Magnesium and Thermite Poisoning
- Author: Jayson Tappan, MD; Chief Editor: Zygmunt F Dembek, PhD, MPH, MS, LHD more...
Two major types of metal incendiaries exist: those that are magnesium based and those of the thermite/thermate type. Incendiary metals are usually encountered in the military or industrial setting but can also be encountered in other applications due to common usage of magnesium shavings as a fire-starting technique such as for camping or in sparklers and fireworks.
Magnesium, a silvery white metal of atomic weight 24.32, ignites at 632°C and burns at 1982°C, with magnesium oxide (MgO) as its combustion product. In an exothermic reaction, metallic magnesium can ignite to produce magnesium dihydroxide (ie, Mg(OH)2 and hydrogen. When combined with water while burning it releases hydrogen gas and oxygen. Magnesium is used in either powdered or solid form as an incendiary agent for both illumination and antipersonnel purposes. Various alloys of magnesium (eg, aluminum/zinc/magnesium alloy found in US M126 round) are mechanically sturdier but also can be ignited easily. Militaries use magnesium in hand-held signal flares and in glowing “tracer rounds,” which are ammunition fired in series with traditional ammunition in automatic weapons to assist with aim (eg, US M856, M10, M17).
Thermite is a mixture of powdered or granular aluminum and powdered iron oxide. When combined with other substances, such as binders, the material is termed a thermate. All such materials react vigorously when heated to the combustion temperature of aluminum. This reaction produces aluminum oxide, elemental iron, and sufficient heat to melt the iron. The reaction temperature is at least 2200°C. Due to its high temperature and creation of iron, the thermite is used industrially for welding such as welding together railroad track and other in place structural repairs. Thermite is also used to purify other metals through its high temperature.
The military uses thermite in grenades (US AN-M14) for the destruction of vehicles and equipment where their high heat renders vehicles and equipment inoperable. Possible thermite burns could be seen from a railroad employee opening the thermite crucible before the reaction had completed and being exposed to the still burning material or a military individual being exposed to the burning particles from the use or demonstration of one of these grenades.
Because the burning temperature of these chemicals is so high, standard hazardous-materials clothing (even level A self-contained and chemical-proof clothing) is not protective.
Burning thermite or magnesium produces predominantly thermal injury that may be considered identical to deep partial- or full-thickness thermal burns (see Emergent Management of Thermal Burns). Thermite incendiaries may produce multiple small deep burns that contain scattered molten iron. These particles should be cooled immediately with water and removed. This may be possible with local anesthesia. Residual particles (especially of magnesium) may also produce chemical injury to the eyes, skin, and respiratory tract.
If exposure to incendiary metals takes place in a small, confined space such as in a military vehicle attacked by a thermite grenade, inhalation of hot gases can produce direct thermal injury to respiratory tissues. The magnesium particles can react with tissue fluid to create magnesium hydroxide, which is a strong base. This strong base can lead to alkali burns from the noncombusted magnesium particles. In a separate reaction, while the magnesium is burning, it can react with water to create hydrogen gas (H2), which is highly flammable. This is why water is not a recommended dousing agent for these magnesium burns.
No exhaustive study or series of incendiary injury exists. In a study of one burn center during a 51-year period, only one burn was attributed to magnesium and no burns were reported due to thermite. This seemingly low incidence likely stems from the fact that all thermal burns are managed similarly regardless of cause and often unique historical elements go unnoticed or unrecorded.
Outcomes of incendiary metal burns are similar to other thermal injuries (see Emergent Management of Thermal Burns).
Race-, Sex-, and Age-related Demographics
Incendiary burns show no predilection for race. Because incendiary metals are more commonly encountered in industrial and military settings, exposures are more common in males than in females. Because incendiary metals are more commonly encountered in industrial and military settings, exposures are more common in younger adults.
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