(source: http://www.publicdomainfiles.com/show_file.php?id=13500120613252 (licensed for public domain))

Jet engines are a very complex propulsion system that contains gears and fans made up of several types of material that are intended to handle extreme temperatures (from cold to hot) while providing the necessary movement (at rapid speeds close to the sound of noise) to create movement of an airplane, helicopter, or rocket engine.

In many cases, jet fuel contains additives to prevent corrosion, sometimes has a deicer additive as well.

Jet fuel is kerosene-based that can contains several volatile organic compounds (alkanes, cycloalkanes, alkenes) in addition to aromatic hydrocarbons (pentane, butane, benzene, toluene, ehtylbenzenes, 1,3 butadiene, and xylenes).

(source: Jet Fuel Toxicology; Neurotoxicity from Exposure to Jet Fuel Exhaust (pg.61))

Some of these compounds are the same ones that have resulted in exposure concerns in the printing industry when used in solvents.

There can be variations in fuel between military and commercial aircraft application that can change the levels for the compounds used.

(source: https://commons.wikimedia.org/wiki/File:JetEngineGraph2.PNG (creative commons license))

Applications for aircraft (either civilian or military) requires a transportation mode that is capable of fast speeds, equipment that can change from hot to cold quickly (without damage) and intense heat utilizing elements that doesn’t deteriorate when temperatures reach 1000 degrees Kelvin.

To handle these conditions, three different materials, used in the construction of these engines, contain cesium, thorium, and uranium are elements that are within our own earth crust and mantle that produce radiation.

Iron, cobolt, and nickel are used as well in the construction of the engines.

Jet exhaust emissions can produce a black soot (in colder temperatures) this is visible on buildings and other objects. These emmisions can contain particulates from these engine components.

When fog conditions happen at Sea-Tac Airport, the jet fuel odor can be present on the North, West, and South sides of the airport.