For an ultrasonic humidifier, 90% of the aerosols formed are in the respirable range. This suggests that such humidifiers may have negative effects on human health depending on the quality of the water source. Researchers analyzed five drinking water samples of different quality. The study published in Environmental Engineering Science has revealed that ultrasonic humidifiers aerosolize and emit dissolved contaminants that can be inhaled, including minerals and metals.
In the study titled 'Emission of Inhalable Dissolved Drinking Water Constituents by Ultrasonic Humidifiers', Amanda Sain and Andrea Dietrich, Virginia Polytechnic and State University (Blacksburg), described the results of testing five different water quality types in ultrasonic humidifiers. The drinking water samples used to fill the humidifiers ranged from low to high levels of total dissolved solids (a common measure of mineral content), hardness, and iron content. The researchers evaluated the aerosols emitted for the range of particle sizes and for evidence of dissolved metal and nonmetal constituents.
‘Ultrasonic humidifiers aerosolize and emit dissolved contaminants that can be inhaled, including minerals and metals. Thus, the quality of drinking water that is used to fill the humidifiers may have negative effects on human health.’
Domenico Grasso, Editor-in-Chief of Environmental Engineering Science
and Provost, University of Delaware, said, "This is a very interesting study that identifies another path of human uptake of constituents in drinking water - that of inhalation. Health consequences appear to be dependent on the nature of the water quality used in the humidifiers."