You do not have to smoke a cigarette yourself to be harmed by tobacco smoke. For millions of Indians, exposure happens at home, at work, in public spaces or simply by being around someone who smokes. A new analysis from the Global Burden of Disease (GBD) Study 2023, published in The Lancet Public Health, has put the scale of this problem into sharp focus. The study estimates that 444 million people in India were exposed to second-hand smoke in 2023, making India the country with the second-highest number of exposed people globally, after China. More concerningly, 325,600 deaths in India were attributed to second-hand smoke in 2023, compared with 217,700 in 1990, an increase of almost 50%.

Globally, 2.71 billion people were exposed to second-hand smoke in 2023, including 767 million children aged 0-14 years. The exposure was associated with an estimated 1.66 million deaths and 44.8 million disability-adjusted life-years (DALYs).

India's passive smoking burden: What has changed?

The latest figures reveal an important contradiction. India's proportion of people exposed to second-hand smoke has actually fallen, but the absolute number of people exposed has increased.

The age-standardised prevalence of second-hand smoke exposure in India declined from 43.2% in 1990 to 30.6% in 2023. However, because India's population has grown substantially, the estimated number of people exposed rose from 375 million to 444 million over the same period.

The associated deaths increased from 217,700 to 325,600. Among women, estimated deaths rose from 113,400 in 1990 to 156,900 in 2023, while deaths among men increased from 104,300 to 168,700. The study estimated that second-hand smoke accounted for 9.28 million DALYs in India in 2023, representing years of healthy life lost because of premature death, illness or disability.

The findings do not mean that every death in these categories was caused solely by passive smoking. Rather, the GBD analysis estimates the health burden attributable to exposure to second-hand smoke at a population level.

What is second-hand smoke?

Second-hand smoke, also called passive smoke or environmental tobacco smoke, is the smoke inhaled by people around someone who is smoking. It includes smoke released from the burning end of a tobacco product as well as smoke exhaled by the smoker.

Tobacco smoke contains more than 7,000 chemicals, including hundreds that are toxic and dozens known to cause cancer. There is no established safe level of second-hand smoke exposure.

This means exposure is not simply an issue of being in a room filled with smoke for hours. Even short exposure can affect the cardiovascular and respiratory systems.

Passive smoking can affect the heart and brain

One of the most serious consequences of second-hand smoke is its effect on the cardiovascular system. The latest GBD analysis found ischaemic heart disease was the largest contributor to the overall second-hand-smoke disease burden.

Exposure can damage blood vessels, increase inflammation and make blood more likely to clot. According to the US Centers for Disease Control and Prevention (CDC), non-smokers exposed to second-hand smoke have a 25-30% higher risk of coronary heart disease and a 20-30% higher risk of stroke.

For people who already have heart disease, avoiding exposure becomes particularly important because even brief exposure can adversely affect the heart and blood vessels.

Lung cancer is not only a smoker's disease

Second-hand smoke is an established risk factor for lung cancer among people who have never smoked. The CDC estimates that non-smokers exposed to second-hand smoke have a 20-30% increased risk of developing lung cancer.

This is particularly relevant in India because lung cancer is increasingly being diagnosed in people who have never smoked. However, it is important not to attribute every lung cancer in a non-smoker to passive smoking. Other factors, including air pollution, occupational exposures, radon, genetic factors and other environmental risks, can also contribute.

Second-hand smoke should therefore be viewed as one preventable risk factor among several.

Children face a different level of risk

Children are particularly vulnerable because their lungs and immune systems are still developing. The latest global analysis estimated that 767 million children aged 0-14 years were exposed to second-hand smoke in 2023. Among children, lower respiratory infections represented the largest component of the health burden associated with second-hand smoke.

The CDC links childhood exposure with respiratory infections such as pneumonia and bronchitis, recurrent or severe asthma attacks, middle-ear disease, respiratory symptoms and slowed lung growth. Exposure during infancy is also associated with an increased risk of sudden infant death syndrome (SIDS).

For a child with asthma, tobacco smoke can be especially problematic because exposure can trigger attacks and make symptoms more frequent or severe.

Pregnancy is another critical window

Second-hand smoke exposure during pregnancy is also a concern. Exposure to tobacco smoke during pregnancy has been associated with adverse reproductive outcomes, including lower birth weight.

The WHO has also highlighted that tobacco exposure can affect reproductive health and notes that people do not necessarily have to smoke themselves to face risks from second-hand smoke.

For pregnant women, infants and young children, therefore, maintaining a completely smoke-free home and vehicle is particularly important.

Where are Indians being exposed?

India's own Global Adult Tobacco Survey (GATS) 2016-17 shows that the home remains a significant source of exposure. According to the Ministry of Health and Family Welfare, 35% of non-smokers were exposed to second-hand smoke at home. Among non-smokers who worked indoors, 26.2% were exposed at their workplace in the preceding 30 days.

The survey also found exposure among adults in public places, including public transport, restaurants, healthcare facilities and government buildings. Overall, 25.7% of adults reported exposure to second-hand smoke in at least one of the surveyed public settings.

These numbers underline why passive smoking cannot be treated simply as an individual choice made by a smoker. The exposure can extend to family members, colleagues and strangers.

Opening a window is not enough

One common misconception is that smoking near a window, balcony or exhaust fan makes indoor smoking safe for others.

It does not. The WHO states that there is no safe level of exposure to second-hand smoke and that completely smoke-free indoor environments are necessary to adequately protect people.

The most effective protection is therefore straightforward: do not smoke inside homes, cars or other enclosed spaces, and do not smoke around children, pregnant women or people with heart or lung disease.

The latest GBD findings offer an important reminder: the health consequences of tobacco do not stop with the person holding the cigarette.

India has made progress in reducing the proportion of people exposed to second-hand smoke, but the absolute number remains enormous. With an estimated 444 million people exposed and 325,600 deaths attributed to passive smoking in 2023, protecting non-smokers requires more than asking them to move away from smoke.

Smoke-free homes, cars, workplaces and public spaces remain among the most effective ways to reduce exposure. For smokers, quitting remains the best way to protect both their own health and the health of the people around them.

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