Air Quality Pollutants

This is the most common pollutant in the United Kingdom for which Air Quality Management Areas have been declared. There are objective levels  set in regards to the annual mean and also for the number of times the 1-hour mean level can be exceeded.

The health impacts of NO2 include inflammation reaction of the airways if exposed to high concentrations of NO2 while long term exposure may affect lung function and cause respiratory symptoms.

The main source of NO2 is via combustion processes and in particular road transport, power generation, and industrial and commercial combustion processes.

Is a non-gaseous air pollutant, made up of a collection of solid and/or liquid materials of various sizes. This includes primary components (released directly from the source into the atmosphere), and secondary components (formed in the atmosphere by chemical reactions).

The PM10 element refers to particles that are less than 10 microns in diameter and comprise of both coarse and fine particles; PM2.5 refers to very fine particles that are smaller than 2.5 microns.

PM10 objectives have been set for both annual mean and 24 hour mean levels. PM2.5 objective for annual mean level for Scotland was set in the Air Quality (Scotland) Amendment Regulations 2016.

The main sources of particulate matter come from:

• Primary component sources include combustion, such as road traffic, industry and solid fuel heating (wood burning), and coarse particles from suspended soils and dusts (e.g. from the Sahara), sea salt, biological particles and particles from construction work into the atmosphere. Another major source of PM10 is from motor vehicle brake and tyre dust.

• The source of secondary components is the formation of NO2 by chemical reactions in the atmosphere.

These particles can have a profound impact on the health of individuals at high concentrations, and typically cause inflammation of respiratory conditions. The finer element can penetrate deep into the lungs and can eventually give rise to lung and heart related illnesses and diseases, i.e. cardiovascular diseases. There is now a tendency to view PM2.5 rather than PM10 as the source that is most prejudicial to health. PM is a non-threshold substance which means that it is not currently possible to discern a threshold concentration below which there are no effects on the whole population’s health.

Sulphur dioxide (SO2) is produced when a material, or fuel, containing sulphur is burned. Globally, much of the sulphur dioxide in the atmosphere comes from natural sources, but in the UK the predominant source are power stations burning fossil fuels, principally coal and heavy oils. Widespread domestic use of coal can also lead to high local concentrations of SO2.

SO2 has significant and an acute impact on health, typically affecting the respiratory system, causing inflammation of the lungs. Those with poor health and suffer conditions such as asthma, can be more susceptible to illness through exposure. It is also damaging to the environment and can kill or damage plant life by forming lesions on the leaves of plants. SO2 is highly soluble and can give rise to acid rain forming sulphuric acid, which can damage ecosystems and plant life as well as buildings and corroding infrastructure.

Benzene is a VOC (Volatile Organic Compound) which is a minor constituent of petrol. The main source of benzene in the atmosphere in Europe comes from the distribution and combustion of petrol. The escape of petrol vapour at petrol storage facilities is another source in the atmosphere.

The objective level for benzene is set as an annual mean.

The health effects associated with benzene are often result from long-term exposure, and include cancer, organ damage specifically to the liver and kidneys, also the nervous and reproductive system can be affected, and in infant births resulting in defects and disorders.

1,3-butadiene, like benzene, is a VOC (Volatile Organic Compound) emitted into the atmosphere principally from fuel combustion of petrol and diesel vehicles. 1,3-butadiene is also an important chemical in certain industrial processes, particularly the manufacture of synthetic rubber.

The objective level for 1,3-butadiene  is set as an annual mean.

The main health effects associated with 1,3-butadiene come from long term exposure with known possible chronic health effects including cancer, central nervous system disorders, liver and kidney damage, reproductive disorders, and birth defects.

Carbon monoxide is particularly toxic and has the added danger of being virtually un-detectable and as such is sometimes known as the "silent killer" due to it being an odourless and colourless gas. The most prevalent source of CO comes from incomplete combustion from motor vehicles. It is predominantly produced by road transport, in particular petrol-engine vehicles. Other major sources are from in the household, from gas stoves/boilers and domestic fires.

The objective level for carbon monoxide is set as a running 8 hour mean.

The problem from a health aspect is that the CO combines with haemoglobin and prevents the normal transport of oxygen by the blood. This effectively starves the body of it’s oxygen supply with early symptoms of CO poisoning being headaches, tiredness, drowsiness and chest pains. Other health effects are on the functioning of the central nervous system and to the heart, it can also have severe effect on the foetus of pregnant woman.

The major source of lead in the atmosphere historically has been from road transport where it was used as an anti-knocking additive in petrol. In 1990, road transport accounted for 96% of lead emissions; since the phasing out of lead in petrol in 1999 emissions have reduced markedly and now road transport accounts for only 2% of emissions. In recent years, industry, in particular secondary non-ferrous metal smelters have become the most significant contributors to emissions of lead. The highest concentrations of lead are now found around these installations in industrial areas.

The objective level for lead is set as an annual mean.

In high concentrations lead can cause damage to the central nervous system. At low levels lead exposure can cause impaired intellectual development and concentration in children. Acute lead exposure is rare in the UK.

Ozone is not emitted directly from any man-made source in any significant quantities. In the lower atmosphere, ozone is primarily formed by a complicated series of chemical reactions initiated by sunlight. These reactions can be summarised as the sunlight-initiated oxidation of volatile organic compounds (VOCs) in the presence of nitrogen oxides (NOx). The sources of VOCs are similar to those described for NOx above, but also include other activities such as solvent use, and petrol distribution and handling.

The chemical reactions do not take place instantaneously, but can take hours or days, therefore ozone measured at a particular location may have arisen from VOC and NOx emissions many hundreds or even thousands of miles away and is therefore known as ‘trans boundary’.

The objective level for ozone is set as a 8 hour mean however this is not currently included in Scottish Regulations and therefore is not routinely monitored by Local Government Authorities, including Dundee City Council.

Ozone in high concentrations can cause irritation to the eyes and the airways of the lungs and increasing the symptoms of those suffering from asthma and lung diseases. At very high concentrations ozone can damage airways leading to inflammatory reactions. There is also a potential for ozone to damage ecosystems.

Polycyclic Aromatic Hydrocarbons (PAHs) belong to a large group of organic compounds ; several individual PAHs have been shown to be carcinogenic.

EPAQS have recommended a standard for PAHs of 0.25 ng/m3 using benzo[a]pyrene as a marker compound.