Polar SAI Simulations Show Cabin Sulphuric Acid Exceeding EU Hazardous Threshold on Asia-North America Routes

Researchers led by Alan Robock at Rutgers used output from prior stratospheric aerosol injection runs that released 6 million tonnes SO2 seasonally at each pole. They mapped the resulting sulphate plumes onto commercial polar routes flown by Boeing 777-class aircraft whose bleed-air systems draw directly from engine compressors. Peak plume segments produced cabin sulphuric acid levels above the EU 50 microgram threshold for hours, while average exposure remained near urban SO2 background values. The study flags repeated exposure for flight crews but does not quantify cumulative dose or synergistic effects with existing ozone and particulate loads at cruise altitude.

Mainstream coverage has focused on deployment feasibility and ignored occupational health standards already applied to cabin air. Cumulative exposure for pilots and cabin crew operating multiple polar rotations per month could approach thresholds linked to increased stroke risk and asthma exacerbation in occupational cohorts. Existing HEPA filters are not rated for sub-micron sulphate aerosols formed in the stratosphere, creating an unexamined retrofit requirement. Governance discussions on solar radiation management have likewise omitted liability frameworks for in-flight chemical exposure.

The next required step is coupled chemistry-transport modeling at aircraft scale combined with real-time cabin air sampling during dedicated test flights. Without these data, cost-benefit analyses of polar SAI remain incomplete on the health dimension.