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What the research says so far
There are currently no long-term studies that show exactly what repeated exposure to secondhand vapour does to health over many years. Vaping is still relatively new compared with smoking, so the evidence base is much smaller.
Most of the available research has focused on short-term exposure, measuring what happens to indoor air and whether people nearby absorb nicotine or other substances. These studies suggest secondhand vapour is generally less harmful than secondhand smoke, but that does not mean it is completely harmless.
Why long-term evidence is limited
Long-term studies take time. Because widespread vaping only became common in the UK in the last decade or so, researchers have not yet had enough years to follow large groups of people exposed to vapour in the same way they have studied tobacco smoke.
It is also difficult to separate the effects of secondhand vapour from other factors. People who live with vapers may also be exposed to other pollutants, and health outcomes can be influenced by age, existing conditions, and smoking history.
What short-term studies have found
Research has found that secondhand vapour can contain nicotine, tiny particles, flavourings, and trace chemicals. However, the levels are usually much lower than in tobacco smoke.
Some studies show that exposure can irritate the eyes, throat, or airways in sensitive people. This is especially relevant for children, pregnant people, and anyone with asthma or other breathing conditions.
What this means for public health in the UK
In the UK, public health advice generally treats vaping as less harmful than smoking, but not risk-free. The current view is that non-smokers and children should avoid inhaling secondhand vapour where possible.
Indoor spaces, cars, and homes can all become relevant settings for exposure. While the risks appear to be lower than with cigarettes, many experts still recommend courtesy and ventilation, especially around vulnerable people.
Bottom line
There are no strong long-term studies yet that can fully answer the question of how secondhand vapour affects health over decades. That means scientists cannot rule out all risks, even though early evidence suggests the danger is much lower than with secondhand smoke.
For now, the safest approach is to avoid vaping around others, particularly children and people with health conditions. As more time passes, researchers will be able to provide clearer answers based on longer follow-up data.
Frequently Asked Questions
Long-term studies on secondhand vapor examine whether repeated exposure over months or years is linked to lasting health effects. Researchers study them to understand possible impacts on the lungs, heart, and overall wellbeing, especially in children, pregnant people, and those with asthma or other conditions.
Long-term studies of secondhand vapor commonly evaluate respiratory symptoms, lung function, asthma control, cardiovascular markers, irritation of the eyes and throat, and exposure-related changes in biomarkers such as nicotine metabolites and particulate levels.
No. Long-term studies suggest secondhand vapor generally contains fewer toxic chemicals than secondhand cigarette smoke, but it is not harmless. The evidence is still developing, and potential risks may differ in type and magnitude from those of tobacco smoke.
Researchers often measure exposure using air-quality sensors, indoor particle counts, nicotine or cotinine levels in saliva, urine, or blood, and questionnaires about time spent near vaping. Some studies also track exposure patterns in homes, cars, schools, or workplaces.
Long-term studies indicate that exposure to secondhand vapor may irritate the airways and could worsen asthma symptoms in some people. The evidence is not as extensive as for cigarette smoke, but concerns remain for sensitive individuals and children.
Long-term studies of secondhand vapor in children are limited, but researchers are concerned that repeated exposure could affect developing lungs, increase irritation, and contribute to respiratory symptoms. More long-term data are needed to clarify risks in children.
Long-term studies directly focused on secondhand vapor during pregnancy are limited. Because nicotine and other aerosol components may be present, researchers advise caution, as repeated exposure could potentially affect maternal health and fetal development, though more evidence is needed.
Some long-term studies assess blood pressure, heart rate, vascular function, and inflammation markers. Early findings raise concern that repeated exposure may affect cardiovascular health, but evidence is still less mature than for cigarette smoke and requires more research.
Studies often consider nicotine, ultrafine particles, volatile organic compounds, flavoring chemicals, formaldehyde-related compounds, and metals that may be present in aerosol. The exact mix depends on the device, liquid, power settings, and environment.
No. The long-term evidence is still emerging and is less comprehensive than the evidence for secondhand smoke. Existing studies suggest secondhand vapor is not harmless, but researchers need more years of follow-up and larger populations to draw firmer conclusions.
Common limitations include short follow-up periods, changing vaping devices and liquids, mixed exposure to smoke and vapor, self-reported exposure data, and small study sizes. These factors make it harder to isolate the effects of secondhand vapor over time.
Exposure can vary significantly by setting. Long-term studies often find that enclosed spaces with poor ventilation, such as cars or small rooms, may produce higher exposure levels than larger or better-ventilated areas like some workplaces or public spaces.
Yes, long-term studies are designed to examine effects in nonsmokers who are repeatedly exposed. Findings suggest nonsmokers can still absorb nicotine and aerosol components, and some may experience irritation or respiratory symptoms over time.
Many studies track flavoring chemicals because some may be irritating when inhaled. Researchers are still determining how chronic low-level exposure through secondhand vapor influences health, especially for people exposed regularly indoors.
Long-term studies show that secondhand vapor can worsen indoor air quality by increasing fine particles and nicotine-related residues. Ventilation can reduce but does not necessarily eliminate exposure, especially in enclosed spaces.
At present, long-term studies have not produced definitive cancer-risk estimates for secondhand vapor. Researchers note that because some aerosol constituents can be harmful, more long-term data are needed before firm conclusions can be made.
Nicotine is important because it can be absorbed from secondhand vapor and may have biological effects even without direct use. Researchers study it as a marker of exposure and because it may influence cardiovascular, developmental, and addictive pathways.
Researchers often collect information on room size, ventilation, device power, and e-liquid composition because these factors strongly affect how much aerosol accumulates and how much bystanders may inhale over time.
Based on current evidence, many experts recommend minimizing indoor vaping around children, pregnant people, and individuals with respiratory conditions. Better ventilation, avoiding vaping in enclosed spaces, and respecting smoke-free or vape-free policies can reduce exposure.
Future studies need longer follow-up, larger and more diverse populations, better exposure measurements, and clearer separation of vapor exposure from other pollutants. This will help researchers determine which health effects, if any, are caused by long-term secondhand vapor exposure.
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