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One of the most important sources of air pollution:


  In my opinion one of the major sources of air pollution that can be observed in modern society is motor vehicles . Modern society is highly dependent on motorized transportation such as cars, trucks, and railways. Movement of people and goods requires energy which relies mostly on the burning of fossil fuels, thus causing emissions and noise with adverse local effects.
In almost all the large cities of the world, air and noise pollution from
motor vehicles are, or are fast becoming, major problems for the physical
and mental health of the people. The industrialized countries, where
86% of the world’s vehicles are to be found, have a long standing and
extensive experience of the problem. In the developing countries, rapid
industrial growth and population increase coupled with rising standards
of living are likely to lead to patterns of motorization that resemble
those of the industrialized countries. Since the 1960s, the world’s
motor vehicle fleet has been growing faster than its population. The
problems are acute in certain cities in both the developing and the
industrialized world and unless controls are applied or strengthened
immediately, the damage to public health will become very serious.
The World Health Organization (WHO) and the United Nations Environment
Programme (UNEP) have had a long standing project within
the Global Environment Monitoring System (GEMS) to monitor the
air quality of urban areas of the world in this period of rapid change
during which nations strive to achieve a sustainable economy without
degradation of the environment. Recently, under the umbrella of the
Healthy Cities Programme, WHO has developed the Air Management
Information System (AMIS) as a successor of the GEMS/AIR
project which acts as an turntable for exchange of information on air
quality management in urban areas of this world.

 And where can we see this type of pollutants?
 This source of air pollution we can see it in the streets. motorized road traffic is the main emission source while public transport is environmentally friendlier than passenger cars.

How wide this source can be sagnificant impact on environment and what are the factors affecting transporting this pollutant to the receptors?
  Worldwide, a quarter of a million people die on the roads every year and ten million are injured, a scale equivalent to war. Motor vehicles are the single biggest source of atmospheric pollution. A new report by the World Health Organization (WHO) showed long-term air pollution from cars in Austria, France and Switzerland triggered an extra 21,000 premature deaths per year from respiratory or heart diseases, more than the total number of annual traffic deaths in the three countries.


So know we can talk about the most dangerous motor vehicle exhaust emissions and their concentration in some countries:

 FU Lixin and Ying YUAN. Beijing's Recent Efforts on Reducing Motor Vehicle Emissions.
Estimate that, in Beiing, 73% of ambient concentration of NOx and 84% of CO is from motor vehicles.
 Results of Roadside Air Monitoring at Hang Xanh Station in Ho Chi Minh city (annual average concentrations)
CO (mg/m3)
1997 - 9.85
1998 - 6.88
1999 - 6.94
2000 - 7.99
Vietnam Standard 40
PM (mg/m3)
1997 - 0.55
1998 - 0.73
1999 - 0.99
2000 - 0.96
Vietnam Standard 0.3
Lead (microgram/m3)
1997 - 2.5
1998 - 2.5
1999 - 2.5
2000 - 2.4
Vietnam Standard 5.0
NO2 (mg/m3)
1997 - 0.097
1998 - 0.119
1999 - 0.122
2000 - 0.139
Vietnam Standard 0.4

And here are some factors that may affect transporting this pollutants to the receptors:

1-traffic  in capital cities which is have no green lands.
2-most of people in modern cities depend on cars ,trucks( automotives)
3-type of fuel used in automotives.
4- Change of climate and global warming which changes the produt of combustion.
5- Topography.
6-Turbulence
7-wind speed and direction
8- Atmospheric stability.

What is the effect of these pollutants on health and environment?
 
1-CO and CO2, into the atmosphere which contribute to global warming and climate change but the products of combustion also produce additional local pollution. Transportation accounts for about 80% of man-made emissions in Gauteng. The most severe CO problems are found
in cities where vehicle emissions are concentrated between rows of tall buildings. The ambient concentration of
carbon monoxide on a particular day depends on the number of vehicles and the weather.
Carbon monoxide reduces the supply of oxygen to the human body. Oxygen transporting cells usually replace carbon
dioxide with oxygen. However, in the presence of carbon monoxide, they will replace the oxygen and carbon dioxide
with carbon monoxide.
Carbon monoxide at the levels found in some major metropolitan areas can lead to heart and circulatory systemrelated diseases.

2-the emission of nitrogen oxides, sulphur and carbon particulates (soot) can be very detrimental to health.
the human health effects of NO 2 exposure have not
been fully characterized. The toxicological evidence has indicated
hypotheses to be tested in human populations but limitations of the
clinical and epidemiological studies have precluded definitive testing
of these hypotheses. There is a need to characterize factors that
may modulate response to NO2 exposure (Samet & Utell, 1990).
Guidelines proposed by WHO (WHO, 1995a) are the following: a 1-
h guideline of 200 μg/m 3 (0.11 parts per million [ppm]) and an annual
guideline of 40 to 50 μg/m 3 (0.021 to 0.026 ppm)

3- Ozone and other photochemical oxidants and its effect s are  coughing and chest pain.

4- Lead: In those countries which do not yet use unleaded petrol, the addition
of alkyl lead additives in motor fuels accounts for an estimated 80-90% of lead in ambient air and it makes effect to kidney ,liver and nervous system of the human.

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