How many people does second-hand smoke kill a year?
About 1.66 million. That is the worldwide death toll in 2023 traced back to second-hand smoke, along with 44.8 million years of healthy life lost. The estimate runs from 1.33 million to 2.07 million deaths, so even the low end of that range is large.
The figure comes from the Global Burden of Disease Study 2023, published in The Lancet Public Health. It is the first report in that project built specifically around second-hand smoke, and it covers 204 countries and territories from 1990 through 2023.
Second-hand smoke is the smoke a non-smoker breathes from someone else’s cigarette. Nobody chooses it. That is what makes it different from smoking statistics, where the exposure is at least a personal decision.
How many people breathe second-hand smoke?
An estimated 2.71 billion people were exposed in 2023, roughly a third of everyone alive, with a range of 2.44 billion to 3.02 billion. That total includes 767 million children aged 0 to 14.
Exposure is not spread evenly. Age-standardized prevalence was highest in southeast Asia, east Asia, and Oceania at 48.4 percent, close to half the population. In some countries, women were exposed at nearly 1.8 times the rate of men, and that gap points at the home rather than the workplace or the bar. Indoor smoking bans have cleared most public spaces in countries that enforce them, which leaves the home and the car as the settings that matter, and those are exactly the rooms a child cannot walk out of.
What the data show
The two headline harms are cardiovascular and respiratory. Ischemic heart disease was the single largest contributor overall, at 12.0 million disability-adjusted life-years. A disability-adjusted life-year, or DALY, is one year of healthy life lost, either to early death or to living with illness.
In children, the picture flips to the lungs. Lower respiratory infections led the burden in that group at 5.16 million DALYs. Children have smaller airways, they breathe faster than adults, and they cannot leave the room.
The trend line is the part worth sitting with. Global age-standardized prevalence fell 22.2 percent since 1990, which sounds like a win. But the absolute number of people exposed has not moved. Population growth cancelled the progress out. In sub-Saharan Africa the number of exposed people rose 98.5 percent, close to double, and in North Africa and the Middle East it rose 72.1 percent.
Dr. Kumar’s Take
Percentages can flatter a public health story. Reported as a rate, a 22.2 percent decline since 1990 looks like tobacco control is winning. Reported as a head count, the same data set shows 2.71 billion people still breathing it, which is where the story stalls. Both are true, and the second one is what a child in a smoky apartment actually experiences.
Second-hand smoke also deserves more attention as a heart problem than it usually gets. It is filed in most people’s minds under lung disease, yet ischemic heart disease carried 12.0 million DALYs here, more than double the children’s respiratory burden. Tobacco smoke damages the lining of blood vessels, and there is no threshold below which it stops doing that.
The regional numbers are the part I would watch. A 98.5 percent rise in sub-Saharan Africa and a 72.1 percent rise in North Africa and the Middle East are not rounding errors, and a reassuring global average sits directly on top of them.
How strong is the evidence?
This is a modeling study, not a trial, and that shapes what it can tell you. The team pulled population-based surveys and household composition data, then filled the gaps between countries and years using a statistical method called spatiotemporal Gaussian process regression. In plain terms, they used data from places and years they had to estimate places and years they did not. That is why every figure here comes with a wide uncertainty range, and why the death estimate spans 1.33 million to 2.07 million rather than landing on a single number.
They then applied relative risks for nine health outcomes, asthma newly among them, using a method called Burden of Proof that weights how strong the underlying evidence is for each link. Attribution studies like this cannot prove that a specific death was caused by a specific exposure. What they can do is estimate, from known risk relationships, how much disease would not exist if the exposure disappeared. The work was funded by Bloomberg Philanthropies and the Gates Foundation.
Practical Takeaways
- Make the home and the car completely smoke-free rather than smoking near an open window, since the exposure that drives these numbers is largely domestic and children cannot remove themselves from it.
- If you live with a smoker and have unexplained chest symptoms or a cardiac risk assessment coming up, mention the exposure, because ischemic heart disease was the largest single share of the harm here at 12.0 million DALYs.
- Pay attention to indoor air where you live and travel, since exposure ranged up to 48.4 percent of the population in southeast Asia, east Asia, and Oceania, and indoor smoking rules vary enormously from one country to the next.
Related Studies and Research
- Nearly 9 in 10 US heart disease deaths are preventable
- PEPFAR put 20 million people on HIV treatment and prevented nearly 8 million infected births
- Red yeast rice may lower heart risks in people with metabolic syndrome
- A plant-based diet lowered heart disease risk over 20 years
FAQs
Is there a safe level of second-hand smoke exposure?
This analysis did not test a threshold, so it cannot answer that directly. What it does show is that the harm runs through the heart as well as the lungs, and the biology of coronary damage does not suggest a clean cutoff below which smoke is harmless. Practically, the useful question is not how little exposure is acceptable but whether the space someone spends the most hours in, usually the home, is smoke-free. Opening a window or smoking in the next room does not create a separate air supply.
Why does second-hand smoke hurt children differently than adults?
Children are not small adults when it comes to inhaled smoke. Their airways are narrower, their breathing rate is higher, and their immune systems are still developing, so a chest infection that an adult shrugs off can put a child in hospital. That shows up in the data: lower respiratory infections were the leading source of harm in children at 5.16 million DALYs, while heart disease led among adults. There are 767 million children aged 0 to 14 in the exposed group, and none of them chose the room they are in.
Why can exposure rates fall while the number of people exposed does not?
Because rates and totals answer different questions. Global age-standardized prevalence dropped 22.2 percent since 1990, but the absolute number of exposed people stayed flat, because the population underneath that share kept growing. In sub-Saharan Africa the head count actually rose 98.5 percent over the same period. Any progress claim based only on percentages is missing that.
Bottom Line
Second-hand smoke killed about 1.66 million people in 2023 and cost 44.8 million years of healthy life, with 2.71 billion people exposed worldwide, 767 million of them children. Ischemic heart disease was the largest single piece of that burden at 12.0 million DALYs, so this is a cardiovascular problem as much as a respiratory one. And while the exposure rate has fallen 22.2 percent since 1990, the number of people breathing it has not budged, which is the figure that matters to anyone living in a smoky house.
