Second-hand smoke still reaches billions, and the burden has not shifted quietly
In 2023, second-hand smoke exposure remained one of the world’s most pervasive preventable risks, affecting an estimated 2.71 billion people across 204 countries and territories. The global count included 767 million children aged 0 to 14 years, a figure that makes the household and community reach of tobacco smoke impossible to dismiss as a marginal exposure problem. Even after decades of tobacco control, passive smoke continues to move through homes, workplaces, public spaces, and multigenerational living arrangements with measurable consequences for survival and disability.
The analysis, built within the Global Burden of Disease 2023 comparative risk assessment framework, is the first dedicated GBD publication to quantify SHS prevalence and the disease burden attributable to it at global, regional, and national levels. Exposure estimates were assembled from population-based surveys and household composition data using spatiotemporal Gaussian process regression. Relative risks for nine health outcomes, now including asthma, were then applied to deaths and disability-adjusted life-years, giving the study both reach and clinical specificity. The result is not a single headline number but a burden map that follows smoke into the outcomes clinicians see every day.
Cardiovascular disease carried the largest adult toll
In 2023, SHS exposure accounted for 1.66 million deaths and 44.8 million disability-adjusted life-years worldwide. Ischaemic heart disease contributed the largest share of SHS-attributable DALYs overall, at 12.0 million, placing cardiovascular injury at the center of the passive smoking burden. The pathophysiology is straightforward and unforgiving: tobacco smoke exposure promotes endothelial dysfunction, oxidative stress, platelet activation, and inflammatory vascular injury, all of which accelerate atherosclerotic plaque instability and coronary events even in people who never smoke themselves.
This pattern matters because passive smoke is often treated as a diffuse environmental irritant rather than a major cardiovascular exposure. The burden estimates argue otherwise. When a risk factor contributes millions of DALYs through coronary disease alone, prevention stops being an abstract public health ideal and becomes a matter of real-time vascular injury prevention.
Children bore a disproportionate respiratory burden
Among children, lower respiratory infections were the dominant SHS-attributable outcome, accounting for 5.16 million DALYs. This finding aligns with the known vulnerability of the pediatric airway, where smaller caliber bronchi, developing immune defenses, and repeated exposure in enclosed domestic settings amplify harm from tobacco smoke particles and gases. The study also incorporated asthma among the evaluated outcomes, widening the respiratory picture beyond infection alone.
The numbers point to a domestic exposure problem as much as a societal one. Children rarely control where smoke enters their environment, and the burden data suggest that the airway injury begins long before chronic disease is diagnosed. Recurrent respiratory illness in childhood can mean missed school, repeated clinical visits, caregiver strain, and a cumulative respiratory disadvantage that extends well beyond the acute episode.
Exposure fell in rate, not in absolute human terms
Global age-standardised SHS prevalence declined by 22.2% since 1990, with a 95% uncertainty interval of 10.6% to 32.4%. Yet the absolute number of exposed people remained stable worldwide. In practical terms, population growth has erased much of the gain from declining prevalence rates. Lower percentages do not help when the total number of exposed people is still measured in billions.
The regional pattern was especially stark. Age-standardised prevalence was highest in southeast Asia, east Asia, and Oceania at 48.4%, and female individuals in some countries experienced nearly 1.8 times the exposure prevalence of male individuals. The sex gap suggests that social structure, household smoking patterns, and differential time spent in enclosed environments may continue to place women at higher risk in some settings. Public policy that focuses only on public venues misses this domestic asymmetry.
Several regions saw exposure numbers surge despite global progress
The most troubling signal in the analysis was the rise in absolute numbers of exposed individuals in specific regions. Sub-Saharan Africa recorded a 98.5% increase in exposed people, while North Africa and the Middle East showed a 72.1% increase. Those rises occurred even as the global age-standardised prevalence declined, illustrating how demography, urban growth, household structure, and uneven tobacco control can outpace gains in risk reduction.
A declining rate can therefore conceal a worsening count. Health systems planning around prevalence alone may miss the rising clinical load generated by population expansion and persistent exposure in vulnerable communities. The burden is no longer concentrated only where smoking is common; it is also concentrated where health protections are least comprehensive.
Tobacco control needs to reach the places smoke still hides
The interpretation is direct: SHS remains a substantial driver of global health loss, particularly through cardiovascular disease and paediatric respiratory illness. The data support stronger enforcement of comprehensive tobacco control measures, especially those that protect women and children in both public and domestic environments. Smoke-free laws, household cessation support, and stronger restriction of indoor smoking are not symbolic interventions here. They are mechanisms that prevent endothelial injury, childhood infection, and avoidable death.
Because the analysis spans 1990 to 2023 across 204 countries and territories, it offers a long view of progress and failure at once. Some settings have reduced exposure substantially, but the global burden remains large enough to demand renewed urgency. The challenge is no longer establishing that second-hand smoke is harmful. The remaining task is closing the gap between evidence and enforcement in places where exposure still persists, especially where children and women continue to carry the heaviest unseen load.