Smokers who started using e-cigarettes alongside cigarettes were exposed to lower levels of several tobacco-related carcinogens. However, their total nicotine intake did not decrease, according to a new US study.
Combining e-cigarettes with continued cigarette smoking – known as ‘dual use’ – is often described as a first step towards giving up smoking. At the same time, questions have been raised about the actual effect such use has on exposure to harmful substances.
In a new study, published in the journal Addiction, researchers have analysed data from just over 8,600 American smokers who took part in the national PATH study. The researchers compared people who switched from smoking cigarettes exclusively to combining cigarettes with e-cigarettes with those who continued to smoke cigarettes exclusively.
Lower levels of carcinogens
The results show that those who started using e-cigarettes alongside cigarettes had lower levels of two tobacco-related nitrosamines – NNAL and NNNT – in their urine. These substances are formed during the combustion of tobacco and are often used as biomarkers of exposure to carcinogens from cigarettes.
Compared with those who continued to smoke only cigarettes, levels of NNAL fell by around 13 per cent and levels of NNNT by around 10 per cent.
Nicotine intake increased slightly
At the same time, the researchers observed no reduction in total nicotine intake. On the contrary, levels of two established biomarkers of nicotine exposure increased by between 8 and 17 per cent among those who switched to dual use.
The researchers therefore conclude that switching to e-cigarettes as a complement to cigarettes appears to reduce exposure to certain harmful substances in tobacco smoke, but not exposure to nicotine.
The number of cigarettes smoked each day has an impact on
When the researchers grouped the participants according to how much they smoked before making the switch, the differences became clearer. The reduction in nitrosamines was mainly linked to people who initially smoked fewer than around 13 cigarettes a day. Among the heaviest smokers, the reduction was significantly smaller and not statistically significant.
The researchers emphasise that the findings are based on observational data and therefore cannot establish a direct causal link. At the same time, they argue that the findings reinforce the view that smokers who supplement their cigarettes with e-cigarettes can reduce their exposure to some of the most harmful substances produced by tobacco smoking, even if their nicotine intake remains the same.
Facts about the study
- Study: Longitudinal association between switching to dual use of cigarettes and e-cigarettes versus continued exclusive cigarette smoking and the intake of tobacco-specific nitrosamines and nicotine
- Published in: Addiction
- Participants: 8,688 adult smokers in the US PATH study
- Comparison: Continued cigarette smoking compared with switching to the combined use of cigarettes and e-cigarettes
- Key findings: Lower exposure to tobacco-related nitrosamines, but no reduction in nicotine intake.
