Scientists have found hidden toxins in vape liquids

Researchers from the University of California at Riverside have come to this conclusion after studying chemical reactions when heating the main component of most vape liquids - propylene glycol.

According to the University of California - Riverside, vaping liquids produce two toxic substances - methylglyoxal and acetaldehyde. Both of these compounds are already known for their toxicity, but their effect on human lung cells when vapour is inhaled has not been studied sufficiently before.

The scientists used lab-grown cells of bronchial epithelium, the tissue lining the respiratory tract. The cells were exposed to realistic concentrations of both substances. The results showed that both toxins disrupted important cellular processes, but methylglyoxal was more dangerous even at lower doses.

It damaged mitochondria, the energy centres of the cell, and also weakened the cytoskeleton, which is responsible for the shape and strength of cells. According to Professor Prue Talbot, lead author of the study, such changes indicate cellular stress and may contribute to long-term lung damage from regular vaping.

Acetaldehyde, widely studied as a component of tobacco smoke, does occur in high amounts in vape vapour. However, the study found that methylglyoxal may be more toxic despite its lower concentration in vapour.

Of particular concern to scientists was the fact that lower wattage devices - generally considered safer - may emit more methylglyoxal. PhD student Man Wong, first author of the publication, said.

"Almost all e-cigarettes use propylene glycol," Wong said. - So it's important to understand how by-products are formed when heated and how they affect cells. This is critical for assessing the long-term harms of vaping."

Even short-term exposure to the identified substances led to malfunctions in genes responsible for energy production, DNA repair and maintaining cell structure. This explains why e-cigarettes, considered less harmful, may also be a risk factor for the respiratory system.

The authors hope their work will form the basis for further research and help in the development of safety regulations for vape products.

The study is published in Frontiers in Toxicology under the title Acetaldehyde and methylglyoxal: comparative analysis of toxic electronic cigarette degradation products in 3D and 2D exposure systems using human bronchial epithelial models (2025).