Together we will beat cancer


It’s just over a decade since e-cigarettes first hit the shelves. And since then there’s been an explosion in their popularity, with almost 3 million adults using them in Great Britain today.

But this rapid popularity, and the potential these devices hold to help people stop smoking, has left some challenges. The biggest being that research looking at their safety has struggled to keep up.

Many studies have shown that e-cigarettes appear to be far safer than smoking. But there’s still a big misconception that e-cigarettes are as harmful as smoking, and that could be stopping smokers who might benefit from switching to them.

Now a new study from a team of our scientists at UCL helps put to rest these fears. And depending on how you define ‘long-term’, the findings are the most convincing evidence to date that e-cigarettes are far safer than smoking.

E-cigarettes should be far safer than smoking

Tobacco is the world’s leading cause of preventable death, accounting for around 6 million deaths each year. That’s thanks to the cocktail of over 5,000 chemicals in cigarette smoke, of which at least 70 may cause cancer.

E-cigarettes, on the other hand, do not contain tobacco. Instead, they carry a nicotine-containing liquid which is heated into a vapour and breathed in. The nicotine satisfies the cravings associated with a smoking addiction, but doesn’t cause cancer.


Click to view full size image.

The fact that e-cigarettes don’t produce tobacco smoke and the countless chemicals found within it has always suggested that these devices should be safer than smoking. But when they first came to the market, there wasn’t enough research to be sure of this. This is why scientists around the world have sought to understand what’s in e-cigarettes and what the impact of these products might be.

Early studies looking into this showed that e-cigarette liquids, and the vapour they produce, don’t contain the same level of most toxic chemicals as tobacco cigarettes. In fact, these levels have been found to be so low that Public Health England and the Royal College of Physicians estimate that e-cigarettes are ‘around 95% safer than smoking’.

But, until now, nobody had looked at what everyday users are actually exposed to in the real-world.

So the study out today, led by Dr Lion Shahab, is the first to look at the effects of e-cigarettes in what they define as ‘long-term users’.

Just how safe are they?

The study included a group of e-cigarette users, who had been using them for an average of around 17 months, and measured the levels of nicotine and 26 potentially harmful chemicals in their body, by looking at samples of their urine and saliva.

The team compared the results to cigarette smokers, and people who both smoked and used e-cigarettes. They also looked at people who used nicotine replacement therapy (NRT), which is commonly used to help people stop smoking or as a long-term alternative.

“We looked at NRT users because we know these products are safe to use,” says Shahab. “We thought they would be a good comparison,” he adds, because long-term users get their nicotine hit from a smoke-free source, much like e-cigarette users.

Interestingly, the nicotine levels found in the samples from e-cigarette users were very similar to those who used NRT and to smokers. This suggests that people are able to satisfy their nicotine cravings through using either of these products.

The full benefit of using e-cigarettes is from completely stopping smoking

– Dr Lion Shahab, UCL

“Part of the reason why people use e-cigarettes is to stop smoking, and we have shown that they provide effective delivery of nicotine,” says Shahab.

But the key finding came when the team looked in the samples at the levels of potentially toxic chemicals. They found that there was a remarkable difference in the levels of these substances between the different groups. In fact one chemical, called NNAL (known to cause lung cancer), was 97% lower in e-cigarette users compared to smokers.

Not only did e-cigarette users have lower levels of these substances compared to smokers, but they were also found to have very similar levels to people using NRT – something that Shahab is quick to point out is known to be relatively safe.

“We have 3 decades of research into the safety of NRT, and we’ve not picked up any significant long-term health issues,” he says.

So if e-cigarettes have the same effect on the body as an established stop smoking treatment, then surely we can assume that these products are relatively ‘safe’ too? While nothing can ever be considered completely safe, we can compare it to the other things we experience in our day to day lives.

We still need to be cautious about e-cigarettes

Unfortunately, we’re not 100% convinced yet. There are a number of points left to uncover that this study hasn’t yet answered.

The first is that people who used e-cigarettes while still smoking didn’t reduce the levels of toxic chemicals they were exposed to. And a large number of e-cigarette users do still smoke.

“The full benefit of using e-cigarettes is from completely stopping smoking,” says Shahab. “Any health benefits come from dramatic reductions in these chemicals, and we’re not seeing this in people that use both e-cigarettes and combustible cigarettes.”


