Cancer risk in dogs is greatly elevated by exposure to cigarette smoke

In a study led by Purdue veterinarian Deborah Knapp, experts have found that exposure to cigarette smoke significantly elevates the risk of bladder cancer in dogs. 

The researchers tracked 120 Scottish terriers over three years, revealing that those exposed to cigarette smoke were six times more likely to develop bladder cancer compared to unexposed dogs.

Risk factors of dogs and smoke

Knapp, a renowned expert in veterinary medicine and a leader in comparative oncology research, emphasized the interplay of genetics and environmental factors in cancer development. 

“Cancer is a combination of what you are born with – your genetics – and what you are exposed to – your environment,” Knapp explained.

“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 are particularly prone to bladder cancer, with a rate 20 times higher than other dog breeds.

Bladder cancer is often very aggressive in these dogs, similar to muscle invasive bladder cancer in humans, noted the researchers.

“We know that Scotties’ genetics play a huge role in making them vulnerable to cancer,” said Knapp. This strong genetic signal helps researchers isolate other factors that affect the likelihood of any dog, or human, getting cancer.  

“If we were to do this study with mixed breeds of dogs, it would take hundreds and hundreds of dogs to uncover this same risk, which is probably there, just more difficult to discern because those dogs are not already inclined genetically to get bladder cancer.”

How to study dogs and cigarette smoke

The research team, including Scottish terrier expert Marcia Dawson, delved into the impact of tobacco smoke exposure on dogs.

The experts studied 120 Scottish terriers, analyzing their health, environment, food, activity, and any other factors that may affect their cancer risk.

Dogs can inhale secondhand smoke or ingest chemicals through licking smoke-infused clothing, leading to the absorption and urinary elimination of harmful compounds like nicotine metabolites. 

“If someone goes out to a smoky concert or party, then comes home and their dog hops up on their lap to snuggle with them, the dog can be exposed to the particulate material in smoke through the person’s clothing,” explained Knapp.

Key research findings

Some dogs showed exposure to smoke even in non-smoking households, suggesting indirect exposure through environments visited by their owners.

The study also revealed a complex relationship between smoke exposure and cancer development. Not all dogs exposed to smoke developed cancer, mirroring the variability seen in human smokers.

This complexity provides the Purdue team with an opportunity to further investigate the interplay of genetics and environmental factors in cancer development.

Knapp emphasized that this discovery is a new one. Dog owners, who almost universally want the best for their dog, did not knowingly put their dogs at risk of cancer by smoking around them. However, with this new information, individuals may be able to better protect their pets going forward.

Results and future implications

Contrary to previous research, the experts did not find a connection between lawn chemicals and bladder cancer. 

“That’s likely because we are working with pet owners who are aware of the risk of lawn chemicals, so they took precautions to keep the dogs safe, like not treating parts of the lawn where the dog tends to be or keeping the dogs off the lawn for longer,” said Knapp.

“That is encouraging! People love their pets. There are people taking steps to keep their dogs healthier.”

Ultimately, understanding the link between cigarette smoke and cancer can lead to more informed decisions to protect pets’ health. 

“What we hope pet owners will take from this is that if they can reduce the exposure of their dogs to smoke, that can help the dogs’ health,” said Knapp.

“We hope they stop smoking altogether, both for their health and so they will continue to be around for their dogs, but any steps to keep smoke from the dogs will help.”

The study was funded by the National Institutes of Health’s National Cancer Institute, the Scottish Terrier Club of America and gifts made to Purdue University for canine bladder cancer research.

More about dogs and cancer

As discussed above, dogs, much like humans, are susceptible to a variety of cancers, which have become a significant health issue in the canine world.

Cancer, an uncontrolled growth of cells, can affect dogs of all breeds and ages. The most common types include lymphoma, affecting the lymph nodes; mast cell tumors, usually found on the skin; and osteosarcoma, a bone cancer.

Symptoms vary based on the cancer type but often include lumps or bumps, sudden weight loss, lethargy, and changes in appetite or behavior.

Diagnosis and treatment

Early detection plays a crucial role in successful treatment. Regular veterinary check-ups and paying attention to any unusual changes in your dog’s health are vital.

Modern veterinary medicine offers a range of treatments, including surgery, chemotherapy, and radiation, often used in combination for the best outcome. The choice of treatment depends on the cancer type, stage, and the overall health of the dog.

While the diagnosis of cancer in a dog can be devastating, advancements in veterinary oncology have significantly improved the prognosis for many dogs.

Owners play a critical role in the care of a dog with cancer, providing emotional support and working closely with veterinarians to ensure the best possible quality of life.

In summary, cancer in dogs is a complex health issue that requires awareness and proactive care. With advances in veterinary medicine and the commitment of dog owners, many dogs with cancer can lead fulfilling lives.

Early detection, appropriate treatment, and loving care are the keys to managing this challenging condition.

The research is published in The Veterinary Journal.

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