Fig. 2

Urine from 93 kindergarten children analyzed by ELISA and GC–MS. a Free and total cotinine levels determined by GC–MS and IR-cotinine levels in the urine of kindergarten children according to smoking status of parents: a parents are non-smokers (n = 36), b father smokes (n = 44), c mother smokes (n = 3), d both parents smoke (n = 10). *P < 0.05, **P < 0.01 by Scheffe’s test after ANOVA using logarithmic analysis, ^†† P < 0.01 by the Kruskal–Wallis test. Spearman’s rank correlation coefficients are 0.28 (P < 0.01), 0.37 (P < 0.01), and 0.49 (P < 0.01) for free cotinine, total cotinine, and IR-cotinine, respectively. b Free and total cotinine levels determined by GC–MS and IR-cotinine levels in urine of kindergarten children according to smoking habits of the parents in the presence of their children: a parents are non-smokers (n = 36), b parents do not smoke in the presence of their children (n = 37), c father or mother smokes in the presence of their children (n = 17), d both parents smoke in the presence of their children (n = 3). ^†† P < 0.01, Kruskal–Wallis test. Spearman’s rank correlation coefficients are 0.14 (P = 0.17), 0.16 (P = 0.13) and 0.34 (P < 0.01) for free cotinine, total cotinine, and IR-cotinine, respectively