Second-hand smoke is a mix of smoke from a burning cigarette, pipe or cigar, plus the smoke exhaled by the person smoking. This smoke is harmful to the health of both smokers and non-smokers, including children.
Firsthand smoking and secondhand smoke both cause serious health effects. While directly smoking is worse, the two have similar adverse health effects.
Secondhand smoke is also called:
side-stream smoke
environmental smoke
passive smoke
involuntary smoke
Nonsmokers who inhale secondhand smoke are affected by chemicals contained in the smoke.
Exposure to secondhand smoke occurs anywhere someone might be smoking. These places can include:
bars
cars
homes
parties
recreational areas
restaurants
workplaces
Effects in adults
Cardiovascular diseases
Respiratory diseases
Lung cancer
Other cancers
breast cancer
leukemia
lymphoma
Effects in children
Lung health effects. This includes delayed lung development and asthma.
Respiratory infections. Children exposed to secondhand smoke have more frequent infections. Pneumonia and bronchitis are the most common.
Ear infections. These often occur in the middle ear and are frequent in nature.
Worsening asthma symptoms, such as coughing and wheezing. Children with asthma might also be privy to asthma attacks from frequent secondhand smoke exposure.
Constant cold or asthma-like symptoms. These include coughing, wheezing, and shortness of breath, as well as sneezing and runny nose.
Brain tumors. These might develop later in life, too.
If you’re around tobacco smoke, the only way you can fully eliminate exposure is by leaving the affected place entirely.
Source: Healthline