surface of the ocean that results in the release of microscopic salt particles into the air. Unlike the previous categories, humans emit minimal quantities of particulates by transportation; fires, incomplete combustion of fossil fuels, and industrial breaking of stone, give off most human released particulates. Few studies have been conducted to see the effect of particulates on plants, but it has been found that when dust settles on their leaves sunlight is partially blocked, thus preventing growth of the plant. The effect on humans is entirely in the respiratory system. Small particles (those less than 5m m) can get by the defenses of the upper respiratory system and reach the lungs; the smaller the particle, the deeper into the lungs it can get and the more problems it can cause, because they become increasingly difficult for the body to remove.
Several different kinds of waste are oxygen consumers. There is a certain concentration of oxygen needed in the world?s oceans to support life. However, when waste is present in the water that is easily broken down by the presence of oxygen, and this lowers the oxygen levels necessary to sustain the “natural biota” for that water. Radioactive materials escape from ore processing, nuclear power plants and use of nuclear weapons. Just as radioactivity has harmful effects on humans these effects translate to aquatic life and invade water supplies around the world if not properly contained.
Oil is made up of crude petroleum and refined petroleum products such as gasoline. Crude petroleum is made up of an integral mix of compounds of hydrocarbons and
refined petroleum, the actual effective pollutant, is a simpler mix of “fewer components.” Table 11.1 gives an example of the structural make-up of hydrocarbons. Oil pollution results from normal tanker operations, offshore oil productions, oil waste in sewage systems and spills. Oils spills are the most public of mass water pollution (i.e. Exxon Valdez) and have both long and short-term effects on regional waters. 25% of spilled oil evaporates in the first days after the spill and through several other processes. Emulsification is the distribution of a liquid into another liquid. There are two main emulsification processes that can happen in the water and two consequences for living organisms. In oil pollution there is oil-in-water and water-in-oil. The former is stabilized throughout the chemical action between the water and oil, not only at the surface but throughout the body of water as well. It can sink to the bottom, which involves the sediments of the sediments in the ocean floor. Water-in-oil is more commonly seen in “flushing” which is a spread on the surface and what is most commonly seen lying on the surface of the water after a spill. Oil is also picked up by aquatic organisms and other aquatic life. Oxidation occurs as oil is a oxygen consuming waste and is quickly photo oxidized by microorganism providing the strongest source of degradation. Oxygen up-take in needy organisms is thus slowed down in this way.
Toxic metals are made up of heavy metals, light metals, and trace metals. Heavy metals have five times the density of water, whereas light metals have less. . Heavy metals are made up of seven basic elements that are found frequently in the Earth in aquatic and terrestrial environments. Trace metals display natural compounds of metal. The latter carry more contaminants than the heavy metals because of their great effects on living organisms. As Figure 12.5 shows, metals in certain quantities are needed. Some trace metals, although involved in the soil and water cycle, have small concentrations and it is when the concentrations are too high that they contaminate and pollute water. They are transmitted through direct use of mining in ores, in the burning of fossil fuels. The trace elements end up in water systems through atmospheric rain, agricultural run-off, mining wastes and domestic sewage. One the key factors of metal pollution is that they cannot biologically or chemically breakdown in nature. This stability also lets them be carried long distances through air and water. Mercury has shown to be a good example of how contamination of trace metals has severe effects and will be discussed in the next section on effects on society.
Synthetic organic pesticides are compounds that include insecticides, fungicides, and other pests that inhibit human conduct. There are chlorophenoxy acids, organophosphates, carbamates and chlorinated hydrocarbons. Discussing chlorinated hydrocarbons, the most dominant of these pollutants, is necessary because of their persistence or staying power. They resist breakdown for approximately two years before they disappear. Because of the great length of time that is these hydrocarbons can invade areas of the environment they were not meant for and spread into soils, runoffs and water environments. Their toxic effects on living organisms pervade fatty membranes around nerves and disrupt the movement of ions between the fiber.
Dichlorodiphenyltrichloroethane (DDT) is the most infamous compound used to explain their effects as severe water pollutants. Its history of success as a pesticide and sharp decline in use because of previously unknown pollution pushed synthetic organic pesticides onto the public stage. DDT was used to destroy insect carriers of malaria, yellow fever, and typhus among other diseases. And for all its success in halting disease causing agents its use was not monitored closely and it became a major water pollutant. It got into water areas through aerial sprays on land or in flight; it was carried in the atmosphere in rain and was in runoffs from soil. As an acting pollutant it was soluble in body tissues (fats and oils) in organism and it affected reproductive systems in organisms such as birds and fish. Birds such as the bald eagle and brown pelican had total reproductive failure. Fish experienced high mortality rates with it being directly toxic to some species.