Table 1

Unit risks and average concentrations for IARC type 1 and 2 carcinogens measured in tobacco smoke and other forms of nicotine delivery

CarcinogensTobacco smoke (n=309)Heat-not-burn emission (n=44)E-cigarette vapour (n=44)Nicotine inhaler (n=1)
CompoundIARC typeOEHHA 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)
Acetaldehyde2B2.7×10−6 2.55×10−0  3.33×10−1 4.41×10−3 1.05×10−4
Formaldehyde16.0×10−6 1.54×10−1 1.06×10−2 8.07×10−3 1.90×10−4
Acrylonitrile2B2.9×10−4 4.59×10−2 2.96×10−4 NRNR
Benzene12.9×10−5 1.57×10−1 9.32×10−4 NRNR
1,3-Butadiene11.7×10−4 1.83×10−1 3.94×10−4 NRNR
2-Amino-naphthalene15.14×10−4 4.13×10−5 4.82×10−8 NRNR
4-Amino-biphenyl16.0×10−3 8.68×10−6 1.80×10−8 NRNR
Benzo[a]pyrene11.1×10−3 3.67×10−5 2.12×10−6 NRNR
NNN14.0×10−4 4.63×10−4 2.57×10−5 1.94×10−7 BDL
NNK14.0×10−4 2.88×10−4 1.64×10−5 8.39×10−7 BDL
Cadmium14.2×10−3 1.99×10−4 BDL 1.01×10−5 9.52×10−7
Lead2B1.2×10−5 7.52×10−5 4.09×10−6 7.06×10−6 1.90×10−6
Chromium11.5×10−1 BDLBDLNRNR
Nickel2B2.6×10−4 BDLBDL6.98×10−6 1.90×10−6
Arsenic13.3×10−3 2.20×10−5 2.14×10−6 NRNR
Mean cancer potency ratio (equation 5)1.02.01×10−2 1.81×10−3 1.02×10−4
Mean lifetime cancer risk (equations 6 and 7)Consumption15 cigarettes/day15 sticks/day30 L vapour/day30 L vapour/day
Risk2.4×10−2 5.7×10−4 9.5×10−5 8.9×10−6
Ratio to tobacco smoke1.00.0240.0040.0004
Ratio to nicotine inhaler26976410.71.0
  • 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.