Relationship of serum thiocyanate concentrations to smoking characteristics

Thiocyanate (SCN) concentrations were determined in serum samples from 130 young healthy persons (60 smokers) and related to their smoking and physiologic characteristics. Serum thiocyanate correlated strongly and approximately equally with the number of cigarettes/d X kg of ideal body weight (IBW) (r = 0.748), total nicotine intake in mg/d X kg IBW (r = 0.735), and total tar intake in mg/d X kg IBW (r = 0.731). Multiple linear regression analysis that included these factors as well as sex, marijuana use, menthol, and degree of inhalation only increased the multiple r to 0.803. A more sensitive statistical method (NYBAID) was also used to determine the most significant influences of these variables on serum SCN. The association with depth of inhalation (i.e., smoking versus nonsmoking) was dominant among the relationships considered. The highest SCN levels were exhibited in heavy nicotine users (8.58 +/- 3.00 mg/l), while average users had slightly lower concentrations (6.49 +/- 2.37 mg/l) (p less than 0.03). In nontobacco smokers, those who smoked marijuana several times weekly had higher SCN levels (4.66 +/- 2.16 mg/l) than noncannabis users (2.38 +/- 1.38 mg/l) (p less than 0.03). These studies confirm the utility of serum SCN as an index of smoking rate and demonstrate the role of secondary variables in accounting for the chemical in serum.