There has always been some form of air pollution – even before man arrived on the scene.  Naturally-occurring forest fires initiated by lightning or even volcanoes have been polluting the air for centuries.  However, since the arrival of humans – and more especially since the advent of industrialization – we have been the major source of air pollution.

As early as the turn of the century people were dying from air pollution of their own making.  In Glasgow, Scotland, in 1909 one thousand people died as a result of polluted air in that city (Owen et al. 445).  It has only gotten worse from that point.  In 1999 there was only one day in Beijing, China when the air reached the Level One rating.  On average 25% of the year the air rating is only Level Four or Level Five, where a person can become dizzy from the toxic atmosphere (Dorgan).
 
 

There are several types of pollutants emitted into the air.  One of them is carbon monoxide.  Surprisingly, most of this gas (93%) occurs  naturally from  places like  marshlands  as organisms decay.  Yet,  this source is  no real threat  as it  is so widely dispersed and is so quickly converted into carbon dioxide (Owen et al. 446).  Why should we be concerned about the 7% of carbon monoxide which we introduce into the air?  The problem is that this amount of gas is concentrated in small areas and does not disperse  effectively.   In many cities  the carbon  monoxide percentage is fifty times higher than the worldwide average.  It is these deadly concentrations that are harmful, both to us and to the other organisms with which we share this planet.

Nitric oxide is formed during combustion processes like those used in our vehicle engines.  In small concen- trations this gas is relatively harmless.  However, large concentrations can be deadly.  It combines with the hemoglobin in our systems and blocks its ability to transport oxygen effectively throughout our bodies.

When combined with atmospheric oxygen, nitric oxide produces nitrogen dioxide.  This is a major component of photochemical smog.  This gas causes problems ranging from internal bleeding to emphysema.  It is four times more toxic than nitric oxide.  Our vehicles account for 50% of this gas in the atmosphere.
 
 

Another form of pollution is particulate matter.  Particles are introduced  into the  air  by plants  and factories  during their operating processes.  Most  of this  pollution is caused by the burning of coal as fuel. Slash and burn agriculture, which is often practiced in less developed countries, is another contributor to this type of pollution (see Cultural Perspectives). The smaller the particle, the longer it remains suspended in the atmosphere.  These  pollutants have been shown to cause many respiratory problems and even heart malfunctions.  Some are known carci- nogens.  There are an estimated 60,000 deaths annually caused by this type of pollution (Owen et al. 447).  It is the elderly and people with asthma who are most at risk.

Whenever coal and oil are burned, oxides of sulfur are emitted into the air.  This gas also contributes to the respiratory ailments of our planet.  Yet, when combined with nitrogen dioxide, it is even more of a problem.  These two gases combine with water and oxygen to produce sulfuric acid and nitric acid.  These acids fall back to the earth in the form of precipitation, sometimes hundreds of miles away from the source of the pollution.  The rain in the highly industrialized northeastern United States is the most acidic of the whole country.  The disturbing aspect is that not only is this acidity rising, the area of coverage is also expanding (Owen et al. 478).  Of course, the United States is only one country with this problem.  Almost every area in the world downwind from a major industrial or population center has this problem.

What are the effects of this acid precipitation?  Acids erode manmade structures, especially monuments made of stone or marble.  Metallic structures are not exempt from this damage.  The monetary damage to buildings and materials in only seventeen states in the U. S. has been estimated to be over five billion dollars annually.  What would these numbers insinuate for global damage?

Acid precipitation causes a loss of nutrients in the soil due to displacement by hydrogen ions and inhibition of nitrogen-fixing bacteria.  Heavy metals, which are usually harmlessly bound to soil, are released and can be absorbed by the roots of plants.  In addition to harming the soil from which plants receive their nutrition, the acid can kill buds and stunt growth on already existing plants.

Thousands of lakes have been destroyed worldwide due to a buildup of acid.  The acidity levels are lethal for many species of fish, leading to a huge reduction in fish populations and possibly even outright extinction of some species.  Obviously, acid precipitation is a major problem for the planet.  Refer to the Environmental Protection Agency’s Acid Rain Program for more details.

