Measures of PSE The primary dependent variable in this study was the child’s exposure to PSE from all persons who smoked in the child’s environment. Parents provided information about their child’s PSE in response to a 15-item PSE Questionnaire that included questions these about the number of smokers in the home, parent/family smoking patterns and exposure, as well as home smoking rules. Specifically, parents were asked, ��How many cigarettes did you smoke in your home and to how many was your child exposed?�� They were also asked this question for each smoker living in or visiting the home and were similarly asked to report smoking and exposure occurring in the car. Exposure was defined as the number of cigarettes smoked in the same room or car as the child.

Parents were required to record a specific number of cigarettes smoked and exposed along a continuum ranging from yesterday through 7 days ago. However, the number of cigarettes smoked and the number of cigarettes to which the child was exposed over the previous 72 hr (3 days) was of primary interest for this study, as this timeframe was used to validate against measures of cotinine whose half-life falls within this window (Collier, Goldstein, Shrewsbury, Zhang, & Williams, 1990). Smoking parents participating in the study were asked to report on the number of cigarettes smoked and exposed from himself/herself and all other smokers living in the home and from those who visited. Nonsmoking parents were asked to report on the number of cigarettes smoked and the number of cigarettes to which the child was exposed from the smoking spouse/partner and all other smokers living in the home or visiting.

Responses were used to calculate the parents�� and all sources�� average daily smoking and the child’s average daily exposure to the cigarettes smoked in the home or car. Urine collection For toilet-trained children, urine samples were obtained in the clinic using standard urine collection methods. Children urinated into standard urine collection cups, and urine was transferred to plastic test tubes for freezing and analyses. For non�Ctoilet-trained children (n=15), samples were collected using a sterile pediatric urine collection bag (Pediabag; n=14) or via cotton rolls placed in the diaper (n=1). Obtained urine was expressed into a collection cup.

Obtained samples were split and frozen in a standard freezer with tubes labeled with a randomly assigned identification number for laboratory use. Twenty-one (16.9%) subjects were unable to provide sufficient urine to split (<10 ml of urine in a single void). Batched samples were packed in dry ice and shipped to the Mass Spectrometry laboratories at San Diego State University, San Diego, Batimastat CA, for analyses of cotinine levels. All samples were assayed by a high-performance liquid chromatography and tandem mass spectrometry method (Bernert et al., 1997). Statistical analyses Cotinine values below detection were set to 0.