Multiple peer-reviewed studies have analyzed the chemical composition of secondhand vape aerosol. Here's what the science shows, with evidence confidence ratings:
| Compound | Concentration in Indoor Air | vs Secondhand Smoke | Evidence Level |
|---|---|---|---|
| Nicotine | 0.1-3.3 ug/m3 | 10-50x lower | HIGH |
| PM2.5 (fine particles) | 22-160 ug/m3 (during active vaping) | 5-10x lower | HIGH |
| Ultrafine particles (PM0.1) | 10,000-100,000 particles/cm3 | Comparable (both produce UFPs) | HIGH |
| Formaldehyde | 0.02-0.15 ug/m3 | 20-50x lower | MODERATE |
| Acrolein | 0.005-0.03 ug/m3 | 10-30x lower | MODERATE |
| Benzene | Below detection in most studies | 100x+ lower | MODERATE |
| Heavy metals (Pb, Ni, Cr) | Trace levels (from coil degradation) | Lower but present | LOW |
| Carbon monoxide (CO) | Not detected | Absent (no combustion) | HIGH |
| Propylene glycol | 0.5-5.0 mg/m3 | Not present in smoke | HIGH |
| Tobacco-specific nitrosamines (TSNAs) | Not detected | Absent (no tobacco) | HIGH |
Composition verdict: Secondhand vape aerosol contains nicotine, particulate matter, VOCs, and trace metals — but at concentrations 10-100x lower than secondhand smoke. The absence of carbon monoxide and tobacco-specific nitrosamines is the most significant difference. For a full breakdown of e-liquid chemistry, see our vape juice ingredients science guide.
