[Markers for smoking].

Quantitative and objective measurement of exposure to cigarette smoke by assays of chemical markers is desirable, especially in preventive medicine, since the negative health effects of tobacco smoke are well documented. Chemical markers include nicotine and cotinine in plasma, urine, and saliva; carbon monoxide in exhaled air; carboxyhemoglobin in blood and thiocyanate in biological fluids. Ease of use, cost, specificity, and sensitivity vary across markers. Determination of the thiocyanate/creatinine ratio in urine is a reliable, noninvasive, and inexpensive test for evaluating exposure to cigarette smoke. No marker for cumulative exposure to cigarette smoke is available to date. The plasma level of fluorescent lipoperoxides may provide an estimation of the in vivo toxicity of exposure to cigarette smoke.