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Can Pets Get Cancer from Owners’ Smoking?

By Jennifer Coates, DVM


The Dangers of Second Hand Smoke for Pets


You must have been living on a desert island for the last few decades if you are not aware of the danger that smoking poses both to smokers and to the people who come in contact with second hand smoke. Less well known, however, is the effect that a smoke filled home can have on pet health.


First some definitions. Second hand smoke is smoke that is exhaled or otherwise escapes into the air and can then be inhaled by non-smokers, including pets. Third hand smoke is the residue from smoke that remains on skin, fur, clothing, furniture, etc. even after the air has cleared. Both second and third hand smoke can be referred to using the term “environmental tobacco smoke,” or ETS.


Now let’s take a look at the scientific studies that reveal a link between environmental tobacco smoke and serious diseases in cats and dogs.


The Effects of Tobacco Smoke on Cats


A study published in 2002 demonstrated a greatly increased risk of malignant lymphoma (also called lymphoma or lymphosarcoma) in cats with exposure to ETS. The relative risk for malignant lymphoma in cats with any household ETS exposure was almost 2 ½ times higher than that seen in cats who lived in smoke-free households.


For cats with five or more years of ETS exposure, the relative risk climbed to 3.2. In other words, these poor cats were more than three times as likely to develop lymphoma as were cats who lived in a home where no one smoked.


This study and others also strongly suggest a link between oral cancers in cats and third hand smoke. It is thought that cats groom the toxins contained in tobacco smoke out of their fur, which damages tissues in their mouths. This eventually leads to oral cancer.


The Effects of Tobacco Smoke on Dogs


Dogs can become seriously ill after long term exposure to second and third hand smoke as well. Two studies, one published in 1992 and the other in 1998, determined that cancer of the respiratory tract was more common in dogs who were exposed to environmental tobacco smoke. Interestingly, the type of cancer the dogs got was influenced by the shape of their heads.


The risk of nasal cancer increased by 250% when dogs with long noses (picture a Collie) were exposed to tobacco smoke. On the other hand, dogs with short or medium noses tended to develop lung cancer under similar conditions.


When you think about it, these findings aren’t all that surprising. The extensive nasal passages of long-nosed dogs are good at filtering out the toxins contained in cigarette smoke, which protects the lungs to the detriment of the nose. These same toxins pass right through the relatively shorter noses of other dogs and then become lodged in and damage the lungs.


Many other studies underline the damage that tobacco smoke does to the lining of the respiratory tract and a possible link to non-cancerous diseases such as chronic bronchitis and asthma.


Do Alternatives Help?


By now you might be thinking, “I’ll just smoke outside.” While direct research into the effect that outdoor smoking has on pet health hasn’t been performed, we can look at a 2004 study on infants and draw some conclusions. It found that smoking outside of the home helps but does not eliminate smoke exposure to babies. The infants of parents who smoked outdoors but not inside were still exposed to 5-7 times as much environmental tobacco smoke in comparison to the infants of nonsmokers. Similar results could be expected for pets.


And what about vaping? Again, no direct research into the health effects of second and third hand vaping solution on pet health has been done, but according to the American Lung Association:


In 2009, the FDA conducted lab tests and found detectable levels of toxic cancer-causing chemicals, including an ingredient used in antifreeze, in two leading brands of e-cigarettes and 18 various cartridges. A 2014 study found that e-cigarettes with a higher voltage level have higher amounts of formaldehyde, a carcinogen.


It’s hard to imagine that inhaling substances like these or licking them off their fur could be completely risk free for pets.




Looking at the science brings us to the inevitable conclusion that second and third hand smoke exposure is very dangerous for pets. If you must smoke, do so outside or switch to vaping, but know that you are still likely putting your pets’ health at some degree of risk… to say nothing of what you are doing to yourself.




Environmental tobacco smoke and risk of malignant lymphoma in petcats. Bertone ER, Snyder LA, Moore AS. Am J Epidemiol. 2002 Aug 1;156(3):268-73.


Passive smoking and canine lung cancer risk. Reif JS, Dunn K, Ogilvie GK, Harris CK. Am J Epidemiol. 1992 Feb 1;135(3):234-9.


Cancer of the nasal cavity and paranasal sinuses and exposure to environmental tobacco smoke in pet dogs. Reif JS, Bruns C, Lower KS. Am J Epidemiol. 1998 Mar 1;147(5):488-92.


The dog as a passive smoker: effects of exposure to environmental cigarette smoke on domestic dogs. Roza MR, Viegas CA. Nicotine Tob Res. 2007 Nov;9(11):1171-6.


Demographic and historical findings, including exposure to environmental tobacco smoke, in dogs with chronic cough. Hawkins EC, Clay LD, Bradley JM, Davidian M. J Vet Intern Med. 2010 Jul-Aug;24(4):825-31. 


Methylation of free-floating deoxyribonucleic acid fragments in the bronchoalveolar lavage fluid of dogs with chronic bronchitis exposed to environmental tobacco smoke. Yamaya Y, Sugiya H, Watari T. Ir Vet J. 2015 Apr 29;68(1):7.


