PM10 Particulates
PM10 describes the fraction of airborne particulate matter that is less than 10 microns in size. Fine particles are of the
greatest concern since they are capable of being easily transported over long distances on currents of air. Also, fine particles
may be drawn into the respiratory airways where they may adversely affect health. Recently, the attention of scientists has
been drawn towards studying the PM2.5 fraction and even smaller particles, which can penetrate the very deepest parts of the
lung.
PM10 and other particulate matter may vary considerably in chemical and physical composition. The principal sources
of these particles are combustion processes, including traffic and industry.
Nitrogen Dioxide (NO2)
Nitrogen dioxide is one of a number of nitrogen oxides, which are formed during high temperature combustion processes. Road
traffic is the main source, accounting for
approximately 50% of all European emissions. Therefore, concentrations tend to be highest in urban environments with high
traffic levels. Large industrial sources can also have a significant impact.
Nitrogen dioxide is a respiratory irritant and also plays a part in the production of another atmospheric pollutant,
Ozone. Nitrogen oxides remain in the atmosphere for approximately one day before they are oxidised to nitric acid. Nitrogen
oxides are therefore a contributory factor in the production of acid rain.
Air quality is monitored for Nitrogen Dioxide at various sites across the District .
Ozone (O3)
Ozone is a very reactive chemical, which is potentially toxic to both plants and animals. In the Stratosphere, ozone helps
to protect the earth from the harmful effects of ultra-violet rays from the sun. However at ground level it is a pollutant.
Unlike the other pollutants mentioned above, ozone is not emitted directly. Rather, it is formed as a result of a complex
series of reactions involving hydrocarbons, sunlight and nitrogen dioxide (NO2). The involvement of sunlight in this process
means that ozone levels tend to be highest in summer. The reactions take time to generate ozone and the highest concentrations
are frequently experienced many miles away from the source of the pollution, perhaps in rural areas. In fact, a significant
proportion of ozone incidents experienced in the UK are due to pollution imported from abroad. The problem of ozone pollution
can therefore only be adequately dealt with as a result of international agreements.
Sulphur Dioxide (SO2)
Sulphur dioxide is a corrosive acid gas which combines with water vapour in the atmosphere to produce acid rain. SO2 in ambient
air is capable of causing harm to human health and the environment. It is associated with aggravation of asthma and chronic
bronchitis, and has been known to damage vegetation, soils, watercourses and building materials.
Sulphur dioxide is mainly formed as a result of the combustion of fossil fuels in power stations. Some areas, which
rely heavily upon the use of coal for domestic heating, may also suffer localised pollution as a consequence.
Carbon Monoxide (CO)
Carbon monoxide is a colourless, odourless and tasteless gas that is produced in the process of combustion, such as the burning
of fossil fuels or in a car engine. It is the most dangerous of all the pollutant gases and can cause death in very high concentrations.
Once emitted into the atmosphere CO is slowly oxidised to CO2.
Vehicle emissions are again a major contributor. CO is produced by the incomplete combustion of fossil fuel. The main
source of outdoor exposure (aside from smoking) is general pollution from vehicle exhausts, although indoor sources can account
for a larger proportion than traffic.
