'Stop Smoking Altogether,' Dog Owners Warned

Smoking cigarettes near your dog can increase their risk of cancer, according to a new study.

Exposure to cigarette smoke can increase the risk of bladder cancer in Scottish terriers by up to six times, new research in The Veterinary Journal revealed.

Scottish terriers are already known to develop bladder cancer at a twentyfold greater rate than other dog breeds, with cigarette smoke only further exacerbating this breed's vulnerability to the disease.

"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," Deborah Knapp, a veterinarian at Purdue University and co-author of the paper, said in a statement. "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."

Researchers studied a group of 120 Scottish terriers, also known as Scotties, over a three-year period, tracking the dogs' health, environment, food intake and physical activity. They hoped to pin down exactly what may drive the high cancer rates in the breed and what can be done to minimize the risks to Scotties, other dogs, and even humans.

"Cancer is a combination of what you are born with — your genetics — and what you are exposed to — your environment," Knapp said. "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?'"

Scotties are especially prone to cancer due to their genetics, meaning that environmental factors that may trigger cancer are particularly important to be aware of as an owner.

"Scotties inherit some genetic variants, i.e. differences in their genome, that puts them at higher risk of cancer. The exact causative variant(s) in their genome has/have not yet been defined, but that is an active area of investigation. The cancer studied the most in Scotties is bladder cancer, although they do develop other forms of cancer too," Knapp told Newsweek.

The chemicals in cigarette smoke can be taken up into the body by breathing or by licking clothes that have absorbed the fumes and eventually end up being excreted in the urine.

"The carcinogens in cigarette smoke are taken into the body and eliminated from the body through the kidneys, i.e. in the urine. The urine containing the carcinogens bathes the lining of the urinary tract, leading to DNA damage and cancer development," Knapp said.

This urine content of smoke particulates is why smoke can cause bladder and urinary tract cancers and can also allow for the measuring of how much a person or animal has been exposed to smoke.

The researchers found that cigarette smoke is one of the main drivers for the development of bladder cancer in Scotties and that dogs may even be exposed to cigarette smoke when their owner does not smoke.

"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," Knapp said.

However, not all dogs—or humans—exposed to cigarette smoke get cancer, and some may develop cancer after minimal exposure to smoke.

The authors hope that this research can be used to figure out exactly which genes predispose dogs and humans to certain types of cancer and how the environment can influence them.

"The findings support the use of dogs in high-risk breeds to help elucidate gene-carcinogen interactions which could be involved in canine and human [urothelial carcinoma], and to develop cancer prevention strategies around these interactions," they wrote in the paper.

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Update 01/05/24, 10:41 a.m. ET: This article was updated with comment from Deborah Knapp.