Air Quality and Pollution
ZORAN MARMUT
Institute of Hygiene and Medical Ecology, Faculty
of Medicine, University of Belgrade, Belgrade, Serbia
zmarmut@eunet.yu
Definition
Air quality refers to the physical, chemical, and biological
characteristics of air, both in outside space and in
enclosed spaces, such as most industrial settings, other
non-industrialworking places, and residencies. Air pollution
is the abnormal presence of various substances
(gases, vapors or particles) in the air in sufficient concentrations
such that accumulated substances lead to
poor air quality and affect human health, living matter
and other materials. These substances may be released
into the air by natural processes or by human activities.
Basic Characteristics
Air is a mixture of gases, water vapor, solid and liquid
airborne particles in a wide range of concentrations that
range from essential for life to chemically inert. Some
of them are even hazardous, but are normally present
in low concentrations. Air is what constitutes Earth’s
atmosphere and it is present as an almost transparent,
thin envelope around our planet. The atmosphere significantly
determines the necessary conditions for various
forms of life on Earth, and also shapes and modifies
the subtle combination of environmental factors that we
call climate.
The normal chemical composition of dry air in the
troposphere is as follows: major gases are nitrogen
and oxygen (78,09% and 20,94%, respectively, by volume);
minor gases are argon (0,93%) and carbon dioxide
(0,03%); and trace gases (the whole group totaling
0,01%) are neon, helium, methane, krypton, hydrogen,
nitrogen oxides, ozone, ammonia, and sulfur dioxide.
Water vapor content in the low atmosphere is highly
variable, ranging from less than 1% to 5–6% by volume.
Air quality may range widely from quite good (satisfactory)
to poor, in various degrees. Air quality is good
when there is normal chemical composition of air without
significant variations in physical (or physico-chemical,
e. g. radiological) and biological characteristics.
Air quality is poor and detrimental if air is odorous
and stale, if physical parameters are out of optimal values,
or if air is polluted by chemicals of various origin.
The main physical characteristics of air that affect
air quality are temperature, humidity, air velocity, and
radiant heat. Biological origins of air quality deterioration
include bacteria, viruses (humans are the main
sources in indoor spaces), fungi (molds), insects (fleas
and cockroaches), arthropods (e. g. house dustmites),
mammals (e. g. home pets – their excreta, hair, dander
or feathers), and plants (pollen grains). There are two
main groups of sources of air pollution – natural, and
artificial or man-made sources.
Natural Sources of Air Pollution
Over the millennia it has been in existence, the atmosphere
has been relatively balanced and stable in composition,
being polluted mainly by natural processes.
Like now, natural sources of pollution have been volcanic
eruptions, forest wildfires, biochemical release of
pollutants from soils and oceans, soil erosion, windstorms,
lightning, and plant pollen release, etc. Natural
sources are much stronger than artificial ones, but pollutants
are usually diluted or widely dispersed over the
whole atmosphere, often far from human habitation.
Artificial Sources of Air Pollution
During the last 150–300 years, which have seen agricultural
and industrial revolutions, human technology
has reached a point where it is disturbing the global
balance of the atmosphere. Man has begun to pollute
air in a much stronger manner than ever before. Pollution
has been caused by an enormous output of harmful
substances into the atmosphere, emitted from a variety
of stationary or mobile sources. These artificial or
man-made sources are usually situated inside human
settlements or close to them; for this reason, they are
much more threatening to human health than natural
sources. The most important sources of pollution are:
a) power and heat generation objects (e. g. fossil fuel
power stations, domestic combustion appliances, and
biomass burning); b) industrial objects (smelteries and
foundries) and agricultural activities; c) transportation
(motor vehicles with internal combustion); d) waste
sites (the burning or spontaneous evaporation of pollutants
out of dumps); and e) Other human activities producing
gases, vapors or aerosols (fumigation, spraying,
etc.).
Ambient or Outdoor Air Pollution
Major pollutants are slightly different throughout the
world, depending on the predominance of pollution
sources locally. However, the six major types are the
organic pollutants carbon monoxide and hydrocarbons,
and the inorganic pollutants nitrogen oxides, sulfur
dioxide, particulates, and low ozone. Smog, a contraction
of the words smoke and fog, is a common term
used to indicate the presence of a mixture of multisource
pollutants in the air around large human settlements.
Indoor Air Pollution
Indoor space is the interior of each working or residential
building in the commercial, public or private sectors,
not including industrial working interiors or outdoor
space. Indoor spaces are: a) private residences; b)
non residential, commercial and public buildings, e. g.
offices, libraries, cinemas, indoor market places, restaurants,
hospitals, schools and indoor sport arenas, and c)
transportation, e. g. the interior of private cars, buses,
aircrafts and subways.
The indoor environment is now more significant for
health considerations than the outdoor environment.
Concerns about potential public health problems due to
indoor air pollution are based on epidemiological evidence
that urban residents spend approximately 90% of
their time indoors. By such activity patterns, they have
more exposure to harmful agents that exist indoors. The
most important pollutants are nitrogen oxides, volatile
organic compounds, formaldehyde, carbon monoxide,
ozone, and suspended particles. If tobacco smoking
is not restricted, a mixture of dangerous pollutants may
be detected. Inside many indoor spaces, airborne allergens
such as dustmites are present, and sometimes even
the radioactive gas radon. Carbon dioxide is a marker of
indoor air pollution rather than a specific pollutant.
Adverse Effects of Air Pollution
Enormous and continually increasing rates of outdoor
air pollution may have significant consequences on the
quality of air, human health and the whole environment.
Local, regional and even global environmental effects
are well known and scientifically proven. Considering
local health effects, increased morbidity and mortality
rates are reported among vulnerable population groups
in highly polluted areas. Usually registered are: a) upper
respiratory tract illnesses; b) lower respiratory tract illnesses
(bronchitis, asthma and pneumonia); c) malignant
diseases of the respiratory tract; d) ocular mucous
membrane illnesses and complaints; and e) decreased
resistance to common allergens. Effects on the local
climate are also pronounced as climate characteristics
Over certain regions of the Earth, air pollution induces
ecosystem acidification and acid deposition ( acid
rain), with both noticeable adverse environmental consequences
(e. g. damage to vegetation), and human
health impairments. Air pollution has also led to deterioration
of the atmosphere on a global scale. The
most important global consequences are ozone layer
depletion in the stratosphere (ozone holes), and the
greenhouse effect. As a consequence of ozone layer
depletion, the amount of harmful short-wave ultraviolet
reaching the Earth’s surface has been enhanced.
The greenhouse effect (global warming of the atmosphere)
is mainly a result of carbon dioxide and
methane being released into the atmosphere due to
burning of fossil fuels and farming practices, respectively.
During the last decade of the 20th century, the US
Environmental Protection Agency consistently ranked
indoor air pollution among the top five risks for health
impairments in general population groups. There is
mounting evidence that exposure to polluted indoor air
is the cause of excessive morbidity and mortality. The
main health consequences of indoor air pollution are
grouped into a) specific building- and home-related
illnesses (SBRI), and b) chemical sensitivity syndromes.
Cross-References
Acid Rain
Chemical Sensitivity Syndromes
Greenhouse Effect
House Dust Mites
Smog
Specific Building- and Home-Related Illnesses
Suspended Particles
References
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