Passive smoking: an invisible danger that kills more than 1.6 million people a year

A planetary-scale study

The paper, published on 8 September 2026 in The Lancet, is enormously ambitious: the researchers analysed data from 204 countries and territories between 1990 and 2023, broken down by age and sex, and reviewed studies published between 2010 and 2025 to assess the impact of passive smoking on nine health conditions, including asthma. They estimated that, in 2023 alone, around 2.7 billion people were exposed to secondhand smoke worldwide, including 767 million children aged 0 to 14.

1.66 million deaths and millions of years of life lost

That exposure is estimated to have resulted in 1.66 million premature deaths in a single year — out of approximately 8 million deaths attributable to tobacco in 2023. In addition, passive smoking is estimated to have caused the loss of 44.8 million years of healthy life worldwide, principally due to ischaemic heart disease (the heart condition caused by insufficient oxygen reaching the cardiac muscle). And in children, 5.16 million respiratory infections in that same year are attributed to it.

Why other people's cigarette smoke is so dangerous

Anyone who breathes secondhand smoke is actually exposed to two types of smoke: the smoke that comes from the lit tip of the cigarette and the smoke exhaled by the smoker. The first, which is unfiltered and does not result from complete combustion, contains higher concentrations of toxic and carcinogenic compounds than the second. And there is one crucial point: there is no safe threshold of inhalation. We are not talking about an 'acceptable' amount; any exposure counts.

Heart, lungs and metabolism

These exposures increase the risk of cardiovascular, respiratory and metabolic diseases. Children are particularly vulnerable: their lungs are still developing, they suffer more respiratory infections and they have a higher risk of asthma. That is why such a significant share of the harm falls precisely on those who are least able to decide what they are exposed to.

Fewer smokers, but the same number of people exposed

Here one of the study's most striking paradoxes emerges: despite the fact that global smoking prevalence has fallen by 22% since 1990, the absolute number of people exposed to secondhand smoke has remained stable at a global level, and has increased sharply in sub-Saharan Africa, North Africa and the Middle East. Fewer smokers as a proportion, but no fewer victims of smoke.

The home: a blind spot

The study emphasises the urgency of strengthening anti-tobacco policies not only in public places but also in the domestic sphere, and in particular to protect women and children. Because the home, which should be the safest place of all, is often where exposure is hardest to avoid.

What I want you to remember

Passive smoking is not 'smelling a little like smoke': it is a real cause of heart disease, cancer, and respiratory problems, with no safe dose. The good news is that it is almost entirely preventable. In practice: never smoke inside the home or in the car — opening the window does not protect anyone — and especially not near children or pregnant women; support smoke-free public spaces; and, if you smoke, quitting protects not only your own health, but also the health of everyone around you.

As a physician, I would add a detail I often see in my practice: tobacco — both active and passive — also ages the skin and impairs wound healing, so taking care of the air we share is also taking care of our skin. I am Dr. Florian Vallecillo, and protecting those around us from smoke — especially children — is, in all likelihood, one of the most cost-effective and generous health decisions we can make.