170 Ecology and Applied Environmental Science
• Sulphur oxides SO 2 and SO 3
• Ozone O 3
• Suspended particulate matter (PM)
• Lead compounds (Chapter 7, Section 7.4)
• Hydrocarbons and other volatile organic compounds (VOCs) (Chapter 7,
Section 7.2)
Carbon monoxide (CO) is a colourless, odourless, tasteless and extremely
poisonous gas. In the air, it is oxidized to carbon dioxide. It is produced by
incomplete burning of carbon at a high temperature with inadequate presence of oxygen. Its appearance in the air of a city is almost exclusively due
to exhaust fumes resulting from incomplete burning in the internal combustion engines of cars. It is also a component of cigarette smoke. Its presence
in the respirable air in a 0.1% concentration by volume can be fatal. This
gas is especially dangerous because it is not easily perceived by the human
senses. The first symptoms of poisoning include sleepiness and headache,
followed by loss of senses, asphyxia and death. When inhaled, it reacts with
haemoglobin, being attracted by it approximately 210 times more strongly
than oxygen is, thus substituting oxygen in the blood. Long-term exposure
can be a factor for mental retardation or chronic illness. Carbon monoxide
contributes to photochemical pollution and it also indirectly amplifies the
greenhouse effect because it gets oxidized to carbon dioxide when found in
the atmosphere.
Carbon dioxide (CO 2 ) is produced by burnings and its presence in the air
does not harm human health in its usual low concentrations, but in very
high concentrations it causes asphyxia. Its accumulation in the atmosphere
is the main factor for the amplification of the greenhouse effect.
Nitrogen monoxide (NO) is mainly produced by the oxidation of atmospheric N 2 either in internal combustion engines through the conditions of
high temperature and pressure that prevail there or by the burning of natural gas; it is also produced by the burning of nitrogen contained in fossil
carbon or petroleum. When in the atmosphere, it is gradually oxidized to
istic brownish-yellow hue in the air, especially in cities. By further oxidation, nitrogen pentoxide (N 2 O 5 ) may be formed which is an anhydride of
nitric acid HNO 3 . Generally, these oxides cause several harmful effects in
human health. Nitrogen hypoxide (N 2 O) occurs in significant concentrations, not specifically in cities but in the whole atmosphere as well, and it
is a greenhouse gas. The average global concentration of nitrogen oxides in
the atmosphere is only 3 × 10 –3 ppm, but in some urban areas it reaches the
level of 1–2 ppm.
Gaseous hydrocarbons (HCs) are volatile components of fluid fuels as well
as products of incomplete burning. Some are considered to be carcino genic.
• Sulphur oxides SO 2 and SO 3
• Ozone O 3
• Suspended particulate matter (PM)
• Lead compounds (Chapter 7, Section 7.4)
• Hydrocarbons and other volatile organic compounds (VOCs) (Chapter 7,
Section 7.2)
Carbon monoxide (CO) is a colourless, odourless, tasteless and extremely
poisonous gas. In the air, it is oxidized to carbon dioxide. It is produced by
incomplete burning of carbon at a high temperature with inadequate presence of oxygen. Its appearance in the air of a city is almost exclusively due
to exhaust fumes resulting from incomplete burning in the internal combustion engines of cars. It is also a component of cigarette smoke. Its presence
in the respirable air in a 0.1% concentration by volume can be fatal. This
gas is especially dangerous because it is not easily perceived by the human
senses. The first symptoms of poisoning include sleepiness and headache,
followed by loss of senses, asphyxia and death. When inhaled, it reacts with
haemoglobin, being attracted by it approximately 210 times more strongly
than oxygen is, thus substituting oxygen in the blood. Long-term exposure
can be a factor for mental retardation or chronic illness. Carbon monoxide
contributes to photochemical pollution and it also indirectly amplifies the
greenhouse effect because it gets oxidized to carbon dioxide when found in
the atmosphere.
Carbon dioxide (CO 2 ) is produced by burnings and its presence in the air
does not harm human health in its usual low concentrations, but in very
high concentrations it causes asphyxia. Its accumulation in the atmosphere
is the main factor for the amplification of the greenhouse effect.
Nitrogen monoxide (NO) is mainly produced by the oxidation of atmospheric N 2 either in internal combustion engines through the conditions of
high temperature and pressure that prevail there or by the burning of natural gas; it is also produced by the burning of nitrogen contained in fossil
carbon or petroleum. When in the atmosphere, it is gradually oxidized to
istic brownish-yellow hue in the air, especially in cities. By further oxidation, nitrogen pentoxide (N 2 O 5 ) may be formed which is an anhydride of
nitric acid HNO 3 . Generally, these oxides cause several harmful effects in
human health. Nitrogen hypoxide (N 2 O) occurs in significant concentrations, not specifically in cities but in the whole atmosphere as well, and it
is a greenhouse gas. The average global concentration of nitrogen oxides in
the atmosphere is only 3 × 10 –3 ppm, but in some urban areas it reaches the
level of 1–2 ppm.
Gaseous hydrocarbons (HCs) are volatile components of fluid fuels as well
as products of incomplete burning. Some are considered to be carcino genic.