Passive smoking, also known as secondhand smoke, refers to the inhalation of tobacco smoke by non-smokers who are in proximity to active smokers. Exposure to secondhand smoke is considered dangerous and a major public health concern. Numerous studies have shown that passive smoking can cause serious diseases and death in non-smokers. But how many people have actually died from the effects of passive smoking? Providing an accurate estimate is challenging, but public health experts agree the number is substantial.
Key Facts on Passive Smoking Deaths
- Secondhand smoke contains over 7,000 chemicals, hundreds of which are toxic and can cause cancer.
- There is no risk-free level of exposure to secondhand smoke.
- Even brief exposure can be harmful.
- Passive smoking increases the risk of heart disease, lung cancer, and other cancers.
- Children are especially vulnerable to the health effects.
- Bans on public smoking help reduce exposure and save lives.
These key facts indicate the lethality of passive smoking. But putting a number on passive smoking mortality requires analyzing epidemiological data and assessing attributable risk.
Estimates of Annual Passive Smoking Deaths
Various health organizations have attempted to quantify the annual passive smoking death toll:
- The World Health Organization (WHO) estimates that passive smoking causes over 600,000 premature deaths per year worldwide.
- The Centers for Disease Control and Prevention (CDC) estimates that secondhand smoke kills over 41,000 adults per year in the United States.
- The American Cancer Society (ACS) likewise estimates that secondhand smoke kills over 41,000 people per year in the U.S.
These figures clearly indicate that passive smoking leads to a huge number of preventable deaths each year, both globally and in the U.S. But how are these estimates derived?
Methodology for Estimating Passive Smoking Mortality
Calculating passive smoking deaths relies on epidemiological data and statistical modeling. Researchers determine the increased risk of disease from secondhand smoke exposure for never-smokers. Then they estimate the proportion of disease cases attributable to passive smoking based on secondhand smoke prevalence.
Some key steps in the methodology include:
- Meta-analyses of observational studies on the RR (relative risk) of disease for passive smokers vs non-exposed never smokers.
- Surveys on the prevalence and degree of secondhand smoke exposure in the population.
- Analysis of RR and exposure data using population attributable risk (PAR) methods.
- Applying the PAR percentages to mortality statistics to determine attributable deaths.
By following this process, scientists can systematically produce estimates on passive smoking mortality that policymakers can use to guide public health initiatives.
Data Sources on the Health Risks of Passive Smoking
The estimates on passive smoking deaths rely heavily on data from epidemiological studies examining the association between disease and secondhand smoke exposure. Some key sources of evidence include:
- Cohort studies – like the American Cancer Society’s Cancer Prevention Studies I and II, which followed over 150,000 never-smoking adults.
- Case-control studies – such as studies on lung cancer and heart disease among lifetime never-smoking women exposed to spousal smoking.
- Meta-analyses – pooled analyses of multiple studies, like a 2015 meta-analysis of 45 studies showing a 27% increase in lung cancer risk from exposure to a smoking spouse.
These and other epidemiological studies provide risk estimates used to calculate the disease burden of passive smoking. Longitudinal studies have also quantified the reductions in heart attacks following the implementation of smoke-free laws.
Health Effects Linked to Passive Smoking
Many adverse health effects are causally associated with exposure to secondhand tobacco smoke:
| Disease/Condition | Evidence of Risk From Passive Smoke |
|---|---|
| Lung Cancer | Conclusive evidence of significantly elevated risk, estimated at 20-30% higher for passive smokers. |
| Heart Disease | Clear evidence of increased risk of heart attack and heart disease mortality, estimated at 25-35% higher. |
| Stroke | Suggestive evidence of increased stroke risk from pooled data, perhaps 20-30% higher. |
| Breast Cancer | Limited suggestive evidence of increased risk, perhaps 20-40% higher for most exposure. |
This table outlines some of the major health consequences. Other effects include higher risks of asthma, COPD, reduced lung function, ear infections, bronchitis, pneumonia, SIDS, and low birth weight. Clearly, passive smoking has wide-ranging effects on health.
