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.
A smaller natural cause is the growth and decay of chlorophyll which is the green pigment in the leaves of plants. Eighty percent of the carbon monoxide that is emitted by humans is by transportation (mostly by gasoline powered vehicles). Because automobiles are the largest source of CO pollution, the highest concentration of this gas is in highly populated/urban areas. The next greatest anthropogenic source is agricultural burning, which accounts for another twelve percent. It has been shown that exposure to high concentrations of carbon monoxide can harm living organisms, but the current concentration in our atmosphere is still low enough so that plants and humans are both at minimal risk.
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.
People are mostly oblivious to the effects of air pollution. They know it’s out there and it is a problem but excepting skin cancer, there have been very few deaths with a direct link to air pollution. It is probably because of this that people aren’t as concerned with air pollution as they should be. Air pollution has always been around, and has actually been on a decline since the 1960’s (when coal was the major source of energy.) It is relatively easy to decrease the amount of pollutants we emit (each year new laws arise that crack down on the amount of certain substances that can be released into the air) but the harm has already been done, and next to impossible to fix. The ozone layer is the part of the atmosphere that keeps ultraviolet rays from penetrating humans and plants. But because of all the air pollution, various chemicals are slowly destroying the ozone layer. Each year the concentration of the ozone decreases by approximately two percent and the ozone layer over the South Pole is already fifty percent of its natural concentration. Ozone depleters (the majority of which are chlorofluorocarbons or CFC’s) react with ultraviolet radiation and break down into their component atoms, especially chlorine, bromine and fluoride. These component atoms then go on to steal an oxygen atom from the ozone layer (opposite to the reaction which forms O3), thereby destroying the ozone layer. This loss of protection from UV rays can result in an increase of human skin cancer, damage to various parts of the eyes as well as causing a breakdown of the immune system. With health being such a major issue in our society today, people have become scared by this "outbreak" of cancer. People know that the ozone layer is slowing depleting and that there is a health risk involved with being in the sun for extended periods of time. But very few people know that there is a connection between this breakdown of the ozone layer and air pollution. Instead of trying to control pollution emissions they just cut back on their time outdoors, or wear more sunscreen. Ultraviolet rays can also cause major environmental problems. These rays enter the atmosphere and can kill small aquatic organisms, such as plankton. When these small life forms decompose they release carbon dioxide, CO2, another gas which can cause the ozone layer to break down, thus resulting in a continuos cycle.
Another danger of air pollutants is before they get high enough in the atmosphere to break down the ozone layer, they are the leading cause of the greenhouse effect. These chemicals reflect some of the earth’s heat back down to earth, raising the surface temperature. The rise in temperature is known as the greenhouse effect. If this rise in temperature continues it could start to melt the polar icebergs, which would result in the oceans rising and in turn flooded coastal areas. This is one of the few effects of pollution that our society is actively worried about. The subject of the greenhouse effect is highly publicized and therefore people know about the risks concerning this topic. Even though people know about the greenhouse effect, they fai,lonce again, to see the why behind this event. People believe that the greenhouse effect is due to the ozone layer breaking down and in turn more ultraviolet rays enter our atmosphere which is the reason the temperature is increasing. Although this belief isn’t entirely accurate it is close enough for our purposes. As in the case with the problems of the ozone layer, society fails to see that this is all a result of air pollution.
Although air pollution
has relatively few immediate effects on humans at the present time it is
important that we try to reduce the amount of pollutants we emit into the
air. As discussed before the biggest cause of air pollution is use of
transportation, followed by the combustion of fossil fuels. In the past
thirty years many new standards have been passed in the United States which
resulted in a dramatic reduction in the gases emitted by automobiles (such
as the Clean Air Act of 1979). But even with these new laws air pollution
is still on the increase. It is mostly due to the fact that there are more
automobiles on the road today. Cars may be more efficient but there are
too many of them, which in many ways dimishes their efficiency. One solution
to this problem is encouraging people to carpool which would reduce the
number of cars on the road and in turn reduce the amount of pollutants.
