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Cigarette Smoke and Bladder Cancer In Dogs

It has long been known that dogs get cancers, from similar chemical exposures as humans (e.g., lymphoma from exposure to weed-killer 2,4-D on lawns). A recent study found that Scottish terriers exposed to cigarette smoke develop bladder cancer about 6 times more than terriers not exposed to cigarette smoke.

Dogs can be viewed as "sentinel species" or early warning systems for harmful chemical exposures. This is because they show risks or dangers due to chemical exposures in the environment earlier than humans. They live alongside humans and so are exposed to the same things as humans.

By the way, smoking is also considered a major risk factor in human urinary bladder cancers.

From Futurity (site that publishes research news from universities): CIGARETTE SMOKE MAY SPIKE DOGS’ BLADDER CANCER RISK

By assessing individual dogs and studying their medical history, scientists are beginning to untangle the question of who gets cancer and why, and how best to detect, treat, and prevent it.

For the study, published in the Veterinary Journal, researchers tracked a cohort of 120 Scottish terriers over a three-year period. They found that dogs exposed to cigarette smoke were six times more likely to develop bladder cancer than those that were not.

“Cancer is a combination of what you are born with—your genetics—and what you are exposed to—your environment,” says Deborah Knapp, a professor of comparative oncology and professor of veterinary medicine at Purdue University. “In this case, we studied these dogs for years at a time, and then we went back and asked, ‘What was different between those that developed cancer and those that did not develop cancer? What were the risk factors?'”

Scottish terriers develop bladder cancer at a rate 20 times higher than that of other dog breeds. And when Scotties and other dogs develop bladder cancer, it is often an aggressive form similar to muscle invasive bladder cancer in humans.

Knapp’s team studied 120 Scotties, assessing their health, environment, food, activity, locations, and anything they could think of that might affect their cancer risk. The goal was both to figure out what could prevent a heartbreaking and often fatal cancer in this breed, but also to use that information to see what might affect cancer in other dogs and even humans.

Dogs make an excellent study species because they live alongside humans, sharing food, bedding, housing, atmosphere, and almost everything else.

When a dog (or human) is exposed to tobacco smoke, either by breathing it or by licking clothes saturated with the scent, their body takes up the chemicals in the smoke and eliminates them through the urine.

This leads to cancer in the urinary tract, but also offers a way to assess smoke exposure. The researchers analyzed the dogs’ urine for a nicotine metabolite, cotinine, and its presence indicated the dog had been exposed to significant amounts of tobacco smoke.

Any time tobacco smoke is present in the same room as a dog, the dog breathes in the smoke. However, some dogs also had cotinine in their urine when their owners did not smoke. In that case, the dog could have been exposed away from the home. Or it may be that their owners visited places where others were smoking and returned home with smoke on their clothes.

The results are not all black and white. Not all the dogs who were around smokers got cancer, and some dogs who were not around the smoke still got cancer. This is also true in humans. Half of human bladder cancer is due to smoking, but not all smokers develop bladder cancer. This discovery gives the researchers the opportunity to study how the combined effects of the genetics inherited from the parents plus environmental exposures lead to cancer.

That new and encouraging result means there are further things humans can do to protect dogs. They can reduce the amount of smoke around the dog by quitting smoking or by smoking outside away from the dog and changing clothes before they come back inside from a smoky environment and snuggling their dog.

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