Airway pH (logarithm of the inverse concentration of H+) is central to the physiologic function and cellular biology of the airway. Even a very mild airway acid (pH reduction) insult triggers cough, bronchospasm, and neurogenic inflammation. The pH reduction is the main feature of inflammatory respiratory diseases and plays a role in bronchoconstriction, impaired ciliary function, increased airway mucus viscosity, and in turn, can enhance inflammation and airway dysfunction.

In this conceptual research, the hypothesis was put forward that short-term supersaturation effects in the airways induced by some specific weather and climatic conditions can induce pH reduction in the upper airways.

Available data were summarized and analysed, and preliminary analysis and assessment of the physicochemical processes occurring during supersaturation and liquefication of water vapor in the respiratory tract were conduct.

It was found that liquefication of water vapor under supersaturated conditions in the airways can lead to the formation of liquid droplets with a high concentration of carbon dioxide (CO2) which hydrated to carbonic acid, which subsequently dissociates to H+ and HCO3-. Therefore, it was shown that CO2 can lead to substantial acidification (pH reduction) of the formed droplets. It was found that the pH of condensate can reach of 5.5-6.5. Thus, it was found that due to the condensation under supersaturated conditions the normal pH (6.9-9.0) in the airways may become acidic.

The primary implication of the results of this conceptual research is that weather conditions can play a significantly more important role in the airway acidification and as a consequence in the negative respiratory health impact than previously assumed.