Updated 24 January 2014

Secondhand smoke and its impact on children

Inhaling other people's smoke is known as passive, involuntary or secondhand smoking.

What is secondhand smoke?

Inhaling other people's smoke is known as passive, involuntary or secondhand smoking (SHS). Inhaling SHS is an unavoidable consequence of being in a smoke-filled environment. Secondhand smoke is a mixture of air-diluted ‘sidestream’ smoke from the burning tip of a cigarette, and the exhaled ‘mainstream’ smoke exhaled by the smoker.

Exposure to tobacco smoke

The World Health Organization (WHO) has estimated that nearly 700 million, or almost half the world’s children, are exposed to tobacco smoke by the 1.2 billion adults who smoke.(1)

It is well known that tobacco use leads to disease, and that SHS exposure is also harmful. There is no known safe level of exposure to secondhand smoke.(2)

According to the most recent estimates from the WHO, more than 600,000 people worldwide die prematurely every year of exposure to SHS. Of these attributable deaths, 28% occur in children.(2)

For young children, the major source of tobacco smoke is smoking by parents and other household members. Maternal smoking is usually the largest source of SHS because of the cumulative effect of exposure during pregnancy and also close proximity to the mother during early life.(1)

SHS in the home is a major source of exposure because children spend most of their time at home and indoors. Unlike adults who can choose whether or not to be in a smoky environment, children have little choice – they are far less likely to be able to leave a smoke-filled room if they want to.(1)

Children are more likely to start smoking if they grow up in households where those around them smoke.(1)

Health effects of SHS exposure

Children are especially vulnerable to SHS as they breathe more rapidly and inhale more pollutants per kilogram of body weight than adults.

A review by the World Health Organization concluded that passive smoking is a cause of bronchitis, pneumonia, reduced respiratory function (coughing and wheezing), asthma attacks, middle ear infection, cot death (sudden infant death syndrome [SIDS]), and possibly cardiovascular and neurobiological impairment (including deficits in reading and reasoning skills) in children.

Asthma is the most common chronic disease of childhood. Tobacco smoke exposure can trigger the development of asthma and exacerbate symptoms, and the prevalence of asthma increases with the number of smokers in the home.

Children who suffer from asthma and whose parents smoke, are at least twice as likely to suffer asthma symptoms all year round compared to children of non-smokers.(1)

An effective means of preventing asthma is to reduce exposure to SHS.

Health effects of prenatal exposure to SHS

Prenatal exposure to tobacco smoke has significant adverse impacts on the health of the foetus, including low birth weight (babies born to women who smoke weigh around 200 grams less than non-smokers), premature birth, spontaneous abortion and still birth.

In addition to this, prenatal exposure can have adverse impacts on the learning and behavioural development of a child. Maternal prenatal smoking is associated with both antisocial behaviour and attention deficit hyperactivity disorder (ADHD) in children and adolescents.

Smoking also impacts on In Vitro Fertilization (IVF) and fertility rates. It has been found that exposure to SHS is as damaging as smoking itself in terms of successful pregnancy outcomes for people using IVF.

1. Action on Smoking and Health. Research Report: Secondhand Smoke: the impact on children. [Internet]; April 2010 [cited 2013 April 2]. Available from:
2. Tanski SE, Wilson KM. Children and Secondhand Smoke: Clear Evidence for Action. Pediatrics 2012 January; 129(1):170-171

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