The main chemical in some vaping aerosols that has been linked to “popcorn lung” is diacetyl (also called 2,3‑butanedione).

What is “popcorn lung”?

  • “Popcorn lung” is the nickname for bronchiolitis obliterans, a serious and irreversible disease that scars and narrows the smallest airways in the lungs.
  • It was first identified in workers at microwave popcorn factories who inhaled heated butter‑flavoring fumes over time.

The key chemical in vapes

  • Diacetyl is a butter‑flavoring chemical that is safe to eat in food but hazardous when inhaled as a vapor or aerosol.
  • Some e‑cigarette liquids, especially sweet or buttery flavors, have been found to contain diacetyl, which can be carried in the aerosol users inhale.

Other related chemicals

  • Substitutes for diacetyl, such as acetoin and 2,3‑pentanedione, may also damage small airways in similar ways when inhaled.
  • Other inhaled toxic chemicals found in some vapors (like formaldehyde and acetaldehyde) can also injure the lungs and are discussed as additional contributors to popcorn lung–type damage.

Quick safety takeaway

  • The specific answer to “which chemical in vaping aerosol can cause popcorn lung?” is diacetyl.
  • Because flavoring chemicals can change when heated and inhaled, health agencies warn that no inhaled level of diacetyl or its close substitutes is known to be completely safe for the lungs.

Information gathered from public forums or data available on the internet and portrayed here.