“…The cotinine levels in children, measured in saliva or urine, increase with the number of smoking parents (Cook et al, 1994;Irvine et al, 1997;Seifert et al, 2002), the number of smokers in the household (Jordaan et al 1999), the number of cigarettes/day that the parents smoke at home (Bakoula et al, 1997;Irvine et al, 1997;Oddoze et al, 1999) and the number of cigarettes/day that household members (parents and others) smoke at home (Preston et al, 1997;Winkelstein et al, 1997;Manino et al, 2001;Callais et al, 2003). Moreover, the cotinine is substantially reduced when parents do not smoke in the presence of their children (Bakoula et al, 1997;Irvine et al, 1997;Seifert et al, 2002), and increases progressively with the frequency of smoking in their presence (Irvine et al, 1997).…”