Professor Clare Knottenbelt at the University of Glasgow would like to change that by creating more awareness and understanding through her research. So far her team has shown a direct link between pets living in a smoking environment and a higher risk of health problems. Previous studies have shown a link to cancer risk, but the new research also uncovered a connection to weight gain in castrated dogs.
When the scientists examined the testicles of male dogs post-neutering, they found a gene that they believe acts as a marker of cell damage since it appears more often in dogs living in smoking homes versus non-smoking homes. In other studies, this gene has been shown to be altered in dogs with certain canine cancers. However, the effect on this gene was reduced when owners chose to smoke outside to reduce their pets' exposure. So this is a way for people to limit their pets' risk if they can't outright quit.
Interestingly, the researchers found that cats are even more affected by smoke than dogs. The hypothesis is that self-grooming may increase the amount of smoke ingested. Free access to the outdoors didn't significantly help reduce risk.
Clare's research is ongoing and is expected to be published later this year. However, I think the early findings, combined with what we already know about the effects of smoking, makes a compelling reason to quit smoking, or at least limit it as much as you can.