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October 19, 2016

Infrequently Asked Questions: Is secondhand smoke bad for my pet?

Little Sneakers may not seem bothered by the stream of smoke flowing from your cigarette, but who can tell? He can't, he's a dog. But science knows the answer, right?

Determined to find an answer on the matter, we reached out to Ericka Krick, assistant professor of oncology at the University of Pennsylvania School of Veterinary Medicine, to drop some knowledge. 

Can secondhand cigarette smoke cause harm to a pet — say, a cat or dog? 

There’s actually not a lot of published data to answer that question. There is, however, one study that shows an increased risk of lymphoma in cats exposed to cigarette smoke. And most of the cats in that report had either intestinal or nasal lymphoma, so the thought is either through breathing, increasing their nasal lymphoma risk, or potentially when cats groom, they’re licking carcinogens off their fur and ingesting them and that’s why it’s intestinal lymphoma.

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There also was a study looking at risk factors for cats with ... a very aggressive cancer of the head and neck in cats. And no significant link was reported there. And there was actually another study that looked at risk factors for nasal tumors in dogs and they looked at exposure to cigarette smoke, but didn’t find any [higher risk] for dogs with nasal tumors. 

And actually, primary lung tumors in cats and dogs is very uncommon. And there hasn’t been a study looking at an increased risk [of] lung cancer in other species because of cigarette smoke. I suspect it's because lung tumors are so uncommon that it would be very difficult to actually recruit enough cases to show a risk or not.

Otherwise, the chemicals in a cigarette would cause the same damaging effects as in a human?

One would think. There have been more studies suggesting that exposure to cigarette smoke can cause changes in the DNA of the cells that line the oral cavity in dogs. That’s the only study asking that question so far. So, potentially. ... We, unfortunately, don't know yet.

And what if I had a lizard or a bird? I imagine there's no info on that either, if the data on cats and dogs is limited.

Unfortunately, that is true. It’s a good question, but you are totally correct that there really isn’t published data about secondhand smoke in those species. But you have to wonder.

It’s interesting that there’s not any data — a testament to how much research there is still to do. In terms of medical studies for animals, is it generally harder to find funding for that sort of thing?

It is. I think that’s probably one of our biggest barriers, is the funding issue. Certainly. It's just difficult to find sources for the type of funding that would be needed for a very large study. We certainly do it, but it is certainly more challenging. Particularly, it’s a little easier for dogs because there has been a lot more evidence to show that a lot of tumors in dogs are really models for people, and cats are a little trickier also because they're a lot smaller. So, it’s difficult to get the same amount of blood and tissue samples from a cat as from a dog, given the smaller body size. It is challenging. But because dogs can be a model for diseases in people, there seems to be more funding available for canine studies as opposed to feline studies.

Anything to add?

The other thing is, that for veterinary studies, it’s one thing to collect data on the veterinary patients and that we can certainly do. But if you’re doing a study where you’re asking owners ‘Do you smoke, and how much do you smoke?’ that’s a whole other set of regulations you have to go through. And that has to go through an institutional review board if you’re collecting data on the humans associated. So I suspect that’s another reason why we don’t have as much data on the exposure of cigarette smoke to patients because that would involve asking clients.

Now, you can potentially check urine of patients for compounds that would indicate cigarette smoke, but that doesn’t necessarily — that’s a snapshot in time, it doesn’t you give you information on how long the pet has been exposed. That you would need a human for. That can be difficult for us veterinarians as well.