Second-hand smoke, also called environmental tobacco smoke (ETS), is known ­to play a role in the development of cancer, lung disease and heart disease in people. Now evidence shows it is a health hazard to dogs as well.

ETS is linked to canine nasal sinus (nose) cancer. Dogs in ETS households have a greater chance of developing this cancer than dogs that are not exposed to second-hand smoke.

Long-nosed dogs such as Collies are at the highest risk for nasal cancer. Two hy­po­theses have been proposed for this. One is that their longer nasal passages con­tain more cells than those of short-nosed dogs, so have a greater opportunity to de­velop tumours.

The other hypothesis is based on how smoke is inhaled. Cigarette smokers in­hale through their mouths and the carcinogens in the smoke are deposited di­rectly in the lungs, triggering lung cancer. On the other hand, bystanders inhale ETS through the nose, which filters cancer-causing chemicals.

You can imagine that these nasal filters are effective in long-nosed dogs so the carcinogens become concentrated. In contrast, squat-nosed dogs have shorter nasal passages that are less efficient at removing carcinogens from the air. The result – short-nosed dogs have fewer nasal tumours but more lung tumours than their long-nosed counterparts.

Researchers at the Western College of Veterinary Medicine in Saskatoon also delved into the question of whether cigarette smoke affects overall hea­lth. They performed physical exams, had owners fill out questionnaires, and performed a myriad of tests.

What they found was that dogs from smoking households had more muscle on the left side of the heart, supposedly reflecting a heart that is working harder to pump blood. This, along with poor relaxation of the arteries, indicated the dogs had high blood pressure.

Although the changes in the dogs’ hearts did not seem to create signs of illness, the same heart changes in people often lead to significant cardiac disease. We don’t know what the heart changes mean for the dogs’ long-term health, so studies are ongoing.

As we share more of our lives with our dogs, they are exposed to the same en­vi­ronmental hazards that we are. We know that second-hand smoke is bad for peop­le. Now we know it’s bad for our dogs.

By Jeff Grognet, D.V.M.
A multi-published writer, Jeff Grognet, D.V.M., B.S.c.(Agr.), runs a veterinary practice in Qualicum Beach, B.C., along with his wife, Louise Janes, D.V.M.
(Appeared in May, 2008 issue)