Households contaminated by environmental tobacco smoke: sources of infant exposures. Matt GE, Quintana PJ, Hovell MF, Bernert JT, Song S, Novianti N, Juarez T, Floro J, Gehrman C, Garcia M, Larson S. Tob Control. 2004 Mar;13(1):29-37.



Image: MaxPhoto / Shutterstock


Related health content:

Electronic Cigarettes Connected to Canine Fatalities


Finding the Causes of Cancer in Cats and Dogs


Tips for Preventing Cancer in Cats


Comments  1

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  • Lymphoma Causes
    06/25/2016 04:35am

    What do we know about the causes of lymphoma?

    Lymphomas develop because of changes in the genes of a lymphocyte (a type of white blood cell). These changes alter how the cell grows and divides or may prevent it dying when it normally should do. Often more than one change happens in the genes before a lymphoma develops.

    We now know a lot about the gene changes in different types of lymphoma. In most cases, however, no one really knows what makes the changes happen. This is probably because lymphomas are caused by lots of different things that each affect the genes in a small way. Scientists sometimes call this the ‘multi-hit theory’.

    There are some things that are known to increase the risk of developing lymphoma (often called ‘risk factors’). These are things that have been linked with certain types of lymphoma or are seen more often in people with lymphoma. They are not a cause on their own.

    Known risk factors for lymphoma include:

    problems with the immune system
    certain infections
    a close relative having lymphoma
    previous treatment for cancer
    getting older.

    Other things that have been studied but are less clearly linked include:

    chemicals and certain jobs where people use these
    lifestyle, including smoking, diet and obesity.

    Many scientists and doctors studying the causes of lymphoma are now working together through the International Lymphoma Epidemiology Consortium.

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    Immune system problems

    Some people are more at risk of lymphoma because their immune system (a system in the body that protects us from infection and other diseases) does not work normally.

    This may be because their immune system is weakened by another medical condition, such as:

    being on drugs to prevent rejection of an organ or bone marrow transplant (immunosuppressive drugs) – lymphomas that develop in this situation are sometimes called post-transplant lymphoproliferative disorders (PTLDs)
    infection with HIV (human immunodeficiency virus) – many types of lymphoma, particularly Burkitt lymphoma and diffuse large B-cell lymphoma (DLBCL), are more common
    an inherited disorder of the immune system – these are rare and usually show up when people are very young.

    An overactive immune system, which can happen when people have autoimmune disorders, can also lead to an increased risk of certain types of lymphoma. For example:

    having Sjögren’s syndrome increases the risk of developing MALT lymphoma of the salivary gland or lung, or Waldenström’s macroglobulinaemia
    having Hashimoto’s thyroiditis increases the risk of MALT lymphoma of the thyroid, and
    enteropathy-associated T-cell lymphoma (EATL) can occur in people with coeliac disease.

    Back to top

    Certain lymphomas are linked to particular infections. A few viruses cause lymphomas directly – the virus lives in the lymphoma cells and makes them grow and divide. Other viruses and bacteria cause lymphomas indirectly – the infection stimulates the immune system chronically (over a long time), which makes lymphoma more likely to develop.

    Many of these infections are common and most people who have them do not develop lymphoma. This means other things must happen too for a lymphoma to develop.

    The infections linked to lymphoma include:

    Epstein–Barr virus (EBV), the virus that causes glandular fever, is linked with several types of lymphomas. Most people in the world are infected by EBV and the infection does not usually cause any symptoms. EBV is found in the lymphoma cells of:
    the type of Burkitt lymphoma seen in children in Africa and sometimes in the sporadic type of Burkitt lymphoma (the type seen in the UK)
    some Hodgkin lymphomas – in the UK, around a third of Hodgkin lymphomas can be linked to EBV
    HIV-associated lymphoma and post-transplant lymphoproliferative disorder (PTLD)
    nasal-type NK/T-cell lymphoma (a rare type of lymphoma seen mainly in people from Asia and Central America)
    HTLV-1 (human T-lymphotropic virus 1), which is more common in Japan, South-East Asia, the Caribbean, south-eastern USA, South America and parts of Africa, is found in people with ‘adult T-cell leukaemia/lymphoma’ (a lymphoma not often seen in the UK)
    HHV-8 (human herpes virus 8) is linked with primary effusion lymphoma and with an illness called ‘multicentric Castleman’s disease’ – both are uncommon but are sometimes seen in people with a weakened immune system.

    Infections that can indirectly cause lymphoma by over-stimulating the immune system include:

    hepatitis C virus (HCV), which is seen in some people with marginal zone lymphoma and a few with diffuse large B-cell lymphoma
    Helicobacter pylori, bacteria that cause inflammation and ulcers in the stomach, which are often found in people with gastric MALT lymphoma – treatment with antibiotics alone can sometimes cure this lymphoma
    Chlamydia psittaci, which is linked with MALT lymphoma in the tear gland and around the eye
    Campylobacter jejuni, which is linked with MALT lymphoma in the bowel
    Borrelia burgdorferi, which causes Lyme disease, is linked with MALT lymphoma in the skin.

