Cognitive endpoints in aircrew radiation protection: a combined radiation and cabin air-quality framework, the Closed-Loop Life Support System (CLLSS) concept, and the “Shadow Zone”

Occupational radiation protection for aircrew is based on stochastic cancer risk, and aerospace life-support certification, primarily the Environmental Control and Life Support System (ECLSS) framework, is built around acute physiological survival thresholds. Both frameworks fail to capture two subtler and cumulative neurocognitive risk pathways suggested by the existing literature: (1) a radiation-induced cognitive tipping point linking cumulative low-dose radiation to long-term neurophysiological alterations, and (2) a “Shadow Zone” of subclinical cognitive degradation in which cabin atmospheric fluctuations (CO2, ozone, trace contaminants) act as environmental co-stressors that compound ionizing radiation risks to impair crew performance. In this Opinion article, we synthesize emerging evidence and advance the testable hypothesis that these cosmic radiation risks and environmental co-stressors interact through shared downstream neurophysiological markers, positioning radiological protection as the primary operational framework. On this basis, we introduce the Closed-Loop Life Support System (CLLSS) concept, a conceptual discussion framework designed to stimulate dialogue on shifting life-support certification logic from simple physiological 'survival' to operational 'performance.' Finally, we propose a unified experimental protocol that combines EEG acquisition with real-time atmospheric and cosmic radiation monitoring, inviting critique from the radiation protection community ahead of upcoming multi-site collaborative empirical validation.