Hydrocarbons are composed of hydrogen and carbon.  Examples of these are methane and benzene.  When hydrocarbons react with nitric oxide, they produce ozone.  The greater the sun’s strength, the more ozone which is produced.  Ozone is another major contributor to photochemical smog.  The peak hours when this smog is most powerful are between 12:00 and 4:00 in the afternoon.  This smog has become a serious problem in many highly-populated cities of the world.  This photochemical smog irritates the eyes, the nose, and throat, causing respiratory distress.  Of course, it is the weaker individuals which are most susceptible to these problems.  Once again, the major source of this pollutant is our vehicles.

Despite the fact that the Clean Air Act has been in place for many years in the U. S., in 1994 there were 77 cities that failed to meet the federal ozone standard.  Another side effect of ozone production is reduced crop yield.  There have been billions of dollars lost annually to decreases in crop production caused by air pollution.

During normal weather the warm air produced by our pollution rises and eventually disperses throughout the atmosphere.  However, sometimes a thermal inversion occurs.  When the atmospheric air is warmer than the air at ground level, there is no way for the polluted ground level air to rise and dissipate.  This causes the pollution to settle and remain in one spot for as long as the inversion lasts.  Sometimes this is only a few hours; other times a high pressure area can stall and cause the inversion to last for days.  This can be deadly.

In October of 1948 a thermal inversion occurred in Donora, Pennsylvania, near Pittsburgh.  The town is encircled by hills, trapping the pollution very effectively.  When the thermal inversion occurred, the people were literally choking in their own pollution.  Unfortunately, this inversion lasted for several days.  Over 40% of the citizens became ill with respiratory problems and severe headaches.  Before the inversion was gone, twenty people had died (Owen et al. 454).

In London in 1952 an even worse incident occurred.  A thermal inversion there (with its much greater population) caused 4,000 people to die.  It is fortunate that these events do not occur often.  However, the world’s population is rising dramatically; and the number of vehicles on the road is following suit.  We should expect that these types of occurrences will become more commonplace unless we do something to correct the problem.

One problem caused by air pollution is long-term illnesses.  There are many people with chronic bronchitis, emphysema, and lung cancer which were precipitated by air pollution.  In many ways these diseases are more troubling than outright death as they harm a person slowly over a period of many years, making his life increasingly more difficult.

Another result of air pollution is more subtle.  The increasing particles in the atmosphere allow less sunlight to penetrate through to the earth, thereby changing our seasons and the amount of light we receive. The gases we are introducing into the atmosphere also collect and cause the atmosphere to warm.  This trapping of heat is known as the “greenhouse effect”.  Carbon dioxide, methane, and other gases essentially produce a greenhouse around the earth.  These gases trap the heat coming off the earth’s surface.  Of the gases contributing to this process carbon dioxide is the most important.

Carbon dioxide is constantly removed from the atmosphere by green plants and algae during photosynthesis.  But it is also released back into the air when plants and animals respire, when organisms decay, or when any organic material is burned (such as in burning of forests, either accidentally or purposely).  Until recently this exchange has been in balance, with neither removal nor production being greater.  However, since 1860 scientists have discovered that the amount of carbon dioxide in the atmosphere has increased almost 25%.  Most of this increase can be contributed to human activities like burning of fossil fuels and the clearing of forests for development.  From 1957 to 1995 alone a 15% increase in carbon dioxide has been measured in Hawaii.  During this same time frame, global temperatures have also risen steadily.  Many animal species cannot adapt to this sudden fluctuation.  It is possible that many species will become extinct because of this stress.  See Greenhouse Effect.

It does not take a genius to realize that if these air pollutants are harming us so extensively they must also be causing damage to the organisms around us.  Plants especially are vulnerable because they are in such close proximity to us in comparison to wild animals.  As plants respire, they essentially “breathe” in the same poisons that we do.  If they are not killed outright, they are damaged and can have long-term problems like we do.

Refer to the Environmental Protection Agency website for details of the Clean Air Act and other environmental legislation.