Study: Second-hand smoking on the rise in Africa

 2.71 billion people worldwide were exposed to second-hand smoke in 2023.[Courtesy]

You do not have to light a cigarette to inhale its smoke. Sitting beside a smoker, sharing a room with someone who smokes or growing up in a household where tobacco is used can expose you to the same toxic smoke, even when you have never touched a cigarette yourself.

A new study published in The Lancet Public Health shows just how widespread that invisible exposure remains. The Global Burden of Disease Study 2023 analysed second-hand smoke exposure and its health effects across 204 countries and territories between 1990 and 2023, using data on different age groups and sexes.

Researchers estimated exposure to combustible tobacco smoke at home and in workplaces among non-smokers and occasional smokers, then assessed its contribution to nine health outcomes.

The findings are sobering. In 2023, about 2.71 billion people worldwide were exposed to second-hand smoke, including 767 million children aged 0-14 years. Although the age-standardised prevalence of exposure had fallen by 22.2 per cent since 1990, population growth kept the overall number of exposed people broadly stable.

In some parts of the world, the situation moved in the opposite direction. In sub-Saharan Africa, the absolute number of people exposed increased by 98.5 per cent between 1990 and 2023.

That makes the findings particularly relevant to African countries, including Kenya. The study does not suggest that every country in the region experienced the same increase, and its country-level estimates are presented separately in the supplementary appendix.

However, the regional trend highlights a growing challenge: reductions in smoking prevalence do not automatically translate into fewer people being exposed to tobacco smoke, especially where populations are growing and smoke-free protections are unevenly enforced.

The health consequences extend far beyond an unpleasant smell on clothes. The researchers estimated that second-hand smoke contributed to 1.66 million deaths globally in 2023 and was responsible for 44.8 million disability-adjusted life-years, a measure combining years of healthy life lost through premature death and disability.

Ischaemic heart disease was the largest contributor to the disease burden. Among children, lower respiratory infections accounted for the largest share.

Second-hand smoke is a mixture of smoke released from the burning end of a tobacco product and smoke exhaled by the smoker. The smoke contains toxic and carcinogenic substances that can trigger inflammation and damage the cardiovascular and respiratory systems.

Children are especially vulnerable because their lungs and immune systems are still developing. The new study also expands the evidence base by including asthma among the health outcomes examined.

Women also emerge as an important group in the findings. Globally, about 1.49 billion females were estimated to have been exposed to second-hand smoke in 2023, and the study found that women in some countries experienced substantially higher exposure than men.

This can happen in settings where smoking is more common among men, leaving women and children exposed at home despite not using tobacco themselves.

For Kenyan households, this distinction matters. Tobacco exposure does not stop at the smoker. A parent who smokes inside the house can expose children, a spouse or other relatives. The same principle applies in workplaces and other enclosed environments.

The study notes that its estimates primarily capture exposure at home and at work rather than every setting, meaning the full range of people’s exposure may be broader than what is measured.

Kenya already has measures intended to protect people from tobacco smoke. The country has reported a national smoke-free policy covering public places, supported by penalties. Kenya also gazetted a total ban on shisha in 2024.

Protecting people from second-hand smoke requires more than rules on paper. Enforcement, public awareness and behaviour in homes all matter.

Reducing exposure also means helping people who smoke to quit. Kenya began revising its National Tobacco Cessation Guidelines with technical support from WHO. The revised approach includes routine brief advice from health workers, behavioural counselling, digital cessation tools and medicines that can help people stop using tobacco.

The new Lancet Public Health study therefore points to a problem that cannot be solved simply by asking non-smokers to keep their distance. The responsibility also lies with smokers, households, workplaces, communities and governments to create environments where people are not involuntarily exposed.

For someone who smokes, quitting is the most direct way to protect both their own health and the people around them. For households, keeping indoor spaces completely smoke-free is a practical step. For parents, avoiding smoking around children is particularly important. For workplaces and public facilities, enforcing smoke-free rules protects people who have no control over whether someone nearby chooses to smoke.

The message from the study is simple: a cigarette may belong to one person, but its smoke does not. For billions of people around the world, including children who have never chosen to smoke, that distinction can have lifelong consequences.