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Smoking and cancer: Second-hand smoke

Second hand smoke can cause cancer. Breathing in other people's smoke can cause cancer. Second-hand smoke can increase a non-smoker's risk of getting lung cancer by a quarter, and may also increase the risk of cancers of the larynx (voice box) and pharynx (upper throat).

Second-hand smoke can cause other health problems too, including heart disease, stroke and breathing problems. Even 30 minutes of exposure to second-hand smoke can reduce blood flow in a non-smoker’s heart. Every year, second-hand smoke kills about 11,000 people in the UK from lung cancer, heart disease and strokes.

For more information about the evidence that links second-hand smoke to cancer, go to our How do we know section.

Second-hand smoke and children

Second-hand smoke is particularly dangerous for children because their bodies are still developing. Smoking when you are with your children can increase their risk of cot death, glue ear, respiratory illnesses such as asthma and chest infections, and possibly cancer later on in life.

A study by the Royal College of Physicians showed that about 17,000 children in the UK are admitted to hospital every year because of illnesses caused by second-hand smoke.

Over forty percent of children in the UK live in a household where at least one person smokes. If you are a smoker, try not to expose your child to your smoke.

The chemicals in second-hand smoke

There are two types of tobacco smoke:

  • mainstream smoke, which is directly inhaled through the mouth end of the cigarette, and
  • sidestream smoke, which comes from the burning tip of the cigarette.

Second-hand smoke consists mainly of sidestream smoke, which is about four times more toxic than mainstream smoke, although people inhale it in a more diluted form. This is because sidestream smoke contains much higher levels of many of the poisons and cancer-causing chemicals in cigarettes, including:

Smoking in public places

In February 2006, MPs voted by a massive majority to make public spaces, including pubs and private members' clubs, smokefree. This move will help to protect workers from the harmful effects of second-hand smoke and has been hailed as a large advance in public health.

Since the ban was brought into place, England has seen the largest ever fall in smoking rates. In the first year of the ban, about 400,000 people quit smoking and scientists have estimated that the new laws will prevent about 40,000 deaths from smoking-related diseases over the next decade.

Our Policy section has more information on the vote for smokefree public places, Cancer Research UK's view on smokefree legislation, and the dangers of second-hand smoke.

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Updated: 25 September 2009