RESUMEN
More than 40 mutagenic and carcinogenic agents present in cigarette smoke have been identified as causative factors of human cancer, but no relation has been clearly documented in companion animals. In dogs, in addition to smoke inhalation and transdermic absorption, exposure to smoke includes oral ingestion of particles adhered to the animal's fur. This study evaluates the presence and type of histological alterations and DNA integrity in oropharyngeal tissue in dogs exposed and non-exposed to household cigarette smoke by means of histopathology and comet assay studies on biopsy and swab samples. A non-probabilistic convenience sample of 12 dogs were selected and classified in two groups: exposed and non-exposed to cigarette smoke. Non-parametric Kruskal-Wallis test was carried out on biopsy and swab data and a Chi(2) test was performed on the information obtained by histopathology. A significance level was set at P<0.05. Statistically significant differences were found between groups in comet assays carried out on biopsy samples. No differences (P>0.05) were found between groups based on comet assays swab samples and histopathology assessment. In conclusion, exposure to cigarette smoke causes DNA damage in dog oropharyngeal tissue. The use of dogs as sentinels for early DNA damage caused by exposure to environmental genotoxic agents like cigarette smoke is reported for the first time.