Hair nicotine concentration measurement in cats: its relationship to owner-reported environmental tobacco smoke exposure; and its measurement in cats with gastrointestinal lymphoma and unaffected control cases

The negative health effects of smoking and exposure to second-hand smoke are well documented in people. Several biomarkers of environmental tobacco smoke (ETS) exposure have been identified in human medical research. Relatively little research has been performed in cats to investigate possible biomarkers of ETS and disease associations, however an association between ETS and the development of several anatomical variants of lymphoma has been suggested. The objectives of this thesis were to: (1) investigate the utility of hair nicotine concentration (HNC) in cats as a biomarker of ETS; (2) investigate the association between HNC in cats and owner reported exposure; (3) identify a cut-off HNC to differentiate between exposed and unexposed cats; and (4) further investigate the association between exposure to ETS and gastrointestinal lymphoma, using HNC as a biomarker. Nicotine was extracted from cat hair by sonification in methanol, followed by hydrophilic interaction chromatography with mass spectrometry. Owner questionnaires were used to quantify ETS exposure. The HNC of reportedly exposed and unexposed groups were compared and a cut-off value to differentiate these groups was created. To investigate associations between ETS and gastrointestinal lymphoma, the HNC of cats affected by this condition was compared to the HNC of control cases. The HNC of reportedly exposed cats was significantly higher than that of unexposed cats. When the cats were grouped according to the intensity of exposure and the number of products smoked each day at home, the median HNCs were significantly different. A hair nicotine concentration of 0.1ng/mg had a specificity of 98% for detecting exposure to ETS. Using HNC as a biomarker of exposure to ETS, there was no significant difference in HNC between cats with gastrointestinal lymphoma and control cases, although the group of cats with the highest HNC was composed of nearly two-thirds lymphoma cases. A further study with larger case numbers would help confirm whether cats with exposure to ETS do or do not have an increased risk of gastrointestinal lymphoma