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1.1 Introduction 3

• local
• urban
• regional
• transboundary
• global.
vel Local le

el,
v
At the local le air pollution concerns a region within a 5-km radius. It is characterized
by high concentrations of specific pollutants that may come from automobiles or industrial
activities in that region. For example, emissions from vehicles can lead to high concentra-
f
tions of carbon monoxide near trafic-jammed roads. High buildings and the terrain can
also contribute to high local concentrations of pollutants.
Urban areas
In urban areas, there are three major types of air pollution found (EEA, 2003):

v
• High annual aerage concentration leels of various pollutants, e.g. benzene, lead,
v
sulfur dioxide (SO 2 ), and particulate matter (PM). As in the case of air pollution at the
v
el, local le this type of pollution is linked to specific pollutants resulting from either
large industrial and power plants or automoti ehicles. e v v
• Winter-type smog, characterized by high concentrations of SO 2 and PM that arise
mainly from the combustion of coal and fuels with a high content of sulfur . This kind
of pollution occurs in urban areas with manwer plants or industrial units clustered y po
together, where low temperatures and mist are observed in the year. It has been also
termed “industrial pollution.”
• Summer-type smog, characterized by high concentrations of carbon monoxide, v olatile
organic compounds (VOCs), and nitrogen oxides (NO x ). It is also called “photochemi-
cal smog” or “LA smog”, since it first appeared in Los Angeles. This type of pollution
ehicles,
v
is closely connected to automotie v and its formation is fored by sunlight v a
and high temperatures.
The first two types are associated with primary pollutants, namely compounds such as ,
nitrogen oxide (NO), carbon monoxide (CO), and sulfur dioxide (SO 2 ) that are emitted
directly into the atmosphere from various sources, whereas the third type of urban air
pollution is a more complex phenomenon associated with secondary pollutants, which are
formed from reactions between primary pollutants in the atmosphere, usually in the pres-
ence of sunlight and heat. Specif various volatile organic compounds react in the
ically
,
atmosphere with nitrogen oxides by means of the ultraviolet radiation of sunlight, produc-
ing the so-called photochemical smog consisting of nitrogen dioxide, various oxidized
forms of organic compounds, and ozone. The pollution of primary pollutants is easier to
treat than the one associated with secondary pollutants, because the latter are produced by
various organic compounds participating in numerous photochemical reactions.
Approximately half of the world’s population now lives in urban areas, and half of these
people suffer an atmosphere containing harmful amounts of substances such as sulfur
.
dioxide, ozone, and particulate matterApproximately 4000 people died from lung and
heart conditions during a London smog episode in December 1952. Globally, around 50%
of cases of chronic respiratory illness are now connected with air pollution. The most