You may not feel ready to kick the habit just yet. But health officials are urging smokers to quit - if only to save their pets.

Chemicals in tobacco smoke wreak havoc on the blood and organs of cats, dogs, guinea pigs, hamsters and even fish - driving up their risk of developing cancer, heart disease or lung disease.

Compared to human studies, research on smoking-related illnesses in animals remains relatively scarce. However, the Food and Drug Administration has released an advisory urging smokers that the studies we do have show even third-hand smoke can kill animals. 'Smoking's not only harmful to people; it's harmful to pets, too,' said FDA veterinarian Carmela Stamper. Chemicals in tobacco smoke wreak havoc on the blood and organs of cats, dogs, guinea pigs, hamsters and even fish - driving up their risk of developing cancer or lung disease.

'If 58 million non-smoking adults and children are exposed to tobacco smoke, imagine how many pets are exposed at the same time. 'Like children, dogs and cats spend a lot of time on or near the floor, where tobacco smoke residue concentrates in house dust, carpets and rugs. 'Then, it gets on their fur. 'Dogs, cats and children not only breathe these harmful substances in, but pets can also ingest them by licking their owner's hair, skin, and clothes.'

Secondhand smoke can cause lung and nasal cancer in dogs, malignant lymphoma in cats and allergy and respiratory problems in both animals, according to studies done at Tufts University's School of Veterinary Medicine in Massachusetts, Colorado State University and other schools.

The number of pets that die each year from tobacco exposure isn't available, but vets know from lab tests and office visits that inhaling smoke causes allergic reactions, inflammation and nasal and pulmonary cancers in pets. Lymphoma is one of the leading causes of feline death. The Tufts research showed that repeated exposure to smoke doubled a cat's chances of getting the cancer and living with a smoker for more than five years increased the risk fourfold. It can also cause a fatal mouth cancer.

Tobacco companies acknowledge the risks of smoking in people but haven't taken the same stance with dogs and cats.

Philip Morris USA says on its website that it believes cigarettes cause diseases and aggravates others in non-smokers and that the problems warrant warnings. Cancer kills more dogs and cats than any other disease, according to Denver-based Morris Animal Foundation, which has been funding pet cancer research since 1962.

In addition, the recent surge in the use of electronic cigarettes has raised questions about their impact on pets. The greatest danger is the trash, where dogs can find nicotine cartridges from e-cigarettes, said Rozanski, the Tufts veterinarian. 'You wouldn't think dogs would eat such things, but they do,' she said.

Dogs with big noses have a higher risk of developing nose cancer. The hair and mucus in one's nose - either human or animal - traps tobacco smoke, dust and other particles, stopping them from reaching the lungs. Therefore dogs with bigger noses - Greyhounds, Borzois, and Doberman Pinschers, for example - trap more particles. While this protects them from lung cancer, the toxins are then stuck in their noses, where they fester. Over time, these carcinogenic toxins could cause nose cancer.

Smaller-nosed dogs have a higher risk of lung cancer. These pups - including Pugs, Bulldogs and Beagles - do not have the same filter as their bigger-nosed cousins. Fewer tobacco smoke particles get trapped, and therefore more carcinogens travel directly into the lungs, increasing the risk of lung cancer.

Cats tend to have a much higher risk of developing cancer than dogs. Most common among cats are mouth cancer and cancer of the immune system (lymphoma). That is because they groom themselves, licking their fur - and the invisible carcinogenic toxins that have become stuck to their fur. By licking these toxins, cats in smoking households have a four-times higher risk of developing oral squamous cell carcinoma - an aggressive form of mouth cancer. Even with chemotherapy, rarely more than 10 percent of cats live for more than a year after being diagnosed with this type of cancer.

Cats whose owners smoke one pack a day have a three-times higher risk of developing lymphoma than those that don't. Even with treatment, they have a life expectancy of six months.

A study by the Veterinary Clinics of North America Exotic Animal Practice found fish exposed to toxic levels of nicotine will start to spasm, lose colour, get rigid fins, then ultimately die. Another study published by Tobacco Control placed a school of minnows in nicotine-infected water. Half of them died within 96 hours.