Influence of weather and seasonal variations in temperature and humidity on supersaturation and enhanced deposition of submicron aerosols in the human respiratory tract

In this review, all available data on the effects of supersaturation in human airways were summarized and analysed, and the most critical parameters identified. The analysis shows the boundary conditions for increased supersaturation in airways: inhalation of cold air of T < 22 degrees C or cool saturated air of T < 25-27 degrees C. Thus, it was summarized for the first time that conditions during rainy weather or cold seasons in a temperate climate and rainy seasons in subtropical and tropical climates can induce supersaturated conditions in human airways. It was shown that under such conditions a total deposition of 300 nm particles may increase from similar to 13% (when the supersaturation is not taken into account) to similar to 90% due to enhanced condensational growth. It was found that such unusually high underestimation of deposition efficiency may be typical for most classical studies and approaches. An important observation was made for the first time: weather conditions which are favorable for enhanced deposition of submicron aerosols (and infectious aerosols) due to supersaturation in human airways may be connected with increased respiratory symptoms of asthma and chronic obstructive pulmonary disease (COPD) and two different patterns of seasonality of respiratory infections and influenza. This is one of the main aspects of this work that needs to be studied in the future. The primary implication of the results of this review is that weather patterns can play a significantly more important role in the deposition of ambient submicron aerosols in human airways than previously assumed.