Cats whose owners smoke are to three times as likely to develop lymphoma, a form of cancer, as cats living with non-smokers.
The doctor who did the study said cats in many ways were better subjects than people for studying second-hand smoke because cats basically hang around inside the house, so they don't get exposed to as many environmental hazards. And, he said, you can often smell the smoke on their fur, and when you consider that they're grooming all the time with their tongues, they're probably getting a fairly significant dose.
The researchers, headed by Dr. Antony S. Moore of the the Tufts Vet School, found not only that the higher risk of lymphoma is directly related to how much smoke is in the house and how long the cat is exposed. from the NY Times 8/16/02