Study ID

Time point

Data

Direction over time[2] (↓ decline; ↔ equivocal; ↑ increase)

Czoli 2019

1 week

Compared to dual use (baseline):

1-HOP EC -31%; tobacco cigarette +23%

NNAL EC -30%; tobacco cigarette +8%

↓ 1-HOP

↓ NNAL

Goniewicz 2017

2 weeks

1-Hydroxyfluorene, baseline mean: 1414; week 2 mean: 592
1-Hydroxyphenanthrene, baseline mean: 488; week 2 mean: 584
1-Hydroxypyrene, baseline mean: 778; week 2 mean: 746
2-HPMA, baseline mean: 45; week 2 mean: 21
2-Hydroxyfluorene, baseline mean: 1029; week 2 mean: 842
2-Hydroxyphenanthrene, baseline mean: 655; week 2 mean: 968
2-Naphthol, baseline mean: 24; week 2 mean: 19
3-, 4-Hydroxyphenanthrenes, baseline mean: 1314; week 2 mean: 1410
3-HPMA, baseline mean: 937; week 2 mean: 410
3-Hydroxyfluorene, baseline mean: 679; week 2 mean: 451
AAMA, baseline mean: 254; week 2 mean: 110
CNEMA, baseline mean: 212; week 2 mean: 45
HEMA, baseline mean: 3821; week 2 mean: 1480
HPMMA, baseline mean: 1857; week 2 mean: 616
MHBMA, baseline mean: 1912; week 2 mean: 305
SPMA, baseline mean: 792; week 2 mean: 188

↓ 1-Hydroxyfluorene

↑ 1-Hydroxyphenanthrene

↓ 1-Hydroxypyrene

↓ 2-HPMA

↓ 2-Hydroxyfluorene

↑ 2-Hydroxyphenanthrene

↓ 2-Naphthol

↑ 3-, 4-Hydroxyphenanthrenes

↓ 3-HPMA

↓ 3-Hydroxyfluorene

↓ AAMA

↓ CNEMA

↓ HEMA

↓ HPMMA

↓ MHBMA

↓ SPMA

Hickling 2019

6 weeks

3HPMA (ng/ml), baseline mean: 2438.25; week 6 mean: 1180.75
Formic Acid, baseline mean: 6.6375; week 6 mean: 7.775

↓ 3-HPMA

↑ Formic acid

Ikonomidis 2020b

1 month

“…reduction of MDA (1.22 ± 0.1 vs 1.09 ± 0.1 μmol/L, P = 0.03)” in EC group. No change reported in cig group

↓MDA

McRobbie 2015

4 weeks

Of the 33 people that completed four-week follow-up, 16 were EC users only, and 17 were dual users. Both groups showed a significant decrease in 3-HMPA in ng/mg creatinine (EC users: 1623 (SD 850) to 343 (SD 178), P < 0.001; Dual users: 2443 (SD 1105) to 969 (SD 807), P < 0.001).

↓3-HMPA

Morris 2022*

9 days

“All BoE, except for nicotine equivalents, demonstrated statistically significant reductions from baseline levels (ranging from 72 to 97%).” No information provided on differences between study conditions.

↓NNAL

↓ 3-HPMA

↓ S-PMA

↓ CEMA

↓ HEMA

↓ 3-HMPMA

↓ MHBMA

↓ o-tol

↓ 1-AN

↓ 2-AN

↓ NNN

↓ 1-OHP

↓ 3-OH B[a]P

Pratt 2022

8 weeks

Nicotine EC v no intervention comparison. “NNAL decreased more over time in the e-cigarette group. Closer examination of the longitudinal differences in NNAL revealed that the e-cigarette group had significantly lower NNAL at 4 weeks (estimate=0.54; se=0.23; t=2.37;p<.02), but the group difference was attenuated at 8 weeks (estimate=0.42; se=0.23; t=1.83; p<.07)”

↓ NNAL

Pulvers 2018

4 weeks

“Statistically significant differences in log-transformed NNAL levels (mean difference = 0.35, 95% CI = 0.09–0.69, p < .01). Of the eight VOCs measured, there were two significant decreases in log-transformed values of the benzene metabolite, PMA (mean differences = 0.57, 95%CI = 0.12–1.03, p = .01), and the acrylonitrile metabolite, CNEMA (mean differences = 0.60, 95%CI = 0.25–0.96, p = .001).” See paper for crude data on all outcomes.

↓ NNAL

↓ PMA

↓ HEMA

↑ MMA

↓ CNEMA

↓ 3-HPMA

↓ 2-HPMA

↓ AAMA

↓ HPMMA