The component-by-component picture

Vape is a mixture of components, each with different evidence on cancer risk:

1. Nicotine. Not classified as a Group 1 carcinogen by IARC. The addictive component of vape but not the cancer-causing component of smoking. Some research suggests nicotine may have tumour-promoting effects on existing cancers though it is not tumour-initiating. Our nicotine cancer guide covers this specifically.

2. Propylene glycol (PG). Widely used in food, pharmaceuticals plus cosmetics. Considered generally safe at normal temperatures. Some concerns have been raised about decomposition products at high vape temperatures but at typical vape conditions PG is considered low risk.

3. Vegetable glycerine (VG). Food-grade ingredient. Generally considered safe. Like PG it can produce some decomposition products at very high temperatures but at typical vape conditions VG is low risk.

4. Flavour compounds. The most variable component. Most food-grade flavourings are safe for ingestion. Inhalation safety is less well-established for many compounds. Some flavour compounds (notably diacetyl, acetyl propionyl) have been linked to lung disease though banned in UK compliant products since 2016. Some compounds at high heat may produce concerning breakdown products. This is an active research area.

5. Coil-derived metal particles. Heating coils can shed trace amounts of metals (nickel, chromium, copper, lead) into vapour. Published studies have found variable amounts in different devices. Levels are generally far below those in cigarette smoke. Quality control in UK-compliant devices reduces but does not eliminate this concern. Replacing coils as specified by manufacturers minimises exposure.

6. Thermal breakdown products. At very high wattages certain compounds can form including formaldehyde plus acetaldehyde which are Group 1 carcinogens. These are present at low levels at normal vape temperatures but rise significantly with poorly-maintained devices, dry-hit conditions (wicking failure) or excessive wattage. Proper device use minimises this.

What current research shows

Research on vape and cancer risk comes in three main forms:

1. Biomarker studies. Measure specific chemicals in the body that indicate carcinogen exposure. Key findings:

• Vapers have much lower carcinogen biomarkers than smokers. Often 90+ per cent lower across multiple compounds.
• Vapers typically have slightly higher biomarkers than non-users. The increase is small but not zero.
• Dual users (who vape and smoke) have levels between vapers plus smokers. Not as good as switching fully.

2. Short-term DNA damage studies. Examine markers of DNA damage in cells exposed to vape. Findings are mixed. Some show measurable damage. Others show none. Effect size is consistently smaller than for smoke exposure.

3. Population studies. Track cancer incidence in large groups of vapers over time. These are the gold-standard evidence but require long follow-up periods. Current population data is still developing because widespread vape use only dates to around 2010. Full picture will emerge over the next 10-20 years.

UK evidence synthesis: The Cochrane Review 2024 remains the most authoritative evidence source. It confirms vape is an effective smoking cessation tool plus supports the position that vape harm is substantially lower than smoking. Cancer-specific long-term data is an ongoing research priority.

The PHE 95 per cent less harmful figure

Public Health England's estimate that vape is 95 per cent less harmful than smoking has been repeated since 2015 plus maintained through subsequent reviews. The figure is based on:

• Mechanistic analysis of which harmful compounds in smoke are absent in vape.
• Biomarker comparisons showing vastly reduced carcinogen exposure.
• Short-term health outcome studies showing rapid improvements when switching.
• Expert panel consensus on overall harm profile.

The figure is an estimate plus has some uncertainty. Some critics argue it is too low (implying vape is safer than the estimate) while others argue it is too high (implying more risk than 5 per cent). The estimate has held up across multiple reviews including the 2022 OHID evidence review plus remains UK public health consensus.

Who has higher vape cancer risk

Several factors may increase vape-specific cancer risk:

• Heavy use. More vape means more exposure to any harmful components present.
• Long duration. More years of use means more cumulative exposure.
• High wattage devices. May produce more thermal breakdown products.
• Poor device maintenance. Old coils, dry hits, unregulated devices all raise exposure.
• Non-compliant products. Black market or poorly-regulated products lack quality controls.
• Dual use with smoking. Does not reduce smoking cancer risk substantially.
• Starting from non-smoker baseline. Adds risk that was not there before.

Conversely switching from smoking to vape substantially reduces cancer risk from the smoking baseline.

Practical implications

For smokers:

• Switching to vape substantially reduces cancer risk compared to continued smoking.
• NHS Stop Smoking Services support this transition with highest success rates.
• Complete cessation is cleanest but vape is meaningful harm reduction.

For existing vapers:

• Use UK-compliant devices from reputable retailers.
• Maintain devices properly: fresh coils, adequate e-liquid, no dry hits.
• Avoid unregulated or high-wattage devices unless you understand the risks.
• Step down nicotine strength over time.
• Consider full cessation for cleanest long-term cancer risk profile.

For non-nicotine users:

• Do not start vaping. NHS guidance is clear that vape is a harm reduction tool for smokers, not for non-smokers.
• Starting vape introduces cancer risk that was not there before.

For anyone with cancer or family history:

• Discuss nicotine use with your oncology team or GP.
• NHS guidance typically favours cessation during active cancer treatment.
• Individual risk factors matter more than general population estimates.

Red flag symptoms

Cancer symptoms warrant prompt medical assessment regardless of nicotine use. Book GP appointment for:

• Unexplained weight loss.
• Persistent cough lasting more than 3 weeks.
• Blood in sputum, urine or stool.
• Unexplained lumps.
• Persistent fatigue.
• Unexplained pain.
• Changes in moles.
• Any symptom you are concerned about.

NHS cancer screening programmes (bowel, breast, cervical) matter regardless of vape use. Keep up with recommended screening.

Practical approach

• Current smokers should switch to vape as meaningful harm reduction while working toward full cessation.
• Current vapers should use compliant devices properly maintained plus step down strength over time.
• Non-nicotine users should not start.
• Everyone should keep up with cancer screening.
• Persistent symptoms warrant GP review regardless of nicotine status.

For lower-strength options as part of a step-down plan, our nicotine salts collection covers every UK compliant strength from 20mg down to 3mg.