Dr Lion Shahab, a Cancer Research UK-funded scientists at UCL

And although this study found significantly lower levels of these substances in vapers than smokers, the chemicals are still there.

The study didn’t compare the levels of chemicals in people who don’t smoke or use  e-cigarettes with those who do, so it’s not known what the differences are likely to be. If these chemicals are found to be at higher levels in people who use the devices  there’s still a chance that some harm is being done.

According to Shahab the next step is to look for signs of damage in these different groups of people, instead of looking at levels of chemicals that cause harm. But it can take decades to see these differences.

We also know that different users use different devices and liquids. So it could be that some are safer or more harmful than others. And people also use the devices in different ways. So further work needs to be done to understand these differences, so that each vaper is using their device as safely as possible.

We intend on playing a key part in finding these answers. And that’s why we set up the UK E-Cigarette Research Forum, made up of the country’s top tobacco and e-cigarette researchers, to do exactly that.

What does this mean right now?

This study confirms that e-cigarettes are far safer than smoking. If you’re a smoker, the best thing you can do for your health is to stop. And the most effective way to do so is through free Stop Smoking Services.

And as we’ve written about previously, a number of successful quitters have managed to ditch the cigs through using both an e-cigarette and specialist support.

But this doesn’t mean that e-cigarettes are entirely without harm. If you’re a non-smoker, it’s not advisable to start vaping. We can’t yet be certain of all the long-term effects across all devices and liquids, so it’s best not to pick up the habit.

So although it’s unlikely e-cigarettes will be shown to be completely harmless (nothing ever is), today’s results are a landmark moment in showing just how much safer they are than smoking.



Shahab, L., et al. (2017). Nicotine, Carcinogen, and Toxin Exposure in Long-Term E-Cigarette and Nicotine Replacement Therapy Users. Annals of Internal Medicine. DOI: 10.7326/M16-1107


Michal Khan June 10, 2017

In my point of view, the e-cigarette is dangerous for health.Every year huge no. of peoples dies due to smoking (cancer, TB). Smoking also affects the environment and also the person who is nearest to the smokers. While reading this news ( I found many disadvantages of smoking.

John Harrison May 27, 2017

I have smoked for fourth plus yes and finally decided enough is enough. At first I smoked and used the e-cig. It didn’t make sense so I put all the tobaco out and have a new and better unit. So, three months without tobacco and all is fine. Like one of the other commentors said, tobacco, never again. I was just questioning what is the latest research on the subject? I’m glad I checked it out.
If your still using tobacco, your not doing yourself right.

Jamie Johnson May 27, 2017

Before people say they don’t work or make them ill have you tried all types of devices no. have you every used other types of e-liquids nope. You all try one style of liquid and one type of device. Then say it no good. That is not how some one should be trying vaping at all. There 100s of devices and liquids and ways to vape so do some research before you just buy a pice of junk. You will notice lots of benefits in the end.

My blog May 25, 2017

This article is now on my bookmark bar. Thank you
for writing this.

Carl Alexander May 3, 2017

Hi Renee,
Thanks for your question. The vapour you breathe into your lungs from your e-cigarette is the evaporated form of the e-liquid contained in the device. This is made up of many tiny droplets of the liquid, and forms the cloud you see when you breathe out again.
The evidence from the study featured in this blog post shows that breathing in this vapour from an e-cigarette appears to be far less harmful than breathing in smoke from tobacco.
Best wishes,
Carl, Cancer Research UK

Michelle May 1, 2017

I have never felt so ill in my life! I’m convinced Vaping is not the way forward. I’ve had to stop and can no longer force myself to keep doing it. I’ve been vaping for 17 month 3-6mg Nicotine, I feel like I’m constantly sucking in air and can feel my stomach expanding, feel tired and nausea comes and goes while I’m using it, causes indigestion through sucking in all of the air not to mention the chemical taste, it’s done nothing but make me miserable, I’m so glad Ive stopped and my symptoms have all gone, I definitely don’t it’s the answer

Lynne April 30, 2017

I smoked for 30+ years & tried NRT patches which for me didn’t work. When my Dad changed to e-cigs after smoking for 60+ years, I decided to try it. I’ve been vaping for for 3.5 years now & have absolutely no intention of smoking ever again.

