Blood carbon monoxide and hydrogen cyanide concentrations in the fatalities of fire and non-fire associated civil aviation accidents, 1991-1998.

Civil Aerospace Medical Institute2000PDFTech ReportChaturvedi, Arvind K.Smith, DudleyCanfield, Dennis V.Civil Aeromedical InstituteUnited States. Office of Aviation MedicineCivil Aeromedical InstituteUnited StatesAir transportation crashesCivil aviationCrash analysisCarbon monoxideFatalitiesBlood analysisToxicologyHydridesFireForensic sciencestoxicologycarbon monoxidehydrogen cyanidesmoke toxicityfire/non-fire civil aviation accidentsaircraft accident investigationDOT/FAA/AM-00/9Postmortem blood samples submitted to the Federal Aviation Administration's Civil Aeromedical Institute (CAMI) from fatal civil aviation accident victims are analyzed for the primary toxic combustion gases carbon monoxide (CO), as carboxyhemoglobin (COHb), and hydrogen cyanide, as cyanide (CN- ). These analyses are performed to establish possible exposure of victims to smoke produced during in-flight/post-crash fires or to CO leaked into cabin/cockpit from faulty exhaust/heating systems. The presence of both gases in blood would suggest that the victim was alive and inhaled smoke from a fire. If only COHb is elevated, then the accident (or death) could be the result of CO contamination of the interior. Information pertaining to blood levels of the 2 gases in aviation fatalities, in relation to the associated accidents, is scattered or not available, particularly with regard to toxicity. Therefore, considering that COHb 65 10% and CN- 65 0.25 \ub5g/mL are sufficient to produce some degree of undesired physiological effects, the necessary information was extracted from the CAMI's toxicology database. Biological samples from 3857 fatalities of 2837 civil aviation accidents, occurring during 1991- 1998, were received at CAMI. Out of these, 1012 accidents, encompassing 1571 (41%) fatalities, were fire associated, whereas 1820 accidents were non-fire related. The remaining 5 accidents were of unkown fire status. There were fewer firerelated fatalities and associated accidents in the category wherein COHb 65 10% and CN- 65 0.25 \ub5g/mL than that in the category wherein COHb < 10% and CN- < 0.25 \ub5g/mL. No in-flight fire was documented in the former category, but inflight fires were reported in 14 accidents (18 fatalities) in the latter category. No fatality under non-fire accidents was found in which the levels of both gases were determined to be at or above the stated levels. There were 15 non-fire accidents with 17 fatalities in which only COHb (10-69%) was elevated, indicating that these accidents were associated with the inhalation of CO of non-fire origin. The present study suggests that the aviation fire accidents/fatalities were fewer than the aviation non-fire accidents/fatalities, with the fact that the fire-associated fatalities had COHb and CN- at levels high enough to produce some degree of impairment/toxicity. Furthermore, the study confirms that aviation accidents related to in-flight fires and to CO-contaminated interiors are rare.119