[Salivary, urinary and plasma thiocyanate in smokers and non-smokers]. 
Thiocyanate is a major metabolic product of hydrocyanic acid.  Its concentration in the serum, urine and saliva of individuals with little exposure to hydrocyanic acid (i.e. non smokers) is very low.  But about three fold higher concentrations of thiocyanate are found in the sera, urine and saliva of smokers as compared to non smokers, because of cyanide provided by cigarette smoke.  The concentrations of thiocyanate in the three biological fluids studied were different and it appeared to be no correlation in the distribution of thiocyanate concentrations in these fluids when individual subjects were compared.  Urinary and salivary concentration power showed decreased kidney excretion of thiocyanate in smokers.  The appearance or the disappearance of thiocyanates in the saliva and the urine takes place slowly.  The salivary or urinary levels of thiocyanates are therefore good indicators of chronic intoxication from tobacco because it is not very sensitive to daily variations in tobacco smoking; it reflects the slow transformation of cyanide as well as the final elimination of this ion from urine which is slowed down in smokers.