The harm of smoking to human health has long been proven. Now, a new study suggests that exposure to cigarette smoke, even on clothing in a smoky environment, can harm your dog's health. The study, led by Purdue University veterinarian Deborah Knapp, examined the health and lifestyle factors of 120 Scottish terriers over three years and found that those dogs exposed to cigarette smoke were six times more likely to develop bladder cancer than those not exposed to cigarette smoke.
Dogs with cancer were exposed to smoke for a median of 10 pack-years, while dogs without the disease were exposed to smoke for a median of 1.5 pack-years. A pack-year is equivalent to smoking a pack of cigarettes every day for every year.
To determine whether dogs had been exposed to smoke, Knapp's team relied on questionnaires filled out by dog owners and analysis of the dogs' urine, which looked for traces of a nicotine metabolite called cotinine. Interestingly, some dogs have cotinine in their urine, even if their owners don't smoke, leading researchers to believe the dogs are ingesting cotinine by sniffing or licking their clothing.
"If someone goes to a smoky concert or party and then comes home and their dog jumps on their lap and snuggles with them, the dog is exposed to particulate matter in the smoke through the person's clothing," Knapp said.
The researchers chose Scotch dogs for their study because the breed has a 20 percent higher risk of developing bladder cancer than other dog breeds. This gives the research team a baseline to work from, and a specific area of focus for cancer development.
"We know that Scotch dogs' genes play a huge role in predisposing them to cancer," Knapp said. "If we did this study with mixed-breed dogs, it would take hundreds or thousands of dogs to detect this same risk, and the risk is probably there, it's just harder to detect because these dogs are not genetically predisposed to developing bladder cancer. This study takes into account the dogs' predisposition to the disease; a six-fold increase in cancer rates from smoking goes beyond that.""
The study also confirmed and took into account previous research inaccuracies that exposure to pesticides, flea treatments and shampoos; repeated urinary tract infections; and living within one mile of a bog all increase the risk of bladder cancer in Scotch dogs. The cause associated with the swamps may be an increase in the spraying of pesticides in these areas.
The researchers say the findings help reveal a link between carcinogens and cancer that may apply to humans as well, leading them to call dogs "sentinels of human environmental risks." This is because, due to dogs' shorter lifespans, they can become irritated and develop the disease more quickly than humans. For example, it can take decades for humans to develop cancer after exposure to carcinogens, whereas in dogs, the effects can become apparent in as little as a year. Of course, they also point out that this research has the potential to protect our furry friends from mitigable risks.
"What we hope pet owners take away from this is that if they can reduce their dog's exposure to smoke, it will help their dog's health," Knapp said. "We hope they quit smoking altogether, both for their health and so they can continue to be around their dogs, but anything that keeps the smoke away from their dogs will help."
The study was published in the Veterinary Journal.