A new report warns that e-cigarettes may be linked to cancer. But critics say the conclusions are based on misinterpretations - and give a grossly misleading picture of both the absolute risks of vejp use and the relative risks compared to smoking.
“Misleading smokers in this way risks discouraging them from using e-cigarettes, which are one of the most effective methods available to help people quit smoking,” writes Peter Hajek, Professor of Clinical Psychology at Queen Mary University of London.
A new report on e-cigarettes and cancer risk is sparking debate. The researchers behind the report argue that vejpning, or e-cigarette use, can pose significant health risks - while critics say the conclusions are misleading and risk discouraging smokers from less harmful alternatives.
The report: chemical and biological effects
According to the authors of the report, the aerosol inhaled by e-cigarette users contains a complex mixture of substances.
“The aerosol inhaled by vejpare contains a complex mixture of chemicals, including nicotine and its breakdown products and vaporised metals.” according to the report's lead author Mr Bernard Stewart, Professor of Paediatrics at the University of New South Wales in Sydney, Australia.
Furthermore, he claims that aerosol exhibits almost all of the ten “key characteristics of carcinogens” identified by the World Health Organisation.
Linking chemicals to cancer
Mr Stewart also refers to biological measurements in users. According to the report, blood and urine samples from 1TP8 users show that the body absorbs substances linked to cancer. These include nicotine and its breakdown products, but also metals from heating components and organic substances from e-liquids.
“Blood and urine analysis from vejpers confirmed that they had absorbed chemicals from e-cigarettes that we know are linked to cancer. These studies showed that nicotine and its breakdown products were present in the body, including carcinogenic metals from the heating element and organic compounds from the vaporisation of e-liquids.” writes Bernard Stewart.
He also believes that vejpning affects the body's tissues.
“There is no doubt that vejpning alters tissues in the mouth and lungs” writes Bernard Stewart.
“We also found evidence of mutations in the DNA of the mouth and lungs of people who vejpar, further suggesting exposure to carcinogens”
At the same time, the report points to animal studies linking exposure to e-cigarette aerosol to lung cancer, as well as individual cases where dentists suspected that vejpning contributed to oral cancer in patients who had not previously smoked.
“We also looked at experiments in mice that showed that aerosols from e-cigarettes increased the risk of lung cancer,” writes Mr Stewart.
Criticism: no comparison with smoking
However, the report's conclusions are sharply criticised by a number of researchers in the field of tobacco harm, addiction and behavioural sciences.
A key objection is that the report does not compare vejp with traditional smoking - something considered crucial to put the risks in a relevant perspective.
“The review's conclusions are misleading. The authors state early on that they are not comparing vejpers and smokers,” writes Peter Hajek, Professor of Clinical Psychology at Queen Mary University of London.
Risks with no impact on health
Without such a comparison, even very small amounts of certain substances risk being portrayed as dangerous, say the critics, who, together with Peter Hajek, comment on the report via the Science Media Centre.
“Arguments without any comparable reference points, allow the authors to portray the discovery of a suspect chemical, at whatever level and however insignificant, as ‘carcinogenic’.” writes Peter Hajek.
”The dose makes the poison”
Mr Hajek, as well as several other researchers, also highlights that modern measurement methods can detect extremely small amounts of substances in the body not only in the context of vejpning but in many other contexts - but at levels that have no practical significance for health, both in the short and long term.
“Modern sensitive methods can detect very small traces of chemicals with no impact on health. It's the dose that makes the poison,” writes Peter Hajek.
Criticism of laboratory studies
Moreover, when higher levels of different substances are observed in some studies, they often relate to extreme laboratory conditions. According to Mr Hajek, the report does not refer to studies measuring normal use.
As Vejpkollen previously reported some research teams use questionable methods to test e-cigarettes in clinical trials. One example is a Swedish study in which subjects vejpook high-concentration nicotine at very high power in incorrectly set devices. The device was designed for much lower nicotine levels, and was set without regard to the relationship between airflow and power - likely leading to overheating of the e-liquid and burning of the wick material.
This study has used as the basis for a number of other studies, both in Sweden and internationally, since 2020.
The role of nicotine is questioned
Further criticism is levelled at the report's reasoning on nicotine. According to Mr Stewart, nicotine is also linked to the development of cancer, something that science has not shown, according to Mr Hajek.
