Aircraft engine emissions grow more toxic over time, Basel team finds

Simulating atmospheric aging in the lab

Tiny particulate matter with diameters in the nanometer range forms during fuel combustion. These particles stay suspended in the air for hours or days before humans inhale them.

Once inside the human body, the matter penetrates deep into the respiratory tract to trigger oxidative stress. This stress can lead to inflammation and, in the long term, can lead to cardiovascular or respiratory diseases. Scientists measure this harmful capacity as oxidative potential.

A research team led by Professor Markus Kalberer set out to track how this oxidative potential and toxicity evolve over time. They tested emissions from a small aircraft jet engine and a marine diesel engine, using a photochemical reactor to simulate atmospheric aging processes across a timeline of one to 12 days.

The Basel instrument that exposed the split

Known as the Online Oxidative Potential Ascorbic Acid Instrument, or OOPAAI, the device revealed a distinct split between the two transportation sources.

While the health-related properties of marine engine emissions remained substantially stable throughout the testing period, the oxidative potential of aircraft emissions increased significantly as the particles aged.

This transformation stems directly from chemical changes. The particles react with air components under prolonged sunlight exposure over the course of their suspension in the atmosphere.

Regulatory failures contribute to millions of premature deaths

The findings indicate that current regulatory frameworks, including the Swiss Air Protection Ordinance, fail to account adequately for the most toxic sources of fine particulate matter and their evolving properties.

The stakes are high. The World Health Organization estimates that high concentrations of atmospheric particulate matter contribute to more than 7 million premature deaths globally each year.