Methylglyoxal and Glyoxal in High-Puff Disposable Electronic Cigarette Liquids: Unexpected Accumulation and Enhanced...

Despite concerns regarding the potential health risks associated with EC use, their design, puff count, and e-liquid formulations have continued to evolve. Aldehydes are a key class of thermal degradation byproducts generated during the vaporization of EC fluids. This study tested the hypothesis that aldehyde concentrations would be elevated in used ECs with high puff numbers. Devices from multiple brands were analyzed to assess the impact of extended use on aldehyde formation. E-fluids were extracted from field-collected and user-donated devices and analyzed using gas chromatography/mass spectrometry to quantify 178 flavor chemicals, two synthetic coolants, nicotine, solvents, and aldehydes (methylglyoxal (MGO), glyoxal (GO), formaldehyde, acetaldehyde, acrolein, glyceraldehyde, dihydroxyacetone, propanal, and 5-hydroxymethylfurfural). Pulmonary cells were exposed to MGO and acetaldehyde in submerged cultures and at the air-liquid interface, and their toxic effects were analyzed in multiple assays. E-fluid consumption averaged 77% in ElfBar, 58% in FLUM, and 42% in "Other Brands", with chemical profiles varying significantly across brands and collection groups. Total flavor chemical concentrations averaged 34 mg/mL ± 21.6 for ElfBar and 9.7 mg/mL ± 7.9 for FLUM, and these concentrations were significantly reduced in vaped fluids. MGO, GO, and formaldehyde concentrations increased significantly in vaped fluids, while acetaldehyde and acrolein both decreased. Glyceraldehyde and dihydroxyacetone were detected only in vaped fluids and were generally elevated in ElfBar compared to FLUM products. MGO and acetaldehyde significantly disrupted the morphology of BEAS-2B cells and increased superoxide production in a concentration-dependent manner. These findings underscore the potential for increases in fluid aldehyde concentration with high-puff number ECs and raise concerns about the inhalation of cytotoxic byproducts generated during puffing. Regulatory policies should consider the influence of puff count on aldehyde generation.