What is in the vapour?
An e-cigarette does not burn tobacco; it heats a liquid into an aerosol that the user inhales. The liquid usually contains nicotine, a solvent such as propylene glycol or glycerine, and flavourings. Because there is no combustion, the aerosol lacks much of the tar and carbon monoxide of cigarette smoke — which is why vaping is often described as less harmful than smoking for an adult who already smokes.
Less harmful is not the same as harmless. The aerosol still carries fine particles, heated solvents, and metals from the heating coil deep into the lung. Vaping can irritate the airways and worsen asthma, and the long-term effects of inhaling these mixtures for decades are simply not yet known — the products are too new.
EVALI: when vaping injures the lung fast
In 2019 clinicians described a sudden, severe illness in vapers now called EVALI — E-cigarette or Vaping product use-Associated Lung Injury. Affected people developed cough, shortness of breath, fever, and falling oxygen saturation over days, and their scans showed widespread ground-glass opacity — a hazy whiteout of the lung tissue.
Investigators traced most cases to vitamin E acetate, a thickening additive found mainly in informal, black-market THC vaping products — not the nicotine devices on store shelves. Treatment is supportive: stop vaping, give oxygen and often steroids, and most people recover, though some need intensive care.
Secondhand smoke: harm you did not choose
Secondhand smoke is the mix a non-smoker breathes from someone else's cigarette — both the smoke they exhale and, importantly, the smoke drifting off the burning tip. That sidestream smoke is unfiltered and can be even richer in some toxins than the puff the smoker takes.
- In children: more ear infections, more frequent and severe asthma attacks, more chest infections, and a higher risk of sudden infant death.
- In adults: a measurably higher risk of lung cancer and heart disease, even in people who never smoked themselves.
- There is no safe level of exposure; ventilation and 'smoking sections' reduce but do not remove the risk.