My clothes & hair are always fresh, I don’t smell of smoke all the time. I don’t have a cough any more & make sure I’m not behind a smoker when I’m out. I have a choice whether to be in the ‘firing line’ of their smoke or to simply be out of the way of it, which for me is no big deal.

I had unrelated inflammatory breast cancer which was one of the most serious & all I can say to the gentleman who was quite adamant in his views is that each time I was hospitalised I saw people dying from lung cancer & believe me that’s something you never forget.

Everyone has the right to be treated whether they are couch potatoes eating fast food, alcoholics, smokers, the list of addictions in endless, or people who have a healthy lifestyle. We are all individual human beings & deserve to be treated with respect & dignity.

Thank you NHS & CancerResearchUK. Without you & the love & support of my family I wouldn’t be here today & that’s a fact.

Keep up the good work.

Renee April 30, 2017

I was a 30 plus year smoker and have totally quit by using an e cig. I enjoy vaping but wonder if I am breathing in any sort of liquid into my lungs. Is this true or no?

chris April 24, 2017

It is amazing and great news .I am an ex-smoker and have been for the last 40 years but my son is a smoker and he uses the e-cigarettes and as much as I would like him to stop after reading this article it puts my mind at rest know that he is at low risk when he is using the e-cigarette . PS thank Dr Lion Shahab and his team for all the hard work that is carried out.

Josh April 23, 2017

Its amazing article and great news for all the vapers. I hope they will soon reach to the bottom of the issue- that is lack of enough scientific evidence about e cig. This research is great addition to the current efforts by many researchers

Carl Alexander April 20, 2017

Hi Susan,
Thanks for the comment.
The evidence so far shows that passively breathing vapour from e-cigarettes is unlikely to be harmful. We’re funding a range of projects on e-cigarettes, including ones looking at their safety and health impact.
You may also find this blog post, which answers a number of common questions about the safety of e-cigarettes, interesting.
Carl, Cancer Research UK

Susan April 15, 2017

I would like to see research into the effectsof the vapour on the Lungs. What is the effect of taking these warmed chemicals into the delicate lungs? What chemicals are “safe” to inhale when warmed? As a non smoker, I am surrounded by friends who now use vaping devices. They never stop all evening, there is no break or routine like with a cigarette. At the end of a night out with my friends the secondary effects to me of the vapour is, dry nose, sore throat often swollen eyes or sinus pain! The next morning I feel like I have a cold. I am sure i am not the only sensitive person on the planet. Please do more research quickly.

Crawford Mackay April 10, 2017

@Steve Johnson – Definitely an angry man who’s ire is directed at the wrong place. Here are a couple of facts :

Cost of Smoking Related illness to the NHS : Apx £2 Billion Annually
Tax Receipts from Tobacco & Related Product Sales : Apx £10 Billion Annually

That points to an £8 Billion net gain for the Government, which, if given to the NHS and/or Cancer Research would add additional fund in the fight against cancer and the research needed to advance it.

Tell me, have you had a drink? Do you enjoy a pint? If that’s the case, and you do, you sir, are a hypocrite. Drinking is a known cause of cancer, seven types if my reading on this very site remains correct. Not to mention the huge number of other non-cancerous effects, not just to the person concerned, but to society as a whole. Alcoholism, Drink Drivers, Domestic abuse, mental health issues, criminal behaviours – the list goes on.

After smoking, and obesity, Alcohol is a known detriment to health – however, unlike smoking, and to an extent, obesity, alcohol harms society in many more direct ways. A smoker, assuming they smoke only in designated areas, will only be killing themselves. An inebriated person (or even impaired only slightly) driving their car, risks everyone around them, regardless of their smoking, drinking, eating habits, their age, background or race.

Figures to consider –
Direct Cost to the NHS for Alcohol Related Treatment – £3.5 Billion Annually
Cost to the Justice System for Alcohol Related Crime – between £8 and £11 Billion Annually
Cost through Lost Work Days and Productivity Loss – Upwards of £7 Billion Annually

Sounds like I’m bashing drinking, and maybe I am…but here, sir, is the difference between you and I…I would never, ever, deny treatment to someone who is ill, regardless of the cause of their illness. In addition, the research into Smoking Related Cancers doesnt just cover smokers – lung cancer is caused by numerous factors, only ONE of which is smoking. Cancer Research, unlike you, do not judge – their sole aim is the fight against cancer regardless of its source.

