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| Green City : Air Quality |
 In both developed and rapidly industrialising
countries, the major historic air pollution problem has typically
been high levels of smoke and sulphur dioixide arising from the
combustion of sulphur-containing fossil fuels such as coal for
domestic and industrial purpose.
The major threat to clean air is
now posed by traffic emissions. Petrol and diesel-engined motor
vehicles emit a wide variety of pollutants, principally carbon
monoxide (CO), oxides of nitrogen (NOx), volatile organic compounds
(VOCs) and particulates (PM10), which have an increasing impact on
urban air quality. In addition, photochemical reactions resulting
from the action of sunlight on nitrogen dioxide (NO2) and VOCs from
vehicles leads to the formation of ozone, a secondary long-range
pollutant, which impacts in rural areas often far from the original
emission site.
Acid rain is another long-range pollutant influenced
by vehicle NOx emissions. In all except worst-case situations,
industrial and domestic pollutant sources, together with their
impact on air quality, tend to be steady-state or improving over
time. However, traffic pollution problems are worsening world-wide.
Below is an introduction to the principal pollutants produced by
industrial, domestic and traffic sources:
Achieving and maintaining good air quality is
crucial to the public health and economic vitality.
The surrounding air, both outdoors and indoors, has the potential to
affect human health, attitudes, productivity, and people's ability
to enjoy their lives. It is important to maintain the quality of the
outdoor air since all life forms depend on it, and since the quality
of indoor air is dependent on that of the outdoors. In addition, a
recent study reveals that Americans spend 90% of their lives
indoors, with the result that there is now an increased awareness of
the importance of the quality of the indoor air.
Automobiles are the major source of air pollution, and
measures must be taken to reduce public dependence on
gasoline-fueled personal vehicles as a primary means of
transportation. Advances are being made in the design of
alternatively fueled vehicles, which reduce tail-pipe emissions, and
there are many accommodations that could make to
encourage less-polluting modes of transportation.
In addition, environmental tobacco smoke, fireplaces, barbecues,
construction practices, improper building ventilation and many
industrial activities have a negative impact on the quality of the
air. Notable examples of stationary sources of
pollution include roof tar,
power-transmitting stations, dry cleaning establishments (which emit perchlorethylene), and asphalt paving.
The economic health of the City is dependent on good air quality. Acids from air pollution
corrode metals, building exteriors, and painted surfaces. As an
esthetic matter, clear air is crucial for tourism as well as for
attracting and keeping other employment centers in the Bay Area.
Creating and maintaining superior air-quality conditions provides a
high quality of life and makes good business sense.
In addition, nitrogen oxides from combustion-related air pollution
make up a surprisingly large one-third of total sources of ocean
pollution. The presence of excess nitrogen in standing bodies of
water leads to runaway growth of algae, which blocks sunlight and
suffocates fish. In addition, a growing opinion in the scientific
community blames airborne chemicals for the increasingly violent and
unpredictable weather being experienced around the world, leading to
undefined, but potentially enormous costs. The international
insurance industry has recognized this risk to its livelihood by
establishing an emergency task force on global climate change.
Many complex and interrelated factors affect indoor air quality.
These factors involve the emission of odors, particulates, volatile
organic compounds (VOCs), microbial volatile organic compounds (MVOCs),
and radon into the air. Examples of such factors include the outdoor
air quality; emissions from construction, building materials, indoor
occupant activities, building maintenance products, cleaning
products, personal care products, and equipment (computers, copy
machines, etc.); molds and mildew; building ventilation systems;
radon emissions from below-grade rock; and environmental tobacco
smoke.
 Research is increasingly showing links between these factors and
human health. Particulates, VOCs, MVOCs and radon can have a
negative impact on human health. Some of these impacts have
short-term and reversible health effects, while others cause more
serious, long-lasting and even life-threatening health effects.
Health problems that may result from indoor air quality are
classified as follows:
Sick Building Syndrome describes a collection of symptoms
experienced by building occupants that are generally short-term and
disappear after the individual has left the building. Examples of
such symptoms include sore throat, fatigue, lethargy, dizziness,
lack of concentration, respiratory tract irritation, headache, eye
irritation and other cold- and allergy-like symptoms.
Building-Related Illnesses are more serious than sick building
condition ailments and are clinically verifiable diseases that can
be attributed to a specific source or pollutant within a building.
Examples of such conditions include cancer, Legionnaire's disease,
and carbon monoxide poisoning.
Multiple Chemical Sensitivities: While much more research is needed
to understand multiple chemical sensitivities, it appears that for
some people, exposure to low levels of a variety of chemicals can
produce many diverse symptoms in more than one body-organ system.
Unacceptable indoor air quality also carries an economic impact.
Costs due to lost productivity when employees are affected by sick
building syndrome are significant to local companies. Furthermore,
when building occupants experience sick building syndrome or
building-related illness, the building owners and responsible design
professionals may be exposed to increased liability. Moreover, when
poor air quality has a negative impact on the health of residents,
there are increased demands on the health care system, which
ultimately translates into increased health care costs for all
businesses and residents.
Finally, when cities begin to implement standards for good indoor
air quality, the global effect will be to reduce ozone depletion and
to minimize climate changes. These effects are difficult to
quantify, but are ultimately some of the more important goals of a
sustainable world.
Source: http://www.sustainable-city.org/ |
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