Background. During studies on the health of children aged 3 or 4.5 years in Teplice and Prachatice districts of the Czech Republic, we focused also on the extent of smoking in the families and exposure of children to environmental tobacco smoke. Methods and Results. In 1128 questionnaires administered to mothers of children born in 1994–1998, 35.6 % of mothers indicated that they smoked and 48.9% of fathers/partners (N=1075) were smokers. Including other family members, there were 41.6 % families without any smoker, 30.1 % of families with one smoker and 24% families with two smokers (out of 1061 households). Urine samples of 523 pairs of mothers and children (aged 4.5 years) were assayed for cotinine using a RIA radioimmunoassay. Concentration of cotinine was higher than 500 ng cotinine/mg creatinine (the cut-off value for smoking) in 199 of 523 mothers (38 %). Exposure of children to environmental tobacco smoke (cotinine levels over 20ng/mg creatinine) was detected in 48.2 % of 523 children. There were more children with cotinine levels over 20 ng in Teplice (59.2 % of 287 children) than in Prachatice district (34.7 % of 236 children). Conclusions. Cotinine levels in child’s urine were significantly positively associated with maternal cotinine levels as well as with smoking of mother and father, and were lower in children visiting kindergarten.

        Key words: cotinine, nicotine, smoking, tobacco smoke pollution.