Kehl et al. BMC Public Health 2010, 10:424 http://www.biomedcentral.com/1471-2458/10/424 R E S E A R C H A R T I C L E Open Access A descriptive analysis of relations between parents’ self-reported smoking behavior and infants’ daily exposure to environmental tobacco smoke Doris Kehl1*, Jochen R Thyrian2, Jan Lüdemann3, Matthias Nauck3, Ulrich John4 Abstract Background: The aims of the present study were to examine relations between parents’ self-reported smoking behavior and infants’ daily exposure to environmental tobacco smoke, as assessed by urinary cotinine-to-creatinine ratio (CCR), and to describe the CCR over seven days among infants at home. Methods: A convenience sample of 27 households was drawn. Each household had to have at least one daily tobacco smoker and one child up to three years of age. Over a seven-day period, urine samples were obtained from the child daily. To examine relations between parents’ self-reported smoking and infants’ daily CCR, generalized estimating equation (GEE) analysis was used. Results: The data revealed that infants from households with indoor smoking had higher CCRs than infants in households with outdoor smoking. CCRs were higher in girls than in boys. Older infants had lower CCRs than younger infants. Smoking outside the home versus inside the home, infant’s gender, and infants’ age accounted for 68% of the variance in CCR in a GEE data analysis model. No increase or decrease of CCR over time was found. Conclusion: The findings suggest that parents’ self-reported smoking indoors at home versus outdoors is predictive of CCR among infants three and younger. Higher CCR concentrations in girls’ urine need further examination. Furthermore, significant fluctuations in daily CCR were not apparent in infants over a seven-day time period. Background Exposure to environmental tobacco smoke (ETS) is an important health risk among infants [1]. Infants lack mobility and independence and are unable to complain about or avoid ETS [2]. In homes where tobacco smok- ing occurs, infants are exposed during their regular daily activities [3]. Many studies have shown strong and consistent associations between ETS, particularly from parental smoking, and numerous childhood diseases such as respiratory infection, asthma, middle ear infec- tions, and sudden infant death syndrome. * Correspondence: doris.kehl@uni-greifswald.de 1Ernst-Moritz-Arndt-University Greifswald, Institute of Psychology, Department Health and Prevention, Robert-Blum-Str. 13, D-17487 Greifswald, Germany Infant’s exposure to ETS at home may be expected to differ according to the amount of tobacco smoke and the distance of tobacco smoke in relation to the air that the child breathes. Research suggests less exposure to ETS in homes with a home smoking ban than in homes without such a ban [4,5]. However, children are exposed to ETS across different environments [6,7]. Parents may not be aware of ETS exposure that occurs outside the home [8]. Cotinine has been suggested as the biomarker of choice for measuring exposure to ETS [9]. Cotinine may be taken from different tissues or fluids in the body [10]. Among infants at age three or younger, urine sam- ples seem to be particularly feasible since blood samples are more invasive and hair samples may not be available or may not be tolerated by children or parents. Cotinine © 2010 Kehl et al; licensee BioMed Central Ltd. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.