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Middlesex-London Health Unit

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Health Effects of Second-Hand Smoke

Second-hand smoke hurts everyone; there is no safe level and it can be harmful even when you can’t see or smell it.1


  • Second-hand smoke can affect our bodies very fast and as we grow there are several harmful effects that regular exposure can put our bodies at risk for.2
  • For every eight smokers that die from smoking related illness, one non-smoker will die from exposure to second-hand smoke.1
  • Unborn babies, infants and children have little control over their exposure to second-hand smoke.1

Unborn Babies

Unborn babies are exposed to second-hand smoke through the mom. Everything the mom drinks, eats and breathes is passed to the baby through an organ called the placenta. This means that if the mom breathes in second-hand smoke all the chemicals she breathes go right to the baby.6 7

  • Nicotine can decrease blood flow to the baby and can affect the baby’s heart, lungs, digestive system and central nervous system.1
  • Carbon monoxide (CO) can affect the baby’s growth and may lead to low birth weight.1 3 4 5
  • Second-smoke exposure can also increase the chances of miscarriage, stillbirth, premature birth and problems with the placenta.1 3 4 5
  • Quitting smoking during pregnancy will have positive health effects within minutes for both you and your baby. Talk to your health care provider about methods for quitting smoking.6 7

If you are unsure how to start this conversation, Pregnets has information on how to talk to your health care provider about smoking.

Infants and Children

Infants and children are at a greater risk to second-hand smoke exposure because their bodies and organs are still growing.1 2 5

This means that:

  • Because their lungs are small they breathe faster and may inhale more air and pollutants.1 2
  • Their immune system is still developing and they are less able to protect against harmful second-hand smoke.1 2
  • They are at a greater risk of dying from Sudden Infant Death Syndrome (SIDS) also known as crib death.1 2 3 5
  • They may develop more frequent middle ear infections and lower respiratory tract problems, such as coughs, pneumonia, bronchitis, and croup.1 2
  • They have a greater chance of developing asthma, asthma attacks, and allergies.1 2
  • Recent studies show children exposed to second-hand smoke had lower test scores when compared to children who were not exposed.1
  • They may miss more days of school due to illness.1

Not only are there physical effects of second-hand smoke but there are also social effects such as role modeling.1

  • If children see their family, friends, coaches, teachers or even celebrities using tobacco they are more likely to start.1


An adult non-smoker living with someone who smokes is exposed to as much danger from second-hand smoke as the person who is smoking.8

Being exposed to second-hand smoke causes:

  • Damage to the lungs, heart1, blood vessels, and circulation5 causing breathing problems (coughing, worsening of asthma)1 9 increased heart rate, increased blood pressure and blood clots.2
  • Increases the risk of developing lung cancer, heart disease, and pre-menopausal breast cancer.1
  • Premature death.1 9


Animals are exposed to second-hand in the same way as humans, but not only do animals inhale second-hand smoke they can also ingest chemicals.2 10

  • Harmful particles remain in animal fur, which can be ingested while grooming with their tongues.2 10
  • Animals are at risk for certain types of cancer such as leukemia, lung cancer, and nasal cancer,2 10 and some animals can also develop allergies.10

Additional Information

For more information, please contact the Middlesex-London Health Unit Tobacco Control Team

Date of creation: February 27, 2013
Last modified on: March 31, 2015


1Smoke-Free Ontario Scientific Advisory Committee. (2010). Evidence to Guide Action: Comprehensive Tobacco Control in Ontario. Retrieved from
2Health Canada. (2008). Make your home and car smoke-free: A guide to protecting your family from secondhand smoke. Retrieved from
3World Health Organization. (2010). Gender, Women, and The Tobacco Epidemic. Chapter 9. Retrieved from
4Greaves, L., Poole, N., Okoli, C. T. C., Hemsing, N., Qu, A., Bialystok, L., & O’Leary, R. (2011). Expecting to Quit: A best practices review of smoking cessation interventions for pregnant and post-partum women (2nd ed.).Vancouver: British Columbia Centre of Excellence for Women’s Health. Retrieved from
5American Cancer Society. (2013). Second-Hand Smoke. Retrieved from
6Health Canada. (2009). Health concerns: Quitting and pregnancy: The sooner you quit, the better for your baby. Retrieved from
7Centre for Addiction and Mental Health. (2013). Second Hand Smoke. Retrieved from
8World Health Organization. (2002). Tobacco Smoke and Involuntary Smoking: Summary of Data Reported and Evaluation. International Agency for Research on Cancer (IARC) Monographs on the Evaluation of Carcinogenic Risks to Humans, Volume 83. Retrieved from
9Government of Canada. (2013). Health Risks from Second-Hand Smoke. Retrieved from
10Bertone, E.R., Snyder, L. A., & Moore, A.S. (2002). Environmental Tobacco Smoke and Risk of Malignant Lymphoma in Pet Cats.American Journal of Epidemiology Vol. 156 (3), 268-273.