Geoengineering Could Fill Cabin Air with Sulphuric Acid
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- Alan Robock at Rutgers University published a study in Geophysical Research Letters finding that polar stratospheric geoengineering could push cabin sulphuric acid concentrations above 50 micrograms per cubic metre — the EU threshold for hazardous air.
- Robock's team modelled injecting 6 million tonnes of sulphur dioxide near the North Pole (March–June) and 6 million tonnes near the South Pole (September–December) at 13–15 km altitude, which atmospheric models suggest would cool Earth 0.6–1.0°C.
- The practical alternative uses upgraded Boeing 777s spraying sulphur near the poles, where the stratosphere dips to ~7 km, because equatorial injection at peak effectiveness would demand new aircraft reaching 20 km altitude — nearly double today's flight ceiling.
- Pilots and flight attendants on polar routes — like Asia–North America — face the highest cumulative exposure, with risks including respiratory irritation, tightened airways, increased stroke risk, and asthma attacks.
- Wake Smith at Harvard called the deployment timeline 'many decades away, if it ever happens,' arguing airlines would have time to upgrade cabin air filters to handle the predicted sulphur loads.
- Daniele Visioni at Cornell deemed the results 'interesting preliminary results, but definitely not anything that would be a dealbreaker,' arguing the larger risks lie elsewhere.
Why it matters: Flight crews on polar routes — like those connecting Asia to North America — would absorb the highest cumulative sulphuric acid exposure if polar geoengineering ever launches, with cabin air potentially exceeding the EU's 50 μg/m³ hazardous threshold. But the researchers themselves stress deployment is decades away, giving aviation decades to upgrade filtration before any passengers or crew are actually exposed.
