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Dry air alters salt and water balance in the upper airways and increases the risks of COVID-19 among other respiratory diseases. We explored whether such upper airway variations in salt and water balance might alter respiratory droplet generation and potentially contribute to observed impacts of airway hydration on respiratory disease. In a randomized 4-arm study of 21 healthy human subjects we found that the breathing of humid air, the wearing of cotton masks, and the delivery of (sodium, calcium, and magnesium chloride) salt droplets sized to deposit in the nose, trachea, and main bronchi similarly reduce the exhalation of respiratory droplets by approximately 50% ($P$ < 0.05) within 10 minutes following hydration. Respiratory droplet generation returns to relatively high baseline levels within 60–90 minutes on return to dry air in all cases other than on exposure to divalent (calcium and magnesium) salts, where suppression continues for 4–5 hours. We also found via a preliminary ecological regression analysis of COVID-19 cases in the United States between January 2020 and March 2021 that exposure to elevated airborne salt on (Gulf and Pacific) US coastlines appears to suppress by approximately 25%–30% ($P$ < 0.05) COVID-19 incidence and deaths per capita relative to inland counties — accounting for ten potential confounding environmental, physiological, and behavioral variables including humidity. We conclude that the hydration of the upper airways by exposure to humidity, the wearing of masks, or the breathing of airborne salts that deposit in the upper airways diminish respiratory droplet generation and may reduce the risks of COVID-19 incidence and symptoms.

In the present study, salt granules were dried in fluidized bed dryer and suitable technologic parameters of drying operation were obtained. The results could direct design of industrial dryer. Besides, the air distributing structure of fluidized bed dryer was studied and its pressure drop curve was measured. The result indicated that one layer intertexture net below the air distributing board could obtain good effect of air distributing without increase of pressure drop. This kind of structure could also prevent the material from leaking availably.

The objective of the present study was to investigate the effects of various parameters, i.e., concentration of salt solution (2, 3, 4% (w/v)), boiling time (3, 5, 7 minutes) and drying air temperature (80, 100, 120°C) on the kinetics of drying and various quality attributes of shrimp, namely, color, texture, shrinkage and rehydration ability, during drying in a jet-spouted bed dryer. Small shrimp (350-360 shrimp/kg) was boiled and then dried until its moisture content was around 25% (d.b.). It was found that the color changes, toughness and shrinkage of shrimp increased while the rehydration ability decreased with an increase in the concentration of salt solution and boiling time.