http://en.wikipedia.org/wiki/Chadron,_Nebraska

"The concentrations of Ag, Al, Cd, Cu, Mn, Pb and Zn in samples of rain and snow averaged 8.4 × 10−11, 3.5 × 10−7, 3.1 × 10−10, 4.4 × 10−9, 5.2 × 10−9, 4.8 × 10−9 and 1.0 × 10−8 g cm−3, respectively. "
A.W. Struempler
Trace metals in rain and snow during 1973 at Chadron, Nebraska
in:
Atmospheric Environment (1967)
Volume 10, Issue 1, 1976, Pages 33–37

Silver = 8.4 × 10−11 g cm−3
Aluminum = 3.5 × 10−7 g cm−3
Cadmium = 3.1 × 10−10 g cm−3
Copper = 4.4 × 10−9 g cm−3
Magnesium = 5.2 × 10−9 g cm−3
Lead = 4.8 × 10−9 g cm−3
Zinc = 1.0 × 10−8 g cm−3
http://www.sciencedirect.com/science/article/pii/0004698176902560

In comparison with stated normal amounts of aluminum found in the air.

(Quote) “…..Levels of aluminum in the air generally range from 0.005 to 0.18 micrograms (1 microgram, ?g, equals a millionth of a gram, 1 gram equals 0.0022 pound) of aluminum per cubic meter of air (0.005–0.18 ?g/m3 or 0.00018 mg/L) , depending on location, weather conditions, and level of industrial activity in the area. Most of the aluminum in the air is in the form of small suspended particles of soil (dust). Aluminum levels in urban and industrial areas may be higher and can range from 0.4 to 8.0 ?g/m3 ….”
http://www.eoearth.org/view/article/155461/

or (0.008 mg/l) [ 740.00 mg/L Alu content recorded in Rain water analysis from London- in studies from Wrights Patterson Airforce Laboratory just 5.0 mg/l caused harm to cellular function in the lungs]
http://www.dtic.mil/get-tr-doc/pdf?AD=ADA445568
https://mrmaxbliss.wordpress.com/2013/08...hemtrail-files/

http://www.worldcat.org/oclc/144877