Health risks associated with second-hand smoke

Second-hand smoke isn’t just irritating to the eyes, nose and throat; it is now clear from the growing weight of evidence that it poses a much more serious risk to our health.

Tobacco smoke contains around 4,000 chemicals, including arsenic, benzene, formaldehyde and ammonia. Around 60 of these chemicals are known or suspected to cause cancer. Many of the toxic chemicals are actually more concentrated in the smoke that's given off by the burning tip of a cigarette than in the smoke inhaled by the smoker through the filter.

By breathing in the smoke in the atmosphere, the non-smoker is exposed to many of the same health risks as the smoker, including:

Lung cancer

This is the best known risk to smokers and is also more common in people with long-term exposure to second-hand smoke. The Government's Scientific Committee on Tobacco and Health (SCOTH) concluded in 1998 that exposure to second-hand smoke increases the risk of lung cancer in non-smokers by around 20-30%.

Heart disease

Even though they inhale only 1% of the smoke, non-smokers exposed to second-hand smoke are at an increased risk of heart disease of around 25% (one study suggests it might be as much as 50%). Just 30 minutes of breathing second-hand smoke can reduce the coronary blood supply of a non-smoker to the same level as that of a smoker.


A study in New Zealand found that exposure to second-hand smoke increases the risk of stroke by 82% in non-smokers. This is a serious concern, as stroke is such a common condition.


Around 3.4 million people in the UK have asthma, and for most of these, tobacco smoke is a trigger for an asthma attack. For someone with asthma, just one hour of exposure to second-hand smoke can cause a 20% deterioration in lung function.

Risks to children's health

Children don't make up much of the workforce of course, but they may still spend quite a bit of time in other people's workplaces, such as schools, leisure centres, cafes or shopping centres. Children are even more at risk because of their smaller lungs and the fact that their bodies are still developing.

Second-hand smoking can also affect babies before they're even born - the toxins in the smoke get into the mother's bloodstream and reach the baby that way.

Breathing in second-hand smoke during pregnancy increases the risk of having a baby with a low birth weight. Small babies are at much greater risk of infections and other health problems.

Exposure to smoke before or after birth makes a baby:

  • twice as likely to suffer from colic;
  • more than twice as likely to get meningitis;
  • three times more at risk from cot death.

Older children exposed to cigarette smoke may suffer from delayed mental development, asthma and other respiratory infections, such as bronchitis, pneumonia or bronchiolitis, and middle ear infections (glue ear).


After reviewing all the available evidence, the latest report prepared for the Government by SCOTH has concluded that there is now no doubt that breathing in other people's smoke significantly increases the risk of cancer and heart disease, and advises that no infant, child or adult should be exposed to second-hand smoke. Click here to read the SCOTH report.

A recent review of international research on the immediate health impact of smoke-free workplace legislation found rapid and dramatic improvements. Air quality, respiratory health and levels of heart attacks and heart disease all improved substantially within months of the legislation being introduced.

Copyright © 2013 Public Health Agency. Designed and produced by the Public Health Agency.