Validity of salivary thiocyanate as an indicator of cyanide exposure from smoking.

The purpose of this study was to evaluate the validity of salivary thiocyanate as an indicator of cyanide exposure from smoking. The salivary thiocyanate level showed wide variation, and the largest source of thiocyanate was hydrogen cyanide from cigarette smoke. Hydrogen cyanide in the mainstream of cigarette smoke was as high as 40-70 ppm, which is beyond the threshold limit value for occupational health (10 ppm). The hydrogen cyanide level in the sidestream smoke was lower less than 5 ppm. Thus the amount of cyanide intake was larger in active smokers than in passive ones. The correlation between the thiocyanate level in saliva and plasma was statistically significant. Thiocyanate levels in both plasma and saliva increased with the amount of cigarette smoke, and the discriminant powers (smoker versus non smoker) of thiocyanate levels in both plasma and saliva were quite similar. The smoker/non smoker ratio for salivary thiocyanate was 3.04 and that of plasma thiocyanate was 1.73. The result indicated that smoking status could be reflected more by the thiocyanate level in saliva than in plasma. The biological half life of salivary thiocyanate was estimated to be as long as 9.5 days from the changes salivary thiocyanate after stopping smoking. From the results of this study, it was concluded that salivary thiocyanate was a suitable indicator of habitual smoking exposure.