Another solution is to make more laws enforcing more efficient cars. However
this would cost car manufactures more money, resulting in more expensive
cars which people wouldn’t want to buy. So the best solution to reducing
the amount of pollutants emitted by automobiles is by encouraging people
to carpool.
The combustion of fossil fuels is the other leading cause of air pollution. Although the amount of pollutants these factories emit has reduced since the 1950’s (when coal was the primary source of energy) they still release a large quantity of dangerous gases. More standards can be enforced to reduce the emissions of these factories. Nevertheless, as long as we rely on fossil fuels for energy these factories will have to emit some sort of gas. At the moment, nuclear energy appears to be the wave of the future and this type of energy releases a lot less pollutants into the air than the combustion of oil and coal. Although air pollution presents no immediate danger it is important that we try to control the pollutants we emit. Most of the harm has already been done and there are no known ways to fix these problems. It is for this reason that we try our best to help the situation as most as possible.
Unlike air pollution where the leading emission factors are natural, water pollution is mostly caused by human involvement. There have been many ways scientists have looked at the human effect on water systems. There are main areas of polluting substances that cause disruption or change in the chemical make up of the world’s waters, and effect the aquatic environment. Several areas overlap with one another. Some basic pollutants include, oxygen using wastes, radioactive material, sediments and inorganic chemicals. Other well-documented water pollutants include oil (i.e. tanker spills), synthetic organic compounds (i.e. pesticides) and toxic metals (i.e. mercury).
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.
Society’s main concern with water pollution has mostly
been realized through our own concern for their drinking water. Contaminants
of all kind have been studied for their possible harm on humans, and subsequent
discoveries led to seeing the effects on other life in water. Water as
a carrier of pathogenic organisms that can put health at risk was the primary
reason for pollution control. More recently pollution was personalized
when Americans saw pictures of seals and other sea life drowning in oil
slick from spills, with drastic consequences. Water birds can often be
so covered in oil slick that they can no longer fly and feathers lose their
insulation properties in cool water temperatures. Many surrounding plant
life on the shoreline are also coated and vegetation rates decrease. Photosynthesis
of plants is also affected below the water, where light intensity is decreased
by 90%, two meters below the surface because of oil "flushing". Long-term
affects, although still being studied, are based on the chemical messaging
that is adversely effected by oil compounds in the water. Similarly they
also might be involved and enter in the marine food chain. These facts
helped increase awareness, inform the public and change policy on oil tanker
practices.
In this same manner, DDT, decades after its discoverer
Paul Mueller won the Nobel Prize for chemistry because of its insecticidal
properties, was shown causing severe damage in water life systems. Nevertheless
an abundance of pesticides of all kinds are still used in many areas and
often are hard to contain in specific areas. As for metals, Mercury has
wrought the largest scare to humans as its toxic effects from our actions
have had repercussions. Mercury is used is three major ways by human processing
electrical apparatus, chlor-alkali industry, and paint. Humans are exposed
to mercury through production of other elements, the burning of coal, and
the accelerated weathering of rocks and soils. Although there are different
compounds of mercury effecting different aspects of body processes, there
are also central breakdowns. Toxic action occurs through the binding of
sulfur molecules in enzymes and cell walls that inhibit normal activity
and depending on amount paralyzes or kills. All damage in permanent. Humans'
greatest risk is through food poisoning. This was shown in the "Minamata
disease" where 44 people died and more were paralyzed because of eating
contaminated shellfish and other fish. Because of the biological amplification
of mercury in aquatic life and in humans, the methyl mercury wastes from
a shoreline plastics factory increased the mercury amount in the fish in
great amounts.
Water main purposes for human beings are for recreation and aesthetics, public water supply, aquatic life, agriculture, and industry. Any substance that prevents these normal uses of water can be seen as a pollutant. Because of this great lengths need to be taken to protect and restore our Earth’s water content.
