Kehl et al. BMC Public Health 2010, 10:424 http://www.biomedcentral.com/1471-2458/10/424 Table 1 Demographic and smoking characteristics of the adult respondents (N = 47) Demographic characteristics Age Mean 27.47 SD 5.32 Female gender Partner present Native language German School education Low (≤ 9 years) Middle (10 - 11 years) High (≥ 12 years) Employment Employed Unemployed Parenting time Other Household income per month a < 1300 € 1300 - 2300 € > 2300 € Smoking characteristics Smoking status of respondent b Daily smoker Less than daily smoker Former smoker Never smoker Cigarettes per day (no.), daily smokers (n = 39) Mean 16.23 SD 7.25 N (%) 27 (57.45) 42 (89.4) 39 (83.0) 16 (34.1) 19 (40.4) 12 (25.5) 16 (34.0) 9 (19.1) 16 (34.0) 6 (12.8) 14 (53.9) 8 (30.8) 4 (15.4) 39 (83.0) 3 (6.4) 2 (4.3) 3 (6.4) a one household income is missing b daily smoker: smoked more than 100 cigarettes in lifetime and currently smoking at least one cigarette daily over the last four weeks; less than daily smoker: smoked more than 100 cigarettes and less than daily during the last 30 days; former smoker: smoked more than 100 cigarettes in lifetime and did not smoke during the last 30 days prior to the interview; never smoker: did not smoke, or smoked less than 100 cigarettes in their life. Consequently, self-reported smoking status was related with cotinine values. Among all households, 14 included two smokers and 13 included one smoker, and in 14 households there was smoking inside the home. Among the 14 house- holds with indoor smoking, in 10 tobacco smoking took place in one room only. This room was the kitchen in eight households, the living room in one household, and the working room in one household. In four households, there was general tobacco smoking in two rooms (the kitchen and one of the other rooms such as the bath- room, housekeeping room or living room). No smoking in the bedroom or the children’s room was reported. For the seven days prior to the interview, there was smoking in the living room in 6 of the 14 indoor Page 4 of 8 smoking households. In these 6 households, it was one household member (with or without visitors) who smoked. The median of the cotinine concentrations across all infants was 28.2, concentrations ranged from less than 10.0 to 179.0 ng/ml. Six infants had a median less than 10.0 ng/ml, 2 had a median between 10.0 and 14 ng/ml, 9 a median between 15.0 and 40 ng/ml, and 10 a med- ian above 40 ng/ml. The mean cotinine concentration across all infants was 52.7 (SD = 47.7), and it ranged from less than 10.0 to 171.4 ng/ml. Three infants had mean cotinine values less than 10 ng/ml, five had a low mean (10-14 ng/ml), seven had a moderate mean (15-40 ng/ml), and 12 had a high mean exposure to ETS (more than 40 ng/ml). For one infant, none of the seven urine samples could be analyzed due to insufficient urine. Among the 14 infants who had reports of smoking inside the home, all had mean cotinine concentrations greater than or equal to 10 ng/ml. Among the 13 infants who had no reports of parent’s smoking inside the home, nine infants had mean cotinine concentrations greater than 10 ng/ml and three infants had mean coti- nine concentrations less than 10 ng/ml. From Monday to Sunday, the mean cotinine concentrations across all infants ranged from 31.8 (SD = 31.4; Thursday) to 61.5 (SD = 77.0; Wednesday). The mean CCR across all infants was 43.2 (SD = 96.3), and ranged from 0.43 to 512.7 μg/mmol. From Monday to Sunday, the mean CCR across all infants ranged from 24.7 (SD = 33.0; Monday) to 63.9 μg/mmol (SD = 111.7; Sunday). Infants’ cotinine creatinine ratios (microgram/mmol) in urine during the period of 7 days are presented in Table 2. Relations of the infant’s daily CCR with ETS exposure variables are presented in Table 3. An exchangeable working correlation structure was used regarding the calculated correlation matrix. Smoking outside the home, compared to inside the home, was the only expo- sure variable that was significantly related to CCR. Infants in households with indoor smoking had signifi- cantly higher CCRs than infants in households with reports of smoking on the balcony or outside the home. The explained variance of this model was 22%. For infants with one smoker in the home, compared to infants with two smokers in the home, the differences between the CCRs were not significant. Cpd smoked in the presence of the infant and time infants spend in rooms in which smoking occurs were not significantly related with the CCR. Smoking inside versus outside home was again entered into a GEE model, and this variable included adjustments for infant’s age (in months), gender and study day (Table 4). Smoking inside compared to out- side home, as well as gender and age, were significantly related to the CCR. The CCRs were higher in girls than