A proposed method to cool the planet by spraying sulphur near the poles could put commercial airline passengers and crew at risk of breathing hazardous levels of sulphuric acid. The technique would use modified Boeing 777 aircraft on polar routes. Researchers warn that concentrations could exceed safety limits set by the European Union.
The approach aims to reflect sunlight and reduce global temperatures by 0.6 to 1.0°C through injections of 12 million tonnes of sulphur dioxide annually. Simulations place the releases near the North Pole from March to June and the South Pole from September to December. Polar flight paths connecting Asia and North America would intersect the resulting plumes.
Alan Robock of Rutgers University noted that passenger aircraft fly at the same altitudes where the sulphur would be deposited. Models show cabin concentrations could reach more than 50 micrograms per cubic metre in some areas, above the European Union hazardous threshold.
Exposure to the acid can irritate the throat, inflame lungs and trigger asthma attacks. Wake Smith of Harvard University said any deployment remains many decades away, allowing time for improved cabin air filters. Daniele Visioni of Cornell University described the findings as preliminary but not a dealbreaker for the concept.
