More than 2.7 billion people, including children, were exposed to second-hand smoke globally in 2023, contributing to nearly 1.7 million deaths, according to a study published today (8 September) in The Lancet.

Tobacco remains a leading cause of disease globally, the study said, noting that many non-smokers exposed to second-hand smoke were among the estimated 8 million people who died in 2023 from smoking-related illnesses.

“Exposure to second-hand smoke is a globally recognised health risk, with no safe level of inhalation,” it said.

Published today (8 September), the study reviewed research from the US National Institutes of Health’s PubMed database, along with population surveys, to estimate the prevalence of second-hand smoke exposure and quantify its health burden across 204 countries and territories between 1990 and 2023.

Among the approximately 2.7 billion people exposed to second-hand smoke in 2023 were 767 million children aged 0 to 14, the study found.

This exposure is estimated to have resulted in 1.66 million premature deaths and caused premature disability and illness, including ischemic heart disease, a condition caused by an insufficient supply of oxygen to the heart muscle.

In children, exposure to second-hand smoke is estimated to have caused 5.2 million respiratory tract infections in 2023, it said.

People in close proximity to someone smoking are exposed to both “sidestream smoke” from the burning tobacco product and smoke exhaled by the active smoker, the study explained.

“The sidestream component, which dominates the air non-smokers breathe, is unfiltered, carrying higher per-unit concentrations of toxic and carcinogenic compounds than those inhaled by the active smoker,” it said.

Despite significant declines in smoking prevalence globally since 1990, the absolute number of people exposed to second-hand smoke has remained stable due to population growth and increased exposure in Africa and the Middle East.

Women are also disproportionately affected by second-hand smoke, particularly in regions where smoking prevalence among women is low, the study noted.

“Despite this substantial burden, second-hand smoke exposure remains rarely acknowledged as a major risk factor for women’s health,” it said.

The study called on governments to implement stronger tobacco controls in public places and homes to better protect women and children from second-hand smoke.