Cyanide and thiocyanate levels in blood and urine of workers with low-grade exposure to cyanide.

The concentrations of free cyanide in the blood and in the urine, and the levels of 'free' thiocyanate (oxidized to cyanide and distilled) as well as 'total' thiocyanate (directly determined and quite unspecific) were determined in the urine of 140 volunteers. There were four main categories of volunteers: (i) non-smokers, not exposed to cyanide in the atmosphere, (ii) smokers, not exposed to cyanide, (iii) non-smokers, exposed to various levels of cyanide in their occupation, and (iv) smokers who were also exposed to cyanide. The cyanide concentration in the blood did not show a clear relationship to either smoking or moderate occupational exposure; the levels were found to lie between 2.0 and 15.0 Μg of free cyanide per 100 ml of blood, with an average of 5.4 Μg for all categories of volunteers. It was found that the individual concentrations of free CN′ and CNS′ in the urine varied considerably and could not be used for detecting undue chronic exposure to cyanide at the concentrations encountered in the atmosphere. The average values, on the other hand, varied in a regular pattern for each of the four categories listed above. The influence of smoking had a far greater effect on the values obtained than the influence of atmospheric cyanide. Because of the great variations caused by other factors, concentrations of CN′ and CNS′ in the urine are not appropriate tools for individual routine control of minor occupational exposure to cyanides. However, non-smokers exposed to moderate cyanide levels in the air, and any individual exposed to high cyanide levels show higher than average values of CN′ and CNS′ in their urine. The cyanide values reported in this paper may be useful for the evaluation of analytical results from individual cases where poisoning from cyanide in the atmosphere is suspected. [ABSTRACT FROM AUTHOR]