Look At This
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Air pollution is a general term that covers a broad range of contaminants in the atmosphere. Pollution can occur from natural
causes or from human activities. Discussions about the effects of air pollution have focused mainly on human health but
attention is being directed to environmental quality and amenity as well. Air pollutants are found as gases or particles, and on a
restricted scale they can be trapped inside buildings as indoor air pollutants. Urban air pollution has long been an important
concern for civic administrators, but increasingly, air pollution has become an international problem.
The most characteristic sources of air pollution have always been combustion processes. Here the most obvious pollutant is
smoke. However, the widespread use of fossil fuels has made sulfur and nitrogen oxides pollutants of great concern. With
increasing use of petroleum-based fuels, a range of organic compounds have become widespread in the atmosphere.
In urban areas, air pollution has been a matter of concern since historical times. Indeed, there were complaints about smoke in
ancient Rome. The use of coal throughout the centuries has caused cities to be very smoky places. Along with smoke, large
concentrations of sulfur dioxide were produced. It was this mixture of smoke and sulfur dioxide that typified the foggy streets of
Victorian London, paced by such figures as Sherlock Holmes and Jack the Ripper, whose images remain linked with smoke and
fog. Such situations are far less common in the cities of North America and Europe today. However, until recently, they have been
evident in other cities, such as Ankara, Turkey, and Shanghai, China, that rely heavily on coal.
Coal is still burned in large quantities to produce electricity or to refine metals, but these processes are frequently undertaken
outside cities. Within urban areas, fuel use has shifted toward liquid and gaseous hydrocarbons (petroleum and natural gas).
These fuels typically have a lower concentration of sulfur, so the presence of sulfur dioxide has declined in many urban areas.
However, the widespread use of liquid fuels in automobiles has meant increased production of carbon monoxide, nitrogen
oxides, and volatile organic compounds.
Primary pollutants such as sulfur dioxide or smoke are the direct emission products of the combustion process. Today, many of
the key pollutants in the urban atmospheres are secondary pollutants, produced by processes initiated through photochemical
reactions. The Los Angeles, California-type, photochemical smog is now characteristic of urban atmospheres dominated by
secondary pollutants.
Although the automobile is the main source of air pollution in contemporary cities, there are other equally significant sources.
Stationary sources are still important and the oil-burning furnaces that have replaced the older coal-burning ones are still
responsible for a range of gaseous emissions and fly ash. Incineration is also an important source of complex combustion
products, especially where this incineration burns a wide range of refuse. These emissions can include chlorinated
hydrocarbons such as dioxin. When plastics, which often contain chlorine, are incinerated, hydrochloric acid is found in the waste
gas stream. Metals, especially since they are volatile at high temperatures, can migrate to smaller, respirable particles. The
accumulation of toxic metals, such as cadmium, on fly ash gives rise to concern over harmful effects from incinerator emissions.
In specialized incinerators designed to destroy toxic compounds such as polychlorinated biphenyls (PCBs), many questions
have been raised about the completeness of this destruction process. Even under optimum conditions when the furnace
operation has been properly maintained, great care needs to be taken to control leaks and losses during transfer operations
(fugitive emissions).
The enormous range of compounds used in modern manufacturing processes has also meant that there is an ever-widening
range of emissions from both the industrial processes and the combustion of their wastes. Although the amounts of these toxic
compounds are often rather small, they add to the complex range of compounds found in the urban atmosphere. Again, it is not
only the deliberate loss of effluents through discharge from pipes and chimneys that needs attention. Fugitive emissions of
volatile substances that leak from valves and seals often warrant careful control.
Air pollution control procedures are increasingly an important part of civic administration, although their goals are far from easy to
achieve. It is also noticeable that although many urban concentrations of primary pollutants, for example, smoke and sulfur
dioxide, are on the decline in developed countries, this is not always true in developing countries. Here the desire for rapid
industrial growth has often lowered urban air quality. Secondary air pollutants are generally proving a more difficult problem to
eliminate than primary pollutants like smoke.
AIR POLLUTION AND HEALTH PROBLEMS
Urban air pollutants have a wide range of effects, with health problems being the most enduring concern. In the classical polluted
atmospheres filled with smoke and sulfur dioxide, a range of bronchial diseases was enhanced. While respiratory diseases are
still the principal problem, the issues are somewhat more subtle in atmospheres where the air pollutants are not so obvious. In
photo-chemical smog, eye irritation from a secondary pollutant, peroxyacetyl nitrate (PAN), is one of the most characteristic direct
effects of the smog. High concentrations of carbon monoxide in cities where automobiles operate at high density mean that the
human heart has to work harder to make up for the oxygen displaced from the blood's hemoglobin by carbon monoxide. This
extra stress appears to reveal itself through increased incidence of complaints among people with heart problems. There is a
widespread belief that contemporary air pollutants are involved in the increases in asthma, but the links between asthma and air
pollution are probably rather complex and related to a whole range of factors. Lead, from automotive exhausts, is thought by many
to be a factor in lowering the IQs of urban children.
