Effects and while idling at stoplights. Under calm conditions,

Effects
of Urban Design and Planning on Air Quality

“6.5 million People
are dying annually from air pollution and 92 per cent of the world’s populations
are living in places where levels exceed recommended limits” says a report
by United Nations. The above
statement rings an alarm, immediately making us think what could have been the
various reasons for this state of affairs. Air pollution, other than being the
major contributor to global warming, has also paved way for harmful Public
Health conditions globally. Though there are several contributors to air
pollution, Urban Design and Planning of a city, to a large extent determines
air quality in urban areas, particularly in the developing countries.

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To actively reduce poor air quality in cities,
we need to understand and study the urban climate before we design our urban
space. The shape of a
city and distribution pattern of land use affects air quality and its health
impact.  The urban shape determines, locations of emission
sources, where people predominantly spend their time and commute. Air pollution
in urban areas is characterized mainly by pollutants such as Carbon Monoxide,
Nitrogen Dioxide, Ozone and Particulate Matter. Design factors that affect air
quality in an urban area includes Density, Land Use Mix ,
Transit
Accessibility, pedestrian-environment
and patterns of development. Ambient air pollutant concentrations are distributed
non–uniformly in urban areas, creating hot spots mostly in central business
district, traffic intersections and signalized roadways (Kandlikar, 2007). Street- level air pollution is very critical in determining
the air quality in urban areas. Concentrations
in streets are generally higher than in urban background sites due to the
proximity to high traffic density and poor dispersion conditions 8.
Therefore, pollutant concentrations in these street canyons are likely to
exceed air quality standards. Factors that affect street level air pollution
are Emission
Levels, proximity to Road,
Air
Circulation ( winds, breezes, inversions),  and
sinks. ( Sprin et al,1986).  Vehicles emit fewer air pollutants at even speeds, when engines operate more
efficiently, and emit greater quantities in stop-and-go traffic and while idling
at stoplights. Under calm conditions, the concentration of air pollutants can therefore
vary significantly along a single street or between two streets a block apart. Carbon
Monoxide emissions, for example, tend to peak at intersections, where concentrations
may be ten times higher in the Intersection than at a point eighty meters further
down the road (Horowitz , 1982). This can be evidently seen as a huge urban
planning problem in developing countries. New Delhi, India is one significant example,
to illustrate how various facets of Urban Planning like Land Use, built area,
lack of sufficient green cover and transportation planning are major
contributors among various other myriad reasons to the city’s current state of
air quality emergency.  Though there has
been efforts from policymakers in creating a framework to combat this issue,
unifying people’s efforts through education and awareness is one area that
would make a huge difference if worked upon. Green infrastructure ; that
includes green building technologies, green construction materials , efficient  waste generation and management systems, would
effect the urban design in a positive way, towards achieving a goal for cleaner
air. ( Rizwan et al, 2013).

Though on one hand simplest and proven to improve
air quality has always been associated to reducing the pollutants emitted from
the sources , the serious impacts on human health address the importance of a
more holistic approach for improving the urban air quality. It is important
that we all work together to improve air quality in cites and urban designers
and planners find ways to improve existing systems as well as bring forth
innovations in the field of Green Infrastructure. After all, clean air for this
planet’s residents is indeed a primary requisite for public health and
well-being.

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