Secondhand smoke is a mixture of gases and fine particles that includes smoke from a burning product such as cigarettes, hookah or marijuana, or smoke that has been exhaled from a person who is smoking.
Non-smokers who breathe secondhand smoke inhale the same toxic chemicals as the smoker. The more smoke you breathe, the more harmful chemicals you will inhale. There is no risk-free level of exposure.
Secondhand smoke from cigarettes can cause or worsen many diseases, including pneumonia, asthma, bronchitis, and heart disease. Those who are exposed to high levels of smoke on a long-term basis are likely to develop chronic, potentially fatal diseases. Even brief exposure can cause health problems such as headaches, stuffy nose, irritation of the sinuses and eyes, coughing and can also trigger other breathing or heart problems.