><i>silver iodide and dry ice are the most commonly used substances in cloud seeding technology</i> (down-cased for your reading pleasure)<p>uh, how <i>much</i> silver iodide? All of it eventually goes down a drain, and back into the water supply.<p><a href="http://en.wikipedia.org/wiki/Argyria" rel="nofollow">http://en.wikipedia.org/wiki/Argyria</a>