"Vaping has been endorsed by health experts after the first long-term study of its effects in ex-smokers," ITV News reports.

E-cigarettes contain nicotine but not many of the harmful substances produced by smoking tobacco, such as tar or carbon monoxide. However, there has been debate about exactly how safe their long-term use is.

The study, involving 181 smokers or ex-smokers, has been described as "landmark" as it is thought to be the first (or at least one of the first) looking at long-term vaping outcomes in "real world" users. Previous studies of this kind have mainly relied on laboratory equipment, or animal research, to estimate the long-term effects of e-cigarettes.

The volunteers completed questionnaires and provided breath, saliva and urine samples. The researchers found significantly lower levels of toxic chemicals and cancer-causing substances (carcinogens) in the samples of those of former smokers who had been using e-cigarettes or nicotine replacement therapy (NRT) compared to current smokers.

Another noted result is that current smokers who may be trying to reduce their risk of harm by switching between e-cigarettes and normal cigarettes may be saving money, but doing little for their health. "Combination users" still had very high levels of toxins and carcinogens

This study provides evidence that e-cigarettes and NRT can reduce harm to smokers by reducing exposure to toxic chemicals. The evidence would also seem to support Public Health England’s 2015 report that “E-cigarettes are 95% less harmful than tobacco”.

Where did the story come from?

The study was carried out by researchers from a number of institutions, including University College London, and the Roswell Park Cancer Institute and Centers for Disease Control and Prevention (both in the US). Funding was provided by Cancer Research UK.

The study was published in the peer-reviewed journal: Annals of Internal Medicine.

There has been much discussion over the benefits of vaping over conventional smoking methods and this is the first long-term study assessing these effects. In general the findings have been reported accurately in the UK media; however none of the limitations, as described by the researchers themselves, have been mentioned.

The Daily Mirror included a quote from professor Kevin Fenton, national director of health and wellbeing at Public Health England, who added: "This study provides further evidence that switching to e-cigarettes can significantly reduce harm to smokers, with greatly reduced exposure to carcinogens and toxins."

What kind of research was this?

This was a cross-sectional study that drew comparisons on exposure to nicotine and other tobacco-related toxins and carcinogens in the following groups:

  • current cigarette smokers who only smoked cigarettes
  • current cigarette smokers who also used e-cigarettes
  • current cigarette smokers who also use other forms of nicotine replacement therapies (NRT), such as skin patches or gum
  • former smokers who were now using only e-cigarettes
  • former smokers who were now using only NRT

Limitations to this study design include the possibility of recall bias as participants provide information about their smoking habits through a questionnaire. There is also the possibility of residual confounding from other unmeasured factors so findings may not be entirely accurate.

What did the research involve?

The researchers recruited participants from Greater London by placing advertisements in newspapers and online, posters in pharmacies and though marketing companies.

To be able to join the study participants had to be either:

  • a current smoker, who has smoked an average of five or more cigarettes per day for at least six months
  • a former smoker, who has stopped using tobacco products for at least six months

Researchers aimed to assess the effects of long-term use of non-combustible nicotine delivery – that is NRT or e-cigarettes – for a minimum of six months. They compared:

  • current smokers of cigarettes only
  • combination smokers – cigarette smokers also using an e-cigarette or NRT
  • former smokers using e-cigarettes-only or NRT-only

Participants were asked to visit a laboratory after not eating, drinking, or using combustible cigarettes or other nicotine products for an hour before their visit. During the appointment the participants filled in a questionnaire including questions on sociodemographic and smoking characteristics.

Breath, saliva, and urine samples were taken, which were assessed for levels of nicotine and other carcinogenic or toxic chemicals.

This included tobacco specific nitrosamines (TSNAs), which are one of the most important carcinogens in tobacco formed from nicotine. They also looked at a class of toxins called volatile organic compounds (VOCs) such as acrylamide and cyanide-releasing acrylonitrile. 

Analyses were adjusted for smoking history, sociodemographic variables, physical health and subjective wellbeing.

What were the basic results?

A total of 181 participants were included in the study.

Significantly lower levels of cancer causing chemicals, TSNAs and VOCs were found in samples from former smokers using e-cigarettes only or NRT only, compared with current smokers. Their levels were lower than both those who smoked cigarettes only, or smokers using either e-cigarette or NRT alongside cigarettes.

Former smokers using e-cigarettes only had significantly lower levels of the toxic chemical NNAL (a by-product of exposure to TSNAs) than all other groups. This was equivalent to a 97% reduction compared with the levels of cigarette-only users.

Current smokers of combustible cigarettes only, and current smokers also using NRT or e–cigarettes, had similar levels of the tobacco-related toxins and carcinogens.

Looking at nicotine, levels in urine samples were broadly similar across groups. There was though some variation in salvia levels, with e-cigarette-only users, and those using NRT while continuing to smoke cigarettes had slightly lower nicotine levels than other groups.  

How did the researchers interpret the results?

The researchers conclude: "Former smokers with long-term e-cigarette-only or NRT-only use may obtain roughly similar levels of nicotine compared with smokers of combustible cigarettes only, but results varied. Long-term NRT-only and e-cigarette-only use, but not dual use of NRTs or e-cigarettes with combustible cigarettes, is associated with substantially reduced levels of measured carcinogens and toxins relative to smoking only combustible cigarettes".


This cross-sectional study aimed to assess whether there are differences in levels of nicotine and toxic chemicals in cigarette smokers, and former or current smokers who are also long-term users of e-cigarettes or NRT.

E-cigarettes are designed for users to inhale nicotine without most of the harmful effects of smoking. There has been much discussion over the benefits of vaping over conventional smoking methods and this is the first long-term study assessing these effects.

The main findings are not that surprising – former smokers who have now switched to using e-cigarettes or NRT only have significantly lower levels of toxins than those who continue to smoke regular cigarettes.

However, the study has limitations.

  • while attempts were made to control for confounders, it is possible that other unmeasured factors are influencing the results
  • this was a self-selected sample and therefore findings may not be generalisable to the whole population of former or current smokers
  • indirect exposure to cigarette smoking could not be accounted for in this research
  • the study is not able to assess the comparative effectiveness of NRT or e-cigarettes as aids to smoking cessation

The findings of this study do appear to reassure that use of e-cigarettes and nicotine replacement therapy – while continuing to provide nicotine – can reduce exposure to toxic chemicals that can lead to cancer in cigarette smokers.

However, this is only if you completely stop smoking – using e-cigarettes or NRT while continuing to smoke won’t help.

Smokers who want to stop smoking can get help from NHS stop smoking services, which can reduce their risk of smoking-related disease and death.

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