Ultrasonic Humidifiers - An Underrated Route for Inhalation Exposure? 

Humans living in contemporary societies spend over 90% of their time indoors. Yet, factors affecting indoor air quality have not been investigated in an exhaustive manner. In particular, the impacts of many indoor pollutant sources are not properly recognized. A major reason that existing literature often neglects major indoor sources is the lack of a means of monitoring indoor air quality in the actual living environment. Residents living in the Canadian Northern Prairies often use ultrasonic humidifiers to combat the cold and dry winter. Ultrasonic humidifiers can give rise to fine particulate matter (PM2.5), a benchmark pollutant that can induce a variety of health complications. In this presentation, I will introduce a couple of studies conducted by my research group, investigating PM2.5 emitted from the use of ultrasonic humidifiers. In addition to laboratory studies, we have employed novel low-cost air quality sensors to investigate the transport of humidifier-generated PM2.5 in an experimental home. Further, the impact of humidifier use on indoor air quality in university student residences was also investigated. Our study showed that the use of a single ultrasonic humidifier charged with tap water can give rise to PM2.5 levels equivalent to a polluted city. The composition of the PM2.5 mirrors that of the water used. Overall, our study shows that ultrasonic humidifiers can be an underrated route for inhalation exposure to contaminants that would be normally found in water. This inhalation exposure pathway can be particularly relevant to people living in the Northern Canadian Prairie.