WWI Poison Gas Found in Atmosphere
The infamous poisonous gas phosgene, renown during WWI as a choking agent, has been detected in what is being called 'significant' quantities in the atmosphere. According to the CDC, "At low concentrations, it has a pleasant odor of newly mown hay or green corn..."
The very first global study of the distribution of phosgene was recently published in Geophysical Research Letters, "Global phosgene observations from the Atmospheric Chemistry Experiment (ACE) mission" (Fu et al., 2007; 43, doi:10.1029/2007GL029942).
Phosgene, aka 'CG' by military personal, is a chloroflourocarbon (like CFCs) used in the production of various plastics and foams, pesticides, pharmaceuticals, although its use is apparently being reduced [source].
A large fraction of phosgene is formed through the decay of other CFCs. Ultraviolet light is full of energy, and can break and form chemical bonds (hence, skin cancer). Therefore, through a variety of chemical what-whose-ery, phosgene is also formed from our old refrigerant friends.
Phosgene is then expected to be present in the stratosphere (where the ozone layer hangs out), between 12-25km above the Earth's surface. To put this in perspective, commercial flights cruise between 9-10km (32,000 feet).
And that's where it was. The scientists discovered that, the bulk of atmospheric phosgene is found ~25km above the equator, with decreasing amounts near the the poles. Countries near equator aren't necessarily producing more phosgene/CFC's, but rather due to the mixing of the atmosphere in its upper echelons, 'CG' is being sequestered there.
They then compared their results with data collected in the 1980's and 90's - 'CG' has decreased nearly 25% in the stratosphere, which they attribute to legal regulations on the use of its precursors (CFCs) during the late 1980's (i.e. The Montreal Protocol).
"It's very toxic and pretty nasty stuff - its reputation is well deserved. Considering the health hazards associated with phosgene, the chemical industry is trying to find substitutes to eliminate its use. But the use of chlorinated hydrocarbons is being reduced because of the legal restrictions of the Montreal Protocol, so phosgene is also decreasing."