Occupational exposures to cyanide in Baltimore fire fighters.

A group of 479 fire fighters were investigated for routine exposure to hydrogen cyanide in the fire atmosphere using measurements of serum thiocyanate (SCN-). Our findings indicate that fire fighters were exposed to levels of hydrogen cyanide sufficient to raise their mean serum thiocyanate (SCN-) levels above that of controls. This elevation of serum SCN- occurred independently of smoking habits. Exposure to cyanide occurred much less frequently than previously studied exposures to carbon monoxide. Difficulties of correlating acute symptoms and the effectiveness of mask use with serum thiocyanate are discussed.