Second-hand smoke exposed an estimated 2.71 billion people worldwide in 2023 and contributed to 1.66 million deaths, according to new findings from the Global Burden of Disease study.
The research, published in The Lancet Public Health, examined exposure to passive smoking and its health effects across 204 countries and territories between 1990 and 2023.
Children and women accounted for a large share of those exposed. The study estimated that 767 million children under the age of 15 were exposed to second-hand smoke in 2023, along with about 1.49 billion women.
Researchers said second-hand smoke remains a major cause of preventable illness and death among non-smokers. Exposure has been linked to heart disease, respiratory illnesses and several forms of cancer.
The findings also highlight gaps in efforts to protect people from tobacco smoke. Around 70% of the global population was not covered by comprehensive smoke-free laws as of 2024.
Only 79 countries had reached the highest level of protection under the World Health Organization’s tobacco control framework. These countries either had completely smoke-free public places or legislation covering at least 90% of their populations.
There has been progress over the past two decades. The proportion of the world’s population protected by comprehensive smoke-free legislation increased from just 3% in 2007 to 33% in 2024, covering about 2.6 billion people.
Researchers said smoke-free laws should be supported by other tobacco control measures, including higher tobacco taxes, restrictions on advertising, plain packaging and programmes that help smokers quit.
The global number of people exposed to second-hand smoke has remained broadly stable, but exposure has increased sharply in parts of sub-Saharan Africa, North Africa and the Middle East, largely because of population growth.
Central Europe, Eastern Europe and Central Asia recorded an exposure rate of 37.7%, above the global average of 33.9%. About 146 million people in the region were exposed.
Some high-income countries have recorded substantial progress. Denmark reduced exposure by 48.8% between 1990 and 2023, while Norway recorded a 44.3% reduction.
The health burden remains significant. The study estimated that second-hand smoke was responsible for 44.8 million years of healthy life lost globally.
Non-smokers can inhale sidestream smoke released directly from a burning cigarette as well as smoke exhaled by smokers. Researchers noted that sidestream smoke contains high concentrations of toxic and cancer-causing substances.
Exposure has been associated with stroke, lower respiratory infections, chronic obstructive pulmonary disease, asthma, type 2 diabetes and cancers affecting the trachea, lungs and breast.
The researchers said the findings underline the need for stronger tobacco control policies to protect people, particularly children, from exposure they cannot control.