Remember that smoking is an addiction, just like alcoholism, gambling and many many other vices. You may also want to remember the Hippocratic Oath taken by all Doctors and Physicians and the message it delivers : Do No Harm

Carl Alexander April 10, 2017

Hi Graham,
Thanks for your comment.
That’s a really good point. It will be important for future research to look at the effects of using e-cigarettes compared to not smoking or vaping. Understanding this evidence as it emerges will be a priority for us. We’re also continuing to fund research aimed at measuring the safety or harms of e-cigarettes as people look to stop smoking tobacco, as there’s still more to be done here.
Carl, Cancer Research UK

Graham Clarkson April 7, 2017

Thanks to all at CRUKresearch , Its a well needed study involving real people and not lab conditions with mice.I have been vaping for almost 6 years and the results are no surprise to me but I always point people in your direction when they say yes but no long term studies or we don’t know the long term effects and we don’t know whats in them etc etc
Its key that smokers get the right data to make a choice to switch and in doing so can save countless needless premature deaths, so I really appreciate all your work in this field.
Now we have data between smokers,NRT and vapers will there be further studies showing difference between vaping and non smokers?
This will be a great next step for the non vaping general public to fully understand the difference by putting vaping in context with not vaping, although the immediate must be to inform smokers to make a switch.
Keep up the good work

Carl Alexander April 7, 2017

Hi J,
Thanks for your comment.
When children do use an e-cigarette it’s much more likely that they will also be a current or ex-smoker. Very few children who have never smoked a tobacco cigarette have tried e-cigarettes.
It’s also illegal in England to sell nicotine products to anyone under the age of 18, and Cancer Research UK will continue to campaign to protect children from the harms of smoking.
Something else to note is that since the introduction of e-cigarettes, there hasn’t been an increase in childhood smoking rates in Great Britain. So e-cigarettes don’t appear to be acting as a gateway towards smoking tobacco cigarettes.
Carl, Cancer Research UK

J Smalley April 7, 2017

E-cigarettes are increasingly becoming a huge problem in young children from the age of 12, I’m lead to believe. My concern is, how’s it affecting them?

Steve Johnson April 6, 2017

Josh Groeben. “Grow a Conscience mate” First off, I’m not your mate and secondly, what about those who have died due to passive smoking? Shouldn’t Smokers also grow a Conscience or do we just accept their bad habits and addictions? Behave yourself! I want the money I donate to go to Cancer Patients who haven’t inflicted it upon themselves. You know the risks, it’s advertised enough so please do not use my money to help those smokers who decide and think they know best.

Josh Groeben April 6, 2017

@ Steve Johnson You seem like an angry person who genuinely does not want other people to try to better their health. “Do not use my money to help smokers who have Cancer” is a horrible thing to say. Are you saying you don’t care if people slowly and painfully die? And if smoking was so easy to quit don’t you think everyone would do it?

Nicotine is one of the most studied drugs in the world and there is still no consensus on how bad the effects of it are. Some studies even show it having positive effects as a neuro-stimulator and nootropic.

I am in the Armed Forces and have many friends who smoke, some quite heavily. I would personally love if my friends and colleagues would move to e-cigs. When studies find that it is 95-97% better for you then smoking it can only do wonders for their health to switch.

Grow a conscience mate.

Steve Johnson April 5, 2017

Personally, I believe all forms of inhalation of Nicotine should be discouraged. I have always been against smoking especially as a serving member of The Armed Forces where it was rife. Many a day I would have to sit alongside colleagues and have to endure smoking in the passive form.
Today whilst travelling back from Barcelona on an EasyJet flight, I had to remind a passenger that it is illegal to use an E-Cigarette on the plane. Before you know it Restaurants and other Public places will be allowing E-Smokers to again pollute the air we breathe.
With articles like this it encourages people to continue the disgusting habit of blowing second hand smoke/vapour in non smokers faces.
I for one did not sign up to give a donation each month for it to be used to help smokers recover from Cancer. You smokers know the risks involved with smoking and I personally do not want to help you. After living and working with smokers I never once put a Cigarette to my mouth. Not even to try it once.
You get one chance at life. Smoke and you will regret it. Do not use my money to help smokers who have Cancer.