According to the World Health Organization (WHO), seven million people worldwide die as a consequence of air pollution every year. For around 20 years, studies have shown that air-borne particulate matter negatively affects human health. Now, in addition to already investigated particle sources like emissions from heating systems, industry and road traffic, aircraft turbine engine particle emissions have also become more important.

In a unique, innovative experiment, researchers have investigated the effect of exhaust particles from aircraft turbine engines on human lung cells.

The cells reacted most strongly to particles emitted during ground idling.

It was also shown that the cytotoxic effect is only to some extent comparable to that of particles from gasoline and diesel engines.The primary solid particles, i.e. those emitted directly from the source, have the strongest effect on people in its immediate vicinity. 

Now a multidisciplinary team, led by lung researcher Marianne Geiser of the Institute of Anatomy at the University of Bern, together with colleagues from Empa Dübendorf and the University of Applied Sciences and Arts Northwestern Switzerland (FHNW), has shown that primary soot particles from kerosene combustion in aircraft turbine engines also cause direct damage to lung cells and can trigger an inflammatory reaction if the solid particles are inhaled in the direct vicinity of the engine.

The researchers demonstrated for the first time that the damaging effects also depend on the operating conditions of the turbine engine, the composition of the fuel, and the structure of the generated particles.

Beechcraft 200 Super King Air No 240 showing soiling of the engine panels with soot from exhaust gasses.

Extremely small particles in the nanoscale range

Particles emitted from aircraft turbine engines are generally ultrafine, i.e. smaller than 100 nm. By way of comparison, a human hair has a diameter of about 80,000 nm. When inhaled, these nanoparticles — like those from other combustion sources -efficiently deposit in the airways. In healthy people, the well-developed defense mechanisms in the lungs normally take care of rendering the deposited particles ineffective and removing them from the lungs as quickly as possible.

However, if the inhaled particles manage to overcome these defense mechanisms, due to their structure or physico-chemical properties, there is a danger for irreparable damage to the lung tissue. This process, already known to researchers from earlier experiments with particle emissions from gasoline and diesel engines, has now also been observed for particle emissions from aircraft engines.

Toxicity depends on the operating conditions of the turbines and the type of fuel

Evidence of increased cell membrane damage and oxidative stress in the cell cultures was identified. Oxidative stress accelerates ageing of cells and can be a trigger for cancer or immune system diseases.

Overall, according to the researchers, it has been demonstrated that the cell-damaging effect caused by exposure to particles generated by the combustion of gasoline, diesel and kerosene fuel are comparable for similar doses and exposure times.

Additionally, a similar pattern was found in the secretion of inflammatory cytokines after exposure to gasoline and kerosene fuel particles.

Aerosols: distance from the source is crucial

Aerosols are the finest solid or fluid substance suspended in the air. In combustion processes, the composition of ultrafine particles is highly variable. In addition, aerosols are unstable, and they are modified after their formation. Primary ultrafine solid particles have a high diffusion velocity. As a result, at high concentrations such particles either stick together or attach to other particles. Therefore, the effect of primary ultrafine particles depends on the distance from the source, implying that there is a difference depending on whether a person is close to the source (such as people at the roadside ) or at a greater distance (aircraft taxiing or taking off). Further research is needed to clarify how strong the impact would be at a greater distance from an aircraft engine

Read full article in ScienceDaily

• Particulate matter from aircraft engines affects airways

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The layout of the Irish Air Corps base at Casement Aerodrome ensures that aircraft exhaust gasses are blown over populated sections of the airbase when winds are from the south, south east or south west. This includes hangars, offices, workshops and living in accommodation such as the apprentice hostel and married quarters. Calm weather also creates conditions where exhaust gasses linger in higher concentrations.

This results in all Irish Air Corps personnel (commissioned, enlisted, civilian & family) being exposed to emissions from idling aircraft engines, emissions that are known to cause harm.

In the mid 1990s a study of air pollution adjacent to the ramp area at Baldonnel was commissioned. This report relating to this study has gone missing. 

• Anecdotal evidence suggests increased prevalence of occupational asthma & adult onset asthma amongst serving & former personnel who served in Baldonnel or Gormanston aerodromes. 
• Older gas turbine engines produce dirtier exhaust gasses.
• Idling gas turbine engines produce dirtier exhaust gasses.

Below are some of the gas turbine powered Air Corps aircraft that were powered by elderly engine designs.

Aircraft	Retired	Engine Family	First Run
Alouette III	2007	Turbomeca Artouste	1947
Fouga Magister	1999	Turbomeca Marboré	1951
Gazelle	2005	Turbomeca Astazou	1957
King Air 200	2009	Pratt & Whitney Canada PT6	1960
Dauphin II	2005	Turbomeca Arriel	1974