Potential health hazards from burning aircraft composites

Burning of polymer matrix composites in postcrash aircraft fires generates a complex mixture of combustion products comprised of gases, organic vapors, and particulate matter including airborne carbon fibers. There is concern among the fire fighting, investigative, and mishap response communities that an unusual health hazard is posed by this combination of combustion products. This paper presents an overview of the nature and potential hazards of acute exposure to airborne carbon fibers from fire and explosion involving advanced composites materials. Data from fire tests and crash-site investigations suggest that a small fraction of the fibers released in fires are respirable and can be inhaled deep into the lung. Most of the carbon fibers produced in fires are 2-10 times larger than the critical fiber size associated with asbestos toxicity, and their concentration is well below OSHA recommended levels for chronic exposure. At issue however are the toxicological effects of adsorbed combustion products. Chemical extraction shows that a large number of toxic organic compounds are adsorbed on these fibers, several of which are known carcinogens and mutagens in animals. At the present time there is no conclusive evidence linking airborne fibers from burning composites to any unusual health hazard. However, no toxicological studies have been conducted to assess the long-term health effects from exposure to a single high dose of fibrous particulates and any synergistic interactions with the organic chemicals.