    Note: lymphoma itself is not infectious – you cannot catch it and you cannot pass it on to someone else.

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    Family history

    Lymphoma is not inherited – it is not passed down from generation to generation. Most people with lymphoma have no family history of the disease.

    Having a brother, sister or parent with lymphoma (or another blood cancer) gives people a slightly higher risk of developing lymphoma – approximately doubling the chance for many types.

    Note: the increase in risk is much lower than for some other types of cancer, such as breast cancer. Also lymphomas are not common. Therefore, even if you have lymphoma, it is very unlikely any of your relatives will develop it too.

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    Previous cancer treatments

    Chemotherapy and radiotherapy treatment given for a previous cancer can increase the risk of someone developing lymphoma. This is thought to be due to damage caused by these treatments to genes of the lymphocytes.

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    Older age

    Many lymphomas, like other cancers, are more common in older people. This is because as time goes on more changes happen in the genes and the body is less able to repair these.

    Back to top
    Other possible risk factors

    Many studies have looked for other possible causes of lymphoma. In most cases there has been little to link other possible risk factors with lymphoma. Sometimes one or two studies suggest a possible link, but then other studies find something different. The many different types of lymphoma may explain some of the differences between the results of such studies.

    Industrial chemicals, pesticides and hair dyes have all been looked at as possible risk factors. As these chemicals are more commonly used in certain jobs, studies have also looked at the work that people do. Some studies have suggested links, but possibly only for certain types of lymphoma.

    For instance, people who used hair dyes in the 1970s or earlier may be slightly more likely to develop follicular lymphoma or chronic lymphocytic leukaemia (CLL) – it is likely that hair dyes used more recently are safer. Farmworkers or those who live on farms may be slightly more likely to develop mantle cell lymphoma or CLL, but less likely to develop T-cell lymphomas.

    Scientists are continuing to study the reasons for these differences and exactly which chemicals are important.

    Smoking Many cancers are caused by smoking but there is much less evidence that it leads to lymphoma. Smokers may have a slightly increased risk of follicular lymphoma and of the EBV-linked form of Hodgkin lymphoma.

    Diet There is some evidence that eating plenty of fruit and vegetables, rather than lots of red meat, animal fat and dairy products, makes people less likely to develop lymphoma. Alcohol, coffee and tea have all been looked at but there is no evidence that these increase the risk of lymphoma.

    Exercise Taking more physical exercise has been shown in some studies to lower the chances of developing lymphoma.

    Obesity Some cancers appear to be more common in people who are obese. Evidence of a link with lymphoma has been found in some studies and not in others. This probably means that if it is a risk factor, it is not a strong one. Possibly it is important only if people are very overweight. Or it may be that poor diet and lack of exercise are the real risks for both obesity and lymphoma.

    Back to top

    All these risk factors account for only a few of the lymphomas that develop in people in the UK every year. Most people with one, or even more, of these risk factors do not develop lymphoma.

    In most cases, the cause of lymphoma is not known. There is little or no evidence to suggest that anything you have done – or not done – has caused you to develop lymphoma. Talk to your doctor if you are worried about the possible cause of your lymphoma or about the risk for someone close to you.

    Back to top
    Sources used

    These are a few of the sources we used to prepare this information. The full list of sources is available on request. Please contact us by email ([email protected]) or by ringing 01296 619409 if you would like a copy.

    Roman E, Smith AG. Epidemiology. In: Marcus R, et al. (eds). Lymphoma: Pathology, Diagnosis and Treatment. 2nd edition. 2014. Cambridge University Press, Cambridge UK: 1–10.

    Morton LM, et al. Etiologic heterogeneity among non-Hodgkin lymphoma subtypes: The InterLymph non-Hodgkin lymphoma subtypes project. Journal of the National Cancer Institute Monograph, 2014. 48: 130–144.

    Bassig BA, et al. Current understanding of lifestyle and environmental factors and risk of non-Hodgkin lymphoma: an epidemiological update. Journal of Cancer Epidemiology, 2012. 2012: 978930.

    With thanks to Professor Ruth Jarrett, Professor of Molecular Biology at the University of Glasgow, for her help in reviewing this information.

    We would also like to thank our reader panel who have given their time to review this information.

    Content last reviewed: February 2015

    Next planned review: February 2018
    More information:

    Lymphoplasmacytic lymphoma and Waldenström’s macroglobulinaemia (PDF)
    Gastric MALT lymphoma (PDF)
    Non-gastric MALT lymphoma (PDF)
    T-cell lymphomas (PDF) for information on enteropathy-associated T-cell lymphoma (EATL)

    If you would like a printed copy of any of our lymphoma information, complete our information order form and we will post it to you free of charge (UK, Channel Islands and Republic of Ireland only). If you live outside the UK, we recommend that you contact the lymphoma patient and carer organisation in your country as treatments and healthcare systems vary overseas.
    Relevant printed information:
    Gastric MALT lymphoma
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    Non‑gastric MALT lymphoma
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    T-cell lymphomas
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