Interventional breath analysis reveals oral microbial conversion of 1,2-Propanediol into Propanal and 1-Propanol

A controlled oral 1,2-propanediol challenge in 10 healthy volunteers rapidly and transiently increased exhaled propanal and 1-propanol, while nasal signals stayed stable.

• Why it matters: Breath VOC biomarkers can be confounded by sampling route, and prior work showed 1-propanol is enriched orally; this study tests whether oral metabolism drives route-specific changes.
• What they did: Volunteers rinsed with 0.1 mL 1,2-propanediol in ~50 mL water for ~30 s, then expectorated, with matched oral and nasal end-tidal breath collected before, immediately after, and at 15-min intervals; GC-IMS quantified propanal, 1-propanol, acetol, acetone, and isoprene.
• The result: Propanal and 1-propanol rose most immediately after administration and again at the second post-intervention measurement only in oral samples; acetone and isoprene showed no consistent route effects, and acetol increases were not reproducible due to analytical interference.

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