Air pollution also affects materials in the urban environment. Soiling has long been regarded as a problem, originally the result of
the smoke from wood or coal fires, but now increasingly the result of fine black soot from diesel exhausts. The acid gases,
particularly sulfur dioxide, increase the rate of destruction of building materials. This is most noticeable with calcareous stones,
which are the predominant building material of many important historic structures. Metals also suffer from atmospheric acidity. In
today's photochemical smog, natural rubbers crack and deteriorate rapidly.
Health problems relating to indoor air pollution are extremely ancient. Anthracosis, or black lung disease, has been found in
mummified lung tissue. Recent decades have witnessed a shift from the predominance of concern about outdoor air pollution
into a widening interest in indoor air quality.
The production of energy from combustion and the release of solvents is so large in the contemporary world that it causes air
pollution problems of regional and global nature. Acid rain is now widely observed throughout the world. The sheer quantity of
carbon dioxide emitted in combustion processes is increasing the concentration of carbon dioxide in the atmosphere and
enhancing the greenhouse effect.
Solvents, such as carbon tetrachloride and the aerosol propellants chlorofluorocarbons (CFCs) are now detectable all over the
globe and responsible for problems such as ozone layer depletion.
At the other end of the scale, we need to remember that gases leak indoors from the polluted outdoor environment, but more
often the serious pollutants arise from processes that take place indoors. Here there has been particular concern with regards to
the generation of nitrogen oxides by sources such as gas stoves. Similarly, formaldehyde from insulating foams causes
illnesses and adds to concerns about our exposure to a substance that may induce cancer in the long run. In the last decade it
has become clear that radon leaks from the ground can expose some members of the public to high levels of this radioactive gas
within their own homes. Cancers may also result from the emanation of solvents from consumer products—glues, paints, and
mineral fibers (asbestos). More generally these compounds and a range of biological materials—animal hair, skin, pollen
spores, and dusts—can cause allergic reactions in some people. At one end of the spectrum these simply cause annoyance, but
in extreme cases, such as found with the bacterium Legionella, a large number of deaths can occur.
There are also important issues surrounding the effects of indoor air pollutants on materials. Many industries, especially the
electronics industry, must take great care over the purity of indoor air where a speck of dust can destroy a microchip or low
concentrations of air pollutants change the composition of surface films in component design. Museums must care for objects
over long periods of time, so precautions must be taken to protect delicate dyes from the effects of photochemical smog, paper
and books from sulfur dioxide, and metals from sulfide gases.
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What Do you Know About Air Pollution
Air pollution is a general term that covers a broad range of contaminants in the atmosphere. Pollution can
occur from natural causes or from human activities. Discussions about the effects of air pollution have
focused mainly on human health but attention is being directed to environmental quality and amenity as
well. Air pollutants are found as gases or particles, and on a restricted scale they can be trapped inside
buildings as indoor air pollutants. Urban air pollution has long been an important concern for civic
administrators, but increasingly, air pollution has become an international problem.
The most characteristic sources of air pollution have always been combustion processes. Here the most
obvious pollutant is smoke. However, the widespread use of fossil fuels has made sulfur and nitrogen
oxides pollutants of great concern. With increasing use of petroleum-based fuels, a range of organic
compounds have become widespread in the atmosphere.
In urban areas, air pollution has been a matter of concern since historical times. Indeed, there were
complaints about smoke in ancient Rome. The use of coal throughout the centuries has caused cities to
be very smoky places. Along with smoke, large concentrations of sulfur dioxide were produced. It was this
mixture of smoke and sulfur dioxide that typified the foggy streets of Victorian London, paced by such
figures as Sherlock Holmes and Jack the Ripper, whose images remain linked with smoke and fog. Such
situations are far less common in the cities of North America and Europe today. However, until recently,
they have been evident in other cities, such as Ankara, Turkey, and Shanghai, China, that rely heavily on
coal.
Coal is still burned in large quantities to produce electricity or to refine metals, but these processes are
frequently undertaken outside cities. Within urban areas, fuel use has shifted toward liquid and gaseous
hydrocarbons (petroleum and natural gas). These fuels typically have a lower concentration of sulfur, so the
presence of sulfur dioxide has declined in many urban areas. However, the widespread use of liquid fuels
in automobiles has meant increased production of carbon monoxide, nitrogen oxides, and volatile organic
compounds.
Primary pollutants such as sulfur dioxide or smoke are the direct emission products of the combustion
process. Today, many of the key pollutants in the urban atmospheres are secondary pollutants, produced
by processes initiated through photochemical reactions. The Los Angeles, California-type, photochemical
smog is now characteristic of urban atmospheres dominated by secondary pollutants.
Although the automobile is the main source of air pollution in contemporary cities, there are other equally
significant sources. Stationary sources are still important and the oil-burning furnaces that have replaced
the older coal-burning ones are still responsible for a range of gaseous emissions and fly ash. Incineration
is also an important source of complex combustion products, especially where this incineration burns a
wide range of refuse. These emissions can include chlorinated hydrocarbons such as dioxin. When
plastics, which often contain chlorine, are incinerated, hydrochloric acid is found in the waste gas stream.
