Secondhand smoke | Updated: 2022-03-01
There are more than 7,000 chemicals in secondhand smoke. Of them 250 are are toxic and harmful, 70 of which can cause cancer.
What is secondhand smoke?

1. Secondhand smoke is the smoke from the burning of tobacco products, such as cigarettes, cigars or pipes and the smoke exhaled, or breathed out, by smokers. Exposure to secondhand smoke, even for a short time, can be harmful, especially to kids.
2. The majority of tobacco smoke is not inhaled into the lungs by smokers, but diffuses into the air to form secondhand smoke.
3. The toxicity of secondhand smoke per unit is four times that of firsthand smoke.
4. Secondhand smoke is a Group A carcinogen, containing about 70 kinds of carcinogenic substances.
5. The harmful ingredients of secondhand smoke can be absorbed on the surface of clothing, hair, carpets, sofas, curtains, car cushions and so on, resulting in “thirdhand smoke”, which is also a serious health threat.
6. Secondhand smoke is a main resource of indoor PM2.5. Compared with outdoor PM2.5, the indoor PM2.5 can hardly be detected but can be more harmful.
What health problems can secondhand smoke cause?

How secondhand smoke harms children
Because their bodies are still growing, infants and young children are especially vulnerable to health risks from secondhand smoke. Children cannot choose their own living environment and need more attention and protection.
Behavior disorders:
Children exposed to secondhand smoke for a long time have a 1.5 times higher risk of getting attention-deficit disorder, hyperactivity disorder and learning ability disorder than those who are not.
More vulnerable to diseases:
Children exposed to secondhand smoke for a long time are more vulnerable to malignant diseases such as asthma, bronchitis, pneumonia, allergic rhinitis and even leukemia.
Reduced learning ability:
Children exposed to secondhand smoke for a long time score lower on reading, math and puzzle tests than those who are not.
The height and weight of children exposed to secondhand smoke for a long time are lower than those who are not.
How secondhand smoke harms pregnant women 
The harmful substances of secondhand smoke can enter the fetal body through the placenta and affect the development of fetal heart and lung organs, as well as the digestive and central nervous systems.
Pregnant women exposed to secondhand smoke will:
Lead to low birth weight of infants;
Experience neural tube defects, cleft lips and palates, and other birth defects in infants;
Have a higher rate of spontaneous abortion or premature birth;
Experience more sudden neonatal death.
How secondhand smoke harms adults
Increases the risk of getting coronary heart disease by 25% - 30%;
Increases the risk of getting lung cancer by 20% - 30%;
Causes asthma, acute respiratory disease and chronic obstructive pulmonary disease;
Increases the risk of breast cancer in women.