How can indoor tobacco smoke affect the lungs of nonsmokers?

Created from Britannica articles using AI. AI can make mistakes, so verify using Britannica articles.

Medical illustration of the human chest showing the lungs, diaphragm, ribs, trachea, bronchus, and bronchioles, with one lung cut away to reveal internal structures. — respiratory disease The bronchioles of the lungs are the site where oxygen is exchanged for carbon dioxide during the process of respiration. Inflammation, infection, or obstruction of the bronchioles is often associated with acute or chronic respiratory disease, including bronchiectasis, pneumonia, and lung abscesses.

Indoor tobacco smoke, known as secondhand smoke, poses significant risks to the lungs of nonsmokers. It contains approximately 7,000 chemicals, including nearly 70 known carcinogens, which primarily increase the risk of lung cancer.1

Beyond cancer, these chemicals irritate the respiratory tract, triggering allergy-like symptoms such as coughing, wheezing, and shortness of breath. This exposure can lead to bronchial hyperreactivity, where airways become overly sensitive to irritants and constrict. These effects are particularly dangerous for individuals with pre-existing conditions like asthma or chronic obstructive pulmonary disease (COPD), as secondhand smoke can exacerbate these illnesses or increase the risk of developing new respiratory damage.1

Because toxins in environmental smoke diffuse easily across indoor spaces, exposure remains a serious health concern in shared environments. Protecting nonsmokers from these harmful substances is a critical public health priority to prevent avoidable respiratory and cardiovascular harm.1