Universidad De Moron, Laboratorio Quimico Forense, Sc Of Justice, La Plata
* Toxicology and Legal Chem., University Of La Plata
** Emeritus Prof., University Of Buenos Aires, 41(E) 119 Y 120 (1900), La Plata, Argentina

Methods:
To determine the amount of hydrogen cyanide, two techniques were carried out simultane-ously: a) Gettler and Goldbaum technique which is based on Prussian blue reaction LOD: 0.1 µg) and b) microdiffusion as described by Feldstein and Klendshoj (LOD: 0.2 µg).

Carbon monoxide results were expressed as the percentage of carboxihemoglobin over total hemoglobin, showing values between 4 and 18% with an average of 9% for n = 35. Hydrogen cyanide showed values between 2.0 and 7.2 mg per liter of blood with and average of 3.5 mg/l for n = 35. Other components with toxicogenic relevance such as ethanol, methanol, aldehydes and other volatile compounds gave negative results for the 35 cases. Consumer drugs and psychotropics were negative, as well.

Discussion:
The high level of hydrogen cyanide and the low level of carbon monoxide in the 35 cases was remarkable. The high level of HCN in blood can be attributed to the marked polyurethane decom-position produced between 150° and 300°C and the massive amount of hydrogen cyanide evolved above 500°C. On the other hand, the low level of CO in blood could be due to the rapid temperature increase (500° to 1000°C in 2 to 5 min) of the gases evolved, compared that produced with a fire of an equivalent amount of wood. Other cases of intentional fire of polyurethane mattresses attributed the deaths to carbon monoxide intoxication, with no mention of hydrogen cyanide determination. Authors reporting death cases due to plastic combustion, attributed the main death factor to CO and detected only few cases with sublethal doses of HCN.

Conclusions:
In our opinion polymer type and the presence of delaying combustion agents are the main cause of the differences obtained when comparing cases. In this case, the quantitative determination showed that the main toxic action in the fire deaths was hydrogen cyanide and secondary carbon monoxide.