Pollution and Society

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.

Air Pollutants

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.

CH₄+OH=H₂O+CH₃ CH₄+O=OH+CH₃











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, SO_3, 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).

These secondary pollutants, ozone ( O_3, ) 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.