Exposure to second-hand smoke remains a major global public health concern. A new study published in The Lancet Public Health as part of the Global Burden of Disease (GBD) 2023 study estimates that second-hand smoke exposure was responsible for 1.66 million deaths and 44.8 million disability-adjusted life years (DALYs) among non-smokers in 2023.
Led by researchers from the Institute for Health Metrics and Evaluation (IHME) at the University of Washington, the study involved more than 2,000 researchers worldwide, including Joan B. Soriano, epidemiologist at the University of the Balearic Islands, pulmonologist at Hospital Universitario de La Princesa, and collaborator of the CIBERES research group co-led by the ICO Tobacco Control Unit. It is the first dedicated GBD publication to assess both the prevalence of second-hand smoke exposure and its health burden across 204 countries and territories between 1990 and 2023.
More than 2.7 billion people exposed worldwide
According to the study, an estimated 2.71 billion people were exposed to second-hand smoke in 2023. Of these, 1.49 billion were women and 767 million were children aged 0–14 years, two population groups that experience a particularly high share of the health burden associated with involuntary tobacco smoke exposure.
The highest levels of exposure were found in Southeast Asia, East Asia and Oceania, where almost half of the population is exposed to second-hand smoke. China, India and Indonesia alone account for nearly half of all people exposed worldwide.
Cardiovascular and respiratory diseases drive the burden
The analysis examined nine health conditions linked to second-hand smoke exposure: ischaemic heart disease, stroke, chronic obstructive pulmonary disease (COPD), lower respiratory infections, lung cancer, breast cancer, type 2 diabetes, otitis media and asthma. Asthma was included for the first time as a health outcome attributable to second-hand smoke within the GBD framework.
Globally, ischaemic heart disease was the leading contributor to the disease burden attributable to second-hand smoke, accounting for around 12 million DALYs. Among children, lower respiratory infections represented the greatest health impact, contributing more than 5 million DALYs.
The situation in Spain
According to Joan B. Soriano, approximately one in every three people in Spain continues to be exposed to second-hand smoke. The study estimates that 14.3 million people are exposed nationwide, corresponding to 35.4% of the population. Of these, 6.8 million are women and 7.5 million are men.
Soriano also highlights that children are among the groups most vulnerable to the effects of second-hand smoke because their lungs and immune systems are still developing, making them particularly susceptible to tobacco smoke exposure.
Implications for tobacco control policies
The findings provide further evidence of the need to strengthen tobacco control measures and better protect non-smokers from involuntary exposure to tobacco smoke.
In Spain, the study adds support to the proposed expansion of smoke-free environments included in the forthcoming reform of the national tobacco control law. The proposal would extend smoking and vaping restrictions to a range of outdoor settings, including restaurant and café terraces, beaches, playgrounds, outdoor sports facilities, public transport stops and stations, educational campuses and work vehicles.
According to the authors, reducing exposure to second-hand smoke remains one of the most effective ways to prevent disease and protect public health. This is particularly important for women and children, who continue to bear a disproportionate share of the burden associated with this entirely preventable exposure.