Air Pollution, Sources and Characteristics

"Air pollution is the presence of substances in air in sufficient concentration and for
sufficient time, so as to be, or threaten to be injurious to human, plant or animal life, or
to property, or which reasonably interferes with the comfortable enjoyment of life and
property.

Air pollutants arise from both man made and natural processes. Pollutants are also
defined as primary pollutants resulting from combustion of fuels and industrial
operations and secondary pollutants, those which are produced due to reaction of
primary pollutants in the atmosphere.

The ambient air quality may be defined by the
concentration of a set of pollutants which may be present in the ambient air we breath
in. These pollutants may be called criteria pollutants. Emission standards express the
allowable concentrations of a contaminant at the point of discharge before any mixing
with the surrounding air."

"Nitrogen oxides

Almost all NOx emissions are in the form of NO, which has no known adverse health
effects in the concentrations found in atmosphere. However, NO can be oxidized to
NO2 in the atmosphere, which in turn may give rise to secondary pollutants, which are
injurious. NO2 may also lead to formation of HNO3, which is washed out of the
atmosphere as acid rain.

Carbon monoxide
Most of the CO emissions are from transportation sector. Peak concentrations occur at
street level in busy urban centers particularly when there is no atmospheric mixing as it
happens during winter season. Carbon monoxide interferes with blood's ability to carry
oxygen. With the blood stream carrying less oxygen, brain function is affected and heart
rate increases in an attempt to offset the oxygen deficit.

Breathing between 20 to 35 ppm CO in air for 4 h results in impairment of time related response. Individuals with heart condition may experience chest pain. Exposure to 100ppm concentration would result in dizziness.

Effects of Sulphur Dioxide on Health

Source and Full Article
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