Plasma, salivary and urinary cotinine in non-smoker Italian women exposed and unexposed to environmental tobacco smoking (SEASD study)

Background: The aim of this study was to compare cotinine determinations in three biological fluids for assessing environmental tobacco smoke (ETS) exposure in female non-smokers (n=1605) in Italy. Methods: Information about ETS exposure at home, in the workplace, and in other places within the previous week was collected via questionnaire. Plasma, salivary and urinary cotinine levels were measured. Cotinine levels of >=0.1 ng/mL for plasma, >=0.2 ng/mL for saliva, and >=0.5 ng/mL for urine were used to determine biochemical exposure. Results: Median cotinine levels were significantly higher in exposed than in unexposed women (0.21 vs. 0.05 ng/mL in plasma, 0.80 vs. 0.41 ng/mL in saliva, and 9.74 vs. 5.30 ng/mL in urine). Self-reported ETS exposure was significantly related to biochemical exposure [odds ratio 2.99, (95% CI 2.40-3.72) for plasma; 1.90 (1.51-2.39) for saliva; and 2.67 (2.14-3.34) for urine]. Cotinine significantly increased with increasing exposure level, regardless of the exposure source. Among self-reported exposed subjects, higher percentages of cotinine level above the cut-off, i.e., indicating exposure, were found in saliva (76%) and urine (75%) than in plasma (52%). Conclusions: In general, women correctly reported their ETS exposure status. Both non-invasive salivary and urinary cotinine determinations seem preferable in epidemiological studies, in view of their higher sensitivity, when compared to plasma cotinine.