In other animals

Multiple studies have been conducted to determine the carcinogenicity of environmental tobacco smoke to animals. These studies typically fall under the categories of simulated environmental tobacco smoke, administering condensates of sidestream smoke, or observational studies of cancer among pets. To simulate environmental tobacco smoke, scientists expose animals to sidestream smoke, that which emanates from the cigarette's burning cone and through its paper, or a combination of mainstream and sidestream smoke. The IARC monographs conclude that mice with prolonged exposure to simulated environmental tobacco smoke, that is 6hrs a day, 5 days a week, for five months with a subsequent 4 month interval before dissection, will have significantly higher incidence and multiplicity of lung tumors than with control groups. The IARC monographs concluded that sidestream smoke condensates had a significantly higher carcinogenic effect on mice than did mainstream smoke condensates. Observational studies Second-hand smoke is popularly recognised as a risk factor for cancer in pets.[175] A study conducted by the Tufts University School of Veterinary Medicine and the University of Massachusetts Amherst linked the occurrence of feline oral cancer to exposure to environmental tobacco smoke through an overexpression of the p53 gene.[176] Another study conducted at the same universities concluded that cats living with a smoker were more likely to get feline lymphoma; the risk increased with the duration of exposure to secondhand smoke and the number of smokers in the household.[177] A study by Colorado State University researchers, looking at cases of canine lung cancer, was generally inconclusive, though the authors reported a weak relation for lung cancer in dogs exposed to environmental tobacco smoke. The number of smokers within the home, the number of packs smoked in the home per day, and the amount of time that the dog spent within the home had no effect on the dog's risk for lung cancer.[178] Animal nicotine poisoning Animals like dogs, cats, squirrels, and other small animals are affected by not only second-hand smoke inhalation, but also nicotine poisoning.[citation needed] Domestic pets, especially dogs, usually fall ill when owners leave nicotine products like cigarette butts, chewing tobacco, or nicotine gum within reach of the animal.[citation needed] Littered cigarette butts from smokers are a problem for small animals that mistake them for food if they find them on sidewalks or trashcans.[179] Cigarette butts are the remains of a cigarette after smokin which contain the filter which is meant to contain tar, particles, and toxins from the cigarette such as ammonia, arsenic, benzene, turpentine and other toxins. As set out in the IARC monographs, the carcinogenicity of cigarette smoke is determined in two ways. The first is through the application of cigarette-smoke condensates to skin. Cigarette-smoke condensates are collected by passing smoke through cold traps and recovering the retained material. The cigarettes are usually machine-smoked and the material is washed from the traps using a volatile substance such as acetone, which is then removed. Many of the procedures for collecting this cigarette-smoke-condensate have not yet been standardized across laboratories, including how the condensate is stored, in what numbers and fashion the cigarettes are smoked, and the type of solvent used. Once the condensate is collected, it is painted onto the skin of the animal test subjects, which are then examined at set intervals to assess the growth of tumors. The second method, as described by the IARC monographs, used to measure the carcinogenicity of cigarette smoke to animals is by exposing them to mainstream cigarette smoke. The IARC monographs define mainstream cigarette smoke as that which is emitted by the mouth end of the cigarette and therefore the smoke that human smokers would be exposed to most. The IARC monographs describe the methods and equipment that scientists have developed to make more effective and standardize the deliverance of mainstream cigarette smoke. These devices vary between whole-body and nose-only exposure, but typically involve machine smoked cigarette smoke being pumped into a small chamber that contains the animal test subjects. A variety of factors differentiate the experience of a human smoker from these animal test subjects'. Human smokers inhale smoke voluntarily and therefore do so more deeply than do animal test subjects which typically adopt short, shallow breaths when exposed to smoke. The animal test subjects, primarily rodents and dogs, also have significantly morphologically different upper respiratory system from humans. Despite these variables, the doses of smoke administered to these animals can be determined by examining tissue and blood samples. Dogs, which cannot be exposed to cigarette smoke via inhalation chambers as easily as can small rodents, require different methods of cigarette smoke exposure. These methods include thracheostomy, in which smoke is pumped through a tube directly into a hole cut in the dog's throat, or through a mask fitted to the dog's face.