In many respects pollution control is a Government Issue. In the United States the Clean Water Act in 1972 is now celebrating its 25th anniversary showing exactly what has been accomplished in pollution prevention and water restoration. Economically, clean water is important in the America’s tourism, agriculture, and commerce. (chart) The number of people helped by wastewater treatment plants has doubled by 750 million people. In fact, the Clinton administration has invested 10 billion dollars that will go to continuing the efforts of this act. US policy to help anti-pollution campaigns have been and continue to be successful because if financial capabilities of the country. Unfortunately the same efforts for sanitation and prevention is not seen equally around the world. Water- borne diseases regularly monitored in the US are rampant all over. The World Health Organization would argues that globally one billion people still lack safe drinking water and more than two billion do not have adequate disposal facilities. Basic sanitation is lacking in many developing countries which causes not only a health risk, but an increasingly polluted environment.
The WHO is on the forefront of water policy. In May of 1997, the Assembly resolved to further study and assess twelve POP’s -persistant organic pollutants: PCB’s, dioxins, furans, aldrin, dieldrin, DDT, endrin, chlordane, HCB, mirex, toxaphene and heptachlor. All were found, by the International Program on Chemical Safety, to have comparable substitutes when used as pesticides. DDT although successful in destroying malaria, it still is not used properly in agriculture. Working with governments in the United Nations there has been a global effort to support government authorized programs for alternate means of pest control.
In the United States the Environmental Protection Agency has responded to the water quality problems by looking at the watersheds around the country. Impressing on local state regulators and citizens to pay attention to the pollution problems in their areas, they have classified all of the watersheds by 15 indicators that characterize conditions.
In this same manner they have put together a comprehensive program to decrease non-point source pollution on urban storm water run-off, mining, forestry and agriculture. All of these areas can effect the concentration of pollutants in our water systems.
Pollution is a problem in our society that we are just beginning to try and control properly. In the last century, people have just started to take notice of the serious effects that it can have. Taking steps towards cleaning areas up and changing methods of emitting possible toxic or heavy pollutants as wastes. Whether it is air pollution or water pollution it can be and is very dangerous to us, and other forms of life around us. Recycling is not the easy solution to the problem. Pollution prevention involves a lot more and now with the Internet, the public’s involvement and education in pollution is much easier. Cutting down on pollution is not a one mans job, it takes everybody to pitch in as well as the government to crack down on the larger industries. There are agencies working all over the world to clean up our air and water. . It is very easy to contribute and also extremely worthwhile for the continued health of our planet.
Important Terms:
Anthropogenic- caused by human.
Atmosphere- the gaseous layer surrounding the earth, primarily composed of 21% oxygen and 78% nitrogen.
Combustion- the rapid oxidation of a substance through fire.
Emulsification- the dispersion of droplets of one liquid in another.
Micrometer- one millionth of a meter, mm.
Pesticide- any chemical used for the killing of unwanted insects or plants.
Pollutant- a chemical, which can released by humans or by nature, which can have a negative effect on our planet.
Primary Pollutants- pollutants which have a direct effect on the earth they include; carbon monoxide, nitrogen oxides, hydrocarbons, sulfur oxides and suspended particulate matter
Radioactive material- a material that is capable of emitting alpha, beta or gamma rays.
Secondary Pollutants- pollutants which are formed from a reaction that involve one or more primary pollutants.
Ultraviolet rays- Rays emitted by the sun that have a very short wave length and can be harmful to living organisms if overexposed.
Waterborne diseases- Caused by the ingestion of water contaminated pathogenic bacteria or viruses.
Watershed- Drainage area or land areas bounded by ridges that catch excess water.
Bibliography:
Harrison, Roy M., ed. Pollution; Causes, Effects and Control. Cambridge: The Royal Society of Chemistry, 1990.
Hirschhorn, Joel S. and Kirsten U. Oldenburg. Prosperity Without Pollution. New York: Van Nostrand Reinhold, 1991.
Moriarty, F. Ecotoxicology; The Study of Pollutants in Ecosystems. New York: Academic Press, 1983.
Seager, Spencer L. and H. Stephen Stoker. Environmental Chemistry: Air and Water Pollution. Glenview: Scott, Foresman and Company, 1976.
Singer, S. Fred, ed. Global Effects of Environmental Pollution. New York: Springer-Verlag New York Inc, 1970.
