- Particulate matter (PM10)
Particulate matter (PM) in the air is a priority pollutant internationally
its adverse effects on public health as well as its negative effects on
ecosystems, materials and on climate. Additionally, it is a key contributor
visibility incidents.Particulate pollution in the atmosphere derives from a
range of sources including transportation of natural materials like sand;
construction activities; traffic and industry. Secondary particles are
atmospheric reactions between gases, such as the photochemical oxidation of
Airborne particles cover a wide range of sizes. Large particles generally
out onto surfaces and cause nuisance effects through soiling of buildings,
and fabrics. Human health concerns are generally centered around fine
matter with an aerodynamic diameter of 10 micrometres (μm) or less, known as
These particles can penetrate deep into the human respiratory system and are
for a variety of health effects including effects on the respiratory and
systems, asthma and premature death. Health effects of particulate matter
in the presence of high concentrations of SO2, as the two
- Nitrogen dioxide (NO2)
All combustion processes produce oxides of nitrogen. Nitrogen dioxide
is associated with adverse human health effects and is produced mainly
atmospheric oxidation of nitric oxide, which is produced during combustion
fuels. Sources of nitrogen oxide emissions include road traffic, power
Nitrogen dioxide can affect the respiratory system causing inflammation of
People with asthma or respiratory diseases are particularly sensitive and
effects at low concentrations.
- Sulphur dioxide (SO2)
Sulphur dioxide (SO2) is a gas produced from burning fuel and
materials which contain sulphur contaminants. Typical sources include
power stations, oil and gas processing, industry and road traffic.
Inhalation of sulphur dioxide causes constriction of the airways leading to
difficulties, particularly in those suffering from asthma and chronic lung
SO2 can also lead to the formation of acid rain which can lead to
ecosystem damage in rivers and lakes, sometimes thousands of kilometers from
original emission source. Direct and indirect impacts on vegetation are also
to occur at lower concentrations than those affecting human health.
- Carbon monoxide (CO)
Carbon monoxide (CO) is a colourless, odourless gas which is produced by the
combustion of hydrocarbon fuels. The main source of CO is road traffic, in
petrol-engine vehicles. The main threat to human health from carbon monoxide
from the formation of carboxyhaemoglobin in the blood, which substantially
the uptake and transport of oxygen in the body. People who suffer from
diseases which affect delivery of oxygen to the heart and brain (e.g.
disease) are at particular risk.
- Ozone (O3)
Ozone (O3) is a secondary pollutant which is formed in the
during chemical reactions involving nitrogen oxides, volatile organic
(VOCs) and sunlight. These chemical reactions take place over several hours
days, depending on the VOCs present. As a consequence, ozone measured at a
location could have been formed from precursor compounds produced hundreds
thousands of kilometers away. Once formed, ozone then drifts in the
the influence of meteorological conditions. Maximum concentrations are
generally found some distance downwind from the source emissions.
in urban areas with high levels of traffic are often reduced due to the
between ozone and nitric oxide, resulting in the formation of nitrogen
Ozone is also toxic to plants and can cause leaf necrosis and affect
and therefore reducing production of crops and trees.
- Volatile organic compounds (VOC)
Volatile organic compounds (VOCs) is a term given to a wide class of
including aliphatic, aromatic and halogenated hydrocarbons, aldehydes,
and amines. They are important in the formation of ozone and can have a
of health effects. Some species are directly toxic to humans and some
odours at very low concentrations.
- Lead (Pb)
Lead is a naturally occurring metallic element which is found in the
as small particles. Industrial sources of lead include battery manufacture
metal smelting. Road traffic used to be the dominant source of lead in urban
as it was used as an additive in petrol. In recent years, its use in petrol
been phased out and this is no longer a major source.
Exposure to lead can have a variety of human health effects, including
the synthesis of hemoglobin, effects on the kidneys, gastrointestinal system
effects on the nervous system. It has also been shown to have a negative
on childhood neurological development.