An estimate of the risk from a firework containing mercury. (II) Thiocyanate.

Abstract

An indoor firework, so called "Cagar Ningyo", has been imported from Mexico. It has white stick-type accessaries consisting of mercury (II) thiocyanate (Hg(SCN)2). When we set fire to the accessary, it decomposes extending brown-colored residuum like feces. By the thermal decomposition of Hg(SCN2), some harmful gases such as mercury vapor (Hg gas), sulfur dioxide (SO2 gas) and cyanate gas (CN gas) might be evolved. To estimate the risk from this firework, Hg gas, SO2 gas and CN gas evolved from the accessary were determined by the modified "Standard Method of Analysis for Hygienic Chemists Authorized by the Pharmaceutical Society of Japan". As the results, maximum 157.0μg of Hg gas could be detected in the decomposition gas from 10 mg of the accessary. Therefore, if this firework might be used to play in a room of 22.4 m3 (6 Jyou), Hg concentration in the room air could reach at the level of 0.070 mg/m3, which might exceed the allowable level in the work place (0.05 mg/m3). Maximum values of SO2 gas and CN gas detected were 2.26μg and 75μg, respectively, and predictive levels in the room might be much less than their allowable levels. We considered it undesirable to use this type of firework by the following reasons ; i) from the above estimate, we might be exposed to the high level of Hg vapor, ii) this firework itself or its residuum containing large amount of Hg might be discarded carelessly into the environment, and iii) it is dangerous to put such poisonous substances as Hg compounds near infants.