Supersaturation and nasal anatomy: Correcting critical gaps in aerosol dosimetry for equitable air pollution risk assessment

Abstract

Current inhaled aerosol dosimetry methods, used to assess air pollution risks, may significantly underestimate deposited particle doses by neglecting two key factors in the upper airways: anatomical variability and water vapor supersaturation (RH > 100 %). While personalized dosimetry accounting for anatomical differences is a longer-term research goal, the influence of supersaturation—triggered by some scenarios like breathing cold (<15–20 °C) or saturated air (<27 °C)—demands urgent attention.

Theoretical models suggest that supersaturation can induce condensational growth in particles >10–20 nm, leading to rapid, orders-of-magnitude size increases to supermicrometer dimensions, thereby significantly altering deposition patterns in the respiratory tract. This results in higher dose estimates than those predicted by classical models, which focus primarily on hygroscopic growth under RH < 100 %.

A rough analogy to engineered systems like condensation particle counters illustrates how even non-hygroscopic and hydrophobic particles, traditionally considered inert, can undergo substantial condensational growth in supersaturated conditions. A key unanswered question remains: how will such particles behave within the complex environment of real airways under supersaturating conditions?

Therefore, integrating supersaturation and individual anatomical factors into air pollution risk assessments is crucial for improving public health strategies, particularly for vulnerable populations exposed to relevant climatic conditions.