Medical advice: Effects of Passive smoking


Most of the smoke that hangs in a room is sidestream smoke, which contains higher levels of cancer-causing compounds than mainstream smoke. Second-hand smoke is a common indoor pollutant in the home, making passive smoking a serious health risk for both smokers and non-smokers. Children are particularly at risk of serious health effects from second-hand smoke.


Irritant effects

Tobacco smoke inside a room tends to hang in mid-air rather than disperse. Hot smoke rises, but tobacco smoke cools rapidly, which stops its upward climb. Since the smoke is heavier than the air, the smoke starts to descend. A heavy smoker who smokes indoors causes a permanent low-lying smoke cloud that other householders have no choice but to breathe.


Tobacco smoke contains around 4,000 chemicals, made up of particles and gases, over 50 of which are known to cause cancer. Second-hand smoke has been confirmed as a cause of lung cancer in humans by several leading health authorities. Compounds such as ammonia, sulphur and formaldehyde irritate the eyes, nose, throat and lungs. These compounds are especially harmful to people with respiratory conditions such as bronchitis or asthma. Exposure to second-hand smoke can either trigger or worsen symptoms.


Health risks to children

Children are especially vulnerable to the damaging effects of second-hand smoke. Some of the many health risks include:

  • Passive smoking is a cause of sudden unexpected death in infancy (SUDI), which includes sudden infant death syndrome (SIDS) and fatal sleep accidents.
  • A child who lives in a smoking household for the first 18 months of their life has an increased risk of developing a range of respiratory illnesses including wheeze, bronchitis, bronchiolitis and pneumonia. They are also more prone to getting colds, coughs and middle ear infections. Their lungs show a reduced ability to function and slower growth.
  • A child exposed to second-hand smoke in the home is more likely to develop asthma symptoms, have more asthma attacks and use asthma medications more often and for a longer period
  • School-aged children of smokers are more likely to have symptoms such as cough, phlegm, wheeze and breathlessness
  • Children of smokers have an increased risk of meningococcal disease, which can sometimes cause death or disability


Health risks to partners who have never smoked

People who have never smoked living with partners who smoke, are at increased risk of a range of tobacco-related diseases.


  • Passive smoking increases the risk of heart disease. There is consistent evidence that non-smokers married to smokers have higher risks of coronary heart disease than those whose spouses do not smoke.
  • Passive smoking makes the blood more ‘sticky’ and likely to clot. There is evidence that levels of antioxidant vitamins in the blood are also reduced.
  • Just 30 minutes of exposure to second-hand smoke can affect how your blood vessels regulate blood flow to a similar degree that is seen in smokers.
  • Long-term exposure to passive smoking may lead to the development of atherosclerosis (narrowing of the arteries).
  • Non-smokers who suffer long-term exposure to second-hand smoke have a 20 to 30 per cent higher risk of developing lung cancer.
  • There is increasing evidence that passive smoking can increase the risk of stroke, nasal sinus cancer, throat cancer, breast cancer, long and short-term respiratory symptoms, loss of lung function, and chronic obstructive pulmonary disease among non-smokers.


Reducing the risk of passive smoking

If the smoker is unwilling or unable to stop right now, there are various ways to help protect the health of their partner and children. Suggestions include:

  • Make your home smoke-free. Limiting smoking to one or two rooms in your house is an ineffective measure as tobacco smoke easily drifts through the rest of the house.
  • Make sure that smokers who visit the house smoke their cigarettes outdoors, no matter what the weather. If they object or take offence, try calmly explaining the health risks of passive smoking, and point out that you simply want to protect the health of your family.
  • Make your car smoke-free. The other occupants will still be exposed to tobacco smoke even if the windows are open.
  • Don’t allow smoking in any enclosed space where your partner or children spend time – for example inside a shed, or storage room.
  • Try to avoid taking your children to outdoor areas where people are smoking and you can’t easily move away.
  • Make sure that all people who look after your children (for example, grandparents or babysitters) provide a smoke-free environment.

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