Most of secondhand smoke's estimated deaths were in non-smokers

Exposure to other people's tobacco smoke is an established cause of illness and death, yet it is easy to treat it as a background nuisance rather than a quantifiable health risk. Putting a number on the deaths a country can attribute to secondhand smoke tells policymakers, and the public, how much harm passive exposure still causes despite indoor smoking bans. This study set out to estimate that burden for Spain in 2020, in everyone aged 35 and over, for the diseases most clearly linked to smoke exposure.

The researchers applied an attributable mortality method that combines how common secondhand smoke exposure is with how much it raises disease risk. Exposure prevalence came from a representative Spanish study, while the relative risks came from a meta-analysis of earlier research. They estimated attributable deaths for every combination of sex, age group and cause of death, focusing on lung cancer and ischaemic heart disease, and split results by smoking habit. Uncertainty was quantified with statistical resampling, and a sensitivity analysis tested how robust the totals were.

An estimated 747 deaths in Spain in 2020 were attributable to secondhand smoke exposure: 279 from lung cancer and 468 from ischaemic heart disease. Three quarters of the attributable deaths, 75.1%, occurred in men, and notably 60.9% occurred in non-smokers, people harmed purely by other people's smoke. When chronic obstructive pulmonary disease and cerebrovascular disease were added to the calculation, the estimated burden rose to 2242 deaths. Overall, secondhand smoke exposure was associated with 1.5% of all deaths from lung cancer and ischaemic heart disease in this age group.

The harms of secondhand smoke are not in dispute; what this study adds is a current, country-level accounting of the death toll years after smoke-free legislation became normal in Europe. It confirms that passive exposure remains a measurable killer, and that the majority of its victims in this analysis never smoked. As a modelling exercise it inherits the limitations of its inputs: the exposure survey and the pooled risk estimates. The authors argue the findings justify continued efforts to reduce exposure in all settings and environments.

If you do not smoke, this is a reminder that the risk from tobacco is not entirely in your own hands: in this analysis most attributable deaths fell on non-smokers. That is a reason to take regular exposure seriously, whether in a shared home, a car or social settings where smoke lingers. None of this estimates your individual risk, but it does show that at a population level, breathing other people's smoke is still associated with real deaths from cancer, heart and lung disease.