Pollutants and their effects
During flight, aircraft engines emit carbon dioxide, oxides of nitrogen, oxides of sulphur, water vapour, hydrocarbons and particles. Particles consist mainly of sulphate from sulphur oxides, and soot. These emissions are all issues in relation to climate change (see later section). Nitrogen oxides, sulphur oxides, hydrocarbons and particles (sometimes called particulates) are also issues for local air quality.
Nitrogen oxides, known as NOx, are considered to be a serious air quality issue. The NOx is used to refer to a group of compounds comprising nitrogen and oxygen. Nitric oxide (NO) is a product of combustion that is largely harmless, but once the gas is in the atmosphere, it becomes oxidised, forming nitrogen dioxide (NO2), a colourless, odourless gas which is can irritate the lungs and lower resistance to respiratory infections such as influenza. In 1998, 1753 tonnes of NOx were released into the atmosphere. 53% of these were from transport, mostly road transport, but some from aviation.
Particles are the result of incomplete combustion, and therefore they consist of unburnt fuel and hydrocarbons known to be carcinogenic. Particles are measured in a number of different size fractions according to their mean aerodynamic diameter. Most monitoring is currently focussed on PM10, but the finer fractions such as PM2.5 and PM1 are becoming of increasing interest in terms of health effects. Fine particles can be carried deep into the lungs where they can cause inflammation and a worsening of the condition of people with heart and lung diseases. In addition, they may carry surface-absorbed carcinogenic compounds into the lungs.
Sulphur dioxide (SO2) is less of an issue, although moderate concentrations may affect the lungs of asthmatics and high concentrations can be harmful to more healthy people when particle concentrations are high.
Hydrocarbons are, as the name suggests, compounds of hydrogen and carbon that are vaporise at room. They are a kind of Volatile Organic Compound (VOC). One of the most toxic hydrocarbons produced by combustion of petroleum-based fuels is Benzene, which is known to cause leukaemia.
UK and EU action on Air Pollution
In 2000, The UK Government published the Air Quality Strategy setting objectives for the reduction of a number of pollutants in the air, including those outlined above. The targets were as follows:
|
Pollutant |
Objective |
Date to be achieved by |
|
NO2 |
Annual mean of 40µg/m3 Upper limit – 1 hour mean of 200µg/m3 not exceeded more than 18 times a year |
31/12/05 |
|
PM10 |
Annual mean of 40µg/m3 (20 by 31/12/2010) Upper limit – 1 hour mean of 50µg/m3 not exceeded more than 35 times a year |
31/12/04 |
|
Benzene |
Annual mean 5 µg/m3 |
31/12/10 |
|
Sulphur dioxide |
Various targets, but annual mean of 20 µg/m3
|
31/12/00 |
The 40µg/m3 limit on NOx is also being introduced across Europe by the EU. Other binding targets from the EU are as follows:
Directive 2002/3/EC gives a limit on NOx of 120μg/m3 for an 8-hour average, not to be exceeded more than 25 days pa, averaged over 3 years, to be met by 2010.
The Stage 2 EU limit for particulates
gives a daily value of 50 μg/m3 not be exceeded more than 7
times per annum, and an annual average of 20μg/m3
Air Pollution at Southampton Airport
In March 2006, the Chartered Society of Physiotherapy published a report which identified nine airports which were in breach of the EU target on NOx. Southampton was around 50% over the limit. The airport have since cited a study they commissioned, which found that only 5.55% of the NOx is attributable to them. This does not alter the fact that expansion of the airport would increase the amount of NOX in the local area.