Metals, especially since they are volatile at high temperatures, can migrate to smaller, respirable particles.
The accumulation of toxic metals, such as cadmium, on fly ash gives rise to concern over harmful effects
from incinerator emissions. In specialized incinerators designed to destroy toxic compounds such as
polychlorinated biphenyls (PCBs), many questions have been raised about the completeness of this
destruction process. Even under optimum conditions when the furnace operation has been properly
maintained, great care needs to be taken to control leaks and losses during transfer operations (fugitive
emissions).
The enormous range of compounds used in modern manufacturing processes has also meant that there is
an ever-widening range of emissions from both the industrial processes and the combustion of their
wastes. Although the amounts of these toxic compounds are often rather small, they add to the complex
range of compounds found in the urban atmosphere. Again, it is not only the deliberate loss of effluents
through discharge from pipes and chimneys that needs attention. Fugitive emissions of volatile
substances that leak from valves and seals often warrant careful control.
Air pollution control procedures are increasingly an important part of civic administration, although their
goals are far from easy to achieve. It is also noticeable that although many urban concentrations of primary
pollutants, for example, smoke and sulfur dioxide, are on the decline in developed countries, this is not
always true in developing countries. Here the desire for rapid industrial growth has often lowered urban air
quality. Secondary air pollutants are generally proving a more difficult problem to eliminate than primary
pollutants like smoke.
AIR POLLUTION AND HEALTH PROBLEMS
Urban air pollutants have a wide range of effects, with health problems being the most enduring concern.
In the classical polluted atmospheres filled with smoke and sulfur dioxide, a range of bronchial diseases
was enhanced. While respiratory diseases are still the principal problem, the issues are somewhat more
subtle in atmospheres where the air pollutants are not so obvious. In photo-chemical smog, eye irritation
from a secondary pollutant, peroxyacetyl nitrate (PAN), is one of the most characteristic direct effects of
the smog. High concentrations of carbon monoxide in cities where automobiles operate at high density
mean that the human heart has to work harder to make up for the oxygen displaced from the blood's
hemoglobin by carbon monoxide. This extra stress appears to reveal itself through increased incidence of
complaints among people with heart problems. There is a widespread belief that contemporary air
pollutants are involved in the increases in asthma, but the links between asthma and air pollution are
probably rather complex and related to a whole range of factors. Lead, from automotive exhausts, is
thought by many to be a factor in lowering the IQs of urban children.
Air pollution also affects materials in the urban environment. Soiling has long been regarded as a
problem, originally the result of the smoke from wood or coal fires, but now increasingly the result of fine
black soot from diesel exhausts. The acid gases, particularly sulfur dioxide, increase the rate of
destruction of building materials. This is most noticeable with calcareous stones, which are the
predominant building material of many important historic structures. Metals also suffer from atmospheric
acidity. In today's photochemical smog, natural rubbers crack and deteriorate rapidly.
Health problems relating to indoor air pollution are extremely ancient. Anthracosis, or black lung disease,
has been found in mummified lung tissue. Recent decades have witnessed a shift from the predominance
of concern about outdoor air pollution into a widening interest in indoor air quality.
The production of energy from combustion and the release of solvents is so large in the contemporary
world that it causes air pollution problems of regional and global nature. Acid rain is now widely observed
throughout the world. The sheer quantity of carbon dioxide emitted in combustion processes is increasing
the concentration of carbon dioxide in the atmosphere and enhancing the greenhouse effect.
Solvents, such as carbon tetrachloride and the aerosol propellants chlorofluorocarbons (CFCs) are now
detectable all over the globe and responsible for problems such as ozone layer depletion.
At the other end of the scale, we need to remember that gases leak indoors from the polluted outdoor
environment, but more often the serious pollutants arise from processes that take place indoors. Here
there has been particular concern with regards to the generation of nitrogen oxides by sources such as
gas stoves. Similarly, formaldehyde from insulating foams causes illnesses and adds to concerns about
our exposure to a substance that may induce cancer in the long run. In the last decade it has become clear
that radon leaks from the ground can expose some members of the public to high levels of this radioactive
gas within their own homes. Cancers may also result from the emanation of solvents from consumer
products—glues, paints, and mineral fibers (asbestos). More generally these compounds and a range of
biological materials—animal hair, skin, pollen spores, and dusts—can cause allergic reactions in some
people. At one end of the spectrum these simply cause annoyance, but in extreme cases, such as found
with the bacterium Legionella, a large number of deaths can occur.
There are also important issues surrounding the effects of indoor air pollutants on materials. Many
industries, especially the electronics industry, must take great care over the purity of indoor air where a
speck of dust can destroy a microchip or low concentrations of air pollutants change the composition of
surface films in component design. Museums must care for objects over long periods of time, so
precautions must be taken to protect delicate dyes from the effects of photochemical smog, paper and
books from sulfur dioxide, and metals from sulfide gases.
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