Carcinogens | Tobacco smoke (n=309) | Heat-not-burn emission (n=44) | E-cigarette vapour (n=44) | Nicotine inhaler (n=1) | ||
Compound | IARC type | OEHHA unit risk Uj (µg/m3)−1 | Mean concentration Ej (µg/mL) | Mean concentration Ej (µg/mL) | Mean concentration in first-generation and second-generation e-cigarettes Cj (µg/mL) | Mean concentration Cj (µg/mL) |
Acetaldehyde | 2B | 2.7×10−6 | 2.55×10−0 | 3.33×10−1 | 4.41×10−3 | 1.05×10−4 |
Formaldehyde | 1 | 6.0×10−6 | 1.54×10−1 | 1.06×10−2 | 8.07×10−3 | 1.90×10−4 |
Acrylonitrile | 2B | 2.9×10−4 | 4.59×10−2 | 2.96×10−4 | NR | NR |
Benzene | 1 | 2.9×10−5 | 1.57×10−1 | 9.32×10−4 | NR | NR |
1,3-Butadiene | 1 | 1.7×10−4 | 1.83×10−1 | 3.94×10−4 | NR | NR |
2-Amino-naphthalene | 1 | 5.14×10−4 | 4.13×10−5 | 4.82×10−8 | NR | NR |
4-Amino-biphenyl | 1 | 6.0×10−3 | 8.68×10−6 | 1.80×10−8 | NR | NR |
Benzo[a]pyrene | 1 | 1.1×10−3 | 3.67×10−5 | 2.12×10−6 | NR | NR |
NNN | 1 | 4.0×10−4 | 4.63×10−4 | 2.57×10−5 | 1.94×10−7 | BDL |
NNK | 1 | 4.0×10−4 | 2.88×10−4 | 1.64×10−5 | 8.39×10−7 | BDL |
Cadmium | 1 | 4.2×10−3 | 1.99×10−4 | BDL | 1.01×10−5 | 9.52×10−7 |
Lead | 2B | 1.2×10−5 | 7.52×10−5 | 4.09×10−6 | 7.06×10−6 | 1.90×10−6 |
Chromium | 1 | 1.5×10−1 | BDL | BDL | NR | NR |
Nickel | 2B | 2.6×10−4 | BDL | BDL | 6.98×10−6 | 1.90×10−6 |
Arsenic | 1 | 3.3×10−3 | 2.20×10−5 | 2.14×10−6 | NR | NR |
Mean cancer potency ratio (equation 5) | 1.0 | 2.01×10−2 | 1.81×10−3 | 1.02×10−4 | ||
Mean lifetime cancer risk (equations 6 and 7) | Consumption | 15 cigarettes/day | 15 sticks/day | 30 L vapour/day | 30 L vapour/day | |
Risk | 2.4×10−2 | 5.7×10−4 | 9.5×10−5 | 8.9×10−6 | ||
Ratio to tobacco smoke | 1.0 | 0.024 | 0.004 | 0.0004 | ||
Ratio to nicotine inhaler | 2697 | 64 | 10.7 | 1.0 |
Average concentrations for e-cigarettes for first-generation and second-generation devices only (where identifiable). See text for sources of data. Concentrations in bold type represent compounds that contribute >5% of the modelled potency for a particular form of delivery.
BDL, below detection limit; IARC, International Agency for Research on Cancer; NR, not reported; NNN, N′-nitrosonornicotine; NNK, 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone; OEHHA, Office of Environmental Health Hazard Assessment.