Risks Are Higher Among Vulnerable Groups
While any exposure to secondhand smoke is unhealthy, certain segments of the population face higher risks:
- Infants & children – More susceptible physiologically and with higher exposure rates.
- Pregnant women – Risks to the fetus like low birth weight.
- Elderly – Already higher risks for heart and lung diseases.
- Employees – Bartenders, waitstaff and others exposed occupationally.
- Those with Existing Conditions – Higher baseline risk makes smoke more dangerous.
Clearly, protections from secondhand smoke exposure are especially vital for these vulnerable groups. Workplace smoking bans and smoke-free public place laws help achieve this protection.
Declining Passive Smoking Deaths in the U.S.
The adoption of smoke-free laws and changes in social attitudes on smoking have led to declining rates of exposure to passive smoke in the U.S. and other countries. For example, CDC data shows the percentage of U.S. nonsmokers with detectable cotinine (a biomarker of smoke exposure) declined from 88% in 1988-1991 to 25% in 2015-2018.
As a result of reduced exposure, it is estimated there has been a meaningful decline in passive smoking deaths in recent decades:
- An analysis by researchers at UC San Francisco estimated passive smoking deaths declined from approximately 53,800 per year in 1990 to 41,300 in 2014.
- The decline correlated closely with reductions over this time period in the percentage of U.S. nonsmokers exposed to secondhand smoke.
- California saw one of the largest reductions in exposure thanks to strong statewide smoke-free legislation, with an estimated 26% drop in heart disease deaths attributable to secondhand smoke from 1990 to 2009.
These findings highlight that smoke-free laws and social change can tangibly improve public health by preventing passive smoking deaths. However, more progress is still needed, as over 40,000 deaths annually is still far too many.
Global Progress in Smoke-Free Policies
Many countries have also implemented smoke-free laws over the past decades:
- As of 2018, 38% of the world’s population was covered by comprehensive smoke-free laws, up from 15% in 2008.
- Smoke-free laws are especially prevalent in higher income countries, covering 55% of their populations versus only 21% in low-income countries.
- The WHO reports that 18 countries have successfully implemented nationwide smoking bans as of 2018, including the U.K., Spain, Turkey and Thailand.
However, only about half of the global population is protected by any kind of smoke-free legislation. Broad adoption of comprehensive laws in indoor public spaces and workplaces could prevent hundreds of thousands of passive smoking deaths worldwide.
Challenges in Reducing Passive Smoke Exposure
Despite the considerable progress, major challenges remain in reducing exposure to secondhand smoke:
- Many low and middle-income nations lack adequate smoke-free laws.
- Compliance and enforcement of laws remains inconsistent.
- Young children are still exposed at high rates in homes and cars.
- Certain occupations like casino workers still lack protection.
- Outdoor areas like parks and beaches often are exempted from laws.
Overcoming these challenges will require continued advocacy, policy change, public education campaigns, and resources devoted to implementing smoke-free initiatives, especially in LMICs.
The Future of Passive Smoking
The long-term outlook for passive smoking is positive overall, given the global policy trends:
- As more countries strengthen smoke-free laws and close loopholes, rates of exposure will continue declining.
- WHO projects that a high proportion of the global population may be covered by comprehensive laws by 2030.
- If current momentum continues, passive smoking could eventually become uncommon in many nations.
However, it will likely take decades before secondhand smoke exposure is eliminated completely. And the toll of passive smoking deaths will remain high for years absent accelerated policy change. Concerted efforts from governments and advocates are still needed to maximize the public health gains and save lives.
Conclusion
Passive smoking is a major preventable public health threat, responsible for an estimated 600,000 deaths annually worldwide. While research methods to quantify passive smoking mortality remain imperfect, there is ample evidence it leads to a huge disease burden. Encouragingly, global progress has been made in reducing secondhand smoke exposure through implementation of smoke-free laws and social change. However, over 40,000 deaths are still attributed annually to passive smoking in the U.S. alone, indicating that considerable work remains to protect public health. Through continued advocacy and policy initiatives, especially in LMICs, the future passive smoking death toll could be substantially reduced. But it will likely take many decades before the health risks of passive smoke are largely eliminated through persistent, comprehensive efforts.