“Vaping delivers nicotine at levels similar to smoking, but what is important to point out - despite what the authors suggest - is that nicotine is not carcinogenic,” notes Mr Hajek.
The effects described in the report are in many cases, as in the aforementioned Swedish study, considered to be the effects of nicotine in high doses, often based on animal studies.
“What the article describes are mainly various already known effects of nicotine, and often related to overdose. This is unlikely to occur for extended periods in real-life use situations,” writes Peter Hajek.
Case reports without correlation
The use of individual case reports is also questioned. The fact that people who vejpar develop cancer does not necessarily mean that vejping is the cause, critics say - especially as many were former smokers.
“The authors looked at some case reports of vejpers getting cancer. And although there is no clear correlation, they conclude that vejpning caused cancer without looking at other factors. People who drink orange juice and cycle daily also get cancer - if so, why?” writes Peter Hajek.
Claims ”broad evidence”
The authors of the report, on the other hand, argue that their review weighs up many different types of evidence. They say this has not been done before.
“Our review examined studies that investigated whether vejpning can cause cancer, but none of these covered the wide range of evidence that we have assessed.” writes Bernard Stewart in the Conversation.
However, a much more comprehensive collation has been made of UK Public Health Agency and on an ongoing basis by Cochrane reviews. Something that critics point out.
“Selective selection of studies”
Professor Peter Shields, Emeritus Professor of Medical Oncology at Ohio State University, notes that Bernard Stewart's report does not really add anything new. He also argues that the report is based on a narrow and hand-picked selection of studies.
“This article doesn't really add anything we don't already know, but it selectively chooses studies - and omits many others that contradict the authors” claims - which misleads the reader." writes Peter Shields to Science Media Centre.
In particular, he points out that the mechanistic studies highlighted - i.e. studies at the cellular and molecular level - do not necessarily tell us anything about actual risk in humans.
“None of the mechanistic studies they refer to have been validated as actual risk indicators in humans, and the authors” inability to recognise that leads to misleading conclusions." writes Peter Shields.
Ignoring the evidence of harm reduction
According to Shields, the report also misses a key piece of research: what happens when smokers switch to e-cigarettes?
“We didn't need a study to conclude that it is inappropriate for people who have never smoked to start vejpa. Where they miss the mark is that they don't highlight the many studies that show greatly reduced exposure to carcinogens when smokers switch to vejpning.” he writes to Science Media Centre.
Broad consensus on harm reduction
Peter Shields refers, among other things, to studies of airways and cell changes in the mouth that show a change for the better when cigarette smoking is replaced by vejpning. In comparison with the control group, the studies show that vejp users have similar values to non-smokers.
“There is a broad consensus that the harm reduction effect is positive both for the individual and for public health.” writes Peter Shields.
Worried about media impact
He concludes by expressing concern about how the report's conclusions might be used.
“This article does not properly address the research findings, and hopefully the media will not uncritically reproduce the incorrect conclusions.” writes Peter Shields.
High impact in the media
The report on e-cigarettes and cancer risks was recently published in the peer-reviewed journal Carcinogenesis and launched via an opinion piece The Conversation. The report has received widespread media attention, including in major media outlets such as The Guardian, The Indipendent and popular science journals such as Swedish Illustrated Science. In the home country of lead author Bernard Stewart, Australia, interviews in the national media have been one after another. The regulation of e-cigarettes in Australia is very strict and vejp products can only be sold through pharmacies, which has led to the country's 1.3 million vejp users now buying their e-liquids and devices via the black market.
Facts: What does the research really say about vejping and cancer risk?
- Vejping means a significantly lower exposure to carcinogens compared to smoking
- For many harmful substances, the levels of vejpare close to those of non-users
- The substances that can still be measured are usually found in very low concentrations
- Vejping is considered not be risk-free, especially for people who have never smoked
- For smokers switching to e-cigarettes, it means a sharp reduction of health risks linked to nicotine use
- E-cigarettes are one of the most common and effective tools to quit smoking, according to independent Cochrane reviews (which continuously evaluate health interventions based on randomised control trials)
Source: UK evidence review from 2022 (Nicotine vaping in England: evidence update)
