By Guest Author Chloe Bloom and Jean Hofve, DVM (Revised 6/3/20)smoke-1001667_1280

For many years now, we have known how dangerous tobacco smoking is to health. The list of ways it can harm smokers seems to grow longer every year, as more and more research is conducted. Children, as well as pets, are at risk from smoke in their environment.

Second-Hand Smoke

It’s fairly well known that smoke from cigarettes (and all other tobacco smoke sources such as pipes and cigars) can harm non-smokers via passive intake, or “second-hand” smoke. Children as well as pets are at high risk from smoke in their environment, due to their size and sensitivity.

Since the discovery of this added risk, steps have been taken to reduce the exposure non-smokers receive. So far, 30 U.S. states and 20 foreign countries have enacted laws restricting or prohibiting smoking in public areas, as well as businesses.

The biggest reason pets all over the country are being exposed to second-hand smoke is that people are simply unaware of how serious the danger is. Smoking awareness campaigns are trying to change this, but it is a slow process.

These dangers are not a new discovery. Studies have been conducted since the 1990s on this issue. For example researchers at Tufts University studied two groups of cats. One group came from homes where they cats were exposed to second-hand smoke; the other group came from homes that were smoke-free.

The study found that cats that lived with indoor smokers for just one year were 100% more likely to contract lymphoma, a malignant blood cancer. The more time the cat spent in the home, the higher the risk became. After 5 years of exposure, the cats’ risk of developing lymphoma increased by 300%. [Bertone et al. 2002]

Other research has found that, even when no one in a home smokes, if they live in an apartment next to a smoker, that smoke can still get into your space and cause the same issues.

As if all that is not shocking enough—it is not just second-hand smoke that causes problems. Recent research has found that “third-hand smoke” is also a problem; and it may affect pets even more than people.

Third-Hand Smoke

Third-hand smoke is the sticky residue that remains when the cigarette smoke itself has dissipated. It clings to everything it touches: clothing, furniture, rugs, floors, and walls. This residue contains more than a dozen highly dangerous and carcinogenic chemicals, including tar, nicotine, arsenic, lead, cyanide, and benzene. Cotton in particular absorbs a great deal of nicotine, which is still present a week after exposure. Just think about the things your pet licks throughout the day. Every time the pet eats, drinks water, or grooms herself, she is ingesting toxic third-hand smoke. This is a serious problem for cats, because they spend more time and are more thorough in grooming than other pets.

Third-hand smoke residue is very persistent. It can also off-gas multiple toxins and carcinogens (cancer-causing compounds). [Sleiman 2010]

Marijuana Smoke

Second-hand marijuana smoke also has harmful effects. This is a growing problem, as more states are legalizing medical and/or recreational marijuana. Currently, Alaska, Colorado, Oregon, and Washington have legalized it, and more are likely to join the list after the November 8 election, including Arizona, California, Maine, Massachusetts, and Nevada. Pot smoke is set to create a widespread hazard for our pets.

The “high” experience appears to be unpleasant for animals. Unlike the enjoyable sensations people usually get with marijuana, pets become depressed, disoriented, wobbly, and often incontinent (involuntary urination). Their heart rate and body temperature drops. Effects can last up to 72 hours. With the new, stronger pot strains, there’s a risk of increased excitability, high fever, tremors, seizures, and possibly coma or death. Deliberately exposing pets to pot smoke may also be considered abuse under most state laws.

Tests have shown that just one minute of exposure to marijuana smoke alters the function of blood vessel lining cells (endothelial cells) for 90 minutes—even longer than tobacco smoke! While it’s too soon to tell, long-term cardiovascular health is likely to be compromised in pets exposed to marijuana smoke.

Veterinarians are reporting a sharp increase in the number of pets needing emergency treatment for marijuana toxicity in states where its use is legal; particularly for dogs who have eaten a large amount of buds or edibles.

To reduce the potential harm of marijuana smoke, consider using edibles instead. Just be sure to keep pot and pot-containing edibles securely out of reach of pets—and kids!


E-cigarettes were originally intended as a bridge to quit smoking, but more and more they are being used as a standalone pleasure, especially for young adults. The cartridges are a special danger to pets, especially those that contain nicotene; if an exploring tooth punctures one, it can be fatal. New research is finding some serious dangers to smokers themselves; the second- and third-hand smoke risks are reduced, but not eliminated. Nicotine is still present, albeit at lower levels. But vape smoke alone causes oxidative stress and increased free radical generation in animals exposed to it. This has been shown to disrupt the immune system and makes the animal more susceptible to viral and bacterial infections.

One chemical found in many vaping products, propylene glycol, causes anemia in cats; it is banned in cat foods even at low concentrations. A similar compound, diethylene glycol, can damage your cat’s kidneys.

Third-hand smoke is also an issue with vaping.


Just like children, our pets do not deserve the additional risk they are exposed to by living with a smoker. So what can be done to minimize the harm that comes to them?

Quitting smoking is clearly the best choice. It is the only realistic way to reduce or eliminate the risk. Of course, while it is highly recommended, not everyone reading this can or will quit smoking immediately. But there is one very effective and simple thing that can be done, while remaining a smoker, to reduce your animals exposure to the dangers of tobacco smoke:

Smoke outside.

Unfortunately, no other solution is adequate. Studies that have been conducted on the spread of second- and third-hand smoke have shown that tactics like opening a window while smoking, or smoking in another room, simply do not work.

Even these measures will not totally eliminate your pet’s exposure. Third-hand smoke will still cling to your skin and clothes. But it is a significant improvement on smoking anywhere indoors.

With winter coming, the need to smoke outside could be disconcerting news. But if you do not go outside to smoke, you will be harming your pet. Perhaps this is a good time to consider quitting!

Whatever decisions you make for yourself, please help spread the word about the dangers of second- and third-hand smoke for animals. We need to ensure that our pets are protected from this insidious danger!

If you do decide to quit, then stop smoking socially with the co-author of this article, Chloe Bloom, at


  • Bertone ER, Snyder LA, Moore AS. Environmental Tobacco Smoke and Risk of Malignant Lymphoma in Pets. American Journal of Epidemiology. 2002; 156(3):269-273.
  • Singer BC, Hodgson AT, Nazarof WW. Effect of sorption on exposures to organic gases from environmental tobacco smoke (ETS). Proceedings: Indoor Air 2002, 2002.
  • Sleiman M, Gundel L, Pankow J, et al. Formation of carcinogens indoors by surface-mediated reactions of nicotine with nitrous acid, leading to potential thirdhand smoke hazards. Proceedings of the National Academy of Sciences, February 8, 2010.
  • Sussan TE, Gajghate S, Thimmulappa RK, Ma J, Kim J-H, Sudini K, et al. (2015) Exposure to Electronic Cigarettes Impairs Pulmonary Anti-Bacterial and Anti-Viral Defenses in a Mouse Model. PLoS ONE. 10(2): e0116861.
  • Wang X, Derakhshandeh R, Liu J, et al. One Minute of Marijuana Secondhand Smoke Exposure Substantially Impairs Vascular Endothelial Function. Journal of the American Heart Association. 2016 Aug; 5(8): e003858.

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