Is passive smoking harmful?

Yes. Breathing in someone else's cigarette smoke (passive smoking or secondhand smoking) can increase your risk of cancer and other health problems. It is also particularly harmful for children.

Smoke stays in the air

When someone smokes a cigarette, the smoke from the burning tip is released into the air. So is the smoke they breathe out. Smoke can stay in the air for up to two and a half hours, even with a window open. It may still be there even if you can't see it or smell it.

This also applies in small enclosed places, such as cars. Smoke may still be present in large amounts even after the person has stopped smoking.

Risks of passive smoking

Passive smoking can damage your body because secondhand smoke contains more than 4,000 chemicals, many of which are irritants and toxins, and some of which are known to cause cancer. Passive smoking from all forms of tobacco is harmful, including: 

  • cigarettes
  • cigars
  • pipe tobacco
  • hand-rolling tobacco
  • shisha pipes (also called hookahs or waterpipes)

Frequent exposure to other people's smoke can increase your risk of lung cancer, even if you're a non-smoker. Passive smoking also increases your risk of coronary heart disease. Coronary heart disease can cause a heart attack, angina (chest pain) and heart failure. It also increases your risk of stroke

Children and passive smoking

Breathing in secondhand smoke is particularly harmful for children. Children who breathe in secondhand smoke have an increased risk of:

Children who grow up with a parent or family member who smokes are three times as likely to start smoking themselves.

If you're a parent who smokes, it will be hard to explain to your children why they shouldn't start smoking. Try to lead by example and quit. As well as improving your health and theirs, your children may be less likely to start smoking later in life. See below for where to get support.

Smoking and the law

In July 2007, smoking in public places such as bars, restaurants and workplaces was made illegal to protect non-smokers from the health risks associated with passive smoking.

Stopping smoking

Read more about treatment and support to quit smoking, as well as advice on ways to quit when you're preparing to stop.

Your GP can also give you advice about quitting smoking and NHS stop smoking support services through Go Smokefree.

Read the answers to more questions about stopping smoking.

Further information:

Page last reviewed: 17/03/2014

Next review due: 17/03/2016