Autoxidation of Glycols Used in Inhalable Daily Products: Implications to the Use of Artificial Fogs and E-cigarettes

The use of glycols is seen in various industries and occupations. In past decades, health implications from inhalable glycols have gained public attention. By impacting indoor air quality, inhalable glycols may cause adverse health effects, especially for workers in different occupations receiving frequent exposure. Our previous work highlighted the rapid accumulation of formaldehyde and glycolaldehyde in fog juice, thus proposing the occurrence of glycol autoxidation. However, the fundamentals of glycol autoxidation remained unclear and unexplored. Our goal is to investigate the autoxidation of common glycols during indoor storage. Carbonyls were quantified using liquid chromatography-mass spectrometry (LC-MS), and peroxides from autoxidation were monitored via iodometry and UV-Vis spectrometry. The impact of external factors was also investigated, such as the water mixing ratio, and antioxidants (Vitamin C). Via weekly monitoring, a rapid formation of aldehydes in many glycols was observed, such as E-cigarette juice and triethylene glycol (TEG). Occurrence of autoxidation was confirmed by the rise of the total peroxide concentration. Additionally, we highlighted the dependence of carbonyl formation rate on the TEG-water mixing ratio, demonstrating the complicated role water plays in glycol autoxidation. We have also tested the effectiveness of Vitamin C, with suggestions for minimizing the formation of toxic carbonyls in consumer products.