Second-hand smoke (SHS) has been associated with respiratory cancers in canines, with the predisposed locations determined by the cephalic ratio (head length / head width). Exposure to SHS is frequently measured by analyzing urine or blood samples for the nicotine by-product cotinine. We investigated the suitability of saliva as an alternative source for cotinine analyses in dogs because obtaining saliva is less invasive and cotinine concentrations from SHS exposure are instantaneously measurable in saliva compared to other collection methods. Specifically, we tested for a quantitative relationship between cephalic ratio and the salivary concentration of cotinine. Our null hypothesis was that there is no difference in cotinine concentration in short- and long-nosed dogs that are exposed to SHS. Owners completed a survey about smoking habits, the dog’s exposure to different types of tobacco smoke, dog’s sex, and other variables associated with SHS impacts. Each dog’s body condition and head length and width were recorded. We obtained a saliva sample from the participants’ dogs and analyzed them for cotinine using an ELISA assay. Salivary cotinine concentration was significantly higher in dogs exposed to SHS versus dogs not exposed. There was also a positive linear relationship between cotinine concentration and cephalic ratio. The results did not differ significantly between male and female dogs. Our results supported previous studies reporting that long-nosed dogs accumulate more toxic by-products from SHS compared with short-nosed dogs. Saliva samples may be a useful alternative to more invasive methods when evaluating exposure of some domesticated species to SHS
