“…Due to technically difficult analyses and other sources than ETS of other biomarker compounds, the preferred choice to this date has been the analysis of cotinine [Benowitz, 1999;Jaakkola and Samet, 1999a]. Promising methods utilizing hair cotinine and nicotine levels have been developed and this tracks exposure that has occurred months before sampling [Dimich-Ward et al, 1997;Klein and Koren, 1999] Exposure to ETS has been assessed by analyzing cotinine in body fluids (urine, saliva, and serum) by several groups [Coultas et al, 1990;Bergman et al, 1996;Jenkins et al, 1996;Phillips et al, 1996;Pirkle et al, 1996;Bernert et al, 1997;Phillips et al, 1998a,b,c;Trout et al, 1998;Jenkins and Counts, 1999b;Lindgren et al, 1999;Phillips et al, 1999;Maskarinec et al, 2000]. However, only few have determined 3 0 -hydroxycotinine Tuomi et al, 1999;Tyrpien et al, 2000], even though it is the main nicotine metabolite in both active and passive smokers and corresponds to $40% of the total nicotine excretion [Neurath et al, 1987;Jacob et al, 1992;Jacob et al, 1993].…”