What makes kerosene so toxic
Toxic air from aircraft turbines
According to the World Health Organization (WHO), seven million people worldwide die each year as a result of air pollution. For around 20 years, studies have shown that fine dust particles in the air can be harmful to health. In addition to the sources of fine dust that have already been examined, such as heating, industry and road traffic, exhaust gases from aircraft turbines are also gaining in importance in the course of increasing demand in air traffic.
The primary solid particles emitted directly from the source have the greatest effects on people in the immediate vicinity of a source. However, the toxicity of solid particles from aircraft turbines is still largely unexplored.
Now a multidisciplinary team led by lung researcher Marianne Geiser from the Institute of Anatomy at the University of Bern has shown that primary soot particles from kerosene combustion in aircraft turbines can also damage lung cells directly and trigger inflammatory reactions if the solid particles - as simulated in the experiment - enter directly into the be inhaled near the engine.
The researchers are showing for the first time that the damaging effects also depend on the operating status of the turbines, the composition of the fuel and the structure of the generated particles. This is why research into particulate matter caused by air traffic is important for the further development of environmental standards in aviation.
Particles in aircraft turbine emissions are usually ultra-fine, i.e. smaller than 100 nanometers. In comparison, a human hair has a diameter of around 80,000 nanometers. When inhaled, these nanoparticles - like those from other combustion sources - are largely deposited in the respiratory tract.
When the immune system weakens
In healthy people, the well-developed immune system in the lungs normally ensures that the deposited particles are rendered harmless and removed from the lungs as quickly as possible. However, if inhaled particles can overcome this defense system due to their structure or physico-chemical properties, there is a risk that the lung tissue will be irreparably damaged. This process, which the researchers are familiar with from previous experiments with particle emissions from gasoline and diesel engines, has now also been demonstrated for particle emissions from aircraft engines.
The cell cultures in the laboratory showed increased damage to the cell membranes and oxidative stress. This causes cells to age faster and can be a trigger for cancer or diseases of the immune system. The particles were found to be harmful to different degrees, depending on the turbine thrust and type of fuel: The highest values were measured for conventional fuel when idling and for biofuel when climbing. These results were surprising. Especially in the tests with conventional kerosene and with full engine power - comparable with take-off and climb - the response of the cells was smaller than expected.
Very small particles
"These results can in part be explained by the very small dimensions and structure of these particles," says Anthi Liati, who researched nanostructures of combustion aerosols at Empa and was involved in the study. In addition, after exposure to biofuel, the cells reacted by increasing the release of inflammatory mediators, which are of central importance for our body's defenses. "These reactions reduce the ability of the airway cells to react appropriately to a subsequent viral or bacterial attack," explains Marianne Geiser. (red, May 24, 2019)
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