The ravages of smoking cigarettes on human health have long been established. Now a new study says that contact with cigarette smoke, even if it's on your clothes after coming from a smoky environment, can damage your dog's health as well.
The study, which was led by Purdue University veterinarian Deborah Knapp, looked at the health and lifestyle factors of 120 Scottish terriers over the course of three years and found that those exposed to cigarette smoke had a six times higher chance of developing bladder cancer than those that weren't. The dogs that developed cancer were exposed to a median level of 10 pack-years of smoke, while the ones who did not get the disease were exposed to a median level of 1.5 pack-years of smoke. A pack year is the equivalent of smoking one pack of cigarettes a day per year.
To determine exposure to smoke, Knapp's research team relied both on questionnaires completed by owners and the analysis of the dogs' urine, in which they looked for traces of a nicotine metabolite known as cotinine. Interestingly, some of the dogs had cotinine in their urine even if their owners didn't smoke, which led the researchers to believe that the dogs picked it up from smelling or licking their clothing.
"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.
The researchers chose to use Scotties for their study because the breed is already known to have a 20% higher risk of developing bladder cancer than other breeds. This gave the team a baseline to work from and a particular area of cancer development to focus on.
"We know that Scotties' genetics play a huge role in making them vulnerable to cancer," Knapp said. "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." The study accounted for the dogs' propensity for developing the condition; the six-fold increase in cancer rates due to smoking exposure was over and above this rate.
The study also confirmed – and made allowances for – previous research showing that being exposed to pesticides, flea treatments and shampoos; having repeated urinary tract infections; and living within one mile of a marsh all raised bladder cancer risks in Scotties. The marsh link is likely due to increased insecticide spraying in such areas.
The researchers say that the findings could help shed light on links between carcinogens and cancers that could also be applicable to humans, making dogs what they call "sentinels for environmental risks to humans." That's because, due to their shorter lifespans, dogs develop conditions in relation to stimuli at a quicker rate than humans. For example, carcinogen exposure in humans might take decades to appear as cancer, while in dogs, the effect can manifest in as short a period of time as one year. Of course, they also point out the study's potential to safeguard our furry friends from mitigatable risks.
"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," Knapp said. "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 has been published in The Veterinary Journal.
Source: Purdue University
